1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2019 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2019 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2019 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
544 Initial support for the FreeBSD/mips target and native configuration
545 was developed by SRI International and the University of Cambridge
546 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
547 ("CTSRD"), as part of the DARPA CRASH research programme.
549 Initial support for the FreeBSD/riscv target and native configuration
550 was developed by SRI International and the University of Cambridge
551 Computer Laboratory (Department of Computer Science and Technology)
552 under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the DARPA
553 SSITH research programme.
555 The original port to the OpenRISC 1000 is believed to be due to
556 Alessandro Forin and Per Bothner. More recent ports have been the work
557 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
561 @chapter A Sample @value{GDBN} Session
563 You can use this manual at your leisure to read all about @value{GDBN}.
564 However, a handful of commands are enough to get started using the
565 debugger. This chapter illustrates those commands.
568 In this sample session, we emphasize user input like this: @b{input},
569 to make it easier to pick out from the surrounding output.
572 @c FIXME: this example may not be appropriate for some configs, where
573 @c FIXME...primary interest is in remote use.
575 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
576 processor) exhibits the following bug: sometimes, when we change its
577 quote strings from the default, the commands used to capture one macro
578 definition within another stop working. In the following short @code{m4}
579 session, we define a macro @code{foo} which expands to @code{0000}; we
580 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
581 same thing. However, when we change the open quote string to
582 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
583 procedure fails to define a new synonym @code{baz}:
592 @b{define(bar,defn(`foo'))}
596 @b{changequote(<QUOTE>,<UNQUOTE>)}
598 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
601 m4: End of input: 0: fatal error: EOF in string
605 Let us use @value{GDBN} to try to see what is going on.
608 $ @b{@value{GDBP} m4}
609 @c FIXME: this falsifies the exact text played out, to permit smallbook
610 @c FIXME... format to come out better.
611 @value{GDBN} is free software and you are welcome to distribute copies
612 of it under certain conditions; type "show copying" to see
614 There is absolutely no warranty for @value{GDBN}; type "show warranty"
617 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
622 @value{GDBN} reads only enough symbol data to know where to find the
623 rest when needed; as a result, the first prompt comes up very quickly.
624 We now tell @value{GDBN} to use a narrower display width than usual, so
625 that examples fit in this manual.
628 (@value{GDBP}) @b{set width 70}
632 We need to see how the @code{m4} built-in @code{changequote} works.
633 Having looked at the source, we know the relevant subroutine is
634 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
635 @code{break} command.
638 (@value{GDBP}) @b{break m4_changequote}
639 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
643 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
644 control; as long as control does not reach the @code{m4_changequote}
645 subroutine, the program runs as usual:
648 (@value{GDBP}) @b{run}
649 Starting program: /work/Editorial/gdb/gnu/m4/m4
657 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
658 suspends execution of @code{m4}, displaying information about the
659 context where it stops.
662 @b{changequote(<QUOTE>,<UNQUOTE>)}
664 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
666 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
670 Now we use the command @code{n} (@code{next}) to advance execution to
671 the next line of the current function.
675 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
680 @code{set_quotes} looks like a promising subroutine. We can go into it
681 by using the command @code{s} (@code{step}) instead of @code{next}.
682 @code{step} goes to the next line to be executed in @emph{any}
683 subroutine, so it steps into @code{set_quotes}.
687 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
689 530 if (lquote != def_lquote)
693 The display that shows the subroutine where @code{m4} is now
694 suspended (and its arguments) is called a stack frame display. It
695 shows a summary of the stack. We can use the @code{backtrace}
696 command (which can also be spelled @code{bt}), to see where we are
697 in the stack as a whole: the @code{backtrace} command displays a
698 stack frame for each active subroutine.
701 (@value{GDBP}) @b{bt}
702 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
704 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
706 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
707 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
709 #4 0x79dc in expand_input () at macro.c:40
710 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
714 We step through a few more lines to see what happens. The first two
715 times, we can use @samp{s}; the next two times we use @code{n} to avoid
716 falling into the @code{xstrdup} subroutine.
720 0x3b5c 532 if (rquote != def_rquote)
722 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
723 def_lquote : xstrdup(lq);
725 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
728 538 len_lquote = strlen(rquote);
732 The last line displayed looks a little odd; we can examine the variables
733 @code{lquote} and @code{rquote} to see if they are in fact the new left
734 and right quotes we specified. We use the command @code{p}
735 (@code{print}) to see their values.
738 (@value{GDBP}) @b{p lquote}
739 $1 = 0x35d40 "<QUOTE>"
740 (@value{GDBP}) @b{p rquote}
741 $2 = 0x35d50 "<UNQUOTE>"
745 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
746 To look at some context, we can display ten lines of source
747 surrounding the current line with the @code{l} (@code{list}) command.
753 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
755 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
758 538 len_lquote = strlen(rquote);
759 539 len_rquote = strlen(lquote);
766 Let us step past the two lines that set @code{len_lquote} and
767 @code{len_rquote}, and then examine the values of those variables.
771 539 len_rquote = strlen(lquote);
774 (@value{GDBP}) @b{p len_lquote}
776 (@value{GDBP}) @b{p len_rquote}
781 That certainly looks wrong, assuming @code{len_lquote} and
782 @code{len_rquote} are meant to be the lengths of @code{lquote} and
783 @code{rquote} respectively. We can set them to better values using
784 the @code{p} command, since it can print the value of
785 any expression---and that expression can include subroutine calls and
789 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
791 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
796 Is that enough to fix the problem of using the new quotes with the
797 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
798 executing with the @code{c} (@code{continue}) command, and then try the
799 example that caused trouble initially:
805 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
812 Success! The new quotes now work just as well as the default ones. The
813 problem seems to have been just the two typos defining the wrong
814 lengths. We allow @code{m4} exit by giving it an EOF as input:
818 Program exited normally.
822 The message @samp{Program exited normally.} is from @value{GDBN}; it
823 indicates @code{m4} has finished executing. We can end our @value{GDBN}
824 session with the @value{GDBN} @code{quit} command.
827 (@value{GDBP}) @b{quit}
831 @chapter Getting In and Out of @value{GDBN}
833 This chapter discusses how to start @value{GDBN}, and how to get out of it.
837 type @samp{@value{GDBP}} to start @value{GDBN}.
839 type @kbd{quit} or @kbd{Ctrl-d} to exit.
843 * Invoking GDB:: How to start @value{GDBN}
844 * Quitting GDB:: How to quit @value{GDBN}
845 * Shell Commands:: How to use shell commands inside @value{GDBN}
846 * Logging Output:: How to log @value{GDBN}'s output to a file
850 @section Invoking @value{GDBN}
852 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
853 @value{GDBN} reads commands from the terminal until you tell it to exit.
855 You can also run @code{@value{GDBP}} with a variety of arguments and options,
856 to specify more of your debugging environment at the outset.
858 The command-line options described here are designed
859 to cover a variety of situations; in some environments, some of these
860 options may effectively be unavailable.
862 The most usual way to start @value{GDBN} is with one argument,
863 specifying an executable program:
866 @value{GDBP} @var{program}
870 You can also start with both an executable program and a core file
874 @value{GDBP} @var{program} @var{core}
877 You can, instead, specify a process ID as a second argument, if you want
878 to debug a running process:
881 @value{GDBP} @var{program} 1234
885 would attach @value{GDBN} to process @code{1234} (unless you also have a file
886 named @file{1234}; @value{GDBN} does check for a core file first).
888 Taking advantage of the second command-line argument requires a fairly
889 complete operating system; when you use @value{GDBN} as a remote
890 debugger attached to a bare board, there may not be any notion of
891 ``process'', and there is often no way to get a core dump. @value{GDBN}
892 will warn you if it is unable to attach or to read core dumps.
894 You can optionally have @code{@value{GDBP}} pass any arguments after the
895 executable file to the inferior using @code{--args}. This option stops
898 @value{GDBP} --args gcc -O2 -c foo.c
900 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
901 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
903 You can run @code{@value{GDBP}} without printing the front material, which describes
904 @value{GDBN}'s non-warranty, by specifying @code{--silent}
905 (or @code{-q}/@code{--quiet}):
908 @value{GDBP} --silent
912 You can further control how @value{GDBN} starts up by using command-line
913 options. @value{GDBN} itself can remind you of the options available.
923 to display all available options and briefly describe their use
924 (@samp{@value{GDBP} -h} is a shorter equivalent).
926 All options and command line arguments you give are processed
927 in sequential order. The order makes a difference when the
928 @samp{-x} option is used.
932 * File Options:: Choosing files
933 * Mode Options:: Choosing modes
934 * Startup:: What @value{GDBN} does during startup
938 @subsection Choosing Files
940 When @value{GDBN} starts, it reads any arguments other than options as
941 specifying an executable file and core file (or process ID). This is
942 the same as if the arguments were specified by the @samp{-se} and
943 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
944 first argument that does not have an associated option flag as
945 equivalent to the @samp{-se} option followed by that argument; and the
946 second argument that does not have an associated option flag, if any, as
947 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
948 If the second argument begins with a decimal digit, @value{GDBN} will
949 first attempt to attach to it as a process, and if that fails, attempt
950 to open it as a corefile. If you have a corefile whose name begins with
951 a digit, you can prevent @value{GDBN} from treating it as a pid by
952 prefixing it with @file{./}, e.g.@: @file{./12345}.
954 If @value{GDBN} has not been configured to included core file support,
955 such as for most embedded targets, then it will complain about a second
956 argument and ignore it.
958 Many options have both long and short forms; both are shown in the
959 following list. @value{GDBN} also recognizes the long forms if you truncate
960 them, so long as enough of the option is present to be unambiguous.
961 (If you prefer, you can flag option arguments with @samp{--} rather
962 than @samp{-}, though we illustrate the more usual convention.)
964 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
965 @c way, both those who look for -foo and --foo in the index, will find
969 @item -symbols @var{file}
971 @cindex @code{--symbols}
973 Read symbol table from file @var{file}.
975 @item -exec @var{file}
977 @cindex @code{--exec}
979 Use file @var{file} as the executable file to execute when appropriate,
980 and for examining pure data in conjunction with a core dump.
984 Read symbol table from file @var{file} and use it as the executable
987 @item -core @var{file}
989 @cindex @code{--core}
991 Use file @var{file} as a core dump to examine.
993 @item -pid @var{number}
994 @itemx -p @var{number}
997 Connect to process ID @var{number}, as with the @code{attach} command.
999 @item -command @var{file}
1000 @itemx -x @var{file}
1001 @cindex @code{--command}
1003 Execute commands from file @var{file}. The contents of this file is
1004 evaluated exactly as the @code{source} command would.
1005 @xref{Command Files,, Command files}.
1007 @item -eval-command @var{command}
1008 @itemx -ex @var{command}
1009 @cindex @code{--eval-command}
1011 Execute a single @value{GDBN} command.
1013 This option may be used multiple times to call multiple commands. It may
1014 also be interleaved with @samp{-command} as required.
1017 @value{GDBP} -ex 'target sim' -ex 'load' \
1018 -x setbreakpoints -ex 'run' a.out
1021 @item -init-command @var{file}
1022 @itemx -ix @var{file}
1023 @cindex @code{--init-command}
1025 Execute commands from file @var{file} before loading the inferior (but
1026 after loading gdbinit files).
1029 @item -init-eval-command @var{command}
1030 @itemx -iex @var{command}
1031 @cindex @code{--init-eval-command}
1033 Execute a single @value{GDBN} command before loading the inferior (but
1034 after loading gdbinit files).
1037 @item -directory @var{directory}
1038 @itemx -d @var{directory}
1039 @cindex @code{--directory}
1041 Add @var{directory} to the path to search for source and script files.
1045 @cindex @code{--readnow}
1047 Read each symbol file's entire symbol table immediately, rather than
1048 the default, which is to read it incrementally as it is needed.
1049 This makes startup slower, but makes future operations faster.
1052 @anchor{--readnever}
1053 @cindex @code{--readnever}, command-line option
1054 Do not read each symbol file's symbolic debug information. This makes
1055 startup faster but at the expense of not being able to perform
1056 symbolic debugging. DWARF unwind information is also not read,
1057 meaning backtraces may become incomplete or inaccurate. One use of
1058 this is when a user simply wants to do the following sequence: attach,
1059 dump core, detach. Loading the debugging information in this case is
1060 an unnecessary cause of delay.
1064 @subsection Choosing Modes
1066 You can run @value{GDBN} in various alternative modes---for example, in
1067 batch mode or quiet mode.
1075 Do not execute commands found in any initialization file.
1076 There are three init files, loaded in the following order:
1079 @item @file{system.gdbinit}
1080 This is the system-wide init file.
1081 Its location is specified with the @code{--with-system-gdbinit}
1082 configure option (@pxref{System-wide configuration}).
1083 It is loaded first when @value{GDBN} starts, before command line options
1084 have been processed.
1085 @item @file{~/.gdbinit}
1086 This is the init file in your home directory.
1087 It is loaded next, after @file{system.gdbinit}, and before
1088 command options have been processed.
1089 @item @file{./.gdbinit}
1090 This is the init file in the current directory.
1091 It is loaded last, after command line options other than @code{-x} and
1092 @code{-ex} have been processed. Command line options @code{-x} and
1093 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1096 For further documentation on startup processing, @xref{Startup}.
1097 For documentation on how to write command files,
1098 @xref{Command Files,,Command Files}.
1103 Do not execute commands found in @file{~/.gdbinit}, the init file
1104 in your home directory.
1110 @cindex @code{--quiet}
1111 @cindex @code{--silent}
1113 ``Quiet''. Do not print the introductory and copyright messages. These
1114 messages are also suppressed in batch mode.
1117 @cindex @code{--batch}
1118 Run in batch mode. Exit with status @code{0} after processing all the
1119 command files specified with @samp{-x} (and all commands from
1120 initialization files, if not inhibited with @samp{-n}). Exit with
1121 nonzero status if an error occurs in executing the @value{GDBN} commands
1122 in the command files. Batch mode also disables pagination, sets unlimited
1123 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1124 off} were in effect (@pxref{Messages/Warnings}).
1126 Batch mode may be useful for running @value{GDBN} as a filter, for
1127 example to download and run a program on another computer; in order to
1128 make this more useful, the message
1131 Program exited normally.
1135 (which is ordinarily issued whenever a program running under
1136 @value{GDBN} control terminates) is not issued when running in batch
1140 @cindex @code{--batch-silent}
1141 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1142 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1143 unaffected). This is much quieter than @samp{-silent} and would be useless
1144 for an interactive session.
1146 This is particularly useful when using targets that give @samp{Loading section}
1147 messages, for example.
1149 Note that targets that give their output via @value{GDBN}, as opposed to
1150 writing directly to @code{stdout}, will also be made silent.
1152 @item -return-child-result
1153 @cindex @code{--return-child-result}
1154 The return code from @value{GDBN} will be the return code from the child
1155 process (the process being debugged), with the following exceptions:
1159 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1160 internal error. In this case the exit code is the same as it would have been
1161 without @samp{-return-child-result}.
1163 The user quits with an explicit value. E.g., @samp{quit 1}.
1165 The child process never runs, or is not allowed to terminate, in which case
1166 the exit code will be -1.
1169 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1170 when @value{GDBN} is being used as a remote program loader or simulator
1175 @cindex @code{--nowindows}
1177 ``No windows''. If @value{GDBN} comes with a graphical user interface
1178 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1179 interface. If no GUI is available, this option has no effect.
1183 @cindex @code{--windows}
1185 If @value{GDBN} includes a GUI, then this option requires it to be
1188 @item -cd @var{directory}
1190 Run @value{GDBN} using @var{directory} as its working directory,
1191 instead of the current directory.
1193 @item -data-directory @var{directory}
1194 @itemx -D @var{directory}
1195 @cindex @code{--data-directory}
1197 Run @value{GDBN} using @var{directory} as its data directory.
1198 The data directory is where @value{GDBN} searches for its
1199 auxiliary files. @xref{Data Files}.
1203 @cindex @code{--fullname}
1205 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1206 subprocess. It tells @value{GDBN} to output the full file name and line
1207 number in a standard, recognizable fashion each time a stack frame is
1208 displayed (which includes each time your program stops). This
1209 recognizable format looks like two @samp{\032} characters, followed by
1210 the file name, line number and character position separated by colons,
1211 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1212 @samp{\032} characters as a signal to display the source code for the
1215 @item -annotate @var{level}
1216 @cindex @code{--annotate}
1217 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1218 effect is identical to using @samp{set annotate @var{level}}
1219 (@pxref{Annotations}). The annotation @var{level} controls how much
1220 information @value{GDBN} prints together with its prompt, values of
1221 expressions, source lines, and other types of output. Level 0 is the
1222 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1223 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1224 that control @value{GDBN}, and level 2 has been deprecated.
1226 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1230 @cindex @code{--args}
1231 Change interpretation of command line so that arguments following the
1232 executable file are passed as command line arguments to the inferior.
1233 This option stops option processing.
1235 @item -baud @var{bps}
1237 @cindex @code{--baud}
1239 Set the line speed (baud rate or bits per second) of any serial
1240 interface used by @value{GDBN} for remote debugging.
1242 @item -l @var{timeout}
1244 Set the timeout (in seconds) of any communication used by @value{GDBN}
1245 for remote debugging.
1247 @item -tty @var{device}
1248 @itemx -t @var{device}
1249 @cindex @code{--tty}
1251 Run using @var{device} for your program's standard input and output.
1252 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1254 @c resolve the situation of these eventually
1256 @cindex @code{--tui}
1257 Activate the @dfn{Text User Interface} when starting. The Text User
1258 Interface manages several text windows on the terminal, showing
1259 source, assembly, registers and @value{GDBN} command outputs
1260 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1261 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1262 Using @value{GDBN} under @sc{gnu} Emacs}).
1264 @item -interpreter @var{interp}
1265 @cindex @code{--interpreter}
1266 Use the interpreter @var{interp} for interface with the controlling
1267 program or device. This option is meant to be set by programs which
1268 communicate with @value{GDBN} using it as a back end.
1269 @xref{Interpreters, , Command Interpreters}.
1271 @samp{--interpreter=mi} (or @samp{--interpreter=mi3}) causes
1272 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1273 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1274 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1275 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1276 interfaces are no longer supported.
1279 @cindex @code{--write}
1280 Open the executable and core files for both reading and writing. This
1281 is equivalent to the @samp{set write on} command inside @value{GDBN}
1285 @cindex @code{--statistics}
1286 This option causes @value{GDBN} to print statistics about time and
1287 memory usage after it completes each command and returns to the prompt.
1290 @cindex @code{--version}
1291 This option causes @value{GDBN} to print its version number and
1292 no-warranty blurb, and exit.
1294 @item -configuration
1295 @cindex @code{--configuration}
1296 This option causes @value{GDBN} to print details about its build-time
1297 configuration parameters, and then exit. These details can be
1298 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1303 @subsection What @value{GDBN} Does During Startup
1304 @cindex @value{GDBN} startup
1306 Here's the description of what @value{GDBN} does during session startup:
1310 Sets up the command interpreter as specified by the command line
1311 (@pxref{Mode Options, interpreter}).
1315 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1316 used when building @value{GDBN}; @pxref{System-wide configuration,
1317 ,System-wide configuration and settings}) and executes all the commands in
1320 @anchor{Home Directory Init File}
1322 Reads the init file (if any) in your home directory@footnote{On
1323 DOS/Windows systems, the home directory is the one pointed to by the
1324 @code{HOME} environment variable.} and executes all the commands in
1327 @anchor{Option -init-eval-command}
1329 Executes commands and command files specified by the @samp{-iex} and
1330 @samp{-ix} options in their specified order. Usually you should use the
1331 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1332 settings before @value{GDBN} init files get executed and before inferior
1336 Processes command line options and operands.
1338 @anchor{Init File in the Current Directory during Startup}
1340 Reads and executes the commands from init file (if any) in the current
1341 working directory as long as @samp{set auto-load local-gdbinit} is set to
1342 @samp{on} (@pxref{Init File in the Current Directory}).
1343 This is only done if the current directory is
1344 different from your home directory. Thus, you can have more than one
1345 init file, one generic in your home directory, and another, specific
1346 to the program you are debugging, in the directory where you invoke
1350 If the command line specified a program to debug, or a process to
1351 attach to, or a core file, @value{GDBN} loads any auto-loaded
1352 scripts provided for the program or for its loaded shared libraries.
1353 @xref{Auto-loading}.
1355 If you wish to disable the auto-loading during startup,
1356 you must do something like the following:
1359 $ gdb -iex "set auto-load python-scripts off" myprogram
1362 Option @samp{-ex} does not work because the auto-loading is then turned
1366 Executes commands and command files specified by the @samp{-ex} and
1367 @samp{-x} options in their specified order. @xref{Command Files}, for
1368 more details about @value{GDBN} command files.
1371 Reads the command history recorded in the @dfn{history file}.
1372 @xref{Command History}, for more details about the command history and the
1373 files where @value{GDBN} records it.
1376 Init files use the same syntax as @dfn{command files} (@pxref{Command
1377 Files}) and are processed by @value{GDBN} in the same way. The init
1378 file in your home directory can set options (such as @samp{set
1379 complaints}) that affect subsequent processing of command line options
1380 and operands. Init files are not executed if you use the @samp{-nx}
1381 option (@pxref{Mode Options, ,Choosing Modes}).
1383 To display the list of init files loaded by gdb at startup, you
1384 can use @kbd{gdb --help}.
1386 @cindex init file name
1387 @cindex @file{.gdbinit}
1388 @cindex @file{gdb.ini}
1389 The @value{GDBN} init files are normally called @file{.gdbinit}.
1390 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1391 the limitations of file names imposed by DOS filesystems. The Windows
1392 port of @value{GDBN} uses the standard name, but if it finds a
1393 @file{gdb.ini} file in your home directory, it warns you about that
1394 and suggests to rename the file to the standard name.
1398 @section Quitting @value{GDBN}
1399 @cindex exiting @value{GDBN}
1400 @cindex leaving @value{GDBN}
1403 @kindex quit @r{[}@var{expression}@r{]}
1404 @kindex q @r{(@code{quit})}
1405 @item quit @r{[}@var{expression}@r{]}
1407 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1408 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1409 do not supply @var{expression}, @value{GDBN} will terminate normally;
1410 otherwise it will terminate using the result of @var{expression} as the
1415 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1416 terminates the action of any @value{GDBN} command that is in progress and
1417 returns to @value{GDBN} command level. It is safe to type the interrupt
1418 character at any time because @value{GDBN} does not allow it to take effect
1419 until a time when it is safe.
1421 If you have been using @value{GDBN} to control an attached process or
1422 device, you can release it with the @code{detach} command
1423 (@pxref{Attach, ,Debugging an Already-running Process}).
1425 @node Shell Commands
1426 @section Shell Commands
1428 If you need to execute occasional shell commands during your
1429 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1430 just use the @code{shell} command.
1435 @cindex shell escape
1436 @item shell @var{command-string}
1437 @itemx !@var{command-string}
1438 Invoke a standard shell to execute @var{command-string}.
1439 Note that no space is needed between @code{!} and @var{command-string}.
1440 If it exists, the environment variable @code{SHELL} determines which
1441 shell to run. Otherwise @value{GDBN} uses the default shell
1442 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1445 The utility @code{make} is often needed in development environments.
1446 You do not have to use the @code{shell} command for this purpose in
1451 @cindex calling make
1452 @item make @var{make-args}
1453 Execute the @code{make} program with the specified
1454 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1457 @node Logging Output
1458 @section Logging Output
1459 @cindex logging @value{GDBN} output
1460 @cindex save @value{GDBN} output to a file
1462 You may want to save the output of @value{GDBN} commands to a file.
1463 There are several commands to control @value{GDBN}'s logging.
1467 @item set logging on
1469 @item set logging off
1471 @cindex logging file name
1472 @item set logging file @var{file}
1473 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1474 @item set logging overwrite [on|off]
1475 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1476 you want @code{set logging on} to overwrite the logfile instead.
1477 @item set logging redirect [on|off]
1478 By default, @value{GDBN} output will go to both the terminal and the logfile.
1479 Set @code{redirect} if you want output to go only to the log file.
1480 @kindex show logging
1482 Show the current values of the logging settings.
1486 @chapter @value{GDBN} Commands
1488 You can abbreviate a @value{GDBN} command to the first few letters of the command
1489 name, if that abbreviation is unambiguous; and you can repeat certain
1490 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1491 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1492 show you the alternatives available, if there is more than one possibility).
1495 * Command Syntax:: How to give commands to @value{GDBN}
1496 * Completion:: Command completion
1497 * Help:: How to ask @value{GDBN} for help
1500 @node Command Syntax
1501 @section Command Syntax
1503 A @value{GDBN} command is a single line of input. There is no limit on
1504 how long it can be. It starts with a command name, which is followed by
1505 arguments whose meaning depends on the command name. For example, the
1506 command @code{step} accepts an argument which is the number of times to
1507 step, as in @samp{step 5}. You can also use the @code{step} command
1508 with no arguments. Some commands do not allow any arguments.
1510 @cindex abbreviation
1511 @value{GDBN} command names may always be truncated if that abbreviation is
1512 unambiguous. Other possible command abbreviations are listed in the
1513 documentation for individual commands. In some cases, even ambiguous
1514 abbreviations are allowed; for example, @code{s} is specially defined as
1515 equivalent to @code{step} even though there are other commands whose
1516 names start with @code{s}. You can test abbreviations by using them as
1517 arguments to the @code{help} command.
1519 @cindex repeating commands
1520 @kindex RET @r{(repeat last command)}
1521 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1522 repeat the previous command. Certain commands (for example, @code{run})
1523 will not repeat this way; these are commands whose unintentional
1524 repetition might cause trouble and which you are unlikely to want to
1525 repeat. User-defined commands can disable this feature; see
1526 @ref{Define, dont-repeat}.
1528 The @code{list} and @code{x} commands, when you repeat them with
1529 @key{RET}, construct new arguments rather than repeating
1530 exactly as typed. This permits easy scanning of source or memory.
1532 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1533 output, in a way similar to the common utility @code{more}
1534 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1535 @key{RET} too many in this situation, @value{GDBN} disables command
1536 repetition after any command that generates this sort of display.
1538 @kindex # @r{(a comment)}
1540 Any text from a @kbd{#} to the end of the line is a comment; it does
1541 nothing. This is useful mainly in command files (@pxref{Command
1542 Files,,Command Files}).
1544 @cindex repeating command sequences
1545 @kindex Ctrl-o @r{(operate-and-get-next)}
1546 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1547 commands. This command accepts the current line, like @key{RET}, and
1548 then fetches the next line relative to the current line from the history
1552 @section Command Completion
1555 @cindex word completion
1556 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1557 only one possibility; it can also show you what the valid possibilities
1558 are for the next word in a command, at any time. This works for @value{GDBN}
1559 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1561 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1562 of a word. If there is only one possibility, @value{GDBN} fills in the
1563 word, and waits for you to finish the command (or press @key{RET} to
1564 enter it). For example, if you type
1566 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1567 @c complete accuracy in these examples; space introduced for clarity.
1568 @c If texinfo enhancements make it unnecessary, it would be nice to
1569 @c replace " @key" by "@key" in the following...
1571 (@value{GDBP}) info bre @key{TAB}
1575 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1576 the only @code{info} subcommand beginning with @samp{bre}:
1579 (@value{GDBP}) info breakpoints
1583 You can either press @key{RET} at this point, to run the @code{info
1584 breakpoints} command, or backspace and enter something else, if
1585 @samp{breakpoints} does not look like the command you expected. (If you
1586 were sure you wanted @code{info breakpoints} in the first place, you
1587 might as well just type @key{RET} immediately after @samp{info bre},
1588 to exploit command abbreviations rather than command completion).
1590 If there is more than one possibility for the next word when you press
1591 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1592 characters and try again, or just press @key{TAB} a second time;
1593 @value{GDBN} displays all the possible completions for that word. For
1594 example, you might want to set a breakpoint on a subroutine whose name
1595 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1596 just sounds the bell. Typing @key{TAB} again displays all the
1597 function names in your program that begin with those characters, for
1601 (@value{GDBP}) b make_ @key{TAB}
1602 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1603 make_a_section_from_file make_environ
1604 make_abs_section make_function_type
1605 make_blockvector make_pointer_type
1606 make_cleanup make_reference_type
1607 make_command make_symbol_completion_list
1608 (@value{GDBP}) b make_
1612 After displaying the available possibilities, @value{GDBN} copies your
1613 partial input (@samp{b make_} in the example) so you can finish the
1616 If you just want to see the list of alternatives in the first place, you
1617 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1618 means @kbd{@key{META} ?}. You can type this either by holding down a
1619 key designated as the @key{META} shift on your keyboard (if there is
1620 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1622 If the number of possible completions is large, @value{GDBN} will
1623 print as much of the list as it has collected, as well as a message
1624 indicating that the list may be truncated.
1627 (@value{GDBP}) b m@key{TAB}@key{TAB}
1629 <... the rest of the possible completions ...>
1630 *** List may be truncated, max-completions reached. ***
1635 This behavior can be controlled with the following commands:
1638 @kindex set max-completions
1639 @item set max-completions @var{limit}
1640 @itemx set max-completions unlimited
1641 Set the maximum number of completion candidates. @value{GDBN} will
1642 stop looking for more completions once it collects this many candidates.
1643 This is useful when completing on things like function names as collecting
1644 all the possible candidates can be time consuming.
1645 The default value is 200. A value of zero disables tab-completion.
1646 Note that setting either no limit or a very large limit can make
1648 @kindex show max-completions
1649 @item show max-completions
1650 Show the maximum number of candidates that @value{GDBN} will collect and show
1654 @cindex quotes in commands
1655 @cindex completion of quoted strings
1656 Sometimes the string you need, while logically a ``word'', may contain
1657 parentheses or other characters that @value{GDBN} normally excludes from
1658 its notion of a word. To permit word completion to work in this
1659 situation, you may enclose words in @code{'} (single quote marks) in
1660 @value{GDBN} commands.
1662 A likely situation where you might need this is in typing an
1663 expression that involves a C@t{++} symbol name with template
1664 parameters. This is because when completing expressions, GDB treats
1665 the @samp{<} character as word delimiter, assuming that it's the
1666 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1669 For example, when you want to call a C@t{++} template function
1670 interactively using the @code{print} or @code{call} commands, you may
1671 need to distinguish whether you mean the version of @code{name} that
1672 was specialized for @code{int}, @code{name<int>()}, or the version
1673 that was specialized for @code{float}, @code{name<float>()}. To use
1674 the word-completion facilities in this situation, type a single quote
1675 @code{'} at the beginning of the function name. This alerts
1676 @value{GDBN} that it may need to consider more information than usual
1677 when you press @key{TAB} or @kbd{M-?} to request word completion:
1680 (@value{GDBP}) p 'func< @kbd{M-?}
1681 func<int>() func<float>()
1682 (@value{GDBP}) p 'func<
1685 When setting breakpoints however (@pxref{Specify Location}), you don't
1686 usually need to type a quote before the function name, because
1687 @value{GDBN} understands that you want to set a breakpoint on a
1691 (@value{GDBP}) b func< @kbd{M-?}
1692 func<int>() func<float>()
1693 (@value{GDBP}) b func<
1696 This is true even in the case of typing the name of C@t{++} overloaded
1697 functions (multiple definitions of the same function, distinguished by
1698 argument type). For example, when you want to set a breakpoint you
1699 don't need to distinguish whether you mean the version of @code{name}
1700 that takes an @code{int} parameter, @code{name(int)}, or the version
1701 that takes a @code{float} parameter, @code{name(float)}.
1704 (@value{GDBP}) b bubble( @kbd{M-?}
1705 bubble(int) bubble(double)
1706 (@value{GDBP}) b bubble(dou @kbd{M-?}
1710 See @ref{quoting names} for a description of other scenarios that
1713 For more information about overloaded functions, see @ref{C Plus Plus
1714 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1715 overload-resolution off} to disable overload resolution;
1716 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1718 @cindex completion of structure field names
1719 @cindex structure field name completion
1720 @cindex completion of union field names
1721 @cindex union field name completion
1722 When completing in an expression which looks up a field in a
1723 structure, @value{GDBN} also tries@footnote{The completer can be
1724 confused by certain kinds of invalid expressions. Also, it only
1725 examines the static type of the expression, not the dynamic type.} to
1726 limit completions to the field names available in the type of the
1730 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1731 magic to_fputs to_rewind
1732 to_data to_isatty to_write
1733 to_delete to_put to_write_async_safe
1738 This is because the @code{gdb_stdout} is a variable of the type
1739 @code{struct ui_file} that is defined in @value{GDBN} sources as
1746 ui_file_flush_ftype *to_flush;
1747 ui_file_write_ftype *to_write;
1748 ui_file_write_async_safe_ftype *to_write_async_safe;
1749 ui_file_fputs_ftype *to_fputs;
1750 ui_file_read_ftype *to_read;
1751 ui_file_delete_ftype *to_delete;
1752 ui_file_isatty_ftype *to_isatty;
1753 ui_file_rewind_ftype *to_rewind;
1754 ui_file_put_ftype *to_put;
1761 @section Getting Help
1762 @cindex online documentation
1765 You can always ask @value{GDBN} itself for information on its commands,
1766 using the command @code{help}.
1769 @kindex h @r{(@code{help})}
1772 You can use @code{help} (abbreviated @code{h}) with no arguments to
1773 display a short list of named classes of commands:
1777 List of classes of commands:
1779 aliases -- Aliases of other commands
1780 breakpoints -- Making program stop at certain points
1781 data -- Examining data
1782 files -- Specifying and examining files
1783 internals -- Maintenance commands
1784 obscure -- Obscure features
1785 running -- Running the program
1786 stack -- Examining the stack
1787 status -- Status inquiries
1788 support -- Support facilities
1789 tracepoints -- Tracing of program execution without
1790 stopping the program
1791 user-defined -- User-defined commands
1793 Type "help" followed by a class name for a list of
1794 commands in that class.
1795 Type "help" followed by command name for full
1797 Command name abbreviations are allowed if unambiguous.
1800 @c the above line break eliminates huge line overfull...
1802 @item help @var{class}
1803 Using one of the general help classes as an argument, you can get a
1804 list of the individual commands in that class. For example, here is the
1805 help display for the class @code{status}:
1808 (@value{GDBP}) help status
1813 @c Line break in "show" line falsifies real output, but needed
1814 @c to fit in smallbook page size.
1815 info -- Generic command for showing things
1816 about the program being debugged
1817 show -- Generic command for showing things
1820 Type "help" followed by command name for full
1822 Command name abbreviations are allowed if unambiguous.
1826 @item help @var{command}
1827 With a command name as @code{help} argument, @value{GDBN} displays a
1828 short paragraph on how to use that command.
1831 @item apropos @var{args}
1832 The @code{apropos} command searches through all of the @value{GDBN}
1833 commands, and their documentation, for the regular expression specified in
1834 @var{args}. It prints out all matches found. For example:
1845 alias -- Define a new command that is an alias of an existing command
1846 aliases -- Aliases of other commands
1847 d -- Delete some breakpoints or auto-display expressions
1848 del -- Delete some breakpoints or auto-display expressions
1849 delete -- Delete some breakpoints or auto-display expressions
1854 @item complete @var{args}
1855 The @code{complete @var{args}} command lists all the possible completions
1856 for the beginning of a command. Use @var{args} to specify the beginning of the
1857 command you want completed. For example:
1863 @noindent results in:
1874 @noindent This is intended for use by @sc{gnu} Emacs.
1877 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1878 and @code{show} to inquire about the state of your program, or the state
1879 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1880 manual introduces each of them in the appropriate context. The listings
1881 under @code{info} and under @code{show} in the Command, Variable, and
1882 Function Index point to all the sub-commands. @xref{Command and Variable
1888 @kindex i @r{(@code{info})}
1890 This command (abbreviated @code{i}) is for describing the state of your
1891 program. For example, you can show the arguments passed to a function
1892 with @code{info args}, list the registers currently in use with @code{info
1893 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1894 You can get a complete list of the @code{info} sub-commands with
1895 @w{@code{help info}}.
1899 You can assign the result of an expression to an environment variable with
1900 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1901 @code{set prompt $}.
1905 In contrast to @code{info}, @code{show} is for describing the state of
1906 @value{GDBN} itself.
1907 You can change most of the things you can @code{show}, by using the
1908 related command @code{set}; for example, you can control what number
1909 system is used for displays with @code{set radix}, or simply inquire
1910 which is currently in use with @code{show radix}.
1913 To display all the settable parameters and their current
1914 values, you can use @code{show} with no arguments; you may also use
1915 @code{info set}. Both commands produce the same display.
1916 @c FIXME: "info set" violates the rule that "info" is for state of
1917 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1918 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1922 Here are several miscellaneous @code{show} subcommands, all of which are
1923 exceptional in lacking corresponding @code{set} commands:
1926 @kindex show version
1927 @cindex @value{GDBN} version number
1929 Show what version of @value{GDBN} is running. You should include this
1930 information in @value{GDBN} bug-reports. If multiple versions of
1931 @value{GDBN} are in use at your site, you may need to determine which
1932 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1933 commands are introduced, and old ones may wither away. Also, many
1934 system vendors ship variant versions of @value{GDBN}, and there are
1935 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1936 The version number is the same as the one announced when you start
1939 @kindex show copying
1940 @kindex info copying
1941 @cindex display @value{GDBN} copyright
1944 Display information about permission for copying @value{GDBN}.
1946 @kindex show warranty
1947 @kindex info warranty
1949 @itemx info warranty
1950 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1951 if your version of @value{GDBN} comes with one.
1953 @kindex show configuration
1954 @item show configuration
1955 Display detailed information about the way @value{GDBN} was configured
1956 when it was built. This displays the optional arguments passed to the
1957 @file{configure} script and also configuration parameters detected
1958 automatically by @command{configure}. When reporting a @value{GDBN}
1959 bug (@pxref{GDB Bugs}), it is important to include this information in
1965 @chapter Running Programs Under @value{GDBN}
1967 When you run a program under @value{GDBN}, you must first generate
1968 debugging information when you compile it.
1970 You may start @value{GDBN} with its arguments, if any, in an environment
1971 of your choice. If you are doing native debugging, you may redirect
1972 your program's input and output, debug an already running process, or
1973 kill a child process.
1976 * Compilation:: Compiling for debugging
1977 * Starting:: Starting your program
1978 * Arguments:: Your program's arguments
1979 * Environment:: Your program's environment
1981 * Working Directory:: Your program's working directory
1982 * Input/Output:: Your program's input and output
1983 * Attach:: Debugging an already-running process
1984 * Kill Process:: Killing the child process
1986 * Inferiors and Programs:: Debugging multiple inferiors and programs
1987 * Threads:: Debugging programs with multiple threads
1988 * Forks:: Debugging forks
1989 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1993 @section Compiling for Debugging
1995 In order to debug a program effectively, you need to generate
1996 debugging information when you compile it. This debugging information
1997 is stored in the object file; it describes the data type of each
1998 variable or function and the correspondence between source line numbers
1999 and addresses in the executable code.
2001 To request debugging information, specify the @samp{-g} option when you run
2004 Programs that are to be shipped to your customers are compiled with
2005 optimizations, using the @samp{-O} compiler option. However, some
2006 compilers are unable to handle the @samp{-g} and @samp{-O} options
2007 together. Using those compilers, you cannot generate optimized
2008 executables containing debugging information.
2010 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2011 without @samp{-O}, making it possible to debug optimized code. We
2012 recommend that you @emph{always} use @samp{-g} whenever you compile a
2013 program. You may think your program is correct, but there is no sense
2014 in pushing your luck. For more information, see @ref{Optimized Code}.
2016 Older versions of the @sc{gnu} C compiler permitted a variant option
2017 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2018 format; if your @sc{gnu} C compiler has this option, do not use it.
2020 @value{GDBN} knows about preprocessor macros and can show you their
2021 expansion (@pxref{Macros}). Most compilers do not include information
2022 about preprocessor macros in the debugging information if you specify
2023 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2024 the @sc{gnu} C compiler, provides macro information if you are using
2025 the DWARF debugging format, and specify the option @option{-g3}.
2027 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2028 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2029 information on @value{NGCC} options affecting debug information.
2031 You will have the best debugging experience if you use the latest
2032 version of the DWARF debugging format that your compiler supports.
2033 DWARF is currently the most expressive and best supported debugging
2034 format in @value{GDBN}.
2038 @section Starting your Program
2044 @kindex r @r{(@code{run})}
2047 Use the @code{run} command to start your program under @value{GDBN}.
2048 You must first specify the program name with an argument to
2049 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2050 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2051 command (@pxref{Files, ,Commands to Specify Files}).
2055 If you are running your program in an execution environment that
2056 supports processes, @code{run} creates an inferior process and makes
2057 that process run your program. In some environments without processes,
2058 @code{run} jumps to the start of your program. Other targets,
2059 like @samp{remote}, are always running. If you get an error
2060 message like this one:
2063 The "remote" target does not support "run".
2064 Try "help target" or "continue".
2068 then use @code{continue} to run your program. You may need @code{load}
2069 first (@pxref{load}).
2071 The execution of a program is affected by certain information it
2072 receives from its superior. @value{GDBN} provides ways to specify this
2073 information, which you must do @emph{before} starting your program. (You
2074 can change it after starting your program, but such changes only affect
2075 your program the next time you start it.) This information may be
2076 divided into four categories:
2079 @item The @emph{arguments.}
2080 Specify the arguments to give your program as the arguments of the
2081 @code{run} command. If a shell is available on your target, the shell
2082 is used to pass the arguments, so that you may use normal conventions
2083 (such as wildcard expansion or variable substitution) in describing
2085 In Unix systems, you can control which shell is used with the
2086 @code{SHELL} environment variable. If you do not define @code{SHELL},
2087 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2088 use of any shell with the @code{set startup-with-shell} command (see
2091 @item The @emph{environment.}
2092 Your program normally inherits its environment from @value{GDBN}, but you can
2093 use the @value{GDBN} commands @code{set environment} and @code{unset
2094 environment} to change parts of the environment that affect
2095 your program. @xref{Environment, ,Your Program's Environment}.
2097 @item The @emph{working directory.}
2098 You can set your program's working directory with the command
2099 @kbd{set cwd}. If you do not set any working directory with this
2100 command, your program will inherit @value{GDBN}'s working directory if
2101 native debugging, or the remote server's working directory if remote
2102 debugging. @xref{Working Directory, ,Your Program's Working
2105 @item The @emph{standard input and output.}
2106 Your program normally uses the same device for standard input and
2107 standard output as @value{GDBN} is using. You can redirect input and output
2108 in the @code{run} command line, or you can use the @code{tty} command to
2109 set a different device for your program.
2110 @xref{Input/Output, ,Your Program's Input and Output}.
2113 @emph{Warning:} While input and output redirection work, you cannot use
2114 pipes to pass the output of the program you are debugging to another
2115 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2119 When you issue the @code{run} command, your program begins to execute
2120 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2121 of how to arrange for your program to stop. Once your program has
2122 stopped, you may call functions in your program, using the @code{print}
2123 or @code{call} commands. @xref{Data, ,Examining Data}.
2125 If the modification time of your symbol file has changed since the last
2126 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2127 table, and reads it again. When it does this, @value{GDBN} tries to retain
2128 your current breakpoints.
2133 @cindex run to main procedure
2134 The name of the main procedure can vary from language to language.
2135 With C or C@t{++}, the main procedure name is always @code{main}, but
2136 other languages such as Ada do not require a specific name for their
2137 main procedure. The debugger provides a convenient way to start the
2138 execution of the program and to stop at the beginning of the main
2139 procedure, depending on the language used.
2141 The @samp{start} command does the equivalent of setting a temporary
2142 breakpoint at the beginning of the main procedure and then invoking
2143 the @samp{run} command.
2145 @cindex elaboration phase
2146 Some programs contain an @dfn{elaboration} phase where some startup code is
2147 executed before the main procedure is called. This depends on the
2148 languages used to write your program. In C@t{++}, for instance,
2149 constructors for static and global objects are executed before
2150 @code{main} is called. It is therefore possible that the debugger stops
2151 before reaching the main procedure. However, the temporary breakpoint
2152 will remain to halt execution.
2154 Specify the arguments to give to your program as arguments to the
2155 @samp{start} command. These arguments will be given verbatim to the
2156 underlying @samp{run} command. Note that the same arguments will be
2157 reused if no argument is provided during subsequent calls to
2158 @samp{start} or @samp{run}.
2160 It is sometimes necessary to debug the program during elaboration. In
2161 these cases, using the @code{start} command would stop the execution
2162 of your program too late, as the program would have already completed
2163 the elaboration phase. Under these circumstances, either insert
2164 breakpoints in your elaboration code before running your program or
2165 use the @code{starti} command.
2169 @cindex run to first instruction
2170 The @samp{starti} command does the equivalent of setting a temporary
2171 breakpoint at the first instruction of a program's execution and then
2172 invoking the @samp{run} command. For programs containing an
2173 elaboration phase, the @code{starti} command will stop execution at
2174 the start of the elaboration phase.
2176 @anchor{set exec-wrapper}
2177 @kindex set exec-wrapper
2178 @item set exec-wrapper @var{wrapper}
2179 @itemx show exec-wrapper
2180 @itemx unset exec-wrapper
2181 When @samp{exec-wrapper} is set, the specified wrapper is used to
2182 launch programs for debugging. @value{GDBN} starts your program
2183 with a shell command of the form @kbd{exec @var{wrapper}
2184 @var{program}}. Quoting is added to @var{program} and its
2185 arguments, but not to @var{wrapper}, so you should add quotes if
2186 appropriate for your shell. The wrapper runs until it executes
2187 your program, and then @value{GDBN} takes control.
2189 You can use any program that eventually calls @code{execve} with
2190 its arguments as a wrapper. Several standard Unix utilities do
2191 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2192 with @code{exec "$@@"} will also work.
2194 For example, you can use @code{env} to pass an environment variable to
2195 the debugged program, without setting the variable in your shell's
2199 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2203 This command is available when debugging locally on most targets, excluding
2204 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2206 @kindex set startup-with-shell
2207 @anchor{set startup-with-shell}
2208 @item set startup-with-shell
2209 @itemx set startup-with-shell on
2210 @itemx set startup-with-shell off
2211 @itemx show startup-with-shell
2212 On Unix systems, by default, if a shell is available on your target,
2213 @value{GDBN}) uses it to start your program. Arguments of the
2214 @code{run} command are passed to the shell, which does variable
2215 substitution, expands wildcard characters and performs redirection of
2216 I/O. In some circumstances, it may be useful to disable such use of a
2217 shell, for example, when debugging the shell itself or diagnosing
2218 startup failures such as:
2222 Starting program: ./a.out
2223 During startup program terminated with signal SIGSEGV, Segmentation fault.
2227 which indicates the shell or the wrapper specified with
2228 @samp{exec-wrapper} crashed, not your program. Most often, this is
2229 caused by something odd in your shell's non-interactive mode
2230 initialization file---such as @file{.cshrc} for C-shell,
2231 $@file{.zshenv} for the Z shell, or the file specified in the
2232 @samp{BASH_ENV} environment variable for BASH.
2234 @anchor{set auto-connect-native-target}
2235 @kindex set auto-connect-native-target
2236 @item set auto-connect-native-target
2237 @itemx set auto-connect-native-target on
2238 @itemx set auto-connect-native-target off
2239 @itemx show auto-connect-native-target
2241 By default, if not connected to any target yet (e.g., with
2242 @code{target remote}), the @code{run} command starts your program as a
2243 native process under @value{GDBN}, on your local machine. If you're
2244 sure you don't want to debug programs on your local machine, you can
2245 tell @value{GDBN} to not connect to the native target automatically
2246 with the @code{set auto-connect-native-target off} command.
2248 If @code{on}, which is the default, and if @value{GDBN} is not
2249 connected to a target already, the @code{run} command automaticaly
2250 connects to the native target, if one is available.
2252 If @code{off}, and if @value{GDBN} is not connected to a target
2253 already, the @code{run} command fails with an error:
2257 Don't know how to run. Try "help target".
2260 If @value{GDBN} is already connected to a target, @value{GDBN} always
2261 uses it with the @code{run} command.
2263 In any case, you can explicitly connect to the native target with the
2264 @code{target native} command. For example,
2267 (@value{GDBP}) set auto-connect-native-target off
2269 Don't know how to run. Try "help target".
2270 (@value{GDBP}) target native
2272 Starting program: ./a.out
2273 [Inferior 1 (process 10421) exited normally]
2276 In case you connected explicitly to the @code{native} target,
2277 @value{GDBN} remains connected even if all inferiors exit, ready for
2278 the next @code{run} command. Use the @code{disconnect} command to
2281 Examples of other commands that likewise respect the
2282 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2283 proc}, @code{info os}.
2285 @kindex set disable-randomization
2286 @item set disable-randomization
2287 @itemx set disable-randomization on
2288 This option (enabled by default in @value{GDBN}) will turn off the native
2289 randomization of the virtual address space of the started program. This option
2290 is useful for multiple debugging sessions to make the execution better
2291 reproducible and memory addresses reusable across debugging sessions.
2293 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2294 On @sc{gnu}/Linux you can get the same behavior using
2297 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2300 @item set disable-randomization off
2301 Leave the behavior of the started executable unchanged. Some bugs rear their
2302 ugly heads only when the program is loaded at certain addresses. If your bug
2303 disappears when you run the program under @value{GDBN}, that might be because
2304 @value{GDBN} by default disables the address randomization on platforms, such
2305 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2306 disable-randomization off} to try to reproduce such elusive bugs.
2308 On targets where it is available, virtual address space randomization
2309 protects the programs against certain kinds of security attacks. In these
2310 cases the attacker needs to know the exact location of a concrete executable
2311 code. Randomizing its location makes it impossible to inject jumps misusing
2312 a code at its expected addresses.
2314 Prelinking shared libraries provides a startup performance advantage but it
2315 makes addresses in these libraries predictable for privileged processes by
2316 having just unprivileged access at the target system. Reading the shared
2317 library binary gives enough information for assembling the malicious code
2318 misusing it. Still even a prelinked shared library can get loaded at a new
2319 random address just requiring the regular relocation process during the
2320 startup. Shared libraries not already prelinked are always loaded at
2321 a randomly chosen address.
2323 Position independent executables (PIE) contain position independent code
2324 similar to the shared libraries and therefore such executables get loaded at
2325 a randomly chosen address upon startup. PIE executables always load even
2326 already prelinked shared libraries at a random address. You can build such
2327 executable using @command{gcc -fPIE -pie}.
2329 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2330 (as long as the randomization is enabled).
2332 @item show disable-randomization
2333 Show the current setting of the explicit disable of the native randomization of
2334 the virtual address space of the started program.
2339 @section Your Program's Arguments
2341 @cindex arguments (to your program)
2342 The arguments to your program can be specified by the arguments of the
2344 They are passed to a shell, which expands wildcard characters and
2345 performs redirection of I/O, and thence to your program. Your
2346 @code{SHELL} environment variable (if it exists) specifies what shell
2347 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2348 the default shell (@file{/bin/sh} on Unix).
2350 On non-Unix systems, the program is usually invoked directly by
2351 @value{GDBN}, which emulates I/O redirection via the appropriate system
2352 calls, and the wildcard characters are expanded by the startup code of
2353 the program, not by the shell.
2355 @code{run} with no arguments uses the same arguments used by the previous
2356 @code{run}, or those set by the @code{set args} command.
2361 Specify the arguments to be used the next time your program is run. If
2362 @code{set args} has no arguments, @code{run} executes your program
2363 with no arguments. Once you have run your program with arguments,
2364 using @code{set args} before the next @code{run} is the only way to run
2365 it again without arguments.
2369 Show the arguments to give your program when it is started.
2373 @section Your Program's Environment
2375 @cindex environment (of your program)
2376 The @dfn{environment} consists of a set of environment variables and
2377 their values. Environment variables conventionally record such things as
2378 your user name, your home directory, your terminal type, and your search
2379 path for programs to run. Usually you set up environment variables with
2380 the shell and they are inherited by all the other programs you run. When
2381 debugging, it can be useful to try running your program with a modified
2382 environment without having to start @value{GDBN} over again.
2386 @item path @var{directory}
2387 Add @var{directory} to the front of the @code{PATH} environment variable
2388 (the search path for executables) that will be passed to your program.
2389 The value of @code{PATH} used by @value{GDBN} does not change.
2390 You may specify several directory names, separated by whitespace or by a
2391 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2392 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2393 is moved to the front, so it is searched sooner.
2395 You can use the string @samp{$cwd} to refer to whatever is the current
2396 working directory at the time @value{GDBN} searches the path. If you
2397 use @samp{.} instead, it refers to the directory where you executed the
2398 @code{path} command. @value{GDBN} replaces @samp{.} in the
2399 @var{directory} argument (with the current path) before adding
2400 @var{directory} to the search path.
2401 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2402 @c document that, since repeating it would be a no-op.
2406 Display the list of search paths for executables (the @code{PATH}
2407 environment variable).
2409 @kindex show environment
2410 @item show environment @r{[}@var{varname}@r{]}
2411 Print the value of environment variable @var{varname} to be given to
2412 your program when it starts. If you do not supply @var{varname},
2413 print the names and values of all environment variables to be given to
2414 your program. You can abbreviate @code{environment} as @code{env}.
2416 @kindex set environment
2417 @anchor{set environment}
2418 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2419 Set environment variable @var{varname} to @var{value}. The value
2420 changes for your program (and the shell @value{GDBN} uses to launch
2421 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2422 values of environment variables are just strings, and any
2423 interpretation is supplied by your program itself. The @var{value}
2424 parameter is optional; if it is eliminated, the variable is set to a
2426 @c "any string" here does not include leading, trailing
2427 @c blanks. Gnu asks: does anyone care?
2429 For example, this command:
2436 tells the debugged program, when subsequently run, that its user is named
2437 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2438 are not actually required.)
2440 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2441 which also inherits the environment set with @code{set environment}.
2442 If necessary, you can avoid that by using the @samp{env} program as a
2443 wrapper instead of using @code{set environment}. @xref{set
2444 exec-wrapper}, for an example doing just that.
2446 Environment variables that are set by the user are also transmitted to
2447 @command{gdbserver} to be used when starting the remote inferior.
2448 @pxref{QEnvironmentHexEncoded}.
2450 @kindex unset environment
2451 @anchor{unset environment}
2452 @item unset environment @var{varname}
2453 Remove variable @var{varname} from the environment to be passed to your
2454 program. This is different from @samp{set env @var{varname} =};
2455 @code{unset environment} removes the variable from the environment,
2456 rather than assigning it an empty value.
2458 Environment variables that are unset by the user are also unset on
2459 @command{gdbserver} when starting the remote inferior.
2460 @pxref{QEnvironmentUnset}.
2463 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2464 the shell indicated by your @code{SHELL} environment variable if it
2465 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2466 names a shell that runs an initialization file when started
2467 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2468 for the Z shell, or the file specified in the @samp{BASH_ENV}
2469 environment variable for BASH---any variables you set in that file
2470 affect your program. You may wish to move setting of environment
2471 variables to files that are only run when you sign on, such as
2472 @file{.login} or @file{.profile}.
2474 @node Working Directory
2475 @section Your Program's Working Directory
2477 @cindex working directory (of your program)
2478 Each time you start your program with @code{run}, the inferior will be
2479 initialized with the current working directory specified by the
2480 @kbd{set cwd} command. If no directory has been specified by this
2481 command, then the inferior will inherit @value{GDBN}'s current working
2482 directory as its working directory if native debugging, or it will
2483 inherit the remote server's current working directory if remote
2488 @cindex change inferior's working directory
2489 @anchor{set cwd command}
2490 @item set cwd @r{[}@var{directory}@r{]}
2491 Set the inferior's working directory to @var{directory}, which will be
2492 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2493 argument has been specified, the command clears the setting and resets
2494 it to an empty state. This setting has no effect on @value{GDBN}'s
2495 working directory, and it only takes effect the next time you start
2496 the inferior. The @file{~} in @var{directory} is a short for the
2497 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2498 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2499 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2502 You can also change @value{GDBN}'s current working directory by using
2503 the @code{cd} command.
2507 @cindex show inferior's working directory
2509 Show the inferior's working directory. If no directory has been
2510 specified by @kbd{set cwd}, then the default inferior's working
2511 directory is the same as @value{GDBN}'s working directory.
2514 @cindex change @value{GDBN}'s working directory
2516 @item cd @r{[}@var{directory}@r{]}
2517 Set the @value{GDBN} working directory to @var{directory}. If not
2518 given, @var{directory} uses @file{'~'}.
2520 The @value{GDBN} working directory serves as a default for the
2521 commands that specify files for @value{GDBN} to operate on.
2522 @xref{Files, ,Commands to Specify Files}.
2523 @xref{set cwd command}.
2527 Print the @value{GDBN} working directory.
2530 It is generally impossible to find the current working directory of
2531 the process being debugged (since a program can change its directory
2532 during its run). If you work on a system where @value{GDBN} supports
2533 the @code{info proc} command (@pxref{Process Information}), you can
2534 use the @code{info proc} command to find out the
2535 current working directory of the debuggee.
2538 @section Your Program's Input and Output
2543 By default, the program you run under @value{GDBN} does input and output to
2544 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2545 to its own terminal modes to interact with you, but it records the terminal
2546 modes your program was using and switches back to them when you continue
2547 running your program.
2550 @kindex info terminal
2552 Displays information recorded by @value{GDBN} about the terminal modes your
2556 You can redirect your program's input and/or output using shell
2557 redirection with the @code{run} command. For example,
2564 starts your program, diverting its output to the file @file{outfile}.
2567 @cindex controlling terminal
2568 Another way to specify where your program should do input and output is
2569 with the @code{tty} command. This command accepts a file name as
2570 argument, and causes this file to be the default for future @code{run}
2571 commands. It also resets the controlling terminal for the child
2572 process, for future @code{run} commands. For example,
2579 directs that processes started with subsequent @code{run} commands
2580 default to do input and output on the terminal @file{/dev/ttyb} and have
2581 that as their controlling terminal.
2583 An explicit redirection in @code{run} overrides the @code{tty} command's
2584 effect on the input/output device, but not its effect on the controlling
2587 When you use the @code{tty} command or redirect input in the @code{run}
2588 command, only the input @emph{for your program} is affected. The input
2589 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2590 for @code{set inferior-tty}.
2592 @cindex inferior tty
2593 @cindex set inferior controlling terminal
2594 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2595 display the name of the terminal that will be used for future runs of your
2599 @item set inferior-tty [ @var{tty} ]
2600 @kindex set inferior-tty
2601 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2602 restores the default behavior, which is to use the same terminal as
2605 @item show inferior-tty
2606 @kindex show inferior-tty
2607 Show the current tty for the program being debugged.
2611 @section Debugging an Already-running Process
2616 @item attach @var{process-id}
2617 This command attaches to a running process---one that was started
2618 outside @value{GDBN}. (@code{info files} shows your active
2619 targets.) The command takes as argument a process ID. The usual way to
2620 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2621 or with the @samp{jobs -l} shell command.
2623 @code{attach} does not repeat if you press @key{RET} a second time after
2624 executing the command.
2627 To use @code{attach}, your program must be running in an environment
2628 which supports processes; for example, @code{attach} does not work for
2629 programs on bare-board targets that lack an operating system. You must
2630 also have permission to send the process a signal.
2632 When you use @code{attach}, the debugger finds the program running in
2633 the process first by looking in the current working directory, then (if
2634 the program is not found) by using the source file search path
2635 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2636 the @code{file} command to load the program. @xref{Files, ,Commands to
2639 The first thing @value{GDBN} does after arranging to debug the specified
2640 process is to stop it. You can examine and modify an attached process
2641 with all the @value{GDBN} commands that are ordinarily available when
2642 you start processes with @code{run}. You can insert breakpoints; you
2643 can step and continue; you can modify storage. If you would rather the
2644 process continue running, you may use the @code{continue} command after
2645 attaching @value{GDBN} to the process.
2650 When you have finished debugging the attached process, you can use the
2651 @code{detach} command to release it from @value{GDBN} control. Detaching
2652 the process continues its execution. After the @code{detach} command,
2653 that process and @value{GDBN} become completely independent once more, and you
2654 are ready to @code{attach} another process or start one with @code{run}.
2655 @code{detach} does not repeat if you press @key{RET} again after
2656 executing the command.
2659 If you exit @value{GDBN} while you have an attached process, you detach
2660 that process. If you use the @code{run} command, you kill that process.
2661 By default, @value{GDBN} asks for confirmation if you try to do either of these
2662 things; you can control whether or not you need to confirm by using the
2663 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2667 @section Killing the Child Process
2672 Kill the child process in which your program is running under @value{GDBN}.
2675 This command is useful if you wish to debug a core dump instead of a
2676 running process. @value{GDBN} ignores any core dump file while your program
2679 On some operating systems, a program cannot be executed outside @value{GDBN}
2680 while you have breakpoints set on it inside @value{GDBN}. You can use the
2681 @code{kill} command in this situation to permit running your program
2682 outside the debugger.
2684 The @code{kill} command is also useful if you wish to recompile and
2685 relink your program, since on many systems it is impossible to modify an
2686 executable file while it is running in a process. In this case, when you
2687 next type @code{run}, @value{GDBN} notices that the file has changed, and
2688 reads the symbol table again (while trying to preserve your current
2689 breakpoint settings).
2691 @node Inferiors and Programs
2692 @section Debugging Multiple Inferiors and Programs
2694 @value{GDBN} lets you run and debug multiple programs in a single
2695 session. In addition, @value{GDBN} on some systems may let you run
2696 several programs simultaneously (otherwise you have to exit from one
2697 before starting another). In the most general case, you can have
2698 multiple threads of execution in each of multiple processes, launched
2699 from multiple executables.
2702 @value{GDBN} represents the state of each program execution with an
2703 object called an @dfn{inferior}. An inferior typically corresponds to
2704 a process, but is more general and applies also to targets that do not
2705 have processes. Inferiors may be created before a process runs, and
2706 may be retained after a process exits. Inferiors have unique
2707 identifiers that are different from process ids. Usually each
2708 inferior will also have its own distinct address space, although some
2709 embedded targets may have several inferiors running in different parts
2710 of a single address space. Each inferior may in turn have multiple
2711 threads running in it.
2713 To find out what inferiors exist at any moment, use @w{@code{info
2717 @kindex info inferiors [ @var{id}@dots{} ]
2718 @item info inferiors
2719 Print a list of all inferiors currently being managed by @value{GDBN}.
2720 By default all inferiors are printed, but the argument @var{id}@dots{}
2721 -- a space separated list of inferior numbers -- can be used to limit
2722 the display to just the requested inferiors.
2724 @value{GDBN} displays for each inferior (in this order):
2728 the inferior number assigned by @value{GDBN}
2731 the target system's inferior identifier
2734 the name of the executable the inferior is running.
2739 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2740 indicates the current inferior.
2744 @c end table here to get a little more width for example
2747 (@value{GDBP}) info inferiors
2748 Num Description Executable
2749 2 process 2307 hello
2750 * 1 process 3401 goodbye
2753 To switch focus between inferiors, use the @code{inferior} command:
2756 @kindex inferior @var{infno}
2757 @item inferior @var{infno}
2758 Make inferior number @var{infno} the current inferior. The argument
2759 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2760 in the first field of the @samp{info inferiors} display.
2763 @vindex $_inferior@r{, convenience variable}
2764 The debugger convenience variable @samp{$_inferior} contains the
2765 number of the current inferior. You may find this useful in writing
2766 breakpoint conditional expressions, command scripts, and so forth.
2767 @xref{Convenience Vars,, Convenience Variables}, for general
2768 information on convenience variables.
2770 You can get multiple executables into a debugging session via the
2771 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2772 systems @value{GDBN} can add inferiors to the debug session
2773 automatically by following calls to @code{fork} and @code{exec}. To
2774 remove inferiors from the debugging session use the
2775 @w{@code{remove-inferiors}} command.
2778 @kindex add-inferior
2779 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2780 Adds @var{n} inferiors to be run using @var{executable} as the
2781 executable; @var{n} defaults to 1. If no executable is specified,
2782 the inferiors begins empty, with no program. You can still assign or
2783 change the program assigned to the inferior at any time by using the
2784 @code{file} command with the executable name as its argument.
2786 @kindex clone-inferior
2787 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2788 Adds @var{n} inferiors ready to execute the same program as inferior
2789 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2790 number of the current inferior. This is a convenient command when you
2791 want to run another instance of the inferior you are debugging.
2794 (@value{GDBP}) info inferiors
2795 Num Description Executable
2796 * 1 process 29964 helloworld
2797 (@value{GDBP}) clone-inferior
2800 (@value{GDBP}) info inferiors
2801 Num Description Executable
2803 * 1 process 29964 helloworld
2806 You can now simply switch focus to inferior 2 and run it.
2808 @kindex remove-inferiors
2809 @item remove-inferiors @var{infno}@dots{}
2810 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2811 possible to remove an inferior that is running with this command. For
2812 those, use the @code{kill} or @code{detach} command first.
2816 To quit debugging one of the running inferiors that is not the current
2817 inferior, you can either detach from it by using the @w{@code{detach
2818 inferior}} command (allowing it to run independently), or kill it
2819 using the @w{@code{kill inferiors}} command:
2822 @kindex detach inferiors @var{infno}@dots{}
2823 @item detach inferior @var{infno}@dots{}
2824 Detach from the inferior or inferiors identified by @value{GDBN}
2825 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2826 still stays on the list of inferiors shown by @code{info inferiors},
2827 but its Description will show @samp{<null>}.
2829 @kindex kill inferiors @var{infno}@dots{}
2830 @item kill inferiors @var{infno}@dots{}
2831 Kill the inferior or inferiors identified by @value{GDBN} inferior
2832 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2833 stays on the list of inferiors shown by @code{info inferiors}, but its
2834 Description will show @samp{<null>}.
2837 After the successful completion of a command such as @code{detach},
2838 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2839 a normal process exit, the inferior is still valid and listed with
2840 @code{info inferiors}, ready to be restarted.
2843 To be notified when inferiors are started or exit under @value{GDBN}'s
2844 control use @w{@code{set print inferior-events}}:
2847 @kindex set print inferior-events
2848 @cindex print messages on inferior start and exit
2849 @item set print inferior-events
2850 @itemx set print inferior-events on
2851 @itemx set print inferior-events off
2852 The @code{set print inferior-events} command allows you to enable or
2853 disable printing of messages when @value{GDBN} notices that new
2854 inferiors have started or that inferiors have exited or have been
2855 detached. By default, these messages will not be printed.
2857 @kindex show print inferior-events
2858 @item show print inferior-events
2859 Show whether messages will be printed when @value{GDBN} detects that
2860 inferiors have started, exited or have been detached.
2863 Many commands will work the same with multiple programs as with a
2864 single program: e.g., @code{print myglobal} will simply display the
2865 value of @code{myglobal} in the current inferior.
2868 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2869 get more info about the relationship of inferiors, programs, address
2870 spaces in a debug session. You can do that with the @w{@code{maint
2871 info program-spaces}} command.
2874 @kindex maint info program-spaces
2875 @item maint info program-spaces
2876 Print a list of all program spaces currently being managed by
2879 @value{GDBN} displays for each program space (in this order):
2883 the program space number assigned by @value{GDBN}
2886 the name of the executable loaded into the program space, with e.g.,
2887 the @code{file} command.
2892 An asterisk @samp{*} preceding the @value{GDBN} program space number
2893 indicates the current program space.
2895 In addition, below each program space line, @value{GDBN} prints extra
2896 information that isn't suitable to display in tabular form. For
2897 example, the list of inferiors bound to the program space.
2900 (@value{GDBP}) maint info program-spaces
2904 Bound inferiors: ID 1 (process 21561)
2907 Here we can see that no inferior is running the program @code{hello},
2908 while @code{process 21561} is running the program @code{goodbye}. On
2909 some targets, it is possible that multiple inferiors are bound to the
2910 same program space. The most common example is that of debugging both
2911 the parent and child processes of a @code{vfork} call. For example,
2914 (@value{GDBP}) maint info program-spaces
2917 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2920 Here, both inferior 2 and inferior 1 are running in the same program
2921 space as a result of inferior 1 having executed a @code{vfork} call.
2925 @section Debugging Programs with Multiple Threads
2927 @cindex threads of execution
2928 @cindex multiple threads
2929 @cindex switching threads
2930 In some operating systems, such as GNU/Linux and Solaris, a single program
2931 may have more than one @dfn{thread} of execution. The precise semantics
2932 of threads differ from one operating system to another, but in general
2933 the threads of a single program are akin to multiple processes---except
2934 that they share one address space (that is, they can all examine and
2935 modify the same variables). On the other hand, each thread has its own
2936 registers and execution stack, and perhaps private memory.
2938 @value{GDBN} provides these facilities for debugging multi-thread
2942 @item automatic notification of new threads
2943 @item @samp{thread @var{thread-id}}, a command to switch among threads
2944 @item @samp{info threads}, a command to inquire about existing threads
2945 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
2946 a command to apply a command to a list of threads
2947 @item thread-specific breakpoints
2948 @item @samp{set print thread-events}, which controls printing of
2949 messages on thread start and exit.
2950 @item @samp{set libthread-db-search-path @var{path}}, which lets
2951 the user specify which @code{libthread_db} to use if the default choice
2952 isn't compatible with the program.
2955 @cindex focus of debugging
2956 @cindex current thread
2957 The @value{GDBN} thread debugging facility allows you to observe all
2958 threads while your program runs---but whenever @value{GDBN} takes
2959 control, one thread in particular is always the focus of debugging.
2960 This thread is called the @dfn{current thread}. Debugging commands show
2961 program information from the perspective of the current thread.
2963 @cindex @code{New} @var{systag} message
2964 @cindex thread identifier (system)
2965 @c FIXME-implementors!! It would be more helpful if the [New...] message
2966 @c included GDB's numeric thread handle, so you could just go to that
2967 @c thread without first checking `info threads'.
2968 Whenever @value{GDBN} detects a new thread in your program, it displays
2969 the target system's identification for the thread with a message in the
2970 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2971 whose form varies depending on the particular system. For example, on
2972 @sc{gnu}/Linux, you might see
2975 [New Thread 0x41e02940 (LWP 25582)]
2979 when @value{GDBN} notices a new thread. In contrast, on other systems,
2980 the @var{systag} is simply something like @samp{process 368}, with no
2983 @c FIXME!! (1) Does the [New...] message appear even for the very first
2984 @c thread of a program, or does it only appear for the
2985 @c second---i.e.@: when it becomes obvious we have a multithread
2987 @c (2) *Is* there necessarily a first thread always? Or do some
2988 @c multithread systems permit starting a program with multiple
2989 @c threads ab initio?
2991 @anchor{thread numbers}
2992 @cindex thread number, per inferior
2993 @cindex thread identifier (GDB)
2994 For debugging purposes, @value{GDBN} associates its own thread number
2995 ---always a single integer---with each thread of an inferior. This
2996 number is unique between all threads of an inferior, but not unique
2997 between threads of different inferiors.
2999 @cindex qualified thread ID
3000 You can refer to a given thread in an inferior using the qualified
3001 @var{inferior-num}.@var{thread-num} syntax, also known as
3002 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3003 number and @var{thread-num} being the thread number of the given
3004 inferior. For example, thread @code{2.3} refers to thread number 3 of
3005 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3006 then @value{GDBN} infers you're referring to a thread of the current
3009 Until you create a second inferior, @value{GDBN} does not show the
3010 @var{inferior-num} part of thread IDs, even though you can always use
3011 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3012 of inferior 1, the initial inferior.
3014 @anchor{thread ID lists}
3015 @cindex thread ID lists
3016 Some commands accept a space-separated @dfn{thread ID list} as
3017 argument. A list element can be:
3021 A thread ID as shown in the first field of the @samp{info threads}
3022 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3026 A range of thread numbers, again with or without an inferior
3027 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3028 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3031 All threads of an inferior, specified with a star wildcard, with or
3032 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3033 @samp{1.*}) or @code{*}. The former refers to all threads of the
3034 given inferior, and the latter form without an inferior qualifier
3035 refers to all threads of the current inferior.
3039 For example, if the current inferior is 1, and inferior 7 has one
3040 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3041 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3042 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3043 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3047 @anchor{global thread numbers}
3048 @cindex global thread number
3049 @cindex global thread identifier (GDB)
3050 In addition to a @emph{per-inferior} number, each thread is also
3051 assigned a unique @emph{global} number, also known as @dfn{global
3052 thread ID}, a single integer. Unlike the thread number component of
3053 the thread ID, no two threads have the same global ID, even when
3054 you're debugging multiple inferiors.
3056 From @value{GDBN}'s perspective, a process always has at least one
3057 thread. In other words, @value{GDBN} assigns a thread number to the
3058 program's ``main thread'' even if the program is not multi-threaded.
3060 @vindex $_thread@r{, convenience variable}
3061 @vindex $_gthread@r{, convenience variable}
3062 The debugger convenience variables @samp{$_thread} and
3063 @samp{$_gthread} contain, respectively, the per-inferior thread number
3064 and the global thread number of the current thread. You may find this
3065 useful in writing breakpoint conditional expressions, command scripts,
3066 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3067 general information on convenience variables.
3069 If @value{GDBN} detects the program is multi-threaded, it augments the
3070 usual message about stopping at a breakpoint with the ID and name of
3071 the thread that hit the breakpoint.
3074 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3077 Likewise when the program receives a signal:
3080 Thread 1 "main" received signal SIGINT, Interrupt.
3084 @kindex info threads
3085 @item info threads @r{[}@var{thread-id-list}@r{]}
3087 Display information about one or more threads. With no arguments
3088 displays information about all threads. You can specify the list of
3089 threads that you want to display using the thread ID list syntax
3090 (@pxref{thread ID lists}).
3092 @value{GDBN} displays for each thread (in this order):
3096 the per-inferior thread number assigned by @value{GDBN}
3099 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3100 option was specified
3103 the target system's thread identifier (@var{systag})
3106 the thread's name, if one is known. A thread can either be named by
3107 the user (see @code{thread name}, below), or, in some cases, by the
3111 the current stack frame summary for that thread
3115 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3116 indicates the current thread.
3120 @c end table here to get a little more width for example
3123 (@value{GDBP}) info threads
3125 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3126 2 process 35 thread 23 0x34e5 in sigpause ()
3127 3 process 35 thread 27 0x34e5 in sigpause ()
3131 If you're debugging multiple inferiors, @value{GDBN} displays thread
3132 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3133 Otherwise, only @var{thread-num} is shown.
3135 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3136 indicating each thread's global thread ID:
3139 (@value{GDBP}) info threads
3140 Id GId Target Id Frame
3141 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3142 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3143 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3144 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3147 On Solaris, you can display more information about user threads with a
3148 Solaris-specific command:
3151 @item maint info sol-threads
3152 @kindex maint info sol-threads
3153 @cindex thread info (Solaris)
3154 Display info on Solaris user threads.
3158 @kindex thread @var{thread-id}
3159 @item thread @var{thread-id}
3160 Make thread ID @var{thread-id} the current thread. The command
3161 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3162 the first field of the @samp{info threads} display, with or without an
3163 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3165 @value{GDBN} responds by displaying the system identifier of the
3166 thread you selected, and its current stack frame summary:
3169 (@value{GDBP}) thread 2
3170 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3171 #0 some_function (ignore=0x0) at example.c:8
3172 8 printf ("hello\n");
3176 As with the @samp{[New @dots{}]} message, the form of the text after
3177 @samp{Switching to} depends on your system's conventions for identifying
3180 @kindex thread apply
3181 @cindex apply command to several threads
3182 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3183 The @code{thread apply} command allows you to apply the named
3184 @var{command} to one or more threads. Specify the threads that you
3185 want affected using the thread ID list syntax (@pxref{thread ID
3186 lists}), or specify @code{all} to apply to all threads. To apply a
3187 command to all threads in descending order, type @kbd{thread apply all
3188 @var{command}}. To apply a command to all threads in ascending order,
3189 type @kbd{thread apply all -ascending @var{command}}.
3191 The @var{flag} arguments control what output to produce and how to handle
3192 errors raised when applying @var{command} to a thread. @var{flag}
3193 must start with a @code{-} directly followed by one letter in
3194 @code{qcs}. If several flags are provided, they must be given
3195 individually, such as @code{-c -q}.
3197 By default, @value{GDBN} displays some thread information before the
3198 output produced by @var{command}, and an error raised during the
3199 execution of a @var{command} will abort @code{thread apply}. The
3200 following flags can be used to fine-tune this behavior:
3204 The flag @code{-c}, which stands for @samp{continue}, causes any
3205 errors in @var{command} to be displayed, and the execution of
3206 @code{thread apply} then continues.
3208 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3209 or empty output produced by a @var{command} to be silently ignored.
3210 That is, the execution continues, but the thread information and errors
3213 The flag @code{-q} (@samp{quiet}) disables printing the thread
3217 Flags @code{-c} and @code{-s} cannot be used together.
3220 @cindex apply command to all threads (ignoring errors and empty output)
3221 @item taas @var{command}
3222 Shortcut for @code{thread apply all -s @var{command}}.
3223 Applies @var{command} on all threads, ignoring errors and empty output.
3226 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3227 @item tfaas @var{command}
3228 Shortcut for @code{thread apply all -s frame apply all -s @var{command}}.
3229 Applies @var{command} on all frames of all threads, ignoring errors
3230 and empty output. Note that the flag @code{-s} is specified twice:
3231 The first @code{-s} ensures that @code{thread apply} only shows the thread
3232 information of the threads for which @code{frame apply} produces
3233 some output. The second @code{-s} is needed to ensure that @code{frame
3234 apply} shows the frame information of a frame only if the
3235 @var{command} successfully produced some output.
3237 It can for example be used to print a local variable or a function
3238 argument without knowing the thread or frame where this variable or argument
3241 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3246 @cindex name a thread
3247 @item thread name [@var{name}]
3248 This command assigns a name to the current thread. If no argument is
3249 given, any existing user-specified name is removed. The thread name
3250 appears in the @samp{info threads} display.
3252 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3253 determine the name of the thread as given by the OS. On these
3254 systems, a name specified with @samp{thread name} will override the
3255 system-give name, and removing the user-specified name will cause
3256 @value{GDBN} to once again display the system-specified name.
3259 @cindex search for a thread
3260 @item thread find [@var{regexp}]
3261 Search for and display thread ids whose name or @var{systag}
3262 matches the supplied regular expression.
3264 As well as being the complement to the @samp{thread name} command,
3265 this command also allows you to identify a thread by its target
3266 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3270 (@value{GDBN}) thread find 26688
3271 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3272 (@value{GDBN}) info thread 4
3274 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3277 @kindex set print thread-events
3278 @cindex print messages on thread start and exit
3279 @item set print thread-events
3280 @itemx set print thread-events on
3281 @itemx set print thread-events off
3282 The @code{set print thread-events} command allows you to enable or
3283 disable printing of messages when @value{GDBN} notices that new threads have
3284 started or that threads have exited. By default, these messages will
3285 be printed if detection of these events is supported by the target.
3286 Note that these messages cannot be disabled on all targets.
3288 @kindex show print thread-events
3289 @item show print thread-events
3290 Show whether messages will be printed when @value{GDBN} detects that threads
3291 have started and exited.
3294 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3295 more information about how @value{GDBN} behaves when you stop and start
3296 programs with multiple threads.
3298 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3299 watchpoints in programs with multiple threads.
3301 @anchor{set libthread-db-search-path}
3303 @kindex set libthread-db-search-path
3304 @cindex search path for @code{libthread_db}
3305 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3306 If this variable is set, @var{path} is a colon-separated list of
3307 directories @value{GDBN} will use to search for @code{libthread_db}.
3308 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3309 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3310 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3313 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3314 @code{libthread_db} library to obtain information about threads in the
3315 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3316 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3317 specific thread debugging library loading is enabled
3318 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3320 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3321 refers to the default system directories that are
3322 normally searched for loading shared libraries. The @samp{$sdir} entry
3323 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3324 (@pxref{libthread_db.so.1 file}).
3326 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3327 refers to the directory from which @code{libpthread}
3328 was loaded in the inferior process.
3330 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3331 @value{GDBN} attempts to initialize it with the current inferior process.
3332 If this initialization fails (which could happen because of a version
3333 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3334 will unload @code{libthread_db}, and continue with the next directory.
3335 If none of @code{libthread_db} libraries initialize successfully,
3336 @value{GDBN} will issue a warning and thread debugging will be disabled.
3338 Setting @code{libthread-db-search-path} is currently implemented
3339 only on some platforms.
3341 @kindex show libthread-db-search-path
3342 @item show libthread-db-search-path
3343 Display current libthread_db search path.
3345 @kindex set debug libthread-db
3346 @kindex show debug libthread-db
3347 @cindex debugging @code{libthread_db}
3348 @item set debug libthread-db
3349 @itemx show debug libthread-db
3350 Turns on or off display of @code{libthread_db}-related events.
3351 Use @code{1} to enable, @code{0} to disable.
3355 @section Debugging Forks
3357 @cindex fork, debugging programs which call
3358 @cindex multiple processes
3359 @cindex processes, multiple
3360 On most systems, @value{GDBN} has no special support for debugging
3361 programs which create additional processes using the @code{fork}
3362 function. When a program forks, @value{GDBN} will continue to debug the
3363 parent process and the child process will run unimpeded. If you have
3364 set a breakpoint in any code which the child then executes, the child
3365 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3366 will cause it to terminate.
3368 However, if you want to debug the child process there is a workaround
3369 which isn't too painful. Put a call to @code{sleep} in the code which
3370 the child process executes after the fork. It may be useful to sleep
3371 only if a certain environment variable is set, or a certain file exists,
3372 so that the delay need not occur when you don't want to run @value{GDBN}
3373 on the child. While the child is sleeping, use the @code{ps} program to
3374 get its process ID. Then tell @value{GDBN} (a new invocation of
3375 @value{GDBN} if you are also debugging the parent process) to attach to
3376 the child process (@pxref{Attach}). From that point on you can debug
3377 the child process just like any other process which you attached to.
3379 On some systems, @value{GDBN} provides support for debugging programs
3380 that create additional processes using the @code{fork} or @code{vfork}
3381 functions. On @sc{gnu}/Linux platforms, this feature is supported
3382 with kernel version 2.5.46 and later.
3384 The fork debugging commands are supported in native mode and when
3385 connected to @code{gdbserver} in either @code{target remote} mode or
3386 @code{target extended-remote} mode.
3388 By default, when a program forks, @value{GDBN} will continue to debug
3389 the parent process and the child process will run unimpeded.
3391 If you want to follow the child process instead of the parent process,
3392 use the command @w{@code{set follow-fork-mode}}.
3395 @kindex set follow-fork-mode
3396 @item set follow-fork-mode @var{mode}
3397 Set the debugger response to a program call of @code{fork} or
3398 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3399 process. The @var{mode} argument can be:
3403 The original process is debugged after a fork. The child process runs
3404 unimpeded. This is the default.
3407 The new process is debugged after a fork. The parent process runs
3412 @kindex show follow-fork-mode
3413 @item show follow-fork-mode
3414 Display the current debugger response to a @code{fork} or @code{vfork} call.
3417 @cindex debugging multiple processes
3418 On Linux, if you want to debug both the parent and child processes, use the
3419 command @w{@code{set detach-on-fork}}.
3422 @kindex set detach-on-fork
3423 @item set detach-on-fork @var{mode}
3424 Tells gdb whether to detach one of the processes after a fork, or
3425 retain debugger control over them both.
3429 The child process (or parent process, depending on the value of
3430 @code{follow-fork-mode}) will be detached and allowed to run
3431 independently. This is the default.
3434 Both processes will be held under the control of @value{GDBN}.
3435 One process (child or parent, depending on the value of
3436 @code{follow-fork-mode}) is debugged as usual, while the other
3441 @kindex show detach-on-fork
3442 @item show detach-on-fork
3443 Show whether detach-on-fork mode is on/off.
3446 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3447 will retain control of all forked processes (including nested forks).
3448 You can list the forked processes under the control of @value{GDBN} by
3449 using the @w{@code{info inferiors}} command, and switch from one fork
3450 to another by using the @code{inferior} command (@pxref{Inferiors and
3451 Programs, ,Debugging Multiple Inferiors and Programs}).
3453 To quit debugging one of the forked processes, you can either detach
3454 from it by using the @w{@code{detach inferiors}} command (allowing it
3455 to run independently), or kill it using the @w{@code{kill inferiors}}
3456 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3459 If you ask to debug a child process and a @code{vfork} is followed by an
3460 @code{exec}, @value{GDBN} executes the new target up to the first
3461 breakpoint in the new target. If you have a breakpoint set on
3462 @code{main} in your original program, the breakpoint will also be set on
3463 the child process's @code{main}.
3465 On some systems, when a child process is spawned by @code{vfork}, you
3466 cannot debug the child or parent until an @code{exec} call completes.
3468 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3469 call executes, the new target restarts. To restart the parent
3470 process, use the @code{file} command with the parent executable name
3471 as its argument. By default, after an @code{exec} call executes,
3472 @value{GDBN} discards the symbols of the previous executable image.
3473 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3477 @kindex set follow-exec-mode
3478 @item set follow-exec-mode @var{mode}
3480 Set debugger response to a program call of @code{exec}. An
3481 @code{exec} call replaces the program image of a process.
3483 @code{follow-exec-mode} can be:
3487 @value{GDBN} creates a new inferior and rebinds the process to this
3488 new inferior. The program the process was running before the
3489 @code{exec} call can be restarted afterwards by restarting the
3495 (@value{GDBP}) info inferiors
3497 Id Description Executable
3500 process 12020 is executing new program: prog2
3501 Program exited normally.
3502 (@value{GDBP}) info inferiors
3503 Id Description Executable
3509 @value{GDBN} keeps the process bound to the same inferior. The new
3510 executable image replaces the previous executable loaded in the
3511 inferior. Restarting the inferior after the @code{exec} call, with
3512 e.g., the @code{run} command, restarts the executable the process was
3513 running after the @code{exec} call. This is the default mode.
3518 (@value{GDBP}) info inferiors
3519 Id Description Executable
3522 process 12020 is executing new program: prog2
3523 Program exited normally.
3524 (@value{GDBP}) info inferiors
3525 Id Description Executable
3532 @code{follow-exec-mode} is supported in native mode and
3533 @code{target extended-remote} mode.
3535 You can use the @code{catch} command to make @value{GDBN} stop whenever
3536 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3537 Catchpoints, ,Setting Catchpoints}.
3539 @node Checkpoint/Restart
3540 @section Setting a @emph{Bookmark} to Return to Later
3545 @cindex snapshot of a process
3546 @cindex rewind program state
3548 On certain operating systems@footnote{Currently, only
3549 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3550 program's state, called a @dfn{checkpoint}, and come back to it
3553 Returning to a checkpoint effectively undoes everything that has
3554 happened in the program since the @code{checkpoint} was saved. This
3555 includes changes in memory, registers, and even (within some limits)
3556 system state. Effectively, it is like going back in time to the
3557 moment when the checkpoint was saved.
3559 Thus, if you're stepping thru a program and you think you're
3560 getting close to the point where things go wrong, you can save
3561 a checkpoint. Then, if you accidentally go too far and miss
3562 the critical statement, instead of having to restart your program
3563 from the beginning, you can just go back to the checkpoint and
3564 start again from there.
3566 This can be especially useful if it takes a lot of time or
3567 steps to reach the point where you think the bug occurs.
3569 To use the @code{checkpoint}/@code{restart} method of debugging:
3574 Save a snapshot of the debugged program's current execution state.
3575 The @code{checkpoint} command takes no arguments, but each checkpoint
3576 is assigned a small integer id, similar to a breakpoint id.
3578 @kindex info checkpoints
3579 @item info checkpoints
3580 List the checkpoints that have been saved in the current debugging
3581 session. For each checkpoint, the following information will be
3588 @item Source line, or label
3591 @kindex restart @var{checkpoint-id}
3592 @item restart @var{checkpoint-id}
3593 Restore the program state that was saved as checkpoint number
3594 @var{checkpoint-id}. All program variables, registers, stack frames
3595 etc.@: will be returned to the values that they had when the checkpoint
3596 was saved. In essence, gdb will ``wind back the clock'' to the point
3597 in time when the checkpoint was saved.
3599 Note that breakpoints, @value{GDBN} variables, command history etc.
3600 are not affected by restoring a checkpoint. In general, a checkpoint
3601 only restores things that reside in the program being debugged, not in
3604 @kindex delete checkpoint @var{checkpoint-id}
3605 @item delete checkpoint @var{checkpoint-id}
3606 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3610 Returning to a previously saved checkpoint will restore the user state
3611 of the program being debugged, plus a significant subset of the system
3612 (OS) state, including file pointers. It won't ``un-write'' data from
3613 a file, but it will rewind the file pointer to the previous location,
3614 so that the previously written data can be overwritten. For files
3615 opened in read mode, the pointer will also be restored so that the
3616 previously read data can be read again.
3618 Of course, characters that have been sent to a printer (or other
3619 external device) cannot be ``snatched back'', and characters received
3620 from eg.@: a serial device can be removed from internal program buffers,
3621 but they cannot be ``pushed back'' into the serial pipeline, ready to
3622 be received again. Similarly, the actual contents of files that have
3623 been changed cannot be restored (at this time).
3625 However, within those constraints, you actually can ``rewind'' your
3626 program to a previously saved point in time, and begin debugging it
3627 again --- and you can change the course of events so as to debug a
3628 different execution path this time.
3630 @cindex checkpoints and process id
3631 Finally, there is one bit of internal program state that will be
3632 different when you return to a checkpoint --- the program's process
3633 id. Each checkpoint will have a unique process id (or @var{pid}),
3634 and each will be different from the program's original @var{pid}.
3635 If your program has saved a local copy of its process id, this could
3636 potentially pose a problem.
3638 @subsection A Non-obvious Benefit of Using Checkpoints
3640 On some systems such as @sc{gnu}/Linux, address space randomization
3641 is performed on new processes for security reasons. This makes it
3642 difficult or impossible to set a breakpoint, or watchpoint, on an
3643 absolute address if you have to restart the program, since the
3644 absolute location of a symbol will change from one execution to the
3647 A checkpoint, however, is an @emph{identical} copy of a process.
3648 Therefore if you create a checkpoint at (eg.@:) the start of main,
3649 and simply return to that checkpoint instead of restarting the
3650 process, you can avoid the effects of address randomization and
3651 your symbols will all stay in the same place.
3654 @chapter Stopping and Continuing
3656 The principal purposes of using a debugger are so that you can stop your
3657 program before it terminates; or so that, if your program runs into
3658 trouble, you can investigate and find out why.
3660 Inside @value{GDBN}, your program may stop for any of several reasons,
3661 such as a signal, a breakpoint, or reaching a new line after a
3662 @value{GDBN} command such as @code{step}. You may then examine and
3663 change variables, set new breakpoints or remove old ones, and then
3664 continue execution. Usually, the messages shown by @value{GDBN} provide
3665 ample explanation of the status of your program---but you can also
3666 explicitly request this information at any time.
3669 @kindex info program
3671 Display information about the status of your program: whether it is
3672 running or not, what process it is, and why it stopped.
3676 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3677 * Continuing and Stepping:: Resuming execution
3678 * Skipping Over Functions and Files::
3679 Skipping over functions and files
3681 * Thread Stops:: Stopping and starting multi-thread programs
3685 @section Breakpoints, Watchpoints, and Catchpoints
3688 A @dfn{breakpoint} makes your program stop whenever a certain point in
3689 the program is reached. For each breakpoint, you can add conditions to
3690 control in finer detail whether your program stops. You can set
3691 breakpoints with the @code{break} command and its variants (@pxref{Set
3692 Breaks, ,Setting Breakpoints}), to specify the place where your program
3693 should stop by line number, function name or exact address in the
3696 On some systems, you can set breakpoints in shared libraries before
3697 the executable is run.
3700 @cindex data breakpoints
3701 @cindex memory tracing
3702 @cindex breakpoint on memory address
3703 @cindex breakpoint on variable modification
3704 A @dfn{watchpoint} is a special breakpoint that stops your program
3705 when the value of an expression changes. The expression may be a value
3706 of a variable, or it could involve values of one or more variables
3707 combined by operators, such as @samp{a + b}. This is sometimes called
3708 @dfn{data breakpoints}. You must use a different command to set
3709 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3710 from that, you can manage a watchpoint like any other breakpoint: you
3711 enable, disable, and delete both breakpoints and watchpoints using the
3714 You can arrange to have values from your program displayed automatically
3715 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3719 @cindex breakpoint on events
3720 A @dfn{catchpoint} is another special breakpoint that stops your program
3721 when a certain kind of event occurs, such as the throwing of a C@t{++}
3722 exception or the loading of a library. As with watchpoints, you use a
3723 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3724 Catchpoints}), but aside from that, you can manage a catchpoint like any
3725 other breakpoint. (To stop when your program receives a signal, use the
3726 @code{handle} command; see @ref{Signals, ,Signals}.)
3728 @cindex breakpoint numbers
3729 @cindex numbers for breakpoints
3730 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3731 catchpoint when you create it; these numbers are successive integers
3732 starting with one. In many of the commands for controlling various
3733 features of breakpoints you use the breakpoint number to say which
3734 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3735 @dfn{disabled}; if disabled, it has no effect on your program until you
3738 @cindex breakpoint ranges
3739 @cindex breakpoint lists
3740 @cindex ranges of breakpoints
3741 @cindex lists of breakpoints
3742 Some @value{GDBN} commands accept a space-separated list of breakpoints
3743 on which to operate. A list element can be either a single breakpoint number,
3744 like @samp{5}, or a range of such numbers, like @samp{5-7}.
3745 When a breakpoint list is given to a command, all breakpoints in that list
3749 * Set Breaks:: Setting breakpoints
3750 * Set Watchpoints:: Setting watchpoints
3751 * Set Catchpoints:: Setting catchpoints
3752 * Delete Breaks:: Deleting breakpoints
3753 * Disabling:: Disabling breakpoints
3754 * Conditions:: Break conditions
3755 * Break Commands:: Breakpoint command lists
3756 * Dynamic Printf:: Dynamic printf
3757 * Save Breakpoints:: How to save breakpoints in a file
3758 * Static Probe Points:: Listing static probe points
3759 * Error in Breakpoints:: ``Cannot insert breakpoints''
3760 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3764 @subsection Setting Breakpoints
3766 @c FIXME LMB what does GDB do if no code on line of breakpt?
3767 @c consider in particular declaration with/without initialization.
3769 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3772 @kindex b @r{(@code{break})}
3773 @vindex $bpnum@r{, convenience variable}
3774 @cindex latest breakpoint
3775 Breakpoints are set with the @code{break} command (abbreviated
3776 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3777 number of the breakpoint you've set most recently; see @ref{Convenience
3778 Vars,, Convenience Variables}, for a discussion of what you can do with
3779 convenience variables.
3782 @item break @var{location}
3783 Set a breakpoint at the given @var{location}, which can specify a
3784 function name, a line number, or an address of an instruction.
3785 (@xref{Specify Location}, for a list of all the possible ways to
3786 specify a @var{location}.) The breakpoint will stop your program just
3787 before it executes any of the code in the specified @var{location}.
3789 When using source languages that permit overloading of symbols, such as
3790 C@t{++}, a function name may refer to more than one possible place to break.
3791 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3794 It is also possible to insert a breakpoint that will stop the program
3795 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3796 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3799 When called without any arguments, @code{break} sets a breakpoint at
3800 the next instruction to be executed in the selected stack frame
3801 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3802 innermost, this makes your program stop as soon as control
3803 returns to that frame. This is similar to the effect of a
3804 @code{finish} command in the frame inside the selected frame---except
3805 that @code{finish} does not leave an active breakpoint. If you use
3806 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3807 the next time it reaches the current location; this may be useful
3810 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3811 least one instruction has been executed. If it did not do this, you
3812 would be unable to proceed past a breakpoint without first disabling the
3813 breakpoint. This rule applies whether or not the breakpoint already
3814 existed when your program stopped.
3816 @item break @dots{} if @var{cond}
3817 Set a breakpoint with condition @var{cond}; evaluate the expression
3818 @var{cond} each time the breakpoint is reached, and stop only if the
3819 value is nonzero---that is, if @var{cond} evaluates as true.
3820 @samp{@dots{}} stands for one of the possible arguments described
3821 above (or no argument) specifying where to break. @xref{Conditions,
3822 ,Break Conditions}, for more information on breakpoint conditions.
3825 @item tbreak @var{args}
3826 Set a breakpoint enabled only for one stop. The @var{args} are the
3827 same as for the @code{break} command, and the breakpoint is set in the same
3828 way, but the breakpoint is automatically deleted after the first time your
3829 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3832 @cindex hardware breakpoints
3833 @item hbreak @var{args}
3834 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3835 @code{break} command and the breakpoint is set in the same way, but the
3836 breakpoint requires hardware support and some target hardware may not
3837 have this support. The main purpose of this is EPROM/ROM code
3838 debugging, so you can set a breakpoint at an instruction without
3839 changing the instruction. This can be used with the new trap-generation
3840 provided by SPARClite DSU and most x86-based targets. These targets
3841 will generate traps when a program accesses some data or instruction
3842 address that is assigned to the debug registers. However the hardware
3843 breakpoint registers can take a limited number of breakpoints. For
3844 example, on the DSU, only two data breakpoints can be set at a time, and
3845 @value{GDBN} will reject this command if more than two are used. Delete
3846 or disable unused hardware breakpoints before setting new ones
3847 (@pxref{Disabling, ,Disabling Breakpoints}).
3848 @xref{Conditions, ,Break Conditions}.
3849 For remote targets, you can restrict the number of hardware
3850 breakpoints @value{GDBN} will use, see @ref{set remote
3851 hardware-breakpoint-limit}.
3854 @item thbreak @var{args}
3855 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3856 are the same as for the @code{hbreak} command and the breakpoint is set in
3857 the same way. However, like the @code{tbreak} command,
3858 the breakpoint is automatically deleted after the
3859 first time your program stops there. Also, like the @code{hbreak}
3860 command, the breakpoint requires hardware support and some target hardware
3861 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3862 See also @ref{Conditions, ,Break Conditions}.
3865 @cindex regular expression
3866 @cindex breakpoints at functions matching a regexp
3867 @cindex set breakpoints in many functions
3868 @item rbreak @var{regex}
3869 Set breakpoints on all functions matching the regular expression
3870 @var{regex}. This command sets an unconditional breakpoint on all
3871 matches, printing a list of all breakpoints it set. Once these
3872 breakpoints are set, they are treated just like the breakpoints set with
3873 the @code{break} command. You can delete them, disable them, or make
3874 them conditional the same way as any other breakpoint.
3876 In programs using different languages, @value{GDBN} chooses the syntax
3877 to print the list of all breakpoints it sets according to the
3878 @samp{set language} value: using @samp{set language auto}
3879 (see @ref{Automatically, ,Set Language Automatically}) means to use the
3880 language of the breakpoint's function, other values mean to use
3881 the manually specified language (see @ref{Manually, ,Set Language Manually}).
3883 The syntax of the regular expression is the standard one used with tools
3884 like @file{grep}. Note that this is different from the syntax used by
3885 shells, so for instance @code{foo*} matches all functions that include
3886 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3887 @code{.*} leading and trailing the regular expression you supply, so to
3888 match only functions that begin with @code{foo}, use @code{^foo}.
3890 @cindex non-member C@t{++} functions, set breakpoint in
3891 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3892 breakpoints on overloaded functions that are not members of any special
3895 @cindex set breakpoints on all functions
3896 The @code{rbreak} command can be used to set breakpoints in
3897 @strong{all} the functions in a program, like this:
3900 (@value{GDBP}) rbreak .
3903 @item rbreak @var{file}:@var{regex}
3904 If @code{rbreak} is called with a filename qualification, it limits
3905 the search for functions matching the given regular expression to the
3906 specified @var{file}. This can be used, for example, to set breakpoints on
3907 every function in a given file:
3910 (@value{GDBP}) rbreak file.c:.
3913 The colon separating the filename qualifier from the regex may
3914 optionally be surrounded by spaces.
3916 @kindex info breakpoints
3917 @cindex @code{$_} and @code{info breakpoints}
3918 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3919 @itemx info break @r{[}@var{list}@dots{}@r{]}
3920 Print a table of all breakpoints, watchpoints, and catchpoints set and
3921 not deleted. Optional argument @var{n} means print information only
3922 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3923 For each breakpoint, following columns are printed:
3926 @item Breakpoint Numbers
3928 Breakpoint, watchpoint, or catchpoint.
3930 Whether the breakpoint is marked to be disabled or deleted when hit.
3931 @item Enabled or Disabled
3932 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3933 that are not enabled.
3935 Where the breakpoint is in your program, as a memory address. For a
3936 pending breakpoint whose address is not yet known, this field will
3937 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3938 library that has the symbol or line referred by breakpoint is loaded.
3939 See below for details. A breakpoint with several locations will
3940 have @samp{<MULTIPLE>} in this field---see below for details.
3942 Where the breakpoint is in the source for your program, as a file and
3943 line number. For a pending breakpoint, the original string passed to
3944 the breakpoint command will be listed as it cannot be resolved until
3945 the appropriate shared library is loaded in the future.
3949 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3950 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3951 @value{GDBN} on the host's side. If it is ``target'', then the condition
3952 is evaluated by the target. The @code{info break} command shows
3953 the condition on the line following the affected breakpoint, together with
3954 its condition evaluation mode in between parentheses.
3956 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3957 allowed to have a condition specified for it. The condition is not parsed for
3958 validity until a shared library is loaded that allows the pending
3959 breakpoint to resolve to a valid location.
3962 @code{info break} with a breakpoint
3963 number @var{n} as argument lists only that breakpoint. The
3964 convenience variable @code{$_} and the default examining-address for
3965 the @code{x} command are set to the address of the last breakpoint
3966 listed (@pxref{Memory, ,Examining Memory}).
3969 @code{info break} displays a count of the number of times the breakpoint
3970 has been hit. This is especially useful in conjunction with the
3971 @code{ignore} command. You can ignore a large number of breakpoint
3972 hits, look at the breakpoint info to see how many times the breakpoint
3973 was hit, and then run again, ignoring one less than that number. This
3974 will get you quickly to the last hit of that breakpoint.
3977 For a breakpoints with an enable count (xref) greater than 1,
3978 @code{info break} also displays that count.
3982 @value{GDBN} allows you to set any number of breakpoints at the same place in
3983 your program. There is nothing silly or meaningless about this. When
3984 the breakpoints are conditional, this is even useful
3985 (@pxref{Conditions, ,Break Conditions}).
3987 @cindex multiple locations, breakpoints
3988 @cindex breakpoints, multiple locations
3989 It is possible that a breakpoint corresponds to several locations
3990 in your program. Examples of this situation are:
3994 Multiple functions in the program may have the same name.
3997 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3998 instances of the function body, used in different cases.
4001 For a C@t{++} template function, a given line in the function can
4002 correspond to any number of instantiations.
4005 For an inlined function, a given source line can correspond to
4006 several places where that function is inlined.
4009 In all those cases, @value{GDBN} will insert a breakpoint at all
4010 the relevant locations.
4012 A breakpoint with multiple locations is displayed in the breakpoint
4013 table using several rows---one header row, followed by one row for
4014 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4015 address column. The rows for individual locations contain the actual
4016 addresses for locations, and show the functions to which those
4017 locations belong. The number column for a location is of the form
4018 @var{breakpoint-number}.@var{location-number}.
4023 Num Type Disp Enb Address What
4024 1 breakpoint keep y <MULTIPLE>
4026 breakpoint already hit 1 time
4027 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4028 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4031 You cannot delete the individual locations from a breakpoint. However,
4032 each location can be individually enabled or disabled by passing
4033 @var{breakpoint-number}.@var{location-number} as argument to the
4034 @code{enable} and @code{disable} commands. It's also possible to
4035 @code{enable} and @code{disable} a range of @var{location-number}
4036 locations using a @var{breakpoint-number} and two @var{location-number}s,
4037 in increasing order, separated by a hyphen, like
4038 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4039 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4040 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4041 all of the locations that belong to that breakpoint.
4043 @cindex pending breakpoints
4044 It's quite common to have a breakpoint inside a shared library.
4045 Shared libraries can be loaded and unloaded explicitly,
4046 and possibly repeatedly, as the program is executed. To support
4047 this use case, @value{GDBN} updates breakpoint locations whenever
4048 any shared library is loaded or unloaded. Typically, you would
4049 set a breakpoint in a shared library at the beginning of your
4050 debugging session, when the library is not loaded, and when the
4051 symbols from the library are not available. When you try to set
4052 breakpoint, @value{GDBN} will ask you if you want to set
4053 a so called @dfn{pending breakpoint}---breakpoint whose address
4054 is not yet resolved.
4056 After the program is run, whenever a new shared library is loaded,
4057 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4058 shared library contains the symbol or line referred to by some
4059 pending breakpoint, that breakpoint is resolved and becomes an
4060 ordinary breakpoint. When a library is unloaded, all breakpoints
4061 that refer to its symbols or source lines become pending again.
4063 This logic works for breakpoints with multiple locations, too. For
4064 example, if you have a breakpoint in a C@t{++} template function, and
4065 a newly loaded shared library has an instantiation of that template,
4066 a new location is added to the list of locations for the breakpoint.
4068 Except for having unresolved address, pending breakpoints do not
4069 differ from regular breakpoints. You can set conditions or commands,
4070 enable and disable them and perform other breakpoint operations.
4072 @value{GDBN} provides some additional commands for controlling what
4073 happens when the @samp{break} command cannot resolve breakpoint
4074 address specification to an address:
4076 @kindex set breakpoint pending
4077 @kindex show breakpoint pending
4079 @item set breakpoint pending auto
4080 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4081 location, it queries you whether a pending breakpoint should be created.
4083 @item set breakpoint pending on
4084 This indicates that an unrecognized breakpoint location should automatically
4085 result in a pending breakpoint being created.
4087 @item set breakpoint pending off
4088 This indicates that pending breakpoints are not to be created. Any
4089 unrecognized breakpoint location results in an error. This setting does
4090 not affect any pending breakpoints previously created.
4092 @item show breakpoint pending
4093 Show the current behavior setting for creating pending breakpoints.
4096 The settings above only affect the @code{break} command and its
4097 variants. Once breakpoint is set, it will be automatically updated
4098 as shared libraries are loaded and unloaded.
4100 @cindex automatic hardware breakpoints
4101 For some targets, @value{GDBN} can automatically decide if hardware or
4102 software breakpoints should be used, depending on whether the
4103 breakpoint address is read-only or read-write. This applies to
4104 breakpoints set with the @code{break} command as well as to internal
4105 breakpoints set by commands like @code{next} and @code{finish}. For
4106 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4109 You can control this automatic behaviour with the following commands:
4111 @kindex set breakpoint auto-hw
4112 @kindex show breakpoint auto-hw
4114 @item set breakpoint auto-hw on
4115 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4116 will try to use the target memory map to decide if software or hardware
4117 breakpoint must be used.
4119 @item set breakpoint auto-hw off
4120 This indicates @value{GDBN} should not automatically select breakpoint
4121 type. If the target provides a memory map, @value{GDBN} will warn when
4122 trying to set software breakpoint at a read-only address.
4125 @value{GDBN} normally implements breakpoints by replacing the program code
4126 at the breakpoint address with a special instruction, which, when
4127 executed, given control to the debugger. By default, the program
4128 code is so modified only when the program is resumed. As soon as
4129 the program stops, @value{GDBN} restores the original instructions. This
4130 behaviour guards against leaving breakpoints inserted in the
4131 target should gdb abrubptly disconnect. However, with slow remote
4132 targets, inserting and removing breakpoint can reduce the performance.
4133 This behavior can be controlled with the following commands::
4135 @kindex set breakpoint always-inserted
4136 @kindex show breakpoint always-inserted
4138 @item set breakpoint always-inserted off
4139 All breakpoints, including newly added by the user, are inserted in
4140 the target only when the target is resumed. All breakpoints are
4141 removed from the target when it stops. This is the default mode.
4143 @item set breakpoint always-inserted on
4144 Causes all breakpoints to be inserted in the target at all times. If
4145 the user adds a new breakpoint, or changes an existing breakpoint, the
4146 breakpoints in the target are updated immediately. A breakpoint is
4147 removed from the target only when breakpoint itself is deleted.
4150 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4151 when a breakpoint breaks. If the condition is true, then the process being
4152 debugged stops, otherwise the process is resumed.
4154 If the target supports evaluating conditions on its end, @value{GDBN} may
4155 download the breakpoint, together with its conditions, to it.
4157 This feature can be controlled via the following commands:
4159 @kindex set breakpoint condition-evaluation
4160 @kindex show breakpoint condition-evaluation
4162 @item set breakpoint condition-evaluation host
4163 This option commands @value{GDBN} to evaluate the breakpoint
4164 conditions on the host's side. Unconditional breakpoints are sent to
4165 the target which in turn receives the triggers and reports them back to GDB
4166 for condition evaluation. This is the standard evaluation mode.
4168 @item set breakpoint condition-evaluation target
4169 This option commands @value{GDBN} to download breakpoint conditions
4170 to the target at the moment of their insertion. The target
4171 is responsible for evaluating the conditional expression and reporting
4172 breakpoint stop events back to @value{GDBN} whenever the condition
4173 is true. Due to limitations of target-side evaluation, some conditions
4174 cannot be evaluated there, e.g., conditions that depend on local data
4175 that is only known to the host. Examples include
4176 conditional expressions involving convenience variables, complex types
4177 that cannot be handled by the agent expression parser and expressions
4178 that are too long to be sent over to the target, specially when the
4179 target is a remote system. In these cases, the conditions will be
4180 evaluated by @value{GDBN}.
4182 @item set breakpoint condition-evaluation auto
4183 This is the default mode. If the target supports evaluating breakpoint
4184 conditions on its end, @value{GDBN} will download breakpoint conditions to
4185 the target (limitations mentioned previously apply). If the target does
4186 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4187 to evaluating all these conditions on the host's side.
4191 @cindex negative breakpoint numbers
4192 @cindex internal @value{GDBN} breakpoints
4193 @value{GDBN} itself sometimes sets breakpoints in your program for
4194 special purposes, such as proper handling of @code{longjmp} (in C
4195 programs). These internal breakpoints are assigned negative numbers,
4196 starting with @code{-1}; @samp{info breakpoints} does not display them.
4197 You can see these breakpoints with the @value{GDBN} maintenance command
4198 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4201 @node Set Watchpoints
4202 @subsection Setting Watchpoints
4204 @cindex setting watchpoints
4205 You can use a watchpoint to stop execution whenever the value of an
4206 expression changes, without having to predict a particular place where
4207 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4208 The expression may be as simple as the value of a single variable, or
4209 as complex as many variables combined by operators. Examples include:
4213 A reference to the value of a single variable.
4216 An address cast to an appropriate data type. For example,
4217 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4218 address (assuming an @code{int} occupies 4 bytes).
4221 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4222 expression can use any operators valid in the program's native
4223 language (@pxref{Languages}).
4226 You can set a watchpoint on an expression even if the expression can
4227 not be evaluated yet. For instance, you can set a watchpoint on
4228 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4229 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4230 the expression produces a valid value. If the expression becomes
4231 valid in some other way than changing a variable (e.g.@: if the memory
4232 pointed to by @samp{*global_ptr} becomes readable as the result of a
4233 @code{malloc} call), @value{GDBN} may not stop until the next time
4234 the expression changes.
4236 @cindex software watchpoints
4237 @cindex hardware watchpoints
4238 Depending on your system, watchpoints may be implemented in software or
4239 hardware. @value{GDBN} does software watchpointing by single-stepping your
4240 program and testing the variable's value each time, which is hundreds of
4241 times slower than normal execution. (But this may still be worth it, to
4242 catch errors where you have no clue what part of your program is the
4245 On some systems, such as most PowerPC or x86-based targets,
4246 @value{GDBN} includes support for hardware watchpoints, which do not
4247 slow down the running of your program.
4251 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4252 Set a watchpoint for an expression. @value{GDBN} will break when the
4253 expression @var{expr} is written into by the program and its value
4254 changes. The simplest (and the most popular) use of this command is
4255 to watch the value of a single variable:
4258 (@value{GDBP}) watch foo
4261 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4262 argument, @value{GDBN} breaks only when the thread identified by
4263 @var{thread-id} changes the value of @var{expr}. If any other threads
4264 change the value of @var{expr}, @value{GDBN} will not break. Note
4265 that watchpoints restricted to a single thread in this way only work
4266 with Hardware Watchpoints.
4268 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4269 (see below). The @code{-location} argument tells @value{GDBN} to
4270 instead watch the memory referred to by @var{expr}. In this case,
4271 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4272 and watch the memory at that address. The type of the result is used
4273 to determine the size of the watched memory. If the expression's
4274 result does not have an address, then @value{GDBN} will print an
4277 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4278 of masked watchpoints, if the current architecture supports this
4279 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4280 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4281 to an address to watch. The mask specifies that some bits of an address
4282 (the bits which are reset in the mask) should be ignored when matching
4283 the address accessed by the inferior against the watchpoint address.
4284 Thus, a masked watchpoint watches many addresses simultaneously---those
4285 addresses whose unmasked bits are identical to the unmasked bits in the
4286 watchpoint address. The @code{mask} argument implies @code{-location}.
4290 (@value{GDBP}) watch foo mask 0xffff00ff
4291 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4295 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4296 Set a watchpoint that will break when the value of @var{expr} is read
4300 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4301 Set a watchpoint that will break when @var{expr} is either read from
4302 or written into by the program.
4304 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4305 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4306 This command prints a list of watchpoints, using the same format as
4307 @code{info break} (@pxref{Set Breaks}).
4310 If you watch for a change in a numerically entered address you need to
4311 dereference it, as the address itself is just a constant number which will
4312 never change. @value{GDBN} refuses to create a watchpoint that watches
4313 a never-changing value:
4316 (@value{GDBP}) watch 0x600850
4317 Cannot watch constant value 0x600850.
4318 (@value{GDBP}) watch *(int *) 0x600850
4319 Watchpoint 1: *(int *) 6293584
4322 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4323 watchpoints execute very quickly, and the debugger reports a change in
4324 value at the exact instruction where the change occurs. If @value{GDBN}
4325 cannot set a hardware watchpoint, it sets a software watchpoint, which
4326 executes more slowly and reports the change in value at the next
4327 @emph{statement}, not the instruction, after the change occurs.
4329 @cindex use only software watchpoints
4330 You can force @value{GDBN} to use only software watchpoints with the
4331 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4332 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4333 the underlying system supports them. (Note that hardware-assisted
4334 watchpoints that were set @emph{before} setting
4335 @code{can-use-hw-watchpoints} to zero will still use the hardware
4336 mechanism of watching expression values.)
4339 @item set can-use-hw-watchpoints
4340 @kindex set can-use-hw-watchpoints
4341 Set whether or not to use hardware watchpoints.
4343 @item show can-use-hw-watchpoints
4344 @kindex show can-use-hw-watchpoints
4345 Show the current mode of using hardware watchpoints.
4348 For remote targets, you can restrict the number of hardware
4349 watchpoints @value{GDBN} will use, see @ref{set remote
4350 hardware-breakpoint-limit}.
4352 When you issue the @code{watch} command, @value{GDBN} reports
4355 Hardware watchpoint @var{num}: @var{expr}
4359 if it was able to set a hardware watchpoint.
4361 Currently, the @code{awatch} and @code{rwatch} commands can only set
4362 hardware watchpoints, because accesses to data that don't change the
4363 value of the watched expression cannot be detected without examining
4364 every instruction as it is being executed, and @value{GDBN} does not do
4365 that currently. If @value{GDBN} finds that it is unable to set a
4366 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4367 will print a message like this:
4370 Expression cannot be implemented with read/access watchpoint.
4373 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4374 data type of the watched expression is wider than what a hardware
4375 watchpoint on the target machine can handle. For example, some systems
4376 can only watch regions that are up to 4 bytes wide; on such systems you
4377 cannot set hardware watchpoints for an expression that yields a
4378 double-precision floating-point number (which is typically 8 bytes
4379 wide). As a work-around, it might be possible to break the large region
4380 into a series of smaller ones and watch them with separate watchpoints.
4382 If you set too many hardware watchpoints, @value{GDBN} might be unable
4383 to insert all of them when you resume the execution of your program.
4384 Since the precise number of active watchpoints is unknown until such
4385 time as the program is about to be resumed, @value{GDBN} might not be
4386 able to warn you about this when you set the watchpoints, and the
4387 warning will be printed only when the program is resumed:
4390 Hardware watchpoint @var{num}: Could not insert watchpoint
4394 If this happens, delete or disable some of the watchpoints.
4396 Watching complex expressions that reference many variables can also
4397 exhaust the resources available for hardware-assisted watchpoints.
4398 That's because @value{GDBN} needs to watch every variable in the
4399 expression with separately allocated resources.
4401 If you call a function interactively using @code{print} or @code{call},
4402 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4403 kind of breakpoint or the call completes.
4405 @value{GDBN} automatically deletes watchpoints that watch local
4406 (automatic) variables, or expressions that involve such variables, when
4407 they go out of scope, that is, when the execution leaves the block in
4408 which these variables were defined. In particular, when the program
4409 being debugged terminates, @emph{all} local variables go out of scope,
4410 and so only watchpoints that watch global variables remain set. If you
4411 rerun the program, you will need to set all such watchpoints again. One
4412 way of doing that would be to set a code breakpoint at the entry to the
4413 @code{main} function and when it breaks, set all the watchpoints.
4415 @cindex watchpoints and threads
4416 @cindex threads and watchpoints
4417 In multi-threaded programs, watchpoints will detect changes to the
4418 watched expression from every thread.
4421 @emph{Warning:} In multi-threaded programs, software watchpoints
4422 have only limited usefulness. If @value{GDBN} creates a software
4423 watchpoint, it can only watch the value of an expression @emph{in a
4424 single thread}. If you are confident that the expression can only
4425 change due to the current thread's activity (and if you are also
4426 confident that no other thread can become current), then you can use
4427 software watchpoints as usual. However, @value{GDBN} may not notice
4428 when a non-current thread's activity changes the expression. (Hardware
4429 watchpoints, in contrast, watch an expression in all threads.)
4432 @xref{set remote hardware-watchpoint-limit}.
4434 @node Set Catchpoints
4435 @subsection Setting Catchpoints
4436 @cindex catchpoints, setting
4437 @cindex exception handlers
4438 @cindex event handling
4440 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4441 kinds of program events, such as C@t{++} exceptions or the loading of a
4442 shared library. Use the @code{catch} command to set a catchpoint.
4446 @item catch @var{event}
4447 Stop when @var{event} occurs. The @var{event} can be any of the following:
4450 @item throw @r{[}@var{regexp}@r{]}
4451 @itemx rethrow @r{[}@var{regexp}@r{]}
4452 @itemx catch @r{[}@var{regexp}@r{]}
4454 @kindex catch rethrow
4456 @cindex stop on C@t{++} exceptions
4457 The throwing, re-throwing, or catching of a C@t{++} exception.
4459 If @var{regexp} is given, then only exceptions whose type matches the
4460 regular expression will be caught.
4462 @vindex $_exception@r{, convenience variable}
4463 The convenience variable @code{$_exception} is available at an
4464 exception-related catchpoint, on some systems. This holds the
4465 exception being thrown.
4467 There are currently some limitations to C@t{++} exception handling in
4472 The support for these commands is system-dependent. Currently, only
4473 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4477 The regular expression feature and the @code{$_exception} convenience
4478 variable rely on the presence of some SDT probes in @code{libstdc++}.
4479 If these probes are not present, then these features cannot be used.
4480 These probes were first available in the GCC 4.8 release, but whether
4481 or not they are available in your GCC also depends on how it was
4485 The @code{$_exception} convenience variable is only valid at the
4486 instruction at which an exception-related catchpoint is set.
4489 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4490 location in the system library which implements runtime exception
4491 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4492 (@pxref{Selection}) to get to your code.
4495 If you call a function interactively, @value{GDBN} normally returns
4496 control to you when the function has finished executing. If the call
4497 raises an exception, however, the call may bypass the mechanism that
4498 returns control to you and cause your program either to abort or to
4499 simply continue running until it hits a breakpoint, catches a signal
4500 that @value{GDBN} is listening for, or exits. This is the case even if
4501 you set a catchpoint for the exception; catchpoints on exceptions are
4502 disabled within interactive calls. @xref{Calling}, for information on
4503 controlling this with @code{set unwind-on-terminating-exception}.
4506 You cannot raise an exception interactively.
4509 You cannot install an exception handler interactively.
4513 @kindex catch exception
4514 @cindex Ada exception catching
4515 @cindex catch Ada exceptions
4516 An Ada exception being raised. If an exception name is specified
4517 at the end of the command (eg @code{catch exception Program_Error}),
4518 the debugger will stop only when this specific exception is raised.
4519 Otherwise, the debugger stops execution when any Ada exception is raised.
4521 When inserting an exception catchpoint on a user-defined exception whose
4522 name is identical to one of the exceptions defined by the language, the
4523 fully qualified name must be used as the exception name. Otherwise,
4524 @value{GDBN} will assume that it should stop on the pre-defined exception
4525 rather than the user-defined one. For instance, assuming an exception
4526 called @code{Constraint_Error} is defined in package @code{Pck}, then
4527 the command to use to catch such exceptions is @kbd{catch exception
4528 Pck.Constraint_Error}.
4531 @kindex catch handlers
4532 @cindex Ada exception handlers catching
4533 @cindex catch Ada exceptions when handled
4534 An Ada exception being handled. If an exception name is
4535 specified at the end of the command
4536 (eg @kbd{catch handlers Program_Error}), the debugger will stop
4537 only when this specific exception is handled.
4538 Otherwise, the debugger stops execution when any Ada exception is handled.
4540 When inserting a handlers catchpoint on a user-defined
4541 exception whose name is identical to one of the exceptions
4542 defined by the language, the fully qualified name must be used
4543 as the exception name. Otherwise, @value{GDBN} will assume that it
4544 should stop on the pre-defined exception rather than the
4545 user-defined one. For instance, assuming an exception called
4546 @code{Constraint_Error} is defined in package @code{Pck}, then the
4547 command to use to catch such exceptions handling is
4548 @kbd{catch handlers Pck.Constraint_Error}.
4550 @item exception unhandled
4551 @kindex catch exception unhandled
4552 An exception that was raised but is not handled by the program.
4555 @kindex catch assert
4556 A failed Ada assertion.
4560 @cindex break on fork/exec
4561 A call to @code{exec}.
4563 @anchor{catch syscall}
4565 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4566 @kindex catch syscall
4567 @cindex break on a system call.
4568 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4569 syscall is a mechanism for application programs to request a service
4570 from the operating system (OS) or one of the OS system services.
4571 @value{GDBN} can catch some or all of the syscalls issued by the
4572 debuggee, and show the related information for each syscall. If no
4573 argument is specified, calls to and returns from all system calls
4576 @var{name} can be any system call name that is valid for the
4577 underlying OS. Just what syscalls are valid depends on the OS. On
4578 GNU and Unix systems, you can find the full list of valid syscall
4579 names on @file{/usr/include/asm/unistd.h}.
4581 @c For MS-Windows, the syscall names and the corresponding numbers
4582 @c can be found, e.g., on this URL:
4583 @c http://www.metasploit.com/users/opcode/syscalls.html
4584 @c but we don't support Windows syscalls yet.
4586 Normally, @value{GDBN} knows in advance which syscalls are valid for
4587 each OS, so you can use the @value{GDBN} command-line completion
4588 facilities (@pxref{Completion,, command completion}) to list the
4591 You may also specify the system call numerically. A syscall's
4592 number is the value passed to the OS's syscall dispatcher to
4593 identify the requested service. When you specify the syscall by its
4594 name, @value{GDBN} uses its database of syscalls to convert the name
4595 into the corresponding numeric code, but using the number directly
4596 may be useful if @value{GDBN}'s database does not have the complete
4597 list of syscalls on your system (e.g., because @value{GDBN} lags
4598 behind the OS upgrades).
4600 You may specify a group of related syscalls to be caught at once using
4601 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4602 instance, on some platforms @value{GDBN} allows you to catch all
4603 network related syscalls, by passing the argument @code{group:network}
4604 to @code{catch syscall}. Note that not all syscall groups are
4605 available in every system. You can use the command completion
4606 facilities (@pxref{Completion,, command completion}) to list the
4607 syscall groups available on your environment.
4609 The example below illustrates how this command works if you don't provide
4613 (@value{GDBP}) catch syscall
4614 Catchpoint 1 (syscall)
4616 Starting program: /tmp/catch-syscall
4618 Catchpoint 1 (call to syscall 'close'), \
4619 0xffffe424 in __kernel_vsyscall ()
4623 Catchpoint 1 (returned from syscall 'close'), \
4624 0xffffe424 in __kernel_vsyscall ()
4628 Here is an example of catching a system call by name:
4631 (@value{GDBP}) catch syscall chroot
4632 Catchpoint 1 (syscall 'chroot' [61])
4634 Starting program: /tmp/catch-syscall
4636 Catchpoint 1 (call to syscall 'chroot'), \
4637 0xffffe424 in __kernel_vsyscall ()
4641 Catchpoint 1 (returned from syscall 'chroot'), \
4642 0xffffe424 in __kernel_vsyscall ()
4646 An example of specifying a system call numerically. In the case
4647 below, the syscall number has a corresponding entry in the XML
4648 file, so @value{GDBN} finds its name and prints it:
4651 (@value{GDBP}) catch syscall 252
4652 Catchpoint 1 (syscall(s) 'exit_group')
4654 Starting program: /tmp/catch-syscall
4656 Catchpoint 1 (call to syscall 'exit_group'), \
4657 0xffffe424 in __kernel_vsyscall ()
4661 Program exited normally.
4665 Here is an example of catching a syscall group:
4668 (@value{GDBP}) catch syscall group:process
4669 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4670 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4671 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4673 Starting program: /tmp/catch-syscall
4675 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4676 from /lib64/ld-linux-x86-64.so.2
4682 However, there can be situations when there is no corresponding name
4683 in XML file for that syscall number. In this case, @value{GDBN} prints
4684 a warning message saying that it was not able to find the syscall name,
4685 but the catchpoint will be set anyway. See the example below:
4688 (@value{GDBP}) catch syscall 764
4689 warning: The number '764' does not represent a known syscall.
4690 Catchpoint 2 (syscall 764)
4694 If you configure @value{GDBN} using the @samp{--without-expat} option,
4695 it will not be able to display syscall names. Also, if your
4696 architecture does not have an XML file describing its system calls,
4697 you will not be able to see the syscall names. It is important to
4698 notice that these two features are used for accessing the syscall
4699 name database. In either case, you will see a warning like this:
4702 (@value{GDBP}) catch syscall
4703 warning: Could not open "syscalls/i386-linux.xml"
4704 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4705 GDB will not be able to display syscall names.
4706 Catchpoint 1 (syscall)
4710 Of course, the file name will change depending on your architecture and system.
4712 Still using the example above, you can also try to catch a syscall by its
4713 number. In this case, you would see something like:
4716 (@value{GDBP}) catch syscall 252
4717 Catchpoint 1 (syscall(s) 252)
4720 Again, in this case @value{GDBN} would not be able to display syscall's names.
4724 A call to @code{fork}.
4728 A call to @code{vfork}.
4730 @item load @r{[}regexp@r{]}
4731 @itemx unload @r{[}regexp@r{]}
4733 @kindex catch unload
4734 The loading or unloading of a shared library. If @var{regexp} is
4735 given, then the catchpoint will stop only if the regular expression
4736 matches one of the affected libraries.
4738 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4739 @kindex catch signal
4740 The delivery of a signal.
4742 With no arguments, this catchpoint will catch any signal that is not
4743 used internally by @value{GDBN}, specifically, all signals except
4744 @samp{SIGTRAP} and @samp{SIGINT}.
4746 With the argument @samp{all}, all signals, including those used by
4747 @value{GDBN}, will be caught. This argument cannot be used with other
4750 Otherwise, the arguments are a list of signal names as given to
4751 @code{handle} (@pxref{Signals}). Only signals specified in this list
4754 One reason that @code{catch signal} can be more useful than
4755 @code{handle} is that you can attach commands and conditions to the
4758 When a signal is caught by a catchpoint, the signal's @code{stop} and
4759 @code{print} settings, as specified by @code{handle}, are ignored.
4760 However, whether the signal is still delivered to the inferior depends
4761 on the @code{pass} setting; this can be changed in the catchpoint's
4766 @item tcatch @var{event}
4768 Set a catchpoint that is enabled only for one stop. The catchpoint is
4769 automatically deleted after the first time the event is caught.
4773 Use the @code{info break} command to list the current catchpoints.
4777 @subsection Deleting Breakpoints
4779 @cindex clearing breakpoints, watchpoints, catchpoints
4780 @cindex deleting breakpoints, watchpoints, catchpoints
4781 It is often necessary to eliminate a breakpoint, watchpoint, or
4782 catchpoint once it has done its job and you no longer want your program
4783 to stop there. This is called @dfn{deleting} the breakpoint. A
4784 breakpoint that has been deleted no longer exists; it is forgotten.
4786 With the @code{clear} command you can delete breakpoints according to
4787 where they are in your program. With the @code{delete} command you can
4788 delete individual breakpoints, watchpoints, or catchpoints by specifying
4789 their breakpoint numbers.
4791 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4792 automatically ignores breakpoints on the first instruction to be executed
4793 when you continue execution without changing the execution address.
4798 Delete any breakpoints at the next instruction to be executed in the
4799 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4800 the innermost frame is selected, this is a good way to delete a
4801 breakpoint where your program just stopped.
4803 @item clear @var{location}
4804 Delete any breakpoints set at the specified @var{location}.
4805 @xref{Specify Location}, for the various forms of @var{location}; the
4806 most useful ones are listed below:
4809 @item clear @var{function}
4810 @itemx clear @var{filename}:@var{function}
4811 Delete any breakpoints set at entry to the named @var{function}.
4813 @item clear @var{linenum}
4814 @itemx clear @var{filename}:@var{linenum}
4815 Delete any breakpoints set at or within the code of the specified
4816 @var{linenum} of the specified @var{filename}.
4819 @cindex delete breakpoints
4821 @kindex d @r{(@code{delete})}
4822 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4823 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4824 list specified as argument. If no argument is specified, delete all
4825 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4826 confirm off}). You can abbreviate this command as @code{d}.
4830 @subsection Disabling Breakpoints
4832 @cindex enable/disable a breakpoint
4833 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4834 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4835 it had been deleted, but remembers the information on the breakpoint so
4836 that you can @dfn{enable} it again later.
4838 You disable and enable breakpoints, watchpoints, and catchpoints with
4839 the @code{enable} and @code{disable} commands, optionally specifying
4840 one or more breakpoint numbers as arguments. Use @code{info break} to
4841 print a list of all breakpoints, watchpoints, and catchpoints if you
4842 do not know which numbers to use.
4844 Disabling and enabling a breakpoint that has multiple locations
4845 affects all of its locations.
4847 A breakpoint, watchpoint, or catchpoint can have any of several
4848 different states of enablement:
4852 Enabled. The breakpoint stops your program. A breakpoint set
4853 with the @code{break} command starts out in this state.
4855 Disabled. The breakpoint has no effect on your program.
4857 Enabled once. The breakpoint stops your program, but then becomes
4860 Enabled for a count. The breakpoint stops your program for the next
4861 N times, then becomes disabled.
4863 Enabled for deletion. The breakpoint stops your program, but
4864 immediately after it does so it is deleted permanently. A breakpoint
4865 set with the @code{tbreak} command starts out in this state.
4868 You can use the following commands to enable or disable breakpoints,
4869 watchpoints, and catchpoints:
4873 @kindex dis @r{(@code{disable})}
4874 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4875 Disable the specified breakpoints---or all breakpoints, if none are
4876 listed. A disabled breakpoint has no effect but is not forgotten. All
4877 options such as ignore-counts, conditions and commands are remembered in
4878 case the breakpoint is enabled again later. You may abbreviate
4879 @code{disable} as @code{dis}.
4882 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4883 Enable the specified breakpoints (or all defined breakpoints). They
4884 become effective once again in stopping your program.
4886 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4887 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4888 of these breakpoints immediately after stopping your program.
4890 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4891 Enable the specified breakpoints temporarily. @value{GDBN} records
4892 @var{count} with each of the specified breakpoints, and decrements a
4893 breakpoint's count when it is hit. When any count reaches 0,
4894 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4895 count (@pxref{Conditions, ,Break Conditions}), that will be
4896 decremented to 0 before @var{count} is affected.
4898 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4899 Enable the specified breakpoints to work once, then die. @value{GDBN}
4900 deletes any of these breakpoints as soon as your program stops there.
4901 Breakpoints set by the @code{tbreak} command start out in this state.
4904 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4905 @c confusing: tbreak is also initially enabled.
4906 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4907 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4908 subsequently, they become disabled or enabled only when you use one of
4909 the commands above. (The command @code{until} can set and delete a
4910 breakpoint of its own, but it does not change the state of your other
4911 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4915 @subsection Break Conditions
4916 @cindex conditional breakpoints
4917 @cindex breakpoint conditions
4919 @c FIXME what is scope of break condition expr? Context where wanted?
4920 @c in particular for a watchpoint?
4921 The simplest sort of breakpoint breaks every time your program reaches a
4922 specified place. You can also specify a @dfn{condition} for a
4923 breakpoint. A condition is just a Boolean expression in your
4924 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4925 a condition evaluates the expression each time your program reaches it,
4926 and your program stops only if the condition is @emph{true}.
4928 This is the converse of using assertions for program validation; in that
4929 situation, you want to stop when the assertion is violated---that is,
4930 when the condition is false. In C, if you want to test an assertion expressed
4931 by the condition @var{assert}, you should set the condition
4932 @samp{! @var{assert}} on the appropriate breakpoint.
4934 Conditions are also accepted for watchpoints; you may not need them,
4935 since a watchpoint is inspecting the value of an expression anyhow---but
4936 it might be simpler, say, to just set a watchpoint on a variable name,
4937 and specify a condition that tests whether the new value is an interesting
4940 Break conditions can have side effects, and may even call functions in
4941 your program. This can be useful, for example, to activate functions
4942 that log program progress, or to use your own print functions to
4943 format special data structures. The effects are completely predictable
4944 unless there is another enabled breakpoint at the same address. (In
4945 that case, @value{GDBN} might see the other breakpoint first and stop your
4946 program without checking the condition of this one.) Note that
4947 breakpoint commands are usually more convenient and flexible than break
4949 purpose of performing side effects when a breakpoint is reached
4950 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4952 Breakpoint conditions can also be evaluated on the target's side if
4953 the target supports it. Instead of evaluating the conditions locally,
4954 @value{GDBN} encodes the expression into an agent expression
4955 (@pxref{Agent Expressions}) suitable for execution on the target,
4956 independently of @value{GDBN}. Global variables become raw memory
4957 locations, locals become stack accesses, and so forth.
4959 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4960 when its condition evaluates to true. This mechanism may provide faster
4961 response times depending on the performance characteristics of the target
4962 since it does not need to keep @value{GDBN} informed about
4963 every breakpoint trigger, even those with false conditions.
4965 Break conditions can be specified when a breakpoint is set, by using
4966 @samp{if} in the arguments to the @code{break} command. @xref{Set
4967 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4968 with the @code{condition} command.
4970 You can also use the @code{if} keyword with the @code{watch} command.
4971 The @code{catch} command does not recognize the @code{if} keyword;
4972 @code{condition} is the only way to impose a further condition on a
4977 @item condition @var{bnum} @var{expression}
4978 Specify @var{expression} as the break condition for breakpoint,
4979 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4980 breakpoint @var{bnum} stops your program only if the value of
4981 @var{expression} is true (nonzero, in C). When you use
4982 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4983 syntactic correctness, and to determine whether symbols in it have
4984 referents in the context of your breakpoint. If @var{expression} uses
4985 symbols not referenced in the context of the breakpoint, @value{GDBN}
4986 prints an error message:
4989 No symbol "foo" in current context.
4994 not actually evaluate @var{expression} at the time the @code{condition}
4995 command (or a command that sets a breakpoint with a condition, like
4996 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4998 @item condition @var{bnum}
4999 Remove the condition from breakpoint number @var{bnum}. It becomes
5000 an ordinary unconditional breakpoint.
5003 @cindex ignore count (of breakpoint)
5004 A special case of a breakpoint condition is to stop only when the
5005 breakpoint has been reached a certain number of times. This is so
5006 useful that there is a special way to do it, using the @dfn{ignore
5007 count} of the breakpoint. Every breakpoint has an ignore count, which
5008 is an integer. Most of the time, the ignore count is zero, and
5009 therefore has no effect. But if your program reaches a breakpoint whose
5010 ignore count is positive, then instead of stopping, it just decrements
5011 the ignore count by one and continues. As a result, if the ignore count
5012 value is @var{n}, the breakpoint does not stop the next @var{n} times
5013 your program reaches it.
5017 @item ignore @var{bnum} @var{count}
5018 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5019 The next @var{count} times the breakpoint is reached, your program's
5020 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5023 To make the breakpoint stop the next time it is reached, specify
5026 When you use @code{continue} to resume execution of your program from a
5027 breakpoint, you can specify an ignore count directly as an argument to
5028 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5029 Stepping,,Continuing and Stepping}.
5031 If a breakpoint has a positive ignore count and a condition, the
5032 condition is not checked. Once the ignore count reaches zero,
5033 @value{GDBN} resumes checking the condition.
5035 You could achieve the effect of the ignore count with a condition such
5036 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5037 is decremented each time. @xref{Convenience Vars, ,Convenience
5041 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5044 @node Break Commands
5045 @subsection Breakpoint Command Lists
5047 @cindex breakpoint commands
5048 You can give any breakpoint (or watchpoint or catchpoint) a series of
5049 commands to execute when your program stops due to that breakpoint. For
5050 example, you might want to print the values of certain expressions, or
5051 enable other breakpoints.
5055 @kindex end@r{ (breakpoint commands)}
5056 @item commands @r{[}@var{list}@dots{}@r{]}
5057 @itemx @dots{} @var{command-list} @dots{}
5059 Specify a list of commands for the given breakpoints. The commands
5060 themselves appear on the following lines. Type a line containing just
5061 @code{end} to terminate the commands.
5063 To remove all commands from a breakpoint, type @code{commands} and
5064 follow it immediately with @code{end}; that is, give no commands.
5066 With no argument, @code{commands} refers to the last breakpoint,
5067 watchpoint, or catchpoint set (not to the breakpoint most recently
5068 encountered). If the most recent breakpoints were set with a single
5069 command, then the @code{commands} will apply to all the breakpoints
5070 set by that command. This applies to breakpoints set by
5071 @code{rbreak}, and also applies when a single @code{break} command
5072 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5076 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5077 disabled within a @var{command-list}.
5079 You can use breakpoint commands to start your program up again. Simply
5080 use the @code{continue} command, or @code{step}, or any other command
5081 that resumes execution.
5083 Any other commands in the command list, after a command that resumes
5084 execution, are ignored. This is because any time you resume execution
5085 (even with a simple @code{next} or @code{step}), you may encounter
5086 another breakpoint---which could have its own command list, leading to
5087 ambiguities about which list to execute.
5090 If the first command you specify in a command list is @code{silent}, the
5091 usual message about stopping at a breakpoint is not printed. This may
5092 be desirable for breakpoints that are to print a specific message and
5093 then continue. If none of the remaining commands print anything, you
5094 see no sign that the breakpoint was reached. @code{silent} is
5095 meaningful only at the beginning of a breakpoint command list.
5097 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5098 print precisely controlled output, and are often useful in silent
5099 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5101 For example, here is how you could use breakpoint commands to print the
5102 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5108 printf "x is %d\n",x
5113 One application for breakpoint commands is to compensate for one bug so
5114 you can test for another. Put a breakpoint just after the erroneous line
5115 of code, give it a condition to detect the case in which something
5116 erroneous has been done, and give it commands to assign correct values
5117 to any variables that need them. End with the @code{continue} command
5118 so that your program does not stop, and start with the @code{silent}
5119 command so that no output is produced. Here is an example:
5130 @node Dynamic Printf
5131 @subsection Dynamic Printf
5133 @cindex dynamic printf
5135 The dynamic printf command @code{dprintf} combines a breakpoint with
5136 formatted printing of your program's data to give you the effect of
5137 inserting @code{printf} calls into your program on-the-fly, without
5138 having to recompile it.
5140 In its most basic form, the output goes to the GDB console. However,
5141 you can set the variable @code{dprintf-style} for alternate handling.
5142 For instance, you can ask to format the output by calling your
5143 program's @code{printf} function. This has the advantage that the
5144 characters go to the program's output device, so they can recorded in
5145 redirects to files and so forth.
5147 If you are doing remote debugging with a stub or agent, you can also
5148 ask to have the printf handled by the remote agent. In addition to
5149 ensuring that the output goes to the remote program's device along
5150 with any other output the program might produce, you can also ask that
5151 the dprintf remain active even after disconnecting from the remote
5152 target. Using the stub/agent is also more efficient, as it can do
5153 everything without needing to communicate with @value{GDBN}.
5157 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5158 Whenever execution reaches @var{location}, print the values of one or
5159 more @var{expressions} under the control of the string @var{template}.
5160 To print several values, separate them with commas.
5162 @item set dprintf-style @var{style}
5163 Set the dprintf output to be handled in one of several different
5164 styles enumerated below. A change of style affects all existing
5165 dynamic printfs immediately. (If you need individual control over the
5166 print commands, simply define normal breakpoints with
5167 explicitly-supplied command lists.)
5171 @kindex dprintf-style gdb
5172 Handle the output using the @value{GDBN} @code{printf} command.
5175 @kindex dprintf-style call
5176 Handle the output by calling a function in your program (normally
5180 @kindex dprintf-style agent
5181 Have the remote debugging agent (such as @code{gdbserver}) handle
5182 the output itself. This style is only available for agents that
5183 support running commands on the target.
5186 @item set dprintf-function @var{function}
5187 Set the function to call if the dprintf style is @code{call}. By
5188 default its value is @code{printf}. You may set it to any expression.
5189 that @value{GDBN} can evaluate to a function, as per the @code{call}
5192 @item set dprintf-channel @var{channel}
5193 Set a ``channel'' for dprintf. If set to a non-empty value,
5194 @value{GDBN} will evaluate it as an expression and pass the result as
5195 a first argument to the @code{dprintf-function}, in the manner of
5196 @code{fprintf} and similar functions. Otherwise, the dprintf format
5197 string will be the first argument, in the manner of @code{printf}.
5199 As an example, if you wanted @code{dprintf} output to go to a logfile
5200 that is a standard I/O stream assigned to the variable @code{mylog},
5201 you could do the following:
5204 (gdb) set dprintf-style call
5205 (gdb) set dprintf-function fprintf
5206 (gdb) set dprintf-channel mylog
5207 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5208 Dprintf 1 at 0x123456: file main.c, line 25.
5210 1 dprintf keep y 0x00123456 in main at main.c:25
5211 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5216 Note that the @code{info break} displays the dynamic printf commands
5217 as normal breakpoint commands; you can thus easily see the effect of
5218 the variable settings.
5220 @item set disconnected-dprintf on
5221 @itemx set disconnected-dprintf off
5222 @kindex set disconnected-dprintf
5223 Choose whether @code{dprintf} commands should continue to run if
5224 @value{GDBN} has disconnected from the target. This only applies
5225 if the @code{dprintf-style} is @code{agent}.
5227 @item show disconnected-dprintf off
5228 @kindex show disconnected-dprintf
5229 Show the current choice for disconnected @code{dprintf}.
5233 @value{GDBN} does not check the validity of function and channel,
5234 relying on you to supply values that are meaningful for the contexts
5235 in which they are being used. For instance, the function and channel
5236 may be the values of local variables, but if that is the case, then
5237 all enabled dynamic prints must be at locations within the scope of
5238 those locals. If evaluation fails, @value{GDBN} will report an error.
5240 @node Save Breakpoints
5241 @subsection How to save breakpoints to a file
5243 To save breakpoint definitions to a file use the @w{@code{save
5244 breakpoints}} command.
5247 @kindex save breakpoints
5248 @cindex save breakpoints to a file for future sessions
5249 @item save breakpoints [@var{filename}]
5250 This command saves all current breakpoint definitions together with
5251 their commands and ignore counts, into a file @file{@var{filename}}
5252 suitable for use in a later debugging session. This includes all
5253 types of breakpoints (breakpoints, watchpoints, catchpoints,
5254 tracepoints). To read the saved breakpoint definitions, use the
5255 @code{source} command (@pxref{Command Files}). Note that watchpoints
5256 with expressions involving local variables may fail to be recreated
5257 because it may not be possible to access the context where the
5258 watchpoint is valid anymore. Because the saved breakpoint definitions
5259 are simply a sequence of @value{GDBN} commands that recreate the
5260 breakpoints, you can edit the file in your favorite editing program,
5261 and remove the breakpoint definitions you're not interested in, or
5262 that can no longer be recreated.
5265 @node Static Probe Points
5266 @subsection Static Probe Points
5268 @cindex static probe point, SystemTap
5269 @cindex static probe point, DTrace
5270 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5271 for Statically Defined Tracing, and the probes are designed to have a tiny
5272 runtime code and data footprint, and no dynamic relocations.
5274 Currently, the following types of probes are supported on
5275 ELF-compatible systems:
5279 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5280 @acronym{SDT} probes@footnote{See
5281 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5282 for more information on how to add @code{SystemTap} @acronym{SDT}
5283 probes in your applications.}. @code{SystemTap} probes are usable
5284 from assembly, C and C@t{++} languages@footnote{See
5285 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5286 for a good reference on how the @acronym{SDT} probes are implemented.}.
5288 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5289 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5293 @cindex semaphores on static probe points
5294 Some @code{SystemTap} probes have an associated semaphore variable;
5295 for instance, this happens automatically if you defined your probe
5296 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5297 @value{GDBN} will automatically enable it when you specify a
5298 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5299 breakpoint at a probe's location by some other method (e.g.,
5300 @code{break file:line}), then @value{GDBN} will not automatically set
5301 the semaphore. @code{DTrace} probes do not support semaphores.
5303 You can examine the available static static probes using @code{info
5304 probes}, with optional arguments:
5308 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5309 If given, @var{type} is either @code{stap} for listing
5310 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5311 probes. If omitted all probes are listed regardless of their types.
5313 If given, @var{provider} is a regular expression used to match against provider
5314 names when selecting which probes to list. If omitted, probes by all
5315 probes from all providers are listed.
5317 If given, @var{name} is a regular expression to match against probe names
5318 when selecting which probes to list. If omitted, probe names are not
5319 considered when deciding whether to display them.
5321 If given, @var{objfile} is a regular expression used to select which
5322 object files (executable or shared libraries) to examine. If not
5323 given, all object files are considered.
5325 @item info probes all
5326 List the available static probes, from all types.
5329 @cindex enabling and disabling probes
5330 Some probe points can be enabled and/or disabled. The effect of
5331 enabling or disabling a probe depends on the type of probe being
5332 handled. Some @code{DTrace} probes can be enabled or
5333 disabled, but @code{SystemTap} probes cannot be disabled.
5335 You can enable (or disable) one or more probes using the following
5336 commands, with optional arguments:
5339 @kindex enable probes
5340 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5341 If given, @var{provider} is a regular expression used to match against
5342 provider names when selecting which probes to enable. If omitted,
5343 all probes from all providers are enabled.
5345 If given, @var{name} is a regular expression to match against probe
5346 names when selecting which probes to enable. If omitted, probe names
5347 are not considered when deciding whether to enable them.
5349 If given, @var{objfile} is a regular expression used to select which
5350 object files (executable or shared libraries) to examine. If not
5351 given, all object files are considered.
5353 @kindex disable probes
5354 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5355 See the @code{enable probes} command above for a description of the
5356 optional arguments accepted by this command.
5359 @vindex $_probe_arg@r{, convenience variable}
5360 A probe may specify up to twelve arguments. These are available at the
5361 point at which the probe is defined---that is, when the current PC is
5362 at the probe's location. The arguments are available using the
5363 convenience variables (@pxref{Convenience Vars})
5364 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5365 probes each probe argument is an integer of the appropriate size;
5366 types are not preserved. In @code{DTrace} probes types are preserved
5367 provided that they are recognized as such by @value{GDBN}; otherwise
5368 the value of the probe argument will be a long integer. The
5369 convenience variable @code{$_probe_argc} holds the number of arguments
5370 at the current probe point.
5372 These variables are always available, but attempts to access them at
5373 any location other than a probe point will cause @value{GDBN} to give
5377 @c @ifclear BARETARGET
5378 @node Error in Breakpoints
5379 @subsection ``Cannot insert breakpoints''
5381 If you request too many active hardware-assisted breakpoints and
5382 watchpoints, you will see this error message:
5384 @c FIXME: the precise wording of this message may change; the relevant
5385 @c source change is not committed yet (Sep 3, 1999).
5387 Stopped; cannot insert breakpoints.
5388 You may have requested too many hardware breakpoints and watchpoints.
5392 This message is printed when you attempt to resume the program, since
5393 only then @value{GDBN} knows exactly how many hardware breakpoints and
5394 watchpoints it needs to insert.
5396 When this message is printed, you need to disable or remove some of the
5397 hardware-assisted breakpoints and watchpoints, and then continue.
5399 @node Breakpoint-related Warnings
5400 @subsection ``Breakpoint address adjusted...''
5401 @cindex breakpoint address adjusted
5403 Some processor architectures place constraints on the addresses at
5404 which breakpoints may be placed. For architectures thus constrained,
5405 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5406 with the constraints dictated by the architecture.
5408 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5409 a VLIW architecture in which a number of RISC-like instructions may be
5410 bundled together for parallel execution. The FR-V architecture
5411 constrains the location of a breakpoint instruction within such a
5412 bundle to the instruction with the lowest address. @value{GDBN}
5413 honors this constraint by adjusting a breakpoint's address to the
5414 first in the bundle.
5416 It is not uncommon for optimized code to have bundles which contain
5417 instructions from different source statements, thus it may happen that
5418 a breakpoint's address will be adjusted from one source statement to
5419 another. Since this adjustment may significantly alter @value{GDBN}'s
5420 breakpoint related behavior from what the user expects, a warning is
5421 printed when the breakpoint is first set and also when the breakpoint
5424 A warning like the one below is printed when setting a breakpoint
5425 that's been subject to address adjustment:
5428 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5431 Such warnings are printed both for user settable and @value{GDBN}'s
5432 internal breakpoints. If you see one of these warnings, you should
5433 verify that a breakpoint set at the adjusted address will have the
5434 desired affect. If not, the breakpoint in question may be removed and
5435 other breakpoints may be set which will have the desired behavior.
5436 E.g., it may be sufficient to place the breakpoint at a later
5437 instruction. A conditional breakpoint may also be useful in some
5438 cases to prevent the breakpoint from triggering too often.
5440 @value{GDBN} will also issue a warning when stopping at one of these
5441 adjusted breakpoints:
5444 warning: Breakpoint 1 address previously adjusted from 0x00010414
5448 When this warning is encountered, it may be too late to take remedial
5449 action except in cases where the breakpoint is hit earlier or more
5450 frequently than expected.
5452 @node Continuing and Stepping
5453 @section Continuing and Stepping
5457 @cindex resuming execution
5458 @dfn{Continuing} means resuming program execution until your program
5459 completes normally. In contrast, @dfn{stepping} means executing just
5460 one more ``step'' of your program, where ``step'' may mean either one
5461 line of source code, or one machine instruction (depending on what
5462 particular command you use). Either when continuing or when stepping,
5463 your program may stop even sooner, due to a breakpoint or a signal. (If
5464 it stops due to a signal, you may want to use @code{handle}, or use
5465 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5466 or you may step into the signal's handler (@pxref{stepping and signal
5471 @kindex c @r{(@code{continue})}
5472 @kindex fg @r{(resume foreground execution)}
5473 @item continue @r{[}@var{ignore-count}@r{]}
5474 @itemx c @r{[}@var{ignore-count}@r{]}
5475 @itemx fg @r{[}@var{ignore-count}@r{]}
5476 Resume program execution, at the address where your program last stopped;
5477 any breakpoints set at that address are bypassed. The optional argument
5478 @var{ignore-count} allows you to specify a further number of times to
5479 ignore a breakpoint at this location; its effect is like that of
5480 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5482 The argument @var{ignore-count} is meaningful only when your program
5483 stopped due to a breakpoint. At other times, the argument to
5484 @code{continue} is ignored.
5486 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5487 debugged program is deemed to be the foreground program) are provided
5488 purely for convenience, and have exactly the same behavior as
5492 To resume execution at a different place, you can use @code{return}
5493 (@pxref{Returning, ,Returning from a Function}) to go back to the
5494 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5495 Different Address}) to go to an arbitrary location in your program.
5497 A typical technique for using stepping is to set a breakpoint
5498 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5499 beginning of the function or the section of your program where a problem
5500 is believed to lie, run your program until it stops at that breakpoint,
5501 and then step through the suspect area, examining the variables that are
5502 interesting, until you see the problem happen.
5506 @kindex s @r{(@code{step})}
5508 Continue running your program until control reaches a different source
5509 line, then stop it and return control to @value{GDBN}. This command is
5510 abbreviated @code{s}.
5513 @c "without debugging information" is imprecise; actually "without line
5514 @c numbers in the debugging information". (gcc -g1 has debugging info but
5515 @c not line numbers). But it seems complex to try to make that
5516 @c distinction here.
5517 @emph{Warning:} If you use the @code{step} command while control is
5518 within a function that was compiled without debugging information,
5519 execution proceeds until control reaches a function that does have
5520 debugging information. Likewise, it will not step into a function which
5521 is compiled without debugging information. To step through functions
5522 without debugging information, use the @code{stepi} command, described
5526 The @code{step} command only stops at the first instruction of a source
5527 line. This prevents the multiple stops that could otherwise occur in
5528 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5529 to stop if a function that has debugging information is called within
5530 the line. In other words, @code{step} @emph{steps inside} any functions
5531 called within the line.
5533 Also, the @code{step} command only enters a function if there is line
5534 number information for the function. Otherwise it acts like the
5535 @code{next} command. This avoids problems when using @code{cc -gl}
5536 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5537 was any debugging information about the routine.
5539 @item step @var{count}
5540 Continue running as in @code{step}, but do so @var{count} times. If a
5541 breakpoint is reached, or a signal not related to stepping occurs before
5542 @var{count} steps, stepping stops right away.
5545 @kindex n @r{(@code{next})}
5546 @item next @r{[}@var{count}@r{]}
5547 Continue to the next source line in the current (innermost) stack frame.
5548 This is similar to @code{step}, but function calls that appear within
5549 the line of code are executed without stopping. Execution stops when
5550 control reaches a different line of code at the original stack level
5551 that was executing when you gave the @code{next} command. This command
5552 is abbreviated @code{n}.
5554 An argument @var{count} is a repeat count, as for @code{step}.
5557 @c FIX ME!! Do we delete this, or is there a way it fits in with
5558 @c the following paragraph? --- Vctoria
5560 @c @code{next} within a function that lacks debugging information acts like
5561 @c @code{step}, but any function calls appearing within the code of the
5562 @c function are executed without stopping.
5564 The @code{next} command only stops at the first instruction of a
5565 source line. This prevents multiple stops that could otherwise occur in
5566 @code{switch} statements, @code{for} loops, etc.
5568 @kindex set step-mode
5570 @cindex functions without line info, and stepping
5571 @cindex stepping into functions with no line info
5572 @itemx set step-mode on
5573 The @code{set step-mode on} command causes the @code{step} command to
5574 stop at the first instruction of a function which contains no debug line
5575 information rather than stepping over it.
5577 This is useful in cases where you may be interested in inspecting the
5578 machine instructions of a function which has no symbolic info and do not
5579 want @value{GDBN} to automatically skip over this function.
5581 @item set step-mode off
5582 Causes the @code{step} command to step over any functions which contains no
5583 debug information. This is the default.
5585 @item show step-mode
5586 Show whether @value{GDBN} will stop in or step over functions without
5587 source line debug information.
5590 @kindex fin @r{(@code{finish})}
5592 Continue running until just after function in the selected stack frame
5593 returns. Print the returned value (if any). This command can be
5594 abbreviated as @code{fin}.
5596 Contrast this with the @code{return} command (@pxref{Returning,
5597 ,Returning from a Function}).
5600 @kindex u @r{(@code{until})}
5601 @cindex run until specified location
5604 Continue running until a source line past the current line, in the
5605 current stack frame, is reached. This command is used to avoid single
5606 stepping through a loop more than once. It is like the @code{next}
5607 command, except that when @code{until} encounters a jump, it
5608 automatically continues execution until the program counter is greater
5609 than the address of the jump.
5611 This means that when you reach the end of a loop after single stepping
5612 though it, @code{until} makes your program continue execution until it
5613 exits the loop. In contrast, a @code{next} command at the end of a loop
5614 simply steps back to the beginning of the loop, which forces you to step
5615 through the next iteration.
5617 @code{until} always stops your program if it attempts to exit the current
5620 @code{until} may produce somewhat counterintuitive results if the order
5621 of machine code does not match the order of the source lines. For
5622 example, in the following excerpt from a debugging session, the @code{f}
5623 (@code{frame}) command shows that execution is stopped at line
5624 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5628 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5630 (@value{GDBP}) until
5631 195 for ( ; argc > 0; NEXTARG) @{
5634 This happened because, for execution efficiency, the compiler had
5635 generated code for the loop closure test at the end, rather than the
5636 start, of the loop---even though the test in a C @code{for}-loop is
5637 written before the body of the loop. The @code{until} command appeared
5638 to step back to the beginning of the loop when it advanced to this
5639 expression; however, it has not really gone to an earlier
5640 statement---not in terms of the actual machine code.
5642 @code{until} with no argument works by means of single
5643 instruction stepping, and hence is slower than @code{until} with an
5646 @item until @var{location}
5647 @itemx u @var{location}
5648 Continue running your program until either the specified @var{location} is
5649 reached, or the current stack frame returns. The location is any of
5650 the forms described in @ref{Specify Location}.
5651 This form of the command uses temporary breakpoints, and
5652 hence is quicker than @code{until} without an argument. The specified
5653 location is actually reached only if it is in the current frame. This
5654 implies that @code{until} can be used to skip over recursive function
5655 invocations. For instance in the code below, if the current location is
5656 line @code{96}, issuing @code{until 99} will execute the program up to
5657 line @code{99} in the same invocation of factorial, i.e., after the inner
5658 invocations have returned.
5661 94 int factorial (int value)
5663 96 if (value > 1) @{
5664 97 value *= factorial (value - 1);
5671 @kindex advance @var{location}
5672 @item advance @var{location}
5673 Continue running the program up to the given @var{location}. An argument is
5674 required, which should be of one of the forms described in
5675 @ref{Specify Location}.
5676 Execution will also stop upon exit from the current stack
5677 frame. This command is similar to @code{until}, but @code{advance} will
5678 not skip over recursive function calls, and the target location doesn't
5679 have to be in the same frame as the current one.
5683 @kindex si @r{(@code{stepi})}
5685 @itemx stepi @var{arg}
5687 Execute one machine instruction, then stop and return to the debugger.
5689 It is often useful to do @samp{display/i $pc} when stepping by machine
5690 instructions. This makes @value{GDBN} automatically display the next
5691 instruction to be executed, each time your program stops. @xref{Auto
5692 Display,, Automatic Display}.
5694 An argument is a repeat count, as in @code{step}.
5698 @kindex ni @r{(@code{nexti})}
5700 @itemx nexti @var{arg}
5702 Execute one machine instruction, but if it is a function call,
5703 proceed until the function returns.
5705 An argument is a repeat count, as in @code{next}.
5709 @anchor{range stepping}
5710 @cindex range stepping
5711 @cindex target-assisted range stepping
5712 By default, and if available, @value{GDBN} makes use of
5713 target-assisted @dfn{range stepping}. In other words, whenever you
5714 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5715 tells the target to step the corresponding range of instruction
5716 addresses instead of issuing multiple single-steps. This speeds up
5717 line stepping, particularly for remote targets. Ideally, there should
5718 be no reason you would want to turn range stepping off. However, it's
5719 possible that a bug in the debug info, a bug in the remote stub (for
5720 remote targets), or even a bug in @value{GDBN} could make line
5721 stepping behave incorrectly when target-assisted range stepping is
5722 enabled. You can use the following command to turn off range stepping
5726 @kindex set range-stepping
5727 @kindex show range-stepping
5728 @item set range-stepping
5729 @itemx show range-stepping
5730 Control whether range stepping is enabled.
5732 If @code{on}, and the target supports it, @value{GDBN} tells the
5733 target to step a range of addresses itself, instead of issuing
5734 multiple single-steps. If @code{off}, @value{GDBN} always issues
5735 single-steps, even if range stepping is supported by the target. The
5736 default is @code{on}.
5740 @node Skipping Over Functions and Files
5741 @section Skipping Over Functions and Files
5742 @cindex skipping over functions and files
5744 The program you are debugging may contain some functions which are
5745 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5746 skip a function, all functions in a file or a particular function in
5747 a particular file when stepping.
5749 For example, consider the following C function:
5760 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5761 are not interested in stepping through @code{boring}. If you run @code{step}
5762 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5763 step over both @code{foo} and @code{boring}!
5765 One solution is to @code{step} into @code{boring} and use the @code{finish}
5766 command to immediately exit it. But this can become tedious if @code{boring}
5767 is called from many places.
5769 A more flexible solution is to execute @kbd{skip boring}. This instructs
5770 @value{GDBN} never to step into @code{boring}. Now when you execute
5771 @code{step} at line 103, you'll step over @code{boring} and directly into
5774 Functions may be skipped by providing either a function name, linespec
5775 (@pxref{Specify Location}), regular expression that matches the function's
5776 name, file name or a @code{glob}-style pattern that matches the file name.
5778 On Posix systems the form of the regular expression is
5779 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5780 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5781 expression is whatever is provided by the @code{regcomp} function of
5782 the underlying system.
5783 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5784 description of @code{glob}-style patterns.
5788 @item skip @r{[}@var{options}@r{]}
5789 The basic form of the @code{skip} command takes zero or more options
5790 that specify what to skip.
5791 The @var{options} argument is any useful combination of the following:
5794 @item -file @var{file}
5795 @itemx -fi @var{file}
5796 Functions in @var{file} will be skipped over when stepping.
5798 @item -gfile @var{file-glob-pattern}
5799 @itemx -gfi @var{file-glob-pattern}
5800 @cindex skipping over files via glob-style patterns
5801 Functions in files matching @var{file-glob-pattern} will be skipped
5805 (gdb) skip -gfi utils/*.c
5808 @item -function @var{linespec}
5809 @itemx -fu @var{linespec}
5810 Functions named by @var{linespec} or the function containing the line
5811 named by @var{linespec} will be skipped over when stepping.
5812 @xref{Specify Location}.
5814 @item -rfunction @var{regexp}
5815 @itemx -rfu @var{regexp}
5816 @cindex skipping over functions via regular expressions
5817 Functions whose name matches @var{regexp} will be skipped over when stepping.
5819 This form is useful for complex function names.
5820 For example, there is generally no need to step into C@t{++} @code{std::string}
5821 constructors or destructors. Plus with C@t{++} templates it can be hard to
5822 write out the full name of the function, and often it doesn't matter what
5823 the template arguments are. Specifying the function to be skipped as a
5824 regular expression makes this easier.
5827 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5830 If you want to skip every templated C@t{++} constructor and destructor
5831 in the @code{std} namespace you can do:
5834 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5838 If no options are specified, the function you're currently debugging
5841 @kindex skip function
5842 @item skip function @r{[}@var{linespec}@r{]}
5843 After running this command, the function named by @var{linespec} or the
5844 function containing the line named by @var{linespec} will be skipped over when
5845 stepping. @xref{Specify Location}.
5847 If you do not specify @var{linespec}, the function you're currently debugging
5850 (If you have a function called @code{file} that you want to skip, use
5851 @kbd{skip function file}.)
5854 @item skip file @r{[}@var{filename}@r{]}
5855 After running this command, any function whose source lives in @var{filename}
5856 will be skipped over when stepping.
5859 (gdb) skip file boring.c
5860 File boring.c will be skipped when stepping.
5863 If you do not specify @var{filename}, functions whose source lives in the file
5864 you're currently debugging will be skipped.
5867 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5868 These are the commands for managing your list of skips:
5872 @item info skip @r{[}@var{range}@r{]}
5873 Print details about the specified skip(s). If @var{range} is not specified,
5874 print a table with details about all functions and files marked for skipping.
5875 @code{info skip} prints the following information about each skip:
5879 A number identifying this skip.
5880 @item Enabled or Disabled
5881 Enabled skips are marked with @samp{y}.
5882 Disabled skips are marked with @samp{n}.
5884 If the file name is a @samp{glob} pattern this is @samp{y}.
5885 Otherwise it is @samp{n}.
5887 The name or @samp{glob} pattern of the file to be skipped.
5888 If no file is specified this is @samp{<none>}.
5890 If the function name is a @samp{regular expression} this is @samp{y}.
5891 Otherwise it is @samp{n}.
5893 The name or regular expression of the function to skip.
5894 If no function is specified this is @samp{<none>}.
5898 @item skip delete @r{[}@var{range}@r{]}
5899 Delete the specified skip(s). If @var{range} is not specified, delete all
5903 @item skip enable @r{[}@var{range}@r{]}
5904 Enable the specified skip(s). If @var{range} is not specified, enable all
5907 @kindex skip disable
5908 @item skip disable @r{[}@var{range}@r{]}
5909 Disable the specified skip(s). If @var{range} is not specified, disable all
5912 @kindex set debug skip
5913 @item set debug skip @r{[}on|off@r{]}
5914 Set whether to print the debug output about skipping files and functions.
5916 @kindex show debug skip
5917 @item show debug skip
5918 Show whether the debug output about skipping files and functions is printed.
5926 A signal is an asynchronous event that can happen in a program. The
5927 operating system defines the possible kinds of signals, and gives each
5928 kind a name and a number. For example, in Unix @code{SIGINT} is the
5929 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5930 @code{SIGSEGV} is the signal a program gets from referencing a place in
5931 memory far away from all the areas in use; @code{SIGALRM} occurs when
5932 the alarm clock timer goes off (which happens only if your program has
5933 requested an alarm).
5935 @cindex fatal signals
5936 Some signals, including @code{SIGALRM}, are a normal part of the
5937 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5938 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5939 program has not specified in advance some other way to handle the signal.
5940 @code{SIGINT} does not indicate an error in your program, but it is normally
5941 fatal so it can carry out the purpose of the interrupt: to kill the program.
5943 @value{GDBN} has the ability to detect any occurrence of a signal in your
5944 program. You can tell @value{GDBN} in advance what to do for each kind of
5947 @cindex handling signals
5948 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5949 @code{SIGALRM} be silently passed to your program
5950 (so as not to interfere with their role in the program's functioning)
5951 but to stop your program immediately whenever an error signal happens.
5952 You can change these settings with the @code{handle} command.
5955 @kindex info signals
5959 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5960 handle each one. You can use this to see the signal numbers of all
5961 the defined types of signals.
5963 @item info signals @var{sig}
5964 Similar, but print information only about the specified signal number.
5966 @code{info handle} is an alias for @code{info signals}.
5968 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5969 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5970 for details about this command.
5973 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5974 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5975 can be the number of a signal or its name (with or without the
5976 @samp{SIG} at the beginning); a list of signal numbers of the form
5977 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5978 known signals. Optional arguments @var{keywords}, described below,
5979 say what change to make.
5983 The keywords allowed by the @code{handle} command can be abbreviated.
5984 Their full names are:
5988 @value{GDBN} should not stop your program when this signal happens. It may
5989 still print a message telling you that the signal has come in.
5992 @value{GDBN} should stop your program when this signal happens. This implies
5993 the @code{print} keyword as well.
5996 @value{GDBN} should print a message when this signal happens.
5999 @value{GDBN} should not mention the occurrence of the signal at all. This
6000 implies the @code{nostop} keyword as well.
6004 @value{GDBN} should allow your program to see this signal; your program
6005 can handle the signal, or else it may terminate if the signal is fatal
6006 and not handled. @code{pass} and @code{noignore} are synonyms.
6010 @value{GDBN} should not allow your program to see this signal.
6011 @code{nopass} and @code{ignore} are synonyms.
6015 When a signal stops your program, the signal is not visible to the
6017 continue. Your program sees the signal then, if @code{pass} is in
6018 effect for the signal in question @emph{at that time}. In other words,
6019 after @value{GDBN} reports a signal, you can use the @code{handle}
6020 command with @code{pass} or @code{nopass} to control whether your
6021 program sees that signal when you continue.
6023 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6024 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6025 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6028 You can also use the @code{signal} command to prevent your program from
6029 seeing a signal, or cause it to see a signal it normally would not see,
6030 or to give it any signal at any time. For example, if your program stopped
6031 due to some sort of memory reference error, you might store correct
6032 values into the erroneous variables and continue, hoping to see more
6033 execution; but your program would probably terminate immediately as
6034 a result of the fatal signal once it saw the signal. To prevent this,
6035 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6038 @cindex stepping and signal handlers
6039 @anchor{stepping and signal handlers}
6041 @value{GDBN} optimizes for stepping the mainline code. If a signal
6042 that has @code{handle nostop} and @code{handle pass} set arrives while
6043 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6044 in progress, @value{GDBN} lets the signal handler run and then resumes
6045 stepping the mainline code once the signal handler returns. In other
6046 words, @value{GDBN} steps over the signal handler. This prevents
6047 signals that you've specified as not interesting (with @code{handle
6048 nostop}) from changing the focus of debugging unexpectedly. Note that
6049 the signal handler itself may still hit a breakpoint, stop for another
6050 signal that has @code{handle stop} in effect, or for any other event
6051 that normally results in stopping the stepping command sooner. Also
6052 note that @value{GDBN} still informs you that the program received a
6053 signal if @code{handle print} is set.
6055 @anchor{stepping into signal handlers}
6057 If you set @code{handle pass} for a signal, and your program sets up a
6058 handler for it, then issuing a stepping command, such as @code{step}
6059 or @code{stepi}, when your program is stopped due to the signal will
6060 step @emph{into} the signal handler (if the target supports that).
6062 Likewise, if you use the @code{queue-signal} command to queue a signal
6063 to be delivered to the current thread when execution of the thread
6064 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6065 stepping command will step into the signal handler.
6067 Here's an example, using @code{stepi} to step to the first instruction
6068 of @code{SIGUSR1}'s handler:
6071 (@value{GDBP}) handle SIGUSR1
6072 Signal Stop Print Pass to program Description
6073 SIGUSR1 Yes Yes Yes User defined signal 1
6077 Program received signal SIGUSR1, User defined signal 1.
6078 main () sigusr1.c:28
6081 sigusr1_handler () at sigusr1.c:9
6085 The same, but using @code{queue-signal} instead of waiting for the
6086 program to receive the signal first:
6091 (@value{GDBP}) queue-signal SIGUSR1
6093 sigusr1_handler () at sigusr1.c:9
6098 @cindex extra signal information
6099 @anchor{extra signal information}
6101 On some targets, @value{GDBN} can inspect extra signal information
6102 associated with the intercepted signal, before it is actually
6103 delivered to the program being debugged. This information is exported
6104 by the convenience variable @code{$_siginfo}, and consists of data
6105 that is passed by the kernel to the signal handler at the time of the
6106 receipt of a signal. The data type of the information itself is
6107 target dependent. You can see the data type using the @code{ptype
6108 $_siginfo} command. On Unix systems, it typically corresponds to the
6109 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6112 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6113 referenced address that raised a segmentation fault.
6117 (@value{GDBP}) continue
6118 Program received signal SIGSEGV, Segmentation fault.
6119 0x0000000000400766 in main ()
6121 (@value{GDBP}) ptype $_siginfo
6128 struct @{...@} _kill;
6129 struct @{...@} _timer;
6131 struct @{...@} _sigchld;
6132 struct @{...@} _sigfault;
6133 struct @{...@} _sigpoll;
6136 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6140 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6141 $1 = (void *) 0x7ffff7ff7000
6145 Depending on target support, @code{$_siginfo} may also be writable.
6147 @cindex Intel MPX boundary violations
6148 @cindex boundary violations, Intel MPX
6149 On some targets, a @code{SIGSEGV} can be caused by a boundary
6150 violation, i.e., accessing an address outside of the allowed range.
6151 In those cases @value{GDBN} may displays additional information,
6152 depending on how @value{GDBN} has been told to handle the signal.
6153 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6154 kind: "Upper" or "Lower", the memory address accessed and the
6155 bounds, while with @code{handle nostop SIGSEGV} no additional
6156 information is displayed.
6158 The usual output of a segfault is:
6160 Program received signal SIGSEGV, Segmentation fault
6161 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6162 68 value = *(p + len);
6165 While a bound violation is presented as:
6167 Program received signal SIGSEGV, Segmentation fault
6168 Upper bound violation while accessing address 0x7fffffffc3b3
6169 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6170 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6171 68 value = *(p + len);
6175 @section Stopping and Starting Multi-thread Programs
6177 @cindex stopped threads
6178 @cindex threads, stopped
6180 @cindex continuing threads
6181 @cindex threads, continuing
6183 @value{GDBN} supports debugging programs with multiple threads
6184 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6185 are two modes of controlling execution of your program within the
6186 debugger. In the default mode, referred to as @dfn{all-stop mode},
6187 when any thread in your program stops (for example, at a breakpoint
6188 or while being stepped), all other threads in the program are also stopped by
6189 @value{GDBN}. On some targets, @value{GDBN} also supports
6190 @dfn{non-stop mode}, in which other threads can continue to run freely while
6191 you examine the stopped thread in the debugger.
6194 * All-Stop Mode:: All threads stop when GDB takes control
6195 * Non-Stop Mode:: Other threads continue to execute
6196 * Background Execution:: Running your program asynchronously
6197 * Thread-Specific Breakpoints:: Controlling breakpoints
6198 * Interrupted System Calls:: GDB may interfere with system calls
6199 * Observer Mode:: GDB does not alter program behavior
6203 @subsection All-Stop Mode
6205 @cindex all-stop mode
6207 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6208 @emph{all} threads of execution stop, not just the current thread. This
6209 allows you to examine the overall state of the program, including
6210 switching between threads, without worrying that things may change
6213 Conversely, whenever you restart the program, @emph{all} threads start
6214 executing. @emph{This is true even when single-stepping} with commands
6215 like @code{step} or @code{next}.
6217 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6218 Since thread scheduling is up to your debugging target's operating
6219 system (not controlled by @value{GDBN}), other threads may
6220 execute more than one statement while the current thread completes a
6221 single step. Moreover, in general other threads stop in the middle of a
6222 statement, rather than at a clean statement boundary, when the program
6225 You might even find your program stopped in another thread after
6226 continuing or even single-stepping. This happens whenever some other
6227 thread runs into a breakpoint, a signal, or an exception before the
6228 first thread completes whatever you requested.
6230 @cindex automatic thread selection
6231 @cindex switching threads automatically
6232 @cindex threads, automatic switching
6233 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6234 signal, it automatically selects the thread where that breakpoint or
6235 signal happened. @value{GDBN} alerts you to the context switch with a
6236 message such as @samp{[Switching to Thread @var{n}]} to identify the
6239 On some OSes, you can modify @value{GDBN}'s default behavior by
6240 locking the OS scheduler to allow only a single thread to run.
6243 @item set scheduler-locking @var{mode}
6244 @cindex scheduler locking mode
6245 @cindex lock scheduler
6246 Set the scheduler locking mode. It applies to normal execution,
6247 record mode, and replay mode. If it is @code{off}, then there is no
6248 locking and any thread may run at any time. If @code{on}, then only
6249 the current thread may run when the inferior is resumed. The
6250 @code{step} mode optimizes for single-stepping; it prevents other
6251 threads from preempting the current thread while you are stepping, so
6252 that the focus of debugging does not change unexpectedly. Other
6253 threads never get a chance to run when you step, and they are
6254 completely free to run when you use commands like @samp{continue},
6255 @samp{until}, or @samp{finish}. However, unless another thread hits a
6256 breakpoint during its timeslice, @value{GDBN} does not change the
6257 current thread away from the thread that you are debugging. The
6258 @code{replay} mode behaves like @code{off} in record mode and like
6259 @code{on} in replay mode.
6261 @item show scheduler-locking
6262 Display the current scheduler locking mode.
6265 @cindex resume threads of multiple processes simultaneously
6266 By default, when you issue one of the execution commands such as
6267 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6268 threads of the current inferior to run. For example, if @value{GDBN}
6269 is attached to two inferiors, each with two threads, the
6270 @code{continue} command resumes only the two threads of the current
6271 inferior. This is useful, for example, when you debug a program that
6272 forks and you want to hold the parent stopped (so that, for instance,
6273 it doesn't run to exit), while you debug the child. In other
6274 situations, you may not be interested in inspecting the current state
6275 of any of the processes @value{GDBN} is attached to, and you may want
6276 to resume them all until some breakpoint is hit. In the latter case,
6277 you can instruct @value{GDBN} to allow all threads of all the
6278 inferiors to run with the @w{@code{set schedule-multiple}} command.
6281 @kindex set schedule-multiple
6282 @item set schedule-multiple
6283 Set the mode for allowing threads of multiple processes to be resumed
6284 when an execution command is issued. When @code{on}, all threads of
6285 all processes are allowed to run. When @code{off}, only the threads
6286 of the current process are resumed. The default is @code{off}. The
6287 @code{scheduler-locking} mode takes precedence when set to @code{on},
6288 or while you are stepping and set to @code{step}.
6290 @item show schedule-multiple
6291 Display the current mode for resuming the execution of threads of
6296 @subsection Non-Stop Mode
6298 @cindex non-stop mode
6300 @c This section is really only a place-holder, and needs to be expanded
6301 @c with more details.
6303 For some multi-threaded targets, @value{GDBN} supports an optional
6304 mode of operation in which you can examine stopped program threads in
6305 the debugger while other threads continue to execute freely. This
6306 minimizes intrusion when debugging live systems, such as programs
6307 where some threads have real-time constraints or must continue to
6308 respond to external events. This is referred to as @dfn{non-stop} mode.
6310 In non-stop mode, when a thread stops to report a debugging event,
6311 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6312 threads as well, in contrast to the all-stop mode behavior. Additionally,
6313 execution commands such as @code{continue} and @code{step} apply by default
6314 only to the current thread in non-stop mode, rather than all threads as
6315 in all-stop mode. This allows you to control threads explicitly in
6316 ways that are not possible in all-stop mode --- for example, stepping
6317 one thread while allowing others to run freely, stepping
6318 one thread while holding all others stopped, or stepping several threads
6319 independently and simultaneously.
6321 To enter non-stop mode, use this sequence of commands before you run
6322 or attach to your program:
6325 # If using the CLI, pagination breaks non-stop.
6328 # Finally, turn it on!
6332 You can use these commands to manipulate the non-stop mode setting:
6335 @kindex set non-stop
6336 @item set non-stop on
6337 Enable selection of non-stop mode.
6338 @item set non-stop off
6339 Disable selection of non-stop mode.
6340 @kindex show non-stop
6342 Show the current non-stop enablement setting.
6345 Note these commands only reflect whether non-stop mode is enabled,
6346 not whether the currently-executing program is being run in non-stop mode.
6347 In particular, the @code{set non-stop} preference is only consulted when
6348 @value{GDBN} starts or connects to the target program, and it is generally
6349 not possible to switch modes once debugging has started. Furthermore,
6350 since not all targets support non-stop mode, even when you have enabled
6351 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6354 In non-stop mode, all execution commands apply only to the current thread
6355 by default. That is, @code{continue} only continues one thread.
6356 To continue all threads, issue @code{continue -a} or @code{c -a}.
6358 You can use @value{GDBN}'s background execution commands
6359 (@pxref{Background Execution}) to run some threads in the background
6360 while you continue to examine or step others from @value{GDBN}.
6361 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6362 always executed asynchronously in non-stop mode.
6364 Suspending execution is done with the @code{interrupt} command when
6365 running in the background, or @kbd{Ctrl-c} during foreground execution.
6366 In all-stop mode, this stops the whole process;
6367 but in non-stop mode the interrupt applies only to the current thread.
6368 To stop the whole program, use @code{interrupt -a}.
6370 Other execution commands do not currently support the @code{-a} option.
6372 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6373 that thread current, as it does in all-stop mode. This is because the
6374 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6375 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6376 changed to a different thread just as you entered a command to operate on the
6377 previously current thread.
6379 @node Background Execution
6380 @subsection Background Execution
6382 @cindex foreground execution
6383 @cindex background execution
6384 @cindex asynchronous execution
6385 @cindex execution, foreground, background and asynchronous
6387 @value{GDBN}'s execution commands have two variants: the normal
6388 foreground (synchronous) behavior, and a background
6389 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6390 the program to report that some thread has stopped before prompting for
6391 another command. In background execution, @value{GDBN} immediately gives
6392 a command prompt so that you can issue other commands while your program runs.
6394 If the target doesn't support async mode, @value{GDBN} issues an error
6395 message if you attempt to use the background execution commands.
6397 @cindex @code{&}, background execution of commands
6398 To specify background execution, add a @code{&} to the command. For example,
6399 the background form of the @code{continue} command is @code{continue&}, or
6400 just @code{c&}. The execution commands that accept background execution
6406 @xref{Starting, , Starting your Program}.
6410 @xref{Attach, , Debugging an Already-running Process}.
6414 @xref{Continuing and Stepping, step}.
6418 @xref{Continuing and Stepping, stepi}.
6422 @xref{Continuing and Stepping, next}.
6426 @xref{Continuing and Stepping, nexti}.
6430 @xref{Continuing and Stepping, continue}.
6434 @xref{Continuing and Stepping, finish}.
6438 @xref{Continuing and Stepping, until}.
6442 Background execution is especially useful in conjunction with non-stop
6443 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6444 However, you can also use these commands in the normal all-stop mode with
6445 the restriction that you cannot issue another execution command until the
6446 previous one finishes. Examples of commands that are valid in all-stop
6447 mode while the program is running include @code{help} and @code{info break}.
6449 You can interrupt your program while it is running in the background by
6450 using the @code{interrupt} command.
6457 Suspend execution of the running program. In all-stop mode,
6458 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6459 only the current thread. To stop the whole program in non-stop mode,
6460 use @code{interrupt -a}.
6463 @node Thread-Specific Breakpoints
6464 @subsection Thread-Specific Breakpoints
6466 When your program has multiple threads (@pxref{Threads,, Debugging
6467 Programs with Multiple Threads}), you can choose whether to set
6468 breakpoints on all threads, or on a particular thread.
6471 @cindex breakpoints and threads
6472 @cindex thread breakpoints
6473 @kindex break @dots{} thread @var{thread-id}
6474 @item break @var{location} thread @var{thread-id}
6475 @itemx break @var{location} thread @var{thread-id} if @dots{}
6476 @var{location} specifies source lines; there are several ways of
6477 writing them (@pxref{Specify Location}), but the effect is always to
6478 specify some source line.
6480 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6481 to specify that you only want @value{GDBN} to stop the program when a
6482 particular thread reaches this breakpoint. The @var{thread-id} specifier
6483 is one of the thread identifiers assigned by @value{GDBN}, shown
6484 in the first column of the @samp{info threads} display.
6486 If you do not specify @samp{thread @var{thread-id}} when you set a
6487 breakpoint, the breakpoint applies to @emph{all} threads of your
6490 You can use the @code{thread} qualifier on conditional breakpoints as
6491 well; in this case, place @samp{thread @var{thread-id}} before or
6492 after the breakpoint condition, like this:
6495 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6500 Thread-specific breakpoints are automatically deleted when
6501 @value{GDBN} detects the corresponding thread is no longer in the
6502 thread list. For example:
6506 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6509 There are several ways for a thread to disappear, such as a regular
6510 thread exit, but also when you detach from the process with the
6511 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6512 Process}), or if @value{GDBN} loses the remote connection
6513 (@pxref{Remote Debugging}), etc. Note that with some targets,
6514 @value{GDBN} is only able to detect a thread has exited when the user
6515 explictly asks for the thread list with the @code{info threads}
6518 @node Interrupted System Calls
6519 @subsection Interrupted System Calls
6521 @cindex thread breakpoints and system calls
6522 @cindex system calls and thread breakpoints
6523 @cindex premature return from system calls
6524 There is an unfortunate side effect when using @value{GDBN} to debug
6525 multi-threaded programs. If one thread stops for a
6526 breakpoint, or for some other reason, and another thread is blocked in a
6527 system call, then the system call may return prematurely. This is a
6528 consequence of the interaction between multiple threads and the signals
6529 that @value{GDBN} uses to implement breakpoints and other events that
6532 To handle this problem, your program should check the return value of
6533 each system call and react appropriately. This is good programming
6536 For example, do not write code like this:
6542 The call to @code{sleep} will return early if a different thread stops
6543 at a breakpoint or for some other reason.
6545 Instead, write this:
6550 unslept = sleep (unslept);
6553 A system call is allowed to return early, so the system is still
6554 conforming to its specification. But @value{GDBN} does cause your
6555 multi-threaded program to behave differently than it would without
6558 Also, @value{GDBN} uses internal breakpoints in the thread library to
6559 monitor certain events such as thread creation and thread destruction.
6560 When such an event happens, a system call in another thread may return
6561 prematurely, even though your program does not appear to stop.
6564 @subsection Observer Mode
6566 If you want to build on non-stop mode and observe program behavior
6567 without any chance of disruption by @value{GDBN}, you can set
6568 variables to disable all of the debugger's attempts to modify state,
6569 whether by writing memory, inserting breakpoints, etc. These operate
6570 at a low level, intercepting operations from all commands.
6572 When all of these are set to @code{off}, then @value{GDBN} is said to
6573 be @dfn{observer mode}. As a convenience, the variable
6574 @code{observer} can be set to disable these, plus enable non-stop
6577 Note that @value{GDBN} will not prevent you from making nonsensical
6578 combinations of these settings. For instance, if you have enabled
6579 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6580 then breakpoints that work by writing trap instructions into the code
6581 stream will still not be able to be placed.
6586 @item set observer on
6587 @itemx set observer off
6588 When set to @code{on}, this disables all the permission variables
6589 below (except for @code{insert-fast-tracepoints}), plus enables
6590 non-stop debugging. Setting this to @code{off} switches back to
6591 normal debugging, though remaining in non-stop mode.
6594 Show whether observer mode is on or off.
6596 @kindex may-write-registers
6597 @item set may-write-registers on
6598 @itemx set may-write-registers off
6599 This controls whether @value{GDBN} will attempt to alter the values of
6600 registers, such as with assignment expressions in @code{print}, or the
6601 @code{jump} command. It defaults to @code{on}.
6603 @item show may-write-registers
6604 Show the current permission to write registers.
6606 @kindex may-write-memory
6607 @item set may-write-memory on
6608 @itemx set may-write-memory off
6609 This controls whether @value{GDBN} will attempt to alter the contents
6610 of memory, such as with assignment expressions in @code{print}. It
6611 defaults to @code{on}.
6613 @item show may-write-memory
6614 Show the current permission to write memory.
6616 @kindex may-insert-breakpoints
6617 @item set may-insert-breakpoints on
6618 @itemx set may-insert-breakpoints off
6619 This controls whether @value{GDBN} will attempt to insert breakpoints.
6620 This affects all breakpoints, including internal breakpoints defined
6621 by @value{GDBN}. It defaults to @code{on}.
6623 @item show may-insert-breakpoints
6624 Show the current permission to insert breakpoints.
6626 @kindex may-insert-tracepoints
6627 @item set may-insert-tracepoints on
6628 @itemx set may-insert-tracepoints off
6629 This controls whether @value{GDBN} will attempt to insert (regular)
6630 tracepoints at the beginning of a tracing experiment. It affects only
6631 non-fast tracepoints, fast tracepoints being under the control of
6632 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6634 @item show may-insert-tracepoints
6635 Show the current permission to insert tracepoints.
6637 @kindex may-insert-fast-tracepoints
6638 @item set may-insert-fast-tracepoints on
6639 @itemx set may-insert-fast-tracepoints off
6640 This controls whether @value{GDBN} will attempt to insert fast
6641 tracepoints at the beginning of a tracing experiment. It affects only
6642 fast tracepoints, regular (non-fast) tracepoints being under the
6643 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6645 @item show may-insert-fast-tracepoints
6646 Show the current permission to insert fast tracepoints.
6648 @kindex may-interrupt
6649 @item set may-interrupt on
6650 @itemx set may-interrupt off
6651 This controls whether @value{GDBN} will attempt to interrupt or stop
6652 program execution. When this variable is @code{off}, the
6653 @code{interrupt} command will have no effect, nor will
6654 @kbd{Ctrl-c}. It defaults to @code{on}.
6656 @item show may-interrupt
6657 Show the current permission to interrupt or stop the program.
6661 @node Reverse Execution
6662 @chapter Running programs backward
6663 @cindex reverse execution
6664 @cindex running programs backward
6666 When you are debugging a program, it is not unusual to realize that
6667 you have gone too far, and some event of interest has already happened.
6668 If the target environment supports it, @value{GDBN} can allow you to
6669 ``rewind'' the program by running it backward.
6671 A target environment that supports reverse execution should be able
6672 to ``undo'' the changes in machine state that have taken place as the
6673 program was executing normally. Variables, registers etc.@: should
6674 revert to their previous values. Obviously this requires a great
6675 deal of sophistication on the part of the target environment; not
6676 all target environments can support reverse execution.
6678 When a program is executed in reverse, the instructions that
6679 have most recently been executed are ``un-executed'', in reverse
6680 order. The program counter runs backward, following the previous
6681 thread of execution in reverse. As each instruction is ``un-executed'',
6682 the values of memory and/or registers that were changed by that
6683 instruction are reverted to their previous states. After executing
6684 a piece of source code in reverse, all side effects of that code
6685 should be ``undone'', and all variables should be returned to their
6686 prior values@footnote{
6687 Note that some side effects are easier to undo than others. For instance,
6688 memory and registers are relatively easy, but device I/O is hard. Some
6689 targets may be able undo things like device I/O, and some may not.
6691 The contract between @value{GDBN} and the reverse executing target
6692 requires only that the target do something reasonable when
6693 @value{GDBN} tells it to execute backwards, and then report the
6694 results back to @value{GDBN}. Whatever the target reports back to
6695 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6696 assumes that the memory and registers that the target reports are in a
6697 consistant state, but @value{GDBN} accepts whatever it is given.
6700 On some platforms, @value{GDBN} has built-in support for reverse
6701 execution, activated with the @code{record} or @code{record btrace}
6702 commands. @xref{Process Record and Replay}. Some remote targets,
6703 typically full system emulators, support reverse execution directly
6704 without requiring any special command.
6706 If you are debugging in a target environment that supports
6707 reverse execution, @value{GDBN} provides the following commands.
6710 @kindex reverse-continue
6711 @kindex rc @r{(@code{reverse-continue})}
6712 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6713 @itemx rc @r{[}@var{ignore-count}@r{]}
6714 Beginning at the point where your program last stopped, start executing
6715 in reverse. Reverse execution will stop for breakpoints and synchronous
6716 exceptions (signals), just like normal execution. Behavior of
6717 asynchronous signals depends on the target environment.
6719 @kindex reverse-step
6720 @kindex rs @r{(@code{step})}
6721 @item reverse-step @r{[}@var{count}@r{]}
6722 Run the program backward until control reaches the start of a
6723 different source line; then stop it, and return control to @value{GDBN}.
6725 Like the @code{step} command, @code{reverse-step} will only stop
6726 at the beginning of a source line. It ``un-executes'' the previously
6727 executed source line. If the previous source line included calls to
6728 debuggable functions, @code{reverse-step} will step (backward) into
6729 the called function, stopping at the beginning of the @emph{last}
6730 statement in the called function (typically a return statement).
6732 Also, as with the @code{step} command, if non-debuggable functions are
6733 called, @code{reverse-step} will run thru them backward without stopping.
6735 @kindex reverse-stepi
6736 @kindex rsi @r{(@code{reverse-stepi})}
6737 @item reverse-stepi @r{[}@var{count}@r{]}
6738 Reverse-execute one machine instruction. Note that the instruction
6739 to be reverse-executed is @emph{not} the one pointed to by the program
6740 counter, but the instruction executed prior to that one. For instance,
6741 if the last instruction was a jump, @code{reverse-stepi} will take you
6742 back from the destination of the jump to the jump instruction itself.
6744 @kindex reverse-next
6745 @kindex rn @r{(@code{reverse-next})}
6746 @item reverse-next @r{[}@var{count}@r{]}
6747 Run backward to the beginning of the previous line executed in
6748 the current (innermost) stack frame. If the line contains function
6749 calls, they will be ``un-executed'' without stopping. Starting from
6750 the first line of a function, @code{reverse-next} will take you back
6751 to the caller of that function, @emph{before} the function was called,
6752 just as the normal @code{next} command would take you from the last
6753 line of a function back to its return to its caller
6754 @footnote{Unless the code is too heavily optimized.}.
6756 @kindex reverse-nexti
6757 @kindex rni @r{(@code{reverse-nexti})}
6758 @item reverse-nexti @r{[}@var{count}@r{]}
6759 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6760 in reverse, except that called functions are ``un-executed'' atomically.
6761 That is, if the previously executed instruction was a return from
6762 another function, @code{reverse-nexti} will continue to execute
6763 in reverse until the call to that function (from the current stack
6766 @kindex reverse-finish
6767 @item reverse-finish
6768 Just as the @code{finish} command takes you to the point where the
6769 current function returns, @code{reverse-finish} takes you to the point
6770 where it was called. Instead of ending up at the end of the current
6771 function invocation, you end up at the beginning.
6773 @kindex set exec-direction
6774 @item set exec-direction
6775 Set the direction of target execution.
6776 @item set exec-direction reverse
6777 @cindex execute forward or backward in time
6778 @value{GDBN} will perform all execution commands in reverse, until the
6779 exec-direction mode is changed to ``forward''. Affected commands include
6780 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6781 command cannot be used in reverse mode.
6782 @item set exec-direction forward
6783 @value{GDBN} will perform all execution commands in the normal fashion.
6784 This is the default.
6788 @node Process Record and Replay
6789 @chapter Recording Inferior's Execution and Replaying It
6790 @cindex process record and replay
6791 @cindex recording inferior's execution and replaying it
6793 On some platforms, @value{GDBN} provides a special @dfn{process record
6794 and replay} target that can record a log of the process execution, and
6795 replay it later with both forward and reverse execution commands.
6798 When this target is in use, if the execution log includes the record
6799 for the next instruction, @value{GDBN} will debug in @dfn{replay
6800 mode}. In the replay mode, the inferior does not really execute code
6801 instructions. Instead, all the events that normally happen during
6802 code execution are taken from the execution log. While code is not
6803 really executed in replay mode, the values of registers (including the
6804 program counter register) and the memory of the inferior are still
6805 changed as they normally would. Their contents are taken from the
6809 If the record for the next instruction is not in the execution log,
6810 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6811 inferior executes normally, and @value{GDBN} records the execution log
6814 The process record and replay target supports reverse execution
6815 (@pxref{Reverse Execution}), even if the platform on which the
6816 inferior runs does not. However, the reverse execution is limited in
6817 this case by the range of the instructions recorded in the execution
6818 log. In other words, reverse execution on platforms that don't
6819 support it directly can only be done in the replay mode.
6821 When debugging in the reverse direction, @value{GDBN} will work in
6822 replay mode as long as the execution log includes the record for the
6823 previous instruction; otherwise, it will work in record mode, if the
6824 platform supports reverse execution, or stop if not.
6826 Currently, process record and replay is supported on ARM, Aarch64,
6827 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
6828 GNU/Linux. Process record and replay can be used both when native
6829 debugging, and when remote debugging via @code{gdbserver}.
6831 For architecture environments that support process record and replay,
6832 @value{GDBN} provides the following commands:
6835 @kindex target record
6836 @kindex target record-full
6837 @kindex target record-btrace
6840 @kindex record btrace
6841 @kindex record btrace bts
6842 @kindex record btrace pt
6848 @kindex rec btrace bts
6849 @kindex rec btrace pt
6852 @item record @var{method}
6853 This command starts the process record and replay target. The
6854 recording method can be specified as parameter. Without a parameter
6855 the command uses the @code{full} recording method. The following
6856 recording methods are available:
6860 Full record/replay recording using @value{GDBN}'s software record and
6861 replay implementation. This method allows replaying and reverse
6864 @item btrace @var{format}
6865 Hardware-supported instruction recording, supported on Intel
6866 processors. This method does not record data. Further, the data is
6867 collected in a ring buffer so old data will be overwritten when the
6868 buffer is full. It allows limited reverse execution. Variables and
6869 registers are not available during reverse execution. In remote
6870 debugging, recording continues on disconnect. Recorded data can be
6871 inspected after reconnecting. The recording may be stopped using
6874 The recording format can be specified as parameter. Without a parameter
6875 the command chooses the recording format. The following recording
6876 formats are available:
6880 @cindex branch trace store
6881 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6882 this format, the processor stores a from/to record for each executed
6883 branch in the btrace ring buffer.
6886 @cindex Intel Processor Trace
6887 Use the @dfn{Intel Processor Trace} recording format. In this
6888 format, the processor stores the execution trace in a compressed form
6889 that is afterwards decoded by @value{GDBN}.
6891 The trace can be recorded with very low overhead. The compressed
6892 trace format also allows small trace buffers to already contain a big
6893 number of instructions compared to @acronym{BTS}.
6895 Decoding the recorded execution trace, on the other hand, is more
6896 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6897 increased number of instructions to process. You should increase the
6898 buffer-size with care.
6901 Not all recording formats may be available on all processors.
6904 The process record and replay target can only debug a process that is
6905 already running. Therefore, you need first to start the process with
6906 the @kbd{run} or @kbd{start} commands, and then start the recording
6907 with the @kbd{record @var{method}} command.
6909 @cindex displaced stepping, and process record and replay
6910 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6911 will be automatically disabled when process record and replay target
6912 is started. That's because the process record and replay target
6913 doesn't support displaced stepping.
6915 @cindex non-stop mode, and process record and replay
6916 @cindex asynchronous execution, and process record and replay
6917 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6918 the asynchronous execution mode (@pxref{Background Execution}), not
6919 all recording methods are available. The @code{full} recording method
6920 does not support these two modes.
6925 Stop the process record and replay target. When process record and
6926 replay target stops, the entire execution log will be deleted and the
6927 inferior will either be terminated, or will remain in its final state.
6929 When you stop the process record and replay target in record mode (at
6930 the end of the execution log), the inferior will be stopped at the
6931 next instruction that would have been recorded. In other words, if
6932 you record for a while and then stop recording, the inferior process
6933 will be left in the same state as if the recording never happened.
6935 On the other hand, if the process record and replay target is stopped
6936 while in replay mode (that is, not at the end of the execution log,
6937 but at some earlier point), the inferior process will become ``live''
6938 at that earlier state, and it will then be possible to continue the
6939 usual ``live'' debugging of the process from that state.
6941 When the inferior process exits, or @value{GDBN} detaches from it,
6942 process record and replay target will automatically stop itself.
6946 Go to a specific location in the execution log. There are several
6947 ways to specify the location to go to:
6950 @item record goto begin
6951 @itemx record goto start
6952 Go to the beginning of the execution log.
6954 @item record goto end
6955 Go to the end of the execution log.
6957 @item record goto @var{n}
6958 Go to instruction number @var{n} in the execution log.
6962 @item record save @var{filename}
6963 Save the execution log to a file @file{@var{filename}}.
6964 Default filename is @file{gdb_record.@var{process_id}}, where
6965 @var{process_id} is the process ID of the inferior.
6967 This command may not be available for all recording methods.
6969 @kindex record restore
6970 @item record restore @var{filename}
6971 Restore the execution log from a file @file{@var{filename}}.
6972 File must have been created with @code{record save}.
6974 @kindex set record full
6975 @item set record full insn-number-max @var{limit}
6976 @itemx set record full insn-number-max unlimited
6977 Set the limit of instructions to be recorded for the @code{full}
6978 recording method. Default value is 200000.
6980 If @var{limit} is a positive number, then @value{GDBN} will start
6981 deleting instructions from the log once the number of the record
6982 instructions becomes greater than @var{limit}. For every new recorded
6983 instruction, @value{GDBN} will delete the earliest recorded
6984 instruction to keep the number of recorded instructions at the limit.
6985 (Since deleting recorded instructions loses information, @value{GDBN}
6986 lets you control what happens when the limit is reached, by means of
6987 the @code{stop-at-limit} option, described below.)
6989 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6990 delete recorded instructions from the execution log. The number of
6991 recorded instructions is limited only by the available memory.
6993 @kindex show record full
6994 @item show record full insn-number-max
6995 Show the limit of instructions to be recorded with the @code{full}
6998 @item set record full stop-at-limit
6999 Control the behavior of the @code{full} recording method when the
7000 number of recorded instructions reaches the limit. If ON (the
7001 default), @value{GDBN} will stop when the limit is reached for the
7002 first time and ask you whether you want to stop the inferior or
7003 continue running it and recording the execution log. If you decide
7004 to continue recording, each new recorded instruction will cause the
7005 oldest one to be deleted.
7007 If this option is OFF, @value{GDBN} will automatically delete the
7008 oldest record to make room for each new one, without asking.
7010 @item show record full stop-at-limit
7011 Show the current setting of @code{stop-at-limit}.
7013 @item set record full memory-query
7014 Control the behavior when @value{GDBN} is unable to record memory
7015 changes caused by an instruction for the @code{full} recording method.
7016 If ON, @value{GDBN} will query whether to stop the inferior in that
7019 If this option is OFF (the default), @value{GDBN} will automatically
7020 ignore the effect of such instructions on memory. Later, when
7021 @value{GDBN} replays this execution log, it will mark the log of this
7022 instruction as not accessible, and it will not affect the replay
7025 @item show record full memory-query
7026 Show the current setting of @code{memory-query}.
7028 @kindex set record btrace
7029 The @code{btrace} record target does not trace data. As a
7030 convenience, when replaying, @value{GDBN} reads read-only memory off
7031 the live program directly, assuming that the addresses of the
7032 read-only areas don't change. This for example makes it possible to
7033 disassemble code while replaying, but not to print variables.
7034 In some cases, being able to inspect variables might be useful.
7035 You can use the following command for that:
7037 @item set record btrace replay-memory-access
7038 Control the behavior of the @code{btrace} recording method when
7039 accessing memory during replay. If @code{read-only} (the default),
7040 @value{GDBN} will only allow accesses to read-only memory.
7041 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7042 and to read-write memory. Beware that the accessed memory corresponds
7043 to the live target and not necessarily to the current replay
7046 @item set record btrace cpu @var{identifier}
7047 Set the processor to be used for enabling workarounds for processor
7048 errata when decoding the trace.
7050 Processor errata are defects in processor operation, caused by its
7051 design or manufacture. They can cause a trace not to match the
7052 specification. This, in turn, may cause trace decode to fail.
7053 @value{GDBN} can detect erroneous trace packets and correct them, thus
7054 avoiding the decoding failures. These corrections are known as
7055 @dfn{errata workarounds}, and are enabled based on the processor on
7056 which the trace was recorded.
7058 By default, @value{GDBN} attempts to detect the processor
7059 automatically, and apply the necessary workarounds for it. However,
7060 you may need to specify the processor if @value{GDBN} does not yet
7061 support it. This command allows you to do that, and also allows to
7062 disable the workarounds.
7064 The argument @var{identifier} identifies the @sc{cpu} and is of the
7065 form: @code{@var{vendor}:@var{procesor identifier}}. In addition,
7066 there are two special identifiers, @code{none} and @code{auto}
7069 The following vendor identifiers and corresponding processor
7070 identifiers are currently supported:
7072 @multitable @columnfractions .1 .9
7075 @tab @var{family}/@var{model}[/@var{stepping}]
7079 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7080 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7082 If @var{identifier} is @code{auto}, enable errata workarounds for the
7083 processor on which the trace was recorded. If @var{identifier} is
7084 @code{none}, errata workarounds are disabled.
7086 For example, when using an old @value{GDBN} on a new system, decode
7087 may fail because @value{GDBN} does not support the new processor. It
7088 often suffices to specify an older processor that @value{GDBN}
7093 Active record target: record-btrace
7094 Recording format: Intel Processor Trace.
7096 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7097 (gdb) set record btrace cpu intel:6/158
7099 Active record target: record-btrace
7100 Recording format: Intel Processor Trace.
7102 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7105 @kindex show record btrace
7106 @item show record btrace replay-memory-access
7107 Show the current setting of @code{replay-memory-access}.
7109 @item show record btrace cpu
7110 Show the processor to be used for enabling trace decode errata
7113 @kindex set record btrace bts
7114 @item set record btrace bts buffer-size @var{size}
7115 @itemx set record btrace bts buffer-size unlimited
7116 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7117 format. Default is 64KB.
7119 If @var{size} is a positive number, then @value{GDBN} will try to
7120 allocate a buffer of at least @var{size} bytes for each new thread
7121 that uses the btrace recording method and the @acronym{BTS} format.
7122 The actually obtained buffer size may differ from the requested
7123 @var{size}. Use the @code{info record} command to see the actual
7124 buffer size for each thread that uses the btrace recording method and
7125 the @acronym{BTS} format.
7127 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7128 allocate a buffer of 4MB.
7130 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7131 also need longer to process the branch trace data before it can be used.
7133 @item show record btrace bts buffer-size @var{size}
7134 Show the current setting of the requested ring buffer size for branch
7135 tracing in @acronym{BTS} format.
7137 @kindex set record btrace pt
7138 @item set record btrace pt buffer-size @var{size}
7139 @itemx set record btrace pt buffer-size unlimited
7140 Set the requested ring buffer size for branch tracing in Intel
7141 Processor Trace format. Default is 16KB.
7143 If @var{size} is a positive number, then @value{GDBN} will try to
7144 allocate a buffer of at least @var{size} bytes for each new thread
7145 that uses the btrace recording method and the Intel Processor Trace
7146 format. The actually obtained buffer size may differ from the
7147 requested @var{size}. Use the @code{info record} command to see the
7148 actual buffer size for each thread.
7150 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7151 allocate a buffer of 4MB.
7153 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7154 also need longer to process the branch trace data before it can be used.
7156 @item show record btrace pt buffer-size @var{size}
7157 Show the current setting of the requested ring buffer size for branch
7158 tracing in Intel Processor Trace format.
7162 Show various statistics about the recording depending on the recording
7167 For the @code{full} recording method, it shows the state of process
7168 record and its in-memory execution log buffer, including:
7172 Whether in record mode or replay mode.
7174 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7176 Highest recorded instruction number.
7178 Current instruction about to be replayed (if in replay mode).
7180 Number of instructions contained in the execution log.
7182 Maximum number of instructions that may be contained in the execution log.
7186 For the @code{btrace} recording method, it shows:
7192 Number of instructions that have been recorded.
7194 Number of blocks of sequential control-flow formed by the recorded
7197 Whether in record mode or replay mode.
7200 For the @code{bts} recording format, it also shows:
7203 Size of the perf ring buffer.
7206 For the @code{pt} recording format, it also shows:
7209 Size of the perf ring buffer.
7213 @kindex record delete
7216 When record target runs in replay mode (``in the past''), delete the
7217 subsequent execution log and begin to record a new execution log starting
7218 from the current address. This means you will abandon the previously
7219 recorded ``future'' and begin recording a new ``future''.
7221 @kindex record instruction-history
7222 @kindex rec instruction-history
7223 @item record instruction-history
7224 Disassembles instructions from the recorded execution log. By
7225 default, ten instructions are disassembled. This can be changed using
7226 the @code{set record instruction-history-size} command. Instructions
7227 are printed in execution order.
7229 It can also print mixed source+disassembly if you specify the the
7230 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7231 as well as in symbolic form by specifying the @code{/r} modifier.
7233 The current position marker is printed for the instruction at the
7234 current program counter value. This instruction can appear multiple
7235 times in the trace and the current position marker will be printed
7236 every time. To omit the current position marker, specify the
7239 To better align the printed instructions when the trace contains
7240 instructions from more than one function, the function name may be
7241 omitted by specifying the @code{/f} modifier.
7243 Speculatively executed instructions are prefixed with @samp{?}. This
7244 feature is not available for all recording formats.
7246 There are several ways to specify what part of the execution log to
7250 @item record instruction-history @var{insn}
7251 Disassembles ten instructions starting from instruction number
7254 @item record instruction-history @var{insn}, +/-@var{n}
7255 Disassembles @var{n} instructions around instruction number
7256 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7257 @var{n} instructions after instruction number @var{insn}. If
7258 @var{n} is preceded with @code{-}, disassembles @var{n}
7259 instructions before instruction number @var{insn}.
7261 @item record instruction-history
7262 Disassembles ten more instructions after the last disassembly.
7264 @item record instruction-history -
7265 Disassembles ten more instructions before the last disassembly.
7267 @item record instruction-history @var{begin}, @var{end}
7268 Disassembles instructions beginning with instruction number
7269 @var{begin} until instruction number @var{end}. The instruction
7270 number @var{end} is included.
7273 This command may not be available for all recording methods.
7276 @item set record instruction-history-size @var{size}
7277 @itemx set record instruction-history-size unlimited
7278 Define how many instructions to disassemble in the @code{record
7279 instruction-history} command. The default value is 10.
7280 A @var{size} of @code{unlimited} means unlimited instructions.
7283 @item show record instruction-history-size
7284 Show how many instructions to disassemble in the @code{record
7285 instruction-history} command.
7287 @kindex record function-call-history
7288 @kindex rec function-call-history
7289 @item record function-call-history
7290 Prints the execution history at function granularity. It prints one
7291 line for each sequence of instructions that belong to the same
7292 function giving the name of that function, the source lines
7293 for this instruction sequence (if the @code{/l} modifier is
7294 specified), and the instructions numbers that form the sequence (if
7295 the @code{/i} modifier is specified). The function names are indented
7296 to reflect the call stack depth if the @code{/c} modifier is
7297 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7301 (@value{GDBP}) @b{list 1, 10}
7312 (@value{GDBP}) @b{record function-call-history /ilc}
7313 1 bar inst 1,4 at foo.c:6,8
7314 2 foo inst 5,10 at foo.c:2,3
7315 3 bar inst 11,13 at foo.c:9,10
7318 By default, ten lines are printed. This can be changed using the
7319 @code{set record function-call-history-size} command. Functions are
7320 printed in execution order. There are several ways to specify what
7324 @item record function-call-history @var{func}
7325 Prints ten functions starting from function number @var{func}.
7327 @item record function-call-history @var{func}, +/-@var{n}
7328 Prints @var{n} functions around function number @var{func}. If
7329 @var{n} is preceded with @code{+}, prints @var{n} functions after
7330 function number @var{func}. If @var{n} is preceded with @code{-},
7331 prints @var{n} functions before function number @var{func}.
7333 @item record function-call-history
7334 Prints ten more functions after the last ten-line print.
7336 @item record function-call-history -
7337 Prints ten more functions before the last ten-line print.
7339 @item record function-call-history @var{begin}, @var{end}
7340 Prints functions beginning with function number @var{begin} until
7341 function number @var{end}. The function number @var{end} is included.
7344 This command may not be available for all recording methods.
7346 @item set record function-call-history-size @var{size}
7347 @itemx set record function-call-history-size unlimited
7348 Define how many lines to print in the
7349 @code{record function-call-history} command. The default value is 10.
7350 A size of @code{unlimited} means unlimited lines.
7352 @item show record function-call-history-size
7353 Show how many lines to print in the
7354 @code{record function-call-history} command.
7359 @chapter Examining the Stack
7361 When your program has stopped, the first thing you need to know is where it
7362 stopped and how it got there.
7365 Each time your program performs a function call, information about the call
7367 That information includes the location of the call in your program,
7368 the arguments of the call,
7369 and the local variables of the function being called.
7370 The information is saved in a block of data called a @dfn{stack frame}.
7371 The stack frames are allocated in a region of memory called the @dfn{call
7374 When your program stops, the @value{GDBN} commands for examining the
7375 stack allow you to see all of this information.
7377 @cindex selected frame
7378 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7379 @value{GDBN} commands refer implicitly to the selected frame. In
7380 particular, whenever you ask @value{GDBN} for the value of a variable in
7381 your program, the value is found in the selected frame. There are
7382 special @value{GDBN} commands to select whichever frame you are
7383 interested in. @xref{Selection, ,Selecting a Frame}.
7385 When your program stops, @value{GDBN} automatically selects the
7386 currently executing frame and describes it briefly, similar to the
7387 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7390 * Frames:: Stack frames
7391 * Backtrace:: Backtraces
7392 * Selection:: Selecting a frame
7393 * Frame Info:: Information on a frame
7394 * Frame Apply:: Applying a command to several frames
7395 * Frame Filter Management:: Managing frame filters
7400 @section Stack Frames
7402 @cindex frame, definition
7404 The call stack is divided up into contiguous pieces called @dfn{stack
7405 frames}, or @dfn{frames} for short; each frame is the data associated
7406 with one call to one function. The frame contains the arguments given
7407 to the function, the function's local variables, and the address at
7408 which the function is executing.
7410 @cindex initial frame
7411 @cindex outermost frame
7412 @cindex innermost frame
7413 When your program is started, the stack has only one frame, that of the
7414 function @code{main}. This is called the @dfn{initial} frame or the
7415 @dfn{outermost} frame. Each time a function is called, a new frame is
7416 made. Each time a function returns, the frame for that function invocation
7417 is eliminated. If a function is recursive, there can be many frames for
7418 the same function. The frame for the function in which execution is
7419 actually occurring is called the @dfn{innermost} frame. This is the most
7420 recently created of all the stack frames that still exist.
7422 @cindex frame pointer
7423 Inside your program, stack frames are identified by their addresses. A
7424 stack frame consists of many bytes, each of which has its own address; each
7425 kind of computer has a convention for choosing one byte whose
7426 address serves as the address of the frame. Usually this address is kept
7427 in a register called the @dfn{frame pointer register}
7428 (@pxref{Registers, $fp}) while execution is going on in that frame.
7431 @cindex frame number
7432 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
7433 number that is zero for the innermost frame, one for the frame that
7434 called it, and so on upward. These level numbers give you a way of
7435 designating stack frames in @value{GDBN} commands. The terms
7436 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
7437 describe this number.
7439 @c The -fomit-frame-pointer below perennially causes hbox overflow
7440 @c underflow problems.
7441 @cindex frameless execution
7442 Some compilers provide a way to compile functions so that they operate
7443 without stack frames. (For example, the @value{NGCC} option
7445 @samp{-fomit-frame-pointer}
7447 generates functions without a frame.)
7448 This is occasionally done with heavily used library functions to save
7449 the frame setup time. @value{GDBN} has limited facilities for dealing
7450 with these function invocations. If the innermost function invocation
7451 has no stack frame, @value{GDBN} nevertheless regards it as though
7452 it had a separate frame, which is numbered zero as usual, allowing
7453 correct tracing of the function call chain. However, @value{GDBN} has
7454 no provision for frameless functions elsewhere in the stack.
7460 @cindex call stack traces
7461 A backtrace is a summary of how your program got where it is. It shows one
7462 line per frame, for many frames, starting with the currently executing
7463 frame (frame zero), followed by its caller (frame one), and on up the
7466 @anchor{backtrace-command}
7468 @kindex bt @r{(@code{backtrace})}
7469 To print a backtrace of the entire stack, use the @code{backtrace}
7470 command, or its alias @code{bt}. This command will print one line per
7471 frame for frames in the stack. By default, all stack frames are
7472 printed. You can stop the backtrace at any time by typing the system
7473 interrupt character, normally @kbd{Ctrl-c}.
7476 @item backtrace [@var{args}@dots{}]
7477 @itemx bt [@var{args}@dots{}]
7478 Print the backtrace of the entire stack. The optional @var{args} can
7479 be one of the following:
7484 Print only the innermost @var{n} frames, where @var{n} is a positive
7489 Print only the outermost @var{n} frames, where @var{n} is a positive
7493 Print the values of the local variables also. This can be combined
7494 with a number to limit the number of frames shown.
7497 Do not run Python frame filters on this backtrace. @xref{Frame
7498 Filter API}, for more information. Additionally use @ref{disable
7499 frame-filter all} to turn off all frame filters. This is only
7500 relevant when @value{GDBN} has been configured with @code{Python}
7504 A Python frame filter might decide to ``elide'' some frames. Normally
7505 such elided frames are still printed, but they are indented relative
7506 to the filtered frames that cause them to be elided. The @code{hide}
7507 option causes elided frames to not be printed at all.
7513 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7514 are additional aliases for @code{backtrace}.
7516 @cindex multiple threads, backtrace
7517 In a multi-threaded program, @value{GDBN} by default shows the
7518 backtrace only for the current thread. To display the backtrace for
7519 several or all of the threads, use the command @code{thread apply}
7520 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7521 apply all backtrace}, @value{GDBN} will display the backtrace for all
7522 the threads; this is handy when you debug a core dump of a
7523 multi-threaded program.
7525 Each line in the backtrace shows the frame number and the function name.
7526 The program counter value is also shown---unless you use @code{set
7527 print address off}. The backtrace also shows the source file name and
7528 line number, as well as the arguments to the function. The program
7529 counter value is omitted if it is at the beginning of the code for that
7532 Here is an example of a backtrace. It was made with the command
7533 @samp{bt 3}, so it shows the innermost three frames.
7537 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7539 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7540 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7542 (More stack frames follow...)
7547 The display for frame zero does not begin with a program counter
7548 value, indicating that your program has stopped at the beginning of the
7549 code for line @code{993} of @code{builtin.c}.
7552 The value of parameter @code{data} in frame 1 has been replaced by
7553 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7554 only if it is a scalar (integer, pointer, enumeration, etc). See command
7555 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7556 on how to configure the way function parameter values are printed.
7558 @cindex optimized out, in backtrace
7559 @cindex function call arguments, optimized out
7560 If your program was compiled with optimizations, some compilers will
7561 optimize away arguments passed to functions if those arguments are
7562 never used after the call. Such optimizations generate code that
7563 passes arguments through registers, but doesn't store those arguments
7564 in the stack frame. @value{GDBN} has no way of displaying such
7565 arguments in stack frames other than the innermost one. Here's what
7566 such a backtrace might look like:
7570 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7572 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7573 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7575 (More stack frames follow...)
7580 The values of arguments that were not saved in their stack frames are
7581 shown as @samp{<optimized out>}.
7583 If you need to display the values of such optimized-out arguments,
7584 either deduce that from other variables whose values depend on the one
7585 you are interested in, or recompile without optimizations.
7587 @cindex backtrace beyond @code{main} function
7588 @cindex program entry point
7589 @cindex startup code, and backtrace
7590 Most programs have a standard user entry point---a place where system
7591 libraries and startup code transition into user code. For C this is
7592 @code{main}@footnote{
7593 Note that embedded programs (the so-called ``free-standing''
7594 environment) are not required to have a @code{main} function as the
7595 entry point. They could even have multiple entry points.}.
7596 When @value{GDBN} finds the entry function in a backtrace
7597 it will terminate the backtrace, to avoid tracing into highly
7598 system-specific (and generally uninteresting) code.
7600 If you need to examine the startup code, or limit the number of levels
7601 in a backtrace, you can change this behavior:
7604 @item set backtrace past-main
7605 @itemx set backtrace past-main on
7606 @kindex set backtrace
7607 Backtraces will continue past the user entry point.
7609 @item set backtrace past-main off
7610 Backtraces will stop when they encounter the user entry point. This is the
7613 @item show backtrace past-main
7614 @kindex show backtrace
7615 Display the current user entry point backtrace policy.
7617 @item set backtrace past-entry
7618 @itemx set backtrace past-entry on
7619 Backtraces will continue past the internal entry point of an application.
7620 This entry point is encoded by the linker when the application is built,
7621 and is likely before the user entry point @code{main} (or equivalent) is called.
7623 @item set backtrace past-entry off
7624 Backtraces will stop when they encounter the internal entry point of an
7625 application. This is the default.
7627 @item show backtrace past-entry
7628 Display the current internal entry point backtrace policy.
7630 @item set backtrace limit @var{n}
7631 @itemx set backtrace limit 0
7632 @itemx set backtrace limit unlimited
7633 @cindex backtrace limit
7634 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7635 or zero means unlimited levels.
7637 @item show backtrace limit
7638 Display the current limit on backtrace levels.
7641 You can control how file names are displayed.
7644 @item set filename-display
7645 @itemx set filename-display relative
7646 @cindex filename-display
7647 Display file names relative to the compilation directory. This is the default.
7649 @item set filename-display basename
7650 Display only basename of a filename.
7652 @item set filename-display absolute
7653 Display an absolute filename.
7655 @item show filename-display
7656 Show the current way to display filenames.
7660 @section Selecting a Frame
7662 Most commands for examining the stack and other data in your program work on
7663 whichever stack frame is selected at the moment. Here are the commands for
7664 selecting a stack frame; all of them finish by printing a brief description
7665 of the stack frame just selected.
7668 @kindex frame@r{, selecting}
7669 @kindex f @r{(@code{frame})}
7670 @item frame @r{[} @var{frame-selection-spec} @r{]}
7671 @item f @r{[} @var{frame-selection-spec} @r{]}
7672 The @command{frame} command allows different stack frames to be
7673 selected. The @var{frame-selection-spec} can be any of the following:
7678 @item level @var{num}
7679 Select frame level @var{num}. Recall that frame zero is the innermost
7680 (currently executing) frame, frame one is the frame that called the
7681 innermost one, and so on. The highest level frame is usually the one
7684 As this is the most common method of navigating the frame stack, the
7685 string @command{level} can be omitted. For example, the following two
7686 commands are equivalent:
7689 (@value{GDBP}) frame 3
7690 (@value{GDBP}) frame level 3
7693 @kindex frame address
7694 @item address @var{stack-address}
7695 Select the frame with stack address @var{stack-address}. The
7696 @var{stack-address} for a frame can be seen in the output of
7697 @command{info frame}, for example:
7701 Stack level 1, frame at 0x7fffffffda30:
7702 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
7703 tail call frame, caller of frame at 0x7fffffffda30
7704 source language c++.
7705 Arglist at unknown address.
7706 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
7709 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
7710 indicated by the line:
7713 Stack level 1, frame at 0x7fffffffda30:
7716 @kindex frame function
7717 @item function @var{function-name}
7718 Select the stack frame for function @var{function-name}. If there are
7719 multiple stack frames for function @var{function-name} then the inner
7720 most stack frame is selected.
7723 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
7724 View a frame that is not part of @value{GDBN}'s backtrace. The frame
7725 viewed has stack address @var{stack-addr}, and optionally, a program
7726 counter address of @var{pc-addr}.
7728 This is useful mainly if the chaining of stack frames has been
7729 damaged by a bug, making it impossible for @value{GDBN} to assign
7730 numbers properly to all frames. In addition, this can be useful
7731 when your program has multiple stacks and switches between them.
7733 When viewing a frame outside the current backtrace using
7734 @command{frame view} then you can always return to the original
7735 stack using one of the previous stack frame selection instructions,
7736 for example @command{frame level 0}.
7742 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7743 numbers @var{n}, this advances toward the outermost frame, to higher
7744 frame numbers, to frames that have existed longer.
7747 @kindex do @r{(@code{down})}
7749 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7750 positive numbers @var{n}, this advances toward the innermost frame, to
7751 lower frame numbers, to frames that were created more recently.
7752 You may abbreviate @code{down} as @code{do}.
7755 All of these commands end by printing two lines of output describing the
7756 frame. The first line shows the frame number, the function name, the
7757 arguments, and the source file and line number of execution in that
7758 frame. The second line shows the text of that source line.
7766 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7768 10 read_input_file (argv[i]);
7772 After such a printout, the @code{list} command with no arguments
7773 prints ten lines centered on the point of execution in the frame.
7774 You can also edit the program at the point of execution with your favorite
7775 editing program by typing @code{edit}.
7776 @xref{List, ,Printing Source Lines},
7780 @kindex select-frame
7781 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
7782 The @code{select-frame} command is a variant of @code{frame} that does
7783 not display the new frame after selecting it. This command is
7784 intended primarily for use in @value{GDBN} command scripts, where the
7785 output might be unnecessary and distracting. The
7786 @var{frame-selection-spec} is as for the @command{frame} command
7787 described in @ref{Selection, ,Selecting a Frame}.
7789 @kindex down-silently
7791 @item up-silently @var{n}
7792 @itemx down-silently @var{n}
7793 These two commands are variants of @code{up} and @code{down},
7794 respectively; they differ in that they do their work silently, without
7795 causing display of the new frame. They are intended primarily for use
7796 in @value{GDBN} command scripts, where the output might be unnecessary and
7801 @section Information About a Frame
7803 There are several other commands to print information about the selected
7809 When used without any argument, this command does not change which
7810 frame is selected, but prints a brief description of the currently
7811 selected stack frame. It can be abbreviated @code{f}. With an
7812 argument, this command is used to select a stack frame.
7813 @xref{Selection, ,Selecting a Frame}.
7816 @kindex info f @r{(@code{info frame})}
7819 This command prints a verbose description of the selected stack frame,
7824 the address of the frame
7826 the address of the next frame down (called by this frame)
7828 the address of the next frame up (caller of this frame)
7830 the language in which the source code corresponding to this frame is written
7832 the address of the frame's arguments
7834 the address of the frame's local variables
7836 the program counter saved in it (the address of execution in the caller frame)
7838 which registers were saved in the frame
7841 @noindent The verbose description is useful when
7842 something has gone wrong that has made the stack format fail to fit
7843 the usual conventions.
7845 @item info frame @r{[} @var{frame-selection-spec} @r{]}
7846 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
7847 Print a verbose description of the frame selected by
7848 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
7849 same as for the @command{frame} command (@pxref{Selection, ,Selecting
7850 a Frame}). The selected frame remains unchanged by this command.
7853 @item info args [-q]
7854 Print the arguments of the selected frame, each on a separate line.
7856 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
7857 printing header information and messages explaining why no argument
7860 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
7861 Like @kbd{info args}, but only print the arguments selected
7862 with the provided regexp(s).
7864 If @var{regexp} is provided, print only the arguments whose names
7865 match the regular expression @var{regexp}.
7867 If @var{type_regexp} is provided, print only the arguments whose
7868 types, as printed by the @code{whatis} command, match
7869 the regular expression @var{type_regexp}.
7870 If @var{type_regexp} contains space(s), it should be enclosed in
7871 quote characters. If needed, use backslash to escape the meaning
7872 of special characters or quotes.
7874 If both @var{regexp} and @var{type_regexp} are provided, an argument
7875 is printed only if its name matches @var{regexp} and its type matches
7878 @item info locals [-q]
7880 Print the local variables of the selected frame, each on a separate
7881 line. These are all variables (declared either static or automatic)
7882 accessible at the point of execution of the selected frame.
7884 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
7885 printing header information and messages explaining why no local variables
7888 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
7889 Like @kbd{info locals}, but only print the local variables selected
7890 with the provided regexp(s).
7892 If @var{regexp} is provided, print only the local variables whose names
7893 match the regular expression @var{regexp}.
7895 If @var{type_regexp} is provided, print only the local variables whose
7896 types, as printed by the @code{whatis} command, match
7897 the regular expression @var{type_regexp}.
7898 If @var{type_regexp} contains space(s), it should be enclosed in
7899 quote characters. If needed, use backslash to escape the meaning
7900 of special characters or quotes.
7902 If both @var{regexp} and @var{type_regexp} are provided, a local variable
7903 is printed only if its name matches @var{regexp} and its type matches
7906 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
7907 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
7908 For example, your program might use Resource Acquisition Is
7909 Initialization types (RAII) such as @code{lock_something_t}: each
7910 local variable of type @code{lock_something_t} automatically places a
7911 lock that is destroyed when the variable goes out of scope. You can
7912 then list all acquired locks in your program by doing
7914 thread apply all -s frame apply all -s info locals -q -t lock_something_t
7917 or the equivalent shorter form
7919 tfaas i lo -q -t lock_something_t
7925 @section Applying a Command to Several Frames.
7927 @cindex apply command to several frames
7929 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{flag}]@dots{} @var{command}
7930 The @code{frame apply} command allows you to apply the named
7931 @var{command} to one or more frames.
7935 Specify @code{all} to apply @var{command} to all frames.
7938 Use @var{count} to apply @var{command} to the innermost @var{count}
7939 frames, where @var{count} is a positive number.
7942 Use @var{-count} to apply @var{command} to the outermost @var{count}
7943 frames, where @var{count} is a positive number.
7946 Use @code{level} to apply @var{command} to the set of frames identified
7947 by the @var{level} list. @var{level} is a frame level or a range of frame
7948 levels as @var{level1}-@var{level2}. The frame level is the number shown
7949 in the first field of the @samp{backtrace} command output.
7950 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
7951 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
7957 Note that the frames on which @code{frame apply} applies a command are
7958 also influenced by the @code{set backtrace} settings such as @code{set
7959 backtrace past-main} and @code{set backtrace limit N}. See
7960 @xref{Backtrace,,Backtraces}.
7962 The @var{flag} arguments control what output to produce and how to handle
7963 errors raised when applying @var{command} to a frame. @var{flag}
7964 must start with a @code{-} directly followed by one letter in
7965 @code{qcs}. If several flags are provided, they must be given
7966 individually, such as @code{-c -q}.
7968 By default, @value{GDBN} displays some frame information before the
7969 output produced by @var{command}, and an error raised during the
7970 execution of a @var{command} will abort @code{frame apply}. The
7971 following flags can be used to fine-tune this behavior:
7975 The flag @code{-c}, which stands for @samp{continue}, causes any
7976 errors in @var{command} to be displayed, and the execution of
7977 @code{frame apply} then continues.
7979 The flag @code{-s}, which stands for @samp{silent}, causes any errors
7980 or empty output produced by a @var{command} to be silently ignored.
7981 That is, the execution continues, but the frame information and errors
7984 The flag @code{-q} (@samp{quiet}) disables printing the frame
7988 The following example shows how the flags @code{-c} and @code{-s} are
7989 working when applying the command @code{p j} to all frames, where
7990 variable @code{j} can only be successfully printed in the outermost
7991 @code{#1 main} frame.
7995 (gdb) frame apply all p j
7996 #0 some_function (i=5) at fun.c:4
7997 No symbol "j" in current context.
7998 (gdb) frame apply all -c p j
7999 #0 some_function (i=5) at fun.c:4
8000 No symbol "j" in current context.
8001 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8003 (gdb) frame apply all -s p j
8004 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8010 By default, @samp{frame apply}, prints the frame location
8011 information before the command output:
8015 (gdb) frame apply all p $sp
8016 #0 some_function (i=5) at fun.c:4
8017 $4 = (void *) 0xffffd1e0
8018 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8019 $5 = (void *) 0xffffd1f0
8024 If flag @code{-q} is given, no frame information is printed:
8027 (gdb) frame apply all -q p $sp
8028 $12 = (void *) 0xffffd1e0
8029 $13 = (void *) 0xffffd1f0
8037 @cindex apply a command to all frames (ignoring errors and empty output)
8038 @item faas @var{command}
8039 Shortcut for @code{frame apply all -s @var{command}}.
8040 Applies @var{command} on all frames, ignoring errors and empty output.
8042 It can for example be used to print a local variable or a function
8043 argument without knowing the frame where this variable or argument
8046 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8049 Note that the command @code{tfaas @var{command}} applies @var{command}
8050 on all frames of all threads. See @xref{Threads,,Threads}.
8054 @node Frame Filter Management
8055 @section Management of Frame Filters.
8056 @cindex managing frame filters
8058 Frame filters are Python based utilities to manage and decorate the
8059 output of frames. @xref{Frame Filter API}, for further information.
8061 Managing frame filters is performed by several commands available
8062 within @value{GDBN}, detailed here.
8065 @kindex info frame-filter
8066 @item info frame-filter
8067 Print a list of installed frame filters from all dictionaries, showing
8068 their name, priority and enabled status.
8070 @kindex disable frame-filter
8071 @anchor{disable frame-filter all}
8072 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8073 Disable a frame filter in the dictionary matching
8074 @var{filter-dictionary} and @var{filter-name}. The
8075 @var{filter-dictionary} may be @code{all}, @code{global},
8076 @code{progspace}, or the name of the object file where the frame filter
8077 dictionary resides. When @code{all} is specified, all frame filters
8078 across all dictionaries are disabled. The @var{filter-name} is the name
8079 of the frame filter and is used when @code{all} is not the option for
8080 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8081 may be enabled again later.
8083 @kindex enable frame-filter
8084 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8085 Enable a frame filter in the dictionary matching
8086 @var{filter-dictionary} and @var{filter-name}. The
8087 @var{filter-dictionary} may be @code{all}, @code{global},
8088 @code{progspace} or the name of the object file where the frame filter
8089 dictionary resides. When @code{all} is specified, all frame filters across
8090 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8091 filter and is used when @code{all} is not the option for
8092 @var{filter-dictionary}.
8097 (gdb) info frame-filter
8099 global frame-filters:
8100 Priority Enabled Name
8101 1000 No PrimaryFunctionFilter
8104 progspace /build/test frame-filters:
8105 Priority Enabled Name
8106 100 Yes ProgspaceFilter
8108 objfile /build/test frame-filters:
8109 Priority Enabled Name
8110 999 Yes BuildProgra Filter
8112 (gdb) disable frame-filter /build/test BuildProgramFilter
8113 (gdb) info frame-filter
8115 global frame-filters:
8116 Priority Enabled Name
8117 1000 No PrimaryFunctionFilter
8120 progspace /build/test frame-filters:
8121 Priority Enabled Name
8122 100 Yes ProgspaceFilter
8124 objfile /build/test frame-filters:
8125 Priority Enabled Name
8126 999 No BuildProgramFilter
8128 (gdb) enable frame-filter global PrimaryFunctionFilter
8129 (gdb) info frame-filter
8131 global frame-filters:
8132 Priority Enabled Name
8133 1000 Yes PrimaryFunctionFilter
8136 progspace /build/test frame-filters:
8137 Priority Enabled Name
8138 100 Yes ProgspaceFilter
8140 objfile /build/test frame-filters:
8141 Priority Enabled Name
8142 999 No BuildProgramFilter
8145 @kindex set frame-filter priority
8146 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8147 Set the @var{priority} of a frame filter in the dictionary matching
8148 @var{filter-dictionary}, and the frame filter name matching
8149 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8150 @code{progspace} or the name of the object file where the frame filter
8151 dictionary resides. The @var{priority} is an integer.
8153 @kindex show frame-filter priority
8154 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8155 Show the @var{priority} of a frame filter in the dictionary matching
8156 @var{filter-dictionary}, and the frame filter name matching
8157 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8158 @code{progspace} or the name of the object file where the frame filter
8164 (gdb) info frame-filter
8166 global frame-filters:
8167 Priority Enabled Name
8168 1000 Yes PrimaryFunctionFilter
8171 progspace /build/test frame-filters:
8172 Priority Enabled Name
8173 100 Yes ProgspaceFilter
8175 objfile /build/test frame-filters:
8176 Priority Enabled Name
8177 999 No BuildProgramFilter
8179 (gdb) set frame-filter priority global Reverse 50
8180 (gdb) info frame-filter
8182 global frame-filters:
8183 Priority Enabled Name
8184 1000 Yes PrimaryFunctionFilter
8187 progspace /build/test frame-filters:
8188 Priority Enabled Name
8189 100 Yes ProgspaceFilter
8191 objfile /build/test frame-filters:
8192 Priority Enabled Name
8193 999 No BuildProgramFilter
8198 @chapter Examining Source Files
8200 @value{GDBN} can print parts of your program's source, since the debugging
8201 information recorded in the program tells @value{GDBN} what source files were
8202 used to build it. When your program stops, @value{GDBN} spontaneously prints
8203 the line where it stopped. Likewise, when you select a stack frame
8204 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8205 execution in that frame has stopped. You can print other portions of
8206 source files by explicit command.
8208 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8209 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8210 @value{GDBN} under @sc{gnu} Emacs}.
8213 * List:: Printing source lines
8214 * Specify Location:: How to specify code locations
8215 * Edit:: Editing source files
8216 * Search:: Searching source files
8217 * Source Path:: Specifying source directories
8218 * Machine Code:: Source and machine code
8222 @section Printing Source Lines
8225 @kindex l @r{(@code{list})}
8226 To print lines from a source file, use the @code{list} command
8227 (abbreviated @code{l}). By default, ten lines are printed.
8228 There are several ways to specify what part of the file you want to
8229 print; see @ref{Specify Location}, for the full list.
8231 Here are the forms of the @code{list} command most commonly used:
8234 @item list @var{linenum}
8235 Print lines centered around line number @var{linenum} in the
8236 current source file.
8238 @item list @var{function}
8239 Print lines centered around the beginning of function
8243 Print more lines. If the last lines printed were printed with a
8244 @code{list} command, this prints lines following the last lines
8245 printed; however, if the last line printed was a solitary line printed
8246 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8247 Stack}), this prints lines centered around that line.
8250 Print lines just before the lines last printed.
8253 @cindex @code{list}, how many lines to display
8254 By default, @value{GDBN} prints ten source lines with any of these forms of
8255 the @code{list} command. You can change this using @code{set listsize}:
8258 @kindex set listsize
8259 @item set listsize @var{count}
8260 @itemx set listsize unlimited
8261 Make the @code{list} command display @var{count} source lines (unless
8262 the @code{list} argument explicitly specifies some other number).
8263 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8265 @kindex show listsize
8267 Display the number of lines that @code{list} prints.
8270 Repeating a @code{list} command with @key{RET} discards the argument,
8271 so it is equivalent to typing just @code{list}. This is more useful
8272 than listing the same lines again. An exception is made for an
8273 argument of @samp{-}; that argument is preserved in repetition so that
8274 each repetition moves up in the source file.
8276 In general, the @code{list} command expects you to supply zero, one or two
8277 @dfn{locations}. Locations specify source lines; there are several ways
8278 of writing them (@pxref{Specify Location}), but the effect is always
8279 to specify some source line.
8281 Here is a complete description of the possible arguments for @code{list}:
8284 @item list @var{location}
8285 Print lines centered around the line specified by @var{location}.
8287 @item list @var{first},@var{last}
8288 Print lines from @var{first} to @var{last}. Both arguments are
8289 locations. When a @code{list} command has two locations, and the
8290 source file of the second location is omitted, this refers to
8291 the same source file as the first location.
8293 @item list ,@var{last}
8294 Print lines ending with @var{last}.
8296 @item list @var{first},
8297 Print lines starting with @var{first}.
8300 Print lines just after the lines last printed.
8303 Print lines just before the lines last printed.
8306 As described in the preceding table.
8309 @node Specify Location
8310 @section Specifying a Location
8311 @cindex specifying location
8313 @cindex source location
8316 * Linespec Locations:: Linespec locations
8317 * Explicit Locations:: Explicit locations
8318 * Address Locations:: Address locations
8321 Several @value{GDBN} commands accept arguments that specify a location
8322 of your program's code. Since @value{GDBN} is a source-level
8323 debugger, a location usually specifies some line in the source code.
8324 Locations may be specified using three different formats:
8325 linespec locations, explicit locations, or address locations.
8327 @node Linespec Locations
8328 @subsection Linespec Locations
8329 @cindex linespec locations
8331 A @dfn{linespec} is a colon-separated list of source location parameters such
8332 as file name, function name, etc. Here are all the different ways of
8333 specifying a linespec:
8337 Specifies the line number @var{linenum} of the current source file.
8340 @itemx +@var{offset}
8341 Specifies the line @var{offset} lines before or after the @dfn{current
8342 line}. For the @code{list} command, the current line is the last one
8343 printed; for the breakpoint commands, this is the line at which
8344 execution stopped in the currently selected @dfn{stack frame}
8345 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
8346 used as the second of the two linespecs in a @code{list} command,
8347 this specifies the line @var{offset} lines up or down from the first
8350 @item @var{filename}:@var{linenum}
8351 Specifies the line @var{linenum} in the source file @var{filename}.
8352 If @var{filename} is a relative file name, then it will match any
8353 source file name with the same trailing components. For example, if
8354 @var{filename} is @samp{gcc/expr.c}, then it will match source file
8355 name of @file{/build/trunk/gcc/expr.c}, but not
8356 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
8358 @item @var{function}
8359 Specifies the line that begins the body of the function @var{function}.
8360 For example, in C, this is the line with the open brace.
8362 By default, in C@t{++} and Ada, @var{function} is interpreted as
8363 specifying all functions named @var{function} in all scopes. For
8364 C@t{++}, this means in all namespaces and classes. For Ada, this
8365 means in all packages.
8367 For example, assuming a program with C@t{++} symbols named
8368 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8369 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
8371 Commands that accept a linespec let you override this with the
8372 @code{-qualified} option. For example, @w{@kbd{break -qualified
8373 func}} sets a breakpoint on a free-function named @code{func} ignoring
8374 any C@t{++} class methods and namespace functions called @code{func}.
8376 @xref{Explicit Locations}.
8378 @item @var{function}:@var{label}
8379 Specifies the line where @var{label} appears in @var{function}.
8381 @item @var{filename}:@var{function}
8382 Specifies the line that begins the body of the function @var{function}
8383 in the file @var{filename}. You only need the file name with a
8384 function name to avoid ambiguity when there are identically named
8385 functions in different source files.
8388 Specifies the line at which the label named @var{label} appears
8389 in the function corresponding to the currently selected stack frame.
8390 If there is no current selected stack frame (for instance, if the inferior
8391 is not running), then @value{GDBN} will not search for a label.
8393 @cindex breakpoint at static probe point
8394 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
8395 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
8396 applications to embed static probes. @xref{Static Probe Points}, for more
8397 information on finding and using static probes. This form of linespec
8398 specifies the location of such a static probe.
8400 If @var{objfile} is given, only probes coming from that shared library
8401 or executable matching @var{objfile} as a regular expression are considered.
8402 If @var{provider} is given, then only probes from that provider are considered.
8403 If several probes match the spec, @value{GDBN} will insert a breakpoint at
8404 each one of those probes.
8407 @node Explicit Locations
8408 @subsection Explicit Locations
8409 @cindex explicit locations
8411 @dfn{Explicit locations} allow the user to directly specify the source
8412 location's parameters using option-value pairs.
8414 Explicit locations are useful when several functions, labels, or
8415 file names have the same name (base name for files) in the program's
8416 sources. In these cases, explicit locations point to the source
8417 line you meant more accurately and unambiguously. Also, using
8418 explicit locations might be faster in large programs.
8420 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
8421 defined in the file named @file{foo} or the label @code{bar} in a function
8422 named @code{foo}. @value{GDBN} must search either the file system or
8423 the symbol table to know.
8425 The list of valid explicit location options is summarized in the
8429 @item -source @var{filename}
8430 The value specifies the source file name. To differentiate between
8431 files with the same base name, prepend as many directories as is necessary
8432 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8433 @value{GDBN} will use the first file it finds with the given base
8434 name. This option requires the use of either @code{-function} or @code{-line}.
8436 @item -function @var{function}
8437 The value specifies the name of a function. Operations
8438 on function locations unmodified by other options (such as @code{-label}
8439 or @code{-line}) refer to the line that begins the body of the function.
8440 In C, for example, this is the line with the open brace.
8442 By default, in C@t{++} and Ada, @var{function} is interpreted as
8443 specifying all functions named @var{function} in all scopes. For
8444 C@t{++}, this means in all namespaces and classes. For Ada, this
8445 means in all packages.
8447 For example, assuming a program with C@t{++} symbols named
8448 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8449 -function func}} and @w{@kbd{break -function B::func}} set a
8450 breakpoint on both symbols.
8452 You can use the @kbd{-qualified} flag to override this (see below).
8456 This flag makes @value{GDBN} interpret a function name specified with
8457 @kbd{-function} as a complete fully-qualified name.
8459 For example, assuming a C@t{++} program with symbols named
8460 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8461 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8463 (Note: the @kbd{-qualified} option can precede a linespec as well
8464 (@pxref{Linespec Locations}), so the particular example above could be
8465 simplified as @w{@kbd{break -qualified B::func}}.)
8467 @item -label @var{label}
8468 The value specifies the name of a label. When the function
8469 name is not specified, the label is searched in the function of the currently
8470 selected stack frame.
8472 @item -line @var{number}
8473 The value specifies a line offset for the location. The offset may either
8474 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8475 the command. When specified without any other options, the line offset is
8476 relative to the current line.
8479 Explicit location options may be abbreviated by omitting any non-unique
8480 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8482 @node Address Locations
8483 @subsection Address Locations
8484 @cindex address locations
8486 @dfn{Address locations} indicate a specific program address. They have
8487 the generalized form *@var{address}.
8489 For line-oriented commands, such as @code{list} and @code{edit}, this
8490 specifies a source line that contains @var{address}. For @code{break} and
8491 other breakpoint-oriented commands, this can be used to set breakpoints in
8492 parts of your program which do not have debugging information or
8495 Here @var{address} may be any expression valid in the current working
8496 language (@pxref{Languages, working language}) that specifies a code
8497 address. In addition, as a convenience, @value{GDBN} extends the
8498 semantics of expressions used in locations to cover several situations
8499 that frequently occur during debugging. Here are the various forms
8503 @item @var{expression}
8504 Any expression valid in the current working language.
8506 @item @var{funcaddr}
8507 An address of a function or procedure derived from its name. In C,
8508 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8509 simply the function's name @var{function} (and actually a special case
8510 of a valid expression). In Pascal and Modula-2, this is
8511 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8512 (although the Pascal form also works).
8514 This form specifies the address of the function's first instruction,
8515 before the stack frame and arguments have been set up.
8517 @item '@var{filename}':@var{funcaddr}
8518 Like @var{funcaddr} above, but also specifies the name of the source
8519 file explicitly. This is useful if the name of the function does not
8520 specify the function unambiguously, e.g., if there are several
8521 functions with identical names in different source files.
8525 @section Editing Source Files
8526 @cindex editing source files
8529 @kindex e @r{(@code{edit})}
8530 To edit the lines in a source file, use the @code{edit} command.
8531 The editing program of your choice
8532 is invoked with the current line set to
8533 the active line in the program.
8534 Alternatively, there are several ways to specify what part of the file you
8535 want to print if you want to see other parts of the program:
8538 @item edit @var{location}
8539 Edit the source file specified by @code{location}. Editing starts at
8540 that @var{location}, e.g., at the specified source line of the
8541 specified file. @xref{Specify Location}, for all the possible forms
8542 of the @var{location} argument; here are the forms of the @code{edit}
8543 command most commonly used:
8546 @item edit @var{number}
8547 Edit the current source file with @var{number} as the active line number.
8549 @item edit @var{function}
8550 Edit the file containing @var{function} at the beginning of its definition.
8555 @subsection Choosing your Editor
8556 You can customize @value{GDBN} to use any editor you want
8558 The only restriction is that your editor (say @code{ex}), recognizes the
8559 following command-line syntax:
8561 ex +@var{number} file
8563 The optional numeric value +@var{number} specifies the number of the line in
8564 the file where to start editing.}.
8565 By default, it is @file{@value{EDITOR}}, but you can change this
8566 by setting the environment variable @code{EDITOR} before using
8567 @value{GDBN}. For example, to configure @value{GDBN} to use the
8568 @code{vi} editor, you could use these commands with the @code{sh} shell:
8574 or in the @code{csh} shell,
8576 setenv EDITOR /usr/bin/vi
8581 @section Searching Source Files
8582 @cindex searching source files
8584 There are two commands for searching through the current source file for a
8589 @kindex forward-search
8590 @kindex fo @r{(@code{forward-search})}
8591 @item forward-search @var{regexp}
8592 @itemx search @var{regexp}
8593 The command @samp{forward-search @var{regexp}} checks each line,
8594 starting with the one following the last line listed, for a match for
8595 @var{regexp}. It lists the line that is found. You can use the
8596 synonym @samp{search @var{regexp}} or abbreviate the command name as
8599 @kindex reverse-search
8600 @item reverse-search @var{regexp}
8601 The command @samp{reverse-search @var{regexp}} checks each line, starting
8602 with the one before the last line listed and going backward, for a match
8603 for @var{regexp}. It lists the line that is found. You can abbreviate
8604 this command as @code{rev}.
8608 @section Specifying Source Directories
8611 @cindex directories for source files
8612 Executable programs sometimes do not record the directories of the source
8613 files from which they were compiled, just the names. Even when they do,
8614 the directories could be moved between the compilation and your debugging
8615 session. @value{GDBN} has a list of directories to search for source files;
8616 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8617 it tries all the directories in the list, in the order they are present
8618 in the list, until it finds a file with the desired name.
8620 For example, suppose an executable references the file
8621 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8622 @file{/mnt/cross}. The file is first looked up literally; if this
8623 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8624 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8625 message is printed. @value{GDBN} does not look up the parts of the
8626 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8627 Likewise, the subdirectories of the source path are not searched: if
8628 the source path is @file{/mnt/cross}, and the binary refers to
8629 @file{foo.c}, @value{GDBN} would not find it under
8630 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8632 Plain file names, relative file names with leading directories, file
8633 names containing dots, etc.@: are all treated as described above; for
8634 instance, if the source path is @file{/mnt/cross}, and the source file
8635 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8636 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8637 that---@file{/mnt/cross/foo.c}.
8639 Note that the executable search path is @emph{not} used to locate the
8642 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8643 any information it has cached about where source files are found and where
8644 each line is in the file.
8648 When you start @value{GDBN}, its source path includes only @samp{cdir}
8649 and @samp{cwd}, in that order.
8650 To add other directories, use the @code{directory} command.
8652 The search path is used to find both program source files and @value{GDBN}
8653 script files (read using the @samp{-command} option and @samp{source} command).
8655 In addition to the source path, @value{GDBN} provides a set of commands
8656 that manage a list of source path substitution rules. A @dfn{substitution
8657 rule} specifies how to rewrite source directories stored in the program's
8658 debug information in case the sources were moved to a different
8659 directory between compilation and debugging. A rule is made of
8660 two strings, the first specifying what needs to be rewritten in
8661 the path, and the second specifying how it should be rewritten.
8662 In @ref{set substitute-path}, we name these two parts @var{from} and
8663 @var{to} respectively. @value{GDBN} does a simple string replacement
8664 of @var{from} with @var{to} at the start of the directory part of the
8665 source file name, and uses that result instead of the original file
8666 name to look up the sources.
8668 Using the previous example, suppose the @file{foo-1.0} tree has been
8669 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8670 @value{GDBN} to replace @file{/usr/src} in all source path names with
8671 @file{/mnt/cross}. The first lookup will then be
8672 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8673 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8674 substitution rule, use the @code{set substitute-path} command
8675 (@pxref{set substitute-path}).
8677 To avoid unexpected substitution results, a rule is applied only if the
8678 @var{from} part of the directory name ends at a directory separator.
8679 For instance, a rule substituting @file{/usr/source} into
8680 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8681 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8682 is applied only at the beginning of the directory name, this rule will
8683 not be applied to @file{/root/usr/source/baz.c} either.
8685 In many cases, you can achieve the same result using the @code{directory}
8686 command. However, @code{set substitute-path} can be more efficient in
8687 the case where the sources are organized in a complex tree with multiple
8688 subdirectories. With the @code{directory} command, you need to add each
8689 subdirectory of your project. If you moved the entire tree while
8690 preserving its internal organization, then @code{set substitute-path}
8691 allows you to direct the debugger to all the sources with one single
8694 @code{set substitute-path} is also more than just a shortcut command.
8695 The source path is only used if the file at the original location no
8696 longer exists. On the other hand, @code{set substitute-path} modifies
8697 the debugger behavior to look at the rewritten location instead. So, if
8698 for any reason a source file that is not relevant to your executable is
8699 located at the original location, a substitution rule is the only
8700 method available to point @value{GDBN} at the new location.
8702 @cindex @samp{--with-relocated-sources}
8703 @cindex default source path substitution
8704 You can configure a default source path substitution rule by
8705 configuring @value{GDBN} with the
8706 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8707 should be the name of a directory under @value{GDBN}'s configured
8708 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8709 directory names in debug information under @var{dir} will be adjusted
8710 automatically if the installed @value{GDBN} is moved to a new
8711 location. This is useful if @value{GDBN}, libraries or executables
8712 with debug information and corresponding source code are being moved
8716 @item directory @var{dirname} @dots{}
8717 @item dir @var{dirname} @dots{}
8718 Add directory @var{dirname} to the front of the source path. Several
8719 directory names may be given to this command, separated by @samp{:}
8720 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8721 part of absolute file names) or
8722 whitespace. You may specify a directory that is already in the source
8723 path; this moves it forward, so @value{GDBN} searches it sooner.
8727 @vindex $cdir@r{, convenience variable}
8728 @vindex $cwd@r{, convenience variable}
8729 @cindex compilation directory
8730 @cindex current directory
8731 @cindex working directory
8732 @cindex directory, current
8733 @cindex directory, compilation
8734 You can use the string @samp{$cdir} to refer to the compilation
8735 directory (if one is recorded), and @samp{$cwd} to refer to the current
8736 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8737 tracks the current working directory as it changes during your @value{GDBN}
8738 session, while the latter is immediately expanded to the current
8739 directory at the time you add an entry to the source path.
8742 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8744 @c RET-repeat for @code{directory} is explicitly disabled, but since
8745 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8747 @item set directories @var{path-list}
8748 @kindex set directories
8749 Set the source path to @var{path-list}.
8750 @samp{$cdir:$cwd} are added if missing.
8752 @item show directories
8753 @kindex show directories
8754 Print the source path: show which directories it contains.
8756 @anchor{set substitute-path}
8757 @item set substitute-path @var{from} @var{to}
8758 @kindex set substitute-path
8759 Define a source path substitution rule, and add it at the end of the
8760 current list of existing substitution rules. If a rule with the same
8761 @var{from} was already defined, then the old rule is also deleted.
8763 For example, if the file @file{/foo/bar/baz.c} was moved to
8764 @file{/mnt/cross/baz.c}, then the command
8767 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8771 will tell @value{GDBN} to replace @samp{/foo/bar} with
8772 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8773 @file{baz.c} even though it was moved.
8775 In the case when more than one substitution rule have been defined,
8776 the rules are evaluated one by one in the order where they have been
8777 defined. The first one matching, if any, is selected to perform
8780 For instance, if we had entered the following commands:
8783 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8784 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8788 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8789 @file{/mnt/include/defs.h} by using the first rule. However, it would
8790 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8791 @file{/mnt/src/lib/foo.c}.
8794 @item unset substitute-path [path]
8795 @kindex unset substitute-path
8796 If a path is specified, search the current list of substitution rules
8797 for a rule that would rewrite that path. Delete that rule if found.
8798 A warning is emitted by the debugger if no rule could be found.
8800 If no path is specified, then all substitution rules are deleted.
8802 @item show substitute-path [path]
8803 @kindex show substitute-path
8804 If a path is specified, then print the source path substitution rule
8805 which would rewrite that path, if any.
8807 If no path is specified, then print all existing source path substitution
8812 If your source path is cluttered with directories that are no longer of
8813 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8814 versions of source. You can correct the situation as follows:
8818 Use @code{directory} with no argument to reset the source path to its default value.
8821 Use @code{directory} with suitable arguments to reinstall the
8822 directories you want in the source path. You can add all the
8823 directories in one command.
8827 @section Source and Machine Code
8828 @cindex source line and its code address
8830 You can use the command @code{info line} to map source lines to program
8831 addresses (and vice versa), and the command @code{disassemble} to display
8832 a range of addresses as machine instructions. You can use the command
8833 @code{set disassemble-next-line} to set whether to disassemble next
8834 source line when execution stops. When run under @sc{gnu} Emacs
8835 mode, the @code{info line} command causes the arrow to point to the
8836 line specified. Also, @code{info line} prints addresses in symbolic form as
8842 @itemx info line @var{location}
8843 Print the starting and ending addresses of the compiled code for
8844 source line @var{location}. You can specify source lines in any of
8845 the ways documented in @ref{Specify Location}. With no @var{location}
8846 information about the current source line is printed.
8849 For example, we can use @code{info line} to discover the location of
8850 the object code for the first line of function
8851 @code{m4_changequote}:
8854 (@value{GDBP}) info line m4_changequote
8855 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
8856 ends at 0x6350 <m4_changequote+4>.
8860 @cindex code address and its source line
8861 We can also inquire (using @code{*@var{addr}} as the form for
8862 @var{location}) what source line covers a particular address:
8864 (@value{GDBP}) info line *0x63ff
8865 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
8866 ends at 0x6404 <m4_changequote+184>.
8869 @cindex @code{$_} and @code{info line}
8870 @cindex @code{x} command, default address
8871 @kindex x@r{(examine), and} info line
8872 After @code{info line}, the default address for the @code{x} command
8873 is changed to the starting address of the line, so that @samp{x/i} is
8874 sufficient to begin examining the machine code (@pxref{Memory,
8875 ,Examining Memory}). Also, this address is saved as the value of the
8876 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8879 @cindex info line, repeated calls
8880 After @code{info line}, using @code{info line} again without
8881 specifying a location will display information about the next source
8886 @cindex assembly instructions
8887 @cindex instructions, assembly
8888 @cindex machine instructions
8889 @cindex listing machine instructions
8891 @itemx disassemble /m
8892 @itemx disassemble /s
8893 @itemx disassemble /r
8894 This specialized command dumps a range of memory as machine
8895 instructions. It can also print mixed source+disassembly by specifying
8896 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8897 as well as in symbolic form by specifying the @code{/r} modifier.
8898 The default memory range is the function surrounding the
8899 program counter of the selected frame. A single argument to this
8900 command is a program counter value; @value{GDBN} dumps the function
8901 surrounding this value. When two arguments are given, they should
8902 be separated by a comma, possibly surrounded by whitespace. The
8903 arguments specify a range of addresses to dump, in one of two forms:
8906 @item @var{start},@var{end}
8907 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8908 @item @var{start},+@var{length}
8909 the addresses from @var{start} (inclusive) to
8910 @code{@var{start}+@var{length}} (exclusive).
8914 When 2 arguments are specified, the name of the function is also
8915 printed (since there could be several functions in the given range).
8917 The argument(s) can be any expression yielding a numeric value, such as
8918 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8920 If the range of memory being disassembled contains current program counter,
8921 the instruction at that location is shown with a @code{=>} marker.
8924 The following example shows the disassembly of a range of addresses of
8925 HP PA-RISC 2.0 code:
8928 (@value{GDBP}) disas 0x32c4, 0x32e4
8929 Dump of assembler code from 0x32c4 to 0x32e4:
8930 0x32c4 <main+204>: addil 0,dp
8931 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8932 0x32cc <main+212>: ldil 0x3000,r31
8933 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8934 0x32d4 <main+220>: ldo 0(r31),rp
8935 0x32d8 <main+224>: addil -0x800,dp
8936 0x32dc <main+228>: ldo 0x588(r1),r26
8937 0x32e0 <main+232>: ldil 0x3000,r31
8938 End of assembler dump.
8941 Here is an example showing mixed source+assembly for Intel x86
8942 with @code{/m} or @code{/s}, when the program is stopped just after
8943 function prologue in a non-optimized function with no inline code.
8946 (@value{GDBP}) disas /m main
8947 Dump of assembler code for function main:
8949 0x08048330 <+0>: push %ebp
8950 0x08048331 <+1>: mov %esp,%ebp
8951 0x08048333 <+3>: sub $0x8,%esp
8952 0x08048336 <+6>: and $0xfffffff0,%esp
8953 0x08048339 <+9>: sub $0x10,%esp
8955 6 printf ("Hello.\n");
8956 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8957 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8961 0x08048348 <+24>: mov $0x0,%eax
8962 0x0804834d <+29>: leave
8963 0x0804834e <+30>: ret
8965 End of assembler dump.
8968 The @code{/m} option is deprecated as its output is not useful when
8969 there is either inlined code or re-ordered code.
8970 The @code{/s} option is the preferred choice.
8971 Here is an example for AMD x86-64 showing the difference between
8972 @code{/m} output and @code{/s} output.
8973 This example has one inline function defined in a header file,
8974 and the code is compiled with @samp{-O2} optimization.
8975 Note how the @code{/m} output is missing the disassembly of
8976 several instructions that are present in the @code{/s} output.
9006 (@value{GDBP}) disas /m main
9007 Dump of assembler code for function main:
9011 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9012 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9016 0x000000000040041d <+29>: xor %eax,%eax
9017 0x000000000040041f <+31>: retq
9018 0x0000000000400420 <+32>: add %eax,%eax
9019 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9021 End of assembler dump.
9022 (@value{GDBP}) disas /s main
9023 Dump of assembler code for function main:
9027 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9031 0x0000000000400406 <+6>: test %eax,%eax
9032 0x0000000000400408 <+8>: js 0x400420 <main+32>
9037 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9038 0x000000000040040d <+13>: test %eax,%eax
9039 0x000000000040040f <+15>: mov $0x1,%eax
9040 0x0000000000400414 <+20>: cmovne %edx,%eax
9044 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9048 0x000000000040041d <+29>: xor %eax,%eax
9049 0x000000000040041f <+31>: retq
9053 0x0000000000400420 <+32>: add %eax,%eax
9054 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9055 End of assembler dump.
9058 Here is another example showing raw instructions in hex for AMD x86-64,
9061 (gdb) disas /r 0x400281,+10
9062 Dump of assembler code from 0x400281 to 0x40028b:
9063 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9064 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9065 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9066 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9067 End of assembler dump.
9070 Addresses cannot be specified as a location (@pxref{Specify Location}).
9071 So, for example, if you want to disassemble function @code{bar}
9072 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9073 and not @samp{disassemble foo.c:bar}.
9075 Some architectures have more than one commonly-used set of instruction
9076 mnemonics or other syntax.
9078 For programs that were dynamically linked and use shared libraries,
9079 instructions that call functions or branch to locations in the shared
9080 libraries might show a seemingly bogus location---it's actually a
9081 location of the relocation table. On some architectures, @value{GDBN}
9082 might be able to resolve these to actual function names.
9085 @kindex set disassembler-options
9086 @cindex disassembler options
9087 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9088 This command controls the passing of target specific information to
9089 the disassembler. For a list of valid options, please refer to the
9090 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9091 manual and/or the output of @kbd{objdump --help}
9092 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9093 The default value is the empty string.
9095 If it is necessary to specify more than one disassembler option, then
9096 multiple options can be placed together into a comma separated list.
9097 Currently this command is only supported on targets ARM, MIPS, PowerPC
9100 @kindex show disassembler-options
9101 @item show disassembler-options
9102 Show the current setting of the disassembler options.
9106 @kindex set disassembly-flavor
9107 @cindex Intel disassembly flavor
9108 @cindex AT&T disassembly flavor
9109 @item set disassembly-flavor @var{instruction-set}
9110 Select the instruction set to use when disassembling the
9111 program via the @code{disassemble} or @code{x/i} commands.
9113 Currently this command is only defined for the Intel x86 family. You
9114 can set @var{instruction-set} to either @code{intel} or @code{att}.
9115 The default is @code{att}, the AT&T flavor used by default by Unix
9116 assemblers for x86-based targets.
9118 @kindex show disassembly-flavor
9119 @item show disassembly-flavor
9120 Show the current setting of the disassembly flavor.
9124 @kindex set disassemble-next-line
9125 @kindex show disassemble-next-line
9126 @item set disassemble-next-line
9127 @itemx show disassemble-next-line
9128 Control whether or not @value{GDBN} will disassemble the next source
9129 line or instruction when execution stops. If ON, @value{GDBN} will
9130 display disassembly of the next source line when execution of the
9131 program being debugged stops. This is @emph{in addition} to
9132 displaying the source line itself, which @value{GDBN} always does if
9133 possible. If the next source line cannot be displayed for some reason
9134 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9135 info in the debug info), @value{GDBN} will display disassembly of the
9136 next @emph{instruction} instead of showing the next source line. If
9137 AUTO, @value{GDBN} will display disassembly of next instruction only
9138 if the source line cannot be displayed. This setting causes
9139 @value{GDBN} to display some feedback when you step through a function
9140 with no line info or whose source file is unavailable. The default is
9141 OFF, which means never display the disassembly of the next line or
9147 @chapter Examining Data
9149 @cindex printing data
9150 @cindex examining data
9153 The usual way to examine data in your program is with the @code{print}
9154 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9155 evaluates and prints the value of an expression of the language your
9156 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9157 Different Languages}). It may also print the expression using a
9158 Python-based pretty-printer (@pxref{Pretty Printing}).
9161 @item print @var{expr}
9162 @itemx print /@var{f} @var{expr}
9163 @var{expr} is an expression (in the source language). By default the
9164 value of @var{expr} is printed in a format appropriate to its data type;
9165 you can choose a different format by specifying @samp{/@var{f}}, where
9166 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9170 @itemx print /@var{f}
9171 @cindex reprint the last value
9172 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
9173 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
9174 conveniently inspect the same value in an alternative format.
9177 A more low-level way of examining data is with the @code{x} command.
9178 It examines data in memory at a specified address and prints it in a
9179 specified format. @xref{Memory, ,Examining Memory}.
9181 If you are interested in information about types, or about how the
9182 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
9183 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
9186 @cindex exploring hierarchical data structures
9188 Another way of examining values of expressions and type information is
9189 through the Python extension command @code{explore} (available only if
9190 the @value{GDBN} build is configured with @code{--with-python}). It
9191 offers an interactive way to start at the highest level (or, the most
9192 abstract level) of the data type of an expression (or, the data type
9193 itself) and explore all the way down to leaf scalar values/fields
9194 embedded in the higher level data types.
9197 @item explore @var{arg}
9198 @var{arg} is either an expression (in the source language), or a type
9199 visible in the current context of the program being debugged.
9202 The working of the @code{explore} command can be illustrated with an
9203 example. If a data type @code{struct ComplexStruct} is defined in your
9213 struct ComplexStruct
9215 struct SimpleStruct *ss_p;
9221 followed by variable declarations as
9224 struct SimpleStruct ss = @{ 10, 1.11 @};
9225 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
9229 then, the value of the variable @code{cs} can be explored using the
9230 @code{explore} command as follows.
9234 The value of `cs' is a struct/class of type `struct ComplexStruct' with
9235 the following fields:
9237 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
9238 arr = <Enter 1 to explore this field of type `int [10]'>
9240 Enter the field number of choice:
9244 Since the fields of @code{cs} are not scalar values, you are being
9245 prompted to chose the field you want to explore. Let's say you choose
9246 the field @code{ss_p} by entering @code{0}. Then, since this field is a
9247 pointer, you will be asked if it is pointing to a single value. From
9248 the declaration of @code{cs} above, it is indeed pointing to a single
9249 value, hence you enter @code{y}. If you enter @code{n}, then you will
9250 be asked if it were pointing to an array of values, in which case this
9251 field will be explored as if it were an array.
9254 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
9255 Continue exploring it as a pointer to a single value [y/n]: y
9256 The value of `*(cs.ss_p)' is a struct/class of type `struct
9257 SimpleStruct' with the following fields:
9259 i = 10 .. (Value of type `int')
9260 d = 1.1100000000000001 .. (Value of type `double')
9262 Press enter to return to parent value:
9266 If the field @code{arr} of @code{cs} was chosen for exploration by
9267 entering @code{1} earlier, then since it is as array, you will be
9268 prompted to enter the index of the element in the array that you want
9272 `cs.arr' is an array of `int'.
9273 Enter the index of the element you want to explore in `cs.arr': 5
9275 `(cs.arr)[5]' is a scalar value of type `int'.
9279 Press enter to return to parent value:
9282 In general, at any stage of exploration, you can go deeper towards the
9283 leaf values by responding to the prompts appropriately, or hit the
9284 return key to return to the enclosing data structure (the @i{higher}
9285 level data structure).
9287 Similar to exploring values, you can use the @code{explore} command to
9288 explore types. Instead of specifying a value (which is typically a
9289 variable name or an expression valid in the current context of the
9290 program being debugged), you specify a type name. If you consider the
9291 same example as above, your can explore the type
9292 @code{struct ComplexStruct} by passing the argument
9293 @code{struct ComplexStruct} to the @code{explore} command.
9296 (gdb) explore struct ComplexStruct
9300 By responding to the prompts appropriately in the subsequent interactive
9301 session, you can explore the type @code{struct ComplexStruct} in a
9302 manner similar to how the value @code{cs} was explored in the above
9305 The @code{explore} command also has two sub-commands,
9306 @code{explore value} and @code{explore type}. The former sub-command is
9307 a way to explicitly specify that value exploration of the argument is
9308 being invoked, while the latter is a way to explicitly specify that type
9309 exploration of the argument is being invoked.
9312 @item explore value @var{expr}
9313 @cindex explore value
9314 This sub-command of @code{explore} explores the value of the
9315 expression @var{expr} (if @var{expr} is an expression valid in the
9316 current context of the program being debugged). The behavior of this
9317 command is identical to that of the behavior of the @code{explore}
9318 command being passed the argument @var{expr}.
9320 @item explore type @var{arg}
9321 @cindex explore type
9322 This sub-command of @code{explore} explores the type of @var{arg} (if
9323 @var{arg} is a type visible in the current context of program being
9324 debugged), or the type of the value/expression @var{arg} (if @var{arg}
9325 is an expression valid in the current context of the program being
9326 debugged). If @var{arg} is a type, then the behavior of this command is
9327 identical to that of the @code{explore} command being passed the
9328 argument @var{arg}. If @var{arg} is an expression, then the behavior of
9329 this command will be identical to that of the @code{explore} command
9330 being passed the type of @var{arg} as the argument.
9334 * Expressions:: Expressions
9335 * Ambiguous Expressions:: Ambiguous Expressions
9336 * Variables:: Program variables
9337 * Arrays:: Artificial arrays
9338 * Output Formats:: Output formats
9339 * Memory:: Examining memory
9340 * Auto Display:: Automatic display
9341 * Print Settings:: Print settings
9342 * Pretty Printing:: Python pretty printing
9343 * Value History:: Value history
9344 * Convenience Vars:: Convenience variables
9345 * Convenience Funs:: Convenience functions
9346 * Registers:: Registers
9347 * Floating Point Hardware:: Floating point hardware
9348 * Vector Unit:: Vector Unit
9349 * OS Information:: Auxiliary data provided by operating system
9350 * Memory Region Attributes:: Memory region attributes
9351 * Dump/Restore Files:: Copy between memory and a file
9352 * Core File Generation:: Cause a program dump its core
9353 * Character Sets:: Debugging programs that use a different
9354 character set than GDB does
9355 * Caching Target Data:: Data caching for targets
9356 * Searching Memory:: Searching memory for a sequence of bytes
9357 * Value Sizes:: Managing memory allocated for values
9361 @section Expressions
9364 @code{print} and many other @value{GDBN} commands accept an expression and
9365 compute its value. Any kind of constant, variable or operator defined
9366 by the programming language you are using is valid in an expression in
9367 @value{GDBN}. This includes conditional expressions, function calls,
9368 casts, and string constants. It also includes preprocessor macros, if
9369 you compiled your program to include this information; see
9372 @cindex arrays in expressions
9373 @value{GDBN} supports array constants in expressions input by
9374 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
9375 you can use the command @code{print @{1, 2, 3@}} to create an array
9376 of three integers. If you pass an array to a function or assign it
9377 to a program variable, @value{GDBN} copies the array to memory that
9378 is @code{malloc}ed in the target program.
9380 Because C is so widespread, most of the expressions shown in examples in
9381 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
9382 Languages}, for information on how to use expressions in other
9385 In this section, we discuss operators that you can use in @value{GDBN}
9386 expressions regardless of your programming language.
9388 @cindex casts, in expressions
9389 Casts are supported in all languages, not just in C, because it is so
9390 useful to cast a number into a pointer in order to examine a structure
9391 at that address in memory.
9392 @c FIXME: casts supported---Mod2 true?
9394 @value{GDBN} supports these operators, in addition to those common
9395 to programming languages:
9399 @samp{@@} is a binary operator for treating parts of memory as arrays.
9400 @xref{Arrays, ,Artificial Arrays}, for more information.
9403 @samp{::} allows you to specify a variable in terms of the file or
9404 function where it is defined. @xref{Variables, ,Program Variables}.
9406 @cindex @{@var{type}@}
9407 @cindex type casting memory
9408 @cindex memory, viewing as typed object
9409 @cindex casts, to view memory
9410 @item @{@var{type}@} @var{addr}
9411 Refers to an object of type @var{type} stored at address @var{addr} in
9412 memory. The address @var{addr} may be any expression whose value is
9413 an integer or pointer (but parentheses are required around binary
9414 operators, just as in a cast). This construct is allowed regardless
9415 of what kind of data is normally supposed to reside at @var{addr}.
9418 @node Ambiguous Expressions
9419 @section Ambiguous Expressions
9420 @cindex ambiguous expressions
9422 Expressions can sometimes contain some ambiguous elements. For instance,
9423 some programming languages (notably Ada, C@t{++} and Objective-C) permit
9424 a single function name to be defined several times, for application in
9425 different contexts. This is called @dfn{overloading}. Another example
9426 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
9427 templates and is typically instantiated several times, resulting in
9428 the same function name being defined in different contexts.
9430 In some cases and depending on the language, it is possible to adjust
9431 the expression to remove the ambiguity. For instance in C@t{++}, you
9432 can specify the signature of the function you want to break on, as in
9433 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
9434 qualified name of your function often makes the expression unambiguous
9437 When an ambiguity that needs to be resolved is detected, the debugger
9438 has the capability to display a menu of numbered choices for each
9439 possibility, and then waits for the selection with the prompt @samp{>}.
9440 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9441 aborts the current command. If the command in which the expression was
9442 used allows more than one choice to be selected, the next option in the
9443 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9446 For example, the following session excerpt shows an attempt to set a
9447 breakpoint at the overloaded symbol @code{String::after}.
9448 We choose three particular definitions of that function name:
9450 @c FIXME! This is likely to change to show arg type lists, at least
9453 (@value{GDBP}) b String::after
9456 [2] file:String.cc; line number:867
9457 [3] file:String.cc; line number:860
9458 [4] file:String.cc; line number:875
9459 [5] file:String.cc; line number:853
9460 [6] file:String.cc; line number:846
9461 [7] file:String.cc; line number:735
9463 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9464 Breakpoint 2 at 0xb344: file String.cc, line 875.
9465 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9466 Multiple breakpoints were set.
9467 Use the "delete" command to delete unwanted
9474 @kindex set multiple-symbols
9475 @item set multiple-symbols @var{mode}
9476 @cindex multiple-symbols menu
9478 This option allows you to adjust the debugger behavior when an expression
9481 By default, @var{mode} is set to @code{all}. If the command with which
9482 the expression is used allows more than one choice, then @value{GDBN}
9483 automatically selects all possible choices. For instance, inserting
9484 a breakpoint on a function using an ambiguous name results in a breakpoint
9485 inserted on each possible match. However, if a unique choice must be made,
9486 then @value{GDBN} uses the menu to help you disambiguate the expression.
9487 For instance, printing the address of an overloaded function will result
9488 in the use of the menu.
9490 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9491 when an ambiguity is detected.
9493 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9494 an error due to the ambiguity and the command is aborted.
9496 @kindex show multiple-symbols
9497 @item show multiple-symbols
9498 Show the current value of the @code{multiple-symbols} setting.
9502 @section Program Variables
9504 The most common kind of expression to use is the name of a variable
9507 Variables in expressions are understood in the selected stack frame
9508 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9512 global (or file-static)
9519 visible according to the scope rules of the
9520 programming language from the point of execution in that frame
9523 @noindent This means that in the function
9538 you can examine and use the variable @code{a} whenever your program is
9539 executing within the function @code{foo}, but you can only use or
9540 examine the variable @code{b} while your program is executing inside
9541 the block where @code{b} is declared.
9543 @cindex variable name conflict
9544 There is an exception: you can refer to a variable or function whose
9545 scope is a single source file even if the current execution point is not
9546 in this file. But it is possible to have more than one such variable or
9547 function with the same name (in different source files). If that
9548 happens, referring to that name has unpredictable effects. If you wish,
9549 you can specify a static variable in a particular function or file by
9550 using the colon-colon (@code{::}) notation:
9552 @cindex colon-colon, context for variables/functions
9554 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9555 @cindex @code{::}, context for variables/functions
9558 @var{file}::@var{variable}
9559 @var{function}::@var{variable}
9563 Here @var{file} or @var{function} is the name of the context for the
9564 static @var{variable}. In the case of file names, you can use quotes to
9565 make sure @value{GDBN} parses the file name as a single word---for example,
9566 to print a global value of @code{x} defined in @file{f2.c}:
9569 (@value{GDBP}) p 'f2.c'::x
9572 The @code{::} notation is normally used for referring to
9573 static variables, since you typically disambiguate uses of local variables
9574 in functions by selecting the appropriate frame and using the
9575 simple name of the variable. However, you may also use this notation
9576 to refer to local variables in frames enclosing the selected frame:
9585 process (a); /* Stop here */
9596 For example, if there is a breakpoint at the commented line,
9597 here is what you might see
9598 when the program stops after executing the call @code{bar(0)}:
9603 (@value{GDBP}) p bar::a
9606 #2 0x080483d0 in foo (a=5) at foobar.c:12
9609 (@value{GDBP}) p bar::a
9613 @cindex C@t{++} scope resolution
9614 These uses of @samp{::} are very rarely in conflict with the very
9615 similar use of the same notation in C@t{++}. When they are in
9616 conflict, the C@t{++} meaning takes precedence; however, this can be
9617 overridden by quoting the file or function name with single quotes.
9619 For example, suppose the program is stopped in a method of a class
9620 that has a field named @code{includefile}, and there is also an
9621 include file named @file{includefile} that defines a variable,
9625 (@value{GDBP}) p includefile
9627 (@value{GDBP}) p includefile::some_global
9628 A syntax error in expression, near `'.
9629 (@value{GDBP}) p 'includefile'::some_global
9633 @cindex wrong values
9634 @cindex variable values, wrong
9635 @cindex function entry/exit, wrong values of variables
9636 @cindex optimized code, wrong values of variables
9638 @emph{Warning:} Occasionally, a local variable may appear to have the
9639 wrong value at certain points in a function---just after entry to a new
9640 scope, and just before exit.
9642 You may see this problem when you are stepping by machine instructions.
9643 This is because, on most machines, it takes more than one instruction to
9644 set up a stack frame (including local variable definitions); if you are
9645 stepping by machine instructions, variables may appear to have the wrong
9646 values until the stack frame is completely built. On exit, it usually
9647 also takes more than one machine instruction to destroy a stack frame;
9648 after you begin stepping through that group of instructions, local
9649 variable definitions may be gone.
9651 This may also happen when the compiler does significant optimizations.
9652 To be sure of always seeing accurate values, turn off all optimization
9655 @cindex ``No symbol "foo" in current context''
9656 Another possible effect of compiler optimizations is to optimize
9657 unused variables out of existence, or assign variables to registers (as
9658 opposed to memory addresses). Depending on the support for such cases
9659 offered by the debug info format used by the compiler, @value{GDBN}
9660 might not be able to display values for such local variables. If that
9661 happens, @value{GDBN} will print a message like this:
9664 No symbol "foo" in current context.
9667 To solve such problems, either recompile without optimizations, or use a
9668 different debug info format, if the compiler supports several such
9669 formats. @xref{Compilation}, for more information on choosing compiler
9670 options. @xref{C, ,C and C@t{++}}, for more information about debug
9671 info formats that are best suited to C@t{++} programs.
9673 If you ask to print an object whose contents are unknown to
9674 @value{GDBN}, e.g., because its data type is not completely specified
9675 by the debug information, @value{GDBN} will say @samp{<incomplete
9676 type>}. @xref{Symbols, incomplete type}, for more about this.
9678 @cindex no debug info variables
9679 If you try to examine or use the value of a (global) variable for
9680 which @value{GDBN} has no type information, e.g., because the program
9681 includes no debug information, @value{GDBN} displays an error message.
9682 @xref{Symbols, unknown type}, for more about unknown types. If you
9683 cast the variable to its declared type, @value{GDBN} gets the
9684 variable's value using the cast-to type as the variable's type. For
9685 example, in a C program:
9688 (@value{GDBP}) p var
9689 'var' has unknown type; cast it to its declared type
9690 (@value{GDBP}) p (float) var
9694 If you append @kbd{@@entry} string to a function parameter name you get its
9695 value at the time the function got called. If the value is not available an
9696 error message is printed. Entry values are available only with some compilers.
9697 Entry values are normally also printed at the function parameter list according
9698 to @ref{set print entry-values}.
9701 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9707 (gdb) print i@@entry
9711 Strings are identified as arrays of @code{char} values without specified
9712 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9713 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9714 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9715 defines literal string type @code{"char"} as @code{char} without a sign.
9720 signed char var1[] = "A";
9723 You get during debugging
9728 $2 = @{65 'A', 0 '\0'@}
9732 @section Artificial Arrays
9734 @cindex artificial array
9736 @kindex @@@r{, referencing memory as an array}
9737 It is often useful to print out several successive objects of the
9738 same type in memory; a section of an array, or an array of
9739 dynamically determined size for which only a pointer exists in the
9742 You can do this by referring to a contiguous span of memory as an
9743 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9744 operand of @samp{@@} should be the first element of the desired array
9745 and be an individual object. The right operand should be the desired length
9746 of the array. The result is an array value whose elements are all of
9747 the type of the left argument. The first element is actually the left
9748 argument; the second element comes from bytes of memory immediately
9749 following those that hold the first element, and so on. Here is an
9750 example. If a program says
9753 int *array = (int *) malloc (len * sizeof (int));
9757 you can print the contents of @code{array} with
9763 The left operand of @samp{@@} must reside in memory. Array values made
9764 with @samp{@@} in this way behave just like other arrays in terms of
9765 subscripting, and are coerced to pointers when used in expressions.
9766 Artificial arrays most often appear in expressions via the value history
9767 (@pxref{Value History, ,Value History}), after printing one out.
9769 Another way to create an artificial array is to use a cast.
9770 This re-interprets a value as if it were an array.
9771 The value need not be in memory:
9773 (@value{GDBP}) p/x (short[2])0x12345678
9774 $1 = @{0x1234, 0x5678@}
9777 As a convenience, if you leave the array length out (as in
9778 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9779 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9781 (@value{GDBP}) p/x (short[])0x12345678
9782 $2 = @{0x1234, 0x5678@}
9785 Sometimes the artificial array mechanism is not quite enough; in
9786 moderately complex data structures, the elements of interest may not
9787 actually be adjacent---for example, if you are interested in the values
9788 of pointers in an array. One useful work-around in this situation is
9789 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9790 Variables}) as a counter in an expression that prints the first
9791 interesting value, and then repeat that expression via @key{RET}. For
9792 instance, suppose you have an array @code{dtab} of pointers to
9793 structures, and you are interested in the values of a field @code{fv}
9794 in each structure. Here is an example of what you might type:
9804 @node Output Formats
9805 @section Output Formats
9807 @cindex formatted output
9808 @cindex output formats
9809 By default, @value{GDBN} prints a value according to its data type. Sometimes
9810 this is not what you want. For example, you might want to print a number
9811 in hex, or a pointer in decimal. Or you might want to view data in memory
9812 at a certain address as a character string or as an instruction. To do
9813 these things, specify an @dfn{output format} when you print a value.
9815 The simplest use of output formats is to say how to print a value
9816 already computed. This is done by starting the arguments of the
9817 @code{print} command with a slash and a format letter. The format
9818 letters supported are:
9822 Regard the bits of the value as an integer, and print the integer in
9826 Print as integer in signed decimal.
9829 Print as integer in unsigned decimal.
9832 Print as integer in octal.
9835 Print as integer in binary. The letter @samp{t} stands for ``two''.
9836 @footnote{@samp{b} cannot be used because these format letters are also
9837 used with the @code{x} command, where @samp{b} stands for ``byte'';
9838 see @ref{Memory,,Examining Memory}.}
9841 @cindex unknown address, locating
9842 @cindex locate address
9843 Print as an address, both absolute in hexadecimal and as an offset from
9844 the nearest preceding symbol. You can use this format used to discover
9845 where (in what function) an unknown address is located:
9848 (@value{GDBP}) p/a 0x54320
9849 $3 = 0x54320 <_initialize_vx+396>
9853 The command @code{info symbol 0x54320} yields similar results.
9854 @xref{Symbols, info symbol}.
9857 Regard as an integer and print it as a character constant. This
9858 prints both the numerical value and its character representation. The
9859 character representation is replaced with the octal escape @samp{\nnn}
9860 for characters outside the 7-bit @sc{ascii} range.
9862 Without this format, @value{GDBN} displays @code{char},
9863 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9864 constants. Single-byte members of vectors are displayed as integer
9868 Regard the bits of the value as a floating point number and print
9869 using typical floating point syntax.
9872 @cindex printing strings
9873 @cindex printing byte arrays
9874 Regard as a string, if possible. With this format, pointers to single-byte
9875 data are displayed as null-terminated strings and arrays of single-byte data
9876 are displayed as fixed-length strings. Other values are displayed in their
9879 Without this format, @value{GDBN} displays pointers to and arrays of
9880 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9881 strings. Single-byte members of a vector are displayed as an integer
9885 Like @samp{x} formatting, the value is treated as an integer and
9886 printed as hexadecimal, but leading zeros are printed to pad the value
9887 to the size of the integer type.
9890 @cindex raw printing
9891 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9892 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9893 Printing}). This typically results in a higher-level display of the
9894 value's contents. The @samp{r} format bypasses any Python
9895 pretty-printer which might exist.
9898 For example, to print the program counter in hex (@pxref{Registers}), type
9905 Note that no space is required before the slash; this is because command
9906 names in @value{GDBN} cannot contain a slash.
9908 To reprint the last value in the value history with a different format,
9909 you can use the @code{print} command with just a format and no
9910 expression. For example, @samp{p/x} reprints the last value in hex.
9913 @section Examining Memory
9915 You can use the command @code{x} (for ``examine'') to examine memory in
9916 any of several formats, independently of your program's data types.
9918 @cindex examining memory
9920 @kindex x @r{(examine memory)}
9921 @item x/@var{nfu} @var{addr}
9924 Use the @code{x} command to examine memory.
9927 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9928 much memory to display and how to format it; @var{addr} is an
9929 expression giving the address where you want to start displaying memory.
9930 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9931 Several commands set convenient defaults for @var{addr}.
9934 @item @var{n}, the repeat count
9935 The repeat count is a decimal integer; the default is 1. It specifies
9936 how much memory (counting by units @var{u}) to display. If a negative
9937 number is specified, memory is examined backward from @var{addr}.
9938 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9941 @item @var{f}, the display format
9942 The display format is one of the formats used by @code{print}
9943 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9944 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9945 The default is @samp{x} (hexadecimal) initially. The default changes
9946 each time you use either @code{x} or @code{print}.
9948 @item @var{u}, the unit size
9949 The unit size is any of
9955 Halfwords (two bytes).
9957 Words (four bytes). This is the initial default.
9959 Giant words (eight bytes).
9962 Each time you specify a unit size with @code{x}, that size becomes the
9963 default unit the next time you use @code{x}. For the @samp{i} format,
9964 the unit size is ignored and is normally not written. For the @samp{s} format,
9965 the unit size defaults to @samp{b}, unless it is explicitly given.
9966 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9967 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9968 Note that the results depend on the programming language of the
9969 current compilation unit. If the language is C, the @samp{s}
9970 modifier will use the UTF-16 encoding while @samp{w} will use
9971 UTF-32. The encoding is set by the programming language and cannot
9974 @item @var{addr}, starting display address
9975 @var{addr} is the address where you want @value{GDBN} to begin displaying
9976 memory. The expression need not have a pointer value (though it may);
9977 it is always interpreted as an integer address of a byte of memory.
9978 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9979 @var{addr} is usually just after the last address examined---but several
9980 other commands also set the default address: @code{info breakpoints} (to
9981 the address of the last breakpoint listed), @code{info line} (to the
9982 starting address of a line), and @code{print} (if you use it to display
9983 a value from memory).
9986 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9987 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9988 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9989 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9990 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9992 You can also specify a negative repeat count to examine memory backward
9993 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9994 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9996 Since the letters indicating unit sizes are all distinct from the
9997 letters specifying output formats, you do not have to remember whether
9998 unit size or format comes first; either order works. The output
9999 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
10000 (However, the count @var{n} must come first; @samp{wx4} does not work.)
10002 Even though the unit size @var{u} is ignored for the formats @samp{s}
10003 and @samp{i}, you might still want to use a count @var{n}; for example,
10004 @samp{3i} specifies that you want to see three machine instructions,
10005 including any operands. For convenience, especially when used with
10006 the @code{display} command, the @samp{i} format also prints branch delay
10007 slot instructions, if any, beyond the count specified, which immediately
10008 follow the last instruction that is within the count. The command
10009 @code{disassemble} gives an alternative way of inspecting machine
10010 instructions; see @ref{Machine Code,,Source and Machine Code}.
10012 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
10013 the command displays null-terminated strings or instructions before the given
10014 address as many as the absolute value of the given number. For the @samp{i}
10015 format, we use line number information in the debug info to accurately locate
10016 instruction boundaries while disassembling backward. If line info is not
10017 available, the command stops examining memory with an error message.
10019 All the defaults for the arguments to @code{x} are designed to make it
10020 easy to continue scanning memory with minimal specifications each time
10021 you use @code{x}. For example, after you have inspected three machine
10022 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10023 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10024 the repeat count @var{n} is used again; the other arguments default as
10025 for successive uses of @code{x}.
10027 When examining machine instructions, the instruction at current program
10028 counter is shown with a @code{=>} marker. For example:
10031 (@value{GDBP}) x/5i $pc-6
10032 0x804837f <main+11>: mov %esp,%ebp
10033 0x8048381 <main+13>: push %ecx
10034 0x8048382 <main+14>: sub $0x4,%esp
10035 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10036 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10039 @cindex @code{$_}, @code{$__}, and value history
10040 The addresses and contents printed by the @code{x} command are not saved
10041 in the value history because there is often too much of them and they
10042 would get in the way. Instead, @value{GDBN} makes these values available for
10043 subsequent use in expressions as values of the convenience variables
10044 @code{$_} and @code{$__}. After an @code{x} command, the last address
10045 examined is available for use in expressions in the convenience variable
10046 @code{$_}. The contents of that address, as examined, are available in
10047 the convenience variable @code{$__}.
10049 If the @code{x} command has a repeat count, the address and contents saved
10050 are from the last memory unit printed; this is not the same as the last
10051 address printed if several units were printed on the last line of output.
10053 @anchor{addressable memory unit}
10054 @cindex addressable memory unit
10055 Most targets have an addressable memory unit size of 8 bits. This means
10056 that to each memory address are associated 8 bits of data. Some
10057 targets, however, have other addressable memory unit sizes.
10058 Within @value{GDBN} and this document, the term
10059 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
10060 when explicitly referring to a chunk of data of that size. The word
10061 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
10062 the addressable memory unit size of the target. For most systems,
10063 addressable memory unit is a synonym of byte.
10065 @cindex remote memory comparison
10066 @cindex target memory comparison
10067 @cindex verify remote memory image
10068 @cindex verify target memory image
10069 When you are debugging a program running on a remote target machine
10070 (@pxref{Remote Debugging}), you may wish to verify the program's image
10071 in the remote machine's memory against the executable file you
10072 downloaded to the target. Or, on any target, you may want to check
10073 whether the program has corrupted its own read-only sections. The
10074 @code{compare-sections} command is provided for such situations.
10077 @kindex compare-sections
10078 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
10079 Compare the data of a loadable section @var{section-name} in the
10080 executable file of the program being debugged with the same section in
10081 the target machine's memory, and report any mismatches. With no
10082 arguments, compares all loadable sections. With an argument of
10083 @code{-r}, compares all loadable read-only sections.
10085 Note: for remote targets, this command can be accelerated if the
10086 target supports computing the CRC checksum of a block of memory
10087 (@pxref{qCRC packet}).
10091 @section Automatic Display
10092 @cindex automatic display
10093 @cindex display of expressions
10095 If you find that you want to print the value of an expression frequently
10096 (to see how it changes), you might want to add it to the @dfn{automatic
10097 display list} so that @value{GDBN} prints its value each time your program stops.
10098 Each expression added to the list is given a number to identify it;
10099 to remove an expression from the list, you specify that number.
10100 The automatic display looks like this:
10104 3: bar[5] = (struct hack *) 0x3804
10108 This display shows item numbers, expressions and their current values. As with
10109 displays you request manually using @code{x} or @code{print}, you can
10110 specify the output format you prefer; in fact, @code{display} decides
10111 whether to use @code{print} or @code{x} depending your format
10112 specification---it uses @code{x} if you specify either the @samp{i}
10113 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
10117 @item display @var{expr}
10118 Add the expression @var{expr} to the list of expressions to display
10119 each time your program stops. @xref{Expressions, ,Expressions}.
10121 @code{display} does not repeat if you press @key{RET} again after using it.
10123 @item display/@var{fmt} @var{expr}
10124 For @var{fmt} specifying only a display format and not a size or
10125 count, add the expression @var{expr} to the auto-display list but
10126 arrange to display it each time in the specified format @var{fmt}.
10127 @xref{Output Formats,,Output Formats}.
10129 @item display/@var{fmt} @var{addr}
10130 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
10131 number of units, add the expression @var{addr} as a memory address to
10132 be examined each time your program stops. Examining means in effect
10133 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
10136 For example, @samp{display/i $pc} can be helpful, to see the machine
10137 instruction about to be executed each time execution stops (@samp{$pc}
10138 is a common name for the program counter; @pxref{Registers, ,Registers}).
10141 @kindex delete display
10143 @item undisplay @var{dnums}@dots{}
10144 @itemx delete display @var{dnums}@dots{}
10145 Remove items from the list of expressions to display. Specify the
10146 numbers of the displays that you want affected with the command
10147 argument @var{dnums}. It can be a single display number, one of the
10148 numbers shown in the first field of the @samp{info display} display;
10149 or it could be a range of display numbers, as in @code{2-4}.
10151 @code{undisplay} does not repeat if you press @key{RET} after using it.
10152 (Otherwise you would just get the error @samp{No display number @dots{}}.)
10154 @kindex disable display
10155 @item disable display @var{dnums}@dots{}
10156 Disable the display of item numbers @var{dnums}. A disabled display
10157 item is not printed automatically, but is not forgotten. It may be
10158 enabled again later. Specify the numbers of the displays that you
10159 want affected with the command argument @var{dnums}. It can be a
10160 single display number, one of the numbers shown in the first field of
10161 the @samp{info display} display; or it could be a range of display
10162 numbers, as in @code{2-4}.
10164 @kindex enable display
10165 @item enable display @var{dnums}@dots{}
10166 Enable display of item numbers @var{dnums}. It becomes effective once
10167 again in auto display of its expression, until you specify otherwise.
10168 Specify the numbers of the displays that you want affected with the
10169 command argument @var{dnums}. It can be a single display number, one
10170 of the numbers shown in the first field of the @samp{info display}
10171 display; or it could be a range of display numbers, as in @code{2-4}.
10174 Display the current values of the expressions on the list, just as is
10175 done when your program stops.
10177 @kindex info display
10179 Print the list of expressions previously set up to display
10180 automatically, each one with its item number, but without showing the
10181 values. This includes disabled expressions, which are marked as such.
10182 It also includes expressions which would not be displayed right now
10183 because they refer to automatic variables not currently available.
10186 @cindex display disabled out of scope
10187 If a display expression refers to local variables, then it does not make
10188 sense outside the lexical context for which it was set up. Such an
10189 expression is disabled when execution enters a context where one of its
10190 variables is not defined. For example, if you give the command
10191 @code{display last_char} while inside a function with an argument
10192 @code{last_char}, @value{GDBN} displays this argument while your program
10193 continues to stop inside that function. When it stops elsewhere---where
10194 there is no variable @code{last_char}---the display is disabled
10195 automatically. The next time your program stops where @code{last_char}
10196 is meaningful, you can enable the display expression once again.
10198 @node Print Settings
10199 @section Print Settings
10201 @cindex format options
10202 @cindex print settings
10203 @value{GDBN} provides the following ways to control how arrays, structures,
10204 and symbols are printed.
10207 These settings are useful for debugging programs in any language:
10211 @item set print address
10212 @itemx set print address on
10213 @cindex print/don't print memory addresses
10214 @value{GDBN} prints memory addresses showing the location of stack
10215 traces, structure values, pointer values, breakpoints, and so forth,
10216 even when it also displays the contents of those addresses. The default
10217 is @code{on}. For example, this is what a stack frame display looks like with
10218 @code{set print address on}:
10223 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
10225 530 if (lquote != def_lquote)
10229 @item set print address off
10230 Do not print addresses when displaying their contents. For example,
10231 this is the same stack frame displayed with @code{set print address off}:
10235 (@value{GDBP}) set print addr off
10237 #0 set_quotes (lq="<<", rq=">>") at input.c:530
10238 530 if (lquote != def_lquote)
10242 You can use @samp{set print address off} to eliminate all machine
10243 dependent displays from the @value{GDBN} interface. For example, with
10244 @code{print address off}, you should get the same text for backtraces on
10245 all machines---whether or not they involve pointer arguments.
10248 @item show print address
10249 Show whether or not addresses are to be printed.
10252 When @value{GDBN} prints a symbolic address, it normally prints the
10253 closest earlier symbol plus an offset. If that symbol does not uniquely
10254 identify the address (for example, it is a name whose scope is a single
10255 source file), you may need to clarify. One way to do this is with
10256 @code{info line}, for example @samp{info line *0x4537}. Alternately,
10257 you can set @value{GDBN} to print the source file and line number when
10258 it prints a symbolic address:
10261 @item set print symbol-filename on
10262 @cindex source file and line of a symbol
10263 @cindex symbol, source file and line
10264 Tell @value{GDBN} to print the source file name and line number of a
10265 symbol in the symbolic form of an address.
10267 @item set print symbol-filename off
10268 Do not print source file name and line number of a symbol. This is the
10271 @item show print symbol-filename
10272 Show whether or not @value{GDBN} will print the source file name and
10273 line number of a symbol in the symbolic form of an address.
10276 Another situation where it is helpful to show symbol filenames and line
10277 numbers is when disassembling code; @value{GDBN} shows you the line
10278 number and source file that corresponds to each instruction.
10280 Also, you may wish to see the symbolic form only if the address being
10281 printed is reasonably close to the closest earlier symbol:
10284 @item set print max-symbolic-offset @var{max-offset}
10285 @itemx set print max-symbolic-offset unlimited
10286 @cindex maximum value for offset of closest symbol
10287 Tell @value{GDBN} to only display the symbolic form of an address if the
10288 offset between the closest earlier symbol and the address is less than
10289 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
10290 to always print the symbolic form of an address if any symbol precedes
10291 it. Zero is equivalent to @code{unlimited}.
10293 @item show print max-symbolic-offset
10294 Ask how large the maximum offset is that @value{GDBN} prints in a
10298 @cindex wild pointer, interpreting
10299 @cindex pointer, finding referent
10300 If you have a pointer and you are not sure where it points, try
10301 @samp{set print symbol-filename on}. Then you can determine the name
10302 and source file location of the variable where it points, using
10303 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
10304 For example, here @value{GDBN} shows that a variable @code{ptt} points
10305 at another variable @code{t}, defined in @file{hi2.c}:
10308 (@value{GDBP}) set print symbol-filename on
10309 (@value{GDBP}) p/a ptt
10310 $4 = 0xe008 <t in hi2.c>
10314 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
10315 does not show the symbol name and filename of the referent, even with
10316 the appropriate @code{set print} options turned on.
10319 You can also enable @samp{/a}-like formatting all the time using
10320 @samp{set print symbol on}:
10323 @item set print symbol on
10324 Tell @value{GDBN} to print the symbol corresponding to an address, if
10327 @item set print symbol off
10328 Tell @value{GDBN} not to print the symbol corresponding to an
10329 address. In this mode, @value{GDBN} will still print the symbol
10330 corresponding to pointers to functions. This is the default.
10332 @item show print symbol
10333 Show whether @value{GDBN} will display the symbol corresponding to an
10337 Other settings control how different kinds of objects are printed:
10340 @item set print array
10341 @itemx set print array on
10342 @cindex pretty print arrays
10343 Pretty print arrays. This format is more convenient to read,
10344 but uses more space. The default is off.
10346 @item set print array off
10347 Return to compressed format for arrays.
10349 @item show print array
10350 Show whether compressed or pretty format is selected for displaying
10353 @cindex print array indexes
10354 @item set print array-indexes
10355 @itemx set print array-indexes on
10356 Print the index of each element when displaying arrays. May be more
10357 convenient to locate a given element in the array or quickly find the
10358 index of a given element in that printed array. The default is off.
10360 @item set print array-indexes off
10361 Stop printing element indexes when displaying arrays.
10363 @item show print array-indexes
10364 Show whether the index of each element is printed when displaying
10367 @item set print elements @var{number-of-elements}
10368 @itemx set print elements unlimited
10369 @cindex number of array elements to print
10370 @cindex limit on number of printed array elements
10371 Set a limit on how many elements of an array @value{GDBN} will print.
10372 If @value{GDBN} is printing a large array, it stops printing after it has
10373 printed the number of elements set by the @code{set print elements} command.
10374 This limit also applies to the display of strings.
10375 When @value{GDBN} starts, this limit is set to 200.
10376 Setting @var{number-of-elements} to @code{unlimited} or zero means
10377 that the number of elements to print is unlimited.
10379 @item show print elements
10380 Display the number of elements of a large array that @value{GDBN} will print.
10381 If the number is 0, then the printing is unlimited.
10383 @item set print frame-arguments @var{value}
10384 @kindex set print frame-arguments
10385 @cindex printing frame argument values
10386 @cindex print all frame argument values
10387 @cindex print frame argument values for scalars only
10388 @cindex do not print frame argument values
10389 This command allows to control how the values of arguments are printed
10390 when the debugger prints a frame (@pxref{Frames}). The possible
10395 The values of all arguments are printed.
10398 Print the value of an argument only if it is a scalar. The value of more
10399 complex arguments such as arrays, structures, unions, etc, is replaced
10400 by @code{@dots{}}. This is the default. Here is an example where
10401 only scalar arguments are shown:
10404 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
10409 None of the argument values are printed. Instead, the value of each argument
10410 is replaced by @code{@dots{}}. In this case, the example above now becomes:
10413 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
10418 By default, only scalar arguments are printed. This command can be used
10419 to configure the debugger to print the value of all arguments, regardless
10420 of their type. However, it is often advantageous to not print the value
10421 of more complex parameters. For instance, it reduces the amount of
10422 information printed in each frame, making the backtrace more readable.
10423 Also, it improves performance when displaying Ada frames, because
10424 the computation of large arguments can sometimes be CPU-intensive,
10425 especially in large applications. Setting @code{print frame-arguments}
10426 to @code{scalars} (the default) or @code{none} avoids this computation,
10427 thus speeding up the display of each Ada frame.
10429 @item show print frame-arguments
10430 Show how the value of arguments should be displayed when printing a frame.
10432 @item set print raw frame-arguments on
10433 Print frame arguments in raw, non pretty-printed, form.
10435 @item set print raw frame-arguments off
10436 Print frame arguments in pretty-printed form, if there is a pretty-printer
10437 for the value (@pxref{Pretty Printing}),
10438 otherwise print the value in raw form.
10439 This is the default.
10441 @item show print raw frame-arguments
10442 Show whether to print frame arguments in raw form.
10444 @anchor{set print entry-values}
10445 @item set print entry-values @var{value}
10446 @kindex set print entry-values
10447 Set printing of frame argument values at function entry. In some cases
10448 @value{GDBN} can determine the value of function argument which was passed by
10449 the function caller, even if the value was modified inside the called function
10450 and therefore is different. With optimized code, the current value could be
10451 unavailable, but the entry value may still be known.
10453 The default value is @code{default} (see below for its description). Older
10454 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10455 this feature will behave in the @code{default} setting the same way as with the
10458 This functionality is currently supported only by DWARF 2 debugging format and
10459 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10460 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10463 The @var{value} parameter can be one of the following:
10467 Print only actual parameter values, never print values from function entry
10471 #0 different (val=6)
10472 #0 lost (val=<optimized out>)
10474 #0 invalid (val=<optimized out>)
10478 Print only parameter values from function entry point. The actual parameter
10479 values are never printed.
10481 #0 equal (val@@entry=5)
10482 #0 different (val@@entry=5)
10483 #0 lost (val@@entry=5)
10484 #0 born (val@@entry=<optimized out>)
10485 #0 invalid (val@@entry=<optimized out>)
10489 Print only parameter values from function entry point. If value from function
10490 entry point is not known while the actual value is known, print the actual
10491 value for such parameter.
10493 #0 equal (val@@entry=5)
10494 #0 different (val@@entry=5)
10495 #0 lost (val@@entry=5)
10497 #0 invalid (val@@entry=<optimized out>)
10501 Print actual parameter values. If actual parameter value is not known while
10502 value from function entry point is known, print the entry point value for such
10506 #0 different (val=6)
10507 #0 lost (val@@entry=5)
10509 #0 invalid (val=<optimized out>)
10513 Always print both the actual parameter value and its value from function entry
10514 point, even if values of one or both are not available due to compiler
10517 #0 equal (val=5, val@@entry=5)
10518 #0 different (val=6, val@@entry=5)
10519 #0 lost (val=<optimized out>, val@@entry=5)
10520 #0 born (val=10, val@@entry=<optimized out>)
10521 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10525 Print the actual parameter value if it is known and also its value from
10526 function entry point if it is known. If neither is known, print for the actual
10527 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10528 values are known and identical, print the shortened
10529 @code{param=param@@entry=VALUE} notation.
10531 #0 equal (val=val@@entry=5)
10532 #0 different (val=6, val@@entry=5)
10533 #0 lost (val@@entry=5)
10535 #0 invalid (val=<optimized out>)
10539 Always print the actual parameter value. Print also its value from function
10540 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10541 if both values are known and identical, print the shortened
10542 @code{param=param@@entry=VALUE} notation.
10544 #0 equal (val=val@@entry=5)
10545 #0 different (val=6, val@@entry=5)
10546 #0 lost (val=<optimized out>, val@@entry=5)
10548 #0 invalid (val=<optimized out>)
10552 For analysis messages on possible failures of frame argument values at function
10553 entry resolution see @ref{set debug entry-values}.
10555 @item show print entry-values
10556 Show the method being used for printing of frame argument values at function
10559 @item set print repeats @var{number-of-repeats}
10560 @itemx set print repeats unlimited
10561 @cindex repeated array elements
10562 Set the threshold for suppressing display of repeated array
10563 elements. When the number of consecutive identical elements of an
10564 array exceeds the threshold, @value{GDBN} prints the string
10565 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10566 identical repetitions, instead of displaying the identical elements
10567 themselves. Setting the threshold to @code{unlimited} or zero will
10568 cause all elements to be individually printed. The default threshold
10571 @item show print repeats
10572 Display the current threshold for printing repeated identical
10575 @item set print null-stop
10576 @cindex @sc{null} elements in arrays
10577 Cause @value{GDBN} to stop printing the characters of an array when the first
10578 @sc{null} is encountered. This is useful when large arrays actually
10579 contain only short strings.
10580 The default is off.
10582 @item show print null-stop
10583 Show whether @value{GDBN} stops printing an array on the first
10584 @sc{null} character.
10586 @item set print pretty on
10587 @cindex print structures in indented form
10588 @cindex indentation in structure display
10589 Cause @value{GDBN} to print structures in an indented format with one member
10590 per line, like this:
10605 @item set print pretty off
10606 Cause @value{GDBN} to print structures in a compact format, like this:
10610 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10611 meat = 0x54 "Pork"@}
10616 This is the default format.
10618 @item show print pretty
10619 Show which format @value{GDBN} is using to print structures.
10621 @item set print sevenbit-strings on
10622 @cindex eight-bit characters in strings
10623 @cindex octal escapes in strings
10624 Print using only seven-bit characters; if this option is set,
10625 @value{GDBN} displays any eight-bit characters (in strings or
10626 character values) using the notation @code{\}@var{nnn}. This setting is
10627 best if you are working in English (@sc{ascii}) and you use the
10628 high-order bit of characters as a marker or ``meta'' bit.
10630 @item set print sevenbit-strings off
10631 Print full eight-bit characters. This allows the use of more
10632 international character sets, and is the default.
10634 @item show print sevenbit-strings
10635 Show whether or not @value{GDBN} is printing only seven-bit characters.
10637 @item set print union on
10638 @cindex unions in structures, printing
10639 Tell @value{GDBN} to print unions which are contained in structures
10640 and other unions. This is the default setting.
10642 @item set print union off
10643 Tell @value{GDBN} not to print unions which are contained in
10644 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10647 @item show print union
10648 Ask @value{GDBN} whether or not it will print unions which are contained in
10649 structures and other unions.
10651 For example, given the declarations
10654 typedef enum @{Tree, Bug@} Species;
10655 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10656 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10667 struct thing foo = @{Tree, @{Acorn@}@};
10671 with @code{set print union on} in effect @samp{p foo} would print
10674 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10678 and with @code{set print union off} in effect it would print
10681 $1 = @{it = Tree, form = @{...@}@}
10685 @code{set print union} affects programs written in C-like languages
10691 These settings are of interest when debugging C@t{++} programs:
10694 @cindex demangling C@t{++} names
10695 @item set print demangle
10696 @itemx set print demangle on
10697 Print C@t{++} names in their source form rather than in the encoded
10698 (``mangled'') form passed to the assembler and linker for type-safe
10699 linkage. The default is on.
10701 @item show print demangle
10702 Show whether C@t{++} names are printed in mangled or demangled form.
10704 @item set print asm-demangle
10705 @itemx set print asm-demangle on
10706 Print C@t{++} names in their source form rather than their mangled form, even
10707 in assembler code printouts such as instruction disassemblies.
10708 The default is off.
10710 @item show print asm-demangle
10711 Show whether C@t{++} names in assembly listings are printed in mangled
10714 @cindex C@t{++} symbol decoding style
10715 @cindex symbol decoding style, C@t{++}
10716 @kindex set demangle-style
10717 @item set demangle-style @var{style}
10718 Choose among several encoding schemes used by different compilers to represent
10719 C@t{++} names. If you omit @var{style}, you will see a list of possible
10720 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
10721 decoding style by inspecting your program.
10723 @item show demangle-style
10724 Display the encoding style currently in use for decoding C@t{++} symbols.
10726 @item set print object
10727 @itemx set print object on
10728 @cindex derived type of an object, printing
10729 @cindex display derived types
10730 When displaying a pointer to an object, identify the @emph{actual}
10731 (derived) type of the object rather than the @emph{declared} type, using
10732 the virtual function table. Note that the virtual function table is
10733 required---this feature can only work for objects that have run-time
10734 type identification; a single virtual method in the object's declared
10735 type is sufficient. Note that this setting is also taken into account when
10736 working with variable objects via MI (@pxref{GDB/MI}).
10738 @item set print object off
10739 Display only the declared type of objects, without reference to the
10740 virtual function table. This is the default setting.
10742 @item show print object
10743 Show whether actual, or declared, object types are displayed.
10745 @item set print static-members
10746 @itemx set print static-members on
10747 @cindex static members of C@t{++} objects
10748 Print static members when displaying a C@t{++} object. The default is on.
10750 @item set print static-members off
10751 Do not print static members when displaying a C@t{++} object.
10753 @item show print static-members
10754 Show whether C@t{++} static members are printed or not.
10756 @item set print pascal_static-members
10757 @itemx set print pascal_static-members on
10758 @cindex static members of Pascal objects
10759 @cindex Pascal objects, static members display
10760 Print static members when displaying a Pascal object. The default is on.
10762 @item set print pascal_static-members off
10763 Do not print static members when displaying a Pascal object.
10765 @item show print pascal_static-members
10766 Show whether Pascal static members are printed or not.
10768 @c These don't work with HP ANSI C++ yet.
10769 @item set print vtbl
10770 @itemx set print vtbl on
10771 @cindex pretty print C@t{++} virtual function tables
10772 @cindex virtual functions (C@t{++}) display
10773 @cindex VTBL display
10774 Pretty print C@t{++} virtual function tables. The default is off.
10775 (The @code{vtbl} commands do not work on programs compiled with the HP
10776 ANSI C@t{++} compiler (@code{aCC}).)
10778 @item set print vtbl off
10779 Do not pretty print C@t{++} virtual function tables.
10781 @item show print vtbl
10782 Show whether C@t{++} virtual function tables are pretty printed, or not.
10785 @node Pretty Printing
10786 @section Pretty Printing
10788 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10789 Python code. It greatly simplifies the display of complex objects. This
10790 mechanism works for both MI and the CLI.
10793 * Pretty-Printer Introduction:: Introduction to pretty-printers
10794 * Pretty-Printer Example:: An example pretty-printer
10795 * Pretty-Printer Commands:: Pretty-printer commands
10798 @node Pretty-Printer Introduction
10799 @subsection Pretty-Printer Introduction
10801 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10802 registered for the value. If there is then @value{GDBN} invokes the
10803 pretty-printer to print the value. Otherwise the value is printed normally.
10805 Pretty-printers are normally named. This makes them easy to manage.
10806 The @samp{info pretty-printer} command will list all the installed
10807 pretty-printers with their names.
10808 If a pretty-printer can handle multiple data types, then its
10809 @dfn{subprinters} are the printers for the individual data types.
10810 Each such subprinter has its own name.
10811 The format of the name is @var{printer-name};@var{subprinter-name}.
10813 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10814 Typically they are automatically loaded and registered when the corresponding
10815 debug information is loaded, thus making them available without having to
10816 do anything special.
10818 There are three places where a pretty-printer can be registered.
10822 Pretty-printers registered globally are available when debugging
10826 Pretty-printers registered with a program space are available only
10827 when debugging that program.
10828 @xref{Progspaces In Python}, for more details on program spaces in Python.
10831 Pretty-printers registered with an objfile are loaded and unloaded
10832 with the corresponding objfile (e.g., shared library).
10833 @xref{Objfiles In Python}, for more details on objfiles in Python.
10836 @xref{Selecting Pretty-Printers}, for further information on how
10837 pretty-printers are selected,
10839 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10842 @node Pretty-Printer Example
10843 @subsection Pretty-Printer Example
10845 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10848 (@value{GDBP}) print s
10850 static npos = 4294967295,
10852 <std::allocator<char>> = @{
10853 <__gnu_cxx::new_allocator<char>> = @{
10854 <No data fields>@}, <No data fields>
10856 members of std::basic_string<char, std::char_traits<char>,
10857 std::allocator<char> >::_Alloc_hider:
10858 _M_p = 0x804a014 "abcd"
10863 With a pretty-printer for @code{std::string} only the contents are printed:
10866 (@value{GDBP}) print s
10870 @node Pretty-Printer Commands
10871 @subsection Pretty-Printer Commands
10872 @cindex pretty-printer commands
10875 @kindex info pretty-printer
10876 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10877 Print the list of installed pretty-printers.
10878 This includes disabled pretty-printers, which are marked as such.
10880 @var{object-regexp} is a regular expression matching the objects
10881 whose pretty-printers to list.
10882 Objects can be @code{global}, the program space's file
10883 (@pxref{Progspaces In Python}),
10884 and the object files within that program space (@pxref{Objfiles In Python}).
10885 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10886 looks up a printer from these three objects.
10888 @var{name-regexp} is a regular expression matching the name of the printers
10891 @kindex disable pretty-printer
10892 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10893 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10894 A disabled pretty-printer is not forgotten, it may be enabled again later.
10896 @kindex enable pretty-printer
10897 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10898 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10903 Suppose we have three pretty-printers installed: one from library1.so
10904 named @code{foo} that prints objects of type @code{foo}, and
10905 another from library2.so named @code{bar} that prints two types of objects,
10906 @code{bar1} and @code{bar2}.
10909 (gdb) info pretty-printer
10916 (gdb) info pretty-printer library2
10921 (gdb) disable pretty-printer library1
10923 2 of 3 printers enabled
10924 (gdb) info pretty-printer
10931 (gdb) disable pretty-printer library2 bar;bar1
10933 1 of 3 printers enabled
10934 (gdb) info pretty-printer library2
10941 (gdb) disable pretty-printer library2 bar
10943 0 of 3 printers enabled
10944 (gdb) info pretty-printer library2
10953 Note that for @code{bar} the entire printer can be disabled,
10954 as can each individual subprinter.
10956 @node Value History
10957 @section Value History
10959 @cindex value history
10960 @cindex history of values printed by @value{GDBN}
10961 Values printed by the @code{print} command are saved in the @value{GDBN}
10962 @dfn{value history}. This allows you to refer to them in other expressions.
10963 Values are kept until the symbol table is re-read or discarded
10964 (for example with the @code{file} or @code{symbol-file} commands).
10965 When the symbol table changes, the value history is discarded,
10966 since the values may contain pointers back to the types defined in the
10971 @cindex history number
10972 The values printed are given @dfn{history numbers} by which you can
10973 refer to them. These are successive integers starting with one.
10974 @code{print} shows you the history number assigned to a value by
10975 printing @samp{$@var{num} = } before the value; here @var{num} is the
10978 To refer to any previous value, use @samp{$} followed by the value's
10979 history number. The way @code{print} labels its output is designed to
10980 remind you of this. Just @code{$} refers to the most recent value in
10981 the history, and @code{$$} refers to the value before that.
10982 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10983 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10984 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10986 For example, suppose you have just printed a pointer to a structure and
10987 want to see the contents of the structure. It suffices to type
10993 If you have a chain of structures where the component @code{next} points
10994 to the next one, you can print the contents of the next one with this:
11001 You can print successive links in the chain by repeating this
11002 command---which you can do by just typing @key{RET}.
11004 Note that the history records values, not expressions. If the value of
11005 @code{x} is 4 and you type these commands:
11013 then the value recorded in the value history by the @code{print} command
11014 remains 4 even though the value of @code{x} has changed.
11017 @kindex show values
11019 Print the last ten values in the value history, with their item numbers.
11020 This is like @samp{p@ $$9} repeated ten times, except that @code{show
11021 values} does not change the history.
11023 @item show values @var{n}
11024 Print ten history values centered on history item number @var{n}.
11026 @item show values +
11027 Print ten history values just after the values last printed. If no more
11028 values are available, @code{show values +} produces no display.
11031 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
11032 same effect as @samp{show values +}.
11034 @node Convenience Vars
11035 @section Convenience Variables
11037 @cindex convenience variables
11038 @cindex user-defined variables
11039 @value{GDBN} provides @dfn{convenience variables} that you can use within
11040 @value{GDBN} to hold on to a value and refer to it later. These variables
11041 exist entirely within @value{GDBN}; they are not part of your program, and
11042 setting a convenience variable has no direct effect on further execution
11043 of your program. That is why you can use them freely.
11045 Convenience variables are prefixed with @samp{$}. Any name preceded by
11046 @samp{$} can be used for a convenience variable, unless it is one of
11047 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
11048 (Value history references, in contrast, are @emph{numbers} preceded
11049 by @samp{$}. @xref{Value History, ,Value History}.)
11051 You can save a value in a convenience variable with an assignment
11052 expression, just as you would set a variable in your program.
11056 set $foo = *object_ptr
11060 would save in @code{$foo} the value contained in the object pointed to by
11063 Using a convenience variable for the first time creates it, but its
11064 value is @code{void} until you assign a new value. You can alter the
11065 value with another assignment at any time.
11067 Convenience variables have no fixed types. You can assign a convenience
11068 variable any type of value, including structures and arrays, even if
11069 that variable already has a value of a different type. The convenience
11070 variable, when used as an expression, has the type of its current value.
11073 @kindex show convenience
11074 @cindex show all user variables and functions
11075 @item show convenience
11076 Print a list of convenience variables used so far, and their values,
11077 as well as a list of the convenience functions.
11078 Abbreviated @code{show conv}.
11080 @kindex init-if-undefined
11081 @cindex convenience variables, initializing
11082 @item init-if-undefined $@var{variable} = @var{expression}
11083 Set a convenience variable if it has not already been set. This is useful
11084 for user-defined commands that keep some state. It is similar, in concept,
11085 to using local static variables with initializers in C (except that
11086 convenience variables are global). It can also be used to allow users to
11087 override default values used in a command script.
11089 If the variable is already defined then the expression is not evaluated so
11090 any side-effects do not occur.
11093 One of the ways to use a convenience variable is as a counter to be
11094 incremented or a pointer to be advanced. For example, to print
11095 a field from successive elements of an array of structures:
11099 print bar[$i++]->contents
11103 Repeat that command by typing @key{RET}.
11105 Some convenience variables are created automatically by @value{GDBN} and given
11106 values likely to be useful.
11109 @vindex $_@r{, convenience variable}
11111 The variable @code{$_} is automatically set by the @code{x} command to
11112 the last address examined (@pxref{Memory, ,Examining Memory}). Other
11113 commands which provide a default address for @code{x} to examine also
11114 set @code{$_} to that address; these commands include @code{info line}
11115 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
11116 except when set by the @code{x} command, in which case it is a pointer
11117 to the type of @code{$__}.
11119 @vindex $__@r{, convenience variable}
11121 The variable @code{$__} is automatically set by the @code{x} command
11122 to the value found in the last address examined. Its type is chosen
11123 to match the format in which the data was printed.
11126 @vindex $_exitcode@r{, convenience variable}
11127 When the program being debugged terminates normally, @value{GDBN}
11128 automatically sets this variable to the exit code of the program, and
11129 resets @code{$_exitsignal} to @code{void}.
11132 @vindex $_exitsignal@r{, convenience variable}
11133 When the program being debugged dies due to an uncaught signal,
11134 @value{GDBN} automatically sets this variable to that signal's number,
11135 and resets @code{$_exitcode} to @code{void}.
11137 To distinguish between whether the program being debugged has exited
11138 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
11139 @code{$_exitsignal} is not @code{void}), the convenience function
11140 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
11141 Functions}). For example, considering the following source code:
11144 #include <signal.h>
11147 main (int argc, char *argv[])
11154 A valid way of telling whether the program being debugged has exited
11155 or signalled would be:
11158 (@value{GDBP}) define has_exited_or_signalled
11159 Type commands for definition of ``has_exited_or_signalled''.
11160 End with a line saying just ``end''.
11161 >if $_isvoid ($_exitsignal)
11162 >echo The program has exited\n
11164 >echo The program has signalled\n
11170 Program terminated with signal SIGALRM, Alarm clock.
11171 The program no longer exists.
11172 (@value{GDBP}) has_exited_or_signalled
11173 The program has signalled
11176 As can be seen, @value{GDBN} correctly informs that the program being
11177 debugged has signalled, since it calls @code{raise} and raises a
11178 @code{SIGALRM} signal. If the program being debugged had not called
11179 @code{raise}, then @value{GDBN} would report a normal exit:
11182 (@value{GDBP}) has_exited_or_signalled
11183 The program has exited
11187 The variable @code{$_exception} is set to the exception object being
11188 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
11191 @itemx $_probe_arg0@dots{}$_probe_arg11
11192 Arguments to a static probe. @xref{Static Probe Points}.
11195 @vindex $_sdata@r{, inspect, convenience variable}
11196 The variable @code{$_sdata} contains extra collected static tracepoint
11197 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
11198 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
11199 if extra static tracepoint data has not been collected.
11202 @vindex $_siginfo@r{, convenience variable}
11203 The variable @code{$_siginfo} contains extra signal information
11204 (@pxref{extra signal information}). Note that @code{$_siginfo}
11205 could be empty, if the application has not yet received any signals.
11206 For example, it will be empty before you execute the @code{run} command.
11209 @vindex $_tlb@r{, convenience variable}
11210 The variable @code{$_tlb} is automatically set when debugging
11211 applications running on MS-Windows in native mode or connected to
11212 gdbserver that supports the @code{qGetTIBAddr} request.
11213 @xref{General Query Packets}.
11214 This variable contains the address of the thread information block.
11217 The number of the current inferior. @xref{Inferiors and
11218 Programs, ,Debugging Multiple Inferiors and Programs}.
11221 The thread number of the current thread. @xref{thread numbers}.
11224 The global number of the current thread. @xref{global thread numbers}.
11228 @vindex $_gdb_major@r{, convenience variable}
11229 @vindex $_gdb_minor@r{, convenience variable}
11230 The major and minor version numbers of the running @value{GDBN}.
11231 Development snapshots and pretest versions have their minor version
11232 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
11233 the value 12 for @code{$_gdb_minor}. These variables allow you to
11234 write scripts that work with different versions of @value{GDBN}
11235 without errors caused by features unavailable in some of those
11239 @node Convenience Funs
11240 @section Convenience Functions
11242 @cindex convenience functions
11243 @value{GDBN} also supplies some @dfn{convenience functions}. These
11244 have a syntax similar to convenience variables. A convenience
11245 function can be used in an expression just like an ordinary function;
11246 however, a convenience function is implemented internally to
11249 These functions do not require @value{GDBN} to be configured with
11250 @code{Python} support, which means that they are always available.
11254 @item $_isvoid (@var{expr})
11255 @findex $_isvoid@r{, convenience function}
11256 Return one if the expression @var{expr} is @code{void}. Otherwise it
11259 A @code{void} expression is an expression where the type of the result
11260 is @code{void}. For example, you can examine a convenience variable
11261 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
11265 (@value{GDBP}) print $_exitcode
11267 (@value{GDBP}) print $_isvoid ($_exitcode)
11270 Starting program: ./a.out
11271 [Inferior 1 (process 29572) exited normally]
11272 (@value{GDBP}) print $_exitcode
11274 (@value{GDBP}) print $_isvoid ($_exitcode)
11278 In the example above, we used @code{$_isvoid} to check whether
11279 @code{$_exitcode} is @code{void} before and after the execution of the
11280 program being debugged. Before the execution there is no exit code to
11281 be examined, therefore @code{$_exitcode} is @code{void}. After the
11282 execution the program being debugged returned zero, therefore
11283 @code{$_exitcode} is zero, which means that it is not @code{void}
11286 The @code{void} expression can also be a call of a function from the
11287 program being debugged. For example, given the following function:
11296 The result of calling it inside @value{GDBN} is @code{void}:
11299 (@value{GDBP}) print foo ()
11301 (@value{GDBP}) print $_isvoid (foo ())
11303 (@value{GDBP}) set $v = foo ()
11304 (@value{GDBP}) print $v
11306 (@value{GDBP}) print $_isvoid ($v)
11312 These functions require @value{GDBN} to be configured with
11313 @code{Python} support.
11317 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
11318 @findex $_memeq@r{, convenience function}
11319 Returns one if the @var{length} bytes at the addresses given by
11320 @var{buf1} and @var{buf2} are equal.
11321 Otherwise it returns zero.
11323 @item $_regex(@var{str}, @var{regex})
11324 @findex $_regex@r{, convenience function}
11325 Returns one if the string @var{str} matches the regular expression
11326 @var{regex}. Otherwise it returns zero.
11327 The syntax of the regular expression is that specified by @code{Python}'s
11328 regular expression support.
11330 @item $_streq(@var{str1}, @var{str2})
11331 @findex $_streq@r{, convenience function}
11332 Returns one if the strings @var{str1} and @var{str2} are equal.
11333 Otherwise it returns zero.
11335 @item $_strlen(@var{str})
11336 @findex $_strlen@r{, convenience function}
11337 Returns the length of string @var{str}.
11339 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11340 @findex $_caller_is@r{, convenience function}
11341 Returns one if the calling function's name is equal to @var{name}.
11342 Otherwise it returns zero.
11344 If the optional argument @var{number_of_frames} is provided,
11345 it is the number of frames up in the stack to look.
11353 at testsuite/gdb.python/py-caller-is.c:21
11354 #1 0x00000000004005a0 in middle_func ()
11355 at testsuite/gdb.python/py-caller-is.c:27
11356 #2 0x00000000004005ab in top_func ()
11357 at testsuite/gdb.python/py-caller-is.c:33
11358 #3 0x00000000004005b6 in main ()
11359 at testsuite/gdb.python/py-caller-is.c:39
11360 (gdb) print $_caller_is ("middle_func")
11362 (gdb) print $_caller_is ("top_func", 2)
11366 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11367 @findex $_caller_matches@r{, convenience function}
11368 Returns one if the calling function's name matches the regular expression
11369 @var{regexp}. Otherwise it returns zero.
11371 If the optional argument @var{number_of_frames} is provided,
11372 it is the number of frames up in the stack to look.
11375 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11376 @findex $_any_caller_is@r{, convenience function}
11377 Returns one if any calling function's name is equal to @var{name}.
11378 Otherwise it returns zero.
11380 If the optional argument @var{number_of_frames} is provided,
11381 it is the number of frames up in the stack to look.
11384 This function differs from @code{$_caller_is} in that this function
11385 checks all stack frames from the immediate caller to the frame specified
11386 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
11387 frame specified by @var{number_of_frames}.
11389 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11390 @findex $_any_caller_matches@r{, convenience function}
11391 Returns one if any calling function's name matches the regular expression
11392 @var{regexp}. Otherwise it returns zero.
11394 If the optional argument @var{number_of_frames} is provided,
11395 it is the number of frames up in the stack to look.
11398 This function differs from @code{$_caller_matches} in that this function
11399 checks all stack frames from the immediate caller to the frame specified
11400 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
11401 frame specified by @var{number_of_frames}.
11403 @item $_as_string(@var{value})
11404 @findex $_as_string@r{, convenience function}
11405 Return the string representation of @var{value}.
11407 This function is useful to obtain the textual label (enumerator) of an
11408 enumeration value. For example, assuming the variable @var{node} is of
11409 an enumerated type:
11412 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
11413 Visiting node of type NODE_INTEGER
11416 @item $_cimag(@var{value})
11417 @itemx $_creal(@var{value})
11418 @findex $_cimag@r{, convenience function}
11419 @findex $_creal@r{, convenience function}
11420 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
11421 the complex number @var{value}.
11423 The type of the imaginary or real part depends on the type of the
11424 complex number, e.g., using @code{$_cimag} on a @code{float complex}
11425 will return an imaginary part of type @code{float}.
11429 @value{GDBN} provides the ability to list and get help on
11430 convenience functions.
11433 @item help function
11434 @kindex help function
11435 @cindex show all convenience functions
11436 Print a list of all convenience functions.
11443 You can refer to machine register contents, in expressions, as variables
11444 with names starting with @samp{$}. The names of registers are different
11445 for each machine; use @code{info registers} to see the names used on
11449 @kindex info registers
11450 @item info registers
11451 Print the names and values of all registers except floating-point
11452 and vector registers (in the selected stack frame).
11454 @kindex info all-registers
11455 @cindex floating point registers
11456 @item info all-registers
11457 Print the names and values of all registers, including floating-point
11458 and vector registers (in the selected stack frame).
11460 @item info registers @var{reggroup} @dots{}
11461 Print the name and value of the registers in each of the specified
11462 @var{reggroup}s. The @var{reggoup} can be any of those returned by
11463 @code{maint print reggroups} (@pxref{Maintenance Commands}).
11465 @item info registers @var{regname} @dots{}
11466 Print the @dfn{relativized} value of each specified register @var{regname}.
11467 As discussed in detail below, register values are normally relative to
11468 the selected stack frame. The @var{regname} may be any register name valid on
11469 the machine you are using, with or without the initial @samp{$}.
11472 @anchor{standard registers}
11473 @cindex stack pointer register
11474 @cindex program counter register
11475 @cindex process status register
11476 @cindex frame pointer register
11477 @cindex standard registers
11478 @value{GDBN} has four ``standard'' register names that are available (in
11479 expressions) on most machines---whenever they do not conflict with an
11480 architecture's canonical mnemonics for registers. The register names
11481 @code{$pc} and @code{$sp} are used for the program counter register and
11482 the stack pointer. @code{$fp} is used for a register that contains a
11483 pointer to the current stack frame, and @code{$ps} is used for a
11484 register that contains the processor status. For example,
11485 you could print the program counter in hex with
11492 or print the instruction to be executed next with
11499 or add four to the stack pointer@footnote{This is a way of removing
11500 one word from the stack, on machines where stacks grow downward in
11501 memory (most machines, nowadays). This assumes that the innermost
11502 stack frame is selected; setting @code{$sp} is not allowed when other
11503 stack frames are selected. To pop entire frames off the stack,
11504 regardless of machine architecture, use @code{return};
11505 see @ref{Returning, ,Returning from a Function}.} with
11511 Whenever possible, these four standard register names are available on
11512 your machine even though the machine has different canonical mnemonics,
11513 so long as there is no conflict. The @code{info registers} command
11514 shows the canonical names. For example, on the SPARC, @code{info
11515 registers} displays the processor status register as @code{$psr} but you
11516 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11517 is an alias for the @sc{eflags} register.
11519 @value{GDBN} always considers the contents of an ordinary register as an
11520 integer when the register is examined in this way. Some machines have
11521 special registers which can hold nothing but floating point; these
11522 registers are considered to have floating point values. There is no way
11523 to refer to the contents of an ordinary register as floating point value
11524 (although you can @emph{print} it as a floating point value with
11525 @samp{print/f $@var{regname}}).
11527 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11528 means that the data format in which the register contents are saved by
11529 the operating system is not the same one that your program normally
11530 sees. For example, the registers of the 68881 floating point
11531 coprocessor are always saved in ``extended'' (raw) format, but all C
11532 programs expect to work with ``double'' (virtual) format. In such
11533 cases, @value{GDBN} normally works with the virtual format only (the format
11534 that makes sense for your program), but the @code{info registers} command
11535 prints the data in both formats.
11537 @cindex SSE registers (x86)
11538 @cindex MMX registers (x86)
11539 Some machines have special registers whose contents can be interpreted
11540 in several different ways. For example, modern x86-based machines
11541 have SSE and MMX registers that can hold several values packed
11542 together in several different formats. @value{GDBN} refers to such
11543 registers in @code{struct} notation:
11546 (@value{GDBP}) print $xmm1
11548 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11549 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11550 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11551 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11552 v4_int32 = @{0, 20657912, 11, 13@},
11553 v2_int64 = @{88725056443645952, 55834574859@},
11554 uint128 = 0x0000000d0000000b013b36f800000000
11559 To set values of such registers, you need to tell @value{GDBN} which
11560 view of the register you wish to change, as if you were assigning
11561 value to a @code{struct} member:
11564 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11567 Normally, register values are relative to the selected stack frame
11568 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11569 value that the register would contain if all stack frames farther in
11570 were exited and their saved registers restored. In order to see the
11571 true contents of hardware registers, you must select the innermost
11572 frame (with @samp{frame 0}).
11574 @cindex caller-saved registers
11575 @cindex call-clobbered registers
11576 @cindex volatile registers
11577 @cindex <not saved> values
11578 Usually ABIs reserve some registers as not needed to be saved by the
11579 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11580 registers). It may therefore not be possible for @value{GDBN} to know
11581 the value a register had before the call (in other words, in the outer
11582 frame), if the register value has since been changed by the callee.
11583 @value{GDBN} tries to deduce where the inner frame saved
11584 (``callee-saved'') registers, from the debug info, unwind info, or the
11585 machine code generated by your compiler. If some register is not
11586 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11587 its own knowledge of the ABI, or because the debug/unwind info
11588 explicitly says the register's value is undefined), @value{GDBN}
11589 displays @w{@samp{<not saved>}} as the register's value. With targets
11590 that @value{GDBN} has no knowledge of the register saving convention,
11591 if a register was not saved by the callee, then its value and location
11592 in the outer frame are assumed to be the same of the inner frame.
11593 This is usually harmless, because if the register is call-clobbered,
11594 the caller either does not care what is in the register after the
11595 call, or has code to restore the value that it does care about. Note,
11596 however, that if you change such a register in the outer frame, you
11597 may also be affecting the inner frame. Also, the more ``outer'' the
11598 frame is you're looking at, the more likely a call-clobbered
11599 register's value is to be wrong, in the sense that it doesn't actually
11600 represent the value the register had just before the call.
11602 @node Floating Point Hardware
11603 @section Floating Point Hardware
11604 @cindex floating point
11606 Depending on the configuration, @value{GDBN} may be able to give
11607 you more information about the status of the floating point hardware.
11612 Display hardware-dependent information about the floating
11613 point unit. The exact contents and layout vary depending on the
11614 floating point chip. Currently, @samp{info float} is supported on
11615 the ARM and x86 machines.
11619 @section Vector Unit
11620 @cindex vector unit
11622 Depending on the configuration, @value{GDBN} may be able to give you
11623 more information about the status of the vector unit.
11626 @kindex info vector
11628 Display information about the vector unit. The exact contents and
11629 layout vary depending on the hardware.
11632 @node OS Information
11633 @section Operating System Auxiliary Information
11634 @cindex OS information
11636 @value{GDBN} provides interfaces to useful OS facilities that can help
11637 you debug your program.
11639 @cindex auxiliary vector
11640 @cindex vector, auxiliary
11641 Some operating systems supply an @dfn{auxiliary vector} to programs at
11642 startup. This is akin to the arguments and environment that you
11643 specify for a program, but contains a system-dependent variety of
11644 binary values that tell system libraries important details about the
11645 hardware, operating system, and process. Each value's purpose is
11646 identified by an integer tag; the meanings are well-known but system-specific.
11647 Depending on the configuration and operating system facilities,
11648 @value{GDBN} may be able to show you this information. For remote
11649 targets, this functionality may further depend on the remote stub's
11650 support of the @samp{qXfer:auxv:read} packet, see
11651 @ref{qXfer auxiliary vector read}.
11656 Display the auxiliary vector of the inferior, which can be either a
11657 live process or a core dump file. @value{GDBN} prints each tag value
11658 numerically, and also shows names and text descriptions for recognized
11659 tags. Some values in the vector are numbers, some bit masks, and some
11660 pointers to strings or other data. @value{GDBN} displays each value in the
11661 most appropriate form for a recognized tag, and in hexadecimal for
11662 an unrecognized tag.
11665 On some targets, @value{GDBN} can access operating system-specific
11666 information and show it to you. The types of information available
11667 will differ depending on the type of operating system running on the
11668 target. The mechanism used to fetch the data is described in
11669 @ref{Operating System Information}. For remote targets, this
11670 functionality depends on the remote stub's support of the
11671 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11675 @item info os @var{infotype}
11677 Display OS information of the requested type.
11679 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11681 @anchor{linux info os infotypes}
11683 @kindex info os cpus
11685 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11686 the available fields from /proc/cpuinfo. For each supported architecture
11687 different fields are available. Two common entries are processor which gives
11688 CPU number and bogomips; a system constant that is calculated during
11689 kernel initialization.
11691 @kindex info os files
11693 Display the list of open file descriptors on the target. For each
11694 file descriptor, @value{GDBN} prints the identifier of the process
11695 owning the descriptor, the command of the owning process, the value
11696 of the descriptor, and the target of the descriptor.
11698 @kindex info os modules
11700 Display the list of all loaded kernel modules on the target. For each
11701 module, @value{GDBN} prints the module name, the size of the module in
11702 bytes, the number of times the module is used, the dependencies of the
11703 module, the status of the module, and the address of the loaded module
11706 @kindex info os msg
11708 Display the list of all System V message queues on the target. For each
11709 message queue, @value{GDBN} prints the message queue key, the message
11710 queue identifier, the access permissions, the current number of bytes
11711 on the queue, the current number of messages on the queue, the processes
11712 that last sent and received a message on the queue, the user and group
11713 of the owner and creator of the message queue, the times at which a
11714 message was last sent and received on the queue, and the time at which
11715 the message queue was last changed.
11717 @kindex info os processes
11719 Display the list of processes on the target. For each process,
11720 @value{GDBN} prints the process identifier, the name of the user, the
11721 command corresponding to the process, and the list of processor cores
11722 that the process is currently running on. (To understand what these
11723 properties mean, for this and the following info types, please consult
11724 the general @sc{gnu}/Linux documentation.)
11726 @kindex info os procgroups
11728 Display the list of process groups on the target. For each process,
11729 @value{GDBN} prints the identifier of the process group that it belongs
11730 to, the command corresponding to the process group leader, the process
11731 identifier, and the command line of the process. The list is sorted
11732 first by the process group identifier, then by the process identifier,
11733 so that processes belonging to the same process group are grouped together
11734 and the process group leader is listed first.
11736 @kindex info os semaphores
11738 Display the list of all System V semaphore sets on the target. For each
11739 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11740 set identifier, the access permissions, the number of semaphores in the
11741 set, the user and group of the owner and creator of the semaphore set,
11742 and the times at which the semaphore set was operated upon and changed.
11744 @kindex info os shm
11746 Display the list of all System V shared-memory regions on the target.
11747 For each shared-memory region, @value{GDBN} prints the region key,
11748 the shared-memory identifier, the access permissions, the size of the
11749 region, the process that created the region, the process that last
11750 attached to or detached from the region, the current number of live
11751 attaches to the region, and the times at which the region was last
11752 attached to, detach from, and changed.
11754 @kindex info os sockets
11756 Display the list of Internet-domain sockets on the target. For each
11757 socket, @value{GDBN} prints the address and port of the local and
11758 remote endpoints, the current state of the connection, the creator of
11759 the socket, the IP address family of the socket, and the type of the
11762 @kindex info os threads
11764 Display the list of threads running on the target. For each thread,
11765 @value{GDBN} prints the identifier of the process that the thread
11766 belongs to, the command of the process, the thread identifier, and the
11767 processor core that it is currently running on. The main thread of a
11768 process is not listed.
11772 If @var{infotype} is omitted, then list the possible values for
11773 @var{infotype} and the kind of OS information available for each
11774 @var{infotype}. If the target does not return a list of possible
11775 types, this command will report an error.
11778 @node Memory Region Attributes
11779 @section Memory Region Attributes
11780 @cindex memory region attributes
11782 @dfn{Memory region attributes} allow you to describe special handling
11783 required by regions of your target's memory. @value{GDBN} uses
11784 attributes to determine whether to allow certain types of memory
11785 accesses; whether to use specific width accesses; and whether to cache
11786 target memory. By default the description of memory regions is
11787 fetched from the target (if the current target supports this), but the
11788 user can override the fetched regions.
11790 Defined memory regions can be individually enabled and disabled. When a
11791 memory region is disabled, @value{GDBN} uses the default attributes when
11792 accessing memory in that region. Similarly, if no memory regions have
11793 been defined, @value{GDBN} uses the default attributes when accessing
11796 When a memory region is defined, it is given a number to identify it;
11797 to enable, disable, or remove a memory region, you specify that number.
11801 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11802 Define a memory region bounded by @var{lower} and @var{upper} with
11803 attributes @var{attributes}@dots{}, and add it to the list of regions
11804 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11805 case: it is treated as the target's maximum memory address.
11806 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11809 Discard any user changes to the memory regions and use target-supplied
11810 regions, if available, or no regions if the target does not support.
11813 @item delete mem @var{nums}@dots{}
11814 Remove memory regions @var{nums}@dots{} from the list of regions
11815 monitored by @value{GDBN}.
11817 @kindex disable mem
11818 @item disable mem @var{nums}@dots{}
11819 Disable monitoring of memory regions @var{nums}@dots{}.
11820 A disabled memory region is not forgotten.
11821 It may be enabled again later.
11824 @item enable mem @var{nums}@dots{}
11825 Enable monitoring of memory regions @var{nums}@dots{}.
11829 Print a table of all defined memory regions, with the following columns
11833 @item Memory Region Number
11834 @item Enabled or Disabled.
11835 Enabled memory regions are marked with @samp{y}.
11836 Disabled memory regions are marked with @samp{n}.
11839 The address defining the inclusive lower bound of the memory region.
11842 The address defining the exclusive upper bound of the memory region.
11845 The list of attributes set for this memory region.
11850 @subsection Attributes
11852 @subsubsection Memory Access Mode
11853 The access mode attributes set whether @value{GDBN} may make read or
11854 write accesses to a memory region.
11856 While these attributes prevent @value{GDBN} from performing invalid
11857 memory accesses, they do nothing to prevent the target system, I/O DMA,
11858 etc.@: from accessing memory.
11862 Memory is read only.
11864 Memory is write only.
11866 Memory is read/write. This is the default.
11869 @subsubsection Memory Access Size
11870 The access size attribute tells @value{GDBN} to use specific sized
11871 accesses in the memory region. Often memory mapped device registers
11872 require specific sized accesses. If no access size attribute is
11873 specified, @value{GDBN} may use accesses of any size.
11877 Use 8 bit memory accesses.
11879 Use 16 bit memory accesses.
11881 Use 32 bit memory accesses.
11883 Use 64 bit memory accesses.
11886 @c @subsubsection Hardware/Software Breakpoints
11887 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11888 @c will use hardware or software breakpoints for the internal breakpoints
11889 @c used by the step, next, finish, until, etc. commands.
11893 @c Always use hardware breakpoints
11894 @c @item swbreak (default)
11897 @subsubsection Data Cache
11898 The data cache attributes set whether @value{GDBN} will cache target
11899 memory. While this generally improves performance by reducing debug
11900 protocol overhead, it can lead to incorrect results because @value{GDBN}
11901 does not know about volatile variables or memory mapped device
11906 Enable @value{GDBN} to cache target memory.
11908 Disable @value{GDBN} from caching target memory. This is the default.
11911 @subsection Memory Access Checking
11912 @value{GDBN} can be instructed to refuse accesses to memory that is
11913 not explicitly described. This can be useful if accessing such
11914 regions has undesired effects for a specific target, or to provide
11915 better error checking. The following commands control this behaviour.
11918 @kindex set mem inaccessible-by-default
11919 @item set mem inaccessible-by-default [on|off]
11920 If @code{on} is specified, make @value{GDBN} treat memory not
11921 explicitly described by the memory ranges as non-existent and refuse accesses
11922 to such memory. The checks are only performed if there's at least one
11923 memory range defined. If @code{off} is specified, make @value{GDBN}
11924 treat the memory not explicitly described by the memory ranges as RAM.
11925 The default value is @code{on}.
11926 @kindex show mem inaccessible-by-default
11927 @item show mem inaccessible-by-default
11928 Show the current handling of accesses to unknown memory.
11932 @c @subsubsection Memory Write Verification
11933 @c The memory write verification attributes set whether @value{GDBN}
11934 @c will re-reads data after each write to verify the write was successful.
11938 @c @item noverify (default)
11941 @node Dump/Restore Files
11942 @section Copy Between Memory and a File
11943 @cindex dump/restore files
11944 @cindex append data to a file
11945 @cindex dump data to a file
11946 @cindex restore data from a file
11948 You can use the commands @code{dump}, @code{append}, and
11949 @code{restore} to copy data between target memory and a file. The
11950 @code{dump} and @code{append} commands write data to a file, and the
11951 @code{restore} command reads data from a file back into the inferior's
11952 memory. Files may be in binary, Motorola S-record, Intel hex,
11953 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11954 append to binary files, and cannot read from Verilog Hex files.
11959 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11960 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11961 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11962 or the value of @var{expr}, to @var{filename} in the given format.
11964 The @var{format} parameter may be any one of:
11971 Motorola S-record format.
11973 Tektronix Hex format.
11975 Verilog Hex format.
11978 @value{GDBN} uses the same definitions of these formats as the
11979 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11980 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11984 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11985 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11986 Append the contents of memory from @var{start_addr} to @var{end_addr},
11987 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11988 (@value{GDBN} can only append data to files in raw binary form.)
11991 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11992 Restore the contents of file @var{filename} into memory. The
11993 @code{restore} command can automatically recognize any known @sc{bfd}
11994 file format, except for raw binary. To restore a raw binary file you
11995 must specify the optional keyword @code{binary} after the filename.
11997 If @var{bias} is non-zero, its value will be added to the addresses
11998 contained in the file. Binary files always start at address zero, so
11999 they will be restored at address @var{bias}. Other bfd files have
12000 a built-in location; they will be restored at offset @var{bias}
12001 from that location.
12003 If @var{start} and/or @var{end} are non-zero, then only data between
12004 file offset @var{start} and file offset @var{end} will be restored.
12005 These offsets are relative to the addresses in the file, before
12006 the @var{bias} argument is applied.
12010 @node Core File Generation
12011 @section How to Produce a Core File from Your Program
12012 @cindex dump core from inferior
12014 A @dfn{core file} or @dfn{core dump} is a file that records the memory
12015 image of a running process and its process status (register values
12016 etc.). Its primary use is post-mortem debugging of a program that
12017 crashed while it ran outside a debugger. A program that crashes
12018 automatically produces a core file, unless this feature is disabled by
12019 the user. @xref{Files}, for information on invoking @value{GDBN} in
12020 the post-mortem debugging mode.
12022 Occasionally, you may wish to produce a core file of the program you
12023 are debugging in order to preserve a snapshot of its state.
12024 @value{GDBN} has a special command for that.
12028 @kindex generate-core-file
12029 @item generate-core-file [@var{file}]
12030 @itemx gcore [@var{file}]
12031 Produce a core dump of the inferior process. The optional argument
12032 @var{file} specifies the file name where to put the core dump. If not
12033 specified, the file name defaults to @file{core.@var{pid}}, where
12034 @var{pid} is the inferior process ID.
12036 Note that this command is implemented only for some systems (as of
12037 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
12039 On @sc{gnu}/Linux, this command can take into account the value of the
12040 file @file{/proc/@var{pid}/coredump_filter} when generating the core
12041 dump (@pxref{set use-coredump-filter}), and by default honors the
12042 @code{VM_DONTDUMP} flag for mappings where it is present in the file
12043 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
12045 @kindex set use-coredump-filter
12046 @anchor{set use-coredump-filter}
12047 @item set use-coredump-filter on
12048 @itemx set use-coredump-filter off
12049 Enable or disable the use of the file
12050 @file{/proc/@var{pid}/coredump_filter} when generating core dump
12051 files. This file is used by the Linux kernel to decide what types of
12052 memory mappings will be dumped or ignored when generating a core dump
12053 file. @var{pid} is the process ID of a currently running process.
12055 To make use of this feature, you have to write in the
12056 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
12057 which is a bit mask representing the memory mapping types. If a bit
12058 is set in the bit mask, then the memory mappings of the corresponding
12059 types will be dumped; otherwise, they will be ignored. This
12060 configuration is inherited by child processes. For more information
12061 about the bits that can be set in the
12062 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
12063 manpage of @code{core(5)}.
12065 By default, this option is @code{on}. If this option is turned
12066 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
12067 and instead uses the same default value as the Linux kernel in order
12068 to decide which pages will be dumped in the core dump file. This
12069 value is currently @code{0x33}, which means that bits @code{0}
12070 (anonymous private mappings), @code{1} (anonymous shared mappings),
12071 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
12072 This will cause these memory mappings to be dumped automatically.
12074 @kindex set dump-excluded-mappings
12075 @anchor{set dump-excluded-mappings}
12076 @item set dump-excluded-mappings on
12077 @itemx set dump-excluded-mappings off
12078 If @code{on} is specified, @value{GDBN} will dump memory mappings
12079 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
12080 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
12082 The default value is @code{off}.
12085 @node Character Sets
12086 @section Character Sets
12087 @cindex character sets
12089 @cindex translating between character sets
12090 @cindex host character set
12091 @cindex target character set
12093 If the program you are debugging uses a different character set to
12094 represent characters and strings than the one @value{GDBN} uses itself,
12095 @value{GDBN} can automatically translate between the character sets for
12096 you. The character set @value{GDBN} uses we call the @dfn{host
12097 character set}; the one the inferior program uses we call the
12098 @dfn{target character set}.
12100 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
12101 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
12102 remote protocol (@pxref{Remote Debugging}) to debug a program
12103 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
12104 then the host character set is Latin-1, and the target character set is
12105 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
12106 target-charset EBCDIC-US}, then @value{GDBN} translates between
12107 @sc{ebcdic} and Latin 1 as you print character or string values, or use
12108 character and string literals in expressions.
12110 @value{GDBN} has no way to automatically recognize which character set
12111 the inferior program uses; you must tell it, using the @code{set
12112 target-charset} command, described below.
12114 Here are the commands for controlling @value{GDBN}'s character set
12118 @item set target-charset @var{charset}
12119 @kindex set target-charset
12120 Set the current target character set to @var{charset}. To display the
12121 list of supported target character sets, type
12122 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
12124 @item set host-charset @var{charset}
12125 @kindex set host-charset
12126 Set the current host character set to @var{charset}.
12128 By default, @value{GDBN} uses a host character set appropriate to the
12129 system it is running on; you can override that default using the
12130 @code{set host-charset} command. On some systems, @value{GDBN} cannot
12131 automatically determine the appropriate host character set. In this
12132 case, @value{GDBN} uses @samp{UTF-8}.
12134 @value{GDBN} can only use certain character sets as its host character
12135 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
12136 @value{GDBN} will list the host character sets it supports.
12138 @item set charset @var{charset}
12139 @kindex set charset
12140 Set the current host and target character sets to @var{charset}. As
12141 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
12142 @value{GDBN} will list the names of the character sets that can be used
12143 for both host and target.
12146 @kindex show charset
12147 Show the names of the current host and target character sets.
12149 @item show host-charset
12150 @kindex show host-charset
12151 Show the name of the current host character set.
12153 @item show target-charset
12154 @kindex show target-charset
12155 Show the name of the current target character set.
12157 @item set target-wide-charset @var{charset}
12158 @kindex set target-wide-charset
12159 Set the current target's wide character set to @var{charset}. This is
12160 the character set used by the target's @code{wchar_t} type. To
12161 display the list of supported wide character sets, type
12162 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
12164 @item show target-wide-charset
12165 @kindex show target-wide-charset
12166 Show the name of the current target's wide character set.
12169 Here is an example of @value{GDBN}'s character set support in action.
12170 Assume that the following source code has been placed in the file
12171 @file{charset-test.c}:
12177 = @{72, 101, 108, 108, 111, 44, 32, 119,
12178 111, 114, 108, 100, 33, 10, 0@};
12179 char ibm1047_hello[]
12180 = @{200, 133, 147, 147, 150, 107, 64, 166,
12181 150, 153, 147, 132, 90, 37, 0@};
12185 printf ("Hello, world!\n");
12189 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
12190 containing the string @samp{Hello, world!} followed by a newline,
12191 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
12193 We compile the program, and invoke the debugger on it:
12196 $ gcc -g charset-test.c -o charset-test
12197 $ gdb -nw charset-test
12198 GNU gdb 2001-12-19-cvs
12199 Copyright 2001 Free Software Foundation, Inc.
12204 We can use the @code{show charset} command to see what character sets
12205 @value{GDBN} is currently using to interpret and display characters and
12209 (@value{GDBP}) show charset
12210 The current host and target character set is `ISO-8859-1'.
12214 For the sake of printing this manual, let's use @sc{ascii} as our
12215 initial character set:
12217 (@value{GDBP}) set charset ASCII
12218 (@value{GDBP}) show charset
12219 The current host and target character set is `ASCII'.
12223 Let's assume that @sc{ascii} is indeed the correct character set for our
12224 host system --- in other words, let's assume that if @value{GDBN} prints
12225 characters using the @sc{ascii} character set, our terminal will display
12226 them properly. Since our current target character set is also
12227 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
12230 (@value{GDBP}) print ascii_hello
12231 $1 = 0x401698 "Hello, world!\n"
12232 (@value{GDBP}) print ascii_hello[0]
12237 @value{GDBN} uses the target character set for character and string
12238 literals you use in expressions:
12241 (@value{GDBP}) print '+'
12246 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
12249 @value{GDBN} relies on the user to tell it which character set the
12250 target program uses. If we print @code{ibm1047_hello} while our target
12251 character set is still @sc{ascii}, we get jibberish:
12254 (@value{GDBP}) print ibm1047_hello
12255 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
12256 (@value{GDBP}) print ibm1047_hello[0]
12261 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
12262 @value{GDBN} tells us the character sets it supports:
12265 (@value{GDBP}) set target-charset
12266 ASCII EBCDIC-US IBM1047 ISO-8859-1
12267 (@value{GDBP}) set target-charset
12270 We can select @sc{ibm1047} as our target character set, and examine the
12271 program's strings again. Now the @sc{ascii} string is wrong, but
12272 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
12273 target character set, @sc{ibm1047}, to the host character set,
12274 @sc{ascii}, and they display correctly:
12277 (@value{GDBP}) set target-charset IBM1047
12278 (@value{GDBP}) show charset
12279 The current host character set is `ASCII'.
12280 The current target character set is `IBM1047'.
12281 (@value{GDBP}) print ascii_hello
12282 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
12283 (@value{GDBP}) print ascii_hello[0]
12285 (@value{GDBP}) print ibm1047_hello
12286 $8 = 0x4016a8 "Hello, world!\n"
12287 (@value{GDBP}) print ibm1047_hello[0]
12292 As above, @value{GDBN} uses the target character set for character and
12293 string literals you use in expressions:
12296 (@value{GDBP}) print '+'
12301 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
12304 @node Caching Target Data
12305 @section Caching Data of Targets
12306 @cindex caching data of targets
12308 @value{GDBN} caches data exchanged between the debugger and a target.
12309 Each cache is associated with the address space of the inferior.
12310 @xref{Inferiors and Programs}, about inferior and address space.
12311 Such caching generally improves performance in remote debugging
12312 (@pxref{Remote Debugging}), because it reduces the overhead of the
12313 remote protocol by bundling memory reads and writes into large chunks.
12314 Unfortunately, simply caching everything would lead to incorrect results,
12315 since @value{GDBN} does not necessarily know anything about volatile
12316 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
12317 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
12319 Therefore, by default, @value{GDBN} only caches data
12320 known to be on the stack@footnote{In non-stop mode, it is moderately
12321 rare for a running thread to modify the stack of a stopped thread
12322 in a way that would interfere with a backtrace, and caching of
12323 stack reads provides a significant speed up of remote backtraces.} or
12324 in the code segment.
12325 Other regions of memory can be explicitly marked as
12326 cacheable; @pxref{Memory Region Attributes}.
12329 @kindex set remotecache
12330 @item set remotecache on
12331 @itemx set remotecache off
12332 This option no longer does anything; it exists for compatibility
12335 @kindex show remotecache
12336 @item show remotecache
12337 Show the current state of the obsolete remotecache flag.
12339 @kindex set stack-cache
12340 @item set stack-cache on
12341 @itemx set stack-cache off
12342 Enable or disable caching of stack accesses. When @code{on}, use
12343 caching. By default, this option is @code{on}.
12345 @kindex show stack-cache
12346 @item show stack-cache
12347 Show the current state of data caching for memory accesses.
12349 @kindex set code-cache
12350 @item set code-cache on
12351 @itemx set code-cache off
12352 Enable or disable caching of code segment accesses. When @code{on},
12353 use caching. By default, this option is @code{on}. This improves
12354 performance of disassembly in remote debugging.
12356 @kindex show code-cache
12357 @item show code-cache
12358 Show the current state of target memory cache for code segment
12361 @kindex info dcache
12362 @item info dcache @r{[}line@r{]}
12363 Print the information about the performance of data cache of the
12364 current inferior's address space. The information displayed
12365 includes the dcache width and depth, and for each cache line, its
12366 number, address, and how many times it was referenced. This
12367 command is useful for debugging the data cache operation.
12369 If a line number is specified, the contents of that line will be
12372 @item set dcache size @var{size}
12373 @cindex dcache size
12374 @kindex set dcache size
12375 Set maximum number of entries in dcache (dcache depth above).
12377 @item set dcache line-size @var{line-size}
12378 @cindex dcache line-size
12379 @kindex set dcache line-size
12380 Set number of bytes each dcache entry caches (dcache width above).
12381 Must be a power of 2.
12383 @item show dcache size
12384 @kindex show dcache size
12385 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
12387 @item show dcache line-size
12388 @kindex show dcache line-size
12389 Show default size of dcache lines.
12393 @node Searching Memory
12394 @section Search Memory
12395 @cindex searching memory
12397 Memory can be searched for a particular sequence of bytes with the
12398 @code{find} command.
12402 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12403 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12404 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
12405 etc. The search begins at address @var{start_addr} and continues for either
12406 @var{len} bytes or through to @var{end_addr} inclusive.
12409 @var{s} and @var{n} are optional parameters.
12410 They may be specified in either order, apart or together.
12413 @item @var{s}, search query size
12414 The size of each search query value.
12420 halfwords (two bytes)
12424 giant words (eight bytes)
12427 All values are interpreted in the current language.
12428 This means, for example, that if the current source language is C/C@t{++}
12429 then searching for the string ``hello'' includes the trailing '\0'.
12430 The null terminator can be removed from searching by using casts,
12431 e.g.: @samp{@{char[5]@}"hello"}.
12433 If the value size is not specified, it is taken from the
12434 value's type in the current language.
12435 This is useful when one wants to specify the search
12436 pattern as a mixture of types.
12437 Note that this means, for example, that in the case of C-like languages
12438 a search for an untyped 0x42 will search for @samp{(int) 0x42}
12439 which is typically four bytes.
12441 @item @var{n}, maximum number of finds
12442 The maximum number of matches to print. The default is to print all finds.
12445 You can use strings as search values. Quote them with double-quotes
12447 The string value is copied into the search pattern byte by byte,
12448 regardless of the endianness of the target and the size specification.
12450 The address of each match found is printed as well as a count of the
12451 number of matches found.
12453 The address of the last value found is stored in convenience variable
12455 A count of the number of matches is stored in @samp{$numfound}.
12457 For example, if stopped at the @code{printf} in this function:
12463 static char hello[] = "hello-hello";
12464 static struct @{ char c; short s; int i; @}
12465 __attribute__ ((packed)) mixed
12466 = @{ 'c', 0x1234, 0x87654321 @};
12467 printf ("%s\n", hello);
12472 you get during debugging:
12475 (gdb) find &hello[0], +sizeof(hello), "hello"
12476 0x804956d <hello.1620+6>
12478 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12479 0x8049567 <hello.1620>
12480 0x804956d <hello.1620+6>
12482 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12483 0x8049567 <hello.1620>
12484 0x804956d <hello.1620+6>
12486 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12487 0x8049567 <hello.1620>
12489 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12490 0x8049560 <mixed.1625>
12492 (gdb) print $numfound
12495 $2 = (void *) 0x8049560
12499 @section Value Sizes
12501 Whenever @value{GDBN} prints a value memory will be allocated within
12502 @value{GDBN} to hold the contents of the value. It is possible in
12503 some languages with dynamic typing systems, that an invalid program
12504 may indicate a value that is incorrectly large, this in turn may cause
12505 @value{GDBN} to try and allocate an overly large ammount of memory.
12508 @kindex set max-value-size
12509 @item set max-value-size @var{bytes}
12510 @itemx set max-value-size unlimited
12511 Set the maximum size of memory that @value{GDBN} will allocate for the
12512 contents of a value to @var{bytes}, trying to display a value that
12513 requires more memory than that will result in an error.
12515 Setting this variable does not effect values that have already been
12516 allocated within @value{GDBN}, only future allocations.
12518 There's a minimum size that @code{max-value-size} can be set to in
12519 order that @value{GDBN} can still operate correctly, this minimum is
12520 currently 16 bytes.
12522 The limit applies to the results of some subexpressions as well as to
12523 complete expressions. For example, an expression denoting a simple
12524 integer component, such as @code{x.y.z}, may fail if the size of
12525 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12526 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12527 @var{A} is an array variable with non-constant size, will generally
12528 succeed regardless of the bounds on @var{A}, as long as the component
12529 size is less than @var{bytes}.
12531 The default value of @code{max-value-size} is currently 64k.
12533 @kindex show max-value-size
12534 @item show max-value-size
12535 Show the maximum size of memory, in bytes, that @value{GDBN} will
12536 allocate for the contents of a value.
12539 @node Optimized Code
12540 @chapter Debugging Optimized Code
12541 @cindex optimized code, debugging
12542 @cindex debugging optimized code
12544 Almost all compilers support optimization. With optimization
12545 disabled, the compiler generates assembly code that corresponds
12546 directly to your source code, in a simplistic way. As the compiler
12547 applies more powerful optimizations, the generated assembly code
12548 diverges from your original source code. With help from debugging
12549 information generated by the compiler, @value{GDBN} can map from
12550 the running program back to constructs from your original source.
12552 @value{GDBN} is more accurate with optimization disabled. If you
12553 can recompile without optimization, it is easier to follow the
12554 progress of your program during debugging. But, there are many cases
12555 where you may need to debug an optimized version.
12557 When you debug a program compiled with @samp{-g -O}, remember that the
12558 optimizer has rearranged your code; the debugger shows you what is
12559 really there. Do not be too surprised when the execution path does not
12560 exactly match your source file! An extreme example: if you define a
12561 variable, but never use it, @value{GDBN} never sees that
12562 variable---because the compiler optimizes it out of existence.
12564 Some things do not work as well with @samp{-g -O} as with just
12565 @samp{-g}, particularly on machines with instruction scheduling. If in
12566 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12567 please report it to us as a bug (including a test case!).
12568 @xref{Variables}, for more information about debugging optimized code.
12571 * Inline Functions:: How @value{GDBN} presents inlining
12572 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12575 @node Inline Functions
12576 @section Inline Functions
12577 @cindex inline functions, debugging
12579 @dfn{Inlining} is an optimization that inserts a copy of the function
12580 body directly at each call site, instead of jumping to a shared
12581 routine. @value{GDBN} displays inlined functions just like
12582 non-inlined functions. They appear in backtraces. You can view their
12583 arguments and local variables, step into them with @code{step}, skip
12584 them with @code{next}, and escape from them with @code{finish}.
12585 You can check whether a function was inlined by using the
12586 @code{info frame} command.
12588 For @value{GDBN} to support inlined functions, the compiler must
12589 record information about inlining in the debug information ---
12590 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12591 other compilers do also. @value{GDBN} only supports inlined functions
12592 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12593 do not emit two required attributes (@samp{DW_AT_call_file} and
12594 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12595 function calls with earlier versions of @value{NGCC}. It instead
12596 displays the arguments and local variables of inlined functions as
12597 local variables in the caller.
12599 The body of an inlined function is directly included at its call site;
12600 unlike a non-inlined function, there are no instructions devoted to
12601 the call. @value{GDBN} still pretends that the call site and the
12602 start of the inlined function are different instructions. Stepping to
12603 the call site shows the call site, and then stepping again shows
12604 the first line of the inlined function, even though no additional
12605 instructions are executed.
12607 This makes source-level debugging much clearer; you can see both the
12608 context of the call and then the effect of the call. Only stepping by
12609 a single instruction using @code{stepi} or @code{nexti} does not do
12610 this; single instruction steps always show the inlined body.
12612 There are some ways that @value{GDBN} does not pretend that inlined
12613 function calls are the same as normal calls:
12617 Setting breakpoints at the call site of an inlined function may not
12618 work, because the call site does not contain any code. @value{GDBN}
12619 may incorrectly move the breakpoint to the next line of the enclosing
12620 function, after the call. This limitation will be removed in a future
12621 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12622 or inside the inlined function instead.
12625 @value{GDBN} cannot locate the return value of inlined calls after
12626 using the @code{finish} command. This is a limitation of compiler-generated
12627 debugging information; after @code{finish}, you can step to the next line
12628 and print a variable where your program stored the return value.
12632 @node Tail Call Frames
12633 @section Tail Call Frames
12634 @cindex tail call frames, debugging
12636 Function @code{B} can call function @code{C} in its very last statement. In
12637 unoptimized compilation the call of @code{C} is immediately followed by return
12638 instruction at the end of @code{B} code. Optimizing compiler may replace the
12639 call and return in function @code{B} into one jump to function @code{C}
12640 instead. Such use of a jump instruction is called @dfn{tail call}.
12642 During execution of function @code{C}, there will be no indication in the
12643 function call stack frames that it was tail-called from @code{B}. If function
12644 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12645 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12646 some cases @value{GDBN} can determine that @code{C} was tail-called from
12647 @code{B}, and it will then create fictitious call frame for that, with the
12648 return address set up as if @code{B} called @code{C} normally.
12650 This functionality is currently supported only by DWARF 2 debugging format and
12651 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12652 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12655 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12656 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12660 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12662 Stack level 1, frame at 0x7fffffffda30:
12663 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12664 tail call frame, caller of frame at 0x7fffffffda30
12665 source language c++.
12666 Arglist at unknown address.
12667 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12670 The detection of all the possible code path executions can find them ambiguous.
12671 There is no execution history stored (possible @ref{Reverse Execution} is never
12672 used for this purpose) and the last known caller could have reached the known
12673 callee by multiple different jump sequences. In such case @value{GDBN} still
12674 tries to show at least all the unambiguous top tail callers and all the
12675 unambiguous bottom tail calees, if any.
12678 @anchor{set debug entry-values}
12679 @item set debug entry-values
12680 @kindex set debug entry-values
12681 When set to on, enables printing of analysis messages for both frame argument
12682 values at function entry and tail calls. It will show all the possible valid
12683 tail calls code paths it has considered. It will also print the intersection
12684 of them with the final unambiguous (possibly partial or even empty) code path
12687 @item show debug entry-values
12688 @kindex show debug entry-values
12689 Show the current state of analysis messages printing for both frame argument
12690 values at function entry and tail calls.
12693 The analysis messages for tail calls can for example show why the virtual tail
12694 call frame for function @code{c} has not been recognized (due to the indirect
12695 reference by variable @code{x}):
12698 static void __attribute__((noinline, noclone)) c (void);
12699 void (*x) (void) = c;
12700 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12701 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12702 int main (void) @{ x (); return 0; @}
12704 Breakpoint 1, DW_OP_entry_value resolving cannot find
12705 DW_TAG_call_site 0x40039a in main
12707 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12710 #1 0x000000000040039a in main () at t.c:5
12713 Another possibility is an ambiguous virtual tail call frames resolution:
12717 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12718 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12719 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12720 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12721 static void __attribute__((noinline, noclone)) b (void)
12722 @{ if (i) c (); else e (); @}
12723 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12724 int main (void) @{ a (); return 0; @}
12726 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12727 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12728 tailcall: reduced: 0x4004d2(a) |
12731 #1 0x00000000004004d2 in a () at t.c:8
12732 #2 0x0000000000400395 in main () at t.c:9
12735 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12736 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12738 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12739 @ifset HAVE_MAKEINFO_CLICK
12740 @set ARROW @click{}
12741 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12742 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12744 @ifclear HAVE_MAKEINFO_CLICK
12746 @set CALLSEQ1B @value{CALLSEQ1A}
12747 @set CALLSEQ2B @value{CALLSEQ2A}
12750 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12751 The code can have possible execution paths @value{CALLSEQ1B} or
12752 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12754 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12755 has found. It then finds another possible calling sequcen - that one is
12756 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12757 printed as the @code{reduced:} calling sequence. That one could have many
12758 futher @code{compare:} and @code{reduced:} statements as long as there remain
12759 any non-ambiguous sequence entries.
12761 For the frame of function @code{b} in both cases there are different possible
12762 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12763 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12764 therefore this one is displayed to the user while the ambiguous frames are
12767 There can be also reasons why printing of frame argument values at function
12772 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12773 static void __attribute__((noinline, noclone)) a (int i);
12774 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12775 static void __attribute__((noinline, noclone)) a (int i)
12776 @{ if (i) b (i - 1); else c (0); @}
12777 int main (void) @{ a (5); return 0; @}
12780 #0 c (i=i@@entry=0) at t.c:2
12781 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12782 function "a" at 0x400420 can call itself via tail calls
12783 i=<optimized out>) at t.c:6
12784 #2 0x000000000040036e in main () at t.c:7
12787 @value{GDBN} cannot find out from the inferior state if and how many times did
12788 function @code{a} call itself (via function @code{b}) as these calls would be
12789 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12790 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12791 prints @code{<optimized out>} instead.
12794 @chapter C Preprocessor Macros
12796 Some languages, such as C and C@t{++}, provide a way to define and invoke
12797 ``preprocessor macros'' which expand into strings of tokens.
12798 @value{GDBN} can evaluate expressions containing macro invocations, show
12799 the result of macro expansion, and show a macro's definition, including
12800 where it was defined.
12802 You may need to compile your program specially to provide @value{GDBN}
12803 with information about preprocessor macros. Most compilers do not
12804 include macros in their debugging information, even when you compile
12805 with the @option{-g} flag. @xref{Compilation}.
12807 A program may define a macro at one point, remove that definition later,
12808 and then provide a different definition after that. Thus, at different
12809 points in the program, a macro may have different definitions, or have
12810 no definition at all. If there is a current stack frame, @value{GDBN}
12811 uses the macros in scope at that frame's source code line. Otherwise,
12812 @value{GDBN} uses the macros in scope at the current listing location;
12815 Whenever @value{GDBN} evaluates an expression, it always expands any
12816 macro invocations present in the expression. @value{GDBN} also provides
12817 the following commands for working with macros explicitly.
12821 @kindex macro expand
12822 @cindex macro expansion, showing the results of preprocessor
12823 @cindex preprocessor macro expansion, showing the results of
12824 @cindex expanding preprocessor macros
12825 @item macro expand @var{expression}
12826 @itemx macro exp @var{expression}
12827 Show the results of expanding all preprocessor macro invocations in
12828 @var{expression}. Since @value{GDBN} simply expands macros, but does
12829 not parse the result, @var{expression} need not be a valid expression;
12830 it can be any string of tokens.
12833 @item macro expand-once @var{expression}
12834 @itemx macro exp1 @var{expression}
12835 @cindex expand macro once
12836 @i{(This command is not yet implemented.)} Show the results of
12837 expanding those preprocessor macro invocations that appear explicitly in
12838 @var{expression}. Macro invocations appearing in that expansion are
12839 left unchanged. This command allows you to see the effect of a
12840 particular macro more clearly, without being confused by further
12841 expansions. Since @value{GDBN} simply expands macros, but does not
12842 parse the result, @var{expression} need not be a valid expression; it
12843 can be any string of tokens.
12846 @cindex macro definition, showing
12847 @cindex definition of a macro, showing
12848 @cindex macros, from debug info
12849 @item info macro [-a|-all] [--] @var{macro}
12850 Show the current definition or all definitions of the named @var{macro},
12851 and describe the source location or compiler command-line where that
12852 definition was established. The optional double dash is to signify the end of
12853 argument processing and the beginning of @var{macro} for non C-like macros where
12854 the macro may begin with a hyphen.
12856 @kindex info macros
12857 @item info macros @var{location}
12858 Show all macro definitions that are in effect at the location specified
12859 by @var{location}, and describe the source location or compiler
12860 command-line where those definitions were established.
12862 @kindex macro define
12863 @cindex user-defined macros
12864 @cindex defining macros interactively
12865 @cindex macros, user-defined
12866 @item macro define @var{macro} @var{replacement-list}
12867 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12868 Introduce a definition for a preprocessor macro named @var{macro},
12869 invocations of which are replaced by the tokens given in
12870 @var{replacement-list}. The first form of this command defines an
12871 ``object-like'' macro, which takes no arguments; the second form
12872 defines a ``function-like'' macro, which takes the arguments given in
12875 A definition introduced by this command is in scope in every
12876 expression evaluated in @value{GDBN}, until it is removed with the
12877 @code{macro undef} command, described below. The definition overrides
12878 all definitions for @var{macro} present in the program being debugged,
12879 as well as any previous user-supplied definition.
12881 @kindex macro undef
12882 @item macro undef @var{macro}
12883 Remove any user-supplied definition for the macro named @var{macro}.
12884 This command only affects definitions provided with the @code{macro
12885 define} command, described above; it cannot remove definitions present
12886 in the program being debugged.
12890 List all the macros defined using the @code{macro define} command.
12893 @cindex macros, example of debugging with
12894 Here is a transcript showing the above commands in action. First, we
12895 show our source files:
12900 #include "sample.h"
12903 #define ADD(x) (M + x)
12908 printf ("Hello, world!\n");
12910 printf ("We're so creative.\n");
12912 printf ("Goodbye, world!\n");
12919 Now, we compile the program using the @sc{gnu} C compiler,
12920 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12921 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12922 and @option{-gdwarf-4}; we recommend always choosing the most recent
12923 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12924 includes information about preprocessor macros in the debugging
12928 $ gcc -gdwarf-2 -g3 sample.c -o sample
12932 Now, we start @value{GDBN} on our sample program:
12936 GNU gdb 2002-05-06-cvs
12937 Copyright 2002 Free Software Foundation, Inc.
12938 GDB is free software, @dots{}
12942 We can expand macros and examine their definitions, even when the
12943 program is not running. @value{GDBN} uses the current listing position
12944 to decide which macro definitions are in scope:
12947 (@value{GDBP}) list main
12950 5 #define ADD(x) (M + x)
12955 10 printf ("Hello, world!\n");
12957 12 printf ("We're so creative.\n");
12958 (@value{GDBP}) info macro ADD
12959 Defined at /home/jimb/gdb/macros/play/sample.c:5
12960 #define ADD(x) (M + x)
12961 (@value{GDBP}) info macro Q
12962 Defined at /home/jimb/gdb/macros/play/sample.h:1
12963 included at /home/jimb/gdb/macros/play/sample.c:2
12965 (@value{GDBP}) macro expand ADD(1)
12966 expands to: (42 + 1)
12967 (@value{GDBP}) macro expand-once ADD(1)
12968 expands to: once (M + 1)
12972 In the example above, note that @code{macro expand-once} expands only
12973 the macro invocation explicit in the original text --- the invocation of
12974 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12975 which was introduced by @code{ADD}.
12977 Once the program is running, @value{GDBN} uses the macro definitions in
12978 force at the source line of the current stack frame:
12981 (@value{GDBP}) break main
12982 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12984 Starting program: /home/jimb/gdb/macros/play/sample
12986 Breakpoint 1, main () at sample.c:10
12987 10 printf ("Hello, world!\n");
12991 At line 10, the definition of the macro @code{N} at line 9 is in force:
12994 (@value{GDBP}) info macro N
12995 Defined at /home/jimb/gdb/macros/play/sample.c:9
12997 (@value{GDBP}) macro expand N Q M
12998 expands to: 28 < 42
12999 (@value{GDBP}) print N Q M
13004 As we step over directives that remove @code{N}'s definition, and then
13005 give it a new definition, @value{GDBN} finds the definition (or lack
13006 thereof) in force at each point:
13009 (@value{GDBP}) next
13011 12 printf ("We're so creative.\n");
13012 (@value{GDBP}) info macro N
13013 The symbol `N' has no definition as a C/C++ preprocessor macro
13014 at /home/jimb/gdb/macros/play/sample.c:12
13015 (@value{GDBP}) next
13017 14 printf ("Goodbye, world!\n");
13018 (@value{GDBP}) info macro N
13019 Defined at /home/jimb/gdb/macros/play/sample.c:13
13021 (@value{GDBP}) macro expand N Q M
13022 expands to: 1729 < 42
13023 (@value{GDBP}) print N Q M
13028 In addition to source files, macros can be defined on the compilation command
13029 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
13030 such a way, @value{GDBN} displays the location of their definition as line zero
13031 of the source file submitted to the compiler.
13034 (@value{GDBP}) info macro __STDC__
13035 Defined at /home/jimb/gdb/macros/play/sample.c:0
13042 @chapter Tracepoints
13043 @c This chapter is based on the documentation written by Michael
13044 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
13046 @cindex tracepoints
13047 In some applications, it is not feasible for the debugger to interrupt
13048 the program's execution long enough for the developer to learn
13049 anything helpful about its behavior. If the program's correctness
13050 depends on its real-time behavior, delays introduced by a debugger
13051 might cause the program to change its behavior drastically, or perhaps
13052 fail, even when the code itself is correct. It is useful to be able
13053 to observe the program's behavior without interrupting it.
13055 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
13056 specify locations in the program, called @dfn{tracepoints}, and
13057 arbitrary expressions to evaluate when those tracepoints are reached.
13058 Later, using the @code{tfind} command, you can examine the values
13059 those expressions had when the program hit the tracepoints. The
13060 expressions may also denote objects in memory---structures or arrays,
13061 for example---whose values @value{GDBN} should record; while visiting
13062 a particular tracepoint, you may inspect those objects as if they were
13063 in memory at that moment. However, because @value{GDBN} records these
13064 values without interacting with you, it can do so quickly and
13065 unobtrusively, hopefully not disturbing the program's behavior.
13067 The tracepoint facility is currently available only for remote
13068 targets. @xref{Targets}. In addition, your remote target must know
13069 how to collect trace data. This functionality is implemented in the
13070 remote stub; however, none of the stubs distributed with @value{GDBN}
13071 support tracepoints as of this writing. The format of the remote
13072 packets used to implement tracepoints are described in @ref{Tracepoint
13075 It is also possible to get trace data from a file, in a manner reminiscent
13076 of corefiles; you specify the filename, and use @code{tfind} to search
13077 through the file. @xref{Trace Files}, for more details.
13079 This chapter describes the tracepoint commands and features.
13082 * Set Tracepoints::
13083 * Analyze Collected Data::
13084 * Tracepoint Variables::
13088 @node Set Tracepoints
13089 @section Commands to Set Tracepoints
13091 Before running such a @dfn{trace experiment}, an arbitrary number of
13092 tracepoints can be set. A tracepoint is actually a special type of
13093 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
13094 standard breakpoint commands. For instance, as with breakpoints,
13095 tracepoint numbers are successive integers starting from one, and many
13096 of the commands associated with tracepoints take the tracepoint number
13097 as their argument, to identify which tracepoint to work on.
13099 For each tracepoint, you can specify, in advance, some arbitrary set
13100 of data that you want the target to collect in the trace buffer when
13101 it hits that tracepoint. The collected data can include registers,
13102 local variables, or global data. Later, you can use @value{GDBN}
13103 commands to examine the values these data had at the time the
13104 tracepoint was hit.
13106 Tracepoints do not support every breakpoint feature. Ignore counts on
13107 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
13108 commands when they are hit. Tracepoints may not be thread-specific
13111 @cindex fast tracepoints
13112 Some targets may support @dfn{fast tracepoints}, which are inserted in
13113 a different way (such as with a jump instead of a trap), that is
13114 faster but possibly restricted in where they may be installed.
13116 @cindex static tracepoints
13117 @cindex markers, static tracepoints
13118 @cindex probing markers, static tracepoints
13119 Regular and fast tracepoints are dynamic tracing facilities, meaning
13120 that they can be used to insert tracepoints at (almost) any location
13121 in the target. Some targets may also support controlling @dfn{static
13122 tracepoints} from @value{GDBN}. With static tracing, a set of
13123 instrumentation points, also known as @dfn{markers}, are embedded in
13124 the target program, and can be activated or deactivated by name or
13125 address. These are usually placed at locations which facilitate
13126 investigating what the target is actually doing. @value{GDBN}'s
13127 support for static tracing includes being able to list instrumentation
13128 points, and attach them with @value{GDBN} defined high level
13129 tracepoints that expose the whole range of convenience of
13130 @value{GDBN}'s tracepoints support. Namely, support for collecting
13131 registers values and values of global or local (to the instrumentation
13132 point) variables; tracepoint conditions and trace state variables.
13133 The act of installing a @value{GDBN} static tracepoint on an
13134 instrumentation point, or marker, is referred to as @dfn{probing} a
13135 static tracepoint marker.
13137 @code{gdbserver} supports tracepoints on some target systems.
13138 @xref{Server,,Tracepoints support in @code{gdbserver}}.
13140 This section describes commands to set tracepoints and associated
13141 conditions and actions.
13144 * Create and Delete Tracepoints::
13145 * Enable and Disable Tracepoints::
13146 * Tracepoint Passcounts::
13147 * Tracepoint Conditions::
13148 * Trace State Variables::
13149 * Tracepoint Actions::
13150 * Listing Tracepoints::
13151 * Listing Static Tracepoint Markers::
13152 * Starting and Stopping Trace Experiments::
13153 * Tracepoint Restrictions::
13156 @node Create and Delete Tracepoints
13157 @subsection Create and Delete Tracepoints
13160 @cindex set tracepoint
13162 @item trace @var{location}
13163 The @code{trace} command is very similar to the @code{break} command.
13164 Its argument @var{location} can be any valid location.
13165 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
13166 which is a point in the target program where the debugger will briefly stop,
13167 collect some data, and then allow the program to continue. Setting a tracepoint
13168 or changing its actions takes effect immediately if the remote stub
13169 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
13171 If remote stub doesn't support the @samp{InstallInTrace} feature, all
13172 these changes don't take effect until the next @code{tstart}
13173 command, and once a trace experiment is running, further changes will
13174 not have any effect until the next trace experiment starts. In addition,
13175 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
13176 address is not yet resolved. (This is similar to pending breakpoints.)
13177 Pending tracepoints are not downloaded to the target and not installed
13178 until they are resolved. The resolution of pending tracepoints requires
13179 @value{GDBN} support---when debugging with the remote target, and
13180 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
13181 tracing}), pending tracepoints can not be resolved (and downloaded to
13182 the remote stub) while @value{GDBN} is disconnected.
13184 Here are some examples of using the @code{trace} command:
13187 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
13189 (@value{GDBP}) @b{trace +2} // 2 lines forward
13191 (@value{GDBP}) @b{trace my_function} // first source line of function
13193 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
13195 (@value{GDBP}) @b{trace *0x2117c4} // an address
13199 You can abbreviate @code{trace} as @code{tr}.
13201 @item trace @var{location} if @var{cond}
13202 Set a tracepoint with condition @var{cond}; evaluate the expression
13203 @var{cond} each time the tracepoint is reached, and collect data only
13204 if the value is nonzero---that is, if @var{cond} evaluates as true.
13205 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
13206 information on tracepoint conditions.
13208 @item ftrace @var{location} [ if @var{cond} ]
13209 @cindex set fast tracepoint
13210 @cindex fast tracepoints, setting
13212 The @code{ftrace} command sets a fast tracepoint. For targets that
13213 support them, fast tracepoints will use a more efficient but possibly
13214 less general technique to trigger data collection, such as a jump
13215 instruction instead of a trap, or some sort of hardware support. It
13216 may not be possible to create a fast tracepoint at the desired
13217 location, in which case the command will exit with an explanatory
13220 @value{GDBN} handles arguments to @code{ftrace} exactly as for
13223 On 32-bit x86-architecture systems, fast tracepoints normally need to
13224 be placed at an instruction that is 5 bytes or longer, but can be
13225 placed at 4-byte instructions if the low 64K of memory of the target
13226 program is available to install trampolines. Some Unix-type systems,
13227 such as @sc{gnu}/Linux, exclude low addresses from the program's
13228 address space; but for instance with the Linux kernel it is possible
13229 to let @value{GDBN} use this area by doing a @command{sysctl} command
13230 to set the @code{mmap_min_addr} kernel parameter, as in
13233 sudo sysctl -w vm.mmap_min_addr=32768
13237 which sets the low address to 32K, which leaves plenty of room for
13238 trampolines. The minimum address should be set to a page boundary.
13240 @item strace @var{location} [ if @var{cond} ]
13241 @cindex set static tracepoint
13242 @cindex static tracepoints, setting
13243 @cindex probe static tracepoint marker
13245 The @code{strace} command sets a static tracepoint. For targets that
13246 support it, setting a static tracepoint probes a static
13247 instrumentation point, or marker, found at @var{location}. It may not
13248 be possible to set a static tracepoint at the desired location, in
13249 which case the command will exit with an explanatory message.
13251 @value{GDBN} handles arguments to @code{strace} exactly as for
13252 @code{trace}, with the addition that the user can also specify
13253 @code{-m @var{marker}} as @var{location}. This probes the marker
13254 identified by the @var{marker} string identifier. This identifier
13255 depends on the static tracepoint backend library your program is
13256 using. You can find all the marker identifiers in the @samp{ID} field
13257 of the @code{info static-tracepoint-markers} command output.
13258 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
13259 Markers}. For example, in the following small program using the UST
13265 trace_mark(ust, bar33, "str %s", "FOOBAZ");
13270 the marker id is composed of joining the first two arguments to the
13271 @code{trace_mark} call with a slash, which translates to:
13274 (@value{GDBP}) info static-tracepoint-markers
13275 Cnt Enb ID Address What
13276 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
13282 so you may probe the marker above with:
13285 (@value{GDBP}) strace -m ust/bar33
13288 Static tracepoints accept an extra collect action --- @code{collect
13289 $_sdata}. This collects arbitrary user data passed in the probe point
13290 call to the tracing library. In the UST example above, you'll see
13291 that the third argument to @code{trace_mark} is a printf-like format
13292 string. The user data is then the result of running that formating
13293 string against the following arguments. Note that @code{info
13294 static-tracepoint-markers} command output lists that format string in
13295 the @samp{Data:} field.
13297 You can inspect this data when analyzing the trace buffer, by printing
13298 the $_sdata variable like any other variable available to
13299 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
13302 @cindex last tracepoint number
13303 @cindex recent tracepoint number
13304 @cindex tracepoint number
13305 The convenience variable @code{$tpnum} records the tracepoint number
13306 of the most recently set tracepoint.
13308 @kindex delete tracepoint
13309 @cindex tracepoint deletion
13310 @item delete tracepoint @r{[}@var{num}@r{]}
13311 Permanently delete one or more tracepoints. With no argument, the
13312 default is to delete all tracepoints. Note that the regular
13313 @code{delete} command can remove tracepoints also.
13318 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
13320 (@value{GDBP}) @b{delete trace} // remove all tracepoints
13324 You can abbreviate this command as @code{del tr}.
13327 @node Enable and Disable Tracepoints
13328 @subsection Enable and Disable Tracepoints
13330 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
13333 @kindex disable tracepoint
13334 @item disable tracepoint @r{[}@var{num}@r{]}
13335 Disable tracepoint @var{num}, or all tracepoints if no argument
13336 @var{num} is given. A disabled tracepoint will have no effect during
13337 a trace experiment, but it is not forgotten. You can re-enable
13338 a disabled tracepoint using the @code{enable tracepoint} command.
13339 If the command is issued during a trace experiment and the debug target
13340 has support for disabling tracepoints during a trace experiment, then the
13341 change will be effective immediately. Otherwise, it will be applied to the
13342 next trace experiment.
13344 @kindex enable tracepoint
13345 @item enable tracepoint @r{[}@var{num}@r{]}
13346 Enable tracepoint @var{num}, or all tracepoints. If this command is
13347 issued during a trace experiment and the debug target supports enabling
13348 tracepoints during a trace experiment, then the enabled tracepoints will
13349 become effective immediately. Otherwise, they will become effective the
13350 next time a trace experiment is run.
13353 @node Tracepoint Passcounts
13354 @subsection Tracepoint Passcounts
13358 @cindex tracepoint pass count
13359 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
13360 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
13361 automatically stop a trace experiment. If a tracepoint's passcount is
13362 @var{n}, then the trace experiment will be automatically stopped on
13363 the @var{n}'th time that tracepoint is hit. If the tracepoint number
13364 @var{num} is not specified, the @code{passcount} command sets the
13365 passcount of the most recently defined tracepoint. If no passcount is
13366 given, the trace experiment will run until stopped explicitly by the
13372 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
13373 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
13375 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
13376 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
13377 (@value{GDBP}) @b{trace foo}
13378 (@value{GDBP}) @b{pass 3}
13379 (@value{GDBP}) @b{trace bar}
13380 (@value{GDBP}) @b{pass 2}
13381 (@value{GDBP}) @b{trace baz}
13382 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
13383 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
13384 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
13385 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
13389 @node Tracepoint Conditions
13390 @subsection Tracepoint Conditions
13391 @cindex conditional tracepoints
13392 @cindex tracepoint conditions
13394 The simplest sort of tracepoint collects data every time your program
13395 reaches a specified place. You can also specify a @dfn{condition} for
13396 a tracepoint. A condition is just a Boolean expression in your
13397 programming language (@pxref{Expressions, ,Expressions}). A
13398 tracepoint with a condition evaluates the expression each time your
13399 program reaches it, and data collection happens only if the condition
13402 Tracepoint conditions can be specified when a tracepoint is set, by
13403 using @samp{if} in the arguments to the @code{trace} command.
13404 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
13405 also be set or changed at any time with the @code{condition} command,
13406 just as with breakpoints.
13408 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
13409 the conditional expression itself. Instead, @value{GDBN} encodes the
13410 expression into an agent expression (@pxref{Agent Expressions})
13411 suitable for execution on the target, independently of @value{GDBN}.
13412 Global variables become raw memory locations, locals become stack
13413 accesses, and so forth.
13415 For instance, suppose you have a function that is usually called
13416 frequently, but should not be called after an error has occurred. You
13417 could use the following tracepoint command to collect data about calls
13418 of that function that happen while the error code is propagating
13419 through the program; an unconditional tracepoint could end up
13420 collecting thousands of useless trace frames that you would have to
13424 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
13427 @node Trace State Variables
13428 @subsection Trace State Variables
13429 @cindex trace state variables
13431 A @dfn{trace state variable} is a special type of variable that is
13432 created and managed by target-side code. The syntax is the same as
13433 that for GDB's convenience variables (a string prefixed with ``$''),
13434 but they are stored on the target. They must be created explicitly,
13435 using a @code{tvariable} command. They are always 64-bit signed
13438 Trace state variables are remembered by @value{GDBN}, and downloaded
13439 to the target along with tracepoint information when the trace
13440 experiment starts. There are no intrinsic limits on the number of
13441 trace state variables, beyond memory limitations of the target.
13443 @cindex convenience variables, and trace state variables
13444 Although trace state variables are managed by the target, you can use
13445 them in print commands and expressions as if they were convenience
13446 variables; @value{GDBN} will get the current value from the target
13447 while the trace experiment is running. Trace state variables share
13448 the same namespace as other ``$'' variables, which means that you
13449 cannot have trace state variables with names like @code{$23} or
13450 @code{$pc}, nor can you have a trace state variable and a convenience
13451 variable with the same name.
13455 @item tvariable $@var{name} [ = @var{expression} ]
13457 The @code{tvariable} command creates a new trace state variable named
13458 @code{$@var{name}}, and optionally gives it an initial value of
13459 @var{expression}. The @var{expression} is evaluated when this command is
13460 entered; the result will be converted to an integer if possible,
13461 otherwise @value{GDBN} will report an error. A subsequent
13462 @code{tvariable} command specifying the same name does not create a
13463 variable, but instead assigns the supplied initial value to the
13464 existing variable of that name, overwriting any previous initial
13465 value. The default initial value is 0.
13467 @item info tvariables
13468 @kindex info tvariables
13469 List all the trace state variables along with their initial values.
13470 Their current values may also be displayed, if the trace experiment is
13473 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13474 @kindex delete tvariable
13475 Delete the given trace state variables, or all of them if no arguments
13480 @node Tracepoint Actions
13481 @subsection Tracepoint Action Lists
13485 @cindex tracepoint actions
13486 @item actions @r{[}@var{num}@r{]}
13487 This command will prompt for a list of actions to be taken when the
13488 tracepoint is hit. If the tracepoint number @var{num} is not
13489 specified, this command sets the actions for the one that was most
13490 recently defined (so that you can define a tracepoint and then say
13491 @code{actions} without bothering about its number). You specify the
13492 actions themselves on the following lines, one action at a time, and
13493 terminate the actions list with a line containing just @code{end}. So
13494 far, the only defined actions are @code{collect}, @code{teval}, and
13495 @code{while-stepping}.
13497 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13498 Commands, ,Breakpoint Command Lists}), except that only the defined
13499 actions are allowed; any other @value{GDBN} command is rejected.
13501 @cindex remove actions from a tracepoint
13502 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13503 and follow it immediately with @samp{end}.
13506 (@value{GDBP}) @b{collect @var{data}} // collect some data
13508 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13510 (@value{GDBP}) @b{end} // signals the end of actions.
13513 In the following example, the action list begins with @code{collect}
13514 commands indicating the things to be collected when the tracepoint is
13515 hit. Then, in order to single-step and collect additional data
13516 following the tracepoint, a @code{while-stepping} command is used,
13517 followed by the list of things to be collected after each step in a
13518 sequence of single steps. The @code{while-stepping} command is
13519 terminated by its own separate @code{end} command. Lastly, the action
13520 list is terminated by an @code{end} command.
13523 (@value{GDBP}) @b{trace foo}
13524 (@value{GDBP}) @b{actions}
13525 Enter actions for tracepoint 1, one per line:
13528 > while-stepping 12
13529 > collect $pc, arr[i]
13534 @kindex collect @r{(tracepoints)}
13535 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13536 Collect values of the given expressions when the tracepoint is hit.
13537 This command accepts a comma-separated list of any valid expressions.
13538 In addition to global, static, or local variables, the following
13539 special arguments are supported:
13543 Collect all registers.
13546 Collect all function arguments.
13549 Collect all local variables.
13552 Collect the return address. This is helpful if you want to see more
13555 @emph{Note:} The return address location can not always be reliably
13556 determined up front, and the wrong address / registers may end up
13557 collected instead. On some architectures the reliability is higher
13558 for tracepoints at function entry, while on others it's the opposite.
13559 When this happens, backtracing will stop because the return address is
13560 found unavailable (unless another collect rule happened to match it).
13563 Collects the number of arguments from the static probe at which the
13564 tracepoint is located.
13565 @xref{Static Probe Points}.
13567 @item $_probe_arg@var{n}
13568 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13569 from the static probe at which the tracepoint is located.
13570 @xref{Static Probe Points}.
13573 @vindex $_sdata@r{, collect}
13574 Collect static tracepoint marker specific data. Only available for
13575 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13576 Lists}. On the UST static tracepoints library backend, an
13577 instrumentation point resembles a @code{printf} function call. The
13578 tracing library is able to collect user specified data formatted to a
13579 character string using the format provided by the programmer that
13580 instrumented the program. Other backends have similar mechanisms.
13581 Here's an example of a UST marker call:
13584 const char master_name[] = "$your_name";
13585 trace_mark(channel1, marker1, "hello %s", master_name)
13588 In this case, collecting @code{$_sdata} collects the string
13589 @samp{hello $yourname}. When analyzing the trace buffer, you can
13590 inspect @samp{$_sdata} like any other variable available to
13594 You can give several consecutive @code{collect} commands, each one
13595 with a single argument, or one @code{collect} command with several
13596 arguments separated by commas; the effect is the same.
13598 The optional @var{mods} changes the usual handling of the arguments.
13599 @code{s} requests that pointers to chars be handled as strings, in
13600 particular collecting the contents of the memory being pointed at, up
13601 to the first zero. The upper bound is by default the value of the
13602 @code{print elements} variable; if @code{s} is followed by a decimal
13603 number, that is the upper bound instead. So for instance
13604 @samp{collect/s25 mystr} collects as many as 25 characters at
13607 The command @code{info scope} (@pxref{Symbols, info scope}) is
13608 particularly useful for figuring out what data to collect.
13610 @kindex teval @r{(tracepoints)}
13611 @item teval @var{expr1}, @var{expr2}, @dots{}
13612 Evaluate the given expressions when the tracepoint is hit. This
13613 command accepts a comma-separated list of expressions. The results
13614 are discarded, so this is mainly useful for assigning values to trace
13615 state variables (@pxref{Trace State Variables}) without adding those
13616 values to the trace buffer, as would be the case if the @code{collect}
13619 @kindex while-stepping @r{(tracepoints)}
13620 @item while-stepping @var{n}
13621 Perform @var{n} single-step instruction traces after the tracepoint,
13622 collecting new data after each step. The @code{while-stepping}
13623 command is followed by the list of what to collect while stepping
13624 (followed by its own @code{end} command):
13627 > while-stepping 12
13628 > collect $regs, myglobal
13634 Note that @code{$pc} is not automatically collected by
13635 @code{while-stepping}; you need to explicitly collect that register if
13636 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13639 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13640 @kindex set default-collect
13641 @cindex default collection action
13642 This variable is a list of expressions to collect at each tracepoint
13643 hit. It is effectively an additional @code{collect} action prepended
13644 to every tracepoint action list. The expressions are parsed
13645 individually for each tracepoint, so for instance a variable named
13646 @code{xyz} may be interpreted as a global for one tracepoint, and a
13647 local for another, as appropriate to the tracepoint's location.
13649 @item show default-collect
13650 @kindex show default-collect
13651 Show the list of expressions that are collected by default at each
13656 @node Listing Tracepoints
13657 @subsection Listing Tracepoints
13660 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13661 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13662 @cindex information about tracepoints
13663 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13664 Display information about the tracepoint @var{num}. If you don't
13665 specify a tracepoint number, displays information about all the
13666 tracepoints defined so far. The format is similar to that used for
13667 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13668 command, simply restricting itself to tracepoints.
13670 A tracepoint's listing may include additional information specific to
13675 its passcount as given by the @code{passcount @var{n}} command
13678 the state about installed on target of each location
13682 (@value{GDBP}) @b{info trace}
13683 Num Type Disp Enb Address What
13684 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13686 collect globfoo, $regs
13691 2 tracepoint keep y <MULTIPLE>
13693 2.1 y 0x0804859c in func4 at change-loc.h:35
13694 installed on target
13695 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13696 installed on target
13697 2.3 y <PENDING> set_tracepoint
13698 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13699 not installed on target
13704 This command can be abbreviated @code{info tp}.
13707 @node Listing Static Tracepoint Markers
13708 @subsection Listing Static Tracepoint Markers
13711 @kindex info static-tracepoint-markers
13712 @cindex information about static tracepoint markers
13713 @item info static-tracepoint-markers
13714 Display information about all static tracepoint markers defined in the
13717 For each marker, the following columns are printed:
13721 An incrementing counter, output to help readability. This is not a
13724 The marker ID, as reported by the target.
13725 @item Enabled or Disabled
13726 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13727 that are not enabled.
13729 Where the marker is in your program, as a memory address.
13731 Where the marker is in the source for your program, as a file and line
13732 number. If the debug information included in the program does not
13733 allow @value{GDBN} to locate the source of the marker, this column
13734 will be left blank.
13738 In addition, the following information may be printed for each marker:
13742 User data passed to the tracing library by the marker call. In the
13743 UST backend, this is the format string passed as argument to the
13745 @item Static tracepoints probing the marker
13746 The list of static tracepoints attached to the marker.
13750 (@value{GDBP}) info static-tracepoint-markers
13751 Cnt ID Enb Address What
13752 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13753 Data: number1 %d number2 %d
13754 Probed by static tracepoints: #2
13755 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13761 @node Starting and Stopping Trace Experiments
13762 @subsection Starting and Stopping Trace Experiments
13765 @kindex tstart [ @var{notes} ]
13766 @cindex start a new trace experiment
13767 @cindex collected data discarded
13769 This command starts the trace experiment, and begins collecting data.
13770 It has the side effect of discarding all the data collected in the
13771 trace buffer during the previous trace experiment. If any arguments
13772 are supplied, they are taken as a note and stored with the trace
13773 experiment's state. The notes may be arbitrary text, and are
13774 especially useful with disconnected tracing in a multi-user context;
13775 the notes can explain what the trace is doing, supply user contact
13776 information, and so forth.
13778 @kindex tstop [ @var{notes} ]
13779 @cindex stop a running trace experiment
13781 This command stops the trace experiment. If any arguments are
13782 supplied, they are recorded with the experiment as a note. This is
13783 useful if you are stopping a trace started by someone else, for
13784 instance if the trace is interfering with the system's behavior and
13785 needs to be stopped quickly.
13787 @strong{Note}: a trace experiment and data collection may stop
13788 automatically if any tracepoint's passcount is reached
13789 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13792 @cindex status of trace data collection
13793 @cindex trace experiment, status of
13795 This command displays the status of the current trace data
13799 Here is an example of the commands we described so far:
13802 (@value{GDBP}) @b{trace gdb_c_test}
13803 (@value{GDBP}) @b{actions}
13804 Enter actions for tracepoint #1, one per line.
13805 > collect $regs,$locals,$args
13806 > while-stepping 11
13810 (@value{GDBP}) @b{tstart}
13811 [time passes @dots{}]
13812 (@value{GDBP}) @b{tstop}
13815 @anchor{disconnected tracing}
13816 @cindex disconnected tracing
13817 You can choose to continue running the trace experiment even if
13818 @value{GDBN} disconnects from the target, voluntarily or
13819 involuntarily. For commands such as @code{detach}, the debugger will
13820 ask what you want to do with the trace. But for unexpected
13821 terminations (@value{GDBN} crash, network outage), it would be
13822 unfortunate to lose hard-won trace data, so the variable
13823 @code{disconnected-tracing} lets you decide whether the trace should
13824 continue running without @value{GDBN}.
13827 @item set disconnected-tracing on
13828 @itemx set disconnected-tracing off
13829 @kindex set disconnected-tracing
13830 Choose whether a tracing run should continue to run if @value{GDBN}
13831 has disconnected from the target. Note that @code{detach} or
13832 @code{quit} will ask you directly what to do about a running trace no
13833 matter what this variable's setting, so the variable is mainly useful
13834 for handling unexpected situations, such as loss of the network.
13836 @item show disconnected-tracing
13837 @kindex show disconnected-tracing
13838 Show the current choice for disconnected tracing.
13842 When you reconnect to the target, the trace experiment may or may not
13843 still be running; it might have filled the trace buffer in the
13844 meantime, or stopped for one of the other reasons. If it is running,
13845 it will continue after reconnection.
13847 Upon reconnection, the target will upload information about the
13848 tracepoints in effect. @value{GDBN} will then compare that
13849 information to the set of tracepoints currently defined, and attempt
13850 to match them up, allowing for the possibility that the numbers may
13851 have changed due to creation and deletion in the meantime. If one of
13852 the target's tracepoints does not match any in @value{GDBN}, the
13853 debugger will create a new tracepoint, so that you have a number with
13854 which to specify that tracepoint. This matching-up process is
13855 necessarily heuristic, and it may result in useless tracepoints being
13856 created; you may simply delete them if they are of no use.
13858 @cindex circular trace buffer
13859 If your target agent supports a @dfn{circular trace buffer}, then you
13860 can run a trace experiment indefinitely without filling the trace
13861 buffer; when space runs out, the agent deletes already-collected trace
13862 frames, oldest first, until there is enough room to continue
13863 collecting. This is especially useful if your tracepoints are being
13864 hit too often, and your trace gets terminated prematurely because the
13865 buffer is full. To ask for a circular trace buffer, simply set
13866 @samp{circular-trace-buffer} to on. You can set this at any time,
13867 including during tracing; if the agent can do it, it will change
13868 buffer handling on the fly, otherwise it will not take effect until
13872 @item set circular-trace-buffer on
13873 @itemx set circular-trace-buffer off
13874 @kindex set circular-trace-buffer
13875 Choose whether a tracing run should use a linear or circular buffer
13876 for trace data. A linear buffer will not lose any trace data, but may
13877 fill up prematurely, while a circular buffer will discard old trace
13878 data, but it will have always room for the latest tracepoint hits.
13880 @item show circular-trace-buffer
13881 @kindex show circular-trace-buffer
13882 Show the current choice for the trace buffer. Note that this may not
13883 match the agent's current buffer handling, nor is it guaranteed to
13884 match the setting that might have been in effect during a past run,
13885 for instance if you are looking at frames from a trace file.
13890 @item set trace-buffer-size @var{n}
13891 @itemx set trace-buffer-size unlimited
13892 @kindex set trace-buffer-size
13893 Request that the target use a trace buffer of @var{n} bytes. Not all
13894 targets will honor the request; they may have a compiled-in size for
13895 the trace buffer, or some other limitation. Set to a value of
13896 @code{unlimited} or @code{-1} to let the target use whatever size it
13897 likes. This is also the default.
13899 @item show trace-buffer-size
13900 @kindex show trace-buffer-size
13901 Show the current requested size for the trace buffer. Note that this
13902 will only match the actual size if the target supports size-setting,
13903 and was able to handle the requested size. For instance, if the
13904 target can only change buffer size between runs, this variable will
13905 not reflect the change until the next run starts. Use @code{tstatus}
13906 to get a report of the actual buffer size.
13910 @item set trace-user @var{text}
13911 @kindex set trace-user
13913 @item show trace-user
13914 @kindex show trace-user
13916 @item set trace-notes @var{text}
13917 @kindex set trace-notes
13918 Set the trace run's notes.
13920 @item show trace-notes
13921 @kindex show trace-notes
13922 Show the trace run's notes.
13924 @item set trace-stop-notes @var{text}
13925 @kindex set trace-stop-notes
13926 Set the trace run's stop notes. The handling of the note is as for
13927 @code{tstop} arguments; the set command is convenient way to fix a
13928 stop note that is mistaken or incomplete.
13930 @item show trace-stop-notes
13931 @kindex show trace-stop-notes
13932 Show the trace run's stop notes.
13936 @node Tracepoint Restrictions
13937 @subsection Tracepoint Restrictions
13939 @cindex tracepoint restrictions
13940 There are a number of restrictions on the use of tracepoints. As
13941 described above, tracepoint data gathering occurs on the target
13942 without interaction from @value{GDBN}. Thus the full capabilities of
13943 the debugger are not available during data gathering, and then at data
13944 examination time, you will be limited by only having what was
13945 collected. The following items describe some common problems, but it
13946 is not exhaustive, and you may run into additional difficulties not
13952 Tracepoint expressions are intended to gather objects (lvalues). Thus
13953 the full flexibility of GDB's expression evaluator is not available.
13954 You cannot call functions, cast objects to aggregate types, access
13955 convenience variables or modify values (except by assignment to trace
13956 state variables). Some language features may implicitly call
13957 functions (for instance Objective-C fields with accessors), and therefore
13958 cannot be collected either.
13961 Collection of local variables, either individually or in bulk with
13962 @code{$locals} or @code{$args}, during @code{while-stepping} may
13963 behave erratically. The stepping action may enter a new scope (for
13964 instance by stepping into a function), or the location of the variable
13965 may change (for instance it is loaded into a register). The
13966 tracepoint data recorded uses the location information for the
13967 variables that is correct for the tracepoint location. When the
13968 tracepoint is created, it is not possible, in general, to determine
13969 where the steps of a @code{while-stepping} sequence will advance the
13970 program---particularly if a conditional branch is stepped.
13973 Collection of an incompletely-initialized or partially-destroyed object
13974 may result in something that @value{GDBN} cannot display, or displays
13975 in a misleading way.
13978 When @value{GDBN} displays a pointer to character it automatically
13979 dereferences the pointer to also display characters of the string
13980 being pointed to. However, collecting the pointer during tracing does
13981 not automatically collect the string. You need to explicitly
13982 dereference the pointer and provide size information if you want to
13983 collect not only the pointer, but the memory pointed to. For example,
13984 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13988 It is not possible to collect a complete stack backtrace at a
13989 tracepoint. Instead, you may collect the registers and a few hundred
13990 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13991 (adjust to use the name of the actual stack pointer register on your
13992 target architecture, and the amount of stack you wish to capture).
13993 Then the @code{backtrace} command will show a partial backtrace when
13994 using a trace frame. The number of stack frames that can be examined
13995 depends on the sizes of the frames in the collected stack. Note that
13996 if you ask for a block so large that it goes past the bottom of the
13997 stack, the target agent may report an error trying to read from an
14001 If you do not collect registers at a tracepoint, @value{GDBN} can
14002 infer that the value of @code{$pc} must be the same as the address of
14003 the tracepoint and use that when you are looking at a trace frame
14004 for that tracepoint. However, this cannot work if the tracepoint has
14005 multiple locations (for instance if it was set in a function that was
14006 inlined), or if it has a @code{while-stepping} loop. In those cases
14007 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
14012 @node Analyze Collected Data
14013 @section Using the Collected Data
14015 After the tracepoint experiment ends, you use @value{GDBN} commands
14016 for examining the trace data. The basic idea is that each tracepoint
14017 collects a trace @dfn{snapshot} every time it is hit and another
14018 snapshot every time it single-steps. All these snapshots are
14019 consecutively numbered from zero and go into a buffer, and you can
14020 examine them later. The way you examine them is to @dfn{focus} on a
14021 specific trace snapshot. When the remote stub is focused on a trace
14022 snapshot, it will respond to all @value{GDBN} requests for memory and
14023 registers by reading from the buffer which belongs to that snapshot,
14024 rather than from @emph{real} memory or registers of the program being
14025 debugged. This means that @strong{all} @value{GDBN} commands
14026 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
14027 behave as if we were currently debugging the program state as it was
14028 when the tracepoint occurred. Any requests for data that are not in
14029 the buffer will fail.
14032 * tfind:: How to select a trace snapshot
14033 * tdump:: How to display all data for a snapshot
14034 * save tracepoints:: How to save tracepoints for a future run
14038 @subsection @code{tfind @var{n}}
14041 @cindex select trace snapshot
14042 @cindex find trace snapshot
14043 The basic command for selecting a trace snapshot from the buffer is
14044 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
14045 counting from zero. If no argument @var{n} is given, the next
14046 snapshot is selected.
14048 Here are the various forms of using the @code{tfind} command.
14052 Find the first snapshot in the buffer. This is a synonym for
14053 @code{tfind 0} (since 0 is the number of the first snapshot).
14056 Stop debugging trace snapshots, resume @emph{live} debugging.
14059 Same as @samp{tfind none}.
14062 No argument means find the next trace snapshot or find the first
14063 one if no trace snapshot is selected.
14066 Find the previous trace snapshot before the current one. This permits
14067 retracing earlier steps.
14069 @item tfind tracepoint @var{num}
14070 Find the next snapshot associated with tracepoint @var{num}. Search
14071 proceeds forward from the last examined trace snapshot. If no
14072 argument @var{num} is given, it means find the next snapshot collected
14073 for the same tracepoint as the current snapshot.
14075 @item tfind pc @var{addr}
14076 Find the next snapshot associated with the value @var{addr} of the
14077 program counter. Search proceeds forward from the last examined trace
14078 snapshot. If no argument @var{addr} is given, it means find the next
14079 snapshot with the same value of PC as the current snapshot.
14081 @item tfind outside @var{addr1}, @var{addr2}
14082 Find the next snapshot whose PC is outside the given range of
14083 addresses (exclusive).
14085 @item tfind range @var{addr1}, @var{addr2}
14086 Find the next snapshot whose PC is between @var{addr1} and
14087 @var{addr2} (inclusive).
14089 @item tfind line @r{[}@var{file}:@r{]}@var{n}
14090 Find the next snapshot associated with the source line @var{n}. If
14091 the optional argument @var{file} is given, refer to line @var{n} in
14092 that source file. Search proceeds forward from the last examined
14093 trace snapshot. If no argument @var{n} is given, it means find the
14094 next line other than the one currently being examined; thus saying
14095 @code{tfind line} repeatedly can appear to have the same effect as
14096 stepping from line to line in a @emph{live} debugging session.
14099 The default arguments for the @code{tfind} commands are specifically
14100 designed to make it easy to scan through the trace buffer. For
14101 instance, @code{tfind} with no argument selects the next trace
14102 snapshot, and @code{tfind -} with no argument selects the previous
14103 trace snapshot. So, by giving one @code{tfind} command, and then
14104 simply hitting @key{RET} repeatedly you can examine all the trace
14105 snapshots in order. Or, by saying @code{tfind -} and then hitting
14106 @key{RET} repeatedly you can examine the snapshots in reverse order.
14107 The @code{tfind line} command with no argument selects the snapshot
14108 for the next source line executed. The @code{tfind pc} command with
14109 no argument selects the next snapshot with the same program counter
14110 (PC) as the current frame. The @code{tfind tracepoint} command with
14111 no argument selects the next trace snapshot collected by the same
14112 tracepoint as the current one.
14114 In addition to letting you scan through the trace buffer manually,
14115 these commands make it easy to construct @value{GDBN} scripts that
14116 scan through the trace buffer and print out whatever collected data
14117 you are interested in. Thus, if we want to examine the PC, FP, and SP
14118 registers from each trace frame in the buffer, we can say this:
14121 (@value{GDBP}) @b{tfind start}
14122 (@value{GDBP}) @b{while ($trace_frame != -1)}
14123 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
14124 $trace_frame, $pc, $sp, $fp
14128 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
14129 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
14130 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
14131 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
14132 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
14133 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
14134 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
14135 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
14136 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
14137 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
14138 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
14141 Or, if we want to examine the variable @code{X} at each source line in
14145 (@value{GDBP}) @b{tfind start}
14146 (@value{GDBP}) @b{while ($trace_frame != -1)}
14147 > printf "Frame %d, X == %d\n", $trace_frame, X
14157 @subsection @code{tdump}
14159 @cindex dump all data collected at tracepoint
14160 @cindex tracepoint data, display
14162 This command takes no arguments. It prints all the data collected at
14163 the current trace snapshot.
14166 (@value{GDBP}) @b{trace 444}
14167 (@value{GDBP}) @b{actions}
14168 Enter actions for tracepoint #2, one per line:
14169 > collect $regs, $locals, $args, gdb_long_test
14172 (@value{GDBP}) @b{tstart}
14174 (@value{GDBP}) @b{tfind line 444}
14175 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
14177 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
14179 (@value{GDBP}) @b{tdump}
14180 Data collected at tracepoint 2, trace frame 1:
14181 d0 0xc4aa0085 -995491707
14185 d4 0x71aea3d 119204413
14188 d7 0x380035 3670069
14189 a0 0x19e24a 1696330
14190 a1 0x3000668 50333288
14192 a3 0x322000 3284992
14193 a4 0x3000698 50333336
14194 a5 0x1ad3cc 1758156
14195 fp 0x30bf3c 0x30bf3c
14196 sp 0x30bf34 0x30bf34
14198 pc 0x20b2c8 0x20b2c8
14202 p = 0x20e5b4 "gdb-test"
14209 gdb_long_test = 17 '\021'
14214 @code{tdump} works by scanning the tracepoint's current collection
14215 actions and printing the value of each expression listed. So
14216 @code{tdump} can fail, if after a run, you change the tracepoint's
14217 actions to mention variables that were not collected during the run.
14219 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
14220 uses the collected value of @code{$pc} to distinguish between trace
14221 frames that were collected at the tracepoint hit, and frames that were
14222 collected while stepping. This allows it to correctly choose whether
14223 to display the basic list of collections, or the collections from the
14224 body of the while-stepping loop. However, if @code{$pc} was not collected,
14225 then @code{tdump} will always attempt to dump using the basic collection
14226 list, and may fail if a while-stepping frame does not include all the
14227 same data that is collected at the tracepoint hit.
14228 @c This is getting pretty arcane, example would be good.
14230 @node save tracepoints
14231 @subsection @code{save tracepoints @var{filename}}
14232 @kindex save tracepoints
14233 @kindex save-tracepoints
14234 @cindex save tracepoints for future sessions
14236 This command saves all current tracepoint definitions together with
14237 their actions and passcounts, into a file @file{@var{filename}}
14238 suitable for use in a later debugging session. To read the saved
14239 tracepoint definitions, use the @code{source} command (@pxref{Command
14240 Files}). The @w{@code{save-tracepoints}} command is a deprecated
14241 alias for @w{@code{save tracepoints}}
14243 @node Tracepoint Variables
14244 @section Convenience Variables for Tracepoints
14245 @cindex tracepoint variables
14246 @cindex convenience variables for tracepoints
14249 @vindex $trace_frame
14250 @item (int) $trace_frame
14251 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
14252 snapshot is selected.
14254 @vindex $tracepoint
14255 @item (int) $tracepoint
14256 The tracepoint for the current trace snapshot.
14258 @vindex $trace_line
14259 @item (int) $trace_line
14260 The line number for the current trace snapshot.
14262 @vindex $trace_file
14263 @item (char []) $trace_file
14264 The source file for the current trace snapshot.
14266 @vindex $trace_func
14267 @item (char []) $trace_func
14268 The name of the function containing @code{$tracepoint}.
14271 Note: @code{$trace_file} is not suitable for use in @code{printf},
14272 use @code{output} instead.
14274 Here's a simple example of using these convenience variables for
14275 stepping through all the trace snapshots and printing some of their
14276 data. Note that these are not the same as trace state variables,
14277 which are managed by the target.
14280 (@value{GDBP}) @b{tfind start}
14282 (@value{GDBP}) @b{while $trace_frame != -1}
14283 > output $trace_file
14284 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
14290 @section Using Trace Files
14291 @cindex trace files
14293 In some situations, the target running a trace experiment may no
14294 longer be available; perhaps it crashed, or the hardware was needed
14295 for a different activity. To handle these cases, you can arrange to
14296 dump the trace data into a file, and later use that file as a source
14297 of trace data, via the @code{target tfile} command.
14302 @item tsave [ -r ] @var{filename}
14303 @itemx tsave [-ctf] @var{dirname}
14304 Save the trace data to @var{filename}. By default, this command
14305 assumes that @var{filename} refers to the host filesystem, so if
14306 necessary @value{GDBN} will copy raw trace data up from the target and
14307 then save it. If the target supports it, you can also supply the
14308 optional argument @code{-r} (``remote'') to direct the target to save
14309 the data directly into @var{filename} in its own filesystem, which may be
14310 more efficient if the trace buffer is very large. (Note, however, that
14311 @code{target tfile} can only read from files accessible to the host.)
14312 By default, this command will save trace frame in tfile format.
14313 You can supply the optional argument @code{-ctf} to save data in CTF
14314 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
14315 that can be shared by multiple debugging and tracing tools. Please go to
14316 @indicateurl{http://www.efficios.com/ctf} to get more information.
14318 @kindex target tfile
14322 @item target tfile @var{filename}
14323 @itemx target ctf @var{dirname}
14324 Use the file named @var{filename} or directory named @var{dirname} as
14325 a source of trace data. Commands that examine data work as they do with
14326 a live target, but it is not possible to run any new trace experiments.
14327 @code{tstatus} will report the state of the trace run at the moment
14328 the data was saved, as well as the current trace frame you are examining.
14329 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
14333 (@value{GDBP}) target ctf ctf.ctf
14334 (@value{GDBP}) tfind
14335 Found trace frame 0, tracepoint 2
14336 39 ++a; /* set tracepoint 1 here */
14337 (@value{GDBP}) tdump
14338 Data collected at tracepoint 2, trace frame 0:
14342 c = @{"123", "456", "789", "123", "456", "789"@}
14343 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
14351 @chapter Debugging Programs That Use Overlays
14354 If your program is too large to fit completely in your target system's
14355 memory, you can sometimes use @dfn{overlays} to work around this
14356 problem. @value{GDBN} provides some support for debugging programs that
14360 * How Overlays Work:: A general explanation of overlays.
14361 * Overlay Commands:: Managing overlays in @value{GDBN}.
14362 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
14363 mapped by asking the inferior.
14364 * Overlay Sample Program:: A sample program using overlays.
14367 @node How Overlays Work
14368 @section How Overlays Work
14369 @cindex mapped overlays
14370 @cindex unmapped overlays
14371 @cindex load address, overlay's
14372 @cindex mapped address
14373 @cindex overlay area
14375 Suppose you have a computer whose instruction address space is only 64
14376 kilobytes long, but which has much more memory which can be accessed by
14377 other means: special instructions, segment registers, or memory
14378 management hardware, for example. Suppose further that you want to
14379 adapt a program which is larger than 64 kilobytes to run on this system.
14381 One solution is to identify modules of your program which are relatively
14382 independent, and need not call each other directly; call these modules
14383 @dfn{overlays}. Separate the overlays from the main program, and place
14384 their machine code in the larger memory. Place your main program in
14385 instruction memory, but leave at least enough space there to hold the
14386 largest overlay as well.
14388 Now, to call a function located in an overlay, you must first copy that
14389 overlay's machine code from the large memory into the space set aside
14390 for it in the instruction memory, and then jump to its entry point
14393 @c NB: In the below the mapped area's size is greater or equal to the
14394 @c size of all overlays. This is intentional to remind the developer
14395 @c that overlays don't necessarily need to be the same size.
14399 Data Instruction Larger
14400 Address Space Address Space Address Space
14401 +-----------+ +-----------+ +-----------+
14403 +-----------+ +-----------+ +-----------+<-- overlay 1
14404 | program | | main | .----| overlay 1 | load address
14405 | variables | | program | | +-----------+
14406 | and heap | | | | | |
14407 +-----------+ | | | +-----------+<-- overlay 2
14408 | | +-----------+ | | | load address
14409 +-----------+ | | | .-| overlay 2 |
14411 mapped --->+-----------+ | | +-----------+
14412 address | | | | | |
14413 | overlay | <-' | | |
14414 | area | <---' +-----------+<-- overlay 3
14415 | | <---. | | load address
14416 +-----------+ `--| overlay 3 |
14423 @anchor{A code overlay}A code overlay
14427 The diagram (@pxref{A code overlay}) shows a system with separate data
14428 and instruction address spaces. To map an overlay, the program copies
14429 its code from the larger address space to the instruction address space.
14430 Since the overlays shown here all use the same mapped address, only one
14431 may be mapped at a time. For a system with a single address space for
14432 data and instructions, the diagram would be similar, except that the
14433 program variables and heap would share an address space with the main
14434 program and the overlay area.
14436 An overlay loaded into instruction memory and ready for use is called a
14437 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
14438 instruction memory. An overlay not present (or only partially present)
14439 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
14440 is its address in the larger memory. The mapped address is also called
14441 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
14442 called the @dfn{load memory address}, or @dfn{LMA}.
14444 Unfortunately, overlays are not a completely transparent way to adapt a
14445 program to limited instruction memory. They introduce a new set of
14446 global constraints you must keep in mind as you design your program:
14451 Before calling or returning to a function in an overlay, your program
14452 must make sure that overlay is actually mapped. Otherwise, the call or
14453 return will transfer control to the right address, but in the wrong
14454 overlay, and your program will probably crash.
14457 If the process of mapping an overlay is expensive on your system, you
14458 will need to choose your overlays carefully to minimize their effect on
14459 your program's performance.
14462 The executable file you load onto your system must contain each
14463 overlay's instructions, appearing at the overlay's load address, not its
14464 mapped address. However, each overlay's instructions must be relocated
14465 and its symbols defined as if the overlay were at its mapped address.
14466 You can use GNU linker scripts to specify different load and relocation
14467 addresses for pieces of your program; see @ref{Overlay Description,,,
14468 ld.info, Using ld: the GNU linker}.
14471 The procedure for loading executable files onto your system must be able
14472 to load their contents into the larger address space as well as the
14473 instruction and data spaces.
14477 The overlay system described above is rather simple, and could be
14478 improved in many ways:
14483 If your system has suitable bank switch registers or memory management
14484 hardware, you could use those facilities to make an overlay's load area
14485 contents simply appear at their mapped address in instruction space.
14486 This would probably be faster than copying the overlay to its mapped
14487 area in the usual way.
14490 If your overlays are small enough, you could set aside more than one
14491 overlay area, and have more than one overlay mapped at a time.
14494 You can use overlays to manage data, as well as instructions. In
14495 general, data overlays are even less transparent to your design than
14496 code overlays: whereas code overlays only require care when you call or
14497 return to functions, data overlays require care every time you access
14498 the data. Also, if you change the contents of a data overlay, you
14499 must copy its contents back out to its load address before you can copy a
14500 different data overlay into the same mapped area.
14505 @node Overlay Commands
14506 @section Overlay Commands
14508 To use @value{GDBN}'s overlay support, each overlay in your program must
14509 correspond to a separate section of the executable file. The section's
14510 virtual memory address and load memory address must be the overlay's
14511 mapped and load addresses. Identifying overlays with sections allows
14512 @value{GDBN} to determine the appropriate address of a function or
14513 variable, depending on whether the overlay is mapped or not.
14515 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14516 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14521 Disable @value{GDBN}'s overlay support. When overlay support is
14522 disabled, @value{GDBN} assumes that all functions and variables are
14523 always present at their mapped addresses. By default, @value{GDBN}'s
14524 overlay support is disabled.
14526 @item overlay manual
14527 @cindex manual overlay debugging
14528 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14529 relies on you to tell it which overlays are mapped, and which are not,
14530 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14531 commands described below.
14533 @item overlay map-overlay @var{overlay}
14534 @itemx overlay map @var{overlay}
14535 @cindex map an overlay
14536 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14537 be the name of the object file section containing the overlay. When an
14538 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14539 functions and variables at their mapped addresses. @value{GDBN} assumes
14540 that any other overlays whose mapped ranges overlap that of
14541 @var{overlay} are now unmapped.
14543 @item overlay unmap-overlay @var{overlay}
14544 @itemx overlay unmap @var{overlay}
14545 @cindex unmap an overlay
14546 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14547 must be the name of the object file section containing the overlay.
14548 When an overlay is unmapped, @value{GDBN} assumes it can find the
14549 overlay's functions and variables at their load addresses.
14552 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14553 consults a data structure the overlay manager maintains in the inferior
14554 to see which overlays are mapped. For details, see @ref{Automatic
14555 Overlay Debugging}.
14557 @item overlay load-target
14558 @itemx overlay load
14559 @cindex reloading the overlay table
14560 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14561 re-reads the table @value{GDBN} automatically each time the inferior
14562 stops, so this command should only be necessary if you have changed the
14563 overlay mapping yourself using @value{GDBN}. This command is only
14564 useful when using automatic overlay debugging.
14566 @item overlay list-overlays
14567 @itemx overlay list
14568 @cindex listing mapped overlays
14569 Display a list of the overlays currently mapped, along with their mapped
14570 addresses, load addresses, and sizes.
14574 Normally, when @value{GDBN} prints a code address, it includes the name
14575 of the function the address falls in:
14578 (@value{GDBP}) print main
14579 $3 = @{int ()@} 0x11a0 <main>
14582 When overlay debugging is enabled, @value{GDBN} recognizes code in
14583 unmapped overlays, and prints the names of unmapped functions with
14584 asterisks around them. For example, if @code{foo} is a function in an
14585 unmapped overlay, @value{GDBN} prints it this way:
14588 (@value{GDBP}) overlay list
14589 No sections are mapped.
14590 (@value{GDBP}) print foo
14591 $5 = @{int (int)@} 0x100000 <*foo*>
14594 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14598 (@value{GDBP}) overlay list
14599 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14600 mapped at 0x1016 - 0x104a
14601 (@value{GDBP}) print foo
14602 $6 = @{int (int)@} 0x1016 <foo>
14605 When overlay debugging is enabled, @value{GDBN} can find the correct
14606 address for functions and variables in an overlay, whether or not the
14607 overlay is mapped. This allows most @value{GDBN} commands, like
14608 @code{break} and @code{disassemble}, to work normally, even on unmapped
14609 code. However, @value{GDBN}'s breakpoint support has some limitations:
14613 @cindex breakpoints in overlays
14614 @cindex overlays, setting breakpoints in
14615 You can set breakpoints in functions in unmapped overlays, as long as
14616 @value{GDBN} can write to the overlay at its load address.
14618 @value{GDBN} can not set hardware or simulator-based breakpoints in
14619 unmapped overlays. However, if you set a breakpoint at the end of your
14620 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14621 you are using manual overlay management), @value{GDBN} will re-set its
14622 breakpoints properly.
14626 @node Automatic Overlay Debugging
14627 @section Automatic Overlay Debugging
14628 @cindex automatic overlay debugging
14630 @value{GDBN} can automatically track which overlays are mapped and which
14631 are not, given some simple co-operation from the overlay manager in the
14632 inferior. If you enable automatic overlay debugging with the
14633 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14634 looks in the inferior's memory for certain variables describing the
14635 current state of the overlays.
14637 Here are the variables your overlay manager must define to support
14638 @value{GDBN}'s automatic overlay debugging:
14642 @item @code{_ovly_table}:
14643 This variable must be an array of the following structures:
14648 /* The overlay's mapped address. */
14651 /* The size of the overlay, in bytes. */
14652 unsigned long size;
14654 /* The overlay's load address. */
14657 /* Non-zero if the overlay is currently mapped;
14659 unsigned long mapped;
14663 @item @code{_novlys}:
14664 This variable must be a four-byte signed integer, holding the total
14665 number of elements in @code{_ovly_table}.
14669 To decide whether a particular overlay is mapped or not, @value{GDBN}
14670 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14671 @code{lma} members equal the VMA and LMA of the overlay's section in the
14672 executable file. When @value{GDBN} finds a matching entry, it consults
14673 the entry's @code{mapped} member to determine whether the overlay is
14676 In addition, your overlay manager may define a function called
14677 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14678 will silently set a breakpoint there. If the overlay manager then
14679 calls this function whenever it has changed the overlay table, this
14680 will enable @value{GDBN} to accurately keep track of which overlays
14681 are in program memory, and update any breakpoints that may be set
14682 in overlays. This will allow breakpoints to work even if the
14683 overlays are kept in ROM or other non-writable memory while they
14684 are not being executed.
14686 @node Overlay Sample Program
14687 @section Overlay Sample Program
14688 @cindex overlay example program
14690 When linking a program which uses overlays, you must place the overlays
14691 at their load addresses, while relocating them to run at their mapped
14692 addresses. To do this, you must write a linker script (@pxref{Overlay
14693 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14694 since linker scripts are specific to a particular host system, target
14695 architecture, and target memory layout, this manual cannot provide
14696 portable sample code demonstrating @value{GDBN}'s overlay support.
14698 However, the @value{GDBN} source distribution does contain an overlaid
14699 program, with linker scripts for a few systems, as part of its test
14700 suite. The program consists of the following files from
14701 @file{gdb/testsuite/gdb.base}:
14705 The main program file.
14707 A simple overlay manager, used by @file{overlays.c}.
14712 Overlay modules, loaded and used by @file{overlays.c}.
14715 Linker scripts for linking the test program on the @code{d10v-elf}
14716 and @code{m32r-elf} targets.
14719 You can build the test program using the @code{d10v-elf} GCC
14720 cross-compiler like this:
14723 $ d10v-elf-gcc -g -c overlays.c
14724 $ d10v-elf-gcc -g -c ovlymgr.c
14725 $ d10v-elf-gcc -g -c foo.c
14726 $ d10v-elf-gcc -g -c bar.c
14727 $ d10v-elf-gcc -g -c baz.c
14728 $ d10v-elf-gcc -g -c grbx.c
14729 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14730 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14733 The build process is identical for any other architecture, except that
14734 you must substitute the appropriate compiler and linker script for the
14735 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14739 @chapter Using @value{GDBN} with Different Languages
14742 Although programming languages generally have common aspects, they are
14743 rarely expressed in the same manner. For instance, in ANSI C,
14744 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14745 Modula-2, it is accomplished by @code{p^}. Values can also be
14746 represented (and displayed) differently. Hex numbers in C appear as
14747 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14749 @cindex working language
14750 Language-specific information is built into @value{GDBN} for some languages,
14751 allowing you to express operations like the above in your program's
14752 native language, and allowing @value{GDBN} to output values in a manner
14753 consistent with the syntax of your program's native language. The
14754 language you use to build expressions is called the @dfn{working
14758 * Setting:: Switching between source languages
14759 * Show:: Displaying the language
14760 * Checks:: Type and range checks
14761 * Supported Languages:: Supported languages
14762 * Unsupported Languages:: Unsupported languages
14766 @section Switching Between Source Languages
14768 There are two ways to control the working language---either have @value{GDBN}
14769 set it automatically, or select it manually yourself. You can use the
14770 @code{set language} command for either purpose. On startup, @value{GDBN}
14771 defaults to setting the language automatically. The working language is
14772 used to determine how expressions you type are interpreted, how values
14775 In addition to the working language, every source file that
14776 @value{GDBN} knows about has its own working language. For some object
14777 file formats, the compiler might indicate which language a particular
14778 source file is in. However, most of the time @value{GDBN} infers the
14779 language from the name of the file. The language of a source file
14780 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14781 show each frame appropriately for its own language. There is no way to
14782 set the language of a source file from within @value{GDBN}, but you can
14783 set the language associated with a filename extension. @xref{Show, ,
14784 Displaying the Language}.
14786 This is most commonly a problem when you use a program, such
14787 as @code{cfront} or @code{f2c}, that generates C but is written in
14788 another language. In that case, make the
14789 program use @code{#line} directives in its C output; that way
14790 @value{GDBN} will know the correct language of the source code of the original
14791 program, and will display that source code, not the generated C code.
14794 * Filenames:: Filename extensions and languages.
14795 * Manually:: Setting the working language manually
14796 * Automatically:: Having @value{GDBN} infer the source language
14800 @subsection List of Filename Extensions and Languages
14802 If a source file name ends in one of the following extensions, then
14803 @value{GDBN} infers that its language is the one indicated.
14821 C@t{++} source file
14827 Objective-C source file
14831 Fortran source file
14834 Modula-2 source file
14838 Assembler source file. This actually behaves almost like C, but
14839 @value{GDBN} does not skip over function prologues when stepping.
14842 In addition, you may set the language associated with a filename
14843 extension. @xref{Show, , Displaying the Language}.
14846 @subsection Setting the Working Language
14848 If you allow @value{GDBN} to set the language automatically,
14849 expressions are interpreted the same way in your debugging session and
14852 @kindex set language
14853 If you wish, you may set the language manually. To do this, issue the
14854 command @samp{set language @var{lang}}, where @var{lang} is the name of
14855 a language, such as
14856 @code{c} or @code{modula-2}.
14857 For a list of the supported languages, type @samp{set language}.
14859 Setting the language manually prevents @value{GDBN} from updating the working
14860 language automatically. This can lead to confusion if you try
14861 to debug a program when the working language is not the same as the
14862 source language, when an expression is acceptable to both
14863 languages---but means different things. For instance, if the current
14864 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14872 might not have the effect you intended. In C, this means to add
14873 @code{b} and @code{c} and place the result in @code{a}. The result
14874 printed would be the value of @code{a}. In Modula-2, this means to compare
14875 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14877 @node Automatically
14878 @subsection Having @value{GDBN} Infer the Source Language
14880 To have @value{GDBN} set the working language automatically, use
14881 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14882 then infers the working language. That is, when your program stops in a
14883 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14884 working language to the language recorded for the function in that
14885 frame. If the language for a frame is unknown (that is, if the function
14886 or block corresponding to the frame was defined in a source file that
14887 does not have a recognized extension), the current working language is
14888 not changed, and @value{GDBN} issues a warning.
14890 This may not seem necessary for most programs, which are written
14891 entirely in one source language. However, program modules and libraries
14892 written in one source language can be used by a main program written in
14893 a different source language. Using @samp{set language auto} in this
14894 case frees you from having to set the working language manually.
14897 @section Displaying the Language
14899 The following commands help you find out which language is the
14900 working language, and also what language source files were written in.
14903 @item show language
14904 @anchor{show language}
14905 @kindex show language
14906 Display the current working language. This is the
14907 language you can use with commands such as @code{print} to
14908 build and compute expressions that may involve variables in your program.
14911 @kindex info frame@r{, show the source language}
14912 Display the source language for this frame. This language becomes the
14913 working language if you use an identifier from this frame.
14914 @xref{Frame Info, ,Information about a Frame}, to identify the other
14915 information listed here.
14918 @kindex info source@r{, show the source language}
14919 Display the source language of this source file.
14920 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14921 information listed here.
14924 In unusual circumstances, you may have source files with extensions
14925 not in the standard list. You can then set the extension associated
14926 with a language explicitly:
14929 @item set extension-language @var{ext} @var{language}
14930 @kindex set extension-language
14931 Tell @value{GDBN} that source files with extension @var{ext} are to be
14932 assumed as written in the source language @var{language}.
14934 @item info extensions
14935 @kindex info extensions
14936 List all the filename extensions and the associated languages.
14940 @section Type and Range Checking
14942 Some languages are designed to guard you against making seemingly common
14943 errors through a series of compile- and run-time checks. These include
14944 checking the type of arguments to functions and operators and making
14945 sure mathematical overflows are caught at run time. Checks such as
14946 these help to ensure a program's correctness once it has been compiled
14947 by eliminating type mismatches and providing active checks for range
14948 errors when your program is running.
14950 By default @value{GDBN} checks for these errors according to the
14951 rules of the current source language. Although @value{GDBN} does not check
14952 the statements in your program, it can check expressions entered directly
14953 into @value{GDBN} for evaluation via the @code{print} command, for example.
14956 * Type Checking:: An overview of type checking
14957 * Range Checking:: An overview of range checking
14960 @cindex type checking
14961 @cindex checks, type
14962 @node Type Checking
14963 @subsection An Overview of Type Checking
14965 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14966 arguments to operators and functions have to be of the correct type,
14967 otherwise an error occurs. These checks prevent type mismatch
14968 errors from ever causing any run-time problems. For example,
14971 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14973 (@value{GDBP}) print obj.my_method (0)
14976 (@value{GDBP}) print obj.my_method (0x1234)
14977 Cannot resolve method klass::my_method to any overloaded instance
14980 The second example fails because in C@t{++} the integer constant
14981 @samp{0x1234} is not type-compatible with the pointer parameter type.
14983 For the expressions you use in @value{GDBN} commands, you can tell
14984 @value{GDBN} to not enforce strict type checking or
14985 to treat any mismatches as errors and abandon the expression;
14986 When type checking is disabled, @value{GDBN} successfully evaluates
14987 expressions like the second example above.
14989 Even if type checking is off, there may be other reasons
14990 related to type that prevent @value{GDBN} from evaluating an expression.
14991 For instance, @value{GDBN} does not know how to add an @code{int} and
14992 a @code{struct foo}. These particular type errors have nothing to do
14993 with the language in use and usually arise from expressions which make
14994 little sense to evaluate anyway.
14996 @value{GDBN} provides some additional commands for controlling type checking:
14998 @kindex set check type
14999 @kindex show check type
15001 @item set check type on
15002 @itemx set check type off
15003 Set strict type checking on or off. If any type mismatches occur in
15004 evaluating an expression while type checking is on, @value{GDBN} prints a
15005 message and aborts evaluation of the expression.
15007 @item show check type
15008 Show the current setting of type checking and whether @value{GDBN}
15009 is enforcing strict type checking rules.
15012 @cindex range checking
15013 @cindex checks, range
15014 @node Range Checking
15015 @subsection An Overview of Range Checking
15017 In some languages (such as Modula-2), it is an error to exceed the
15018 bounds of a type; this is enforced with run-time checks. Such range
15019 checking is meant to ensure program correctness by making sure
15020 computations do not overflow, or indices on an array element access do
15021 not exceed the bounds of the array.
15023 For expressions you use in @value{GDBN} commands, you can tell
15024 @value{GDBN} to treat range errors in one of three ways: ignore them,
15025 always treat them as errors and abandon the expression, or issue
15026 warnings but evaluate the expression anyway.
15028 A range error can result from numerical overflow, from exceeding an
15029 array index bound, or when you type a constant that is not a member
15030 of any type. Some languages, however, do not treat overflows as an
15031 error. In many implementations of C, mathematical overflow causes the
15032 result to ``wrap around'' to lower values---for example, if @var{m} is
15033 the largest integer value, and @var{s} is the smallest, then
15036 @var{m} + 1 @result{} @var{s}
15039 This, too, is specific to individual languages, and in some cases
15040 specific to individual compilers or machines. @xref{Supported Languages, ,
15041 Supported Languages}, for further details on specific languages.
15043 @value{GDBN} provides some additional commands for controlling the range checker:
15045 @kindex set check range
15046 @kindex show check range
15048 @item set check range auto
15049 Set range checking on or off based on the current working language.
15050 @xref{Supported Languages, ,Supported Languages}, for the default settings for
15053 @item set check range on
15054 @itemx set check range off
15055 Set range checking on or off, overriding the default setting for the
15056 current working language. A warning is issued if the setting does not
15057 match the language default. If a range error occurs and range checking is on,
15058 then a message is printed and evaluation of the expression is aborted.
15060 @item set check range warn
15061 Output messages when the @value{GDBN} range checker detects a range error,
15062 but attempt to evaluate the expression anyway. Evaluating the
15063 expression may still be impossible for other reasons, such as accessing
15064 memory that the process does not own (a typical example from many Unix
15068 Show the current setting of the range checker, and whether or not it is
15069 being set automatically by @value{GDBN}.
15072 @node Supported Languages
15073 @section Supported Languages
15075 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
15076 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
15077 @c This is false ...
15078 Some @value{GDBN} features may be used in expressions regardless of the
15079 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
15080 and the @samp{@{type@}addr} construct (@pxref{Expressions,
15081 ,Expressions}) can be used with the constructs of any supported
15084 The following sections detail to what degree each source language is
15085 supported by @value{GDBN}. These sections are not meant to be language
15086 tutorials or references, but serve only as a reference guide to what the
15087 @value{GDBN} expression parser accepts, and what input and output
15088 formats should look like for different languages. There are many good
15089 books written on each of these languages; please look to these for a
15090 language reference or tutorial.
15093 * C:: C and C@t{++}
15096 * Objective-C:: Objective-C
15097 * OpenCL C:: OpenCL C
15098 * Fortran:: Fortran
15101 * Modula-2:: Modula-2
15106 @subsection C and C@t{++}
15108 @cindex C and C@t{++}
15109 @cindex expressions in C or C@t{++}
15111 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
15112 to both languages. Whenever this is the case, we discuss those languages
15116 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
15117 @cindex @sc{gnu} C@t{++}
15118 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
15119 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
15120 effectively, you must compile your C@t{++} programs with a supported
15121 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
15122 compiler (@code{aCC}).
15125 * C Operators:: C and C@t{++} operators
15126 * C Constants:: C and C@t{++} constants
15127 * C Plus Plus Expressions:: C@t{++} expressions
15128 * C Defaults:: Default settings for C and C@t{++}
15129 * C Checks:: C and C@t{++} type and range checks
15130 * Debugging C:: @value{GDBN} and C
15131 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
15132 * Decimal Floating Point:: Numbers in Decimal Floating Point format
15136 @subsubsection C and C@t{++} Operators
15138 @cindex C and C@t{++} operators
15140 Operators must be defined on values of specific types. For instance,
15141 @code{+} is defined on numbers, but not on structures. Operators are
15142 often defined on groups of types.
15144 For the purposes of C and C@t{++}, the following definitions hold:
15149 @emph{Integral types} include @code{int} with any of its storage-class
15150 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
15153 @emph{Floating-point types} include @code{float}, @code{double}, and
15154 @code{long double} (if supported by the target platform).
15157 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
15160 @emph{Scalar types} include all of the above.
15165 The following operators are supported. They are listed here
15166 in order of increasing precedence:
15170 The comma or sequencing operator. Expressions in a comma-separated list
15171 are evaluated from left to right, with the result of the entire
15172 expression being the last expression evaluated.
15175 Assignment. The value of an assignment expression is the value
15176 assigned. Defined on scalar types.
15179 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
15180 and translated to @w{@code{@var{a} = @var{a op b}}}.
15181 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
15182 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
15183 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
15186 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
15187 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
15188 should be of an integral type.
15191 Logical @sc{or}. Defined on integral types.
15194 Logical @sc{and}. Defined on integral types.
15197 Bitwise @sc{or}. Defined on integral types.
15200 Bitwise exclusive-@sc{or}. Defined on integral types.
15203 Bitwise @sc{and}. Defined on integral types.
15206 Equality and inequality. Defined on scalar types. The value of these
15207 expressions is 0 for false and non-zero for true.
15209 @item <@r{, }>@r{, }<=@r{, }>=
15210 Less than, greater than, less than or equal, greater than or equal.
15211 Defined on scalar types. The value of these expressions is 0 for false
15212 and non-zero for true.
15215 left shift, and right shift. Defined on integral types.
15218 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15221 Addition and subtraction. Defined on integral types, floating-point types and
15224 @item *@r{, }/@r{, }%
15225 Multiplication, division, and modulus. Multiplication and division are
15226 defined on integral and floating-point types. Modulus is defined on
15230 Increment and decrement. When appearing before a variable, the
15231 operation is performed before the variable is used in an expression;
15232 when appearing after it, the variable's value is used before the
15233 operation takes place.
15236 Pointer dereferencing. Defined on pointer types. Same precedence as
15240 Address operator. Defined on variables. Same precedence as @code{++}.
15242 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
15243 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
15244 to examine the address
15245 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
15249 Negative. Defined on integral and floating-point types. Same
15250 precedence as @code{++}.
15253 Logical negation. Defined on integral types. Same precedence as
15257 Bitwise complement operator. Defined on integral types. Same precedence as
15262 Structure member, and pointer-to-structure member. For convenience,
15263 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
15264 pointer based on the stored type information.
15265 Defined on @code{struct} and @code{union} data.
15268 Dereferences of pointers to members.
15271 Array indexing. @code{@var{a}[@var{i}]} is defined as
15272 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
15275 Function parameter list. Same precedence as @code{->}.
15278 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
15279 and @code{class} types.
15282 Doubled colons also represent the @value{GDBN} scope operator
15283 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
15287 If an operator is redefined in the user code, @value{GDBN} usually
15288 attempts to invoke the redefined version instead of using the operator's
15289 predefined meaning.
15292 @subsubsection C and C@t{++} Constants
15294 @cindex C and C@t{++} constants
15296 @value{GDBN} allows you to express the constants of C and C@t{++} in the
15301 Integer constants are a sequence of digits. Octal constants are
15302 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
15303 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
15304 @samp{l}, specifying that the constant should be treated as a
15308 Floating point constants are a sequence of digits, followed by a decimal
15309 point, followed by a sequence of digits, and optionally followed by an
15310 exponent. An exponent is of the form:
15311 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
15312 sequence of digits. The @samp{+} is optional for positive exponents.
15313 A floating-point constant may also end with a letter @samp{f} or
15314 @samp{F}, specifying that the constant should be treated as being of
15315 the @code{float} (as opposed to the default @code{double}) type; or with
15316 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
15320 Enumerated constants consist of enumerated identifiers, or their
15321 integral equivalents.
15324 Character constants are a single character surrounded by single quotes
15325 (@code{'}), or a number---the ordinal value of the corresponding character
15326 (usually its @sc{ascii} value). Within quotes, the single character may
15327 be represented by a letter or by @dfn{escape sequences}, which are of
15328 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
15329 of the character's ordinal value; or of the form @samp{\@var{x}}, where
15330 @samp{@var{x}} is a predefined special character---for example,
15331 @samp{\n} for newline.
15333 Wide character constants can be written by prefixing a character
15334 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
15335 form of @samp{x}. The target wide character set is used when
15336 computing the value of this constant (@pxref{Character Sets}).
15339 String constants are a sequence of character constants surrounded by
15340 double quotes (@code{"}). Any valid character constant (as described
15341 above) may appear. Double quotes within the string must be preceded by
15342 a backslash, so for instance @samp{"a\"b'c"} is a string of five
15345 Wide string constants can be written by prefixing a string constant
15346 with @samp{L}, as in C. The target wide character set is used when
15347 computing the value of this constant (@pxref{Character Sets}).
15350 Pointer constants are an integral value. You can also write pointers
15351 to constants using the C operator @samp{&}.
15354 Array constants are comma-separated lists surrounded by braces @samp{@{}
15355 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
15356 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
15357 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
15360 @node C Plus Plus Expressions
15361 @subsubsection C@t{++} Expressions
15363 @cindex expressions in C@t{++}
15364 @value{GDBN} expression handling can interpret most C@t{++} expressions.
15366 @cindex debugging C@t{++} programs
15367 @cindex C@t{++} compilers
15368 @cindex debug formats and C@t{++}
15369 @cindex @value{NGCC} and C@t{++}
15371 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
15372 the proper compiler and the proper debug format. Currently,
15373 @value{GDBN} works best when debugging C@t{++} code that is compiled
15374 with the most recent version of @value{NGCC} possible. The DWARF
15375 debugging format is preferred; @value{NGCC} defaults to this on most
15376 popular platforms. Other compilers and/or debug formats are likely to
15377 work badly or not at all when using @value{GDBN} to debug C@t{++}
15378 code. @xref{Compilation}.
15383 @cindex member functions
15385 Member function calls are allowed; you can use expressions like
15388 count = aml->GetOriginal(x, y)
15391 @vindex this@r{, inside C@t{++} member functions}
15392 @cindex namespace in C@t{++}
15394 While a member function is active (in the selected stack frame), your
15395 expressions have the same namespace available as the member function;
15396 that is, @value{GDBN} allows implicit references to the class instance
15397 pointer @code{this} following the same rules as C@t{++}. @code{using}
15398 declarations in the current scope are also respected by @value{GDBN}.
15400 @cindex call overloaded functions
15401 @cindex overloaded functions, calling
15402 @cindex type conversions in C@t{++}
15404 You can call overloaded functions; @value{GDBN} resolves the function
15405 call to the right definition, with some restrictions. @value{GDBN} does not
15406 perform overload resolution involving user-defined type conversions,
15407 calls to constructors, or instantiations of templates that do not exist
15408 in the program. It also cannot handle ellipsis argument lists or
15411 It does perform integral conversions and promotions, floating-point
15412 promotions, arithmetic conversions, pointer conversions, conversions of
15413 class objects to base classes, and standard conversions such as those of
15414 functions or arrays to pointers; it requires an exact match on the
15415 number of function arguments.
15417 Overload resolution is always performed, unless you have specified
15418 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
15419 ,@value{GDBN} Features for C@t{++}}.
15421 You must specify @code{set overload-resolution off} in order to use an
15422 explicit function signature to call an overloaded function, as in
15424 p 'foo(char,int)'('x', 13)
15427 The @value{GDBN} command-completion facility can simplify this;
15428 see @ref{Completion, ,Command Completion}.
15430 @cindex reference declarations
15432 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
15433 references; you can use them in expressions just as you do in C@t{++}
15434 source---they are automatically dereferenced.
15436 In the parameter list shown when @value{GDBN} displays a frame, the values of
15437 reference variables are not displayed (unlike other variables); this
15438 avoids clutter, since references are often used for large structures.
15439 The @emph{address} of a reference variable is always shown, unless
15440 you have specified @samp{set print address off}.
15443 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
15444 expressions can use it just as expressions in your program do. Since
15445 one scope may be defined in another, you can use @code{::} repeatedly if
15446 necessary, for example in an expression like
15447 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
15448 resolving name scope by reference to source files, in both C and C@t{++}
15449 debugging (@pxref{Variables, ,Program Variables}).
15452 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15457 @subsubsection C and C@t{++} Defaults
15459 @cindex C and C@t{++} defaults
15461 If you allow @value{GDBN} to set range checking automatically, it
15462 defaults to @code{off} whenever the working language changes to
15463 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15464 selects the working language.
15466 If you allow @value{GDBN} to set the language automatically, it
15467 recognizes source files whose names end with @file{.c}, @file{.C}, or
15468 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15469 these files, it sets the working language to C or C@t{++}.
15470 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15471 for further details.
15474 @subsubsection C and C@t{++} Type and Range Checks
15476 @cindex C and C@t{++} checks
15478 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15479 checking is used. However, if you turn type checking off, @value{GDBN}
15480 will allow certain non-standard conversions, such as promoting integer
15481 constants to pointers.
15483 Range checking, if turned on, is done on mathematical operations. Array
15484 indices are not checked, since they are often used to index a pointer
15485 that is not itself an array.
15488 @subsubsection @value{GDBN} and C
15490 The @code{set print union} and @code{show print union} commands apply to
15491 the @code{union} type. When set to @samp{on}, any @code{union} that is
15492 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15493 appears as @samp{@{...@}}.
15495 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15496 with pointers and a memory allocation function. @xref{Expressions,
15499 @node Debugging C Plus Plus
15500 @subsubsection @value{GDBN} Features for C@t{++}
15502 @cindex commands for C@t{++}
15504 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15505 designed specifically for use with C@t{++}. Here is a summary:
15508 @cindex break in overloaded functions
15509 @item @r{breakpoint menus}
15510 When you want a breakpoint in a function whose name is overloaded,
15511 @value{GDBN} has the capability to display a menu of possible breakpoint
15512 locations to help you specify which function definition you want.
15513 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15515 @cindex overloading in C@t{++}
15516 @item rbreak @var{regex}
15517 Setting breakpoints using regular expressions is helpful for setting
15518 breakpoints on overloaded functions that are not members of any special
15520 @xref{Set Breaks, ,Setting Breakpoints}.
15522 @cindex C@t{++} exception handling
15524 @itemx catch rethrow
15526 Debug C@t{++} exception handling using these commands. @xref{Set
15527 Catchpoints, , Setting Catchpoints}.
15529 @cindex inheritance
15530 @item ptype @var{typename}
15531 Print inheritance relationships as well as other information for type
15533 @xref{Symbols, ,Examining the Symbol Table}.
15535 @item info vtbl @var{expression}.
15536 The @code{info vtbl} command can be used to display the virtual
15537 method tables of the object computed by @var{expression}. This shows
15538 one entry per virtual table; there may be multiple virtual tables when
15539 multiple inheritance is in use.
15541 @cindex C@t{++} demangling
15542 @item demangle @var{name}
15543 Demangle @var{name}.
15544 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15546 @cindex C@t{++} symbol display
15547 @item set print demangle
15548 @itemx show print demangle
15549 @itemx set print asm-demangle
15550 @itemx show print asm-demangle
15551 Control whether C@t{++} symbols display in their source form, both when
15552 displaying code as C@t{++} source and when displaying disassemblies.
15553 @xref{Print Settings, ,Print Settings}.
15555 @item set print object
15556 @itemx show print object
15557 Choose whether to print derived (actual) or declared types of objects.
15558 @xref{Print Settings, ,Print Settings}.
15560 @item set print vtbl
15561 @itemx show print vtbl
15562 Control the format for printing virtual function tables.
15563 @xref{Print Settings, ,Print Settings}.
15564 (The @code{vtbl} commands do not work on programs compiled with the HP
15565 ANSI C@t{++} compiler (@code{aCC}).)
15567 @kindex set overload-resolution
15568 @cindex overloaded functions, overload resolution
15569 @item set overload-resolution on
15570 Enable overload resolution for C@t{++} expression evaluation. The default
15571 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15572 and searches for a function whose signature matches the argument types,
15573 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15574 Expressions, ,C@t{++} Expressions}, for details).
15575 If it cannot find a match, it emits a message.
15577 @item set overload-resolution off
15578 Disable overload resolution for C@t{++} expression evaluation. For
15579 overloaded functions that are not class member functions, @value{GDBN}
15580 chooses the first function of the specified name that it finds in the
15581 symbol table, whether or not its arguments are of the correct type. For
15582 overloaded functions that are class member functions, @value{GDBN}
15583 searches for a function whose signature @emph{exactly} matches the
15586 @kindex show overload-resolution
15587 @item show overload-resolution
15588 Show the current setting of overload resolution.
15590 @item @r{Overloaded symbol names}
15591 You can specify a particular definition of an overloaded symbol, using
15592 the same notation that is used to declare such symbols in C@t{++}: type
15593 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15594 also use the @value{GDBN} command-line word completion facilities to list the
15595 available choices, or to finish the type list for you.
15596 @xref{Completion,, Command Completion}, for details on how to do this.
15598 @item @r{Breakpoints in functions with ABI tags}
15600 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15601 correspond to changes in the ABI of a type, function, or variable that
15602 would not otherwise be reflected in a mangled name. See
15603 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15606 The ABI tags are visible in C@t{++} demangled names. For example, a
15607 function that returns a std::string:
15610 std::string function(int);
15614 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15615 tag, and @value{GDBN} displays the symbol like this:
15618 function[abi:cxx11](int)
15621 You can set a breakpoint on such functions simply as if they had no
15625 (gdb) b function(int)
15626 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15627 (gdb) info breakpoints
15628 Num Type Disp Enb Address What
15629 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15633 On the rare occasion you need to disambiguate between different ABI
15634 tags, you can do so by simply including the ABI tag in the function
15638 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15642 @node Decimal Floating Point
15643 @subsubsection Decimal Floating Point format
15644 @cindex decimal floating point format
15646 @value{GDBN} can examine, set and perform computations with numbers in
15647 decimal floating point format, which in the C language correspond to the
15648 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15649 specified by the extension to support decimal floating-point arithmetic.
15651 There are two encodings in use, depending on the architecture: BID (Binary
15652 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15653 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15656 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15657 to manipulate decimal floating point numbers, it is not possible to convert
15658 (using a cast, for example) integers wider than 32-bit to decimal float.
15660 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15661 point computations, error checking in decimal float operations ignores
15662 underflow, overflow and divide by zero exceptions.
15664 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15665 to inspect @code{_Decimal128} values stored in floating point registers.
15666 See @ref{PowerPC,,PowerPC} for more details.
15672 @value{GDBN} can be used to debug programs written in D and compiled with
15673 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15674 specific feature --- dynamic arrays.
15679 @cindex Go (programming language)
15680 @value{GDBN} can be used to debug programs written in Go and compiled with
15681 @file{gccgo} or @file{6g} compilers.
15683 Here is a summary of the Go-specific features and restrictions:
15686 @cindex current Go package
15687 @item The current Go package
15688 The name of the current package does not need to be specified when
15689 specifying global variables and functions.
15691 For example, given the program:
15695 var myglob = "Shall we?"
15701 When stopped inside @code{main} either of these work:
15705 (gdb) p main.myglob
15708 @cindex builtin Go types
15709 @item Builtin Go types
15710 The @code{string} type is recognized by @value{GDBN} and is printed
15713 @cindex builtin Go functions
15714 @item Builtin Go functions
15715 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15716 function and handles it internally.
15718 @cindex restrictions on Go expressions
15719 @item Restrictions on Go expressions
15720 All Go operators are supported except @code{&^}.
15721 The Go @code{_} ``blank identifier'' is not supported.
15722 Automatic dereferencing of pointers is not supported.
15726 @subsection Objective-C
15728 @cindex Objective-C
15729 This section provides information about some commands and command
15730 options that are useful for debugging Objective-C code. See also
15731 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15732 few more commands specific to Objective-C support.
15735 * Method Names in Commands::
15736 * The Print Command with Objective-C::
15739 @node Method Names in Commands
15740 @subsubsection Method Names in Commands
15742 The following commands have been extended to accept Objective-C method
15743 names as line specifications:
15745 @kindex clear@r{, and Objective-C}
15746 @kindex break@r{, and Objective-C}
15747 @kindex info line@r{, and Objective-C}
15748 @kindex jump@r{, and Objective-C}
15749 @kindex list@r{, and Objective-C}
15753 @item @code{info line}
15758 A fully qualified Objective-C method name is specified as
15761 -[@var{Class} @var{methodName}]
15764 where the minus sign is used to indicate an instance method and a
15765 plus sign (not shown) is used to indicate a class method. The class
15766 name @var{Class} and method name @var{methodName} are enclosed in
15767 brackets, similar to the way messages are specified in Objective-C
15768 source code. For example, to set a breakpoint at the @code{create}
15769 instance method of class @code{Fruit} in the program currently being
15773 break -[Fruit create]
15776 To list ten program lines around the @code{initialize} class method,
15780 list +[NSText initialize]
15783 In the current version of @value{GDBN}, the plus or minus sign is
15784 required. In future versions of @value{GDBN}, the plus or minus
15785 sign will be optional, but you can use it to narrow the search. It
15786 is also possible to specify just a method name:
15792 You must specify the complete method name, including any colons. If
15793 your program's source files contain more than one @code{create} method,
15794 you'll be presented with a numbered list of classes that implement that
15795 method. Indicate your choice by number, or type @samp{0} to exit if
15798 As another example, to clear a breakpoint established at the
15799 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15802 clear -[NSWindow makeKeyAndOrderFront:]
15805 @node The Print Command with Objective-C
15806 @subsubsection The Print Command With Objective-C
15807 @cindex Objective-C, print objects
15808 @kindex print-object
15809 @kindex po @r{(@code{print-object})}
15811 The print command has also been extended to accept methods. For example:
15814 print -[@var{object} hash]
15817 @cindex print an Objective-C object description
15818 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15820 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15821 and print the result. Also, an additional command has been added,
15822 @code{print-object} or @code{po} for short, which is meant to print
15823 the description of an object. However, this command may only work
15824 with certain Objective-C libraries that have a particular hook
15825 function, @code{_NSPrintForDebugger}, defined.
15828 @subsection OpenCL C
15831 This section provides information about @value{GDBN}s OpenCL C support.
15834 * OpenCL C Datatypes::
15835 * OpenCL C Expressions::
15836 * OpenCL C Operators::
15839 @node OpenCL C Datatypes
15840 @subsubsection OpenCL C Datatypes
15842 @cindex OpenCL C Datatypes
15843 @value{GDBN} supports the builtin scalar and vector datatypes specified
15844 by OpenCL 1.1. In addition the half- and double-precision floating point
15845 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15846 extensions are also known to @value{GDBN}.
15848 @node OpenCL C Expressions
15849 @subsubsection OpenCL C Expressions
15851 @cindex OpenCL C Expressions
15852 @value{GDBN} supports accesses to vector components including the access as
15853 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15854 supported by @value{GDBN} can be used as well.
15856 @node OpenCL C Operators
15857 @subsubsection OpenCL C Operators
15859 @cindex OpenCL C Operators
15860 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15864 @subsection Fortran
15865 @cindex Fortran-specific support in @value{GDBN}
15867 @value{GDBN} can be used to debug programs written in Fortran, but it
15868 currently supports only the features of Fortran 77 language.
15870 @cindex trailing underscore, in Fortran symbols
15871 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15872 among them) append an underscore to the names of variables and
15873 functions. When you debug programs compiled by those compilers, you
15874 will need to refer to variables and functions with a trailing
15878 * Fortran Operators:: Fortran operators and expressions
15879 * Fortran Defaults:: Default settings for Fortran
15880 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15883 @node Fortran Operators
15884 @subsubsection Fortran Operators and Expressions
15886 @cindex Fortran operators and expressions
15888 Operators must be defined on values of specific types. For instance,
15889 @code{+} is defined on numbers, but not on characters or other non-
15890 arithmetic types. Operators are often defined on groups of types.
15894 The exponentiation operator. It raises the first operand to the power
15898 The range operator. Normally used in the form of array(low:high) to
15899 represent a section of array.
15902 The access component operator. Normally used to access elements in derived
15903 types. Also suitable for unions. As unions aren't part of regular Fortran,
15904 this can only happen when accessing a register that uses a gdbarch-defined
15908 @node Fortran Defaults
15909 @subsubsection Fortran Defaults
15911 @cindex Fortran Defaults
15913 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15914 default uses case-insensitive matches for Fortran symbols. You can
15915 change that with the @samp{set case-insensitive} command, see
15916 @ref{Symbols}, for the details.
15918 @node Special Fortran Commands
15919 @subsubsection Special Fortran Commands
15921 @cindex Special Fortran commands
15923 @value{GDBN} has some commands to support Fortran-specific features,
15924 such as displaying common blocks.
15927 @cindex @code{COMMON} blocks, Fortran
15928 @kindex info common
15929 @item info common @r{[}@var{common-name}@r{]}
15930 This command prints the values contained in the Fortran @code{COMMON}
15931 block whose name is @var{common-name}. With no argument, the names of
15932 all @code{COMMON} blocks visible at the current program location are
15939 @cindex Pascal support in @value{GDBN}, limitations
15940 Debugging Pascal programs which use sets, subranges, file variables, or
15941 nested functions does not currently work. @value{GDBN} does not support
15942 entering expressions, printing values, or similar features using Pascal
15945 The Pascal-specific command @code{set print pascal_static-members}
15946 controls whether static members of Pascal objects are displayed.
15947 @xref{Print Settings, pascal_static-members}.
15952 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15953 Programming Language}. Type- and value-printing, and expression
15954 parsing, are reasonably complete. However, there are a few
15955 peculiarities and holes to be aware of.
15959 Linespecs (@pxref{Specify Location}) are never relative to the current
15960 crate. Instead, they act as if there were a global namespace of
15961 crates, somewhat similar to the way @code{extern crate} behaves.
15963 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15964 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15965 to set a breakpoint in a function named @samp{f} in a crate named
15968 As a consequence of this approach, linespecs also cannot refer to
15969 items using @samp{self::} or @samp{super::}.
15972 Because @value{GDBN} implements Rust name-lookup semantics in
15973 expressions, it will sometimes prepend the current crate to a name.
15974 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15975 @samp{K}, then @code{print ::x::y} will try to find the symbol
15978 However, since it is useful to be able to refer to other crates when
15979 debugging, @value{GDBN} provides the @code{extern} extension to
15980 circumvent this. To use the extension, just put @code{extern} before
15981 a path expression to refer to the otherwise unavailable ``global''
15984 In the above example, if you wanted to refer to the symbol @samp{y} in
15985 the crate @samp{x}, you would use @code{print extern x::y}.
15988 The Rust expression evaluator does not support ``statement-like''
15989 expressions such as @code{if} or @code{match}, or lambda expressions.
15992 Tuple expressions are not implemented.
15995 The Rust expression evaluator does not currently implement the
15996 @code{Drop} trait. Objects that may be created by the evaluator will
15997 never be destroyed.
16000 @value{GDBN} does not implement type inference for generics. In order
16001 to call generic functions or otherwise refer to generic items, you
16002 will have to specify the type parameters manually.
16005 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
16006 cases this does not cause any problems. However, in an expression
16007 context, completing a generic function name will give syntactically
16008 invalid results. This happens because Rust requires the @samp{::}
16009 operator between the function name and its generic arguments. For
16010 example, @value{GDBN} might provide a completion like
16011 @code{crate::f<u32>}, where the parser would require
16012 @code{crate::f::<u32>}.
16015 As of this writing, the Rust compiler (version 1.8) has a few holes in
16016 the debugging information it generates. These holes prevent certain
16017 features from being implemented by @value{GDBN}:
16021 Method calls cannot be made via traits.
16024 Operator overloading is not implemented.
16027 When debugging in a monomorphized function, you cannot use the generic
16031 The type @code{Self} is not available.
16034 @code{use} statements are not available, so some names may not be
16035 available in the crate.
16040 @subsection Modula-2
16042 @cindex Modula-2, @value{GDBN} support
16044 The extensions made to @value{GDBN} to support Modula-2 only support
16045 output from the @sc{gnu} Modula-2 compiler (which is currently being
16046 developed). Other Modula-2 compilers are not currently supported, and
16047 attempting to debug executables produced by them is most likely
16048 to give an error as @value{GDBN} reads in the executable's symbol
16051 @cindex expressions in Modula-2
16053 * M2 Operators:: Built-in operators
16054 * Built-In Func/Proc:: Built-in functions and procedures
16055 * M2 Constants:: Modula-2 constants
16056 * M2 Types:: Modula-2 types
16057 * M2 Defaults:: Default settings for Modula-2
16058 * Deviations:: Deviations from standard Modula-2
16059 * M2 Checks:: Modula-2 type and range checks
16060 * M2 Scope:: The scope operators @code{::} and @code{.}
16061 * GDB/M2:: @value{GDBN} and Modula-2
16065 @subsubsection Operators
16066 @cindex Modula-2 operators
16068 Operators must be defined on values of specific types. For instance,
16069 @code{+} is defined on numbers, but not on structures. Operators are
16070 often defined on groups of types. For the purposes of Modula-2, the
16071 following definitions hold:
16076 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
16080 @emph{Character types} consist of @code{CHAR} and its subranges.
16083 @emph{Floating-point types} consist of @code{REAL}.
16086 @emph{Pointer types} consist of anything declared as @code{POINTER TO
16090 @emph{Scalar types} consist of all of the above.
16093 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
16096 @emph{Boolean types} consist of @code{BOOLEAN}.
16100 The following operators are supported, and appear in order of
16101 increasing precedence:
16105 Function argument or array index separator.
16108 Assignment. The value of @var{var} @code{:=} @var{value} is
16112 Less than, greater than on integral, floating-point, or enumerated
16116 Less than or equal to, greater than or equal to
16117 on integral, floating-point and enumerated types, or set inclusion on
16118 set types. Same precedence as @code{<}.
16120 @item =@r{, }<>@r{, }#
16121 Equality and two ways of expressing inequality, valid on scalar types.
16122 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
16123 available for inequality, since @code{#} conflicts with the script
16127 Set membership. Defined on set types and the types of their members.
16128 Same precedence as @code{<}.
16131 Boolean disjunction. Defined on boolean types.
16134 Boolean conjunction. Defined on boolean types.
16137 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16140 Addition and subtraction on integral and floating-point types, or union
16141 and difference on set types.
16144 Multiplication on integral and floating-point types, or set intersection
16148 Division on floating-point types, or symmetric set difference on set
16149 types. Same precedence as @code{*}.
16152 Integer division and remainder. Defined on integral types. Same
16153 precedence as @code{*}.
16156 Negative. Defined on @code{INTEGER} and @code{REAL} data.
16159 Pointer dereferencing. Defined on pointer types.
16162 Boolean negation. Defined on boolean types. Same precedence as
16166 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
16167 precedence as @code{^}.
16170 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
16173 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
16177 @value{GDBN} and Modula-2 scope operators.
16181 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
16182 treats the use of the operator @code{IN}, or the use of operators
16183 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
16184 @code{<=}, and @code{>=} on sets as an error.
16188 @node Built-In Func/Proc
16189 @subsubsection Built-in Functions and Procedures
16190 @cindex Modula-2 built-ins
16192 Modula-2 also makes available several built-in procedures and functions.
16193 In describing these, the following metavariables are used:
16198 represents an @code{ARRAY} variable.
16201 represents a @code{CHAR} constant or variable.
16204 represents a variable or constant of integral type.
16207 represents an identifier that belongs to a set. Generally used in the
16208 same function with the metavariable @var{s}. The type of @var{s} should
16209 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
16212 represents a variable or constant of integral or floating-point type.
16215 represents a variable or constant of floating-point type.
16221 represents a variable.
16224 represents a variable or constant of one of many types. See the
16225 explanation of the function for details.
16228 All Modula-2 built-in procedures also return a result, described below.
16232 Returns the absolute value of @var{n}.
16235 If @var{c} is a lower case letter, it returns its upper case
16236 equivalent, otherwise it returns its argument.
16239 Returns the character whose ordinal value is @var{i}.
16242 Decrements the value in the variable @var{v} by one. Returns the new value.
16244 @item DEC(@var{v},@var{i})
16245 Decrements the value in the variable @var{v} by @var{i}. Returns the
16248 @item EXCL(@var{m},@var{s})
16249 Removes the element @var{m} from the set @var{s}. Returns the new
16252 @item FLOAT(@var{i})
16253 Returns the floating point equivalent of the integer @var{i}.
16255 @item HIGH(@var{a})
16256 Returns the index of the last member of @var{a}.
16259 Increments the value in the variable @var{v} by one. Returns the new value.
16261 @item INC(@var{v},@var{i})
16262 Increments the value in the variable @var{v} by @var{i}. Returns the
16265 @item INCL(@var{m},@var{s})
16266 Adds the element @var{m} to the set @var{s} if it is not already
16267 there. Returns the new set.
16270 Returns the maximum value of the type @var{t}.
16273 Returns the minimum value of the type @var{t}.
16276 Returns boolean TRUE if @var{i} is an odd number.
16279 Returns the ordinal value of its argument. For example, the ordinal
16280 value of a character is its @sc{ascii} value (on machines supporting
16281 the @sc{ascii} character set). The argument @var{x} must be of an
16282 ordered type, which include integral, character and enumerated types.
16284 @item SIZE(@var{x})
16285 Returns the size of its argument. The argument @var{x} can be a
16286 variable or a type.
16288 @item TRUNC(@var{r})
16289 Returns the integral part of @var{r}.
16291 @item TSIZE(@var{x})
16292 Returns the size of its argument. The argument @var{x} can be a
16293 variable or a type.
16295 @item VAL(@var{t},@var{i})
16296 Returns the member of the type @var{t} whose ordinal value is @var{i}.
16300 @emph{Warning:} Sets and their operations are not yet supported, so
16301 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
16305 @cindex Modula-2 constants
16307 @subsubsection Constants
16309 @value{GDBN} allows you to express the constants of Modula-2 in the following
16315 Integer constants are simply a sequence of digits. When used in an
16316 expression, a constant is interpreted to be type-compatible with the
16317 rest of the expression. Hexadecimal integers are specified by a
16318 trailing @samp{H}, and octal integers by a trailing @samp{B}.
16321 Floating point constants appear as a sequence of digits, followed by a
16322 decimal point and another sequence of digits. An optional exponent can
16323 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
16324 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
16325 digits of the floating point constant must be valid decimal (base 10)
16329 Character constants consist of a single character enclosed by a pair of
16330 like quotes, either single (@code{'}) or double (@code{"}). They may
16331 also be expressed by their ordinal value (their @sc{ascii} value, usually)
16332 followed by a @samp{C}.
16335 String constants consist of a sequence of characters enclosed by a
16336 pair of like quotes, either single (@code{'}) or double (@code{"}).
16337 Escape sequences in the style of C are also allowed. @xref{C
16338 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
16342 Enumerated constants consist of an enumerated identifier.
16345 Boolean constants consist of the identifiers @code{TRUE} and
16349 Pointer constants consist of integral values only.
16352 Set constants are not yet supported.
16356 @subsubsection Modula-2 Types
16357 @cindex Modula-2 types
16359 Currently @value{GDBN} can print the following data types in Modula-2
16360 syntax: array types, record types, set types, pointer types, procedure
16361 types, enumerated types, subrange types and base types. You can also
16362 print the contents of variables declared using these type.
16363 This section gives a number of simple source code examples together with
16364 sample @value{GDBN} sessions.
16366 The first example contains the following section of code:
16375 and you can request @value{GDBN} to interrogate the type and value of
16376 @code{r} and @code{s}.
16379 (@value{GDBP}) print s
16381 (@value{GDBP}) ptype s
16383 (@value{GDBP}) print r
16385 (@value{GDBP}) ptype r
16390 Likewise if your source code declares @code{s} as:
16394 s: SET ['A'..'Z'] ;
16398 then you may query the type of @code{s} by:
16401 (@value{GDBP}) ptype s
16402 type = SET ['A'..'Z']
16406 Note that at present you cannot interactively manipulate set
16407 expressions using the debugger.
16409 The following example shows how you might declare an array in Modula-2
16410 and how you can interact with @value{GDBN} to print its type and contents:
16414 s: ARRAY [-10..10] OF CHAR ;
16418 (@value{GDBP}) ptype s
16419 ARRAY [-10..10] OF CHAR
16422 Note that the array handling is not yet complete and although the type
16423 is printed correctly, expression handling still assumes that all
16424 arrays have a lower bound of zero and not @code{-10} as in the example
16427 Here are some more type related Modula-2 examples:
16431 colour = (blue, red, yellow, green) ;
16432 t = [blue..yellow] ;
16440 The @value{GDBN} interaction shows how you can query the data type
16441 and value of a variable.
16444 (@value{GDBP}) print s
16446 (@value{GDBP}) ptype t
16447 type = [blue..yellow]
16451 In this example a Modula-2 array is declared and its contents
16452 displayed. Observe that the contents are written in the same way as
16453 their @code{C} counterparts.
16457 s: ARRAY [1..5] OF CARDINAL ;
16463 (@value{GDBP}) print s
16464 $1 = @{1, 0, 0, 0, 0@}
16465 (@value{GDBP}) ptype s
16466 type = ARRAY [1..5] OF CARDINAL
16469 The Modula-2 language interface to @value{GDBN} also understands
16470 pointer types as shown in this example:
16474 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16481 and you can request that @value{GDBN} describes the type of @code{s}.
16484 (@value{GDBP}) ptype s
16485 type = POINTER TO ARRAY [1..5] OF CARDINAL
16488 @value{GDBN} handles compound types as we can see in this example.
16489 Here we combine array types, record types, pointer types and subrange
16500 myarray = ARRAY myrange OF CARDINAL ;
16501 myrange = [-2..2] ;
16503 s: POINTER TO ARRAY myrange OF foo ;
16507 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16511 (@value{GDBP}) ptype s
16512 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16515 f3 : ARRAY [-2..2] OF CARDINAL;
16520 @subsubsection Modula-2 Defaults
16521 @cindex Modula-2 defaults
16523 If type and range checking are set automatically by @value{GDBN}, they
16524 both default to @code{on} whenever the working language changes to
16525 Modula-2. This happens regardless of whether you or @value{GDBN}
16526 selected the working language.
16528 If you allow @value{GDBN} to set the language automatically, then entering
16529 code compiled from a file whose name ends with @file{.mod} sets the
16530 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16531 Infer the Source Language}, for further details.
16534 @subsubsection Deviations from Standard Modula-2
16535 @cindex Modula-2, deviations from
16537 A few changes have been made to make Modula-2 programs easier to debug.
16538 This is done primarily via loosening its type strictness:
16542 Unlike in standard Modula-2, pointer constants can be formed by
16543 integers. This allows you to modify pointer variables during
16544 debugging. (In standard Modula-2, the actual address contained in a
16545 pointer variable is hidden from you; it can only be modified
16546 through direct assignment to another pointer variable or expression that
16547 returned a pointer.)
16550 C escape sequences can be used in strings and characters to represent
16551 non-printable characters. @value{GDBN} prints out strings with these
16552 escape sequences embedded. Single non-printable characters are
16553 printed using the @samp{CHR(@var{nnn})} format.
16556 The assignment operator (@code{:=}) returns the value of its right-hand
16560 All built-in procedures both modify @emph{and} return their argument.
16564 @subsubsection Modula-2 Type and Range Checks
16565 @cindex Modula-2 checks
16568 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16571 @c FIXME remove warning when type/range checks added
16573 @value{GDBN} considers two Modula-2 variables type equivalent if:
16577 They are of types that have been declared equivalent via a @code{TYPE
16578 @var{t1} = @var{t2}} statement
16581 They have been declared on the same line. (Note: This is true of the
16582 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16585 As long as type checking is enabled, any attempt to combine variables
16586 whose types are not equivalent is an error.
16588 Range checking is done on all mathematical operations, assignment, array
16589 index bounds, and all built-in functions and procedures.
16592 @subsubsection The Scope Operators @code{::} and @code{.}
16594 @cindex @code{.}, Modula-2 scope operator
16595 @cindex colon, doubled as scope operator
16597 @vindex colon-colon@r{, in Modula-2}
16598 @c Info cannot handle :: but TeX can.
16601 @vindex ::@r{, in Modula-2}
16604 There are a few subtle differences between the Modula-2 scope operator
16605 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16610 @var{module} . @var{id}
16611 @var{scope} :: @var{id}
16615 where @var{scope} is the name of a module or a procedure,
16616 @var{module} the name of a module, and @var{id} is any declared
16617 identifier within your program, except another module.
16619 Using the @code{::} operator makes @value{GDBN} search the scope
16620 specified by @var{scope} for the identifier @var{id}. If it is not
16621 found in the specified scope, then @value{GDBN} searches all scopes
16622 enclosing the one specified by @var{scope}.
16624 Using the @code{.} operator makes @value{GDBN} search the current scope for
16625 the identifier specified by @var{id} that was imported from the
16626 definition module specified by @var{module}. With this operator, it is
16627 an error if the identifier @var{id} was not imported from definition
16628 module @var{module}, or if @var{id} is not an identifier in
16632 @subsubsection @value{GDBN} and Modula-2
16634 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16635 Five subcommands of @code{set print} and @code{show print} apply
16636 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16637 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16638 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16639 analogue in Modula-2.
16641 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16642 with any language, is not useful with Modula-2. Its
16643 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16644 created in Modula-2 as they can in C or C@t{++}. However, because an
16645 address can be specified by an integral constant, the construct
16646 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16648 @cindex @code{#} in Modula-2
16649 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16650 interpreted as the beginning of a comment. Use @code{<>} instead.
16656 The extensions made to @value{GDBN} for Ada only support
16657 output from the @sc{gnu} Ada (GNAT) compiler.
16658 Other Ada compilers are not currently supported, and
16659 attempting to debug executables produced by them is most likely
16663 @cindex expressions in Ada
16665 * Ada Mode Intro:: General remarks on the Ada syntax
16666 and semantics supported by Ada mode
16668 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16669 * Additions to Ada:: Extensions of the Ada expression syntax.
16670 * Overloading support for Ada:: Support for expressions involving overloaded
16672 * Stopping Before Main Program:: Debugging the program during elaboration.
16673 * Ada Exceptions:: Ada Exceptions
16674 * Ada Tasks:: Listing and setting breakpoints in tasks.
16675 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16676 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16678 * Ada Settings:: New settable GDB parameters for Ada.
16679 * Ada Glitches:: Known peculiarities of Ada mode.
16682 @node Ada Mode Intro
16683 @subsubsection Introduction
16684 @cindex Ada mode, general
16686 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16687 syntax, with some extensions.
16688 The philosophy behind the design of this subset is
16692 That @value{GDBN} should provide basic literals and access to operations for
16693 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16694 leaving more sophisticated computations to subprograms written into the
16695 program (which therefore may be called from @value{GDBN}).
16698 That type safety and strict adherence to Ada language restrictions
16699 are not particularly important to the @value{GDBN} user.
16702 That brevity is important to the @value{GDBN} user.
16705 Thus, for brevity, the debugger acts as if all names declared in
16706 user-written packages are directly visible, even if they are not visible
16707 according to Ada rules, thus making it unnecessary to fully qualify most
16708 names with their packages, regardless of context. Where this causes
16709 ambiguity, @value{GDBN} asks the user's intent.
16711 The debugger will start in Ada mode if it detects an Ada main program.
16712 As for other languages, it will enter Ada mode when stopped in a program that
16713 was translated from an Ada source file.
16715 While in Ada mode, you may use `@t{--}' for comments. This is useful
16716 mostly for documenting command files. The standard @value{GDBN} comment
16717 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16718 middle (to allow based literals).
16720 @node Omissions from Ada
16721 @subsubsection Omissions from Ada
16722 @cindex Ada, omissions from
16724 Here are the notable omissions from the subset:
16728 Only a subset of the attributes are supported:
16732 @t{'First}, @t{'Last}, and @t{'Length}
16733 on array objects (not on types and subtypes).
16736 @t{'Min} and @t{'Max}.
16739 @t{'Pos} and @t{'Val}.
16745 @t{'Range} on array objects (not subtypes), but only as the right
16746 operand of the membership (@code{in}) operator.
16749 @t{'Access}, @t{'Unchecked_Access}, and
16750 @t{'Unrestricted_Access} (a GNAT extension).
16758 @code{Characters.Latin_1} are not available and
16759 concatenation is not implemented. Thus, escape characters in strings are
16760 not currently available.
16763 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16764 equality of representations. They will generally work correctly
16765 for strings and arrays whose elements have integer or enumeration types.
16766 They may not work correctly for arrays whose element
16767 types have user-defined equality, for arrays of real values
16768 (in particular, IEEE-conformant floating point, because of negative
16769 zeroes and NaNs), and for arrays whose elements contain unused bits with
16770 indeterminate values.
16773 The other component-by-component array operations (@code{and}, @code{or},
16774 @code{xor}, @code{not}, and relational tests other than equality)
16775 are not implemented.
16778 @cindex array aggregates (Ada)
16779 @cindex record aggregates (Ada)
16780 @cindex aggregates (Ada)
16781 There is limited support for array and record aggregates. They are
16782 permitted only on the right sides of assignments, as in these examples:
16785 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16786 (@value{GDBP}) set An_Array := (1, others => 0)
16787 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16788 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16789 (@value{GDBP}) set A_Record := (1, "Peter", True);
16790 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16794 discriminant's value by assigning an aggregate has an
16795 undefined effect if that discriminant is used within the record.
16796 However, you can first modify discriminants by directly assigning to
16797 them (which normally would not be allowed in Ada), and then performing an
16798 aggregate assignment. For example, given a variable @code{A_Rec}
16799 declared to have a type such as:
16802 type Rec (Len : Small_Integer := 0) is record
16804 Vals : IntArray (1 .. Len);
16808 you can assign a value with a different size of @code{Vals} with two
16812 (@value{GDBP}) set A_Rec.Len := 4
16813 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16816 As this example also illustrates, @value{GDBN} is very loose about the usual
16817 rules concerning aggregates. You may leave out some of the
16818 components of an array or record aggregate (such as the @code{Len}
16819 component in the assignment to @code{A_Rec} above); they will retain their
16820 original values upon assignment. You may freely use dynamic values as
16821 indices in component associations. You may even use overlapping or
16822 redundant component associations, although which component values are
16823 assigned in such cases is not defined.
16826 Calls to dispatching subprograms are not implemented.
16829 The overloading algorithm is much more limited (i.e., less selective)
16830 than that of real Ada. It makes only limited use of the context in
16831 which a subexpression appears to resolve its meaning, and it is much
16832 looser in its rules for allowing type matches. As a result, some
16833 function calls will be ambiguous, and the user will be asked to choose
16834 the proper resolution.
16837 The @code{new} operator is not implemented.
16840 Entry calls are not implemented.
16843 Aside from printing, arithmetic operations on the native VAX floating-point
16844 formats are not supported.
16847 It is not possible to slice a packed array.
16850 The names @code{True} and @code{False}, when not part of a qualified name,
16851 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16853 Should your program
16854 redefine these names in a package or procedure (at best a dubious practice),
16855 you will have to use fully qualified names to access their new definitions.
16858 @node Additions to Ada
16859 @subsubsection Additions to Ada
16860 @cindex Ada, deviations from
16862 As it does for other languages, @value{GDBN} makes certain generic
16863 extensions to Ada (@pxref{Expressions}):
16867 If the expression @var{E} is a variable residing in memory (typically
16868 a local variable or array element) and @var{N} is a positive integer,
16869 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16870 @var{N}-1 adjacent variables following it in memory as an array. In
16871 Ada, this operator is generally not necessary, since its prime use is
16872 in displaying parts of an array, and slicing will usually do this in
16873 Ada. However, there are occasional uses when debugging programs in
16874 which certain debugging information has been optimized away.
16877 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16878 appears in function or file @var{B}.'' When @var{B} is a file name,
16879 you must typically surround it in single quotes.
16882 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16883 @var{type} that appears at address @var{addr}.''
16886 A name starting with @samp{$} is a convenience variable
16887 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16890 In addition, @value{GDBN} provides a few other shortcuts and outright
16891 additions specific to Ada:
16895 The assignment statement is allowed as an expression, returning
16896 its right-hand operand as its value. Thus, you may enter
16899 (@value{GDBP}) set x := y + 3
16900 (@value{GDBP}) print A(tmp := y + 1)
16904 The semicolon is allowed as an ``operator,'' returning as its value
16905 the value of its right-hand operand.
16906 This allows, for example,
16907 complex conditional breaks:
16910 (@value{GDBP}) break f
16911 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16915 Rather than use catenation and symbolic character names to introduce special
16916 characters into strings, one may instead use a special bracket notation,
16917 which is also used to print strings. A sequence of characters of the form
16918 @samp{["@var{XX}"]} within a string or character literal denotes the
16919 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16920 sequence of characters @samp{["""]} also denotes a single quotation mark
16921 in strings. For example,
16923 "One line.["0a"]Next line.["0a"]"
16926 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16930 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16931 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16935 (@value{GDBP}) print 'max(x, y)
16939 When printing arrays, @value{GDBN} uses positional notation when the
16940 array has a lower bound of 1, and uses a modified named notation otherwise.
16941 For example, a one-dimensional array of three integers with a lower bound
16942 of 3 might print as
16949 That is, in contrast to valid Ada, only the first component has a @code{=>}
16953 You may abbreviate attributes in expressions with any unique,
16954 multi-character subsequence of
16955 their names (an exact match gets preference).
16956 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16957 in place of @t{a'length}.
16960 @cindex quoting Ada internal identifiers
16961 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16962 to lower case. The GNAT compiler uses upper-case characters for
16963 some of its internal identifiers, which are normally of no interest to users.
16964 For the rare occasions when you actually have to look at them,
16965 enclose them in angle brackets to avoid the lower-case mapping.
16968 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16972 Printing an object of class-wide type or dereferencing an
16973 access-to-class-wide value will display all the components of the object's
16974 specific type (as indicated by its run-time tag). Likewise, component
16975 selection on such a value will operate on the specific type of the
16980 @node Overloading support for Ada
16981 @subsubsection Overloading support for Ada
16982 @cindex overloading, Ada
16984 The debugger supports limited overloading. Given a subprogram call in which
16985 the function symbol has multiple definitions, it will use the number of
16986 actual parameters and some information about their types to attempt to narrow
16987 the set of definitions. It also makes very limited use of context, preferring
16988 procedures to functions in the context of the @code{call} command, and
16989 functions to procedures elsewhere.
16991 If, after narrowing, the set of matching definitions still contains more than
16992 one definition, @value{GDBN} will display a menu to query which one it should
16996 (@value{GDBP}) print f(1)
16997 Multiple matches for f
16999 [1] foo.f (integer) return boolean at foo.adb:23
17000 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
17004 In this case, just select one menu entry either to cancel expression evaluation
17005 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
17006 instance (type the corresponding number and press @key{RET}).
17008 Here are a couple of commands to customize @value{GDBN}'s behavior in this
17013 @kindex set ada print-signatures
17014 @item set ada print-signatures
17015 Control whether parameter types and return types are displayed in overloads
17016 selection menus. It is @code{on} by default.
17017 @xref{Overloading support for Ada}.
17019 @kindex show ada print-signatures
17020 @item show ada print-signatures
17021 Show the current setting for displaying parameter types and return types in
17022 overloads selection menu.
17023 @xref{Overloading support for Ada}.
17027 @node Stopping Before Main Program
17028 @subsubsection Stopping at the Very Beginning
17030 @cindex breakpointing Ada elaboration code
17031 It is sometimes necessary to debug the program during elaboration, and
17032 before reaching the main procedure.
17033 As defined in the Ada Reference
17034 Manual, the elaboration code is invoked from a procedure called
17035 @code{adainit}. To run your program up to the beginning of
17036 elaboration, simply use the following two commands:
17037 @code{tbreak adainit} and @code{run}.
17039 @node Ada Exceptions
17040 @subsubsection Ada Exceptions
17042 A command is provided to list all Ada exceptions:
17045 @kindex info exceptions
17046 @item info exceptions
17047 @itemx info exceptions @var{regexp}
17048 The @code{info exceptions} command allows you to list all Ada exceptions
17049 defined within the program being debugged, as well as their addresses.
17050 With a regular expression, @var{regexp}, as argument, only those exceptions
17051 whose names match @var{regexp} are listed.
17054 Below is a small example, showing how the command can be used, first
17055 without argument, and next with a regular expression passed as an
17059 (@value{GDBP}) info exceptions
17060 All defined Ada exceptions:
17061 constraint_error: 0x613da0
17062 program_error: 0x613d20
17063 storage_error: 0x613ce0
17064 tasking_error: 0x613ca0
17065 const.aint_global_e: 0x613b00
17066 (@value{GDBP}) info exceptions const.aint
17067 All Ada exceptions matching regular expression "const.aint":
17068 constraint_error: 0x613da0
17069 const.aint_global_e: 0x613b00
17072 It is also possible to ask @value{GDBN} to stop your program's execution
17073 when an exception is raised. For more details, see @ref{Set Catchpoints}.
17076 @subsubsection Extensions for Ada Tasks
17077 @cindex Ada, tasking
17079 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
17080 @value{GDBN} provides the following task-related commands:
17085 This command shows a list of current Ada tasks, as in the following example:
17092 (@value{GDBP}) info tasks
17093 ID TID P-ID Pri State Name
17094 1 8088000 0 15 Child Activation Wait main_task
17095 2 80a4000 1 15 Accept Statement b
17096 3 809a800 1 15 Child Activation Wait a
17097 * 4 80ae800 3 15 Runnable c
17102 In this listing, the asterisk before the last task indicates it to be the
17103 task currently being inspected.
17107 Represents @value{GDBN}'s internal task number.
17113 The parent's task ID (@value{GDBN}'s internal task number).
17116 The base priority of the task.
17119 Current state of the task.
17123 The task has been created but has not been activated. It cannot be
17127 The task is not blocked for any reason known to Ada. (It may be waiting
17128 for a mutex, though.) It is conceptually "executing" in normal mode.
17131 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
17132 that were waiting on terminate alternatives have been awakened and have
17133 terminated themselves.
17135 @item Child Activation Wait
17136 The task is waiting for created tasks to complete activation.
17138 @item Accept Statement
17139 The task is waiting on an accept or selective wait statement.
17141 @item Waiting on entry call
17142 The task is waiting on an entry call.
17144 @item Async Select Wait
17145 The task is waiting to start the abortable part of an asynchronous
17149 The task is waiting on a select statement with only a delay
17152 @item Child Termination Wait
17153 The task is sleeping having completed a master within itself, and is
17154 waiting for the tasks dependent on that master to become terminated or
17155 waiting on a terminate Phase.
17157 @item Wait Child in Term Alt
17158 The task is sleeping waiting for tasks on terminate alternatives to
17159 finish terminating.
17161 @item Accepting RV with @var{taskno}
17162 The task is accepting a rendez-vous with the task @var{taskno}.
17166 Name of the task in the program.
17170 @kindex info task @var{taskno}
17171 @item info task @var{taskno}
17172 This command shows detailled informations on the specified task, as in
17173 the following example:
17178 (@value{GDBP}) info tasks
17179 ID TID P-ID Pri State Name
17180 1 8077880 0 15 Child Activation Wait main_task
17181 * 2 807c468 1 15 Runnable task_1
17182 (@value{GDBP}) info task 2
17183 Ada Task: 0x807c468
17187 Parent: 1 (main_task)
17193 @kindex task@r{ (Ada)}
17194 @cindex current Ada task ID
17195 This command prints the ID of the current task.
17201 (@value{GDBP}) info tasks
17202 ID TID P-ID Pri State Name
17203 1 8077870 0 15 Child Activation Wait main_task
17204 * 2 807c458 1 15 Runnable t
17205 (@value{GDBP}) task
17206 [Current task is 2]
17209 @item task @var{taskno}
17210 @cindex Ada task switching
17211 This command is like the @code{thread @var{thread-id}}
17212 command (@pxref{Threads}). It switches the context of debugging
17213 from the current task to the given task.
17219 (@value{GDBP}) info tasks
17220 ID TID P-ID Pri State Name
17221 1 8077870 0 15 Child Activation Wait main_task
17222 * 2 807c458 1 15 Runnable t
17223 (@value{GDBP}) task 1
17224 [Switching to task 1]
17225 #0 0x8067726 in pthread_cond_wait ()
17227 #0 0x8067726 in pthread_cond_wait ()
17228 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
17229 #2 0x805cb63 in system.task_primitives.operations.sleep ()
17230 #3 0x806153e in system.tasking.stages.activate_tasks ()
17231 #4 0x804aacc in un () at un.adb:5
17234 @item break @var{location} task @var{taskno}
17235 @itemx break @var{location} task @var{taskno} if @dots{}
17236 @cindex breakpoints and tasks, in Ada
17237 @cindex task breakpoints, in Ada
17238 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
17239 These commands are like the @code{break @dots{} thread @dots{}}
17240 command (@pxref{Thread Stops}). The
17241 @var{location} argument specifies source lines, as described
17242 in @ref{Specify Location}.
17244 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
17245 to specify that you only want @value{GDBN} to stop the program when a
17246 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
17247 numeric task identifiers assigned by @value{GDBN}, shown in the first
17248 column of the @samp{info tasks} display.
17250 If you do not specify @samp{task @var{taskno}} when you set a
17251 breakpoint, the breakpoint applies to @emph{all} tasks of your
17254 You can use the @code{task} qualifier on conditional breakpoints as
17255 well; in this case, place @samp{task @var{taskno}} before the
17256 breakpoint condition (before the @code{if}).
17264 (@value{GDBP}) info tasks
17265 ID TID P-ID Pri State Name
17266 1 140022020 0 15 Child Activation Wait main_task
17267 2 140045060 1 15 Accept/Select Wait t2
17268 3 140044840 1 15 Runnable t1
17269 * 4 140056040 1 15 Runnable t3
17270 (@value{GDBP}) b 15 task 2
17271 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
17272 (@value{GDBP}) cont
17277 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
17279 (@value{GDBP}) info tasks
17280 ID TID P-ID Pri State Name
17281 1 140022020 0 15 Child Activation Wait main_task
17282 * 2 140045060 1 15 Runnable t2
17283 3 140044840 1 15 Runnable t1
17284 4 140056040 1 15 Delay Sleep t3
17288 @node Ada Tasks and Core Files
17289 @subsubsection Tasking Support when Debugging Core Files
17290 @cindex Ada tasking and core file debugging
17292 When inspecting a core file, as opposed to debugging a live program,
17293 tasking support may be limited or even unavailable, depending on
17294 the platform being used.
17295 For instance, on x86-linux, the list of tasks is available, but task
17296 switching is not supported.
17298 On certain platforms, the debugger needs to perform some
17299 memory writes in order to provide Ada tasking support. When inspecting
17300 a core file, this means that the core file must be opened with read-write
17301 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
17302 Under these circumstances, you should make a backup copy of the core
17303 file before inspecting it with @value{GDBN}.
17305 @node Ravenscar Profile
17306 @subsubsection Tasking Support when using the Ravenscar Profile
17307 @cindex Ravenscar Profile
17309 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
17310 specifically designed for systems with safety-critical real-time
17314 @kindex set ravenscar task-switching on
17315 @cindex task switching with program using Ravenscar Profile
17316 @item set ravenscar task-switching on
17317 Allows task switching when debugging a program that uses the Ravenscar
17318 Profile. This is the default.
17320 @kindex set ravenscar task-switching off
17321 @item set ravenscar task-switching off
17322 Turn off task switching when debugging a program that uses the Ravenscar
17323 Profile. This is mostly intended to disable the code that adds support
17324 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
17325 the Ravenscar runtime is preventing @value{GDBN} from working properly.
17326 To be effective, this command should be run before the program is started.
17328 @kindex show ravenscar task-switching
17329 @item show ravenscar task-switching
17330 Show whether it is possible to switch from task to task in a program
17331 using the Ravenscar Profile.
17336 @subsubsection Ada Settings
17337 @cindex Ada settings
17340 @kindex set varsize-limit
17341 @item set varsize-limit @var{size}
17342 Prevent @value{GDBN} from attempting to evaluate objects whose size
17343 is above the given limit (@var{size}) when those sizes are computed
17344 from run-time quantities. This is typically the case when the object
17345 has a variable size, such as an array whose bounds are not known at
17346 compile time for example. Setting @var{size} to @code{unlimited}
17347 removes the size limitation. By default, the limit is about 65KB.
17349 The purpose of having such a limit is to prevent @value{GDBN} from
17350 trying to grab enormous chunks of virtual memory when asked to evaluate
17351 a quantity whose bounds have been corrupted or have not yet been fully
17352 initialized. The limit applies to the results of some subexpressions
17353 as well as to complete expressions. For example, an expression denoting
17354 a simple integer component, such as @code{x.y.z}, may fail if the size of
17355 @code{x.y} is variable and exceeds @code{size}. On the other hand,
17356 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
17357 @code{A} is an array variable with non-constant size, will generally
17358 succeed regardless of the bounds on @code{A}, as long as the component
17359 size is less than @var{size}.
17361 @kindex show varsize-limit
17362 @item show varsize-limit
17363 Show the limit on types whose size is determined by run-time quantities.
17367 @subsubsection Known Peculiarities of Ada Mode
17368 @cindex Ada, problems
17370 Besides the omissions listed previously (@pxref{Omissions from Ada}),
17371 we know of several problems with and limitations of Ada mode in
17373 some of which will be fixed with planned future releases of the debugger
17374 and the GNU Ada compiler.
17378 Static constants that the compiler chooses not to materialize as objects in
17379 storage are invisible to the debugger.
17382 Named parameter associations in function argument lists are ignored (the
17383 argument lists are treated as positional).
17386 Many useful library packages are currently invisible to the debugger.
17389 Fixed-point arithmetic, conversions, input, and output is carried out using
17390 floating-point arithmetic, and may give results that only approximate those on
17394 The GNAT compiler never generates the prefix @code{Standard} for any of
17395 the standard symbols defined by the Ada language. @value{GDBN} knows about
17396 this: it will strip the prefix from names when you use it, and will never
17397 look for a name you have so qualified among local symbols, nor match against
17398 symbols in other packages or subprograms. If you have
17399 defined entities anywhere in your program other than parameters and
17400 local variables whose simple names match names in @code{Standard},
17401 GNAT's lack of qualification here can cause confusion. When this happens,
17402 you can usually resolve the confusion
17403 by qualifying the problematic names with package
17404 @code{Standard} explicitly.
17407 Older versions of the compiler sometimes generate erroneous debugging
17408 information, resulting in the debugger incorrectly printing the value
17409 of affected entities. In some cases, the debugger is able to work
17410 around an issue automatically. In other cases, the debugger is able
17411 to work around the issue, but the work-around has to be specifically
17414 @kindex set ada trust-PAD-over-XVS
17415 @kindex show ada trust-PAD-over-XVS
17418 @item set ada trust-PAD-over-XVS on
17419 Configure GDB to strictly follow the GNAT encoding when computing the
17420 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
17421 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
17422 a complete description of the encoding used by the GNAT compiler).
17423 This is the default.
17425 @item set ada trust-PAD-over-XVS off
17426 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
17427 sometimes prints the wrong value for certain entities, changing @code{ada
17428 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
17429 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
17430 @code{off}, but this incurs a slight performance penalty, so it is
17431 recommended to leave this setting to @code{on} unless necessary.
17435 @cindex GNAT descriptive types
17436 @cindex GNAT encoding
17437 Internally, the debugger also relies on the compiler following a number
17438 of conventions known as the @samp{GNAT Encoding}, all documented in
17439 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
17440 how the debugging information should be generated for certain types.
17441 In particular, this convention makes use of @dfn{descriptive types},
17442 which are artificial types generated purely to help the debugger.
17444 These encodings were defined at a time when the debugging information
17445 format used was not powerful enough to describe some of the more complex
17446 types available in Ada. Since DWARF allows us to express nearly all
17447 Ada features, the long-term goal is to slowly replace these descriptive
17448 types by their pure DWARF equivalent. To facilitate that transition,
17449 a new maintenance option is available to force the debugger to ignore
17450 those descriptive types. It allows the user to quickly evaluate how
17451 well @value{GDBN} works without them.
17455 @kindex maint ada set ignore-descriptive-types
17456 @item maintenance ada set ignore-descriptive-types [on|off]
17457 Control whether the debugger should ignore descriptive types.
17458 The default is not to ignore descriptives types (@code{off}).
17460 @kindex maint ada show ignore-descriptive-types
17461 @item maintenance ada show ignore-descriptive-types
17462 Show if descriptive types are ignored by @value{GDBN}.
17466 @node Unsupported Languages
17467 @section Unsupported Languages
17469 @cindex unsupported languages
17470 @cindex minimal language
17471 In addition to the other fully-supported programming languages,
17472 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
17473 It does not represent a real programming language, but provides a set
17474 of capabilities close to what the C or assembly languages provide.
17475 This should allow most simple operations to be performed while debugging
17476 an application that uses a language currently not supported by @value{GDBN}.
17478 If the language is set to @code{auto}, @value{GDBN} will automatically
17479 select this language if the current frame corresponds to an unsupported
17483 @chapter Examining the Symbol Table
17485 The commands described in this chapter allow you to inquire about the
17486 symbols (names of variables, functions and types) defined in your
17487 program. This information is inherent in the text of your program and
17488 does not change as your program executes. @value{GDBN} finds it in your
17489 program's symbol table, in the file indicated when you started @value{GDBN}
17490 (@pxref{File Options, ,Choosing Files}), or by one of the
17491 file-management commands (@pxref{Files, ,Commands to Specify Files}).
17493 @cindex symbol names
17494 @cindex names of symbols
17495 @cindex quoting names
17496 @anchor{quoting names}
17497 Occasionally, you may need to refer to symbols that contain unusual
17498 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17499 most frequent case is in referring to static variables in other
17500 source files (@pxref{Variables,,Program Variables}). File names
17501 are recorded in object files as debugging symbols, but @value{GDBN} would
17502 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17503 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17504 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17511 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17514 @cindex case-insensitive symbol names
17515 @cindex case sensitivity in symbol names
17516 @kindex set case-sensitive
17517 @item set case-sensitive on
17518 @itemx set case-sensitive off
17519 @itemx set case-sensitive auto
17520 Normally, when @value{GDBN} looks up symbols, it matches their names
17521 with case sensitivity determined by the current source language.
17522 Occasionally, you may wish to control that. The command @code{set
17523 case-sensitive} lets you do that by specifying @code{on} for
17524 case-sensitive matches or @code{off} for case-insensitive ones. If
17525 you specify @code{auto}, case sensitivity is reset to the default
17526 suitable for the source language. The default is case-sensitive
17527 matches for all languages except for Fortran, for which the default is
17528 case-insensitive matches.
17530 @kindex show case-sensitive
17531 @item show case-sensitive
17532 This command shows the current setting of case sensitivity for symbols
17535 @kindex set print type methods
17536 @item set print type methods
17537 @itemx set print type methods on
17538 @itemx set print type methods off
17539 Normally, when @value{GDBN} prints a class, it displays any methods
17540 declared in that class. You can control this behavior either by
17541 passing the appropriate flag to @code{ptype}, or using @command{set
17542 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17543 display the methods; this is the default. Specifying @code{off} will
17544 cause @value{GDBN} to omit the methods.
17546 @kindex show print type methods
17547 @item show print type methods
17548 This command shows the current setting of method display when printing
17551 @kindex set print type nested-type-limit
17552 @item set print type nested-type-limit @var{limit}
17553 @itemx set print type nested-type-limit unlimited
17554 Set the limit of displayed nested types that the type printer will
17555 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
17556 nested definitions. By default, the type printer will not show any nested
17557 types defined in classes.
17559 @kindex show print type nested-type-limit
17560 @item show print type nested-type-limit
17561 This command shows the current display limit of nested types when
17564 @kindex set print type typedefs
17565 @item set print type typedefs
17566 @itemx set print type typedefs on
17567 @itemx set print type typedefs off
17569 Normally, when @value{GDBN} prints a class, it displays any typedefs
17570 defined in that class. You can control this behavior either by
17571 passing the appropriate flag to @code{ptype}, or using @command{set
17572 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17573 display the typedef definitions; this is the default. Specifying
17574 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17575 Note that this controls whether the typedef definition itself is
17576 printed, not whether typedef names are substituted when printing other
17579 @kindex show print type typedefs
17580 @item show print type typedefs
17581 This command shows the current setting of typedef display when
17584 @kindex info address
17585 @cindex address of a symbol
17586 @item info address @var{symbol}
17587 Describe where the data for @var{symbol} is stored. For a register
17588 variable, this says which register it is kept in. For a non-register
17589 local variable, this prints the stack-frame offset at which the variable
17592 Note the contrast with @samp{print &@var{symbol}}, which does not work
17593 at all for a register variable, and for a stack local variable prints
17594 the exact address of the current instantiation of the variable.
17596 @kindex info symbol
17597 @cindex symbol from address
17598 @cindex closest symbol and offset for an address
17599 @item info symbol @var{addr}
17600 Print the name of a symbol which is stored at the address @var{addr}.
17601 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17602 nearest symbol and an offset from it:
17605 (@value{GDBP}) info symbol 0x54320
17606 _initialize_vx + 396 in section .text
17610 This is the opposite of the @code{info address} command. You can use
17611 it to find out the name of a variable or a function given its address.
17613 For dynamically linked executables, the name of executable or shared
17614 library containing the symbol is also printed:
17617 (@value{GDBP}) info symbol 0x400225
17618 _start + 5 in section .text of /tmp/a.out
17619 (@value{GDBP}) info symbol 0x2aaaac2811cf
17620 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17625 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17626 Demangle @var{name}.
17627 If @var{language} is provided it is the name of the language to demangle
17628 @var{name} in. Otherwise @var{name} is demangled in the current language.
17630 The @samp{--} option specifies the end of options,
17631 and is useful when @var{name} begins with a dash.
17633 The parameter @code{demangle-style} specifies how to interpret the kind
17634 of mangling used. @xref{Print Settings}.
17637 @item whatis[/@var{flags}] [@var{arg}]
17638 Print the data type of @var{arg}, which can be either an expression
17639 or a name of a data type. With no argument, print the data type of
17640 @code{$}, the last value in the value history.
17642 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17643 is not actually evaluated, and any side-effecting operations (such as
17644 assignments or function calls) inside it do not take place.
17646 If @var{arg} is a variable or an expression, @code{whatis} prints its
17647 literal type as it is used in the source code. If the type was
17648 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17649 the data type underlying the @code{typedef}. If the type of the
17650 variable or the expression is a compound data type, such as
17651 @code{struct} or @code{class}, @code{whatis} never prints their
17652 fields or methods. It just prints the @code{struct}/@code{class}
17653 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17654 such a compound data type, use @code{ptype}.
17656 If @var{arg} is a type name that was defined using @code{typedef},
17657 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17658 Unrolling means that @code{whatis} will show the underlying type used
17659 in the @code{typedef} declaration of @var{arg}. However, if that
17660 underlying type is also a @code{typedef}, @code{whatis} will not
17663 For C code, the type names may also have the form @samp{class
17664 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17665 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17667 @var{flags} can be used to modify how the type is displayed.
17668 Available flags are:
17672 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17673 parameters and typedefs defined in a class when printing the class'
17674 members. The @code{/r} flag disables this.
17677 Do not print methods defined in the class.
17680 Print methods defined in the class. This is the default, but the flag
17681 exists in case you change the default with @command{set print type methods}.
17684 Do not print typedefs defined in the class. Note that this controls
17685 whether the typedef definition itself is printed, not whether typedef
17686 names are substituted when printing other types.
17689 Print typedefs defined in the class. This is the default, but the flag
17690 exists in case you change the default with @command{set print type typedefs}.
17693 Print the offsets and sizes of fields in a struct, similar to what the
17694 @command{pahole} tool does. This option implies the @code{/tm} flags.
17696 For example, given the following declarations:
17732 Issuing a @kbd{ptype /o struct tuv} command would print:
17735 (@value{GDBP}) ptype /o struct tuv
17736 /* offset | size */ type = struct tuv @{
17737 /* 0 | 4 */ int a1;
17738 /* XXX 4-byte hole */
17739 /* 8 | 8 */ char *a2;
17740 /* 16 | 4 */ int a3;
17742 /* total size (bytes): 24 */
17746 Notice the format of the first column of comments. There, you can
17747 find two parts separated by the @samp{|} character: the @emph{offset},
17748 which indicates where the field is located inside the struct, in
17749 bytes, and the @emph{size} of the field. Another interesting line is
17750 the marker of a @emph{hole} in the struct, indicating that it may be
17751 possible to pack the struct and make it use less space by reorganizing
17754 It is also possible to print offsets inside an union:
17757 (@value{GDBP}) ptype /o union qwe
17758 /* offset | size */ type = union qwe @{
17759 /* 24 */ struct tuv @{
17760 /* 0 | 4 */ int a1;
17761 /* XXX 4-byte hole */
17762 /* 8 | 8 */ char *a2;
17763 /* 16 | 4 */ int a3;
17765 /* total size (bytes): 24 */
17767 /* 40 */ struct xyz @{
17768 /* 0 | 4 */ int f1;
17769 /* 4 | 1 */ char f2;
17770 /* XXX 3-byte hole */
17771 /* 8 | 8 */ void *f3;
17772 /* 16 | 24 */ struct tuv @{
17773 /* 16 | 4 */ int a1;
17774 /* XXX 4-byte hole */
17775 /* 24 | 8 */ char *a2;
17776 /* 32 | 4 */ int a3;
17778 /* total size (bytes): 24 */
17781 /* total size (bytes): 40 */
17784 /* total size (bytes): 40 */
17788 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
17789 same space (because we are dealing with an union), the offset is not
17790 printed for them. However, you can still examine the offset of each
17791 of these structures' fields.
17793 Another useful scenario is printing the offsets of a struct containing
17797 (@value{GDBP}) ptype /o struct tyu
17798 /* offset | size */ type = struct tyu @{
17799 /* 0:31 | 4 */ int a1 : 1;
17800 /* 0:28 | 4 */ int a2 : 3;
17801 /* 0: 5 | 4 */ int a3 : 23;
17802 /* 3: 3 | 1 */ signed char a4 : 2;
17803 /* XXX 3-bit hole */
17804 /* XXX 4-byte hole */
17805 /* 8 | 8 */ int64_t a5;
17806 /* 16:27 | 4 */ int a6 : 5;
17807 /* 16:56 | 8 */ int64_t a7 : 3;
17809 /* total size (bytes): 24 */
17813 Note how the offset information is now extended to also include how
17814 many bits are left to be used in each bitfield.
17818 @item ptype[/@var{flags}] [@var{arg}]
17819 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17820 detailed description of the type, instead of just the name of the type.
17821 @xref{Expressions, ,Expressions}.
17823 Contrary to @code{whatis}, @code{ptype} always unrolls any
17824 @code{typedef}s in its argument declaration, whether the argument is
17825 a variable, expression, or a data type. This means that @code{ptype}
17826 of a variable or an expression will not print literally its type as
17827 present in the source code---use @code{whatis} for that. @code{typedef}s at
17828 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17829 fields, methods and inner @code{class typedef}s of @code{struct}s,
17830 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17832 For example, for this variable declaration:
17835 typedef double real_t;
17836 struct complex @{ real_t real; double imag; @};
17837 typedef struct complex complex_t;
17839 real_t *real_pointer_var;
17843 the two commands give this output:
17847 (@value{GDBP}) whatis var
17849 (@value{GDBP}) ptype var
17850 type = struct complex @{
17854 (@value{GDBP}) whatis complex_t
17855 type = struct complex
17856 (@value{GDBP}) whatis struct complex
17857 type = struct complex
17858 (@value{GDBP}) ptype struct complex
17859 type = struct complex @{
17863 (@value{GDBP}) whatis real_pointer_var
17865 (@value{GDBP}) ptype real_pointer_var
17871 As with @code{whatis}, using @code{ptype} without an argument refers to
17872 the type of @code{$}, the last value in the value history.
17874 @cindex incomplete type
17875 Sometimes, programs use opaque data types or incomplete specifications
17876 of complex data structure. If the debug information included in the
17877 program does not allow @value{GDBN} to display a full declaration of
17878 the data type, it will say @samp{<incomplete type>}. For example,
17879 given these declarations:
17883 struct foo *fooptr;
17887 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17890 (@value{GDBP}) ptype foo
17891 $1 = <incomplete type>
17895 ``Incomplete type'' is C terminology for data types that are not
17896 completely specified.
17898 @cindex unknown type
17899 Othertimes, information about a variable's type is completely absent
17900 from the debug information included in the program. This most often
17901 happens when the program or library where the variable is defined
17902 includes no debug information at all. @value{GDBN} knows the variable
17903 exists from inspecting the linker/loader symbol table (e.g., the ELF
17904 dynamic symbol table), but such symbols do not contain type
17905 information. Inspecting the type of a (global) variable for which
17906 @value{GDBN} has no type information shows:
17909 (@value{GDBP}) ptype var
17910 type = <data variable, no debug info>
17913 @xref{Variables, no debug info variables}, for how to print the values
17917 @item info types @var{regexp}
17919 Print a brief description of all types whose names match the regular
17920 expression @var{regexp} (or all types in your program, if you supply
17921 no argument). Each complete typename is matched as though it were a
17922 complete line; thus, @samp{i type value} gives information on all
17923 types in your program whose names include the string @code{value}, but
17924 @samp{i type ^value$} gives information only on types whose complete
17925 name is @code{value}.
17927 In programs using different languages, @value{GDBN} chooses the syntax
17928 to print the type description according to the
17929 @samp{set language} value: using @samp{set language auto}
17930 (see @ref{Automatically, ,Set Language Automatically}) means to use the
17931 language of the type, other values mean to use
17932 the manually specified language (see @ref{Manually, ,Set Language Manually}).
17934 This command differs from @code{ptype} in two ways: first, like
17935 @code{whatis}, it does not print a detailed description; second, it
17936 lists all source files and line numbers where a type is defined.
17938 @kindex info type-printers
17939 @item info type-printers
17940 Versions of @value{GDBN} that ship with Python scripting enabled may
17941 have ``type printers'' available. When using @command{ptype} or
17942 @command{whatis}, these printers are consulted when the name of a type
17943 is needed. @xref{Type Printing API}, for more information on writing
17946 @code{info type-printers} displays all the available type printers.
17948 @kindex enable type-printer
17949 @kindex disable type-printer
17950 @item enable type-printer @var{name}@dots{}
17951 @item disable type-printer @var{name}@dots{}
17952 These commands can be used to enable or disable type printers.
17955 @cindex local variables
17956 @item info scope @var{location}
17957 List all the variables local to a particular scope. This command
17958 accepts a @var{location} argument---a function name, a source line, or
17959 an address preceded by a @samp{*}, and prints all the variables local
17960 to the scope defined by that location. (@xref{Specify Location}, for
17961 details about supported forms of @var{location}.) For example:
17964 (@value{GDBP}) @b{info scope command_line_handler}
17965 Scope for command_line_handler:
17966 Symbol rl is an argument at stack/frame offset 8, length 4.
17967 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17968 Symbol linelength is in static storage at address 0x150a1c, length 4.
17969 Symbol p is a local variable in register $esi, length 4.
17970 Symbol p1 is a local variable in register $ebx, length 4.
17971 Symbol nline is a local variable in register $edx, length 4.
17972 Symbol repeat is a local variable at frame offset -8, length 4.
17976 This command is especially useful for determining what data to collect
17977 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17980 @kindex info source
17982 Show information about the current source file---that is, the source file for
17983 the function containing the current point of execution:
17986 the name of the source file, and the directory containing it,
17988 the directory it was compiled in,
17990 its length, in lines,
17992 which programming language it is written in,
17994 if the debug information provides it, the program that compiled the file
17995 (which may include, e.g., the compiler version and command line arguments),
17997 whether the executable includes debugging information for that file, and
17998 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
18000 whether the debugging information includes information about
18001 preprocessor macros.
18005 @kindex info sources
18007 Print the names of all source files in your program for which there is
18008 debugging information, organized into two lists: files whose symbols
18009 have already been read, and files whose symbols will be read when needed.
18011 @kindex info functions
18012 @item info functions [-q]
18013 Print the names and data types of all defined functions.
18014 Similarly to @samp{info types}, this command groups its output by source
18015 files and annotates each function definition with its source line
18018 In programs using different languages, @value{GDBN} chooses the syntax
18019 to print the function name and type according to the
18020 @samp{set language} value: using @samp{set language auto}
18021 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18022 language of the function, other values mean to use
18023 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18025 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18026 printing header information and messages explaining why no functions
18029 @item info functions [-q] [-t @var{type_regexp}] [@var{regexp}]
18030 Like @samp{info functions}, but only print the names and data types
18031 of the functions selected with the provided regexp(s).
18033 If @var{regexp} is provided, print only the functions whose names
18034 match the regular expression @var{regexp}.
18035 Thus, @samp{info fun step} finds all functions whose
18036 names include @code{step}; @samp{info fun ^step} finds those whose names
18037 start with @code{step}. If a function name contains characters that
18038 conflict with the regular expression language (e.g.@:
18039 @samp{operator*()}), they may be quoted with a backslash.
18041 If @var{type_regexp} is provided, print only the functions whose
18042 types, as printed by the @code{whatis} command, match
18043 the regular expression @var{type_regexp}.
18044 If @var{type_regexp} contains space(s), it should be enclosed in
18045 quote characters. If needed, use backslash to escape the meaning
18046 of special characters or quotes.
18047 Thus, @samp{info fun -t '^int ('} finds the functions that return
18048 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
18049 have an argument type containing int; @samp{info fun -t '^int (' ^step}
18050 finds the functions whose names start with @code{step} and that return
18053 If both @var{regexp} and @var{type_regexp} are provided, a function
18054 is printed only if its name matches @var{regexp} and its type matches
18058 @kindex info variables
18059 @item info variables [-q]
18060 Print the names and data types of all variables that are defined
18061 outside of functions (i.e.@: excluding local variables).
18062 The printed variables are grouped by source files and annotated with
18063 their respective source line numbers.
18065 In programs using different languages, @value{GDBN} chooses the syntax
18066 to print the variable name and type according to the
18067 @samp{set language} value: using @samp{set language auto}
18068 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18069 language of the variable, other values mean to use
18070 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18072 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18073 printing header information and messages explaining why no variables
18076 @item info variables [-q] [-t @var{type_regexp}] [@var{regexp}]
18077 Like @kbd{info variables}, but only print the variables selected
18078 with the provided regexp(s).
18080 If @var{regexp} is provided, print only the variables whose names
18081 match the regular expression @var{regexp}.
18083 If @var{type_regexp} is provided, print only the variables whose
18084 types, as printed by the @code{whatis} command, match
18085 the regular expression @var{type_regexp}.
18086 If @var{type_regexp} contains space(s), it should be enclosed in
18087 quote characters. If needed, use backslash to escape the meaning
18088 of special characters or quotes.
18090 If both @var{regexp} and @var{type_regexp} are provided, an argument
18091 is printed only if its name matches @var{regexp} and its type matches
18094 @kindex info classes
18095 @cindex Objective-C, classes and selectors
18097 @itemx info classes @var{regexp}
18098 Display all Objective-C classes in your program, or
18099 (with the @var{regexp} argument) all those matching a particular regular
18102 @kindex info selectors
18103 @item info selectors
18104 @itemx info selectors @var{regexp}
18105 Display all Objective-C selectors in your program, or
18106 (with the @var{regexp} argument) all those matching a particular regular
18110 This was never implemented.
18111 @kindex info methods
18113 @itemx info methods @var{regexp}
18114 The @code{info methods} command permits the user to examine all defined
18115 methods within C@t{++} program, or (with the @var{regexp} argument) a
18116 specific set of methods found in the various C@t{++} classes. Many
18117 C@t{++} classes provide a large number of methods. Thus, the output
18118 from the @code{ptype} command can be overwhelming and hard to use. The
18119 @code{info-methods} command filters the methods, printing only those
18120 which match the regular-expression @var{regexp}.
18123 @cindex opaque data types
18124 @kindex set opaque-type-resolution
18125 @item set opaque-type-resolution on
18126 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
18127 declared as a pointer to a @code{struct}, @code{class}, or
18128 @code{union}---for example, @code{struct MyType *}---that is used in one
18129 source file although the full declaration of @code{struct MyType} is in
18130 another source file. The default is on.
18132 A change in the setting of this subcommand will not take effect until
18133 the next time symbols for a file are loaded.
18135 @item set opaque-type-resolution off
18136 Tell @value{GDBN} not to resolve opaque types. In this case, the type
18137 is printed as follows:
18139 @{<no data fields>@}
18142 @kindex show opaque-type-resolution
18143 @item show opaque-type-resolution
18144 Show whether opaque types are resolved or not.
18146 @kindex set print symbol-loading
18147 @cindex print messages when symbols are loaded
18148 @item set print symbol-loading
18149 @itemx set print symbol-loading full
18150 @itemx set print symbol-loading brief
18151 @itemx set print symbol-loading off
18152 The @code{set print symbol-loading} command allows you to control the
18153 printing of messages when @value{GDBN} loads symbol information.
18154 By default a message is printed for the executable and one for each
18155 shared library, and normally this is what you want. However, when
18156 debugging apps with large numbers of shared libraries these messages
18158 When set to @code{brief} a message is printed for each executable,
18159 and when @value{GDBN} loads a collection of shared libraries at once
18160 it will only print one message regardless of the number of shared
18161 libraries. When set to @code{off} no messages are printed.
18163 @kindex show print symbol-loading
18164 @item show print symbol-loading
18165 Show whether messages will be printed when a @value{GDBN} command
18166 entered from the keyboard causes symbol information to be loaded.
18168 @kindex maint print symbols
18169 @cindex symbol dump
18170 @kindex maint print psymbols
18171 @cindex partial symbol dump
18172 @kindex maint print msymbols
18173 @cindex minimal symbol dump
18174 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
18175 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18176 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18177 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18178 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18179 Write a dump of debugging symbol data into the file @var{filename} or
18180 the terminal if @var{filename} is unspecified.
18181 If @code{-objfile @var{objfile}} is specified, only dump symbols for
18183 If @code{-pc @var{address}} is specified, only dump symbols for the file
18184 with code at that address. Note that @var{address} may be a symbol like
18186 If @code{-source @var{source}} is specified, only dump symbols for that
18189 These commands are used to debug the @value{GDBN} symbol-reading code.
18190 These commands do not modify internal @value{GDBN} state, therefore
18191 @samp{maint print symbols} will only print symbols for already expanded symbol
18193 You can use the command @code{info sources} to find out which files these are.
18194 If you use @samp{maint print psymbols} instead, the dump shows information
18195 about symbols that @value{GDBN} only knows partially---that is, symbols
18196 defined in files that @value{GDBN} has skimmed, but not yet read completely.
18197 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
18200 @xref{Files, ,Commands to Specify Files}, for a discussion of how
18201 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
18203 @kindex maint info symtabs
18204 @kindex maint info psymtabs
18205 @cindex listing @value{GDBN}'s internal symbol tables
18206 @cindex symbol tables, listing @value{GDBN}'s internal
18207 @cindex full symbol tables, listing @value{GDBN}'s internal
18208 @cindex partial symbol tables, listing @value{GDBN}'s internal
18209 @item maint info symtabs @r{[} @var{regexp} @r{]}
18210 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
18212 List the @code{struct symtab} or @code{struct partial_symtab}
18213 structures whose names match @var{regexp}. If @var{regexp} is not
18214 given, list them all. The output includes expressions which you can
18215 copy into a @value{GDBN} debugging this one to examine a particular
18216 structure in more detail. For example:
18219 (@value{GDBP}) maint info psymtabs dwarf2read
18220 @{ objfile /home/gnu/build/gdb/gdb
18221 ((struct objfile *) 0x82e69d0)
18222 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
18223 ((struct partial_symtab *) 0x8474b10)
18226 text addresses 0x814d3c8 -- 0x8158074
18227 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
18228 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
18229 dependencies (none)
18232 (@value{GDBP}) maint info symtabs
18236 We see that there is one partial symbol table whose filename contains
18237 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
18238 and we see that @value{GDBN} has not read in any symtabs yet at all.
18239 If we set a breakpoint on a function, that will cause @value{GDBN} to
18240 read the symtab for the compilation unit containing that function:
18243 (@value{GDBP}) break dwarf2_psymtab_to_symtab
18244 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
18246 (@value{GDBP}) maint info symtabs
18247 @{ objfile /home/gnu/build/gdb/gdb
18248 ((struct objfile *) 0x82e69d0)
18249 @{ symtab /home/gnu/src/gdb/dwarf2read.c
18250 ((struct symtab *) 0x86c1f38)
18253 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
18254 linetable ((struct linetable *) 0x8370fa0)
18255 debugformat DWARF 2
18261 @kindex maint info line-table
18262 @cindex listing @value{GDBN}'s internal line tables
18263 @cindex line tables, listing @value{GDBN}'s internal
18264 @item maint info line-table @r{[} @var{regexp} @r{]}
18266 List the @code{struct linetable} from all @code{struct symtab}
18267 instances whose name matches @var{regexp}. If @var{regexp} is not
18268 given, list the @code{struct linetable} from all @code{struct symtab}.
18270 @kindex maint set symbol-cache-size
18271 @cindex symbol cache size
18272 @item maint set symbol-cache-size @var{size}
18273 Set the size of the symbol cache to @var{size}.
18274 The default size is intended to be good enough for debugging
18275 most applications. This option exists to allow for experimenting
18276 with different sizes.
18278 @kindex maint show symbol-cache-size
18279 @item maint show symbol-cache-size
18280 Show the size of the symbol cache.
18282 @kindex maint print symbol-cache
18283 @cindex symbol cache, printing its contents
18284 @item maint print symbol-cache
18285 Print the contents of the symbol cache.
18286 This is useful when debugging symbol cache issues.
18288 @kindex maint print symbol-cache-statistics
18289 @cindex symbol cache, printing usage statistics
18290 @item maint print symbol-cache-statistics
18291 Print symbol cache usage statistics.
18292 This helps determine how well the cache is being utilized.
18294 @kindex maint flush-symbol-cache
18295 @cindex symbol cache, flushing
18296 @item maint flush-symbol-cache
18297 Flush the contents of the symbol cache, all entries are removed.
18298 This command is useful when debugging the symbol cache.
18299 It is also useful when collecting performance data.
18304 @chapter Altering Execution
18306 Once you think you have found an error in your program, you might want to
18307 find out for certain whether correcting the apparent error would lead to
18308 correct results in the rest of the run. You can find the answer by
18309 experiment, using the @value{GDBN} features for altering execution of the
18312 For example, you can store new values into variables or memory
18313 locations, give your program a signal, restart it at a different
18314 address, or even return prematurely from a function.
18317 * Assignment:: Assignment to variables
18318 * Jumping:: Continuing at a different address
18319 * Signaling:: Giving your program a signal
18320 * Returning:: Returning from a function
18321 * Calling:: Calling your program's functions
18322 * Patching:: Patching your program
18323 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
18327 @section Assignment to Variables
18330 @cindex setting variables
18331 To alter the value of a variable, evaluate an assignment expression.
18332 @xref{Expressions, ,Expressions}. For example,
18339 stores the value 4 into the variable @code{x}, and then prints the
18340 value of the assignment expression (which is 4).
18341 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
18342 information on operators in supported languages.
18344 @kindex set variable
18345 @cindex variables, setting
18346 If you are not interested in seeing the value of the assignment, use the
18347 @code{set} command instead of the @code{print} command. @code{set} is
18348 really the same as @code{print} except that the expression's value is
18349 not printed and is not put in the value history (@pxref{Value History,
18350 ,Value History}). The expression is evaluated only for its effects.
18352 If the beginning of the argument string of the @code{set} command
18353 appears identical to a @code{set} subcommand, use the @code{set
18354 variable} command instead of just @code{set}. This command is identical
18355 to @code{set} except for its lack of subcommands. For example, if your
18356 program has a variable @code{width}, you get an error if you try to set
18357 a new value with just @samp{set width=13}, because @value{GDBN} has the
18358 command @code{set width}:
18361 (@value{GDBP}) whatis width
18363 (@value{GDBP}) p width
18365 (@value{GDBP}) set width=47
18366 Invalid syntax in expression.
18370 The invalid expression, of course, is @samp{=47}. In
18371 order to actually set the program's variable @code{width}, use
18374 (@value{GDBP}) set var width=47
18377 Because the @code{set} command has many subcommands that can conflict
18378 with the names of program variables, it is a good idea to use the
18379 @code{set variable} command instead of just @code{set}. For example, if
18380 your program has a variable @code{g}, you run into problems if you try
18381 to set a new value with just @samp{set g=4}, because @value{GDBN} has
18382 the command @code{set gnutarget}, abbreviated @code{set g}:
18386 (@value{GDBP}) whatis g
18390 (@value{GDBP}) set g=4
18394 The program being debugged has been started already.
18395 Start it from the beginning? (y or n) y
18396 Starting program: /home/smith/cc_progs/a.out
18397 "/home/smith/cc_progs/a.out": can't open to read symbols:
18398 Invalid bfd target.
18399 (@value{GDBP}) show g
18400 The current BFD target is "=4".
18405 The program variable @code{g} did not change, and you silently set the
18406 @code{gnutarget} to an invalid value. In order to set the variable
18410 (@value{GDBP}) set var g=4
18413 @value{GDBN} allows more implicit conversions in assignments than C; you can
18414 freely store an integer value into a pointer variable or vice versa,
18415 and you can convert any structure to any other structure that is the
18416 same length or shorter.
18417 @comment FIXME: how do structs align/pad in these conversions?
18418 @comment /doc@cygnus.com 18dec1990
18420 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
18421 construct to generate a value of specified type at a specified address
18422 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
18423 to memory location @code{0x83040} as an integer (which implies a certain size
18424 and representation in memory), and
18427 set @{int@}0x83040 = 4
18431 stores the value 4 into that memory location.
18434 @section Continuing at a Different Address
18436 Ordinarily, when you continue your program, you do so at the place where
18437 it stopped, with the @code{continue} command. You can instead continue at
18438 an address of your own choosing, with the following commands:
18442 @kindex j @r{(@code{jump})}
18443 @item jump @var{location}
18444 @itemx j @var{location}
18445 Resume execution at @var{location}. Execution stops again immediately
18446 if there is a breakpoint there. @xref{Specify Location}, for a description
18447 of the different forms of @var{location}. It is common
18448 practice to use the @code{tbreak} command in conjunction with
18449 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
18451 The @code{jump} command does not change the current stack frame, or
18452 the stack pointer, or the contents of any memory location or any
18453 register other than the program counter. If @var{location} is in
18454 a different function from the one currently executing, the results may
18455 be bizarre if the two functions expect different patterns of arguments or
18456 of local variables. For this reason, the @code{jump} command requests
18457 confirmation if the specified line is not in the function currently
18458 executing. However, even bizarre results are predictable if you are
18459 well acquainted with the machine-language code of your program.
18462 On many systems, you can get much the same effect as the @code{jump}
18463 command by storing a new value into the register @code{$pc}. The
18464 difference is that this does not start your program running; it only
18465 changes the address of where it @emph{will} run when you continue. For
18473 makes the next @code{continue} command or stepping command execute at
18474 address @code{0x485}, rather than at the address where your program stopped.
18475 @xref{Continuing and Stepping, ,Continuing and Stepping}.
18477 The most common occasion to use the @code{jump} command is to back
18478 up---perhaps with more breakpoints set---over a portion of a program
18479 that has already executed, in order to examine its execution in more
18484 @section Giving your Program a Signal
18485 @cindex deliver a signal to a program
18489 @item signal @var{signal}
18490 Resume execution where your program is stopped, but immediately give it the
18491 signal @var{signal}. The @var{signal} can be the name or the number of a
18492 signal. For example, on many systems @code{signal 2} and @code{signal
18493 SIGINT} are both ways of sending an interrupt signal.
18495 Alternatively, if @var{signal} is zero, continue execution without
18496 giving a signal. This is useful when your program stopped on account of
18497 a signal and would ordinarily see the signal when resumed with the
18498 @code{continue} command; @samp{signal 0} causes it to resume without a
18501 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
18502 delivered to the currently selected thread, not the thread that last
18503 reported a stop. This includes the situation where a thread was
18504 stopped due to a signal. So if you want to continue execution
18505 suppressing the signal that stopped a thread, you should select that
18506 same thread before issuing the @samp{signal 0} command. If you issue
18507 the @samp{signal 0} command with another thread as the selected one,
18508 @value{GDBN} detects that and asks for confirmation.
18510 Invoking the @code{signal} command is not the same as invoking the
18511 @code{kill} utility from the shell. Sending a signal with @code{kill}
18512 causes @value{GDBN} to decide what to do with the signal depending on
18513 the signal handling tables (@pxref{Signals}). The @code{signal} command
18514 passes the signal directly to your program.
18516 @code{signal} does not repeat when you press @key{RET} a second time
18517 after executing the command.
18519 @kindex queue-signal
18520 @item queue-signal @var{signal}
18521 Queue @var{signal} to be delivered immediately to the current thread
18522 when execution of the thread resumes. The @var{signal} can be the name or
18523 the number of a signal. For example, on many systems @code{signal 2} and
18524 @code{signal SIGINT} are both ways of sending an interrupt signal.
18525 The handling of the signal must be set to pass the signal to the program,
18526 otherwise @value{GDBN} will report an error.
18527 You can control the handling of signals from @value{GDBN} with the
18528 @code{handle} command (@pxref{Signals}).
18530 Alternatively, if @var{signal} is zero, any currently queued signal
18531 for the current thread is discarded and when execution resumes no signal
18532 will be delivered. This is useful when your program stopped on account
18533 of a signal and would ordinarily see the signal when resumed with the
18534 @code{continue} command.
18536 This command differs from the @code{signal} command in that the signal
18537 is just queued, execution is not resumed. And @code{queue-signal} cannot
18538 be used to pass a signal whose handling state has been set to @code{nopass}
18543 @xref{stepping into signal handlers}, for information on how stepping
18544 commands behave when the thread has a signal queued.
18547 @section Returning from a Function
18550 @cindex returning from a function
18553 @itemx return @var{expression}
18554 You can cancel execution of a function call with the @code{return}
18555 command. If you give an
18556 @var{expression} argument, its value is used as the function's return
18560 When you use @code{return}, @value{GDBN} discards the selected stack frame
18561 (and all frames within it). You can think of this as making the
18562 discarded frame return prematurely. If you wish to specify a value to
18563 be returned, give that value as the argument to @code{return}.
18565 This pops the selected stack frame (@pxref{Selection, ,Selecting a
18566 Frame}), and any other frames inside of it, leaving its caller as the
18567 innermost remaining frame. That frame becomes selected. The
18568 specified value is stored in the registers used for returning values
18571 The @code{return} command does not resume execution; it leaves the
18572 program stopped in the state that would exist if the function had just
18573 returned. In contrast, the @code{finish} command (@pxref{Continuing
18574 and Stepping, ,Continuing and Stepping}) resumes execution until the
18575 selected stack frame returns naturally.
18577 @value{GDBN} needs to know how the @var{expression} argument should be set for
18578 the inferior. The concrete registers assignment depends on the OS ABI and the
18579 type being returned by the selected stack frame. For example it is common for
18580 OS ABI to return floating point values in FPU registers while integer values in
18581 CPU registers. Still some ABIs return even floating point values in CPU
18582 registers. Larger integer widths (such as @code{long long int}) also have
18583 specific placement rules. @value{GDBN} already knows the OS ABI from its
18584 current target so it needs to find out also the type being returned to make the
18585 assignment into the right register(s).
18587 Normally, the selected stack frame has debug info. @value{GDBN} will always
18588 use the debug info instead of the implicit type of @var{expression} when the
18589 debug info is available. For example, if you type @kbd{return -1}, and the
18590 function in the current stack frame is declared to return a @code{long long
18591 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
18592 into a @code{long long int}:
18595 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
18597 (@value{GDBP}) return -1
18598 Make func return now? (y or n) y
18599 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
18600 43 printf ("result=%lld\n", func ());
18604 However, if the selected stack frame does not have a debug info, e.g., if the
18605 function was compiled without debug info, @value{GDBN} has to find out the type
18606 to return from user. Specifying a different type by mistake may set the value
18607 in different inferior registers than the caller code expects. For example,
18608 typing @kbd{return -1} with its implicit type @code{int} would set only a part
18609 of a @code{long long int} result for a debug info less function (on 32-bit
18610 architectures). Therefore the user is required to specify the return type by
18611 an appropriate cast explicitly:
18614 Breakpoint 2, 0x0040050b in func ()
18615 (@value{GDBP}) return -1
18616 Return value type not available for selected stack frame.
18617 Please use an explicit cast of the value to return.
18618 (@value{GDBP}) return (long long int) -1
18619 Make selected stack frame return now? (y or n) y
18620 #0 0x00400526 in main ()
18625 @section Calling Program Functions
18628 @cindex calling functions
18629 @cindex inferior functions, calling
18630 @item print @var{expr}
18631 Evaluate the expression @var{expr} and display the resulting value.
18632 The expression may include calls to functions in the program being
18636 @item call @var{expr}
18637 Evaluate the expression @var{expr} without displaying @code{void}
18640 You can use this variant of the @code{print} command if you want to
18641 execute a function from your program that does not return anything
18642 (a.k.a.@: @dfn{a void function}), but without cluttering the output
18643 with @code{void} returned values that @value{GDBN} will otherwise
18644 print. If the result is not void, it is printed and saved in the
18648 It is possible for the function you call via the @code{print} or
18649 @code{call} command to generate a signal (e.g., if there's a bug in
18650 the function, or if you passed it incorrect arguments). What happens
18651 in that case is controlled by the @code{set unwindonsignal} command.
18653 Similarly, with a C@t{++} program it is possible for the function you
18654 call via the @code{print} or @code{call} command to generate an
18655 exception that is not handled due to the constraints of the dummy
18656 frame. In this case, any exception that is raised in the frame, but has
18657 an out-of-frame exception handler will not be found. GDB builds a
18658 dummy-frame for the inferior function call, and the unwinder cannot
18659 seek for exception handlers outside of this dummy-frame. What happens
18660 in that case is controlled by the
18661 @code{set unwind-on-terminating-exception} command.
18664 @item set unwindonsignal
18665 @kindex set unwindonsignal
18666 @cindex unwind stack in called functions
18667 @cindex call dummy stack unwinding
18668 Set unwinding of the stack if a signal is received while in a function
18669 that @value{GDBN} called in the program being debugged. If set to on,
18670 @value{GDBN} unwinds the stack it created for the call and restores
18671 the context to what it was before the call. If set to off (the
18672 default), @value{GDBN} stops in the frame where the signal was
18675 @item show unwindonsignal
18676 @kindex show unwindonsignal
18677 Show the current setting of stack unwinding in the functions called by
18680 @item set unwind-on-terminating-exception
18681 @kindex set unwind-on-terminating-exception
18682 @cindex unwind stack in called functions with unhandled exceptions
18683 @cindex call dummy stack unwinding on unhandled exception.
18684 Set unwinding of the stack if a C@t{++} exception is raised, but left
18685 unhandled while in a function that @value{GDBN} called in the program being
18686 debugged. If set to on (the default), @value{GDBN} unwinds the stack
18687 it created for the call and restores the context to what it was before
18688 the call. If set to off, @value{GDBN} the exception is delivered to
18689 the default C@t{++} exception handler and the inferior terminated.
18691 @item show unwind-on-terminating-exception
18692 @kindex show unwind-on-terminating-exception
18693 Show the current setting of stack unwinding in the functions called by
18696 @item set may-call-functions
18697 @kindex set may-call-functions
18698 @cindex disabling calling functions in the program
18699 @cindex calling functions in the program, disabling
18700 Set permission to call functions in the program.
18701 This controls whether @value{GDBN} will attempt to call functions in
18702 the program, such as with expressions in the @code{print} command. It
18703 defaults to @code{on}.
18705 To call a function in the program, @value{GDBN} has to temporarily
18706 modify the state of the inferior. This has potentially undesired side
18707 effects. Also, having @value{GDBN} call nested functions is likely to
18708 be erroneous and may even crash the program being debugged. You can
18709 avoid such hazards by forbidding @value{GDBN} from calling functions
18710 in the program being debugged. If calling functions in the program
18711 is forbidden, GDB will throw an error when a command (such as printing
18712 an expression) starts a function call in the program.
18714 @item show may-call-functions
18715 @kindex show may-call-functions
18716 Show permission to call functions in the program.
18720 @subsection Calling functions with no debug info
18722 @cindex no debug info functions
18723 Sometimes, a function you wish to call is missing debug information.
18724 In such case, @value{GDBN} does not know the type of the function,
18725 including the types of the function's parameters. To avoid calling
18726 the inferior function incorrectly, which could result in the called
18727 function functioning erroneously and even crash, @value{GDBN} refuses
18728 to call the function unless you tell it the type of the function.
18730 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18731 to do that. The simplest is to cast the call to the function's
18732 declared return type. For example:
18735 (@value{GDBP}) p getenv ("PATH")
18736 'getenv' has unknown return type; cast the call to its declared return type
18737 (@value{GDBP}) p (char *) getenv ("PATH")
18738 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18741 Casting the return type of a no-debug function is equivalent to
18742 casting the function to a pointer to a prototyped function that has a
18743 prototype that matches the types of the passed-in arguments, and
18744 calling that. I.e., the call above is equivalent to:
18747 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18751 and given this prototyped C or C++ function with float parameters:
18754 float multiply (float v1, float v2) @{ return v1 * v2; @}
18758 these calls are equivalent:
18761 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18762 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18765 If the function you wish to call is declared as unprototyped (i.e.@:
18766 old K&R style), you must use the cast-to-function-pointer syntax, so
18767 that @value{GDBN} knows that it needs to apply default argument
18768 promotions (promote float arguments to double). @xref{ABI, float
18769 promotion}. For example, given this unprototyped C function with
18770 float parameters, and no debug info:
18774 multiply_noproto (v1, v2)
18782 you call it like this:
18785 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18789 @section Patching Programs
18791 @cindex patching binaries
18792 @cindex writing into executables
18793 @cindex writing into corefiles
18795 By default, @value{GDBN} opens the file containing your program's
18796 executable code (or the corefile) read-only. This prevents accidental
18797 alterations to machine code; but it also prevents you from intentionally
18798 patching your program's binary.
18800 If you'd like to be able to patch the binary, you can specify that
18801 explicitly with the @code{set write} command. For example, you might
18802 want to turn on internal debugging flags, or even to make emergency
18808 @itemx set write off
18809 If you specify @samp{set write on}, @value{GDBN} opens executable and
18810 core files for both reading and writing; if you specify @kbd{set write
18811 off} (the default), @value{GDBN} opens them read-only.
18813 If you have already loaded a file, you must load it again (using the
18814 @code{exec-file} or @code{core-file} command) after changing @code{set
18815 write}, for your new setting to take effect.
18819 Display whether executable files and core files are opened for writing
18820 as well as reading.
18823 @node Compiling and Injecting Code
18824 @section Compiling and injecting code in @value{GDBN}
18825 @cindex injecting code
18826 @cindex writing into executables
18827 @cindex compiling code
18829 @value{GDBN} supports on-demand compilation and code injection into
18830 programs running under @value{GDBN}. GCC 5.0 or higher built with
18831 @file{libcc1.so} must be installed for this functionality to be enabled.
18832 This functionality is implemented with the following commands.
18835 @kindex compile code
18836 @item compile code @var{source-code}
18837 @itemx compile code -raw @var{--} @var{source-code}
18838 Compile @var{source-code} with the compiler language found as the current
18839 language in @value{GDBN} (@pxref{Languages}). If compilation and
18840 injection is not supported with the current language specified in
18841 @value{GDBN}, or the compiler does not support this feature, an error
18842 message will be printed. If @var{source-code} compiles and links
18843 successfully, @value{GDBN} will load the object-code emitted,
18844 and execute it within the context of the currently selected inferior.
18845 It is important to note that the compiled code is executed immediately.
18846 After execution, the compiled code is removed from @value{GDBN} and any
18847 new types or variables you have defined will be deleted.
18849 The command allows you to specify @var{source-code} in two ways.
18850 The simplest method is to provide a single line of code to the command.
18854 compile code printf ("hello world\n");
18857 If you specify options on the command line as well as source code, they
18858 may conflict. The @samp{--} delimiter can be used to separate options
18859 from actual source code. E.g.:
18862 compile code -r -- printf ("hello world\n");
18865 Alternatively you can enter source code as multiple lines of text. To
18866 enter this mode, invoke the @samp{compile code} command without any text
18867 following the command. This will start the multiple-line editor and
18868 allow you to type as many lines of source code as required. When you
18869 have completed typing, enter @samp{end} on its own line to exit the
18874 >printf ("hello\n");
18875 >printf ("world\n");
18879 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18880 provided @var{source-code} in a callable scope. In this case, you must
18881 specify the entry point of the code by defining a function named
18882 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18883 inferior. Using @samp{-raw} option may be needed for example when
18884 @var{source-code} requires @samp{#include} lines which may conflict with
18885 inferior symbols otherwise.
18887 @kindex compile file
18888 @item compile file @var{filename}
18889 @itemx compile file -raw @var{filename}
18890 Like @code{compile code}, but take the source code from @var{filename}.
18893 compile file /home/user/example.c
18898 @item compile print @var{expr}
18899 @itemx compile print /@var{f} @var{expr}
18900 Compile and execute @var{expr} with the compiler language found as the
18901 current language in @value{GDBN} (@pxref{Languages}). By default the
18902 value of @var{expr} is printed in a format appropriate to its data type;
18903 you can choose a different format by specifying @samp{/@var{f}}, where
18904 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18907 @item compile print
18908 @itemx compile print /@var{f}
18909 @cindex reprint the last value
18910 Alternatively you can enter the expression (source code producing it) as
18911 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18912 command without any text following the command. This will start the
18913 multiple-line editor.
18917 The process of compiling and injecting the code can be inspected using:
18920 @anchor{set debug compile}
18921 @item set debug compile
18922 @cindex compile command debugging info
18923 Turns on or off display of @value{GDBN} process of compiling and
18924 injecting the code. The default is off.
18926 @item show debug compile
18927 Displays the current state of displaying @value{GDBN} process of
18928 compiling and injecting the code.
18930 @anchor{set debug compile-cplus-types}
18931 @item set debug compile-cplus-types
18932 @cindex compile C@t{++} type conversion
18933 Turns on or off the display of C@t{++} type conversion debugging information.
18934 The default is off.
18936 @item show debug compile-cplus-types
18937 Displays the current state of displaying debugging information for
18938 C@t{++} type conversion.
18941 @subsection Compilation options for the @code{compile} command
18943 @value{GDBN} needs to specify the right compilation options for the code
18944 to be injected, in part to make its ABI compatible with the inferior
18945 and in part to make the injected code compatible with @value{GDBN}'s
18949 The options used, in increasing precedence:
18952 @item target architecture and OS options (@code{gdbarch})
18953 These options depend on target processor type and target operating
18954 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18955 (@code{-m64}) compilation option.
18957 @item compilation options recorded in the target
18958 @value{NGCC} (since version 4.7) stores the options used for compilation
18959 into @code{DW_AT_producer} part of DWARF debugging information according
18960 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18961 explicitly specify @code{-g} during inferior compilation otherwise
18962 @value{NGCC} produces no DWARF. This feature is only relevant for
18963 platforms where @code{-g} produces DWARF by default, otherwise one may
18964 try to enforce DWARF by using @code{-gdwarf-4}.
18966 @item compilation options set by @code{set compile-args}
18970 You can override compilation options using the following command:
18973 @item set compile-args
18974 @cindex compile command options override
18975 Set compilation options used for compiling and injecting code with the
18976 @code{compile} commands. These options override any conflicting ones
18977 from the target architecture and/or options stored during inferior
18980 @item show compile-args
18981 Displays the current state of compilation options override.
18982 This does not show all the options actually used during compilation,
18983 use @ref{set debug compile} for that.
18986 @subsection Caveats when using the @code{compile} command
18988 There are a few caveats to keep in mind when using the @code{compile}
18989 command. As the caveats are different per language, the table below
18990 highlights specific issues on a per language basis.
18993 @item C code examples and caveats
18994 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18995 attempt to compile the source code with a @samp{C} compiler. The source
18996 code provided to the @code{compile} command will have much the same
18997 access to variables and types as it normally would if it were part of
18998 the program currently being debugged in @value{GDBN}.
19000 Below is a sample program that forms the basis of the examples that
19001 follow. This program has been compiled and loaded into @value{GDBN},
19002 much like any other normal debugging session.
19005 void function1 (void)
19008 printf ("function 1\n");
19011 void function2 (void)
19026 For the purposes of the examples in this section, the program above has
19027 been compiled, loaded into @value{GDBN}, stopped at the function
19028 @code{main}, and @value{GDBN} is awaiting input from the user.
19030 To access variables and types for any program in @value{GDBN}, the
19031 program must be compiled and packaged with debug information. The
19032 @code{compile} command is not an exception to this rule. Without debug
19033 information, you can still use the @code{compile} command, but you will
19034 be very limited in what variables and types you can access.
19036 So with that in mind, the example above has been compiled with debug
19037 information enabled. The @code{compile} command will have access to
19038 all variables and types (except those that may have been optimized
19039 out). Currently, as @value{GDBN} has stopped the program in the
19040 @code{main} function, the @code{compile} command would have access to
19041 the variable @code{k}. You could invoke the @code{compile} command
19042 and type some source code to set the value of @code{k}. You can also
19043 read it, or do anything with that variable you would normally do in
19044 @code{C}. Be aware that changes to inferior variables in the
19045 @code{compile} command are persistent. In the following example:
19048 compile code k = 3;
19052 the variable @code{k} is now 3. It will retain that value until
19053 something else in the example program changes it, or another
19054 @code{compile} command changes it.
19056 Normal scope and access rules apply to source code compiled and
19057 injected by the @code{compile} command. In the example, the variables
19058 @code{j} and @code{k} are not accessible yet, because the program is
19059 currently stopped in the @code{main} function, where these variables
19060 are not in scope. Therefore, the following command
19063 compile code j = 3;
19067 will result in a compilation error message.
19069 Once the program is continued, execution will bring these variables in
19070 scope, and they will become accessible; then the code you specify via
19071 the @code{compile} command will be able to access them.
19073 You can create variables and types with the @code{compile} command as
19074 part of your source code. Variables and types that are created as part
19075 of the @code{compile} command are not visible to the rest of the program for
19076 the duration of its run. This example is valid:
19079 compile code int ff = 5; printf ("ff is %d\n", ff);
19082 However, if you were to type the following into @value{GDBN} after that
19083 command has completed:
19086 compile code printf ("ff is %d\n'', ff);
19090 a compiler error would be raised as the variable @code{ff} no longer
19091 exists. Object code generated and injected by the @code{compile}
19092 command is removed when its execution ends. Caution is advised
19093 when assigning to program variables values of variables created by the
19094 code submitted to the @code{compile} command. This example is valid:
19097 compile code int ff = 5; k = ff;
19100 The value of the variable @code{ff} is assigned to @code{k}. The variable
19101 @code{k} does not require the existence of @code{ff} to maintain the value
19102 it has been assigned. However, pointers require particular care in
19103 assignment. If the source code compiled with the @code{compile} command
19104 changed the address of a pointer in the example program, perhaps to a
19105 variable created in the @code{compile} command, that pointer would point
19106 to an invalid location when the command exits. The following example
19107 would likely cause issues with your debugged program:
19110 compile code int ff = 5; p = &ff;
19113 In this example, @code{p} would point to @code{ff} when the
19114 @code{compile} command is executing the source code provided to it.
19115 However, as variables in the (example) program persist with their
19116 assigned values, the variable @code{p} would point to an invalid
19117 location when the command exists. A general rule should be followed
19118 in that you should either assign @code{NULL} to any assigned pointers,
19119 or restore a valid location to the pointer before the command exits.
19121 Similar caution must be exercised with any structs, unions, and typedefs
19122 defined in @code{compile} command. Types defined in the @code{compile}
19123 command will no longer be available in the next @code{compile} command.
19124 Therefore, if you cast a variable to a type defined in the
19125 @code{compile} command, care must be taken to ensure that any future
19126 need to resolve the type can be achieved.
19129 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
19130 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
19131 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
19132 Compilation failed.
19133 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
19137 Variables that have been optimized away by the compiler are not
19138 accessible to the code submitted to the @code{compile} command.
19139 Access to those variables will generate a compiler error which @value{GDBN}
19140 will print to the console.
19143 @subsection Compiler search for the @code{compile} command
19145 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
19146 which may not be obvious for remote targets of different architecture
19147 than where @value{GDBN} is running. Environment variable @code{PATH} on
19148 @value{GDBN} host is searched for @value{NGCC} binary matching the
19149 target architecture and operating system. This search can be overriden
19150 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
19151 taken from shell that executed @value{GDBN}, it is not the value set by
19152 @value{GDBN} command @code{set environment}). @xref{Environment}.
19155 Specifically @code{PATH} is searched for binaries matching regular expression
19156 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
19157 debugged. @var{arch} is processor name --- multiarch is supported, so for
19158 example both @code{i386} and @code{x86_64} targets look for pattern
19159 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
19160 for pattern @code{s390x?}. @var{os} is currently supported only for
19161 pattern @code{linux(-gnu)?}.
19163 On Posix hosts the compiler driver @value{GDBN} needs to find also
19164 shared library @file{libcc1.so} from the compiler. It is searched in
19165 default shared library search path (overridable with usual environment
19166 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
19167 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
19168 according to the installation of the found compiler --- as possibly
19169 specified by the @code{set compile-gcc} command.
19172 @item set compile-gcc
19173 @cindex compile command driver filename override
19174 Set compilation command used for compiling and injecting code with the
19175 @code{compile} commands. If this option is not set (it is set to
19176 an empty string), the search described above will occur --- that is the
19179 @item show compile-gcc
19180 Displays the current compile command @value{NGCC} driver filename.
19181 If set, it is the main command @command{gcc}, found usually for example
19182 under name @file{x86_64-linux-gnu-gcc}.
19186 @chapter @value{GDBN} Files
19188 @value{GDBN} needs to know the file name of the program to be debugged,
19189 both in order to read its symbol table and in order to start your
19190 program. To debug a core dump of a previous run, you must also tell
19191 @value{GDBN} the name of the core dump file.
19194 * Files:: Commands to specify files
19195 * File Caching:: Information about @value{GDBN}'s file caching
19196 * Separate Debug Files:: Debugging information in separate files
19197 * MiniDebugInfo:: Debugging information in a special section
19198 * Index Files:: Index files speed up GDB
19199 * Symbol Errors:: Errors reading symbol files
19200 * Data Files:: GDB data files
19204 @section Commands to Specify Files
19206 @cindex symbol table
19207 @cindex core dump file
19209 You may want to specify executable and core dump file names. The usual
19210 way to do this is at start-up time, using the arguments to
19211 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
19212 Out of @value{GDBN}}).
19214 Occasionally it is necessary to change to a different file during a
19215 @value{GDBN} session. Or you may run @value{GDBN} and forget to
19216 specify a file you want to use. Or you are debugging a remote target
19217 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
19218 Program}). In these situations the @value{GDBN} commands to specify
19219 new files are useful.
19222 @cindex executable file
19224 @item file @var{filename}
19225 Use @var{filename} as the program to be debugged. It is read for its
19226 symbols and for the contents of pure memory. It is also the program
19227 executed when you use the @code{run} command. If you do not specify a
19228 directory and the file is not found in the @value{GDBN} working directory,
19229 @value{GDBN} uses the environment variable @code{PATH} as a list of
19230 directories to search, just as the shell does when looking for a program
19231 to run. You can change the value of this variable, for both @value{GDBN}
19232 and your program, using the @code{path} command.
19234 @cindex unlinked object files
19235 @cindex patching object files
19236 You can load unlinked object @file{.o} files into @value{GDBN} using
19237 the @code{file} command. You will not be able to ``run'' an object
19238 file, but you can disassemble functions and inspect variables. Also,
19239 if the underlying BFD functionality supports it, you could use
19240 @kbd{gdb -write} to patch object files using this technique. Note
19241 that @value{GDBN} can neither interpret nor modify relocations in this
19242 case, so branches and some initialized variables will appear to go to
19243 the wrong place. But this feature is still handy from time to time.
19246 @code{file} with no argument makes @value{GDBN} discard any information it
19247 has on both executable file and the symbol table.
19250 @item exec-file @r{[} @var{filename} @r{]}
19251 Specify that the program to be run (but not the symbol table) is found
19252 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
19253 if necessary to locate your program. Omitting @var{filename} means to
19254 discard information on the executable file.
19256 @kindex symbol-file
19257 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
19258 Read symbol table information from file @var{filename}. @code{PATH} is
19259 searched when necessary. Use the @code{file} command to get both symbol
19260 table and program to run from the same file.
19262 If an optional @var{offset} is specified, it is added to the start
19263 address of each section in the symbol file. This is useful if the
19264 program is relocated at runtime, such as the Linux kernel with kASLR
19267 @code{symbol-file} with no argument clears out @value{GDBN} information on your
19268 program's symbol table.
19270 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
19271 some breakpoints and auto-display expressions. This is because they may
19272 contain pointers to the internal data recording symbols and data types,
19273 which are part of the old symbol table data being discarded inside
19276 @code{symbol-file} does not repeat if you press @key{RET} again after
19279 When @value{GDBN} is configured for a particular environment, it
19280 understands debugging information in whatever format is the standard
19281 generated for that environment; you may use either a @sc{gnu} compiler, or
19282 other compilers that adhere to the local conventions.
19283 Best results are usually obtained from @sc{gnu} compilers; for example,
19284 using @code{@value{NGCC}} you can generate debugging information for
19287 For most kinds of object files, with the exception of old SVR3 systems
19288 using COFF, the @code{symbol-file} command does not normally read the
19289 symbol table in full right away. Instead, it scans the symbol table
19290 quickly to find which source files and which symbols are present. The
19291 details are read later, one source file at a time, as they are needed.
19293 The purpose of this two-stage reading strategy is to make @value{GDBN}
19294 start up faster. For the most part, it is invisible except for
19295 occasional pauses while the symbol table details for a particular source
19296 file are being read. (The @code{set verbose} command can turn these
19297 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
19298 Warnings and Messages}.)
19300 We have not implemented the two-stage strategy for COFF yet. When the
19301 symbol table is stored in COFF format, @code{symbol-file} reads the
19302 symbol table data in full right away. Note that ``stabs-in-COFF''
19303 still does the two-stage strategy, since the debug info is actually
19307 @cindex reading symbols immediately
19308 @cindex symbols, reading immediately
19309 @item symbol-file @r{[} -readnow @r{]} @var{filename}
19310 @itemx file @r{[} -readnow @r{]} @var{filename}
19311 You can override the @value{GDBN} two-stage strategy for reading symbol
19312 tables by using the @samp{-readnow} option with any of the commands that
19313 load symbol table information, if you want to be sure @value{GDBN} has the
19314 entire symbol table available.
19316 @cindex @code{-readnever}, option for symbol-file command
19317 @cindex never read symbols
19318 @cindex symbols, never read
19319 @item symbol-file @r{[} -readnever @r{]} @var{filename}
19320 @itemx file @r{[} -readnever @r{]} @var{filename}
19321 You can instruct @value{GDBN} to never read the symbolic information
19322 contained in @var{filename} by using the @samp{-readnever} option.
19323 @xref{--readnever}.
19325 @c FIXME: for now no mention of directories, since this seems to be in
19326 @c flux. 13mar1992 status is that in theory GDB would look either in
19327 @c current dir or in same dir as myprog; but issues like competing
19328 @c GDB's, or clutter in system dirs, mean that in practice right now
19329 @c only current dir is used. FFish says maybe a special GDB hierarchy
19330 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
19334 @item core-file @r{[}@var{filename}@r{]}
19336 Specify the whereabouts of a core dump file to be used as the ``contents
19337 of memory''. Traditionally, core files contain only some parts of the
19338 address space of the process that generated them; @value{GDBN} can access the
19339 executable file itself for other parts.
19341 @code{core-file} with no argument specifies that no core file is
19344 Note that the core file is ignored when your program is actually running
19345 under @value{GDBN}. So, if you have been running your program and you
19346 wish to debug a core file instead, you must kill the subprocess in which
19347 the program is running. To do this, use the @code{kill} command
19348 (@pxref{Kill Process, ,Killing the Child Process}).
19350 @kindex add-symbol-file
19351 @cindex dynamic linking
19352 @item add-symbol-file @var{filename} @r{[} -readnow @r{|} -readnever @r{]} @r{[} -o @var{offset} @r{]} @r{[} @var{textaddress} @r{]} @r{[} -s @var{section} @var{address} @dots{} @r{]}
19353 The @code{add-symbol-file} command reads additional symbol table
19354 information from the file @var{filename}. You would use this command
19355 when @var{filename} has been dynamically loaded (by some other means)
19356 into the program that is running. The @var{textaddress} parameter gives
19357 the memory address at which the file's text section has been loaded.
19358 You can additionally specify the base address of other sections using
19359 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
19360 If a section is omitted, @value{GDBN} will use its default addresses
19361 as found in @var{filename}. Any @var{address} or @var{textaddress}
19362 can be given as an expression.
19364 If an optional @var{offset} is specified, it is added to the start
19365 address of each section, except those for which the address was
19366 specified explicitly.
19368 The symbol table of the file @var{filename} is added to the symbol table
19369 originally read with the @code{symbol-file} command. You can use the
19370 @code{add-symbol-file} command any number of times; the new symbol data
19371 thus read is kept in addition to the old.
19373 Changes can be reverted using the command @code{remove-symbol-file}.
19375 @cindex relocatable object files, reading symbols from
19376 @cindex object files, relocatable, reading symbols from
19377 @cindex reading symbols from relocatable object files
19378 @cindex symbols, reading from relocatable object files
19379 @cindex @file{.o} files, reading symbols from
19380 Although @var{filename} is typically a shared library file, an
19381 executable file, or some other object file which has been fully
19382 relocated for loading into a process, you can also load symbolic
19383 information from relocatable @file{.o} files, as long as:
19387 the file's symbolic information refers only to linker symbols defined in
19388 that file, not to symbols defined by other object files,
19390 every section the file's symbolic information refers to has actually
19391 been loaded into the inferior, as it appears in the file, and
19393 you can determine the address at which every section was loaded, and
19394 provide these to the @code{add-symbol-file} command.
19398 Some embedded operating systems, like Sun Chorus and VxWorks, can load
19399 relocatable files into an already running program; such systems
19400 typically make the requirements above easy to meet. However, it's
19401 important to recognize that many native systems use complex link
19402 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
19403 assembly, for example) that make the requirements difficult to meet. In
19404 general, one cannot assume that using @code{add-symbol-file} to read a
19405 relocatable object file's symbolic information will have the same effect
19406 as linking the relocatable object file into the program in the normal
19409 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
19411 @kindex remove-symbol-file
19412 @item remove-symbol-file @var{filename}
19413 @item remove-symbol-file -a @var{address}
19414 Remove a symbol file added via the @code{add-symbol-file} command. The
19415 file to remove can be identified by its @var{filename} or by an @var{address}
19416 that lies within the boundaries of this symbol file in memory. Example:
19419 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
19420 add symbol table from file "/home/user/gdb/mylib.so" at
19421 .text_addr = 0x7ffff7ff9480
19423 Reading symbols from /home/user/gdb/mylib.so...done.
19424 (gdb) remove-symbol-file -a 0x7ffff7ff9480
19425 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
19430 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
19432 @kindex add-symbol-file-from-memory
19433 @cindex @code{syscall DSO}
19434 @cindex load symbols from memory
19435 @item add-symbol-file-from-memory @var{address}
19436 Load symbols from the given @var{address} in a dynamically loaded
19437 object file whose image is mapped directly into the inferior's memory.
19438 For example, the Linux kernel maps a @code{syscall DSO} into each
19439 process's address space; this DSO provides kernel-specific code for
19440 some system calls. The argument can be any expression whose
19441 evaluation yields the address of the file's shared object file header.
19442 For this command to work, you must have used @code{symbol-file} or
19443 @code{exec-file} commands in advance.
19446 @item section @var{section} @var{addr}
19447 The @code{section} command changes the base address of the named
19448 @var{section} of the exec file to @var{addr}. This can be used if the
19449 exec file does not contain section addresses, (such as in the
19450 @code{a.out} format), or when the addresses specified in the file
19451 itself are wrong. Each section must be changed separately. The
19452 @code{info files} command, described below, lists all the sections and
19456 @kindex info target
19459 @code{info files} and @code{info target} are synonymous; both print the
19460 current target (@pxref{Targets, ,Specifying a Debugging Target}),
19461 including the names of the executable and core dump files currently in
19462 use by @value{GDBN}, and the files from which symbols were loaded. The
19463 command @code{help target} lists all possible targets rather than
19466 @kindex maint info sections
19467 @item maint info sections
19468 Another command that can give you extra information about program sections
19469 is @code{maint info sections}. In addition to the section information
19470 displayed by @code{info files}, this command displays the flags and file
19471 offset of each section in the executable and core dump files. In addition,
19472 @code{maint info sections} provides the following command options (which
19473 may be arbitrarily combined):
19477 Display sections for all loaded object files, including shared libraries.
19478 @item @var{sections}
19479 Display info only for named @var{sections}.
19480 @item @var{section-flags}
19481 Display info only for sections for which @var{section-flags} are true.
19482 The section flags that @value{GDBN} currently knows about are:
19485 Section will have space allocated in the process when loaded.
19486 Set for all sections except those containing debug information.
19488 Section will be loaded from the file into the child process memory.
19489 Set for pre-initialized code and data, clear for @code{.bss} sections.
19491 Section needs to be relocated before loading.
19493 Section cannot be modified by the child process.
19495 Section contains executable code only.
19497 Section contains data only (no executable code).
19499 Section will reside in ROM.
19501 Section contains data for constructor/destructor lists.
19503 Section is not empty.
19505 An instruction to the linker to not output the section.
19506 @item COFF_SHARED_LIBRARY
19507 A notification to the linker that the section contains
19508 COFF shared library information.
19510 Section contains common symbols.
19513 @kindex set trust-readonly-sections
19514 @cindex read-only sections
19515 @item set trust-readonly-sections on
19516 Tell @value{GDBN} that readonly sections in your object file
19517 really are read-only (i.e.@: that their contents will not change).
19518 In that case, @value{GDBN} can fetch values from these sections
19519 out of the object file, rather than from the target program.
19520 For some targets (notably embedded ones), this can be a significant
19521 enhancement to debugging performance.
19523 The default is off.
19525 @item set trust-readonly-sections off
19526 Tell @value{GDBN} not to trust readonly sections. This means that
19527 the contents of the section might change while the program is running,
19528 and must therefore be fetched from the target when needed.
19530 @item show trust-readonly-sections
19531 Show the current setting of trusting readonly sections.
19534 All file-specifying commands allow both absolute and relative file names
19535 as arguments. @value{GDBN} always converts the file name to an absolute file
19536 name and remembers it that way.
19538 @cindex shared libraries
19539 @anchor{Shared Libraries}
19540 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
19541 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
19542 DSBT (TIC6X) shared libraries.
19544 On MS-Windows @value{GDBN} must be linked with the Expat library to support
19545 shared libraries. @xref{Expat}.
19547 @value{GDBN} automatically loads symbol definitions from shared libraries
19548 when you use the @code{run} command, or when you examine a core file.
19549 (Before you issue the @code{run} command, @value{GDBN} does not understand
19550 references to a function in a shared library, however---unless you are
19551 debugging a core file).
19553 @c FIXME: some @value{GDBN} release may permit some refs to undef
19554 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
19555 @c FIXME...lib; check this from time to time when updating manual
19557 There are times, however, when you may wish to not automatically load
19558 symbol definitions from shared libraries, such as when they are
19559 particularly large or there are many of them.
19561 To control the automatic loading of shared library symbols, use the
19565 @kindex set auto-solib-add
19566 @item set auto-solib-add @var{mode}
19567 If @var{mode} is @code{on}, symbols from all shared object libraries
19568 will be loaded automatically when the inferior begins execution, you
19569 attach to an independently started inferior, or when the dynamic linker
19570 informs @value{GDBN} that a new library has been loaded. If @var{mode}
19571 is @code{off}, symbols must be loaded manually, using the
19572 @code{sharedlibrary} command. The default value is @code{on}.
19574 @cindex memory used for symbol tables
19575 If your program uses lots of shared libraries with debug info that
19576 takes large amounts of memory, you can decrease the @value{GDBN}
19577 memory footprint by preventing it from automatically loading the
19578 symbols from shared libraries. To that end, type @kbd{set
19579 auto-solib-add off} before running the inferior, then load each
19580 library whose debug symbols you do need with @kbd{sharedlibrary
19581 @var{regexp}}, where @var{regexp} is a regular expression that matches
19582 the libraries whose symbols you want to be loaded.
19584 @kindex show auto-solib-add
19585 @item show auto-solib-add
19586 Display the current autoloading mode.
19589 @cindex load shared library
19590 To explicitly load shared library symbols, use the @code{sharedlibrary}
19594 @kindex info sharedlibrary
19596 @item info share @var{regex}
19597 @itemx info sharedlibrary @var{regex}
19598 Print the names of the shared libraries which are currently loaded
19599 that match @var{regex}. If @var{regex} is omitted then print
19600 all shared libraries that are loaded.
19603 @item info dll @var{regex}
19604 This is an alias of @code{info sharedlibrary}.
19606 @kindex sharedlibrary
19608 @item sharedlibrary @var{regex}
19609 @itemx share @var{regex}
19610 Load shared object library symbols for files matching a
19611 Unix regular expression.
19612 As with files loaded automatically, it only loads shared libraries
19613 required by your program for a core file or after typing @code{run}. If
19614 @var{regex} is omitted all shared libraries required by your program are
19617 @item nosharedlibrary
19618 @kindex nosharedlibrary
19619 @cindex unload symbols from shared libraries
19620 Unload all shared object library symbols. This discards all symbols
19621 that have been loaded from all shared libraries. Symbols from shared
19622 libraries that were loaded by explicit user requests are not
19626 Sometimes you may wish that @value{GDBN} stops and gives you control
19627 when any of shared library events happen. The best way to do this is
19628 to use @code{catch load} and @code{catch unload} (@pxref{Set
19631 @value{GDBN} also supports the the @code{set stop-on-solib-events}
19632 command for this. This command exists for historical reasons. It is
19633 less useful than setting a catchpoint, because it does not allow for
19634 conditions or commands as a catchpoint does.
19637 @item set stop-on-solib-events
19638 @kindex set stop-on-solib-events
19639 This command controls whether @value{GDBN} should give you control
19640 when the dynamic linker notifies it about some shared library event.
19641 The most common event of interest is loading or unloading of a new
19644 @item show stop-on-solib-events
19645 @kindex show stop-on-solib-events
19646 Show whether @value{GDBN} stops and gives you control when shared
19647 library events happen.
19650 Shared libraries are also supported in many cross or remote debugging
19651 configurations. @value{GDBN} needs to have access to the target's libraries;
19652 this can be accomplished either by providing copies of the libraries
19653 on the host system, or by asking @value{GDBN} to automatically retrieve the
19654 libraries from the target. If copies of the target libraries are
19655 provided, they need to be the same as the target libraries, although the
19656 copies on the target can be stripped as long as the copies on the host are
19659 @cindex where to look for shared libraries
19660 For remote debugging, you need to tell @value{GDBN} where the target
19661 libraries are, so that it can load the correct copies---otherwise, it
19662 may try to load the host's libraries. @value{GDBN} has two variables
19663 to specify the search directories for target libraries.
19666 @cindex prefix for executable and shared library file names
19667 @cindex system root, alternate
19668 @kindex set solib-absolute-prefix
19669 @kindex set sysroot
19670 @item set sysroot @var{path}
19671 Use @var{path} as the system root for the program being debugged. Any
19672 absolute shared library paths will be prefixed with @var{path}; many
19673 runtime loaders store the absolute paths to the shared library in the
19674 target program's memory. When starting processes remotely, and when
19675 attaching to already-running processes (local or remote), their
19676 executable filenames will be prefixed with @var{path} if reported to
19677 @value{GDBN} as absolute by the operating system. If you use
19678 @code{set sysroot} to find executables and shared libraries, they need
19679 to be laid out in the same way that they are on the target, with
19680 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
19683 If @var{path} starts with the sequence @file{target:} and the target
19684 system is remote then @value{GDBN} will retrieve the target binaries
19685 from the remote system. This is only supported when using a remote
19686 target that supports the @code{remote get} command (@pxref{File
19687 Transfer,,Sending files to a remote system}). The part of @var{path}
19688 following the initial @file{target:} (if present) is used as system
19689 root prefix on the remote file system. If @var{path} starts with the
19690 sequence @file{remote:} this is converted to the sequence
19691 @file{target:} by @code{set sysroot}@footnote{Historically the
19692 functionality to retrieve binaries from the remote system was
19693 provided by prefixing @var{path} with @file{remote:}}. If you want
19694 to specify a local system root using a directory that happens to be
19695 named @file{target:} or @file{remote:}, you need to use some
19696 equivalent variant of the name like @file{./target:}.
19698 For targets with an MS-DOS based filesystem, such as MS-Windows and
19699 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
19700 absolute file name with @var{path}. But first, on Unix hosts,
19701 @value{GDBN} converts all backslash directory separators into forward
19702 slashes, because the backslash is not a directory separator on Unix:
19705 c:\foo\bar.dll @result{} c:/foo/bar.dll
19708 Then, @value{GDBN} attempts prefixing the target file name with
19709 @var{path}, and looks for the resulting file name in the host file
19713 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
19716 If that does not find the binary, @value{GDBN} tries removing
19717 the @samp{:} character from the drive spec, both for convenience, and,
19718 for the case of the host file system not supporting file names with
19722 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
19725 This makes it possible to have a system root that mirrors a target
19726 with more than one drive. E.g., you may want to setup your local
19727 copies of the target system shared libraries like so (note @samp{c} vs
19731 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19732 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19733 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19737 and point the system root at @file{/path/to/sysroot}, so that
19738 @value{GDBN} can find the correct copies of both
19739 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19741 If that still does not find the binary, @value{GDBN} tries
19742 removing the whole drive spec from the target file name:
19745 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19748 This last lookup makes it possible to not care about the drive name,
19749 if you don't want or need to.
19751 The @code{set solib-absolute-prefix} command is an alias for @code{set
19754 @cindex default system root
19755 @cindex @samp{--with-sysroot}
19756 You can set the default system root by using the configure-time
19757 @samp{--with-sysroot} option. If the system root is inside
19758 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19759 @samp{--exec-prefix}), then the default system root will be updated
19760 automatically if the installed @value{GDBN} is moved to a new
19763 @kindex show sysroot
19765 Display the current executable and shared library prefix.
19767 @kindex set solib-search-path
19768 @item set solib-search-path @var{path}
19769 If this variable is set, @var{path} is a colon-separated list of
19770 directories to search for shared libraries. @samp{solib-search-path}
19771 is used after @samp{sysroot} fails to locate the library, or if the
19772 path to the library is relative instead of absolute. If you want to
19773 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19774 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19775 finding your host's libraries. @samp{sysroot} is preferred; setting
19776 it to a nonexistent directory may interfere with automatic loading
19777 of shared library symbols.
19779 @kindex show solib-search-path
19780 @item show solib-search-path
19781 Display the current shared library search path.
19783 @cindex DOS file-name semantics of file names.
19784 @kindex set target-file-system-kind (unix|dos-based|auto)
19785 @kindex show target-file-system-kind
19786 @item set target-file-system-kind @var{kind}
19787 Set assumed file system kind for target reported file names.
19789 Shared library file names as reported by the target system may not
19790 make sense as is on the system @value{GDBN} is running on. For
19791 example, when remote debugging a target that has MS-DOS based file
19792 system semantics, from a Unix host, the target may be reporting to
19793 @value{GDBN} a list of loaded shared libraries with file names such as
19794 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19795 drive letters, so the @samp{c:\} prefix is not normally understood as
19796 indicating an absolute file name, and neither is the backslash
19797 normally considered a directory separator character. In that case,
19798 the native file system would interpret this whole absolute file name
19799 as a relative file name with no directory components. This would make
19800 it impossible to point @value{GDBN} at a copy of the remote target's
19801 shared libraries on the host using @code{set sysroot}, and impractical
19802 with @code{set solib-search-path}. Setting
19803 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19804 to interpret such file names similarly to how the target would, and to
19805 map them to file names valid on @value{GDBN}'s native file system
19806 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19807 to one of the supported file system kinds. In that case, @value{GDBN}
19808 tries to determine the appropriate file system variant based on the
19809 current target's operating system (@pxref{ABI, ,Configuring the
19810 Current ABI}). The supported file system settings are:
19814 Instruct @value{GDBN} to assume the target file system is of Unix
19815 kind. Only file names starting the forward slash (@samp{/}) character
19816 are considered absolute, and the directory separator character is also
19820 Instruct @value{GDBN} to assume the target file system is DOS based.
19821 File names starting with either a forward slash, or a drive letter
19822 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19823 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19824 considered directory separators.
19827 Instruct @value{GDBN} to use the file system kind associated with the
19828 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19829 This is the default.
19833 @cindex file name canonicalization
19834 @cindex base name differences
19835 When processing file names provided by the user, @value{GDBN}
19836 frequently needs to compare them to the file names recorded in the
19837 program's debug info. Normally, @value{GDBN} compares just the
19838 @dfn{base names} of the files as strings, which is reasonably fast
19839 even for very large programs. (The base name of a file is the last
19840 portion of its name, after stripping all the leading directories.)
19841 This shortcut in comparison is based upon the assumption that files
19842 cannot have more than one base name. This is usually true, but
19843 references to files that use symlinks or similar filesystem
19844 facilities violate that assumption. If your program records files
19845 using such facilities, or if you provide file names to @value{GDBN}
19846 using symlinks etc., you can set @code{basenames-may-differ} to
19847 @code{true} to instruct @value{GDBN} to completely canonicalize each
19848 pair of file names it needs to compare. This will make file-name
19849 comparisons accurate, but at a price of a significant slowdown.
19852 @item set basenames-may-differ
19853 @kindex set basenames-may-differ
19854 Set whether a source file may have multiple base names.
19856 @item show basenames-may-differ
19857 @kindex show basenames-may-differ
19858 Show whether a source file may have multiple base names.
19862 @section File Caching
19863 @cindex caching of opened files
19864 @cindex caching of bfd objects
19866 To speed up file loading, and reduce memory usage, @value{GDBN} will
19867 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19868 BFD, bfd, The Binary File Descriptor Library}. The following commands
19869 allow visibility and control of the caching behavior.
19872 @kindex maint info bfds
19873 @item maint info bfds
19874 This prints information about each @code{bfd} object that is known to
19877 @kindex maint set bfd-sharing
19878 @kindex maint show bfd-sharing
19879 @kindex bfd caching
19880 @item maint set bfd-sharing
19881 @item maint show bfd-sharing
19882 Control whether @code{bfd} objects can be shared. When sharing is
19883 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19884 than reopening the same file. Turning sharing off does not cause
19885 already shared @code{bfd} objects to be unshared, but all future files
19886 that are opened will create a new @code{bfd} object. Similarly,
19887 re-enabling sharing does not cause multiple existing @code{bfd}
19888 objects to be collapsed into a single shared @code{bfd} object.
19890 @kindex set debug bfd-cache @var{level}
19891 @kindex bfd caching
19892 @item set debug bfd-cache @var{level}
19893 Turns on debugging of the bfd cache, setting the level to @var{level}.
19895 @kindex show debug bfd-cache
19896 @kindex bfd caching
19897 @item show debug bfd-cache
19898 Show the current debugging level of the bfd cache.
19901 @node Separate Debug Files
19902 @section Debugging Information in Separate Files
19903 @cindex separate debugging information files
19904 @cindex debugging information in separate files
19905 @cindex @file{.debug} subdirectories
19906 @cindex debugging information directory, global
19907 @cindex global debugging information directories
19908 @cindex build ID, and separate debugging files
19909 @cindex @file{.build-id} directory
19911 @value{GDBN} allows you to put a program's debugging information in a
19912 file separate from the executable itself, in a way that allows
19913 @value{GDBN} to find and load the debugging information automatically.
19914 Since debugging information can be very large---sometimes larger
19915 than the executable code itself---some systems distribute debugging
19916 information for their executables in separate files, which users can
19917 install only when they need to debug a problem.
19919 @value{GDBN} supports two ways of specifying the separate debug info
19924 The executable contains a @dfn{debug link} that specifies the name of
19925 the separate debug info file. The separate debug file's name is
19926 usually @file{@var{executable}.debug}, where @var{executable} is the
19927 name of the corresponding executable file without leading directories
19928 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19929 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19930 checksum for the debug file, which @value{GDBN} uses to validate that
19931 the executable and the debug file came from the same build.
19934 The executable contains a @dfn{build ID}, a unique bit string that is
19935 also present in the corresponding debug info file. (This is supported
19936 only on some operating systems, when using the ELF or PE file formats
19937 for binary files and the @sc{gnu} Binutils.) For more details about
19938 this feature, see the description of the @option{--build-id}
19939 command-line option in @ref{Options, , Command Line Options, ld,
19940 The GNU Linker}. The debug info file's name is not specified
19941 explicitly by the build ID, but can be computed from the build ID, see
19945 Depending on the way the debug info file is specified, @value{GDBN}
19946 uses two different methods of looking for the debug file:
19950 For the ``debug link'' method, @value{GDBN} looks up the named file in
19951 the directory of the executable file, then in a subdirectory of that
19952 directory named @file{.debug}, and finally under each one of the global debug
19953 directories, in a subdirectory whose name is identical to the leading
19954 directories of the executable's absolute file name.
19957 For the ``build ID'' method, @value{GDBN} looks in the
19958 @file{.build-id} subdirectory of each one of the global debug directories for
19959 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19960 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19961 are the rest of the bit string. (Real build ID strings are 32 or more
19962 hex characters, not 10.)
19965 So, for example, suppose you ask @value{GDBN} to debug
19966 @file{/usr/bin/ls}, which has a debug link that specifies the
19967 file @file{ls.debug}, and a build ID whose value in hex is
19968 @code{abcdef1234}. If the list of the global debug directories includes
19969 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19970 debug information files, in the indicated order:
19974 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19976 @file{/usr/bin/ls.debug}
19978 @file{/usr/bin/.debug/ls.debug}
19980 @file{/usr/lib/debug/usr/bin/ls.debug}.
19983 @anchor{debug-file-directory}
19984 Global debugging info directories default to what is set by @value{GDBN}
19985 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19986 you can also set the global debugging info directories, and view the list
19987 @value{GDBN} is currently using.
19991 @kindex set debug-file-directory
19992 @item set debug-file-directory @var{directories}
19993 Set the directories which @value{GDBN} searches for separate debugging
19994 information files to @var{directory}. Multiple path components can be set
19995 concatenating them by a path separator.
19997 @kindex show debug-file-directory
19998 @item show debug-file-directory
19999 Show the directories @value{GDBN} searches for separate debugging
20004 @cindex @code{.gnu_debuglink} sections
20005 @cindex debug link sections
20006 A debug link is a special section of the executable file named
20007 @code{.gnu_debuglink}. The section must contain:
20011 A filename, with any leading directory components removed, followed by
20014 zero to three bytes of padding, as needed to reach the next four-byte
20015 boundary within the section, and
20017 a four-byte CRC checksum, stored in the same endianness used for the
20018 executable file itself. The checksum is computed on the debugging
20019 information file's full contents by the function given below, passing
20020 zero as the @var{crc} argument.
20023 Any executable file format can carry a debug link, as long as it can
20024 contain a section named @code{.gnu_debuglink} with the contents
20027 @cindex @code{.note.gnu.build-id} sections
20028 @cindex build ID sections
20029 The build ID is a special section in the executable file (and in other
20030 ELF binary files that @value{GDBN} may consider). This section is
20031 often named @code{.note.gnu.build-id}, but that name is not mandatory.
20032 It contains unique identification for the built files---the ID remains
20033 the same across multiple builds of the same build tree. The default
20034 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
20035 content for the build ID string. The same section with an identical
20036 value is present in the original built binary with symbols, in its
20037 stripped variant, and in the separate debugging information file.
20039 The debugging information file itself should be an ordinary
20040 executable, containing a full set of linker symbols, sections, and
20041 debugging information. The sections of the debugging information file
20042 should have the same names, addresses, and sizes as the original file,
20043 but they need not contain any data---much like a @code{.bss} section
20044 in an ordinary executable.
20046 The @sc{gnu} binary utilities (Binutils) package includes the
20047 @samp{objcopy} utility that can produce
20048 the separated executable / debugging information file pairs using the
20049 following commands:
20052 @kbd{objcopy --only-keep-debug foo foo.debug}
20057 These commands remove the debugging
20058 information from the executable file @file{foo} and place it in the file
20059 @file{foo.debug}. You can use the first, second or both methods to link the
20064 The debug link method needs the following additional command to also leave
20065 behind a debug link in @file{foo}:
20068 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
20071 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
20072 a version of the @code{strip} command such that the command @kbd{strip foo -f
20073 foo.debug} has the same functionality as the two @code{objcopy} commands and
20074 the @code{ln -s} command above, together.
20077 Build ID gets embedded into the main executable using @code{ld --build-id} or
20078 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
20079 compatibility fixes for debug files separation are present in @sc{gnu} binary
20080 utilities (Binutils) package since version 2.18.
20085 @cindex CRC algorithm definition
20086 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
20087 IEEE 802.3 using the polynomial:
20089 @c TexInfo requires naked braces for multi-digit exponents for Tex
20090 @c output, but this causes HTML output to barf. HTML has to be set using
20091 @c raw commands. So we end up having to specify this equation in 2
20096 <em>x</em><sup>32</sup> + <em>x</em><sup>26</sup> + <em>x</em><sup>23</sup> + <em>x</em><sup>22</sup> + <em>x</em><sup>16</sup> + <em>x</em><sup>12</sup> + <em>x</em><sup>11</sup>
20097 + <em>x</em><sup>10</sup> + <em>x</em><sup>8</sup> + <em>x</em><sup>7</sup> + <em>x</em><sup>5</sup> + <em>x</em><sup>4</sup> + <em>x</em><sup>2</sup> + <em>x</em> + 1
20103 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
20104 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
20108 The function is computed byte at a time, taking the least
20109 significant bit of each byte first. The initial pattern
20110 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
20111 the final result is inverted to ensure trailing zeros also affect the
20114 @emph{Note:} This is the same CRC polynomial as used in handling the
20115 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
20116 However in the case of the Remote Serial Protocol, the CRC is computed
20117 @emph{most} significant bit first, and the result is not inverted, so
20118 trailing zeros have no effect on the CRC value.
20120 To complete the description, we show below the code of the function
20121 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
20122 initially supplied @code{crc} argument means that an initial call to
20123 this function passing in zero will start computing the CRC using
20126 @kindex gnu_debuglink_crc32
20129 gnu_debuglink_crc32 (unsigned long crc,
20130 unsigned char *buf, size_t len)
20132 static const unsigned long crc32_table[256] =
20134 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
20135 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
20136 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
20137 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
20138 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
20139 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
20140 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
20141 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
20142 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
20143 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
20144 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
20145 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
20146 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
20147 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
20148 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
20149 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
20150 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
20151 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
20152 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
20153 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
20154 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
20155 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
20156 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
20157 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
20158 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
20159 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
20160 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
20161 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
20162 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
20163 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
20164 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
20165 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
20166 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
20167 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
20168 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
20169 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
20170 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
20171 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
20172 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
20173 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
20174 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
20175 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
20176 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
20177 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
20178 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
20179 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
20180 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
20181 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
20182 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
20183 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
20184 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
20187 unsigned char *end;
20189 crc = ~crc & 0xffffffff;
20190 for (end = buf + len; buf < end; ++buf)
20191 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
20192 return ~crc & 0xffffffff;
20197 This computation does not apply to the ``build ID'' method.
20199 @node MiniDebugInfo
20200 @section Debugging information in a special section
20201 @cindex separate debug sections
20202 @cindex @samp{.gnu_debugdata} section
20204 Some systems ship pre-built executables and libraries that have a
20205 special @samp{.gnu_debugdata} section. This feature is called
20206 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
20207 is used to supply extra symbols for backtraces.
20209 The intent of this section is to provide extra minimal debugging
20210 information for use in simple backtraces. It is not intended to be a
20211 replacement for full separate debugging information (@pxref{Separate
20212 Debug Files}). The example below shows the intended use; however,
20213 @value{GDBN} does not currently put restrictions on what sort of
20214 debugging information might be included in the section.
20216 @value{GDBN} has support for this extension. If the section exists,
20217 then it is used provided that no other source of debugging information
20218 can be found, and that @value{GDBN} was configured with LZMA support.
20220 This section can be easily created using @command{objcopy} and other
20221 standard utilities:
20224 # Extract the dynamic symbols from the main binary, there is no need
20225 # to also have these in the normal symbol table.
20226 nm -D @var{binary} --format=posix --defined-only \
20227 | awk '@{ print $1 @}' | sort > dynsyms
20229 # Extract all the text (i.e. function) symbols from the debuginfo.
20230 # (Note that we actually also accept "D" symbols, for the benefit
20231 # of platforms like PowerPC64 that use function descriptors.)
20232 nm @var{binary} --format=posix --defined-only \
20233 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
20236 # Keep all the function symbols not already in the dynamic symbol
20238 comm -13 dynsyms funcsyms > keep_symbols
20240 # Separate full debug info into debug binary.
20241 objcopy --only-keep-debug @var{binary} debug
20243 # Copy the full debuginfo, keeping only a minimal set of symbols and
20244 # removing some unnecessary sections.
20245 objcopy -S --remove-section .gdb_index --remove-section .comment \
20246 --keep-symbols=keep_symbols debug mini_debuginfo
20248 # Drop the full debug info from the original binary.
20249 strip --strip-all -R .comment @var{binary}
20251 # Inject the compressed data into the .gnu_debugdata section of the
20254 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
20258 @section Index Files Speed Up @value{GDBN}
20259 @cindex index files
20260 @cindex @samp{.gdb_index} section
20262 When @value{GDBN} finds a symbol file, it scans the symbols in the
20263 file in order to construct an internal symbol table. This lets most
20264 @value{GDBN} operations work quickly---at the cost of a delay early
20265 on. For large programs, this delay can be quite lengthy, so
20266 @value{GDBN} provides a way to build an index, which speeds up
20269 For convenience, @value{GDBN} comes with a program,
20270 @command{gdb-add-index}, which can be used to add the index to a
20271 symbol file. It takes the symbol file as its only argument:
20274 $ gdb-add-index symfile
20277 @xref{gdb-add-index}.
20279 It is also possible to do the work manually. Here is what
20280 @command{gdb-add-index} does behind the curtains.
20282 The index is stored as a section in the symbol file. @value{GDBN} can
20283 write the index to a file, then you can put it into the symbol file
20284 using @command{objcopy}.
20286 To create an index file, use the @code{save gdb-index} command:
20289 @item save gdb-index [-dwarf-5] @var{directory}
20290 @kindex save gdb-index
20291 Create index files for all symbol files currently known by
20292 @value{GDBN}. For each known @var{symbol-file}, this command by
20293 default creates it produces a single file
20294 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
20295 the @option{-dwarf-5} option, it produces 2 files:
20296 @file{@var{symbol-file}.debug_names} and
20297 @file{@var{symbol-file}.debug_str}. The files are created in the
20298 given @var{directory}.
20301 Once you have created an index file you can merge it into your symbol
20302 file, here named @file{symfile}, using @command{objcopy}:
20305 $ objcopy --add-section .gdb_index=symfile.gdb-index \
20306 --set-section-flags .gdb_index=readonly symfile symfile
20309 Or for @code{-dwarf-5}:
20312 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
20313 $ cat symfile.debug_str >>symfile.debug_str.new
20314 $ objcopy --add-section .debug_names=symfile.gdb-index \
20315 --set-section-flags .debug_names=readonly \
20316 --update-section .debug_str=symfile.debug_str.new symfile symfile
20319 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
20320 sections that have been deprecated. Usually they are deprecated because
20321 they are missing a new feature or have performance issues.
20322 To tell @value{GDBN} to use a deprecated index section anyway
20323 specify @code{set use-deprecated-index-sections on}.
20324 The default is @code{off}.
20325 This can speed up startup, but may result in some functionality being lost.
20326 @xref{Index Section Format}.
20328 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
20329 must be done before gdb reads the file. The following will not work:
20332 $ gdb -ex "set use-deprecated-index-sections on" <program>
20335 Instead you must do, for example,
20338 $ gdb -iex "set use-deprecated-index-sections on" <program>
20341 There are currently some limitation on indices. They only work when
20342 for DWARF debugging information, not stabs. And, they do not
20343 currently work for programs using Ada.
20345 @subsection Automatic symbol index cache
20347 It is possible for @value{GDBN} to automatically save a copy of this index in a
20348 cache on disk and retrieve it from there when loading the same binary in the
20349 future. This feature can be turned on with @kbd{set index-cache on}. The
20350 following commands can be used to tweak the behavior of the index cache.
20354 @item set index-cache on
20355 @itemx set index-cache off
20356 Enable or disable the use of the symbol index cache.
20358 @item set index-cache directory @var{directory}
20359 @itemx show index-cache directory
20360 Set/show the directory where index files will be saved.
20362 The default value for this directory depends on the host platform. On
20363 most systems, the index is cached in the @file{gdb} subdirectory of
20364 the directory pointed to by the @env{XDG_CACHE_HOME} environment
20365 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
20366 of your home directory. However, on some systems, the default may
20367 differ according to local convention.
20369 There is no limit on the disk space used by index cache. It is perfectly safe
20370 to delete the content of that directory to free up disk space.
20372 @item show index-cache stats
20373 Print the number of cache hits and misses since the launch of @value{GDBN}.
20377 @node Symbol Errors
20378 @section Errors Reading Symbol Files
20380 While reading a symbol file, @value{GDBN} occasionally encounters problems,
20381 such as symbol types it does not recognize, or known bugs in compiler
20382 output. By default, @value{GDBN} does not notify you of such problems, since
20383 they are relatively common and primarily of interest to people
20384 debugging compilers. If you are interested in seeing information
20385 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
20386 only one message about each such type of problem, no matter how many
20387 times the problem occurs; or you can ask @value{GDBN} to print more messages,
20388 to see how many times the problems occur, with the @code{set
20389 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
20392 The messages currently printed, and their meanings, include:
20395 @item inner block not inside outer block in @var{symbol}
20397 The symbol information shows where symbol scopes begin and end
20398 (such as at the start of a function or a block of statements). This
20399 error indicates that an inner scope block is not fully contained
20400 in its outer scope blocks.
20402 @value{GDBN} circumvents the problem by treating the inner block as if it had
20403 the same scope as the outer block. In the error message, @var{symbol}
20404 may be shown as ``@code{(don't know)}'' if the outer block is not a
20407 @item block at @var{address} out of order
20409 The symbol information for symbol scope blocks should occur in
20410 order of increasing addresses. This error indicates that it does not
20413 @value{GDBN} does not circumvent this problem, and has trouble
20414 locating symbols in the source file whose symbols it is reading. (You
20415 can often determine what source file is affected by specifying
20416 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
20419 @item bad block start address patched
20421 The symbol information for a symbol scope block has a start address
20422 smaller than the address of the preceding source line. This is known
20423 to occur in the SunOS 4.1.1 (and earlier) C compiler.
20425 @value{GDBN} circumvents the problem by treating the symbol scope block as
20426 starting on the previous source line.
20428 @item bad string table offset in symbol @var{n}
20431 Symbol number @var{n} contains a pointer into the string table which is
20432 larger than the size of the string table.
20434 @value{GDBN} circumvents the problem by considering the symbol to have the
20435 name @code{foo}, which may cause other problems if many symbols end up
20438 @item unknown symbol type @code{0x@var{nn}}
20440 The symbol information contains new data types that @value{GDBN} does
20441 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
20442 uncomprehended information, in hexadecimal.
20444 @value{GDBN} circumvents the error by ignoring this symbol information.
20445 This usually allows you to debug your program, though certain symbols
20446 are not accessible. If you encounter such a problem and feel like
20447 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
20448 on @code{complain}, then go up to the function @code{read_dbx_symtab}
20449 and examine @code{*bufp} to see the symbol.
20451 @item stub type has NULL name
20453 @value{GDBN} could not find the full definition for a struct or class.
20455 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
20456 The symbol information for a C@t{++} member function is missing some
20457 information that recent versions of the compiler should have output for
20460 @item info mismatch between compiler and debugger
20462 @value{GDBN} could not parse a type specification output by the compiler.
20467 @section GDB Data Files
20469 @cindex prefix for data files
20470 @value{GDBN} will sometimes read an auxiliary data file. These files
20471 are kept in a directory known as the @dfn{data directory}.
20473 You can set the data directory's name, and view the name @value{GDBN}
20474 is currently using.
20477 @kindex set data-directory
20478 @item set data-directory @var{directory}
20479 Set the directory which @value{GDBN} searches for auxiliary data files
20480 to @var{directory}.
20482 @kindex show data-directory
20483 @item show data-directory
20484 Show the directory @value{GDBN} searches for auxiliary data files.
20487 @cindex default data directory
20488 @cindex @samp{--with-gdb-datadir}
20489 You can set the default data directory by using the configure-time
20490 @samp{--with-gdb-datadir} option. If the data directory is inside
20491 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
20492 @samp{--exec-prefix}), then the default data directory will be updated
20493 automatically if the installed @value{GDBN} is moved to a new
20496 The data directory may also be specified with the
20497 @code{--data-directory} command line option.
20498 @xref{Mode Options}.
20501 @chapter Specifying a Debugging Target
20503 @cindex debugging target
20504 A @dfn{target} is the execution environment occupied by your program.
20506 Often, @value{GDBN} runs in the same host environment as your program;
20507 in that case, the debugging target is specified as a side effect when
20508 you use the @code{file} or @code{core} commands. When you need more
20509 flexibility---for example, running @value{GDBN} on a physically separate
20510 host, or controlling a standalone system over a serial port or a
20511 realtime system over a TCP/IP connection---you can use the @code{target}
20512 command to specify one of the target types configured for @value{GDBN}
20513 (@pxref{Target Commands, ,Commands for Managing Targets}).
20515 @cindex target architecture
20516 It is possible to build @value{GDBN} for several different @dfn{target
20517 architectures}. When @value{GDBN} is built like that, you can choose
20518 one of the available architectures with the @kbd{set architecture}
20522 @kindex set architecture
20523 @kindex show architecture
20524 @item set architecture @var{arch}
20525 This command sets the current target architecture to @var{arch}. The
20526 value of @var{arch} can be @code{"auto"}, in addition to one of the
20527 supported architectures.
20529 @item show architecture
20530 Show the current target architecture.
20532 @item set processor
20534 @kindex set processor
20535 @kindex show processor
20536 These are alias commands for, respectively, @code{set architecture}
20537 and @code{show architecture}.
20541 * Active Targets:: Active targets
20542 * Target Commands:: Commands for managing targets
20543 * Byte Order:: Choosing target byte order
20546 @node Active Targets
20547 @section Active Targets
20549 @cindex stacking targets
20550 @cindex active targets
20551 @cindex multiple targets
20553 There are multiple classes of targets such as: processes, executable files or
20554 recording sessions. Core files belong to the process class, making core file
20555 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
20556 on multiple active targets, one in each class. This allows you to (for
20557 example) start a process and inspect its activity, while still having access to
20558 the executable file after the process finishes. Or if you start process
20559 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
20560 presented a virtual layer of the recording target, while the process target
20561 remains stopped at the chronologically last point of the process execution.
20563 Use the @code{core-file} and @code{exec-file} commands to select a new core
20564 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
20565 specify as a target a process that is already running, use the @code{attach}
20566 command (@pxref{Attach, ,Debugging an Already-running Process}).
20568 @node Target Commands
20569 @section Commands for Managing Targets
20572 @item target @var{type} @var{parameters}
20573 Connects the @value{GDBN} host environment to a target machine or
20574 process. A target is typically a protocol for talking to debugging
20575 facilities. You use the argument @var{type} to specify the type or
20576 protocol of the target machine.
20578 Further @var{parameters} are interpreted by the target protocol, but
20579 typically include things like device names or host names to connect
20580 with, process numbers, and baud rates.
20582 The @code{target} command does not repeat if you press @key{RET} again
20583 after executing the command.
20585 @kindex help target
20587 Displays the names of all targets available. To display targets
20588 currently selected, use either @code{info target} or @code{info files}
20589 (@pxref{Files, ,Commands to Specify Files}).
20591 @item help target @var{name}
20592 Describe a particular target, including any parameters necessary to
20595 @kindex set gnutarget
20596 @item set gnutarget @var{args}
20597 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
20598 knows whether it is reading an @dfn{executable},
20599 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
20600 with the @code{set gnutarget} command. Unlike most @code{target} commands,
20601 with @code{gnutarget} the @code{target} refers to a program, not a machine.
20604 @emph{Warning:} To specify a file format with @code{set gnutarget},
20605 you must know the actual BFD name.
20609 @xref{Files, , Commands to Specify Files}.
20611 @kindex show gnutarget
20612 @item show gnutarget
20613 Use the @code{show gnutarget} command to display what file format
20614 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
20615 @value{GDBN} will determine the file format for each file automatically,
20616 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
20619 @cindex common targets
20620 Here are some common targets (available, or not, depending on the GDB
20625 @item target exec @var{program}
20626 @cindex executable file target
20627 An executable file. @samp{target exec @var{program}} is the same as
20628 @samp{exec-file @var{program}}.
20630 @item target core @var{filename}
20631 @cindex core dump file target
20632 A core dump file. @samp{target core @var{filename}} is the same as
20633 @samp{core-file @var{filename}}.
20635 @item target remote @var{medium}
20636 @cindex remote target
20637 A remote system connected to @value{GDBN} via a serial line or network
20638 connection. This command tells @value{GDBN} to use its own remote
20639 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
20641 For example, if you have a board connected to @file{/dev/ttya} on the
20642 machine running @value{GDBN}, you could say:
20645 target remote /dev/ttya
20648 @code{target remote} supports the @code{load} command. This is only
20649 useful if you have some other way of getting the stub to the target
20650 system, and you can put it somewhere in memory where it won't get
20651 clobbered by the download.
20653 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20654 @cindex built-in simulator target
20655 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
20663 works; however, you cannot assume that a specific memory map, device
20664 drivers, or even basic I/O is available, although some simulators do
20665 provide these. For info about any processor-specific simulator details,
20666 see the appropriate section in @ref{Embedded Processors, ,Embedded
20669 @item target native
20670 @cindex native target
20671 Setup for local/native process debugging. Useful to make the
20672 @code{run} command spawn native processes (likewise @code{attach},
20673 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
20674 (@pxref{set auto-connect-native-target}).
20678 Different targets are available on different configurations of @value{GDBN};
20679 your configuration may have more or fewer targets.
20681 Many remote targets require you to download the executable's code once
20682 you've successfully established a connection. You may wish to control
20683 various aspects of this process.
20688 @kindex set hash@r{, for remote monitors}
20689 @cindex hash mark while downloading
20690 This command controls whether a hash mark @samp{#} is displayed while
20691 downloading a file to the remote monitor. If on, a hash mark is
20692 displayed after each S-record is successfully downloaded to the
20696 @kindex show hash@r{, for remote monitors}
20697 Show the current status of displaying the hash mark.
20699 @item set debug monitor
20700 @kindex set debug monitor
20701 @cindex display remote monitor communications
20702 Enable or disable display of communications messages between
20703 @value{GDBN} and the remote monitor.
20705 @item show debug monitor
20706 @kindex show debug monitor
20707 Show the current status of displaying communications between
20708 @value{GDBN} and the remote monitor.
20713 @kindex load @var{filename} @var{offset}
20714 @item load @var{filename} @var{offset}
20716 Depending on what remote debugging facilities are configured into
20717 @value{GDBN}, the @code{load} command may be available. Where it exists, it
20718 is meant to make @var{filename} (an executable) available for debugging
20719 on the remote system---by downloading, or dynamic linking, for example.
20720 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
20721 the @code{add-symbol-file} command.
20723 If your @value{GDBN} does not have a @code{load} command, attempting to
20724 execute it gets the error message ``@code{You can't do that when your
20725 target is @dots{}}''
20727 The file is loaded at whatever address is specified in the executable.
20728 For some object file formats, you can specify the load address when you
20729 link the program; for other formats, like a.out, the object file format
20730 specifies a fixed address.
20731 @c FIXME! This would be a good place for an xref to the GNU linker doc.
20733 It is also possible to tell @value{GDBN} to load the executable file at a
20734 specific offset described by the optional argument @var{offset}. When
20735 @var{offset} is provided, @var{filename} must also be provided.
20737 Depending on the remote side capabilities, @value{GDBN} may be able to
20738 load programs into flash memory.
20740 @code{load} does not repeat if you press @key{RET} again after using it.
20745 @kindex flash-erase
20747 @anchor{flash-erase}
20749 Erases all known flash memory regions on the target.
20754 @section Choosing Target Byte Order
20756 @cindex choosing target byte order
20757 @cindex target byte order
20759 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
20760 offer the ability to run either big-endian or little-endian byte
20761 orders. Usually the executable or symbol will include a bit to
20762 designate the endian-ness, and you will not need to worry about
20763 which to use. However, you may still find it useful to adjust
20764 @value{GDBN}'s idea of processor endian-ness manually.
20768 @item set endian big
20769 Instruct @value{GDBN} to assume the target is big-endian.
20771 @item set endian little
20772 Instruct @value{GDBN} to assume the target is little-endian.
20774 @item set endian auto
20775 Instruct @value{GDBN} to use the byte order associated with the
20779 Display @value{GDBN}'s current idea of the target byte order.
20783 If the @code{set endian auto} mode is in effect and no executable has
20784 been selected, then the endianness used is the last one chosen either
20785 by one of the @code{set endian big} and @code{set endian little}
20786 commands or by inferring from the last executable used. If no
20787 endianness has been previously chosen, then the default for this mode
20788 is inferred from the target @value{GDBN} has been built for, and is
20789 @code{little} if the name of the target CPU has an @code{el} suffix
20790 and @code{big} otherwise.
20792 Note that these commands merely adjust interpretation of symbolic
20793 data on the host, and that they have absolutely no effect on the
20797 @node Remote Debugging
20798 @chapter Debugging Remote Programs
20799 @cindex remote debugging
20801 If you are trying to debug a program running on a machine that cannot run
20802 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20803 For example, you might use remote debugging on an operating system kernel,
20804 or on a small system which does not have a general purpose operating system
20805 powerful enough to run a full-featured debugger.
20807 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20808 to make this work with particular debugging targets. In addition,
20809 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20810 but not specific to any particular target system) which you can use if you
20811 write the remote stubs---the code that runs on the remote system to
20812 communicate with @value{GDBN}.
20814 Other remote targets may be available in your
20815 configuration of @value{GDBN}; use @code{help target} to list them.
20818 * Connecting:: Connecting to a remote target
20819 * File Transfer:: Sending files to a remote system
20820 * Server:: Using the gdbserver program
20821 * Remote Configuration:: Remote configuration
20822 * Remote Stub:: Implementing a remote stub
20826 @section Connecting to a Remote Target
20827 @cindex remote debugging, connecting
20828 @cindex @code{gdbserver}, connecting
20829 @cindex remote debugging, types of connections
20830 @cindex @code{gdbserver}, types of connections
20831 @cindex @code{gdbserver}, @code{target remote} mode
20832 @cindex @code{gdbserver}, @code{target extended-remote} mode
20834 This section describes how to connect to a remote target, including the
20835 types of connections and their differences, how to set up executable and
20836 symbol files on the host and target, and the commands used for
20837 connecting to and disconnecting from the remote target.
20839 @subsection Types of Remote Connections
20841 @value{GDBN} supports two types of remote connections, @code{target remote}
20842 mode and @code{target extended-remote} mode. Note that many remote targets
20843 support only @code{target remote} mode. There are several major
20844 differences between the two types of connections, enumerated here:
20848 @cindex remote debugging, detach and program exit
20849 @item Result of detach or program exit
20850 @strong{With target remote mode:} When the debugged program exits or you
20851 detach from it, @value{GDBN} disconnects from the target. When using
20852 @code{gdbserver}, @code{gdbserver} will exit.
20854 @strong{With target extended-remote mode:} When the debugged program exits or
20855 you detach from it, @value{GDBN} remains connected to the target, even
20856 though no program is running. You can rerun the program, attach to a
20857 running program, or use @code{monitor} commands specific to the target.
20859 When using @code{gdbserver} in this case, it does not exit unless it was
20860 invoked using the @option{--once} option. If the @option{--once} option
20861 was not used, you can ask @code{gdbserver} to exit using the
20862 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20864 @item Specifying the program to debug
20865 For both connection types you use the @code{file} command to specify the
20866 program on the host system. If you are using @code{gdbserver} there are
20867 some differences in how to specify the location of the program on the
20870 @strong{With target remote mode:} You must either specify the program to debug
20871 on the @code{gdbserver} command line or use the @option{--attach} option
20872 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20874 @cindex @option{--multi}, @code{gdbserver} option
20875 @strong{With target extended-remote mode:} You may specify the program to debug
20876 on the @code{gdbserver} command line, or you can load the program or attach
20877 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20879 @anchor{--multi Option in Types of Remote Connnections}
20880 You can start @code{gdbserver} without supplying an initial command to run
20881 or process ID to attach. To do this, use the @option{--multi} command line
20882 option. Then you can connect using @code{target extended-remote} and start
20883 the program you want to debug (see below for details on using the
20884 @code{run} command in this scenario). Note that the conditions under which
20885 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20886 (@code{target remote} or @code{target extended-remote}). The
20887 @option{--multi} option to @code{gdbserver} has no influence on that.
20889 @item The @code{run} command
20890 @strong{With target remote mode:} The @code{run} command is not
20891 supported. Once a connection has been established, you can use all
20892 the usual @value{GDBN} commands to examine and change data. The
20893 remote program is already running, so you can use commands like
20894 @kbd{step} and @kbd{continue}.
20896 @strong{With target extended-remote mode:} The @code{run} command is
20897 supported. The @code{run} command uses the value set by
20898 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20899 the program to run. Command line arguments are supported, except for
20900 wildcard expansion and I/O redirection (@pxref{Arguments}).
20902 If you specify the program to debug on the command line, then the
20903 @code{run} command is not required to start execution, and you can
20904 resume using commands like @kbd{step} and @kbd{continue} as with
20905 @code{target remote} mode.
20907 @anchor{Attaching in Types of Remote Connections}
20909 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20910 not supported. To attach to a running program using @code{gdbserver}, you
20911 must use the @option{--attach} option (@pxref{Running gdbserver}).
20913 @strong{With target extended-remote mode:} To attach to a running program,
20914 you may use the @code{attach} command after the connection has been
20915 established. If you are using @code{gdbserver}, you may also invoke
20916 @code{gdbserver} using the @option{--attach} option
20917 (@pxref{Running gdbserver}).
20921 @anchor{Host and target files}
20922 @subsection Host and Target Files
20923 @cindex remote debugging, symbol files
20924 @cindex symbol files, remote debugging
20926 @value{GDBN}, running on the host, needs access to symbol and debugging
20927 information for your program running on the target. This requires
20928 access to an unstripped copy of your program, and possibly any associated
20929 symbol files. Note that this section applies equally to both @code{target
20930 remote} mode and @code{target extended-remote} mode.
20932 Some remote targets (@pxref{qXfer executable filename read}, and
20933 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20934 the same connection used to communicate with @value{GDBN}. With such a
20935 target, if the remote program is unstripped, the only command you need is
20936 @code{target remote} (or @code{target extended-remote}).
20938 If the remote program is stripped, or the target does not support remote
20939 program file access, start up @value{GDBN} using the name of the local
20940 unstripped copy of your program as the first argument, or use the
20941 @code{file} command. Use @code{set sysroot} to specify the location (on
20942 the host) of target libraries (unless your @value{GDBN} was compiled with
20943 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20944 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20947 The symbol file and target libraries must exactly match the executable
20948 and libraries on the target, with one exception: the files on the host
20949 system should not be stripped, even if the files on the target system
20950 are. Mismatched or missing files will lead to confusing results
20951 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20952 files may also prevent @code{gdbserver} from debugging multi-threaded
20955 @subsection Remote Connection Commands
20956 @cindex remote connection commands
20957 @value{GDBN} can communicate with the target over a serial line, a
20958 local Unix domain socket, or
20959 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20960 each case, @value{GDBN} uses the same protocol for debugging your
20961 program; only the medium carrying the debugging packets varies. The
20962 @code{target remote} and @code{target extended-remote} commands
20963 establish a connection to the target. Both commands accept the same
20964 arguments, which indicate the medium to use:
20968 @item target remote @var{serial-device}
20969 @itemx target extended-remote @var{serial-device}
20970 @cindex serial line, @code{target remote}
20971 Use @var{serial-device} to communicate with the target. For example,
20972 to use a serial line connected to the device named @file{/dev/ttyb}:
20975 target remote /dev/ttyb
20978 If you're using a serial line, you may want to give @value{GDBN} the
20979 @samp{--baud} option, or use the @code{set serial baud} command
20980 (@pxref{Remote Configuration, set serial baud}) before the
20981 @code{target} command.
20983 @item target remote @var{local-socket}
20984 @itemx target extended-remote @var{local-socket}
20985 @cindex local socket, @code{target remote}
20986 @cindex Unix domain socket
20987 Use @var{local-socket} to communicate with the target. For example,
20988 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
20991 target remote /tmp/gdb-socket0
20994 Note that this command has the same form as the command to connect
20995 to a serial line. @value{GDBN} will automatically determine which
20996 kind of file you have specified and will make the appropriate kind
20998 This feature is not available if the host system does not support
20999 Unix domain sockets.
21001 @item target remote @code{@var{host}:@var{port}}
21002 @itemx target remote @code{@var{[host]}:@var{port}}
21003 @itemx target remote @code{tcp:@var{host}:@var{port}}
21004 @itemx target remote @code{tcp:@var{[host]}:@var{port}}
21005 @itemx target remote @code{tcp4:@var{host}:@var{port}}
21006 @itemx target remote @code{tcp6:@var{host}:@var{port}}
21007 @itemx target remote @code{tcp6:@var{[host]}:@var{port}}
21008 @itemx target extended-remote @code{@var{host}:@var{port}}
21009 @itemx target extended-remote @code{@var{[host]}:@var{port}}
21010 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
21011 @itemx target extended-remote @code{tcp:@var{[host]}:@var{port}}
21012 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
21013 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
21014 @itemx target extended-remote @code{tcp6:@var{[host]}:@var{port}}
21015 @cindex @acronym{TCP} port, @code{target remote}
21016 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
21017 The @var{host} may be either a host name, a numeric @acronym{IPv4}
21018 address, or a numeric @acronym{IPv6} address (with or without the
21019 square brackets to separate the address from the port); @var{port}
21020 must be a decimal number. The @var{host} could be the target machine
21021 itself, if it is directly connected to the net, or it might be a
21022 terminal server which in turn has a serial line to the target.
21024 For example, to connect to port 2828 on a terminal server named
21028 target remote manyfarms:2828
21031 To connect to port 2828 on a terminal server whose address is
21032 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
21033 square bracket syntax:
21036 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
21040 or explicitly specify the @acronym{IPv6} protocol:
21043 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
21046 This last example may be confusing to the reader, because there is no
21047 visible separation between the hostname and the port number.
21048 Therefore, we recommend the user to provide @acronym{IPv6} addresses
21049 using square brackets for clarity. However, it is important to
21050 mention that for @value{GDBN} there is no ambiguity: the number after
21051 the last colon is considered to be the port number.
21053 If your remote target is actually running on the same machine as your
21054 debugger session (e.g.@: a simulator for your target running on the
21055 same host), you can omit the hostname. For example, to connect to
21056 port 1234 on your local machine:
21059 target remote :1234
21063 Note that the colon is still required here.
21065 @item target remote @code{udp:@var{host}:@var{port}}
21066 @itemx target remote @code{udp:@var{[host]}:@var{port}}
21067 @itemx target remote @code{udp4:@var{host}:@var{port}}
21068 @itemx target remote @code{udp6:@var{[host]}:@var{port}}
21069 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21070 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21071 @itemx target extended-remote @code{udp:@var{[host]}:@var{port}}
21072 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
21073 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
21074 @itemx target extended-remote @code{udp6:@var{[host]}:@var{port}}
21075 @cindex @acronym{UDP} port, @code{target remote}
21076 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
21077 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
21080 target remote udp:manyfarms:2828
21083 When using a @acronym{UDP} connection for remote debugging, you should
21084 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
21085 can silently drop packets on busy or unreliable networks, which will
21086 cause havoc with your debugging session.
21088 @item target remote | @var{command}
21089 @itemx target extended-remote | @var{command}
21090 @cindex pipe, @code{target remote} to
21091 Run @var{command} in the background and communicate with it using a
21092 pipe. The @var{command} is a shell command, to be parsed and expanded
21093 by the system's command shell, @code{/bin/sh}; it should expect remote
21094 protocol packets on its standard input, and send replies on its
21095 standard output. You could use this to run a stand-alone simulator
21096 that speaks the remote debugging protocol, to make net connections
21097 using programs like @code{ssh}, or for other similar tricks.
21099 If @var{command} closes its standard output (perhaps by exiting),
21100 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
21101 program has already exited, this will have no effect.)
21105 @cindex interrupting remote programs
21106 @cindex remote programs, interrupting
21107 Whenever @value{GDBN} is waiting for the remote program, if you type the
21108 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
21109 program. This may or may not succeed, depending in part on the hardware
21110 and the serial drivers the remote system uses. If you type the
21111 interrupt character once again, @value{GDBN} displays this prompt:
21114 Interrupted while waiting for the program.
21115 Give up (and stop debugging it)? (y or n)
21118 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
21119 the remote debugging session. (If you decide you want to try again later,
21120 you can use @kbd{target remote} again to connect once more.) If you type
21121 @kbd{n}, @value{GDBN} goes back to waiting.
21123 In @code{target extended-remote} mode, typing @kbd{n} will leave
21124 @value{GDBN} connected to the target.
21127 @kindex detach (remote)
21129 When you have finished debugging the remote program, you can use the
21130 @code{detach} command to release it from @value{GDBN} control.
21131 Detaching from the target normally resumes its execution, but the results
21132 will depend on your particular remote stub. After the @code{detach}
21133 command in @code{target remote} mode, @value{GDBN} is free to connect to
21134 another target. In @code{target extended-remote} mode, @value{GDBN} is
21135 still connected to the target.
21139 The @code{disconnect} command closes the connection to the target, and
21140 the target is generally not resumed. It will wait for @value{GDBN}
21141 (this instance or another one) to connect and continue debugging. After
21142 the @code{disconnect} command, @value{GDBN} is again free to connect to
21145 @cindex send command to remote monitor
21146 @cindex extend @value{GDBN} for remote targets
21147 @cindex add new commands for external monitor
21149 @item monitor @var{cmd}
21150 This command allows you to send arbitrary commands directly to the
21151 remote monitor. Since @value{GDBN} doesn't care about the commands it
21152 sends like this, this command is the way to extend @value{GDBN}---you
21153 can add new commands that only the external monitor will understand
21157 @node File Transfer
21158 @section Sending files to a remote system
21159 @cindex remote target, file transfer
21160 @cindex file transfer
21161 @cindex sending files to remote systems
21163 Some remote targets offer the ability to transfer files over the same
21164 connection used to communicate with @value{GDBN}. This is convenient
21165 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
21166 running @code{gdbserver} over a network interface. For other targets,
21167 e.g.@: embedded devices with only a single serial port, this may be
21168 the only way to upload or download files.
21170 Not all remote targets support these commands.
21174 @item remote put @var{hostfile} @var{targetfile}
21175 Copy file @var{hostfile} from the host system (the machine running
21176 @value{GDBN}) to @var{targetfile} on the target system.
21179 @item remote get @var{targetfile} @var{hostfile}
21180 Copy file @var{targetfile} from the target system to @var{hostfile}
21181 on the host system.
21183 @kindex remote delete
21184 @item remote delete @var{targetfile}
21185 Delete @var{targetfile} from the target system.
21190 @section Using the @code{gdbserver} Program
21193 @cindex remote connection without stubs
21194 @code{gdbserver} is a control program for Unix-like systems, which
21195 allows you to connect your program with a remote @value{GDBN} via
21196 @code{target remote} or @code{target extended-remote}---but without
21197 linking in the usual debugging stub.
21199 @code{gdbserver} is not a complete replacement for the debugging stubs,
21200 because it requires essentially the same operating-system facilities
21201 that @value{GDBN} itself does. In fact, a system that can run
21202 @code{gdbserver} to connect to a remote @value{GDBN} could also run
21203 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
21204 because it is a much smaller program than @value{GDBN} itself. It is
21205 also easier to port than all of @value{GDBN}, so you may be able to get
21206 started more quickly on a new system by using @code{gdbserver}.
21207 Finally, if you develop code for real-time systems, you may find that
21208 the tradeoffs involved in real-time operation make it more convenient to
21209 do as much development work as possible on another system, for example
21210 by cross-compiling. You can use @code{gdbserver} to make a similar
21211 choice for debugging.
21213 @value{GDBN} and @code{gdbserver} communicate via either a serial line
21214 or a TCP connection, using the standard @value{GDBN} remote serial
21218 @emph{Warning:} @code{gdbserver} does not have any built-in security.
21219 Do not run @code{gdbserver} connected to any public network; a
21220 @value{GDBN} connection to @code{gdbserver} provides access to the
21221 target system with the same privileges as the user running
21225 @anchor{Running gdbserver}
21226 @subsection Running @code{gdbserver}
21227 @cindex arguments, to @code{gdbserver}
21228 @cindex @code{gdbserver}, command-line arguments
21230 Run @code{gdbserver} on the target system. You need a copy of the
21231 program you want to debug, including any libraries it requires.
21232 @code{gdbserver} does not need your program's symbol table, so you can
21233 strip the program if necessary to save space. @value{GDBN} on the host
21234 system does all the symbol handling.
21236 To use the server, you must tell it how to communicate with @value{GDBN};
21237 the name of your program; and the arguments for your program. The usual
21241 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
21244 @var{comm} is either a device name (to use a serial line), or a TCP
21245 hostname and portnumber, or @code{-} or @code{stdio} to use
21246 stdin/stdout of @code{gdbserver}.
21247 For example, to debug Emacs with the argument
21248 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
21252 target> gdbserver /dev/com1 emacs foo.txt
21255 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
21258 To use a TCP connection instead of a serial line:
21261 target> gdbserver host:2345 emacs foo.txt
21264 The only difference from the previous example is the first argument,
21265 specifying that you are communicating with the host @value{GDBN} via
21266 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
21267 expect a TCP connection from machine @samp{host} to local TCP port 2345.
21268 (Currently, the @samp{host} part is ignored.) You can choose any number
21269 you want for the port number as long as it does not conflict with any
21270 TCP ports already in use on the target system (for example, @code{23} is
21271 reserved for @code{telnet}).@footnote{If you choose a port number that
21272 conflicts with another service, @code{gdbserver} prints an error message
21273 and exits.} You must use the same port number with the host @value{GDBN}
21274 @code{target remote} command.
21276 The @code{stdio} connection is useful when starting @code{gdbserver}
21280 (gdb) target remote | ssh -T hostname gdbserver - hello
21283 The @samp{-T} option to ssh is provided because we don't need a remote pty,
21284 and we don't want escape-character handling. Ssh does this by default when
21285 a command is provided, the flag is provided to make it explicit.
21286 You could elide it if you want to.
21288 Programs started with stdio-connected gdbserver have @file{/dev/null} for
21289 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
21290 display through a pipe connected to gdbserver.
21291 Both @code{stdout} and @code{stderr} use the same pipe.
21293 @anchor{Attaching to a program}
21294 @subsubsection Attaching to a Running Program
21295 @cindex attach to a program, @code{gdbserver}
21296 @cindex @option{--attach}, @code{gdbserver} option
21298 On some targets, @code{gdbserver} can also attach to running programs.
21299 This is accomplished via the @code{--attach} argument. The syntax is:
21302 target> gdbserver --attach @var{comm} @var{pid}
21305 @var{pid} is the process ID of a currently running process. It isn't
21306 necessary to point @code{gdbserver} at a binary for the running process.
21308 In @code{target extended-remote} mode, you can also attach using the
21309 @value{GDBN} attach command
21310 (@pxref{Attaching in Types of Remote Connections}).
21313 You can debug processes by name instead of process ID if your target has the
21314 @code{pidof} utility:
21317 target> gdbserver --attach @var{comm} `pidof @var{program}`
21320 In case more than one copy of @var{program} is running, or @var{program}
21321 has multiple threads, most versions of @code{pidof} support the
21322 @code{-s} option to only return the first process ID.
21324 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
21326 This section applies only when @code{gdbserver} is run to listen on a TCP
21329 @code{gdbserver} normally terminates after all of its debugged processes have
21330 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
21331 extended-remote}, @code{gdbserver} stays running even with no processes left.
21332 @value{GDBN} normally terminates the spawned debugged process on its exit,
21333 which normally also terminates @code{gdbserver} in the @kbd{target remote}
21334 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
21335 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
21336 stays running even in the @kbd{target remote} mode.
21338 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
21339 Such reconnecting is useful for features like @ref{disconnected tracing}. For
21340 completeness, at most one @value{GDBN} can be connected at a time.
21342 @cindex @option{--once}, @code{gdbserver} option
21343 By default, @code{gdbserver} keeps the listening TCP port open, so that
21344 subsequent connections are possible. However, if you start @code{gdbserver}
21345 with the @option{--once} option, it will stop listening for any further
21346 connection attempts after connecting to the first @value{GDBN} session. This
21347 means no further connections to @code{gdbserver} will be possible after the
21348 first one. It also means @code{gdbserver} will terminate after the first
21349 connection with remote @value{GDBN} has closed, even for unexpectedly closed
21350 connections and even in the @kbd{target extended-remote} mode. The
21351 @option{--once} option allows reusing the same port number for connecting to
21352 multiple instances of @code{gdbserver} running on the same host, since each
21353 instance closes its port after the first connection.
21355 @anchor{Other Command-Line Arguments for gdbserver}
21356 @subsubsection Other Command-Line Arguments for @code{gdbserver}
21358 You can use the @option{--multi} option to start @code{gdbserver} without
21359 specifying a program to debug or a process to attach to. Then you can
21360 attach in @code{target extended-remote} mode and run or attach to a
21361 program. For more information,
21362 @pxref{--multi Option in Types of Remote Connnections}.
21364 @cindex @option{--debug}, @code{gdbserver} option
21365 The @option{--debug} option tells @code{gdbserver} to display extra
21366 status information about the debugging process.
21367 @cindex @option{--remote-debug}, @code{gdbserver} option
21368 The @option{--remote-debug} option tells @code{gdbserver} to display
21369 remote protocol debug output.
21370 @cindex @option{--debug-file}, @code{gdbserver} option
21371 @cindex @code{gdbserver}, send all debug output to a single file
21372 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
21373 write any debug output to the given @var{filename}. These options are intended
21374 for @code{gdbserver} development and for bug reports to the developers.
21376 @cindex @option{--debug-format}, @code{gdbserver} option
21377 The @option{--debug-format=option1[,option2,...]} option tells
21378 @code{gdbserver} to include additional information in each output.
21379 Possible options are:
21383 Turn off all extra information in debugging output.
21385 Turn on all extra information in debugging output.
21387 Include a timestamp in each line of debugging output.
21390 Options are processed in order. Thus, for example, if @option{none}
21391 appears last then no additional information is added to debugging output.
21393 @cindex @option{--wrapper}, @code{gdbserver} option
21394 The @option{--wrapper} option specifies a wrapper to launch programs
21395 for debugging. The option should be followed by the name of the
21396 wrapper, then any command-line arguments to pass to the wrapper, then
21397 @kbd{--} indicating the end of the wrapper arguments.
21399 @code{gdbserver} runs the specified wrapper program with a combined
21400 command line including the wrapper arguments, then the name of the
21401 program to debug, then any arguments to the program. The wrapper
21402 runs until it executes your program, and then @value{GDBN} gains control.
21404 You can use any program that eventually calls @code{execve} with
21405 its arguments as a wrapper. Several standard Unix utilities do
21406 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
21407 with @code{exec "$@@"} will also work.
21409 For example, you can use @code{env} to pass an environment variable to
21410 the debugged program, without setting the variable in @code{gdbserver}'s
21414 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
21417 @cindex @option{--selftest}
21418 The @option{--selftest} option runs the self tests in @code{gdbserver}:
21421 $ gdbserver --selftest
21422 Ran 2 unit tests, 0 failed
21425 These tests are disabled in release.
21426 @subsection Connecting to @code{gdbserver}
21428 The basic procedure for connecting to the remote target is:
21432 Run @value{GDBN} on the host system.
21435 Make sure you have the necessary symbol files
21436 (@pxref{Host and target files}).
21437 Load symbols for your application using the @code{file} command before you
21438 connect. Use @code{set sysroot} to locate target libraries (unless your
21439 @value{GDBN} was compiled with the correct sysroot using
21440 @code{--with-sysroot}).
21443 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
21444 For TCP connections, you must start up @code{gdbserver} prior to using
21445 the @code{target} command. Otherwise you may get an error whose
21446 text depends on the host system, but which usually looks something like
21447 @samp{Connection refused}. Don't use the @code{load}
21448 command in @value{GDBN} when using @code{target remote} mode, since the
21449 program is already on the target.
21453 @anchor{Monitor Commands for gdbserver}
21454 @subsection Monitor Commands for @code{gdbserver}
21455 @cindex monitor commands, for @code{gdbserver}
21457 During a @value{GDBN} session using @code{gdbserver}, you can use the
21458 @code{monitor} command to send special requests to @code{gdbserver}.
21459 Here are the available commands.
21463 List the available monitor commands.
21465 @item monitor set debug 0
21466 @itemx monitor set debug 1
21467 Disable or enable general debugging messages.
21469 @item monitor set remote-debug 0
21470 @itemx monitor set remote-debug 1
21471 Disable or enable specific debugging messages associated with the remote
21472 protocol (@pxref{Remote Protocol}).
21474 @item monitor set debug-file filename
21475 @itemx monitor set debug-file
21476 Send any debug output to the given file, or to stderr.
21478 @item monitor set debug-format option1@r{[},option2,...@r{]}
21479 Specify additional text to add to debugging messages.
21480 Possible options are:
21484 Turn off all extra information in debugging output.
21486 Turn on all extra information in debugging output.
21488 Include a timestamp in each line of debugging output.
21491 Options are processed in order. Thus, for example, if @option{none}
21492 appears last then no additional information is added to debugging output.
21494 @item monitor set libthread-db-search-path [PATH]
21495 @cindex gdbserver, search path for @code{libthread_db}
21496 When this command is issued, @var{path} is a colon-separated list of
21497 directories to search for @code{libthread_db} (@pxref{Threads,,set
21498 libthread-db-search-path}). If you omit @var{path},
21499 @samp{libthread-db-search-path} will be reset to its default value.
21501 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
21502 not supported in @code{gdbserver}.
21505 Tell gdbserver to exit immediately. This command should be followed by
21506 @code{disconnect} to close the debugging session. @code{gdbserver} will
21507 detach from any attached processes and kill any processes it created.
21508 Use @code{monitor exit} to terminate @code{gdbserver} at the end
21509 of a multi-process mode debug session.
21513 @subsection Tracepoints support in @code{gdbserver}
21514 @cindex tracepoints support in @code{gdbserver}
21516 On some targets, @code{gdbserver} supports tracepoints, fast
21517 tracepoints and static tracepoints.
21519 For fast or static tracepoints to work, a special library called the
21520 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
21521 This library is built and distributed as an integral part of
21522 @code{gdbserver}. In addition, support for static tracepoints
21523 requires building the in-process agent library with static tracepoints
21524 support. At present, the UST (LTTng Userspace Tracer,
21525 @url{http://lttng.org/ust}) tracing engine is supported. This support
21526 is automatically available if UST development headers are found in the
21527 standard include path when @code{gdbserver} is built, or if
21528 @code{gdbserver} was explicitly configured using @option{--with-ust}
21529 to point at such headers. You can explicitly disable the support
21530 using @option{--with-ust=no}.
21532 There are several ways to load the in-process agent in your program:
21535 @item Specifying it as dependency at link time
21537 You can link your program dynamically with the in-process agent
21538 library. On most systems, this is accomplished by adding
21539 @code{-linproctrace} to the link command.
21541 @item Using the system's preloading mechanisms
21543 You can force loading the in-process agent at startup time by using
21544 your system's support for preloading shared libraries. Many Unixes
21545 support the concept of preloading user defined libraries. In most
21546 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
21547 in the environment. See also the description of @code{gdbserver}'s
21548 @option{--wrapper} command line option.
21550 @item Using @value{GDBN} to force loading the agent at run time
21552 On some systems, you can force the inferior to load a shared library,
21553 by calling a dynamic loader function in the inferior that takes care
21554 of dynamically looking up and loading a shared library. On most Unix
21555 systems, the function is @code{dlopen}. You'll use the @code{call}
21556 command for that. For example:
21559 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
21562 Note that on most Unix systems, for the @code{dlopen} function to be
21563 available, the program needs to be linked with @code{-ldl}.
21566 On systems that have a userspace dynamic loader, like most Unix
21567 systems, when you connect to @code{gdbserver} using @code{target
21568 remote}, you'll find that the program is stopped at the dynamic
21569 loader's entry point, and no shared library has been loaded in the
21570 program's address space yet, including the in-process agent. In that
21571 case, before being able to use any of the fast or static tracepoints
21572 features, you need to let the loader run and load the shared
21573 libraries. The simplest way to do that is to run the program to the
21574 main procedure. E.g., if debugging a C or C@t{++} program, start
21575 @code{gdbserver} like so:
21578 $ gdbserver :9999 myprogram
21581 Start GDB and connect to @code{gdbserver} like so, and run to main:
21585 (@value{GDBP}) target remote myhost:9999
21586 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
21587 (@value{GDBP}) b main
21588 (@value{GDBP}) continue
21591 The in-process tracing agent library should now be loaded into the
21592 process; you can confirm it with the @code{info sharedlibrary}
21593 command, which will list @file{libinproctrace.so} as loaded in the
21594 process. You are now ready to install fast tracepoints, list static
21595 tracepoint markers, probe static tracepoints markers, and start
21598 @node Remote Configuration
21599 @section Remote Configuration
21602 @kindex show remote
21603 This section documents the configuration options available when
21604 debugging remote programs. For the options related to the File I/O
21605 extensions of the remote protocol, see @ref{system,
21606 system-call-allowed}.
21609 @item set remoteaddresssize @var{bits}
21610 @cindex address size for remote targets
21611 @cindex bits in remote address
21612 Set the maximum size of address in a memory packet to the specified
21613 number of bits. @value{GDBN} will mask off the address bits above
21614 that number, when it passes addresses to the remote target. The
21615 default value is the number of bits in the target's address.
21617 @item show remoteaddresssize
21618 Show the current value of remote address size in bits.
21620 @item set serial baud @var{n}
21621 @cindex baud rate for remote targets
21622 Set the baud rate for the remote serial I/O to @var{n} baud. The
21623 value is used to set the speed of the serial port used for debugging
21626 @item show serial baud
21627 Show the current speed of the remote connection.
21629 @item set serial parity @var{parity}
21630 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
21631 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
21633 @item show serial parity
21634 Show the current parity of the serial port.
21636 @item set remotebreak
21637 @cindex interrupt remote programs
21638 @cindex BREAK signal instead of Ctrl-C
21639 @anchor{set remotebreak}
21640 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
21641 when you type @kbd{Ctrl-c} to interrupt the program running
21642 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
21643 character instead. The default is off, since most remote systems
21644 expect to see @samp{Ctrl-C} as the interrupt signal.
21646 @item show remotebreak
21647 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
21648 interrupt the remote program.
21650 @item set remoteflow on
21651 @itemx set remoteflow off
21652 @kindex set remoteflow
21653 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
21654 on the serial port used to communicate to the remote target.
21656 @item show remoteflow
21657 @kindex show remoteflow
21658 Show the current setting of hardware flow control.
21660 @item set remotelogbase @var{base}
21661 Set the base (a.k.a.@: radix) of logging serial protocol
21662 communications to @var{base}. Supported values of @var{base} are:
21663 @code{ascii}, @code{octal}, and @code{hex}. The default is
21666 @item show remotelogbase
21667 Show the current setting of the radix for logging remote serial
21670 @item set remotelogfile @var{file}
21671 @cindex record serial communications on file
21672 Record remote serial communications on the named @var{file}. The
21673 default is not to record at all.
21675 @item show remotelogfile
21676 Show the current setting of the file name on which to record the
21677 serial communications.
21679 @item set remotetimeout @var{num}
21680 @cindex timeout for serial communications
21681 @cindex remote timeout
21682 Set the timeout limit to wait for the remote target to respond to
21683 @var{num} seconds. The default is 2 seconds.
21685 @item show remotetimeout
21686 Show the current number of seconds to wait for the remote target
21689 @cindex limit hardware breakpoints and watchpoints
21690 @cindex remote target, limit break- and watchpoints
21691 @anchor{set remote hardware-watchpoint-limit}
21692 @anchor{set remote hardware-breakpoint-limit}
21693 @item set remote hardware-watchpoint-limit @var{limit}
21694 @itemx set remote hardware-breakpoint-limit @var{limit}
21695 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
21696 or breakpoints. The @var{limit} can be set to 0 to disable hardware
21697 watchpoints or breakpoints, and @code{unlimited} for unlimited
21698 watchpoints or breakpoints.
21700 @item show remote hardware-watchpoint-limit
21701 @itemx show remote hardware-breakpoint-limit
21702 Show the current limit for the number of hardware watchpoints or
21703 breakpoints that @value{GDBN} can use.
21705 @cindex limit hardware watchpoints length
21706 @cindex remote target, limit watchpoints length
21707 @anchor{set remote hardware-watchpoint-length-limit}
21708 @item set remote hardware-watchpoint-length-limit @var{limit}
21709 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
21710 length of a remote hardware watchpoint. A @var{limit} of 0 disables
21711 hardware watchpoints and @code{unlimited} allows watchpoints of any
21714 @item show remote hardware-watchpoint-length-limit
21715 Show the current limit (in bytes) of the maximum length of
21716 a remote hardware watchpoint.
21718 @item set remote exec-file @var{filename}
21719 @itemx show remote exec-file
21720 @anchor{set remote exec-file}
21721 @cindex executable file, for remote target
21722 Select the file used for @code{run} with @code{target
21723 extended-remote}. This should be set to a filename valid on the
21724 target system. If it is not set, the target will use a default
21725 filename (e.g.@: the last program run).
21727 @item set remote interrupt-sequence
21728 @cindex interrupt remote programs
21729 @cindex select Ctrl-C, BREAK or BREAK-g
21730 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
21731 @samp{BREAK-g} as the
21732 sequence to the remote target in order to interrupt the execution.
21733 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
21734 is high level of serial line for some certain time.
21735 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
21736 It is @code{BREAK} signal followed by character @code{g}.
21738 @item show interrupt-sequence
21739 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
21740 is sent by @value{GDBN} to interrupt the remote program.
21741 @code{BREAK-g} is BREAK signal followed by @code{g} and
21742 also known as Magic SysRq g.
21744 @item set remote interrupt-on-connect
21745 @cindex send interrupt-sequence on start
21746 Specify whether interrupt-sequence is sent to remote target when
21747 @value{GDBN} connects to it. This is mostly needed when you debug
21748 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
21749 which is known as Magic SysRq g in order to connect @value{GDBN}.
21751 @item show interrupt-on-connect
21752 Show whether interrupt-sequence is sent
21753 to remote target when @value{GDBN} connects to it.
21757 @item set tcp auto-retry on
21758 @cindex auto-retry, for remote TCP target
21759 Enable auto-retry for remote TCP connections. This is useful if the remote
21760 debugging agent is launched in parallel with @value{GDBN}; there is a race
21761 condition because the agent may not become ready to accept the connection
21762 before @value{GDBN} attempts to connect. When auto-retry is
21763 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
21764 to establish the connection using the timeout specified by
21765 @code{set tcp connect-timeout}.
21767 @item set tcp auto-retry off
21768 Do not auto-retry failed TCP connections.
21770 @item show tcp auto-retry
21771 Show the current auto-retry setting.
21773 @item set tcp connect-timeout @var{seconds}
21774 @itemx set tcp connect-timeout unlimited
21775 @cindex connection timeout, for remote TCP target
21776 @cindex timeout, for remote target connection
21777 Set the timeout for establishing a TCP connection to the remote target to
21778 @var{seconds}. The timeout affects both polling to retry failed connections
21779 (enabled by @code{set tcp auto-retry on}) and waiting for connections
21780 that are merely slow to complete, and represents an approximate cumulative
21781 value. If @var{seconds} is @code{unlimited}, there is no timeout and
21782 @value{GDBN} will keep attempting to establish a connection forever,
21783 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
21785 @item show tcp connect-timeout
21786 Show the current connection timeout setting.
21789 @cindex remote packets, enabling and disabling
21790 The @value{GDBN} remote protocol autodetects the packets supported by
21791 your debugging stub. If you need to override the autodetection, you
21792 can use these commands to enable or disable individual packets. Each
21793 packet can be set to @samp{on} (the remote target supports this
21794 packet), @samp{off} (the remote target does not support this packet),
21795 or @samp{auto} (detect remote target support for this packet). They
21796 all default to @samp{auto}. For more information about each packet,
21797 see @ref{Remote Protocol}.
21799 During normal use, you should not have to use any of these commands.
21800 If you do, that may be a bug in your remote debugging stub, or a bug
21801 in @value{GDBN}. You may want to report the problem to the
21802 @value{GDBN} developers.
21804 For each packet @var{name}, the command to enable or disable the
21805 packet is @code{set remote @var{name}-packet}. The available settings
21808 @multitable @columnfractions 0.28 0.32 0.25
21811 @tab Related Features
21813 @item @code{fetch-register}
21815 @tab @code{info registers}
21817 @item @code{set-register}
21821 @item @code{binary-download}
21823 @tab @code{load}, @code{set}
21825 @item @code{read-aux-vector}
21826 @tab @code{qXfer:auxv:read}
21827 @tab @code{info auxv}
21829 @item @code{symbol-lookup}
21830 @tab @code{qSymbol}
21831 @tab Detecting multiple threads
21833 @item @code{attach}
21834 @tab @code{vAttach}
21837 @item @code{verbose-resume}
21839 @tab Stepping or resuming multiple threads
21845 @item @code{software-breakpoint}
21849 @item @code{hardware-breakpoint}
21853 @item @code{write-watchpoint}
21857 @item @code{read-watchpoint}
21861 @item @code{access-watchpoint}
21865 @item @code{pid-to-exec-file}
21866 @tab @code{qXfer:exec-file:read}
21867 @tab @code{attach}, @code{run}
21869 @item @code{target-features}
21870 @tab @code{qXfer:features:read}
21871 @tab @code{set architecture}
21873 @item @code{library-info}
21874 @tab @code{qXfer:libraries:read}
21875 @tab @code{info sharedlibrary}
21877 @item @code{memory-map}
21878 @tab @code{qXfer:memory-map:read}
21879 @tab @code{info mem}
21881 @item @code{read-sdata-object}
21882 @tab @code{qXfer:sdata:read}
21883 @tab @code{print $_sdata}
21885 @item @code{read-spu-object}
21886 @tab @code{qXfer:spu:read}
21887 @tab @code{info spu}
21889 @item @code{write-spu-object}
21890 @tab @code{qXfer:spu:write}
21891 @tab @code{info spu}
21893 @item @code{read-siginfo-object}
21894 @tab @code{qXfer:siginfo:read}
21895 @tab @code{print $_siginfo}
21897 @item @code{write-siginfo-object}
21898 @tab @code{qXfer:siginfo:write}
21899 @tab @code{set $_siginfo}
21901 @item @code{threads}
21902 @tab @code{qXfer:threads:read}
21903 @tab @code{info threads}
21905 @item @code{get-thread-local-@*storage-address}
21906 @tab @code{qGetTLSAddr}
21907 @tab Displaying @code{__thread} variables
21909 @item @code{get-thread-information-block-address}
21910 @tab @code{qGetTIBAddr}
21911 @tab Display MS-Windows Thread Information Block.
21913 @item @code{search-memory}
21914 @tab @code{qSearch:memory}
21917 @item @code{supported-packets}
21918 @tab @code{qSupported}
21919 @tab Remote communications parameters
21921 @item @code{catch-syscalls}
21922 @tab @code{QCatchSyscalls}
21923 @tab @code{catch syscall}
21925 @item @code{pass-signals}
21926 @tab @code{QPassSignals}
21927 @tab @code{handle @var{signal}}
21929 @item @code{program-signals}
21930 @tab @code{QProgramSignals}
21931 @tab @code{handle @var{signal}}
21933 @item @code{hostio-close-packet}
21934 @tab @code{vFile:close}
21935 @tab @code{remote get}, @code{remote put}
21937 @item @code{hostio-open-packet}
21938 @tab @code{vFile:open}
21939 @tab @code{remote get}, @code{remote put}
21941 @item @code{hostio-pread-packet}
21942 @tab @code{vFile:pread}
21943 @tab @code{remote get}, @code{remote put}
21945 @item @code{hostio-pwrite-packet}
21946 @tab @code{vFile:pwrite}
21947 @tab @code{remote get}, @code{remote put}
21949 @item @code{hostio-unlink-packet}
21950 @tab @code{vFile:unlink}
21951 @tab @code{remote delete}
21953 @item @code{hostio-readlink-packet}
21954 @tab @code{vFile:readlink}
21957 @item @code{hostio-fstat-packet}
21958 @tab @code{vFile:fstat}
21961 @item @code{hostio-setfs-packet}
21962 @tab @code{vFile:setfs}
21965 @item @code{noack-packet}
21966 @tab @code{QStartNoAckMode}
21967 @tab Packet acknowledgment
21969 @item @code{osdata}
21970 @tab @code{qXfer:osdata:read}
21971 @tab @code{info os}
21973 @item @code{query-attached}
21974 @tab @code{qAttached}
21975 @tab Querying remote process attach state.
21977 @item @code{trace-buffer-size}
21978 @tab @code{QTBuffer:size}
21979 @tab @code{set trace-buffer-size}
21981 @item @code{trace-status}
21982 @tab @code{qTStatus}
21983 @tab @code{tstatus}
21985 @item @code{traceframe-info}
21986 @tab @code{qXfer:traceframe-info:read}
21987 @tab Traceframe info
21989 @item @code{install-in-trace}
21990 @tab @code{InstallInTrace}
21991 @tab Install tracepoint in tracing
21993 @item @code{disable-randomization}
21994 @tab @code{QDisableRandomization}
21995 @tab @code{set disable-randomization}
21997 @item @code{startup-with-shell}
21998 @tab @code{QStartupWithShell}
21999 @tab @code{set startup-with-shell}
22001 @item @code{environment-hex-encoded}
22002 @tab @code{QEnvironmentHexEncoded}
22003 @tab @code{set environment}
22005 @item @code{environment-unset}
22006 @tab @code{QEnvironmentUnset}
22007 @tab @code{unset environment}
22009 @item @code{environment-reset}
22010 @tab @code{QEnvironmentReset}
22011 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
22013 @item @code{set-working-dir}
22014 @tab @code{QSetWorkingDir}
22015 @tab @code{set cwd}
22017 @item @code{conditional-breakpoints-packet}
22018 @tab @code{Z0 and Z1}
22019 @tab @code{Support for target-side breakpoint condition evaluation}
22021 @item @code{multiprocess-extensions}
22022 @tab @code{multiprocess extensions}
22023 @tab Debug multiple processes and remote process PID awareness
22025 @item @code{swbreak-feature}
22026 @tab @code{swbreak stop reason}
22029 @item @code{hwbreak-feature}
22030 @tab @code{hwbreak stop reason}
22033 @item @code{fork-event-feature}
22034 @tab @code{fork stop reason}
22037 @item @code{vfork-event-feature}
22038 @tab @code{vfork stop reason}
22041 @item @code{exec-event-feature}
22042 @tab @code{exec stop reason}
22045 @item @code{thread-events}
22046 @tab @code{QThreadEvents}
22047 @tab Tracking thread lifetime.
22049 @item @code{no-resumed-stop-reply}
22050 @tab @code{no resumed thread left stop reply}
22051 @tab Tracking thread lifetime.
22056 @section Implementing a Remote Stub
22058 @cindex debugging stub, example
22059 @cindex remote stub, example
22060 @cindex stub example, remote debugging
22061 The stub files provided with @value{GDBN} implement the target side of the
22062 communication protocol, and the @value{GDBN} side is implemented in the
22063 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
22064 these subroutines to communicate, and ignore the details. (If you're
22065 implementing your own stub file, you can still ignore the details: start
22066 with one of the existing stub files. @file{sparc-stub.c} is the best
22067 organized, and therefore the easiest to read.)
22069 @cindex remote serial debugging, overview
22070 To debug a program running on another machine (the debugging
22071 @dfn{target} machine), you must first arrange for all the usual
22072 prerequisites for the program to run by itself. For example, for a C
22077 A startup routine to set up the C runtime environment; these usually
22078 have a name like @file{crt0}. The startup routine may be supplied by
22079 your hardware supplier, or you may have to write your own.
22082 A C subroutine library to support your program's
22083 subroutine calls, notably managing input and output.
22086 A way of getting your program to the other machine---for example, a
22087 download program. These are often supplied by the hardware
22088 manufacturer, but you may have to write your own from hardware
22092 The next step is to arrange for your program to use a serial port to
22093 communicate with the machine where @value{GDBN} is running (the @dfn{host}
22094 machine). In general terms, the scheme looks like this:
22098 @value{GDBN} already understands how to use this protocol; when everything
22099 else is set up, you can simply use the @samp{target remote} command
22100 (@pxref{Targets,,Specifying a Debugging Target}).
22102 @item On the target,
22103 you must link with your program a few special-purpose subroutines that
22104 implement the @value{GDBN} remote serial protocol. The file containing these
22105 subroutines is called a @dfn{debugging stub}.
22107 On certain remote targets, you can use an auxiliary program
22108 @code{gdbserver} instead of linking a stub into your program.
22109 @xref{Server,,Using the @code{gdbserver} Program}, for details.
22112 The debugging stub is specific to the architecture of the remote
22113 machine; for example, use @file{sparc-stub.c} to debug programs on
22116 @cindex remote serial stub list
22117 These working remote stubs are distributed with @value{GDBN}:
22122 @cindex @file{i386-stub.c}
22125 For Intel 386 and compatible architectures.
22128 @cindex @file{m68k-stub.c}
22129 @cindex Motorola 680x0
22131 For Motorola 680x0 architectures.
22134 @cindex @file{sh-stub.c}
22137 For Renesas SH architectures.
22140 @cindex @file{sparc-stub.c}
22142 For @sc{sparc} architectures.
22144 @item sparcl-stub.c
22145 @cindex @file{sparcl-stub.c}
22148 For Fujitsu @sc{sparclite} architectures.
22152 The @file{README} file in the @value{GDBN} distribution may list other
22153 recently added stubs.
22156 * Stub Contents:: What the stub can do for you
22157 * Bootstrapping:: What you must do for the stub
22158 * Debug Session:: Putting it all together
22161 @node Stub Contents
22162 @subsection What the Stub Can Do for You
22164 @cindex remote serial stub
22165 The debugging stub for your architecture supplies these three
22169 @item set_debug_traps
22170 @findex set_debug_traps
22171 @cindex remote serial stub, initialization
22172 This routine arranges for @code{handle_exception} to run when your
22173 program stops. You must call this subroutine explicitly in your
22174 program's startup code.
22176 @item handle_exception
22177 @findex handle_exception
22178 @cindex remote serial stub, main routine
22179 This is the central workhorse, but your program never calls it
22180 explicitly---the setup code arranges for @code{handle_exception} to
22181 run when a trap is triggered.
22183 @code{handle_exception} takes control when your program stops during
22184 execution (for example, on a breakpoint), and mediates communications
22185 with @value{GDBN} on the host machine. This is where the communications
22186 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
22187 representative on the target machine. It begins by sending summary
22188 information on the state of your program, then continues to execute,
22189 retrieving and transmitting any information @value{GDBN} needs, until you
22190 execute a @value{GDBN} command that makes your program resume; at that point,
22191 @code{handle_exception} returns control to your own code on the target
22195 @cindex @code{breakpoint} subroutine, remote
22196 Use this auxiliary subroutine to make your program contain a
22197 breakpoint. Depending on the particular situation, this may be the only
22198 way for @value{GDBN} to get control. For instance, if your target
22199 machine has some sort of interrupt button, you won't need to call this;
22200 pressing the interrupt button transfers control to
22201 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
22202 simply receiving characters on the serial port may also trigger a trap;
22203 again, in that situation, you don't need to call @code{breakpoint} from
22204 your own program---simply running @samp{target remote} from the host
22205 @value{GDBN} session gets control.
22207 Call @code{breakpoint} if none of these is true, or if you simply want
22208 to make certain your program stops at a predetermined point for the
22209 start of your debugging session.
22212 @node Bootstrapping
22213 @subsection What You Must Do for the Stub
22215 @cindex remote stub, support routines
22216 The debugging stubs that come with @value{GDBN} are set up for a particular
22217 chip architecture, but they have no information about the rest of your
22218 debugging target machine.
22220 First of all you need to tell the stub how to communicate with the
22224 @item int getDebugChar()
22225 @findex getDebugChar
22226 Write this subroutine to read a single character from the serial port.
22227 It may be identical to @code{getchar} for your target system; a
22228 different name is used to allow you to distinguish the two if you wish.
22230 @item void putDebugChar(int)
22231 @findex putDebugChar
22232 Write this subroutine to write a single character to the serial port.
22233 It may be identical to @code{putchar} for your target system; a
22234 different name is used to allow you to distinguish the two if you wish.
22237 @cindex control C, and remote debugging
22238 @cindex interrupting remote targets
22239 If you want @value{GDBN} to be able to stop your program while it is
22240 running, you need to use an interrupt-driven serial driver, and arrange
22241 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
22242 character). That is the character which @value{GDBN} uses to tell the
22243 remote system to stop.
22245 Getting the debugging target to return the proper status to @value{GDBN}
22246 probably requires changes to the standard stub; one quick and dirty way
22247 is to just execute a breakpoint instruction (the ``dirty'' part is that
22248 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
22250 Other routines you need to supply are:
22253 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
22254 @findex exceptionHandler
22255 Write this function to install @var{exception_address} in the exception
22256 handling tables. You need to do this because the stub does not have any
22257 way of knowing what the exception handling tables on your target system
22258 are like (for example, the processor's table might be in @sc{rom},
22259 containing entries which point to a table in @sc{ram}).
22260 The @var{exception_number} specifies the exception which should be changed;
22261 its meaning is architecture-dependent (for example, different numbers
22262 might represent divide by zero, misaligned access, etc). When this
22263 exception occurs, control should be transferred directly to
22264 @var{exception_address}, and the processor state (stack, registers,
22265 and so on) should be just as it is when a processor exception occurs. So if
22266 you want to use a jump instruction to reach @var{exception_address}, it
22267 should be a simple jump, not a jump to subroutine.
22269 For the 386, @var{exception_address} should be installed as an interrupt
22270 gate so that interrupts are masked while the handler runs. The gate
22271 should be at privilege level 0 (the most privileged level). The
22272 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
22273 help from @code{exceptionHandler}.
22275 @item void flush_i_cache()
22276 @findex flush_i_cache
22277 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
22278 instruction cache, if any, on your target machine. If there is no
22279 instruction cache, this subroutine may be a no-op.
22281 On target machines that have instruction caches, @value{GDBN} requires this
22282 function to make certain that the state of your program is stable.
22286 You must also make sure this library routine is available:
22289 @item void *memset(void *, int, int)
22291 This is the standard library function @code{memset} that sets an area of
22292 memory to a known value. If you have one of the free versions of
22293 @code{libc.a}, @code{memset} can be found there; otherwise, you must
22294 either obtain it from your hardware manufacturer, or write your own.
22297 If you do not use the GNU C compiler, you may need other standard
22298 library subroutines as well; this varies from one stub to another,
22299 but in general the stubs are likely to use any of the common library
22300 subroutines which @code{@value{NGCC}} generates as inline code.
22303 @node Debug Session
22304 @subsection Putting it All Together
22306 @cindex remote serial debugging summary
22307 In summary, when your program is ready to debug, you must follow these
22312 Make sure you have defined the supporting low-level routines
22313 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
22315 @code{getDebugChar}, @code{putDebugChar},
22316 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
22320 Insert these lines in your program's startup code, before the main
22321 procedure is called:
22328 On some machines, when a breakpoint trap is raised, the hardware
22329 automatically makes the PC point to the instruction after the
22330 breakpoint. If your machine doesn't do that, you may need to adjust
22331 @code{handle_exception} to arrange for it to return to the instruction
22332 after the breakpoint on this first invocation, so that your program
22333 doesn't keep hitting the initial breakpoint instead of making
22337 For the 680x0 stub only, you need to provide a variable called
22338 @code{exceptionHook}. Normally you just use:
22341 void (*exceptionHook)() = 0;
22345 but if before calling @code{set_debug_traps}, you set it to point to a
22346 function in your program, that function is called when
22347 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
22348 error). The function indicated by @code{exceptionHook} is called with
22349 one parameter: an @code{int} which is the exception number.
22352 Compile and link together: your program, the @value{GDBN} debugging stub for
22353 your target architecture, and the supporting subroutines.
22356 Make sure you have a serial connection between your target machine and
22357 the @value{GDBN} host, and identify the serial port on the host.
22360 @c The "remote" target now provides a `load' command, so we should
22361 @c document that. FIXME.
22362 Download your program to your target machine (or get it there by
22363 whatever means the manufacturer provides), and start it.
22366 Start @value{GDBN} on the host, and connect to the target
22367 (@pxref{Connecting,,Connecting to a Remote Target}).
22371 @node Configurations
22372 @chapter Configuration-Specific Information
22374 While nearly all @value{GDBN} commands are available for all native and
22375 cross versions of the debugger, there are some exceptions. This chapter
22376 describes things that are only available in certain configurations.
22378 There are three major categories of configurations: native
22379 configurations, where the host and target are the same, embedded
22380 operating system configurations, which are usually the same for several
22381 different processor architectures, and bare embedded processors, which
22382 are quite different from each other.
22387 * Embedded Processors::
22394 This section describes details specific to particular native
22398 * BSD libkvm Interface:: Debugging BSD kernel memory images
22399 * Process Information:: Process information
22400 * DJGPP Native:: Features specific to the DJGPP port
22401 * Cygwin Native:: Features specific to the Cygwin port
22402 * Hurd Native:: Features specific to @sc{gnu} Hurd
22403 * Darwin:: Features specific to Darwin
22404 * FreeBSD:: Features specific to FreeBSD
22407 @node BSD libkvm Interface
22408 @subsection BSD libkvm Interface
22411 @cindex kernel memory image
22412 @cindex kernel crash dump
22414 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
22415 interface that provides a uniform interface for accessing kernel virtual
22416 memory images, including live systems and crash dumps. @value{GDBN}
22417 uses this interface to allow you to debug live kernels and kernel crash
22418 dumps on many native BSD configurations. This is implemented as a
22419 special @code{kvm} debugging target. For debugging a live system, load
22420 the currently running kernel into @value{GDBN} and connect to the
22424 (@value{GDBP}) @b{target kvm}
22427 For debugging crash dumps, provide the file name of the crash dump as an
22431 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
22434 Once connected to the @code{kvm} target, the following commands are
22440 Set current context from the @dfn{Process Control Block} (PCB) address.
22443 Set current context from proc address. This command isn't available on
22444 modern FreeBSD systems.
22447 @node Process Information
22448 @subsection Process Information
22450 @cindex examine process image
22451 @cindex process info via @file{/proc}
22453 Some operating systems provide interfaces to fetch additional
22454 information about running processes beyond memory and per-thread
22455 register state. If @value{GDBN} is configured for an operating system
22456 with a supported interface, the command @code{info proc} is available
22457 to report information about the process running your program, or about
22458 any process running on your system.
22460 One supported interface is a facility called @samp{/proc} that can be
22461 used to examine the image of a running process using file-system
22462 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
22465 On FreeBSD systems, system control nodes are used to query process
22468 In addition, some systems may provide additional process information
22469 in core files. Note that a core file may include a subset of the
22470 information available from a live process. Process information is
22471 currently avaiable from cores created on @sc{gnu}/Linux and FreeBSD
22478 @itemx info proc @var{process-id}
22479 Summarize available information about a process. If a
22480 process ID is specified by @var{process-id}, display information about
22481 that process; otherwise display information about the program being
22482 debugged. The summary includes the debugged process ID, the command
22483 line used to invoke it, its current working directory, and its
22484 executable file's absolute file name.
22486 On some systems, @var{process-id} can be of the form
22487 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
22488 within a process. If the optional @var{pid} part is missing, it means
22489 a thread from the process being debugged (the leading @samp{/} still
22490 needs to be present, or else @value{GDBN} will interpret the number as
22491 a process ID rather than a thread ID).
22493 @item info proc cmdline
22494 @cindex info proc cmdline
22495 Show the original command line of the process. This command is
22496 supported on @sc{gnu}/Linux and FreeBSD.
22498 @item info proc cwd
22499 @cindex info proc cwd
22500 Show the current working directory of the process. This command is
22501 supported on @sc{gnu}/Linux and FreeBSD.
22503 @item info proc exe
22504 @cindex info proc exe
22505 Show the name of executable of the process. This command is supported
22506 on @sc{gnu}/Linux and FreeBSD.
22508 @item info proc files
22509 @cindex info proc files
22510 Show the file descriptors open by the process. For each open file
22511 descriptor, @value{GDBN} shows its number, type (file, directory,
22512 character device, socket), file pointer offset, and the name of the
22513 resource open on the descriptor. The resource name can be a file name
22514 (for files, directories, and devices) or a protocol followed by socket
22515 address (for network connections). This command is supported on
22518 This example shows the open file descriptors for a process using a
22519 tty for standard input and output as well as two network sockets:
22522 (gdb) info proc files 22136
22526 FD Type Offset Flags Name
22527 text file - r-------- /usr/bin/ssh
22528 ctty chr - rw------- /dev/pts/20
22529 cwd dir - r-------- /usr/home/john
22530 root dir - r-------- /
22531 0 chr 0x32933a4 rw------- /dev/pts/20
22532 1 chr 0x32933a4 rw------- /dev/pts/20
22533 2 chr 0x32933a4 rw------- /dev/pts/20
22534 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
22535 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
22538 @item info proc mappings
22539 @cindex memory address space mappings
22540 Report the memory address space ranges accessible in a process. On
22541 Solaris and FreeBSD systems, each memory range includes information on
22542 whether the process has read, write, or execute access rights to each
22543 range. On @sc{gnu}/Linux and FreeBSD systems, each memory range
22544 includes the object file which is mapped to that range.
22546 @item info proc stat
22547 @itemx info proc status
22548 @cindex process detailed status information
22549 Show additional process-related information, including the user ID and
22550 group ID; virtual memory usage; the signals that are pending, blocked,
22551 and ignored; its TTY; its consumption of system and user time; its
22552 stack size; its @samp{nice} value; etc. These commands are supported
22553 on @sc{gnu}/Linux and FreeBSD.
22555 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
22556 information (type @kbd{man 5 proc} from your shell prompt).
22558 For FreeBSD systems, @code{info proc stat} is an alias for @code{info
22561 @item info proc all
22562 Show all the information about the process described under all of the
22563 above @code{info proc} subcommands.
22566 @comment These sub-options of 'info proc' were not included when
22567 @comment procfs.c was re-written. Keep their descriptions around
22568 @comment against the day when someone finds the time to put them back in.
22569 @kindex info proc times
22570 @item info proc times
22571 Starting time, user CPU time, and system CPU time for your program and
22574 @kindex info proc id
22576 Report on the process IDs related to your program: its own process ID,
22577 the ID of its parent, the process group ID, and the session ID.
22580 @item set procfs-trace
22581 @kindex set procfs-trace
22582 @cindex @code{procfs} API calls
22583 This command enables and disables tracing of @code{procfs} API calls.
22585 @item show procfs-trace
22586 @kindex show procfs-trace
22587 Show the current state of @code{procfs} API call tracing.
22589 @item set procfs-file @var{file}
22590 @kindex set procfs-file
22591 Tell @value{GDBN} to write @code{procfs} API trace to the named
22592 @var{file}. @value{GDBN} appends the trace info to the previous
22593 contents of the file. The default is to display the trace on the
22596 @item show procfs-file
22597 @kindex show procfs-file
22598 Show the file to which @code{procfs} API trace is written.
22600 @item proc-trace-entry
22601 @itemx proc-trace-exit
22602 @itemx proc-untrace-entry
22603 @itemx proc-untrace-exit
22604 @kindex proc-trace-entry
22605 @kindex proc-trace-exit
22606 @kindex proc-untrace-entry
22607 @kindex proc-untrace-exit
22608 These commands enable and disable tracing of entries into and exits
22609 from the @code{syscall} interface.
22612 @kindex info pidlist
22613 @cindex process list, QNX Neutrino
22614 For QNX Neutrino only, this command displays the list of all the
22615 processes and all the threads within each process.
22618 @kindex info meminfo
22619 @cindex mapinfo list, QNX Neutrino
22620 For QNX Neutrino only, this command displays the list of all mapinfos.
22624 @subsection Features for Debugging @sc{djgpp} Programs
22625 @cindex @sc{djgpp} debugging
22626 @cindex native @sc{djgpp} debugging
22627 @cindex MS-DOS-specific commands
22630 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
22631 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
22632 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
22633 top of real-mode DOS systems and their emulations.
22635 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
22636 defines a few commands specific to the @sc{djgpp} port. This
22637 subsection describes those commands.
22642 This is a prefix of @sc{djgpp}-specific commands which print
22643 information about the target system and important OS structures.
22646 @cindex MS-DOS system info
22647 @cindex free memory information (MS-DOS)
22648 @item info dos sysinfo
22649 This command displays assorted information about the underlying
22650 platform: the CPU type and features, the OS version and flavor, the
22651 DPMI version, and the available conventional and DPMI memory.
22656 @cindex segment descriptor tables
22657 @cindex descriptor tables display
22659 @itemx info dos ldt
22660 @itemx info dos idt
22661 These 3 commands display entries from, respectively, Global, Local,
22662 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
22663 tables are data structures which store a descriptor for each segment
22664 that is currently in use. The segment's selector is an index into a
22665 descriptor table; the table entry for that index holds the
22666 descriptor's base address and limit, and its attributes and access
22669 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
22670 segment (used for both data and the stack), and a DOS segment (which
22671 allows access to DOS/BIOS data structures and absolute addresses in
22672 conventional memory). However, the DPMI host will usually define
22673 additional segments in order to support the DPMI environment.
22675 @cindex garbled pointers
22676 These commands allow to display entries from the descriptor tables.
22677 Without an argument, all entries from the specified table are
22678 displayed. An argument, which should be an integer expression, means
22679 display a single entry whose index is given by the argument. For
22680 example, here's a convenient way to display information about the
22681 debugged program's data segment:
22684 @exdent @code{(@value{GDBP}) info dos ldt $ds}
22685 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
22689 This comes in handy when you want to see whether a pointer is outside
22690 the data segment's limit (i.e.@: @dfn{garbled}).
22692 @cindex page tables display (MS-DOS)
22694 @itemx info dos pte
22695 These two commands display entries from, respectively, the Page
22696 Directory and the Page Tables. Page Directories and Page Tables are
22697 data structures which control how virtual memory addresses are mapped
22698 into physical addresses. A Page Table includes an entry for every
22699 page of memory that is mapped into the program's address space; there
22700 may be several Page Tables, each one holding up to 4096 entries. A
22701 Page Directory has up to 4096 entries, one each for every Page Table
22702 that is currently in use.
22704 Without an argument, @kbd{info dos pde} displays the entire Page
22705 Directory, and @kbd{info dos pte} displays all the entries in all of
22706 the Page Tables. An argument, an integer expression, given to the
22707 @kbd{info dos pde} command means display only that entry from the Page
22708 Directory table. An argument given to the @kbd{info dos pte} command
22709 means display entries from a single Page Table, the one pointed to by
22710 the specified entry in the Page Directory.
22712 @cindex direct memory access (DMA) on MS-DOS
22713 These commands are useful when your program uses @dfn{DMA} (Direct
22714 Memory Access), which needs physical addresses to program the DMA
22717 These commands are supported only with some DPMI servers.
22719 @cindex physical address from linear address
22720 @item info dos address-pte @var{addr}
22721 This command displays the Page Table entry for a specified linear
22722 address. The argument @var{addr} is a linear address which should
22723 already have the appropriate segment's base address added to it,
22724 because this command accepts addresses which may belong to @emph{any}
22725 segment. For example, here's how to display the Page Table entry for
22726 the page where a variable @code{i} is stored:
22729 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
22730 @exdent @code{Page Table entry for address 0x11a00d30:}
22731 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
22735 This says that @code{i} is stored at offset @code{0xd30} from the page
22736 whose physical base address is @code{0x02698000}, and shows all the
22737 attributes of that page.
22739 Note that you must cast the addresses of variables to a @code{char *},
22740 since otherwise the value of @code{__djgpp_base_address}, the base
22741 address of all variables and functions in a @sc{djgpp} program, will
22742 be added using the rules of C pointer arithmetics: if @code{i} is
22743 declared an @code{int}, @value{GDBN} will add 4 times the value of
22744 @code{__djgpp_base_address} to the address of @code{i}.
22746 Here's another example, it displays the Page Table entry for the
22750 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
22751 @exdent @code{Page Table entry for address 0x29110:}
22752 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
22756 (The @code{+ 3} offset is because the transfer buffer's address is the
22757 3rd member of the @code{_go32_info_block} structure.) The output
22758 clearly shows that this DPMI server maps the addresses in conventional
22759 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
22760 linear (@code{0x29110}) addresses are identical.
22762 This command is supported only with some DPMI servers.
22765 @cindex DOS serial data link, remote debugging
22766 In addition to native debugging, the DJGPP port supports remote
22767 debugging via a serial data link. The following commands are specific
22768 to remote serial debugging in the DJGPP port of @value{GDBN}.
22771 @kindex set com1base
22772 @kindex set com1irq
22773 @kindex set com2base
22774 @kindex set com2irq
22775 @kindex set com3base
22776 @kindex set com3irq
22777 @kindex set com4base
22778 @kindex set com4irq
22779 @item set com1base @var{addr}
22780 This command sets the base I/O port address of the @file{COM1} serial
22783 @item set com1irq @var{irq}
22784 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
22785 for the @file{COM1} serial port.
22787 There are similar commands @samp{set com2base}, @samp{set com3irq},
22788 etc.@: for setting the port address and the @code{IRQ} lines for the
22791 @kindex show com1base
22792 @kindex show com1irq
22793 @kindex show com2base
22794 @kindex show com2irq
22795 @kindex show com3base
22796 @kindex show com3irq
22797 @kindex show com4base
22798 @kindex show com4irq
22799 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
22800 display the current settings of the base address and the @code{IRQ}
22801 lines used by the COM ports.
22804 @kindex info serial
22805 @cindex DOS serial port status
22806 This command prints the status of the 4 DOS serial ports. For each
22807 port, it prints whether it's active or not, its I/O base address and
22808 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
22809 counts of various errors encountered so far.
22813 @node Cygwin Native
22814 @subsection Features for Debugging MS Windows PE Executables
22815 @cindex MS Windows debugging
22816 @cindex native Cygwin debugging
22817 @cindex Cygwin-specific commands
22819 @value{GDBN} supports native debugging of MS Windows programs, including
22820 DLLs with and without symbolic debugging information.
22822 @cindex Ctrl-BREAK, MS-Windows
22823 @cindex interrupt debuggee on MS-Windows
22824 MS-Windows programs that call @code{SetConsoleMode} to switch off the
22825 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
22826 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
22827 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
22828 sequence, which can be used to interrupt the debuggee even if it
22831 There are various additional Cygwin-specific commands, described in
22832 this section. Working with DLLs that have no debugging symbols is
22833 described in @ref{Non-debug DLL Symbols}.
22838 This is a prefix of MS Windows-specific commands which print
22839 information about the target system and important OS structures.
22841 @item info w32 selector
22842 This command displays information returned by
22843 the Win32 API @code{GetThreadSelectorEntry} function.
22844 It takes an optional argument that is evaluated to
22845 a long value to give the information about this given selector.
22846 Without argument, this command displays information
22847 about the six segment registers.
22849 @item info w32 thread-information-block
22850 This command displays thread specific information stored in the
22851 Thread Information Block (readable on the X86 CPU family using @code{$fs}
22852 selector for 32-bit programs and @code{$gs} for 64-bit programs).
22854 @kindex signal-event
22855 @item signal-event @var{id}
22856 This command signals an event with user-provided @var{id}. Used to resume
22857 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
22859 To use it, create or edit the following keys in
22860 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
22861 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
22862 (for x86_64 versions):
22866 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
22867 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
22868 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
22870 The first @code{%ld} will be replaced by the process ID of the
22871 crashing process, the second @code{%ld} will be replaced by the ID of
22872 the event that blocks the crashing process, waiting for @value{GDBN}
22876 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
22877 make the system run debugger specified by the Debugger key
22878 automatically, @code{0} will cause a dialog box with ``OK'' and
22879 ``Cancel'' buttons to appear, which allows the user to either
22880 terminate the crashing process (OK) or debug it (Cancel).
22883 @kindex set cygwin-exceptions
22884 @cindex debugging the Cygwin DLL
22885 @cindex Cygwin DLL, debugging
22886 @item set cygwin-exceptions @var{mode}
22887 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
22888 happen inside the Cygwin DLL. If @var{mode} is @code{off},
22889 @value{GDBN} will delay recognition of exceptions, and may ignore some
22890 exceptions which seem to be caused by internal Cygwin DLL
22891 ``bookkeeping''. This option is meant primarily for debugging the
22892 Cygwin DLL itself; the default value is @code{off} to avoid annoying
22893 @value{GDBN} users with false @code{SIGSEGV} signals.
22895 @kindex show cygwin-exceptions
22896 @item show cygwin-exceptions
22897 Displays whether @value{GDBN} will break on exceptions that happen
22898 inside the Cygwin DLL itself.
22900 @kindex set new-console
22901 @item set new-console @var{mode}
22902 If @var{mode} is @code{on} the debuggee will
22903 be started in a new console on next start.
22904 If @var{mode} is @code{off}, the debuggee will
22905 be started in the same console as the debugger.
22907 @kindex show new-console
22908 @item show new-console
22909 Displays whether a new console is used
22910 when the debuggee is started.
22912 @kindex set new-group
22913 @item set new-group @var{mode}
22914 This boolean value controls whether the debuggee should
22915 start a new group or stay in the same group as the debugger.
22916 This affects the way the Windows OS handles
22919 @kindex show new-group
22920 @item show new-group
22921 Displays current value of new-group boolean.
22923 @kindex set debugevents
22924 @item set debugevents
22925 This boolean value adds debug output concerning kernel events related
22926 to the debuggee seen by the debugger. This includes events that
22927 signal thread and process creation and exit, DLL loading and
22928 unloading, console interrupts, and debugging messages produced by the
22929 Windows @code{OutputDebugString} API call.
22931 @kindex set debugexec
22932 @item set debugexec
22933 This boolean value adds debug output concerning execute events
22934 (such as resume thread) seen by the debugger.
22936 @kindex set debugexceptions
22937 @item set debugexceptions
22938 This boolean value adds debug output concerning exceptions in the
22939 debuggee seen by the debugger.
22941 @kindex set debugmemory
22942 @item set debugmemory
22943 This boolean value adds debug output concerning debuggee memory reads
22944 and writes by the debugger.
22948 This boolean values specifies whether the debuggee is called
22949 via a shell or directly (default value is on).
22953 Displays if the debuggee will be started with a shell.
22958 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
22961 @node Non-debug DLL Symbols
22962 @subsubsection Support for DLLs without Debugging Symbols
22963 @cindex DLLs with no debugging symbols
22964 @cindex Minimal symbols and DLLs
22966 Very often on windows, some of the DLLs that your program relies on do
22967 not include symbolic debugging information (for example,
22968 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
22969 symbols in a DLL, it relies on the minimal amount of symbolic
22970 information contained in the DLL's export table. This section
22971 describes working with such symbols, known internally to @value{GDBN} as
22972 ``minimal symbols''.
22974 Note that before the debugged program has started execution, no DLLs
22975 will have been loaded. The easiest way around this problem is simply to
22976 start the program --- either by setting a breakpoint or letting the
22977 program run once to completion.
22979 @subsubsection DLL Name Prefixes
22981 In keeping with the naming conventions used by the Microsoft debugging
22982 tools, DLL export symbols are made available with a prefix based on the
22983 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
22984 also entered into the symbol table, so @code{CreateFileA} is often
22985 sufficient. In some cases there will be name clashes within a program
22986 (particularly if the executable itself includes full debugging symbols)
22987 necessitating the use of the fully qualified name when referring to the
22988 contents of the DLL. Use single-quotes around the name to avoid the
22989 exclamation mark (``!'') being interpreted as a language operator.
22991 Note that the internal name of the DLL may be all upper-case, even
22992 though the file name of the DLL is lower-case, or vice-versa. Since
22993 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
22994 some confusion. If in doubt, try the @code{info functions} and
22995 @code{info variables} commands or even @code{maint print msymbols}
22996 (@pxref{Symbols}). Here's an example:
22999 (@value{GDBP}) info function CreateFileA
23000 All functions matching regular expression "CreateFileA":
23002 Non-debugging symbols:
23003 0x77e885f4 CreateFileA
23004 0x77e885f4 KERNEL32!CreateFileA
23008 (@value{GDBP}) info function !
23009 All functions matching regular expression "!":
23011 Non-debugging symbols:
23012 0x6100114c cygwin1!__assert
23013 0x61004034 cygwin1!_dll_crt0@@0
23014 0x61004240 cygwin1!dll_crt0(per_process *)
23018 @subsubsection Working with Minimal Symbols
23020 Symbols extracted from a DLL's export table do not contain very much
23021 type information. All that @value{GDBN} can do is guess whether a symbol
23022 refers to a function or variable depending on the linker section that
23023 contains the symbol. Also note that the actual contents of the memory
23024 contained in a DLL are not available unless the program is running. This
23025 means that you cannot examine the contents of a variable or disassemble
23026 a function within a DLL without a running program.
23028 Variables are generally treated as pointers and dereferenced
23029 automatically. For this reason, it is often necessary to prefix a
23030 variable name with the address-of operator (``&'') and provide explicit
23031 type information in the command. Here's an example of the type of
23035 (@value{GDBP}) print 'cygwin1!__argv'
23036 'cygwin1!__argv' has unknown type; cast it to its declared type
23040 (@value{GDBP}) x 'cygwin1!__argv'
23041 'cygwin1!__argv' has unknown type; cast it to its declared type
23044 And two possible solutions:
23047 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
23048 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
23052 (@value{GDBP}) x/2x &'cygwin1!__argv'
23053 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
23054 (@value{GDBP}) x/x 0x10021608
23055 0x10021608: 0x0022fd98
23056 (@value{GDBP}) x/s 0x0022fd98
23057 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
23060 Setting a break point within a DLL is possible even before the program
23061 starts execution. However, under these circumstances, @value{GDBN} can't
23062 examine the initial instructions of the function in order to skip the
23063 function's frame set-up code. You can work around this by using ``*&''
23064 to set the breakpoint at a raw memory address:
23067 (@value{GDBP}) break *&'python22!PyOS_Readline'
23068 Breakpoint 1 at 0x1e04eff0
23071 The author of these extensions is not entirely convinced that setting a
23072 break point within a shared DLL like @file{kernel32.dll} is completely
23076 @subsection Commands Specific to @sc{gnu} Hurd Systems
23077 @cindex @sc{gnu} Hurd debugging
23079 This subsection describes @value{GDBN} commands specific to the
23080 @sc{gnu} Hurd native debugging.
23085 @kindex set signals@r{, Hurd command}
23086 @kindex set sigs@r{, Hurd command}
23087 This command toggles the state of inferior signal interception by
23088 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
23089 affected by this command. @code{sigs} is a shorthand alias for
23094 @kindex show signals@r{, Hurd command}
23095 @kindex show sigs@r{, Hurd command}
23096 Show the current state of intercepting inferior's signals.
23098 @item set signal-thread
23099 @itemx set sigthread
23100 @kindex set signal-thread
23101 @kindex set sigthread
23102 This command tells @value{GDBN} which thread is the @code{libc} signal
23103 thread. That thread is run when a signal is delivered to a running
23104 process. @code{set sigthread} is the shorthand alias of @code{set
23107 @item show signal-thread
23108 @itemx show sigthread
23109 @kindex show signal-thread
23110 @kindex show sigthread
23111 These two commands show which thread will run when the inferior is
23112 delivered a signal.
23115 @kindex set stopped@r{, Hurd command}
23116 This commands tells @value{GDBN} that the inferior process is stopped,
23117 as with the @code{SIGSTOP} signal. The stopped process can be
23118 continued by delivering a signal to it.
23121 @kindex show stopped@r{, Hurd command}
23122 This command shows whether @value{GDBN} thinks the debuggee is
23125 @item set exceptions
23126 @kindex set exceptions@r{, Hurd command}
23127 Use this command to turn off trapping of exceptions in the inferior.
23128 When exception trapping is off, neither breakpoints nor
23129 single-stepping will work. To restore the default, set exception
23132 @item show exceptions
23133 @kindex show exceptions@r{, Hurd command}
23134 Show the current state of trapping exceptions in the inferior.
23136 @item set task pause
23137 @kindex set task@r{, Hurd commands}
23138 @cindex task attributes (@sc{gnu} Hurd)
23139 @cindex pause current task (@sc{gnu} Hurd)
23140 This command toggles task suspension when @value{GDBN} has control.
23141 Setting it to on takes effect immediately, and the task is suspended
23142 whenever @value{GDBN} gets control. Setting it to off will take
23143 effect the next time the inferior is continued. If this option is set
23144 to off, you can use @code{set thread default pause on} or @code{set
23145 thread pause on} (see below) to pause individual threads.
23147 @item show task pause
23148 @kindex show task@r{, Hurd commands}
23149 Show the current state of task suspension.
23151 @item set task detach-suspend-count
23152 @cindex task suspend count
23153 @cindex detach from task, @sc{gnu} Hurd
23154 This command sets the suspend count the task will be left with when
23155 @value{GDBN} detaches from it.
23157 @item show task detach-suspend-count
23158 Show the suspend count the task will be left with when detaching.
23160 @item set task exception-port
23161 @itemx set task excp
23162 @cindex task exception port, @sc{gnu} Hurd
23163 This command sets the task exception port to which @value{GDBN} will
23164 forward exceptions. The argument should be the value of the @dfn{send
23165 rights} of the task. @code{set task excp} is a shorthand alias.
23167 @item set noninvasive
23168 @cindex noninvasive task options
23169 This command switches @value{GDBN} to a mode that is the least
23170 invasive as far as interfering with the inferior is concerned. This
23171 is the same as using @code{set task pause}, @code{set exceptions}, and
23172 @code{set signals} to values opposite to the defaults.
23174 @item info send-rights
23175 @itemx info receive-rights
23176 @itemx info port-rights
23177 @itemx info port-sets
23178 @itemx info dead-names
23181 @cindex send rights, @sc{gnu} Hurd
23182 @cindex receive rights, @sc{gnu} Hurd
23183 @cindex port rights, @sc{gnu} Hurd
23184 @cindex port sets, @sc{gnu} Hurd
23185 @cindex dead names, @sc{gnu} Hurd
23186 These commands display information about, respectively, send rights,
23187 receive rights, port rights, port sets, and dead names of a task.
23188 There are also shorthand aliases: @code{info ports} for @code{info
23189 port-rights} and @code{info psets} for @code{info port-sets}.
23191 @item set thread pause
23192 @kindex set thread@r{, Hurd command}
23193 @cindex thread properties, @sc{gnu} Hurd
23194 @cindex pause current thread (@sc{gnu} Hurd)
23195 This command toggles current thread suspension when @value{GDBN} has
23196 control. Setting it to on takes effect immediately, and the current
23197 thread is suspended whenever @value{GDBN} gets control. Setting it to
23198 off will take effect the next time the inferior is continued.
23199 Normally, this command has no effect, since when @value{GDBN} has
23200 control, the whole task is suspended. However, if you used @code{set
23201 task pause off} (see above), this command comes in handy to suspend
23202 only the current thread.
23204 @item show thread pause
23205 @kindex show thread@r{, Hurd command}
23206 This command shows the state of current thread suspension.
23208 @item set thread run
23209 This command sets whether the current thread is allowed to run.
23211 @item show thread run
23212 Show whether the current thread is allowed to run.
23214 @item set thread detach-suspend-count
23215 @cindex thread suspend count, @sc{gnu} Hurd
23216 @cindex detach from thread, @sc{gnu} Hurd
23217 This command sets the suspend count @value{GDBN} will leave on a
23218 thread when detaching. This number is relative to the suspend count
23219 found by @value{GDBN} when it notices the thread; use @code{set thread
23220 takeover-suspend-count} to force it to an absolute value.
23222 @item show thread detach-suspend-count
23223 Show the suspend count @value{GDBN} will leave on the thread when
23226 @item set thread exception-port
23227 @itemx set thread excp
23228 Set the thread exception port to which to forward exceptions. This
23229 overrides the port set by @code{set task exception-port} (see above).
23230 @code{set thread excp} is the shorthand alias.
23232 @item set thread takeover-suspend-count
23233 Normally, @value{GDBN}'s thread suspend counts are relative to the
23234 value @value{GDBN} finds when it notices each thread. This command
23235 changes the suspend counts to be absolute instead.
23237 @item set thread default
23238 @itemx show thread default
23239 @cindex thread default settings, @sc{gnu} Hurd
23240 Each of the above @code{set thread} commands has a @code{set thread
23241 default} counterpart (e.g., @code{set thread default pause}, @code{set
23242 thread default exception-port}, etc.). The @code{thread default}
23243 variety of commands sets the default thread properties for all
23244 threads; you can then change the properties of individual threads with
23245 the non-default commands.
23252 @value{GDBN} provides the following commands specific to the Darwin target:
23255 @item set debug darwin @var{num}
23256 @kindex set debug darwin
23257 When set to a non zero value, enables debugging messages specific to
23258 the Darwin support. Higher values produce more verbose output.
23260 @item show debug darwin
23261 @kindex show debug darwin
23262 Show the current state of Darwin messages.
23264 @item set debug mach-o @var{num}
23265 @kindex set debug mach-o
23266 When set to a non zero value, enables debugging messages while
23267 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
23268 file format used on Darwin for object and executable files.) Higher
23269 values produce more verbose output. This is a command to diagnose
23270 problems internal to @value{GDBN} and should not be needed in normal
23273 @item show debug mach-o
23274 @kindex show debug mach-o
23275 Show the current state of Mach-O file messages.
23277 @item set mach-exceptions on
23278 @itemx set mach-exceptions off
23279 @kindex set mach-exceptions
23280 On Darwin, faults are first reported as a Mach exception and are then
23281 mapped to a Posix signal. Use this command to turn on trapping of
23282 Mach exceptions in the inferior. This might be sometimes useful to
23283 better understand the cause of a fault. The default is off.
23285 @item show mach-exceptions
23286 @kindex show mach-exceptions
23287 Show the current state of exceptions trapping.
23291 @subsection FreeBSD
23294 When the ABI of a system call is changed in the FreeBSD kernel, this
23295 is implemented by leaving a compatibility system call using the old
23296 ABI at the existing number and allocating a new system call number for
23297 the version using the new ABI. As a convenience, when a system call
23298 is caught by name (@pxref{catch syscall}), compatibility system calls
23301 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
23302 system call and catching the @code{kevent} system call by name catches
23306 (@value{GDBP}) catch syscall kevent
23307 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
23313 @section Embedded Operating Systems
23315 This section describes configurations involving the debugging of
23316 embedded operating systems that are available for several different
23319 @value{GDBN} includes the ability to debug programs running on
23320 various real-time operating systems.
23322 @node Embedded Processors
23323 @section Embedded Processors
23325 This section goes into details specific to particular embedded
23328 @cindex send command to simulator
23329 Whenever a specific embedded processor has a simulator, @value{GDBN}
23330 allows to send an arbitrary command to the simulator.
23333 @item sim @var{command}
23334 @kindex sim@r{, a command}
23335 Send an arbitrary @var{command} string to the simulator. Consult the
23336 documentation for the specific simulator in use for information about
23337 acceptable commands.
23342 * ARC:: Synopsys ARC
23344 * M68K:: Motorola M68K
23345 * MicroBlaze:: Xilinx MicroBlaze
23346 * MIPS Embedded:: MIPS Embedded
23347 * OpenRISC 1000:: OpenRISC 1000 (or1k)
23348 * PowerPC Embedded:: PowerPC Embedded
23351 * Super-H:: Renesas Super-H
23355 @subsection Synopsys ARC
23356 @cindex Synopsys ARC
23357 @cindex ARC specific commands
23363 @value{GDBN} provides the following ARC-specific commands:
23366 @item set debug arc
23367 @kindex set debug arc
23368 Control the level of ARC specific debug messages. Use 0 for no messages (the
23369 default), 1 for debug messages, and 2 for even more debug messages.
23371 @item show debug arc
23372 @kindex show debug arc
23373 Show the level of ARC specific debugging in operation.
23375 @item maint print arc arc-instruction @var{address}
23376 @kindex maint print arc arc-instruction
23377 Print internal disassembler information about instruction at a given address.
23384 @value{GDBN} provides the following ARM-specific commands:
23387 @item set arm disassembler
23389 This commands selects from a list of disassembly styles. The
23390 @code{"std"} style is the standard style.
23392 @item show arm disassembler
23394 Show the current disassembly style.
23396 @item set arm apcs32
23397 @cindex ARM 32-bit mode
23398 This command toggles ARM operation mode between 32-bit and 26-bit.
23400 @item show arm apcs32
23401 Display the current usage of the ARM 32-bit mode.
23403 @item set arm fpu @var{fputype}
23404 This command sets the ARM floating-point unit (FPU) type. The
23405 argument @var{fputype} can be one of these:
23409 Determine the FPU type by querying the OS ABI.
23411 Software FPU, with mixed-endian doubles on little-endian ARM
23414 GCC-compiled FPA co-processor.
23416 Software FPU with pure-endian doubles.
23422 Show the current type of the FPU.
23425 This command forces @value{GDBN} to use the specified ABI.
23428 Show the currently used ABI.
23430 @item set arm fallback-mode (arm|thumb|auto)
23431 @value{GDBN} uses the symbol table, when available, to determine
23432 whether instructions are ARM or Thumb. This command controls
23433 @value{GDBN}'s default behavior when the symbol table is not
23434 available. The default is @samp{auto}, which causes @value{GDBN} to
23435 use the current execution mode (from the @code{T} bit in the @code{CPSR}
23438 @item show arm fallback-mode
23439 Show the current fallback instruction mode.
23441 @item set arm force-mode (arm|thumb|auto)
23442 This command overrides use of the symbol table to determine whether
23443 instructions are ARM or Thumb. The default is @samp{auto}, which
23444 causes @value{GDBN} to use the symbol table and then the setting
23445 of @samp{set arm fallback-mode}.
23447 @item show arm force-mode
23448 Show the current forced instruction mode.
23450 @item set debug arm
23451 Toggle whether to display ARM-specific debugging messages from the ARM
23452 target support subsystem.
23454 @item show debug arm
23455 Show whether ARM-specific debugging messages are enabled.
23459 @item target sim @r{[}@var{simargs}@r{]} @dots{}
23460 The @value{GDBN} ARM simulator accepts the following optional arguments.
23463 @item --swi-support=@var{type}
23464 Tell the simulator which SWI interfaces to support. The argument
23465 @var{type} may be a comma separated list of the following values.
23466 The default value is @code{all}.
23481 The Motorola m68k configuration includes ColdFire support.
23484 @subsection MicroBlaze
23485 @cindex Xilinx MicroBlaze
23486 @cindex XMD, Xilinx Microprocessor Debugger
23488 The MicroBlaze is a soft-core processor supported on various Xilinx
23489 FPGAs, such as Spartan or Virtex series. Boards with these processors
23490 usually have JTAG ports which connect to a host system running the Xilinx
23491 Embedded Development Kit (EDK) or Software Development Kit (SDK).
23492 This host system is used to download the configuration bitstream to
23493 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
23494 communicates with the target board using the JTAG interface and
23495 presents a @code{gdbserver} interface to the board. By default
23496 @code{xmd} uses port @code{1234}. (While it is possible to change
23497 this default port, it requires the use of undocumented @code{xmd}
23498 commands. Contact Xilinx support if you need to do this.)
23500 Use these GDB commands to connect to the MicroBlaze target processor.
23503 @item target remote :1234
23504 Use this command to connect to the target if you are running @value{GDBN}
23505 on the same system as @code{xmd}.
23507 @item target remote @var{xmd-host}:1234
23508 Use this command to connect to the target if it is connected to @code{xmd}
23509 running on a different system named @var{xmd-host}.
23512 Use this command to download a program to the MicroBlaze target.
23514 @item set debug microblaze @var{n}
23515 Enable MicroBlaze-specific debugging messages if non-zero.
23517 @item show debug microblaze @var{n}
23518 Show MicroBlaze-specific debugging level.
23521 @node MIPS Embedded
23522 @subsection @acronym{MIPS} Embedded
23525 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
23528 @item set mipsfpu double
23529 @itemx set mipsfpu single
23530 @itemx set mipsfpu none
23531 @itemx set mipsfpu auto
23532 @itemx show mipsfpu
23533 @kindex set mipsfpu
23534 @kindex show mipsfpu
23535 @cindex @acronym{MIPS} remote floating point
23536 @cindex floating point, @acronym{MIPS} remote
23537 If your target board does not support the @acronym{MIPS} floating point
23538 coprocessor, you should use the command @samp{set mipsfpu none} (if you
23539 need this, you may wish to put the command in your @value{GDBN} init
23540 file). This tells @value{GDBN} how to find the return value of
23541 functions which return floating point values. It also allows
23542 @value{GDBN} to avoid saving the floating point registers when calling
23543 functions on the board. If you are using a floating point coprocessor
23544 with only single precision floating point support, as on the @sc{r4650}
23545 processor, use the command @samp{set mipsfpu single}. The default
23546 double precision floating point coprocessor may be selected using
23547 @samp{set mipsfpu double}.
23549 In previous versions the only choices were double precision or no
23550 floating point, so @samp{set mipsfpu on} will select double precision
23551 and @samp{set mipsfpu off} will select no floating point.
23553 As usual, you can inquire about the @code{mipsfpu} variable with
23554 @samp{show mipsfpu}.
23557 @node OpenRISC 1000
23558 @subsection OpenRISC 1000
23559 @cindex OpenRISC 1000
23562 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
23563 mainly provided as a soft-core which can run on Xilinx, Altera and other
23566 @value{GDBN} for OpenRISC supports the below commands when connecting to
23574 Runs the builtin CPU simulator which can run very basic
23575 programs but does not support most hardware functions like MMU.
23576 For more complex use cases the user is advised to run an external
23577 target, and connect using @samp{target remote}.
23579 Example: @code{target sim}
23581 @item set debug or1k
23582 Toggle whether to display OpenRISC-specific debugging messages from the
23583 OpenRISC target support subsystem.
23585 @item show debug or1k
23586 Show whether OpenRISC-specific debugging messages are enabled.
23589 @node PowerPC Embedded
23590 @subsection PowerPC Embedded
23592 @cindex DVC register
23593 @value{GDBN} supports using the DVC (Data Value Compare) register to
23594 implement in hardware simple hardware watchpoint conditions of the form:
23597 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
23598 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
23601 The DVC register will be automatically used when @value{GDBN} detects
23602 such pattern in a condition expression, and the created watchpoint uses one
23603 debug register (either the @code{exact-watchpoints} option is on and the
23604 variable is scalar, or the variable has a length of one byte). This feature
23605 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
23608 When running on PowerPC embedded processors, @value{GDBN} automatically uses
23609 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
23610 in which case watchpoints using only one debug register are created when
23611 watching variables of scalar types.
23613 You can create an artificial array to watch an arbitrary memory
23614 region using one of the following commands (@pxref{Expressions}):
23617 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
23618 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
23621 PowerPC embedded processors support masked watchpoints. See the discussion
23622 about the @code{mask} argument in @ref{Set Watchpoints}.
23624 @cindex ranged breakpoint
23625 PowerPC embedded processors support hardware accelerated
23626 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
23627 the inferior whenever it executes an instruction at any address within
23628 the range it specifies. To set a ranged breakpoint in @value{GDBN},
23629 use the @code{break-range} command.
23631 @value{GDBN} provides the following PowerPC-specific commands:
23634 @kindex break-range
23635 @item break-range @var{start-location}, @var{end-location}
23636 Set a breakpoint for an address range given by
23637 @var{start-location} and @var{end-location}, which can specify a function name,
23638 a line number, an offset of lines from the current line or from the start
23639 location, or an address of an instruction (see @ref{Specify Location},
23640 for a list of all the possible ways to specify a @var{location}.)
23641 The breakpoint will stop execution of the inferior whenever it
23642 executes an instruction at any address within the specified range,
23643 (including @var{start-location} and @var{end-location}.)
23645 @kindex set powerpc
23646 @item set powerpc soft-float
23647 @itemx show powerpc soft-float
23648 Force @value{GDBN} to use (or not use) a software floating point calling
23649 convention. By default, @value{GDBN} selects the calling convention based
23650 on the selected architecture and the provided executable file.
23652 @item set powerpc vector-abi
23653 @itemx show powerpc vector-abi
23654 Force @value{GDBN} to use the specified calling convention for vector
23655 arguments and return values. The valid options are @samp{auto};
23656 @samp{generic}, to avoid vector registers even if they are present;
23657 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
23658 registers. By default, @value{GDBN} selects the calling convention
23659 based on the selected architecture and the provided executable file.
23661 @item set powerpc exact-watchpoints
23662 @itemx show powerpc exact-watchpoints
23663 Allow @value{GDBN} to use only one debug register when watching a variable
23664 of scalar type, thus assuming that the variable is accessed through the
23665 address of its first byte.
23670 @subsection Atmel AVR
23673 When configured for debugging the Atmel AVR, @value{GDBN} supports the
23674 following AVR-specific commands:
23677 @item info io_registers
23678 @kindex info io_registers@r{, AVR}
23679 @cindex I/O registers (Atmel AVR)
23680 This command displays information about the AVR I/O registers. For
23681 each register, @value{GDBN} prints its number and value.
23688 When configured for debugging CRIS, @value{GDBN} provides the
23689 following CRIS-specific commands:
23692 @item set cris-version @var{ver}
23693 @cindex CRIS version
23694 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
23695 The CRIS version affects register names and sizes. This command is useful in
23696 case autodetection of the CRIS version fails.
23698 @item show cris-version
23699 Show the current CRIS version.
23701 @item set cris-dwarf2-cfi
23702 @cindex DWARF-2 CFI and CRIS
23703 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
23704 Change to @samp{off} when using @code{gcc-cris} whose version is below
23707 @item show cris-dwarf2-cfi
23708 Show the current state of using DWARF-2 CFI.
23710 @item set cris-mode @var{mode}
23712 Set the current CRIS mode to @var{mode}. It should only be changed when
23713 debugging in guru mode, in which case it should be set to
23714 @samp{guru} (the default is @samp{normal}).
23716 @item show cris-mode
23717 Show the current CRIS mode.
23721 @subsection Renesas Super-H
23724 For the Renesas Super-H processor, @value{GDBN} provides these
23728 @item set sh calling-convention @var{convention}
23729 @kindex set sh calling-convention
23730 Set the calling-convention used when calling functions from @value{GDBN}.
23731 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
23732 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
23733 convention. If the DWARF-2 information of the called function specifies
23734 that the function follows the Renesas calling convention, the function
23735 is called using the Renesas calling convention. If the calling convention
23736 is set to @samp{renesas}, the Renesas calling convention is always used,
23737 regardless of the DWARF-2 information. This can be used to override the
23738 default of @samp{gcc} if debug information is missing, or the compiler
23739 does not emit the DWARF-2 calling convention entry for a function.
23741 @item show sh calling-convention
23742 @kindex show sh calling-convention
23743 Show the current calling convention setting.
23748 @node Architectures
23749 @section Architectures
23751 This section describes characteristics of architectures that affect
23752 all uses of @value{GDBN} with the architecture, both native and cross.
23759 * HPPA:: HP PA architecture
23760 * SPU:: Cell Broadband Engine SPU architecture
23768 @subsection AArch64
23769 @cindex AArch64 support
23771 When @value{GDBN} is debugging the AArch64 architecture, it provides the
23772 following special commands:
23775 @item set debug aarch64
23776 @kindex set debug aarch64
23777 This command determines whether AArch64 architecture-specific debugging
23778 messages are to be displayed.
23780 @item show debug aarch64
23781 Show whether AArch64 debugging messages are displayed.
23785 @subsubsection AArch64 SVE.
23786 @cindex AArch64 SVE.
23788 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
23789 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
23790 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
23791 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
23792 @code{$vg} will be provided. This is the vector granule for the current thread
23793 and represents the number of 64-bit chunks in an SVE @code{z} register.
23795 If the vector length changes, then the @code{$vg} register will be updated,
23796 but the lengths of the @code{z} and @code{p} registers will not change. This
23797 is a known limitation of @value{GDBN} and does not affect the execution of the
23802 @subsection x86 Architecture-specific Issues
23805 @item set struct-convention @var{mode}
23806 @kindex set struct-convention
23807 @cindex struct return convention
23808 @cindex struct/union returned in registers
23809 Set the convention used by the inferior to return @code{struct}s and
23810 @code{union}s from functions to @var{mode}. Possible values of
23811 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
23812 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
23813 are returned on the stack, while @code{"reg"} means that a
23814 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
23815 be returned in a register.
23817 @item show struct-convention
23818 @kindex show struct-convention
23819 Show the current setting of the convention to return @code{struct}s
23824 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
23825 @cindex Intel Memory Protection Extensions (MPX).
23827 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
23828 @footnote{The register named with capital letters represent the architecture
23829 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
23830 which are the lower bound and upper bound. Bounds are effective addresses or
23831 memory locations. The upper bounds are architecturally represented in 1's
23832 complement form. A bound having lower bound = 0, and upper bound = 0
23833 (1's complement of all bits set) will allow access to the entire address space.
23835 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
23836 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
23837 display the upper bound performing the complement of one operation on the
23838 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
23839 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
23840 can also be noted that the upper bounds are inclusive.
23842 As an example, assume that the register BND0 holds bounds for a pointer having
23843 access allowed for the range between 0x32 and 0x71. The values present on
23844 bnd0raw and bnd registers are presented as follows:
23847 bnd0raw = @{0x32, 0xffffffff8e@}
23848 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
23851 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
23852 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
23853 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
23854 Python, the display includes the memory size, in bits, accessible to
23857 Bounds can also be stored in bounds tables, which are stored in
23858 application memory. These tables store bounds for pointers by specifying
23859 the bounds pointer's value along with its bounds. Evaluating and changing
23860 bounds located in bound tables is therefore interesting while investigating
23861 bugs on MPX context. @value{GDBN} provides commands for this purpose:
23864 @item show mpx bound @var{pointer}
23865 @kindex show mpx bound
23866 Display bounds of the given @var{pointer}.
23868 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
23869 @kindex set mpx bound
23870 Set the bounds of a pointer in the bound table.
23871 This command takes three parameters: @var{pointer} is the pointers
23872 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
23873 for lower and upper bounds respectively.
23876 When you call an inferior function on an Intel MPX enabled program,
23877 GDB sets the inferior's bound registers to the init (disabled) state
23878 before calling the function. As a consequence, bounds checks for the
23879 pointer arguments passed to the function will always pass.
23881 This is necessary because when you call an inferior function, the
23882 program is usually in the middle of the execution of other function.
23883 Since at that point bound registers are in an arbitrary state, not
23884 clearing them would lead to random bound violations in the called
23887 You can still examine the influence of the bound registers on the
23888 execution of the called function by stopping the execution of the
23889 called function at its prologue, setting bound registers, and
23890 continuing the execution. For example:
23894 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
23895 $ print upper (a, b, c, d, 1)
23896 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
23898 @{lbound = 0x0, ubound = ffffffff@} : size -1
23901 At this last step the value of bnd0 can be changed for investigation of bound
23902 violations caused along the execution of the call. In order to know how to
23903 set the bound registers or bound table for the call consult the ABI.
23908 See the following section.
23911 @subsection @acronym{MIPS}
23913 @cindex stack on Alpha
23914 @cindex stack on @acronym{MIPS}
23915 @cindex Alpha stack
23916 @cindex @acronym{MIPS} stack
23917 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
23918 sometimes requires @value{GDBN} to search backward in the object code to
23919 find the beginning of a function.
23921 @cindex response time, @acronym{MIPS} debugging
23922 To improve response time (especially for embedded applications, where
23923 @value{GDBN} may be restricted to a slow serial line for this search)
23924 you may want to limit the size of this search, using one of these
23928 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
23929 @item set heuristic-fence-post @var{limit}
23930 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
23931 search for the beginning of a function. A value of @var{0} (the
23932 default) means there is no limit. However, except for @var{0}, the
23933 larger the limit the more bytes @code{heuristic-fence-post} must search
23934 and therefore the longer it takes to run. You should only need to use
23935 this command when debugging a stripped executable.
23937 @item show heuristic-fence-post
23938 Display the current limit.
23942 These commands are available @emph{only} when @value{GDBN} is configured
23943 for debugging programs on Alpha or @acronym{MIPS} processors.
23945 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
23949 @item set mips abi @var{arg}
23950 @kindex set mips abi
23951 @cindex set ABI for @acronym{MIPS}
23952 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
23953 values of @var{arg} are:
23957 The default ABI associated with the current binary (this is the
23967 @item show mips abi
23968 @kindex show mips abi
23969 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
23971 @item set mips compression @var{arg}
23972 @kindex set mips compression
23973 @cindex code compression, @acronym{MIPS}
23974 Tell @value{GDBN} which @acronym{MIPS} compressed
23975 @acronym{ISA, Instruction Set Architecture} encoding is used by the
23976 inferior. @value{GDBN} uses this for code disassembly and other
23977 internal interpretation purposes. This setting is only referred to
23978 when no executable has been associated with the debugging session or
23979 the executable does not provide information about the encoding it uses.
23980 Otherwise this setting is automatically updated from information
23981 provided by the executable.
23983 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
23984 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
23985 executables containing @acronym{MIPS16} code frequently are not
23986 identified as such.
23988 This setting is ``sticky''; that is, it retains its value across
23989 debugging sessions until reset either explicitly with this command or
23990 implicitly from an executable.
23992 The compiler and/or assembler typically add symbol table annotations to
23993 identify functions compiled for the @acronym{MIPS16} or
23994 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
23995 are present, @value{GDBN} uses them in preference to the global
23996 compressed @acronym{ISA} encoding setting.
23998 @item show mips compression
23999 @kindex show mips compression
24000 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
24001 @value{GDBN} to debug the inferior.
24004 @itemx show mipsfpu
24005 @xref{MIPS Embedded, set mipsfpu}.
24007 @item set mips mask-address @var{arg}
24008 @kindex set mips mask-address
24009 @cindex @acronym{MIPS} addresses, masking
24010 This command determines whether the most-significant 32 bits of 64-bit
24011 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
24012 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
24013 setting, which lets @value{GDBN} determine the correct value.
24015 @item show mips mask-address
24016 @kindex show mips mask-address
24017 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
24020 @item set remote-mips64-transfers-32bit-regs
24021 @kindex set remote-mips64-transfers-32bit-regs
24022 This command controls compatibility with 64-bit @acronym{MIPS} targets that
24023 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
24024 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
24025 and 64 bits for other registers, set this option to @samp{on}.
24027 @item show remote-mips64-transfers-32bit-regs
24028 @kindex show remote-mips64-transfers-32bit-regs
24029 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
24031 @item set debug mips
24032 @kindex set debug mips
24033 This command turns on and off debugging messages for the @acronym{MIPS}-specific
24034 target code in @value{GDBN}.
24036 @item show debug mips
24037 @kindex show debug mips
24038 Show the current setting of @acronym{MIPS} debugging messages.
24044 @cindex HPPA support
24046 When @value{GDBN} is debugging the HP PA architecture, it provides the
24047 following special commands:
24050 @item set debug hppa
24051 @kindex set debug hppa
24052 This command determines whether HPPA architecture-specific debugging
24053 messages are to be displayed.
24055 @item show debug hppa
24056 Show whether HPPA debugging messages are displayed.
24058 @item maint print unwind @var{address}
24059 @kindex maint print unwind@r{, HPPA}
24060 This command displays the contents of the unwind table entry at the
24061 given @var{address}.
24067 @subsection Cell Broadband Engine SPU architecture
24068 @cindex Cell Broadband Engine
24071 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
24072 it provides the following special commands:
24075 @item info spu event
24077 Display SPU event facility status. Shows current event mask
24078 and pending event status.
24080 @item info spu signal
24081 Display SPU signal notification facility status. Shows pending
24082 signal-control word and signal notification mode of both signal
24083 notification channels.
24085 @item info spu mailbox
24086 Display SPU mailbox facility status. Shows all pending entries,
24087 in order of processing, in each of the SPU Write Outbound,
24088 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
24091 Display MFC DMA status. Shows all pending commands in the MFC
24092 DMA queue. For each entry, opcode, tag, class IDs, effective
24093 and local store addresses and transfer size are shown.
24095 @item info spu proxydma
24096 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
24097 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
24098 and local store addresses and transfer size are shown.
24102 When @value{GDBN} is debugging a combined PowerPC/SPU application
24103 on the Cell Broadband Engine, it provides in addition the following
24107 @item set spu stop-on-load @var{arg}
24109 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
24110 will give control to the user when a new SPE thread enters its @code{main}
24111 function. The default is @code{off}.
24113 @item show spu stop-on-load
24115 Show whether to stop for new SPE threads.
24117 @item set spu auto-flush-cache @var{arg}
24118 Set whether to automatically flush the software-managed cache. When set to
24119 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
24120 cache to be flushed whenever SPE execution stops. This provides a consistent
24121 view of PowerPC memory that is accessed via the cache. If an application
24122 does not use the software-managed cache, this option has no effect.
24124 @item show spu auto-flush-cache
24125 Show whether to automatically flush the software-managed cache.
24130 @subsection PowerPC
24131 @cindex PowerPC architecture
24133 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
24134 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
24135 numbers stored in the floating point registers. These values must be stored
24136 in two consecutive registers, always starting at an even register like
24137 @code{f0} or @code{f2}.
24139 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
24140 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
24141 @code{f2} and @code{f3} for @code{$dl1} and so on.
24143 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
24144 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
24147 @subsection Nios II
24148 @cindex Nios II architecture
24150 When @value{GDBN} is debugging the Nios II architecture,
24151 it provides the following special commands:
24155 @item set debug nios2
24156 @kindex set debug nios2
24157 This command turns on and off debugging messages for the Nios II
24158 target code in @value{GDBN}.
24160 @item show debug nios2
24161 @kindex show debug nios2
24162 Show the current setting of Nios II debugging messages.
24166 @subsection Sparc64
24167 @cindex Sparc64 support
24168 @cindex Application Data Integrity
24169 @subsubsection ADI Support
24171 The M7 processor supports an Application Data Integrity (ADI) feature that
24172 detects invalid data accesses. When software allocates memory and enables
24173 ADI on the allocated memory, it chooses a 4-bit version number, sets the
24174 version in the upper 4 bits of the 64-bit pointer to that data, and stores
24175 the 4-bit version in every cacheline of that data. Hardware saves the latter
24176 in spare bits in the cache and memory hierarchy. On each load and store,
24177 the processor compares the upper 4 VA (virtual address) bits to the
24178 cacheline's version. If there is a mismatch, the processor generates a
24179 version mismatch trap which can be either precise or disrupting. The trap
24180 is an error condition which the kernel delivers to the process as a SIGSEGV
24183 Note that only 64-bit applications can use ADI and need to be built with
24186 Values of the ADI version tags, which are in granularity of a
24187 cacheline (64 bytes), can be viewed or modified.
24191 @kindex adi examine
24192 @item adi (examine | x) [ / @var{n} ] @var{addr}
24194 The @code{adi examine} command displays the value of one ADI version tag per
24197 @var{n} is a decimal integer specifying the number in bytes; the default
24198 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
24199 block size, to display.
24201 @var{addr} is the address in user address space where you want @value{GDBN}
24202 to begin displaying the ADI version tags.
24204 Below is an example of displaying ADI versions of variable "shmaddr".
24207 (@value{GDBP}) adi x/100 shmaddr
24208 0xfff800010002c000: 0 0
24212 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
24214 The @code{adi assign} command is used to assign new ADI version tag
24217 @var{n} is a decimal integer specifying the number in bytes;
24218 the default is 1. It specifies how much ADI version information, at the
24219 ratio of 1:ADI block size, to modify.
24221 @var{addr} is the address in user address space where you want @value{GDBN}
24222 to begin modifying the ADI version tags.
24224 @var{tag} is the new ADI version tag.
24226 For example, do the following to modify then verify ADI versions of
24227 variable "shmaddr":
24230 (@value{GDBP}) adi a/100 shmaddr = 7
24231 (@value{GDBP}) adi x/100 shmaddr
24232 0xfff800010002c000: 7 7
24239 @cindex S12Z support
24241 When @value{GDBN} is debugging the S12Z architecture,
24242 it provides the following special command:
24245 @item maint info bdccsr
24246 @kindex maint info bdccsr@r{, S12Z}
24247 This command displays the current value of the microprocessor's
24252 @node Controlling GDB
24253 @chapter Controlling @value{GDBN}
24255 You can alter the way @value{GDBN} interacts with you by using the
24256 @code{set} command. For commands controlling how @value{GDBN} displays
24257 data, see @ref{Print Settings, ,Print Settings}. Other settings are
24262 * Editing:: Command editing
24263 * Command History:: Command history
24264 * Screen Size:: Screen size
24265 * Output Styling:: Output styling
24266 * Numbers:: Numbers
24267 * ABI:: Configuring the current ABI
24268 * Auto-loading:: Automatically loading associated files
24269 * Messages/Warnings:: Optional warnings and messages
24270 * Debugging Output:: Optional messages about internal happenings
24271 * Other Misc Settings:: Other Miscellaneous Settings
24279 @value{GDBN} indicates its readiness to read a command by printing a string
24280 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
24281 can change the prompt string with the @code{set prompt} command. For
24282 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
24283 the prompt in one of the @value{GDBN} sessions so that you can always tell
24284 which one you are talking to.
24286 @emph{Note:} @code{set prompt} does not add a space for you after the
24287 prompt you set. This allows you to set a prompt which ends in a space
24288 or a prompt that does not.
24292 @item set prompt @var{newprompt}
24293 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
24295 @kindex show prompt
24297 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
24300 Versions of @value{GDBN} that ship with Python scripting enabled have
24301 prompt extensions. The commands for interacting with these extensions
24305 @kindex set extended-prompt
24306 @item set extended-prompt @var{prompt}
24307 Set an extended prompt that allows for substitutions.
24308 @xref{gdb.prompt}, for a list of escape sequences that can be used for
24309 substitution. Any escape sequences specified as part of the prompt
24310 string are replaced with the corresponding strings each time the prompt
24316 set extended-prompt Current working directory: \w (gdb)
24319 Note that when an extended-prompt is set, it takes control of the
24320 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
24322 @kindex show extended-prompt
24323 @item show extended-prompt
24324 Prints the extended prompt. Any escape sequences specified as part of
24325 the prompt string with @code{set extended-prompt}, are replaced with the
24326 corresponding strings each time the prompt is displayed.
24330 @section Command Editing
24332 @cindex command line editing
24334 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
24335 @sc{gnu} library provides consistent behavior for programs which provide a
24336 command line interface to the user. Advantages are @sc{gnu} Emacs-style
24337 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
24338 substitution, and a storage and recall of command history across
24339 debugging sessions.
24341 You may control the behavior of command line editing in @value{GDBN} with the
24342 command @code{set}.
24345 @kindex set editing
24348 @itemx set editing on
24349 Enable command line editing (enabled by default).
24351 @item set editing off
24352 Disable command line editing.
24354 @kindex show editing
24356 Show whether command line editing is enabled.
24359 @ifset SYSTEM_READLINE
24360 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
24362 @ifclear SYSTEM_READLINE
24363 @xref{Command Line Editing},
24365 for more details about the Readline
24366 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
24367 encouraged to read that chapter.
24369 @node Command History
24370 @section Command History
24371 @cindex command history
24373 @value{GDBN} can keep track of the commands you type during your
24374 debugging sessions, so that you can be certain of precisely what
24375 happened. Use these commands to manage the @value{GDBN} command
24378 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
24379 package, to provide the history facility.
24380 @ifset SYSTEM_READLINE
24381 @xref{Using History Interactively, , , history, GNU History Library},
24383 @ifclear SYSTEM_READLINE
24384 @xref{Using History Interactively},
24386 for the detailed description of the History library.
24388 To issue a command to @value{GDBN} without affecting certain aspects of
24389 the state which is seen by users, prefix it with @samp{server }
24390 (@pxref{Server Prefix}). This
24391 means that this command will not affect the command history, nor will it
24392 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
24393 pressed on a line by itself.
24395 @cindex @code{server}, command prefix
24396 The server prefix does not affect the recording of values into the value
24397 history; to print a value without recording it into the value history,
24398 use the @code{output} command instead of the @code{print} command.
24400 Here is the description of @value{GDBN} commands related to command
24404 @cindex history substitution
24405 @cindex history file
24406 @kindex set history filename
24407 @cindex @env{GDBHISTFILE}, environment variable
24408 @item set history filename @var{fname}
24409 Set the name of the @value{GDBN} command history file to @var{fname}.
24410 This is the file where @value{GDBN} reads an initial command history
24411 list, and where it writes the command history from this session when it
24412 exits. You can access this list through history expansion or through
24413 the history command editing characters listed below. This file defaults
24414 to the value of the environment variable @code{GDBHISTFILE}, or to
24415 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
24418 @cindex save command history
24419 @kindex set history save
24420 @item set history save
24421 @itemx set history save on
24422 Record command history in a file, whose name may be specified with the
24423 @code{set history filename} command. By default, this option is disabled.
24425 @item set history save off
24426 Stop recording command history in a file.
24428 @cindex history size
24429 @kindex set history size
24430 @cindex @env{GDBHISTSIZE}, environment variable
24431 @item set history size @var{size}
24432 @itemx set history size unlimited
24433 Set the number of commands which @value{GDBN} keeps in its history list.
24434 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
24435 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
24436 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
24437 either a negative number or the empty string, then the number of commands
24438 @value{GDBN} keeps in the history list is unlimited.
24440 @cindex remove duplicate history
24441 @kindex set history remove-duplicates
24442 @item set history remove-duplicates @var{count}
24443 @itemx set history remove-duplicates unlimited
24444 Control the removal of duplicate history entries in the command history list.
24445 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
24446 history entries and remove the first entry that is a duplicate of the current
24447 entry being added to the command history list. If @var{count} is
24448 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
24449 removal of duplicate history entries is disabled.
24451 Only history entries added during the current session are considered for
24452 removal. This option is set to 0 by default.
24456 History expansion assigns special meaning to the character @kbd{!}.
24457 @ifset SYSTEM_READLINE
24458 @xref{Event Designators, , , history, GNU History Library},
24460 @ifclear SYSTEM_READLINE
24461 @xref{Event Designators},
24465 @cindex history expansion, turn on/off
24466 Since @kbd{!} is also the logical not operator in C, history expansion
24467 is off by default. If you decide to enable history expansion with the
24468 @code{set history expansion on} command, you may sometimes need to
24469 follow @kbd{!} (when it is used as logical not, in an expression) with
24470 a space or a tab to prevent it from being expanded. The readline
24471 history facilities do not attempt substitution on the strings
24472 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
24474 The commands to control history expansion are:
24477 @item set history expansion on
24478 @itemx set history expansion
24479 @kindex set history expansion
24480 Enable history expansion. History expansion is off by default.
24482 @item set history expansion off
24483 Disable history expansion.
24486 @kindex show history
24488 @itemx show history filename
24489 @itemx show history save
24490 @itemx show history size
24491 @itemx show history expansion
24492 These commands display the state of the @value{GDBN} history parameters.
24493 @code{show history} by itself displays all four states.
24498 @kindex show commands
24499 @cindex show last commands
24500 @cindex display command history
24501 @item show commands
24502 Display the last ten commands in the command history.
24504 @item show commands @var{n}
24505 Print ten commands centered on command number @var{n}.
24507 @item show commands +
24508 Print ten commands just after the commands last printed.
24512 @section Screen Size
24513 @cindex size of screen
24514 @cindex screen size
24517 @cindex pauses in output
24519 Certain commands to @value{GDBN} may produce large amounts of
24520 information output to the screen. To help you read all of it,
24521 @value{GDBN} pauses and asks you for input at the end of each page of
24522 output. Type @key{RET} when you want to see one more page of output,
24523 @kbd{q} to discard the remaining output, or @kbd{c} to continue
24524 without paging for the rest of the current command. Also, the screen
24525 width setting determines when to wrap lines of output. Depending on
24526 what is being printed, @value{GDBN} tries to break the line at a
24527 readable place, rather than simply letting it overflow onto the
24530 Normally @value{GDBN} knows the size of the screen from the terminal
24531 driver software. For example, on Unix @value{GDBN} uses the termcap data base
24532 together with the value of the @code{TERM} environment variable and the
24533 @code{stty rows} and @code{stty cols} settings. If this is not correct,
24534 you can override it with the @code{set height} and @code{set
24541 @kindex show height
24542 @item set height @var{lpp}
24543 @itemx set height unlimited
24545 @itemx set width @var{cpl}
24546 @itemx set width unlimited
24548 These @code{set} commands specify a screen height of @var{lpp} lines and
24549 a screen width of @var{cpl} characters. The associated @code{show}
24550 commands display the current settings.
24552 If you specify a height of either @code{unlimited} or zero lines,
24553 @value{GDBN} does not pause during output no matter how long the
24554 output is. This is useful if output is to a file or to an editor
24557 Likewise, you can specify @samp{set width unlimited} or @samp{set
24558 width 0} to prevent @value{GDBN} from wrapping its output.
24560 @item set pagination on
24561 @itemx set pagination off
24562 @kindex set pagination
24563 Turn the output pagination on or off; the default is on. Turning
24564 pagination off is the alternative to @code{set height unlimited}. Note that
24565 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
24566 Options, -batch}) also automatically disables pagination.
24568 @item show pagination
24569 @kindex show pagination
24570 Show the current pagination mode.
24573 @node Output Styling
24574 @section Output Styling
24580 @value{GDBN} can style its output on a capable terminal. This is
24581 enabled by default on most systems, but disabled by default when in
24582 batch mode (@pxref{Mode Options}). Various style settings are available;
24583 and styles can also be disabled entirely.
24586 @item set style enabled @samp{on|off}
24587 Enable or disable all styling. The default is host-dependent, with
24588 most hosts defaulting to @samp{on}.
24590 @item show style enabled
24591 Show the current state of styling.
24593 @item set style sources @samp{on|off}
24594 Enable or disable source code styling. This affects whether source
24595 code, such as the output of the @code{list} command, is styled. Note
24596 that source styling only works if styling in general is enabled, and
24597 if @value{GDBN} was linked with the GNU Source Highlight library. The
24598 default is @samp{on}.
24600 @item show style sources
24601 Show the current state of source code styling.
24604 Subcommands of @code{set style} control specific forms of styling.
24605 These subcommands all follow the same pattern: each style-able object
24606 can be styled with a foreground color, a background color, and an
24609 For example, the style of file names can be controlled using the
24610 @code{set style filename} group of commands:
24613 @item set style filename background @var{color}
24614 Set the background to @var{color}. Valid colors are @samp{none}
24615 (meaning the terminal's default color), @samp{black}, @samp{red},
24616 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
24619 @item set style filename foreground @var{color}
24620 Set the foreground to @var{color}. Valid colors are @samp{none}
24621 (meaning the terminal's default color), @samp{black}, @samp{red},
24622 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
24625 @item set style filename intensity @var{value}
24626 Set the intensity to @var{value}. Valid intensities are @samp{normal}
24627 (the default), @samp{bold}, and @samp{dim}.
24630 The style-able objects are:
24633 Control the styling of file names. By default, this style's
24634 foreground color is green.
24637 Control the styling of function names. These are managed with the
24638 @code{set style function} family of commands. By default, this
24639 style's foreground color is yellow.
24642 Control the styling of variable names. These are managed with the
24643 @code{set style variable} family of commands. By default, this style's
24644 foreground color is cyan.
24647 Control the styling of addresses. These are managed with the
24648 @code{set style address} family of commands. By default, this style's
24649 foreground color is blue.
24654 @cindex number representation
24655 @cindex entering numbers
24657 You can always enter numbers in octal, decimal, or hexadecimal in
24658 @value{GDBN} by the usual conventions: octal numbers begin with
24659 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
24660 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
24661 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
24662 10; likewise, the default display for numbers---when no particular
24663 format is specified---is base 10. You can change the default base for
24664 both input and output with the commands described below.
24667 @kindex set input-radix
24668 @item set input-radix @var{base}
24669 Set the default base for numeric input. Supported choices
24670 for @var{base} are decimal 8, 10, or 16. The base must itself be
24671 specified either unambiguously or using the current input radix; for
24675 set input-radix 012
24676 set input-radix 10.
24677 set input-radix 0xa
24681 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
24682 leaves the input radix unchanged, no matter what it was, since
24683 @samp{10}, being without any leading or trailing signs of its base, is
24684 interpreted in the current radix. Thus, if the current radix is 16,
24685 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
24688 @kindex set output-radix
24689 @item set output-radix @var{base}
24690 Set the default base for numeric display. Supported choices
24691 for @var{base} are decimal 8, 10, or 16. The base must itself be
24692 specified either unambiguously or using the current input radix.
24694 @kindex show input-radix
24695 @item show input-radix
24696 Display the current default base for numeric input.
24698 @kindex show output-radix
24699 @item show output-radix
24700 Display the current default base for numeric display.
24702 @item set radix @r{[}@var{base}@r{]}
24706 These commands set and show the default base for both input and output
24707 of numbers. @code{set radix} sets the radix of input and output to
24708 the same base; without an argument, it resets the radix back to its
24709 default value of 10.
24714 @section Configuring the Current ABI
24716 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
24717 application automatically. However, sometimes you need to override its
24718 conclusions. Use these commands to manage @value{GDBN}'s view of the
24724 @cindex Newlib OS ABI and its influence on the longjmp handling
24726 One @value{GDBN} configuration can debug binaries for multiple operating
24727 system targets, either via remote debugging or native emulation.
24728 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
24729 but you can override its conclusion using the @code{set osabi} command.
24730 One example where this is useful is in debugging of binaries which use
24731 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
24732 not have the same identifying marks that the standard C library for your
24735 When @value{GDBN} is debugging the AArch64 architecture, it provides a
24736 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
24737 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
24738 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
24742 Show the OS ABI currently in use.
24745 With no argument, show the list of registered available OS ABI's.
24747 @item set osabi @var{abi}
24748 Set the current OS ABI to @var{abi}.
24751 @cindex float promotion
24753 Generally, the way that an argument of type @code{float} is passed to a
24754 function depends on whether the function is prototyped. For a prototyped
24755 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
24756 according to the architecture's convention for @code{float}. For unprototyped
24757 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
24758 @code{double} and then passed.
24760 Unfortunately, some forms of debug information do not reliably indicate whether
24761 a function is prototyped. If @value{GDBN} calls a function that is not marked
24762 as prototyped, it consults @kbd{set coerce-float-to-double}.
24765 @kindex set coerce-float-to-double
24766 @item set coerce-float-to-double
24767 @itemx set coerce-float-to-double on
24768 Arguments of type @code{float} will be promoted to @code{double} when passed
24769 to an unprototyped function. This is the default setting.
24771 @item set coerce-float-to-double off
24772 Arguments of type @code{float} will be passed directly to unprototyped
24775 @kindex show coerce-float-to-double
24776 @item show coerce-float-to-double
24777 Show the current setting of promoting @code{float} to @code{double}.
24781 @kindex show cp-abi
24782 @value{GDBN} needs to know the ABI used for your program's C@t{++}
24783 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
24784 used to build your application. @value{GDBN} only fully supports
24785 programs with a single C@t{++} ABI; if your program contains code using
24786 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
24787 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
24788 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
24789 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
24790 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
24791 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
24796 Show the C@t{++} ABI currently in use.
24799 With no argument, show the list of supported C@t{++} ABI's.
24801 @item set cp-abi @var{abi}
24802 @itemx set cp-abi auto
24803 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
24807 @section Automatically loading associated files
24808 @cindex auto-loading
24810 @value{GDBN} sometimes reads files with commands and settings automatically,
24811 without being explicitly told so by the user. We call this feature
24812 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
24813 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
24814 results or introduce security risks (e.g., if the file comes from untrusted
24818 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
24819 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
24821 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
24822 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
24825 There are various kinds of files @value{GDBN} can automatically load.
24826 In addition to these files, @value{GDBN} supports auto-loading code written
24827 in various extension languages. @xref{Auto-loading extensions}.
24829 Note that loading of these associated files (including the local @file{.gdbinit}
24830 file) requires accordingly configured @code{auto-load safe-path}
24831 (@pxref{Auto-loading safe path}).
24833 For these reasons, @value{GDBN} includes commands and options to let you
24834 control when to auto-load files and which files should be auto-loaded.
24837 @anchor{set auto-load off}
24838 @kindex set auto-load off
24839 @item set auto-load off
24840 Globally disable loading of all auto-loaded files.
24841 You may want to use this command with the @samp{-iex} option
24842 (@pxref{Option -init-eval-command}) such as:
24844 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
24847 Be aware that system init file (@pxref{System-wide configuration})
24848 and init files from your home directory (@pxref{Home Directory Init File})
24849 still get read (as they come from generally trusted directories).
24850 To prevent @value{GDBN} from auto-loading even those init files, use the
24851 @option{-nx} option (@pxref{Mode Options}), in addition to
24852 @code{set auto-load no}.
24854 @anchor{show auto-load}
24855 @kindex show auto-load
24856 @item show auto-load
24857 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
24861 (gdb) show auto-load
24862 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
24863 libthread-db: Auto-loading of inferior specific libthread_db is on.
24864 local-gdbinit: Auto-loading of .gdbinit script from current directory
24866 python-scripts: Auto-loading of Python scripts is on.
24867 safe-path: List of directories from which it is safe to auto-load files
24868 is $debugdir:$datadir/auto-load.
24869 scripts-directory: List of directories from which to load auto-loaded scripts
24870 is $debugdir:$datadir/auto-load.
24873 @anchor{info auto-load}
24874 @kindex info auto-load
24875 @item info auto-load
24876 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
24880 (gdb) info auto-load
24883 Yes /home/user/gdb/gdb-gdb.gdb
24884 libthread-db: No auto-loaded libthread-db.
24885 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
24889 Yes /home/user/gdb/gdb-gdb.py
24893 These are @value{GDBN} control commands for the auto-loading:
24895 @multitable @columnfractions .5 .5
24896 @item @xref{set auto-load off}.
24897 @tab Disable auto-loading globally.
24898 @item @xref{show auto-load}.
24899 @tab Show setting of all kinds of files.
24900 @item @xref{info auto-load}.
24901 @tab Show state of all kinds of files.
24902 @item @xref{set auto-load gdb-scripts}.
24903 @tab Control for @value{GDBN} command scripts.
24904 @item @xref{show auto-load gdb-scripts}.
24905 @tab Show setting of @value{GDBN} command scripts.
24906 @item @xref{info auto-load gdb-scripts}.
24907 @tab Show state of @value{GDBN} command scripts.
24908 @item @xref{set auto-load python-scripts}.
24909 @tab Control for @value{GDBN} Python scripts.
24910 @item @xref{show auto-load python-scripts}.
24911 @tab Show setting of @value{GDBN} Python scripts.
24912 @item @xref{info auto-load python-scripts}.
24913 @tab Show state of @value{GDBN} Python scripts.
24914 @item @xref{set auto-load guile-scripts}.
24915 @tab Control for @value{GDBN} Guile scripts.
24916 @item @xref{show auto-load guile-scripts}.
24917 @tab Show setting of @value{GDBN} Guile scripts.
24918 @item @xref{info auto-load guile-scripts}.
24919 @tab Show state of @value{GDBN} Guile scripts.
24920 @item @xref{set auto-load scripts-directory}.
24921 @tab Control for @value{GDBN} auto-loaded scripts location.
24922 @item @xref{show auto-load scripts-directory}.
24923 @tab Show @value{GDBN} auto-loaded scripts location.
24924 @item @xref{add-auto-load-scripts-directory}.
24925 @tab Add directory for auto-loaded scripts location list.
24926 @item @xref{set auto-load local-gdbinit}.
24927 @tab Control for init file in the current directory.
24928 @item @xref{show auto-load local-gdbinit}.
24929 @tab Show setting of init file in the current directory.
24930 @item @xref{info auto-load local-gdbinit}.
24931 @tab Show state of init file in the current directory.
24932 @item @xref{set auto-load libthread-db}.
24933 @tab Control for thread debugging library.
24934 @item @xref{show auto-load libthread-db}.
24935 @tab Show setting of thread debugging library.
24936 @item @xref{info auto-load libthread-db}.
24937 @tab Show state of thread debugging library.
24938 @item @xref{set auto-load safe-path}.
24939 @tab Control directories trusted for automatic loading.
24940 @item @xref{show auto-load safe-path}.
24941 @tab Show directories trusted for automatic loading.
24942 @item @xref{add-auto-load-safe-path}.
24943 @tab Add directory trusted for automatic loading.
24946 @node Init File in the Current Directory
24947 @subsection Automatically loading init file in the current directory
24948 @cindex auto-loading init file in the current directory
24950 By default, @value{GDBN} reads and executes the canned sequences of commands
24951 from init file (if any) in the current working directory,
24952 see @ref{Init File in the Current Directory during Startup}.
24954 Note that loading of this local @file{.gdbinit} file also requires accordingly
24955 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24958 @anchor{set auto-load local-gdbinit}
24959 @kindex set auto-load local-gdbinit
24960 @item set auto-load local-gdbinit [on|off]
24961 Enable or disable the auto-loading of canned sequences of commands
24962 (@pxref{Sequences}) found in init file in the current directory.
24964 @anchor{show auto-load local-gdbinit}
24965 @kindex show auto-load local-gdbinit
24966 @item show auto-load local-gdbinit
24967 Show whether auto-loading of canned sequences of commands from init file in the
24968 current directory is enabled or disabled.
24970 @anchor{info auto-load local-gdbinit}
24971 @kindex info auto-load local-gdbinit
24972 @item info auto-load local-gdbinit
24973 Print whether canned sequences of commands from init file in the
24974 current directory have been auto-loaded.
24977 @node libthread_db.so.1 file
24978 @subsection Automatically loading thread debugging library
24979 @cindex auto-loading libthread_db.so.1
24981 This feature is currently present only on @sc{gnu}/Linux native hosts.
24983 @value{GDBN} reads in some cases thread debugging library from places specific
24984 to the inferior (@pxref{set libthread-db-search-path}).
24986 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
24987 without checking this @samp{set auto-load libthread-db} switch as system
24988 libraries have to be trusted in general. In all other cases of
24989 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
24990 auto-load libthread-db} is enabled before trying to open such thread debugging
24993 Note that loading of this debugging library also requires accordingly configured
24994 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24997 @anchor{set auto-load libthread-db}
24998 @kindex set auto-load libthread-db
24999 @item set auto-load libthread-db [on|off]
25000 Enable or disable the auto-loading of inferior specific thread debugging library.
25002 @anchor{show auto-load libthread-db}
25003 @kindex show auto-load libthread-db
25004 @item show auto-load libthread-db
25005 Show whether auto-loading of inferior specific thread debugging library is
25006 enabled or disabled.
25008 @anchor{info auto-load libthread-db}
25009 @kindex info auto-load libthread-db
25010 @item info auto-load libthread-db
25011 Print the list of all loaded inferior specific thread debugging libraries and
25012 for each such library print list of inferior @var{pid}s using it.
25015 @node Auto-loading safe path
25016 @subsection Security restriction for auto-loading
25017 @cindex auto-loading safe-path
25019 As the files of inferior can come from untrusted source (such as submitted by
25020 an application user) @value{GDBN} does not always load any files automatically.
25021 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
25022 directories trusted for loading files not explicitly requested by user.
25023 Each directory can also be a shell wildcard pattern.
25025 If the path is not set properly you will see a warning and the file will not
25030 Reading symbols from /home/user/gdb/gdb...done.
25031 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
25032 declined by your `auto-load safe-path' set
25033 to "$debugdir:$datadir/auto-load".
25034 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
25035 declined by your `auto-load safe-path' set
25036 to "$debugdir:$datadir/auto-load".
25040 To instruct @value{GDBN} to go ahead and use the init files anyway,
25041 invoke @value{GDBN} like this:
25044 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
25047 The list of trusted directories is controlled by the following commands:
25050 @anchor{set auto-load safe-path}
25051 @kindex set auto-load safe-path
25052 @item set auto-load safe-path @r{[}@var{directories}@r{]}
25053 Set the list of directories (and their subdirectories) trusted for automatic
25054 loading and execution of scripts. You can also enter a specific trusted file.
25055 Each directory can also be a shell wildcard pattern; wildcards do not match
25056 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
25057 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
25058 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
25059 its default value as specified during @value{GDBN} compilation.
25061 The list of directories uses path separator (@samp{:} on GNU and Unix
25062 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25063 to the @env{PATH} environment variable.
25065 @anchor{show auto-load safe-path}
25066 @kindex show auto-load safe-path
25067 @item show auto-load safe-path
25068 Show the list of directories trusted for automatic loading and execution of
25071 @anchor{add-auto-load-safe-path}
25072 @kindex add-auto-load-safe-path
25073 @item add-auto-load-safe-path
25074 Add an entry (or list of entries) to the list of directories trusted for
25075 automatic loading and execution of scripts. Multiple entries may be delimited
25076 by the host platform path separator in use.
25079 This variable defaults to what @code{--with-auto-load-dir} has been configured
25080 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
25081 substitution applies the same as for @ref{set auto-load scripts-directory}.
25082 The default @code{set auto-load safe-path} value can be also overriden by
25083 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
25085 Setting this variable to @file{/} disables this security protection,
25086 corresponding @value{GDBN} configuration option is
25087 @option{--without-auto-load-safe-path}.
25088 This variable is supposed to be set to the system directories writable by the
25089 system superuser only. Users can add their source directories in init files in
25090 their home directories (@pxref{Home Directory Init File}). See also deprecated
25091 init file in the current directory
25092 (@pxref{Init File in the Current Directory during Startup}).
25094 To force @value{GDBN} to load the files it declined to load in the previous
25095 example, you could use one of the following ways:
25098 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
25099 Specify this trusted directory (or a file) as additional component of the list.
25100 You have to specify also any existing directories displayed by
25101 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
25103 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
25104 Specify this directory as in the previous case but just for a single
25105 @value{GDBN} session.
25107 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
25108 Disable auto-loading safety for a single @value{GDBN} session.
25109 This assumes all the files you debug during this @value{GDBN} session will come
25110 from trusted sources.
25112 @item @kbd{./configure --without-auto-load-safe-path}
25113 During compilation of @value{GDBN} you may disable any auto-loading safety.
25114 This assumes all the files you will ever debug with this @value{GDBN} come from
25118 On the other hand you can also explicitly forbid automatic files loading which
25119 also suppresses any such warning messages:
25122 @item @kbd{gdb -iex "set auto-load no" @dots{}}
25123 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
25125 @item @file{~/.gdbinit}: @samp{set auto-load no}
25126 Disable auto-loading globally for the user
25127 (@pxref{Home Directory Init File}). While it is improbable, you could also
25128 use system init file instead (@pxref{System-wide configuration}).
25131 This setting applies to the file names as entered by user. If no entry matches
25132 @value{GDBN} tries as a last resort to also resolve all the file names into
25133 their canonical form (typically resolving symbolic links) and compare the
25134 entries again. @value{GDBN} already canonicalizes most of the filenames on its
25135 own before starting the comparison so a canonical form of directories is
25136 recommended to be entered.
25138 @node Auto-loading verbose mode
25139 @subsection Displaying files tried for auto-load
25140 @cindex auto-loading verbose mode
25142 For better visibility of all the file locations where you can place scripts to
25143 be auto-loaded with inferior --- or to protect yourself against accidental
25144 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
25145 all the files attempted to be loaded. Both existing and non-existing files may
25148 For example the list of directories from which it is safe to auto-load files
25149 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
25150 may not be too obvious while setting it up.
25153 (gdb) set debug auto-load on
25154 (gdb) file ~/src/t/true
25155 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
25156 for objfile "/tmp/true".
25157 auto-load: Updating directories of "/usr:/opt".
25158 auto-load: Using directory "/usr".
25159 auto-load: Using directory "/opt".
25160 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
25161 by your `auto-load safe-path' set to "/usr:/opt".
25165 @anchor{set debug auto-load}
25166 @kindex set debug auto-load
25167 @item set debug auto-load [on|off]
25168 Set whether to print the filenames attempted to be auto-loaded.
25170 @anchor{show debug auto-load}
25171 @kindex show debug auto-load
25172 @item show debug auto-load
25173 Show whether printing of the filenames attempted to be auto-loaded is turned
25177 @node Messages/Warnings
25178 @section Optional Warnings and Messages
25180 @cindex verbose operation
25181 @cindex optional warnings
25182 By default, @value{GDBN} is silent about its inner workings. If you are
25183 running on a slow machine, you may want to use the @code{set verbose}
25184 command. This makes @value{GDBN} tell you when it does a lengthy
25185 internal operation, so you will not think it has crashed.
25187 Currently, the messages controlled by @code{set verbose} are those
25188 which announce that the symbol table for a source file is being read;
25189 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
25192 @kindex set verbose
25193 @item set verbose on
25194 Enables @value{GDBN} output of certain informational messages.
25196 @item set verbose off
25197 Disables @value{GDBN} output of certain informational messages.
25199 @kindex show verbose
25201 Displays whether @code{set verbose} is on or off.
25204 By default, if @value{GDBN} encounters bugs in the symbol table of an
25205 object file, it is silent; but if you are debugging a compiler, you may
25206 find this information useful (@pxref{Symbol Errors, ,Errors Reading
25211 @kindex set complaints
25212 @item set complaints @var{limit}
25213 Permits @value{GDBN} to output @var{limit} complaints about each type of
25214 unusual symbols before becoming silent about the problem. Set
25215 @var{limit} to zero to suppress all complaints; set it to a large number
25216 to prevent complaints from being suppressed.
25218 @kindex show complaints
25219 @item show complaints
25220 Displays how many symbol complaints @value{GDBN} is permitted to produce.
25224 @anchor{confirmation requests}
25225 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
25226 lot of stupid questions to confirm certain commands. For example, if
25227 you try to run a program which is already running:
25231 The program being debugged has been started already.
25232 Start it from the beginning? (y or n)
25235 If you are willing to unflinchingly face the consequences of your own
25236 commands, you can disable this ``feature'':
25240 @kindex set confirm
25242 @cindex confirmation
25243 @cindex stupid questions
25244 @item set confirm off
25245 Disables confirmation requests. Note that running @value{GDBN} with
25246 the @option{--batch} option (@pxref{Mode Options, -batch}) also
25247 automatically disables confirmation requests.
25249 @item set confirm on
25250 Enables confirmation requests (the default).
25252 @kindex show confirm
25254 Displays state of confirmation requests.
25258 @cindex command tracing
25259 If you need to debug user-defined commands or sourced files you may find it
25260 useful to enable @dfn{command tracing}. In this mode each command will be
25261 printed as it is executed, prefixed with one or more @samp{+} symbols, the
25262 quantity denoting the call depth of each command.
25265 @kindex set trace-commands
25266 @cindex command scripts, debugging
25267 @item set trace-commands on
25268 Enable command tracing.
25269 @item set trace-commands off
25270 Disable command tracing.
25271 @item show trace-commands
25272 Display the current state of command tracing.
25275 @node Debugging Output
25276 @section Optional Messages about Internal Happenings
25277 @cindex optional debugging messages
25279 @value{GDBN} has commands that enable optional debugging messages from
25280 various @value{GDBN} subsystems; normally these commands are of
25281 interest to @value{GDBN} maintainers, or when reporting a bug. This
25282 section documents those commands.
25285 @kindex set exec-done-display
25286 @item set exec-done-display
25287 Turns on or off the notification of asynchronous commands'
25288 completion. When on, @value{GDBN} will print a message when an
25289 asynchronous command finishes its execution. The default is off.
25290 @kindex show exec-done-display
25291 @item show exec-done-display
25292 Displays the current setting of asynchronous command completion
25295 @cindex ARM AArch64
25296 @item set debug aarch64
25297 Turns on or off display of debugging messages related to ARM AArch64.
25298 The default is off.
25300 @item show debug aarch64
25301 Displays the current state of displaying debugging messages related to
25303 @cindex gdbarch debugging info
25304 @cindex architecture debugging info
25305 @item set debug arch
25306 Turns on or off display of gdbarch debugging info. The default is off
25307 @item show debug arch
25308 Displays the current state of displaying gdbarch debugging info.
25309 @item set debug aix-solib
25310 @cindex AIX shared library debugging
25311 Control display of debugging messages from the AIX shared library
25312 support module. The default is off.
25313 @item show debug aix-thread
25314 Show the current state of displaying AIX shared library debugging messages.
25315 @item set debug aix-thread
25316 @cindex AIX threads
25317 Display debugging messages about inner workings of the AIX thread
25319 @item show debug aix-thread
25320 Show the current state of AIX thread debugging info display.
25321 @item set debug check-physname
25323 Check the results of the ``physname'' computation. When reading DWARF
25324 debugging information for C@t{++}, @value{GDBN} attempts to compute
25325 each entity's name. @value{GDBN} can do this computation in two
25326 different ways, depending on exactly what information is present.
25327 When enabled, this setting causes @value{GDBN} to compute the names
25328 both ways and display any discrepancies.
25329 @item show debug check-physname
25330 Show the current state of ``physname'' checking.
25331 @item set debug coff-pe-read
25332 @cindex COFF/PE exported symbols
25333 Control display of debugging messages related to reading of COFF/PE
25334 exported symbols. The default is off.
25335 @item show debug coff-pe-read
25336 Displays the current state of displaying debugging messages related to
25337 reading of COFF/PE exported symbols.
25338 @item set debug dwarf-die
25340 Dump DWARF DIEs after they are read in.
25341 The value is the number of nesting levels to print.
25342 A value of zero turns off the display.
25343 @item show debug dwarf-die
25344 Show the current state of DWARF DIE debugging.
25345 @item set debug dwarf-line
25346 @cindex DWARF Line Tables
25347 Turns on or off display of debugging messages related to reading
25348 DWARF line tables. The default is 0 (off).
25349 A value of 1 provides basic information.
25350 A value greater than 1 provides more verbose information.
25351 @item show debug dwarf-line
25352 Show the current state of DWARF line table debugging.
25353 @item set debug dwarf-read
25354 @cindex DWARF Reading
25355 Turns on or off display of debugging messages related to reading
25356 DWARF debug info. The default is 0 (off).
25357 A value of 1 provides basic information.
25358 A value greater than 1 provides more verbose information.
25359 @item show debug dwarf-read
25360 Show the current state of DWARF reader debugging.
25361 @item set debug displaced
25362 @cindex displaced stepping debugging info
25363 Turns on or off display of @value{GDBN} debugging info for the
25364 displaced stepping support. The default is off.
25365 @item show debug displaced
25366 Displays the current state of displaying @value{GDBN} debugging info
25367 related to displaced stepping.
25368 @item set debug event
25369 @cindex event debugging info
25370 Turns on or off display of @value{GDBN} event debugging info. The
25372 @item show debug event
25373 Displays the current state of displaying @value{GDBN} event debugging
25375 @item set debug expression
25376 @cindex expression debugging info
25377 Turns on or off display of debugging info about @value{GDBN}
25378 expression parsing. The default is off.
25379 @item show debug expression
25380 Displays the current state of displaying debugging info about
25381 @value{GDBN} expression parsing.
25382 @item set debug fbsd-lwp
25383 @cindex FreeBSD LWP debug messages
25384 Turns on or off debugging messages from the FreeBSD LWP debug support.
25385 @item show debug fbsd-lwp
25386 Show the current state of FreeBSD LWP debugging messages.
25387 @item set debug fbsd-nat
25388 @cindex FreeBSD native target debug messages
25389 Turns on or off debugging messages from the FreeBSD native target.
25390 @item show debug fbsd-nat
25391 Show the current state of FreeBSD native target debugging messages.
25392 @item set debug frame
25393 @cindex frame debugging info
25394 Turns on or off display of @value{GDBN} frame debugging info. The
25396 @item show debug frame
25397 Displays the current state of displaying @value{GDBN} frame debugging
25399 @item set debug gnu-nat
25400 @cindex @sc{gnu}/Hurd debug messages
25401 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
25402 @item show debug gnu-nat
25403 Show the current state of @sc{gnu}/Hurd debugging messages.
25404 @item set debug infrun
25405 @cindex inferior debugging info
25406 Turns on or off display of @value{GDBN} debugging info for running the inferior.
25407 The default is off. @file{infrun.c} contains GDB's runtime state machine used
25408 for implementing operations such as single-stepping the inferior.
25409 @item show debug infrun
25410 Displays the current state of @value{GDBN} inferior debugging.
25411 @item set debug jit
25412 @cindex just-in-time compilation, debugging messages
25413 Turn on or off debugging messages from JIT debug support.
25414 @item show debug jit
25415 Displays the current state of @value{GDBN} JIT debugging.
25416 @item set debug lin-lwp
25417 @cindex @sc{gnu}/Linux LWP debug messages
25418 @cindex Linux lightweight processes
25419 Turn on or off debugging messages from the Linux LWP debug support.
25420 @item show debug lin-lwp
25421 Show the current state of Linux LWP debugging messages.
25422 @item set debug linux-namespaces
25423 @cindex @sc{gnu}/Linux namespaces debug messages
25424 Turn on or off debugging messages from the Linux namespaces debug support.
25425 @item show debug linux-namespaces
25426 Show the current state of Linux namespaces debugging messages.
25427 @item set debug mach-o
25428 @cindex Mach-O symbols processing
25429 Control display of debugging messages related to Mach-O symbols
25430 processing. The default is off.
25431 @item show debug mach-o
25432 Displays the current state of displaying debugging messages related to
25433 reading of COFF/PE exported symbols.
25434 @item set debug notification
25435 @cindex remote async notification debugging info
25436 Turn on or off debugging messages about remote async notification.
25437 The default is off.
25438 @item show debug notification
25439 Displays the current state of remote async notification debugging messages.
25440 @item set debug observer
25441 @cindex observer debugging info
25442 Turns on or off display of @value{GDBN} observer debugging. This
25443 includes info such as the notification of observable events.
25444 @item show debug observer
25445 Displays the current state of observer debugging.
25446 @item set debug overload
25447 @cindex C@t{++} overload debugging info
25448 Turns on or off display of @value{GDBN} C@t{++} overload debugging
25449 info. This includes info such as ranking of functions, etc. The default
25451 @item show debug overload
25452 Displays the current state of displaying @value{GDBN} C@t{++} overload
25454 @cindex expression parser, debugging info
25455 @cindex debug expression parser
25456 @item set debug parser
25457 Turns on or off the display of expression parser debugging output.
25458 Internally, this sets the @code{yydebug} variable in the expression
25459 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
25460 details. The default is off.
25461 @item show debug parser
25462 Show the current state of expression parser debugging.
25463 @cindex packets, reporting on stdout
25464 @cindex serial connections, debugging
25465 @cindex debug remote protocol
25466 @cindex remote protocol debugging
25467 @cindex display remote packets
25468 @item set debug remote
25469 Turns on or off display of reports on all packets sent back and forth across
25470 the serial line to the remote machine. The info is printed on the
25471 @value{GDBN} standard output stream. The default is off.
25472 @item show debug remote
25473 Displays the state of display of remote packets.
25475 @item set debug separate-debug-file
25476 Turns on or off display of debug output about separate debug file search.
25477 @item show debug separate-debug-file
25478 Displays the state of separate debug file search debug output.
25480 @item set debug serial
25481 Turns on or off display of @value{GDBN} serial debugging info. The
25483 @item show debug serial
25484 Displays the current state of displaying @value{GDBN} serial debugging
25486 @item set debug solib-frv
25487 @cindex FR-V shared-library debugging
25488 Turn on or off debugging messages for FR-V shared-library code.
25489 @item show debug solib-frv
25490 Display the current state of FR-V shared-library code debugging
25492 @item set debug symbol-lookup
25493 @cindex symbol lookup
25494 Turns on or off display of debugging messages related to symbol lookup.
25495 The default is 0 (off).
25496 A value of 1 provides basic information.
25497 A value greater than 1 provides more verbose information.
25498 @item show debug symbol-lookup
25499 Show the current state of symbol lookup debugging messages.
25500 @item set debug symfile
25501 @cindex symbol file functions
25502 Turns on or off display of debugging messages related to symbol file functions.
25503 The default is off. @xref{Files}.
25504 @item show debug symfile
25505 Show the current state of symbol file debugging messages.
25506 @item set debug symtab-create
25507 @cindex symbol table creation
25508 Turns on or off display of debugging messages related to symbol table creation.
25509 The default is 0 (off).
25510 A value of 1 provides basic information.
25511 A value greater than 1 provides more verbose information.
25512 @item show debug symtab-create
25513 Show the current state of symbol table creation debugging.
25514 @item set debug target
25515 @cindex target debugging info
25516 Turns on or off display of @value{GDBN} target debugging info. This info
25517 includes what is going on at the target level of GDB, as it happens. The
25518 default is 0. Set it to 1 to track events, and to 2 to also track the
25519 value of large memory transfers.
25520 @item show debug target
25521 Displays the current state of displaying @value{GDBN} target debugging
25523 @item set debug timestamp
25524 @cindex timestampping debugging info
25525 Turns on or off display of timestamps with @value{GDBN} debugging info.
25526 When enabled, seconds and microseconds are displayed before each debugging
25528 @item show debug timestamp
25529 Displays the current state of displaying timestamps with @value{GDBN}
25531 @item set debug varobj
25532 @cindex variable object debugging info
25533 Turns on or off display of @value{GDBN} variable object debugging
25534 info. The default is off.
25535 @item show debug varobj
25536 Displays the current state of displaying @value{GDBN} variable object
25538 @item set debug xml
25539 @cindex XML parser debugging
25540 Turn on or off debugging messages for built-in XML parsers.
25541 @item show debug xml
25542 Displays the current state of XML debugging messages.
25545 @node Other Misc Settings
25546 @section Other Miscellaneous Settings
25547 @cindex miscellaneous settings
25550 @kindex set interactive-mode
25551 @item set interactive-mode
25552 If @code{on}, forces @value{GDBN} to assume that GDB was started
25553 in a terminal. In practice, this means that @value{GDBN} should wait
25554 for the user to answer queries generated by commands entered at
25555 the command prompt. If @code{off}, forces @value{GDBN} to operate
25556 in the opposite mode, and it uses the default answers to all queries.
25557 If @code{auto} (the default), @value{GDBN} tries to determine whether
25558 its standard input is a terminal, and works in interactive-mode if it
25559 is, non-interactively otherwise.
25561 In the vast majority of cases, the debugger should be able to guess
25562 correctly which mode should be used. But this setting can be useful
25563 in certain specific cases, such as running a MinGW @value{GDBN}
25564 inside a cygwin window.
25566 @kindex show interactive-mode
25567 @item show interactive-mode
25568 Displays whether the debugger is operating in interactive mode or not.
25571 @node Extending GDB
25572 @chapter Extending @value{GDBN}
25573 @cindex extending GDB
25575 @value{GDBN} provides several mechanisms for extension.
25576 @value{GDBN} also provides the ability to automatically load
25577 extensions when it reads a file for debugging. This allows the
25578 user to automatically customize @value{GDBN} for the program
25582 * Sequences:: Canned Sequences of @value{GDBN} Commands
25583 * Python:: Extending @value{GDBN} using Python
25584 * Guile:: Extending @value{GDBN} using Guile
25585 * Auto-loading extensions:: Automatically loading extensions
25586 * Multiple Extension Languages:: Working with multiple extension languages
25587 * Aliases:: Creating new spellings of existing commands
25590 To facilitate the use of extension languages, @value{GDBN} is capable
25591 of evaluating the contents of a file. When doing so, @value{GDBN}
25592 can recognize which extension language is being used by looking at
25593 the filename extension. Files with an unrecognized filename extension
25594 are always treated as a @value{GDBN} Command Files.
25595 @xref{Command Files,, Command files}.
25597 You can control how @value{GDBN} evaluates these files with the following
25601 @kindex set script-extension
25602 @kindex show script-extension
25603 @item set script-extension off
25604 All scripts are always evaluated as @value{GDBN} Command Files.
25606 @item set script-extension soft
25607 The debugger determines the scripting language based on filename
25608 extension. If this scripting language is supported, @value{GDBN}
25609 evaluates the script using that language. Otherwise, it evaluates
25610 the file as a @value{GDBN} Command File.
25612 @item set script-extension strict
25613 The debugger determines the scripting language based on filename
25614 extension, and evaluates the script using that language. If the
25615 language is not supported, then the evaluation fails.
25617 @item show script-extension
25618 Display the current value of the @code{script-extension} option.
25623 @section Canned Sequences of Commands
25625 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
25626 Command Lists}), @value{GDBN} provides two ways to store sequences of
25627 commands for execution as a unit: user-defined commands and command
25631 * Define:: How to define your own commands
25632 * Hooks:: Hooks for user-defined commands
25633 * Command Files:: How to write scripts of commands to be stored in a file
25634 * Output:: Commands for controlled output
25635 * Auto-loading sequences:: Controlling auto-loaded command files
25639 @subsection User-defined Commands
25641 @cindex user-defined command
25642 @cindex arguments, to user-defined commands
25643 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
25644 which you assign a new name as a command. This is done with the
25645 @code{define} command. User commands may accept an unlimited number of arguments
25646 separated by whitespace. Arguments are accessed within the user command
25647 via @code{$arg0@dots{}$argN}. A trivial example:
25651 print $arg0 + $arg1 + $arg2
25656 To execute the command use:
25663 This defines the command @code{adder}, which prints the sum of
25664 its three arguments. Note the arguments are text substitutions, so they may
25665 reference variables, use complex expressions, or even perform inferior
25668 @cindex argument count in user-defined commands
25669 @cindex how many arguments (user-defined commands)
25670 In addition, @code{$argc} may be used to find out how many arguments have
25676 print $arg0 + $arg1
25679 print $arg0 + $arg1 + $arg2
25684 Combining with the @code{eval} command (@pxref{eval}) makes it easier
25685 to process a variable number of arguments:
25692 eval "set $sum = $sum + $arg%d", $i
25702 @item define @var{commandname}
25703 Define a command named @var{commandname}. If there is already a command
25704 by that name, you are asked to confirm that you want to redefine it.
25705 The argument @var{commandname} may be a bare command name consisting of letters,
25706 numbers, dashes, and underscores. It may also start with any predefined
25707 prefix command. For example, @samp{define target my-target} creates
25708 a user-defined @samp{target my-target} command.
25710 The definition of the command is made up of other @value{GDBN} command lines,
25711 which are given following the @code{define} command. The end of these
25712 commands is marked by a line containing @code{end}.
25715 @kindex end@r{ (user-defined commands)}
25716 @item document @var{commandname}
25717 Document the user-defined command @var{commandname}, so that it can be
25718 accessed by @code{help}. The command @var{commandname} must already be
25719 defined. This command reads lines of documentation just as @code{define}
25720 reads the lines of the command definition, ending with @code{end}.
25721 After the @code{document} command is finished, @code{help} on command
25722 @var{commandname} displays the documentation you have written.
25724 You may use the @code{document} command again to change the
25725 documentation of a command. Redefining the command with @code{define}
25726 does not change the documentation.
25728 @kindex dont-repeat
25729 @cindex don't repeat command
25731 Used inside a user-defined command, this tells @value{GDBN} that this
25732 command should not be repeated when the user hits @key{RET}
25733 (@pxref{Command Syntax, repeat last command}).
25735 @kindex help user-defined
25736 @item help user-defined
25737 List all user-defined commands and all python commands defined in class
25738 COMAND_USER. The first line of the documentation or docstring is
25743 @itemx show user @var{commandname}
25744 Display the @value{GDBN} commands used to define @var{commandname} (but
25745 not its documentation). If no @var{commandname} is given, display the
25746 definitions for all user-defined commands.
25747 This does not work for user-defined python commands.
25749 @cindex infinite recursion in user-defined commands
25750 @kindex show max-user-call-depth
25751 @kindex set max-user-call-depth
25752 @item show max-user-call-depth
25753 @itemx set max-user-call-depth
25754 The value of @code{max-user-call-depth} controls how many recursion
25755 levels are allowed in user-defined commands before @value{GDBN} suspects an
25756 infinite recursion and aborts the command.
25757 This does not apply to user-defined python commands.
25760 In addition to the above commands, user-defined commands frequently
25761 use control flow commands, described in @ref{Command Files}.
25763 When user-defined commands are executed, the
25764 commands of the definition are not printed. An error in any command
25765 stops execution of the user-defined command.
25767 If used interactively, commands that would ask for confirmation proceed
25768 without asking when used inside a user-defined command. Many @value{GDBN}
25769 commands that normally print messages to say what they are doing omit the
25770 messages when used in a user-defined command.
25773 @subsection User-defined Command Hooks
25774 @cindex command hooks
25775 @cindex hooks, for commands
25776 @cindex hooks, pre-command
25779 You may define @dfn{hooks}, which are a special kind of user-defined
25780 command. Whenever you run the command @samp{foo}, if the user-defined
25781 command @samp{hook-foo} exists, it is executed (with no arguments)
25782 before that command.
25784 @cindex hooks, post-command
25786 A hook may also be defined which is run after the command you executed.
25787 Whenever you run the command @samp{foo}, if the user-defined command
25788 @samp{hookpost-foo} exists, it is executed (with no arguments) after
25789 that command. Post-execution hooks may exist simultaneously with
25790 pre-execution hooks, for the same command.
25792 It is valid for a hook to call the command which it hooks. If this
25793 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
25795 @c It would be nice if hookpost could be passed a parameter indicating
25796 @c if the command it hooks executed properly or not. FIXME!
25798 @kindex stop@r{, a pseudo-command}
25799 In addition, a pseudo-command, @samp{stop} exists. Defining
25800 (@samp{hook-stop}) makes the associated commands execute every time
25801 execution stops in your program: before breakpoint commands are run,
25802 displays are printed, or the stack frame is printed.
25804 For example, to ignore @code{SIGALRM} signals while
25805 single-stepping, but treat them normally during normal execution,
25810 handle SIGALRM nopass
25814 handle SIGALRM pass
25817 define hook-continue
25818 handle SIGALRM pass
25822 As a further example, to hook at the beginning and end of the @code{echo}
25823 command, and to add extra text to the beginning and end of the message,
25831 define hookpost-echo
25835 (@value{GDBP}) echo Hello World
25836 <<<---Hello World--->>>
25841 You can define a hook for any single-word command in @value{GDBN}, but
25842 not for command aliases; you should define a hook for the basic command
25843 name, e.g.@: @code{backtrace} rather than @code{bt}.
25844 @c FIXME! So how does Joe User discover whether a command is an alias
25846 You can hook a multi-word command by adding @code{hook-} or
25847 @code{hookpost-} to the last word of the command, e.g.@:
25848 @samp{define target hook-remote} to add a hook to @samp{target remote}.
25850 If an error occurs during the execution of your hook, execution of
25851 @value{GDBN} commands stops and @value{GDBN} issues a prompt
25852 (before the command that you actually typed had a chance to run).
25854 If you try to define a hook which does not match any known command, you
25855 get a warning from the @code{define} command.
25857 @node Command Files
25858 @subsection Command Files
25860 @cindex command files
25861 @cindex scripting commands
25862 A command file for @value{GDBN} is a text file made of lines that are
25863 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
25864 also be included. An empty line in a command file does nothing; it
25865 does not mean to repeat the last command, as it would from the
25868 You can request the execution of a command file with the @code{source}
25869 command. Note that the @code{source} command is also used to evaluate
25870 scripts that are not Command Files. The exact behavior can be configured
25871 using the @code{script-extension} setting.
25872 @xref{Extending GDB,, Extending GDB}.
25876 @cindex execute commands from a file
25877 @item source [-s] [-v] @var{filename}
25878 Execute the command file @var{filename}.
25881 The lines in a command file are generally executed sequentially,
25882 unless the order of execution is changed by one of the
25883 @emph{flow-control commands} described below. The commands are not
25884 printed as they are executed. An error in any command terminates
25885 execution of the command file and control is returned to the console.
25887 @value{GDBN} first searches for @var{filename} in the current directory.
25888 If the file is not found there, and @var{filename} does not specify a
25889 directory, then @value{GDBN} also looks for the file on the source search path
25890 (specified with the @samp{directory} command);
25891 except that @file{$cdir} is not searched because the compilation directory
25892 is not relevant to scripts.
25894 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
25895 on the search path even if @var{filename} specifies a directory.
25896 The search is done by appending @var{filename} to each element of the
25897 search path. So, for example, if @var{filename} is @file{mylib/myscript}
25898 and the search path contains @file{/home/user} then @value{GDBN} will
25899 look for the script @file{/home/user/mylib/myscript}.
25900 The search is also done if @var{filename} is an absolute path.
25901 For example, if @var{filename} is @file{/tmp/myscript} and
25902 the search path contains @file{/home/user} then @value{GDBN} will
25903 look for the script @file{/home/user/tmp/myscript}.
25904 For DOS-like systems, if @var{filename} contains a drive specification,
25905 it is stripped before concatenation. For example, if @var{filename} is
25906 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
25907 will look for the script @file{c:/tmp/myscript}.
25909 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
25910 each command as it is executed. The option must be given before
25911 @var{filename}, and is interpreted as part of the filename anywhere else.
25913 Commands that would ask for confirmation if used interactively proceed
25914 without asking when used in a command file. Many @value{GDBN} commands that
25915 normally print messages to say what they are doing omit the messages
25916 when called from command files.
25918 @value{GDBN} also accepts command input from standard input. In this
25919 mode, normal output goes to standard output and error output goes to
25920 standard error. Errors in a command file supplied on standard input do
25921 not terminate execution of the command file---execution continues with
25925 gdb < cmds > log 2>&1
25928 (The syntax above will vary depending on the shell used.) This example
25929 will execute commands from the file @file{cmds}. All output and errors
25930 would be directed to @file{log}.
25932 Since commands stored on command files tend to be more general than
25933 commands typed interactively, they frequently need to deal with
25934 complicated situations, such as different or unexpected values of
25935 variables and symbols, changes in how the program being debugged is
25936 built, etc. @value{GDBN} provides a set of flow-control commands to
25937 deal with these complexities. Using these commands, you can write
25938 complex scripts that loop over data structures, execute commands
25939 conditionally, etc.
25946 This command allows to include in your script conditionally executed
25947 commands. The @code{if} command takes a single argument, which is an
25948 expression to evaluate. It is followed by a series of commands that
25949 are executed only if the expression is true (its value is nonzero).
25950 There can then optionally be an @code{else} line, followed by a series
25951 of commands that are only executed if the expression was false. The
25952 end of the list is marked by a line containing @code{end}.
25956 This command allows to write loops. Its syntax is similar to
25957 @code{if}: the command takes a single argument, which is an expression
25958 to evaluate, and must be followed by the commands to execute, one per
25959 line, terminated by an @code{end}. These commands are called the
25960 @dfn{body} of the loop. The commands in the body of @code{while} are
25961 executed repeatedly as long as the expression evaluates to true.
25965 This command exits the @code{while} loop in whose body it is included.
25966 Execution of the script continues after that @code{while}s @code{end}
25969 @kindex loop_continue
25970 @item loop_continue
25971 This command skips the execution of the rest of the body of commands
25972 in the @code{while} loop in whose body it is included. Execution
25973 branches to the beginning of the @code{while} loop, where it evaluates
25974 the controlling expression.
25976 @kindex end@r{ (if/else/while commands)}
25978 Terminate the block of commands that are the body of @code{if},
25979 @code{else}, or @code{while} flow-control commands.
25984 @subsection Commands for Controlled Output
25986 During the execution of a command file or a user-defined command, normal
25987 @value{GDBN} output is suppressed; the only output that appears is what is
25988 explicitly printed by the commands in the definition. This section
25989 describes three commands useful for generating exactly the output you
25994 @item echo @var{text}
25995 @c I do not consider backslash-space a standard C escape sequence
25996 @c because it is not in ANSI.
25997 Print @var{text}. Nonprinting characters can be included in
25998 @var{text} using C escape sequences, such as @samp{\n} to print a
25999 newline. @strong{No newline is printed unless you specify one.}
26000 In addition to the standard C escape sequences, a backslash followed
26001 by a space stands for a space. This is useful for displaying a
26002 string with spaces at the beginning or the end, since leading and
26003 trailing spaces are otherwise trimmed from all arguments.
26004 To print @samp{@w{ }and foo =@w{ }}, use the command
26005 @samp{echo \@w{ }and foo = \@w{ }}.
26007 A backslash at the end of @var{text} can be used, as in C, to continue
26008 the command onto subsequent lines. For example,
26011 echo This is some text\n\
26012 which is continued\n\
26013 onto several lines.\n
26016 produces the same output as
26019 echo This is some text\n
26020 echo which is continued\n
26021 echo onto several lines.\n
26025 @item output @var{expression}
26026 Print the value of @var{expression} and nothing but that value: no
26027 newlines, no @samp{$@var{nn} = }. The value is not entered in the
26028 value history either. @xref{Expressions, ,Expressions}, for more information
26031 @item output/@var{fmt} @var{expression}
26032 Print the value of @var{expression} in format @var{fmt}. You can use
26033 the same formats as for @code{print}. @xref{Output Formats,,Output
26034 Formats}, for more information.
26037 @item printf @var{template}, @var{expressions}@dots{}
26038 Print the values of one or more @var{expressions} under the control of
26039 the string @var{template}. To print several values, make
26040 @var{expressions} be a comma-separated list of individual expressions,
26041 which may be either numbers or pointers. Their values are printed as
26042 specified by @var{template}, exactly as a C program would do by
26043 executing the code below:
26046 printf (@var{template}, @var{expressions}@dots{});
26049 As in @code{C} @code{printf}, ordinary characters in @var{template}
26050 are printed verbatim, while @dfn{conversion specification} introduced
26051 by the @samp{%} character cause subsequent @var{expressions} to be
26052 evaluated, their values converted and formatted according to type and
26053 style information encoded in the conversion specifications, and then
26056 For example, you can print two values in hex like this:
26059 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
26062 @code{printf} supports all the standard @code{C} conversion
26063 specifications, including the flags and modifiers between the @samp{%}
26064 character and the conversion letter, with the following exceptions:
26068 The argument-ordering modifiers, such as @samp{2$}, are not supported.
26071 The modifier @samp{*} is not supported for specifying precision or
26075 The @samp{'} flag (for separation of digits into groups according to
26076 @code{LC_NUMERIC'}) is not supported.
26079 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
26083 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
26086 The conversion letters @samp{a} and @samp{A} are not supported.
26090 Note that the @samp{ll} type modifier is supported only if the
26091 underlying @code{C} implementation used to build @value{GDBN} supports
26092 the @code{long long int} type, and the @samp{L} type modifier is
26093 supported only if @code{long double} type is available.
26095 As in @code{C}, @code{printf} supports simple backslash-escape
26096 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
26097 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
26098 single character. Octal and hexadecimal escape sequences are not
26101 Additionally, @code{printf} supports conversion specifications for DFP
26102 (@dfn{Decimal Floating Point}) types using the following length modifiers
26103 together with a floating point specifier.
26108 @samp{H} for printing @code{Decimal32} types.
26111 @samp{D} for printing @code{Decimal64} types.
26114 @samp{DD} for printing @code{Decimal128} types.
26117 If the underlying @code{C} implementation used to build @value{GDBN} has
26118 support for the three length modifiers for DFP types, other modifiers
26119 such as width and precision will also be available for @value{GDBN} to use.
26121 In case there is no such @code{C} support, no additional modifiers will be
26122 available and the value will be printed in the standard way.
26124 Here's an example of printing DFP types using the above conversion letters:
26126 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
26131 @item eval @var{template}, @var{expressions}@dots{}
26132 Convert the values of one or more @var{expressions} under the control of
26133 the string @var{template} to a command line, and call it.
26137 @node Auto-loading sequences
26138 @subsection Controlling auto-loading native @value{GDBN} scripts
26139 @cindex native script auto-loading
26141 When a new object file is read (for example, due to the @code{file}
26142 command, or because the inferior has loaded a shared library),
26143 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
26144 @xref{Auto-loading extensions}.
26146 Auto-loading can be enabled or disabled,
26147 and the list of auto-loaded scripts can be printed.
26150 @anchor{set auto-load gdb-scripts}
26151 @kindex set auto-load gdb-scripts
26152 @item set auto-load gdb-scripts [on|off]
26153 Enable or disable the auto-loading of canned sequences of commands scripts.
26155 @anchor{show auto-load gdb-scripts}
26156 @kindex show auto-load gdb-scripts
26157 @item show auto-load gdb-scripts
26158 Show whether auto-loading of canned sequences of commands scripts is enabled or
26161 @anchor{info auto-load gdb-scripts}
26162 @kindex info auto-load gdb-scripts
26163 @cindex print list of auto-loaded canned sequences of commands scripts
26164 @item info auto-load gdb-scripts [@var{regexp}]
26165 Print the list of all canned sequences of commands scripts that @value{GDBN}
26169 If @var{regexp} is supplied only canned sequences of commands scripts with
26170 matching names are printed.
26172 @c Python docs live in a separate file.
26173 @include python.texi
26175 @c Guile docs live in a separate file.
26176 @include guile.texi
26178 @node Auto-loading extensions
26179 @section Auto-loading extensions
26180 @cindex auto-loading extensions
26182 @value{GDBN} provides two mechanisms for automatically loading extensions
26183 when a new object file is read (for example, due to the @code{file}
26184 command, or because the inferior has loaded a shared library):
26185 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
26186 section of modern file formats like ELF.
26189 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
26190 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
26191 * Which flavor to choose?::
26194 The auto-loading feature is useful for supplying application-specific
26195 debugging commands and features.
26197 Auto-loading can be enabled or disabled,
26198 and the list of auto-loaded scripts can be printed.
26199 See the @samp{auto-loading} section of each extension language
26200 for more information.
26201 For @value{GDBN} command files see @ref{Auto-loading sequences}.
26202 For Python files see @ref{Python Auto-loading}.
26204 Note that loading of this script file also requires accordingly configured
26205 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26207 @node objfile-gdbdotext file
26208 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
26209 @cindex @file{@var{objfile}-gdb.gdb}
26210 @cindex @file{@var{objfile}-gdb.py}
26211 @cindex @file{@var{objfile}-gdb.scm}
26213 When a new object file is read, @value{GDBN} looks for a file named
26214 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
26215 where @var{objfile} is the object file's name and
26216 where @var{ext} is the file extension for the extension language:
26219 @item @file{@var{objfile}-gdb.gdb}
26220 GDB's own command language
26221 @item @file{@var{objfile}-gdb.py}
26223 @item @file{@var{objfile}-gdb.scm}
26227 @var{script-name} is formed by ensuring that the file name of @var{objfile}
26228 is absolute, following all symlinks, and resolving @code{.} and @code{..}
26229 components, and appending the @file{-gdb.@var{ext}} suffix.
26230 If this file exists and is readable, @value{GDBN} will evaluate it as a
26231 script in the specified extension language.
26233 If this file does not exist, then @value{GDBN} will look for
26234 @var{script-name} file in all of the directories as specified below.
26236 Note that loading of these files requires an accordingly configured
26237 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26239 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26240 scripts normally according to its @file{.exe} filename. But if no scripts are
26241 found @value{GDBN} also tries script filenames matching the object file without
26242 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26243 is attempted on any platform. This makes the script filenames compatible
26244 between Unix and MS-Windows hosts.
26247 @anchor{set auto-load scripts-directory}
26248 @kindex set auto-load scripts-directory
26249 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26250 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26251 may be delimited by the host platform path separator in use
26252 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26254 Each entry here needs to be covered also by the security setting
26255 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26257 @anchor{with-auto-load-dir}
26258 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26259 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26260 configuration option @option{--with-auto-load-dir}.
26262 Any reference to @file{$debugdir} will get replaced by
26263 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26264 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26265 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26266 @file{$datadir} must be placed as a directory component --- either alone or
26267 delimited by @file{/} or @file{\} directory separators, depending on the host
26270 The list of directories uses path separator (@samp{:} on GNU and Unix
26271 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26272 to the @env{PATH} environment variable.
26274 @anchor{show auto-load scripts-directory}
26275 @kindex show auto-load scripts-directory
26276 @item show auto-load scripts-directory
26277 Show @value{GDBN} auto-loaded scripts location.
26279 @anchor{add-auto-load-scripts-directory}
26280 @kindex add-auto-load-scripts-directory
26281 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
26282 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
26283 Multiple entries may be delimited by the host platform path separator in use.
26286 @value{GDBN} does not track which files it has already auto-loaded this way.
26287 @value{GDBN} will load the associated script every time the corresponding
26288 @var{objfile} is opened.
26289 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
26290 is evaluated more than once.
26292 @node dotdebug_gdb_scripts section
26293 @subsection The @code{.debug_gdb_scripts} section
26294 @cindex @code{.debug_gdb_scripts} section
26296 For systems using file formats like ELF and COFF,
26297 when @value{GDBN} loads a new object file
26298 it will look for a special section named @code{.debug_gdb_scripts}.
26299 If this section exists, its contents is a list of null-terminated entries
26300 specifying scripts to load. Each entry begins with a non-null prefix byte that
26301 specifies the kind of entry, typically the extension language and whether the
26302 script is in a file or inlined in @code{.debug_gdb_scripts}.
26304 The following entries are supported:
26307 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
26308 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
26309 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
26310 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
26313 @subsubsection Script File Entries
26315 If the entry specifies a file, @value{GDBN} will look for the file first
26316 in the current directory and then along the source search path
26317 (@pxref{Source Path, ,Specifying Source Directories}),
26318 except that @file{$cdir} is not searched, since the compilation
26319 directory is not relevant to scripts.
26321 File entries can be placed in section @code{.debug_gdb_scripts} with,
26322 for example, this GCC macro for Python scripts.
26325 /* Note: The "MS" section flags are to remove duplicates. */
26326 #define DEFINE_GDB_PY_SCRIPT(script_name) \
26328 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26329 .byte 1 /* Python */\n\
26330 .asciz \"" script_name "\"\n\
26336 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
26337 Then one can reference the macro in a header or source file like this:
26340 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
26343 The script name may include directories if desired.
26345 Note that loading of this script file also requires accordingly configured
26346 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26348 If the macro invocation is put in a header, any application or library
26349 using this header will get a reference to the specified script,
26350 and with the use of @code{"MS"} attributes on the section, the linker
26351 will remove duplicates.
26353 @subsubsection Script Text Entries
26355 Script text entries allow to put the executable script in the entry
26356 itself instead of loading it from a file.
26357 The first line of the entry, everything after the prefix byte and up to
26358 the first newline (@code{0xa}) character, is the script name, and must not
26359 contain any kind of space character, e.g., spaces or tabs.
26360 The rest of the entry, up to the trailing null byte, is the script to
26361 execute in the specified language. The name needs to be unique among
26362 all script names, as @value{GDBN} executes each script only once based
26365 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
26369 #include "symcat.h"
26370 #include "gdb/section-scripts.h"
26372 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
26373 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
26374 ".ascii \"gdb.inlined-script\\n\"\n"
26375 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
26376 ".ascii \" def __init__ (self):\\n\"\n"
26377 ".ascii \" super (test_cmd, self).__init__ ("
26378 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
26379 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
26380 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
26381 ".ascii \"test_cmd ()\\n\"\n"
26387 Loading of inlined scripts requires a properly configured
26388 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26389 The path to specify in @code{auto-load safe-path} is the path of the file
26390 containing the @code{.debug_gdb_scripts} section.
26392 @node Which flavor to choose?
26393 @subsection Which flavor to choose?
26395 Given the multiple ways of auto-loading extensions, it might not always
26396 be clear which one to choose. This section provides some guidance.
26399 Benefits of the @file{-gdb.@var{ext}} way:
26403 Can be used with file formats that don't support multiple sections.
26406 Ease of finding scripts for public libraries.
26408 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26409 in the source search path.
26410 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26411 isn't a source directory in which to find the script.
26414 Doesn't require source code additions.
26418 Benefits of the @code{.debug_gdb_scripts} way:
26422 Works with static linking.
26424 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
26425 trigger their loading. When an application is statically linked the only
26426 objfile available is the executable, and it is cumbersome to attach all the
26427 scripts from all the input libraries to the executable's
26428 @file{-gdb.@var{ext}} script.
26431 Works with classes that are entirely inlined.
26433 Some classes can be entirely inlined, and thus there may not be an associated
26434 shared library to attach a @file{-gdb.@var{ext}} script to.
26437 Scripts needn't be copied out of the source tree.
26439 In some circumstances, apps can be built out of large collections of internal
26440 libraries, and the build infrastructure necessary to install the
26441 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
26442 cumbersome. It may be easier to specify the scripts in the
26443 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26444 top of the source tree to the source search path.
26447 @node Multiple Extension Languages
26448 @section Multiple Extension Languages
26450 The Guile and Python extension languages do not share any state,
26451 and generally do not interfere with each other.
26452 There are some things to be aware of, however.
26454 @subsection Python comes first
26456 Python was @value{GDBN}'s first extension language, and to avoid breaking
26457 existing behaviour Python comes first. This is generally solved by the
26458 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
26459 extension languages, and when it makes a call to an extension language,
26460 (say to pretty-print a value), it tries each in turn until an extension
26461 language indicates it has performed the request (e.g., has returned the
26462 pretty-printed form of a value).
26463 This extends to errors while performing such requests: If an error happens
26464 while, for example, trying to pretty-print an object then the error is
26465 reported and any following extension languages are not tried.
26468 @section Creating new spellings of existing commands
26469 @cindex aliases for commands
26471 It is often useful to define alternate spellings of existing commands.
26472 For example, if a new @value{GDBN} command defined in Python has
26473 a long name to type, it is handy to have an abbreviated version of it
26474 that involves less typing.
26476 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26477 of the @samp{step} command even though it is otherwise an ambiguous
26478 abbreviation of other commands like @samp{set} and @samp{show}.
26480 Aliases are also used to provide shortened or more common versions
26481 of multi-word commands. For example, @value{GDBN} provides the
26482 @samp{tty} alias of the @samp{set inferior-tty} command.
26484 You can define a new alias with the @samp{alias} command.
26489 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26493 @var{ALIAS} specifies the name of the new alias.
26494 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26497 @var{COMMAND} specifies the name of an existing command
26498 that is being aliased.
26500 The @samp{-a} option specifies that the new alias is an abbreviation
26501 of the command. Abbreviations are not shown in command
26502 lists displayed by the @samp{help} command.
26504 The @samp{--} option specifies the end of options,
26505 and is useful when @var{ALIAS} begins with a dash.
26507 Here is a simple example showing how to make an abbreviation
26508 of a command so that there is less to type.
26509 Suppose you were tired of typing @samp{disas}, the current
26510 shortest unambiguous abbreviation of the @samp{disassemble} command
26511 and you wanted an even shorter version named @samp{di}.
26512 The following will accomplish this.
26515 (gdb) alias -a di = disas
26518 Note that aliases are different from user-defined commands.
26519 With a user-defined command, you also need to write documentation
26520 for it with the @samp{document} command.
26521 An alias automatically picks up the documentation of the existing command.
26523 Here is an example where we make @samp{elms} an abbreviation of
26524 @samp{elements} in the @samp{set print elements} command.
26525 This is to show that you can make an abbreviation of any part
26529 (gdb) alias -a set print elms = set print elements
26530 (gdb) alias -a show print elms = show print elements
26531 (gdb) set p elms 20
26533 Limit on string chars or array elements to print is 200.
26536 Note that if you are defining an alias of a @samp{set} command,
26537 and you want to have an alias for the corresponding @samp{show}
26538 command, then you need to define the latter separately.
26540 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26541 @var{ALIAS}, just as they are normally.
26544 (gdb) alias -a set pr elms = set p ele
26547 Finally, here is an example showing the creation of a one word
26548 alias for a more complex command.
26549 This creates alias @samp{spe} of the command @samp{set print elements}.
26552 (gdb) alias spe = set print elements
26557 @chapter Command Interpreters
26558 @cindex command interpreters
26560 @value{GDBN} supports multiple command interpreters, and some command
26561 infrastructure to allow users or user interface writers to switch
26562 between interpreters or run commands in other interpreters.
26564 @value{GDBN} currently supports two command interpreters, the console
26565 interpreter (sometimes called the command-line interpreter or @sc{cli})
26566 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26567 describes both of these interfaces in great detail.
26569 By default, @value{GDBN} will start with the console interpreter.
26570 However, the user may choose to start @value{GDBN} with another
26571 interpreter by specifying the @option{-i} or @option{--interpreter}
26572 startup options. Defined interpreters include:
26576 @cindex console interpreter
26577 The traditional console or command-line interpreter. This is the most often
26578 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26579 @value{GDBN} will use this interpreter.
26582 @cindex mi interpreter
26583 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
26584 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26585 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26589 @cindex mi3 interpreter
26590 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
26593 @cindex mi2 interpreter
26594 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
26597 @cindex mi1 interpreter
26598 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
26602 @cindex invoke another interpreter
26604 @kindex interpreter-exec
26605 You may execute commands in any interpreter from the current
26606 interpreter using the appropriate command. If you are running the
26607 console interpreter, simply use the @code{interpreter-exec} command:
26610 interpreter-exec mi "-data-list-register-names"
26613 @sc{gdb/mi} has a similar command, although it is only available in versions of
26614 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26616 Note that @code{interpreter-exec} only changes the interpreter for the
26617 duration of the specified command. It does not change the interpreter
26620 @cindex start a new independent interpreter
26622 Although you may only choose a single interpreter at startup, it is
26623 possible to run an independent interpreter on a specified input/output
26624 device (usually a tty).
26626 For example, consider a debugger GUI or IDE that wants to provide a
26627 @value{GDBN} console view. It may do so by embedding a terminal
26628 emulator widget in its GUI, starting @value{GDBN} in the traditional
26629 command-line mode with stdin/stdout/stderr redirected to that
26630 terminal, and then creating an MI interpreter running on a specified
26631 input/output device. The console interpreter created by @value{GDBN}
26632 at startup handles commands the user types in the terminal widget,
26633 while the GUI controls and synchronizes state with @value{GDBN} using
26634 the separate MI interpreter.
26636 To start a new secondary @dfn{user interface} running MI, use the
26637 @code{new-ui} command:
26640 @cindex new user interface
26642 new-ui @var{interpreter} @var{tty}
26645 The @var{interpreter} parameter specifies the interpreter to run.
26646 This accepts the same values as the @code{interpreter-exec} command.
26647 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
26648 @var{tty} parameter specifies the name of the bidirectional file the
26649 interpreter uses for input/output, usually the name of a
26650 pseudoterminal slave on Unix systems. For example:
26653 (@value{GDBP}) new-ui mi /dev/pts/9
26657 runs an MI interpreter on @file{/dev/pts/9}.
26660 @chapter @value{GDBN} Text User Interface
26662 @cindex Text User Interface
26665 * TUI Overview:: TUI overview
26666 * TUI Keys:: TUI key bindings
26667 * TUI Single Key Mode:: TUI single key mode
26668 * TUI Commands:: TUI-specific commands
26669 * TUI Configuration:: TUI configuration variables
26672 The @value{GDBN} Text User Interface (TUI) is a terminal
26673 interface which uses the @code{curses} library to show the source
26674 file, the assembly output, the program registers and @value{GDBN}
26675 commands in separate text windows. The TUI mode is supported only
26676 on platforms where a suitable version of the @code{curses} library
26679 The TUI mode is enabled by default when you invoke @value{GDBN} as
26680 @samp{@value{GDBP} -tui}.
26681 You can also switch in and out of TUI mode while @value{GDBN} runs by
26682 using various TUI commands and key bindings, such as @command{tui
26683 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
26684 @ref{TUI Keys, ,TUI Key Bindings}.
26687 @section TUI Overview
26689 In TUI mode, @value{GDBN} can display several text windows:
26693 This window is the @value{GDBN} command window with the @value{GDBN}
26694 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26695 managed using readline.
26698 The source window shows the source file of the program. The current
26699 line and active breakpoints are displayed in this window.
26702 The assembly window shows the disassembly output of the program.
26705 This window shows the processor registers. Registers are highlighted
26706 when their values change.
26709 The source and assembly windows show the current program position
26710 by highlighting the current line and marking it with a @samp{>} marker.
26711 Breakpoints are indicated with two markers. The first marker
26712 indicates the breakpoint type:
26716 Breakpoint which was hit at least once.
26719 Breakpoint which was never hit.
26722 Hardware breakpoint which was hit at least once.
26725 Hardware breakpoint which was never hit.
26728 The second marker indicates whether the breakpoint is enabled or not:
26732 Breakpoint is enabled.
26735 Breakpoint is disabled.
26738 The source, assembly and register windows are updated when the current
26739 thread changes, when the frame changes, or when the program counter
26742 These windows are not all visible at the same time. The command
26743 window is always visible. The others can be arranged in several
26754 source and assembly,
26757 source and registers, or
26760 assembly and registers.
26763 A status line above the command window shows the following information:
26767 Indicates the current @value{GDBN} target.
26768 (@pxref{Targets, ,Specifying a Debugging Target}).
26771 Gives the current process or thread number.
26772 When no process is being debugged, this field is set to @code{No process}.
26775 Gives the current function name for the selected frame.
26776 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26777 When there is no symbol corresponding to the current program counter,
26778 the string @code{??} is displayed.
26781 Indicates the current line number for the selected frame.
26782 When the current line number is not known, the string @code{??} is displayed.
26785 Indicates the current program counter address.
26789 @section TUI Key Bindings
26790 @cindex TUI key bindings
26792 The TUI installs several key bindings in the readline keymaps
26793 @ifset SYSTEM_READLINE
26794 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26796 @ifclear SYSTEM_READLINE
26797 (@pxref{Command Line Editing}).
26799 The following key bindings are installed for both TUI mode and the
26800 @value{GDBN} standard mode.
26809 Enter or leave the TUI mode. When leaving the TUI mode,
26810 the curses window management stops and @value{GDBN} operates using
26811 its standard mode, writing on the terminal directly. When reentering
26812 the TUI mode, control is given back to the curses windows.
26813 The screen is then refreshed.
26817 Use a TUI layout with only one window. The layout will
26818 either be @samp{source} or @samp{assembly}. When the TUI mode
26819 is not active, it will switch to the TUI mode.
26821 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26825 Use a TUI layout with at least two windows. When the current
26826 layout already has two windows, the next layout with two windows is used.
26827 When a new layout is chosen, one window will always be common to the
26828 previous layout and the new one.
26830 Think of it as the Emacs @kbd{C-x 2} binding.
26834 Change the active window. The TUI associates several key bindings
26835 (like scrolling and arrow keys) with the active window. This command
26836 gives the focus to the next TUI window.
26838 Think of it as the Emacs @kbd{C-x o} binding.
26842 Switch in and out of the TUI SingleKey mode that binds single
26843 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26846 The following key bindings only work in the TUI mode:
26851 Scroll the active window one page up.
26855 Scroll the active window one page down.
26859 Scroll the active window one line up.
26863 Scroll the active window one line down.
26867 Scroll the active window one column left.
26871 Scroll the active window one column right.
26875 Refresh the screen.
26878 Because the arrow keys scroll the active window in the TUI mode, they
26879 are not available for their normal use by readline unless the command
26880 window has the focus. When another window is active, you must use
26881 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26882 and @kbd{C-f} to control the command window.
26884 @node TUI Single Key Mode
26885 @section TUI Single Key Mode
26886 @cindex TUI single key mode
26888 The TUI also provides a @dfn{SingleKey} mode, which binds several
26889 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26890 switch into this mode, where the following key bindings are used:
26893 @kindex c @r{(SingleKey TUI key)}
26897 @kindex d @r{(SingleKey TUI key)}
26901 @kindex f @r{(SingleKey TUI key)}
26905 @kindex n @r{(SingleKey TUI key)}
26909 @kindex o @r{(SingleKey TUI key)}
26911 nexti. The shortcut letter @samp{o} stands for ``step Over''.
26913 @kindex q @r{(SingleKey TUI key)}
26915 exit the SingleKey mode.
26917 @kindex r @r{(SingleKey TUI key)}
26921 @kindex s @r{(SingleKey TUI key)}
26925 @kindex i @r{(SingleKey TUI key)}
26927 stepi. The shortcut letter @samp{i} stands for ``step Into''.
26929 @kindex u @r{(SingleKey TUI key)}
26933 @kindex v @r{(SingleKey TUI key)}
26937 @kindex w @r{(SingleKey TUI key)}
26942 Other keys temporarily switch to the @value{GDBN} command prompt.
26943 The key that was pressed is inserted in the editing buffer so that
26944 it is possible to type most @value{GDBN} commands without interaction
26945 with the TUI SingleKey mode. Once the command is entered the TUI
26946 SingleKey mode is restored. The only way to permanently leave
26947 this mode is by typing @kbd{q} or @kbd{C-x s}.
26951 @section TUI-specific Commands
26952 @cindex TUI commands
26954 The TUI has specific commands to control the text windows.
26955 These commands are always available, even when @value{GDBN} is not in
26956 the TUI mode. When @value{GDBN} is in the standard mode, most
26957 of these commands will automatically switch to the TUI mode.
26959 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26960 terminal, or @value{GDBN} has been started with the machine interface
26961 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26962 these commands will fail with an error, because it would not be
26963 possible or desirable to enable curses window management.
26968 Activate TUI mode. The last active TUI window layout will be used if
26969 TUI mode has prevsiouly been used in the current debugging session,
26970 otherwise a default layout is used.
26973 @kindex tui disable
26974 Disable TUI mode, returning to the console interpreter.
26978 List and give the size of all displayed windows.
26980 @item layout @var{name}
26982 Changes which TUI windows are displayed. In each layout the command
26983 window is always displayed, the @var{name} parameter controls which
26984 additional windows are displayed, and can be any of the following:
26988 Display the next layout.
26991 Display the previous layout.
26994 Display the source and command windows.
26997 Display the assembly and command windows.
27000 Display the source, assembly, and command windows.
27003 When in @code{src} layout display the register, source, and command
27004 windows. When in @code{asm} or @code{split} layout display the
27005 register, assembler, and command windows.
27008 @item focus @var{name}
27010 Changes which TUI window is currently active for scrolling. The
27011 @var{name} parameter can be any of the following:
27015 Make the next window active for scrolling.
27018 Make the previous window active for scrolling.
27021 Make the source window active for scrolling.
27024 Make the assembly window active for scrolling.
27027 Make the register window active for scrolling.
27030 Make the command window active for scrolling.
27035 Refresh the screen. This is similar to typing @kbd{C-L}.
27037 @item tui reg @var{group}
27039 Changes the register group displayed in the tui register window to
27040 @var{group}. If the register window is not currently displayed this
27041 command will cause the register window to be displayed. The list of
27042 register groups, as well as their order is target specific. The
27043 following groups are available on most targets:
27046 Repeatedly selecting this group will cause the display to cycle
27047 through all of the available register groups.
27050 Repeatedly selecting this group will cause the display to cycle
27051 through all of the available register groups in the reverse order to
27055 Display the general registers.
27057 Display the floating point registers.
27059 Display the system registers.
27061 Display the vector registers.
27063 Display all registers.
27068 Update the source window and the current execution point.
27070 @item winheight @var{name} +@var{count}
27071 @itemx winheight @var{name} -@var{count}
27073 Change the height of the window @var{name} by @var{count}
27074 lines. Positive counts increase the height, while negative counts
27075 decrease it. The @var{name} parameter can be one of @code{src} (the
27076 source window), @code{cmd} (the command window), @code{asm} (the
27077 disassembly window), or @code{regs} (the register display window).
27080 @node TUI Configuration
27081 @section TUI Configuration Variables
27082 @cindex TUI configuration variables
27084 Several configuration variables control the appearance of TUI windows.
27087 @item set tui border-kind @var{kind}
27088 @kindex set tui border-kind
27089 Select the border appearance for the source, assembly and register windows.
27090 The possible values are the following:
27093 Use a space character to draw the border.
27096 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
27099 Use the Alternate Character Set to draw the border. The border is
27100 drawn using character line graphics if the terminal supports them.
27103 @item set tui border-mode @var{mode}
27104 @kindex set tui border-mode
27105 @itemx set tui active-border-mode @var{mode}
27106 @kindex set tui active-border-mode
27107 Select the display attributes for the borders of the inactive windows
27108 or the active window. The @var{mode} can be one of the following:
27111 Use normal attributes to display the border.
27117 Use reverse video mode.
27120 Use half bright mode.
27122 @item half-standout
27123 Use half bright and standout mode.
27126 Use extra bright or bold mode.
27128 @item bold-standout
27129 Use extra bright or bold and standout mode.
27132 @item set tui tab-width @var{nchars}
27133 @kindex set tui tab-width
27135 Set the width of tab stops to be @var{nchars} characters. This
27136 setting affects the display of TAB characters in the source and
27141 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27144 @cindex @sc{gnu} Emacs
27145 A special interface allows you to use @sc{gnu} Emacs to view (and
27146 edit) the source files for the program you are debugging with
27149 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27150 executable file you want to debug as an argument. This command starts
27151 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27152 created Emacs buffer.
27153 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27155 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27160 All ``terminal'' input and output goes through an Emacs buffer, called
27163 This applies both to @value{GDBN} commands and their output, and to the input
27164 and output done by the program you are debugging.
27166 This is useful because it means that you can copy the text of previous
27167 commands and input them again; you can even use parts of the output
27170 All the facilities of Emacs' Shell mode are available for interacting
27171 with your program. In particular, you can send signals the usual
27172 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27176 @value{GDBN} displays source code through Emacs.
27178 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27179 source file for that frame and puts an arrow (@samp{=>}) at the
27180 left margin of the current line. Emacs uses a separate buffer for
27181 source display, and splits the screen to show both your @value{GDBN} session
27184 Explicit @value{GDBN} @code{list} or search commands still produce output as
27185 usual, but you probably have no reason to use them from Emacs.
27188 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27189 a graphical mode, enabled by default, which provides further buffers
27190 that can control the execution and describe the state of your program.
27191 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27193 If you specify an absolute file name when prompted for the @kbd{M-x
27194 gdb} argument, then Emacs sets your current working directory to where
27195 your program resides. If you only specify the file name, then Emacs
27196 sets your current working directory to the directory associated
27197 with the previous buffer. In this case, @value{GDBN} may find your
27198 program by searching your environment's @code{PATH} variable, but on
27199 some operating systems it might not find the source. So, although the
27200 @value{GDBN} input and output session proceeds normally, the auxiliary
27201 buffer does not display the current source and line of execution.
27203 The initial working directory of @value{GDBN} is printed on the top
27204 line of the GUD buffer and this serves as a default for the commands
27205 that specify files for @value{GDBN} to operate on. @xref{Files,
27206 ,Commands to Specify Files}.
27208 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27209 need to call @value{GDBN} by a different name (for example, if you
27210 keep several configurations around, with different names) you can
27211 customize the Emacs variable @code{gud-gdb-command-name} to run the
27214 In the GUD buffer, you can use these special Emacs commands in
27215 addition to the standard Shell mode commands:
27219 Describe the features of Emacs' GUD Mode.
27222 Execute to another source line, like the @value{GDBN} @code{step} command; also
27223 update the display window to show the current file and location.
27226 Execute to next source line in this function, skipping all function
27227 calls, like the @value{GDBN} @code{next} command. Then update the display window
27228 to show the current file and location.
27231 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27232 display window accordingly.
27235 Execute until exit from the selected stack frame, like the @value{GDBN}
27236 @code{finish} command.
27239 Continue execution of your program, like the @value{GDBN} @code{continue}
27243 Go up the number of frames indicated by the numeric argument
27244 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27245 like the @value{GDBN} @code{up} command.
27248 Go down the number of frames indicated by the numeric argument, like the
27249 @value{GDBN} @code{down} command.
27252 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27253 tells @value{GDBN} to set a breakpoint on the source line point is on.
27255 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27256 separate frame which shows a backtrace when the GUD buffer is current.
27257 Move point to any frame in the stack and type @key{RET} to make it
27258 become the current frame and display the associated source in the
27259 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27260 selected frame become the current one. In graphical mode, the
27261 speedbar displays watch expressions.
27263 If you accidentally delete the source-display buffer, an easy way to get
27264 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27265 request a frame display; when you run under Emacs, this recreates
27266 the source buffer if necessary to show you the context of the current
27269 The source files displayed in Emacs are in ordinary Emacs buffers
27270 which are visiting the source files in the usual way. You can edit
27271 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27272 communicates with Emacs in terms of line numbers. If you add or
27273 delete lines from the text, the line numbers that @value{GDBN} knows cease
27274 to correspond properly with the code.
27276 A more detailed description of Emacs' interaction with @value{GDBN} is
27277 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27281 @chapter The @sc{gdb/mi} Interface
27283 @unnumberedsec Function and Purpose
27285 @cindex @sc{gdb/mi}, its purpose
27286 @sc{gdb/mi} is a line based machine oriented text interface to
27287 @value{GDBN} and is activated by specifying using the
27288 @option{--interpreter} command line option (@pxref{Mode Options}). It
27289 is specifically intended to support the development of systems which
27290 use the debugger as just one small component of a larger system.
27292 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27293 in the form of a reference manual.
27295 Note that @sc{gdb/mi} is still under construction, so some of the
27296 features described below are incomplete and subject to change
27297 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27299 @unnumberedsec Notation and Terminology
27301 @cindex notational conventions, for @sc{gdb/mi}
27302 This chapter uses the following notation:
27306 @code{|} separates two alternatives.
27309 @code{[ @var{something} ]} indicates that @var{something} is optional:
27310 it may or may not be given.
27313 @code{( @var{group} )*} means that @var{group} inside the parentheses
27314 may repeat zero or more times.
27317 @code{( @var{group} )+} means that @var{group} inside the parentheses
27318 may repeat one or more times.
27321 @code{"@var{string}"} means a literal @var{string}.
27325 @heading Dependencies
27329 * GDB/MI General Design::
27330 * GDB/MI Command Syntax::
27331 * GDB/MI Compatibility with CLI::
27332 * GDB/MI Development and Front Ends::
27333 * GDB/MI Output Records::
27334 * GDB/MI Simple Examples::
27335 * GDB/MI Command Description Format::
27336 * GDB/MI Breakpoint Commands::
27337 * GDB/MI Catchpoint Commands::
27338 * GDB/MI Program Context::
27339 * GDB/MI Thread Commands::
27340 * GDB/MI Ada Tasking Commands::
27341 * GDB/MI Program Execution::
27342 * GDB/MI Stack Manipulation::
27343 * GDB/MI Variable Objects::
27344 * GDB/MI Data Manipulation::
27345 * GDB/MI Tracepoint Commands::
27346 * GDB/MI Symbol Query::
27347 * GDB/MI File Commands::
27349 * GDB/MI Kod Commands::
27350 * GDB/MI Memory Overlay Commands::
27351 * GDB/MI Signal Handling Commands::
27353 * GDB/MI Target Manipulation::
27354 * GDB/MI File Transfer Commands::
27355 * GDB/MI Ada Exceptions Commands::
27356 * GDB/MI Support Commands::
27357 * GDB/MI Miscellaneous Commands::
27360 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27361 @node GDB/MI General Design
27362 @section @sc{gdb/mi} General Design
27363 @cindex GDB/MI General Design
27365 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27366 parts---commands sent to @value{GDBN}, responses to those commands
27367 and notifications. Each command results in exactly one response,
27368 indicating either successful completion of the command, or an error.
27369 For the commands that do not resume the target, the response contains the
27370 requested information. For the commands that resume the target, the
27371 response only indicates whether the target was successfully resumed.
27372 Notifications is the mechanism for reporting changes in the state of the
27373 target, or in @value{GDBN} state, that cannot conveniently be associated with
27374 a command and reported as part of that command response.
27376 The important examples of notifications are:
27380 Exec notifications. These are used to report changes in
27381 target state---when a target is resumed, or stopped. It would not
27382 be feasible to include this information in response of resuming
27383 commands, because one resume commands can result in multiple events in
27384 different threads. Also, quite some time may pass before any event
27385 happens in the target, while a frontend needs to know whether the resuming
27386 command itself was successfully executed.
27389 Console output, and status notifications. Console output
27390 notifications are used to report output of CLI commands, as well as
27391 diagnostics for other commands. Status notifications are used to
27392 report the progress of a long-running operation. Naturally, including
27393 this information in command response would mean no output is produced
27394 until the command is finished, which is undesirable.
27397 General notifications. Commands may have various side effects on
27398 the @value{GDBN} or target state beyond their official purpose. For example,
27399 a command may change the selected thread. Although such changes can
27400 be included in command response, using notification allows for more
27401 orthogonal frontend design.
27405 There's no guarantee that whenever an MI command reports an error,
27406 @value{GDBN} or the target are in any specific state, and especially,
27407 the state is not reverted to the state before the MI command was
27408 processed. Therefore, whenever an MI command results in an error,
27409 we recommend that the frontend refreshes all the information shown in
27410 the user interface.
27414 * Context management::
27415 * Asynchronous and non-stop modes::
27419 @node Context management
27420 @subsection Context management
27422 @subsubsection Threads and Frames
27424 In most cases when @value{GDBN} accesses the target, this access is
27425 done in context of a specific thread and frame (@pxref{Frames}).
27426 Often, even when accessing global data, the target requires that a thread
27427 be specified. The CLI interface maintains the selected thread and frame,
27428 and supplies them to target on each command. This is convenient,
27429 because a command line user would not want to specify that information
27430 explicitly on each command, and because user interacts with
27431 @value{GDBN} via a single terminal, so no confusion is possible as
27432 to what thread and frame are the current ones.
27434 In the case of MI, the concept of selected thread and frame is less
27435 useful. First, a frontend can easily remember this information
27436 itself. Second, a graphical frontend can have more than one window,
27437 each one used for debugging a different thread, and the frontend might
27438 want to access additional threads for internal purposes. This
27439 increases the risk that by relying on implicitly selected thread, the
27440 frontend may be operating on a wrong one. Therefore, each MI command
27441 should explicitly specify which thread and frame to operate on. To
27442 make it possible, each MI command accepts the @samp{--thread} and
27443 @samp{--frame} options, the value to each is @value{GDBN} global
27444 identifier for thread and frame to operate on.
27446 Usually, each top-level window in a frontend allows the user to select
27447 a thread and a frame, and remembers the user selection for further
27448 operations. However, in some cases @value{GDBN} may suggest that the
27449 current thread or frame be changed. For example, when stopping on a
27450 breakpoint it is reasonable to switch to the thread where breakpoint is
27451 hit. For another example, if the user issues the CLI @samp{thread} or
27452 @samp{frame} commands via the frontend, it is desirable to change the
27453 frontend's selection to the one specified by user. @value{GDBN}
27454 communicates the suggestion to change current thread and frame using the
27455 @samp{=thread-selected} notification.
27457 Note that historically, MI shares the selected thread with CLI, so
27458 frontends used the @code{-thread-select} to execute commands in the
27459 right context. However, getting this to work right is cumbersome. The
27460 simplest way is for frontend to emit @code{-thread-select} command
27461 before every command. This doubles the number of commands that need
27462 to be sent. The alternative approach is to suppress @code{-thread-select}
27463 if the selected thread in @value{GDBN} is supposed to be identical to the
27464 thread the frontend wants to operate on. However, getting this
27465 optimization right can be tricky. In particular, if the frontend
27466 sends several commands to @value{GDBN}, and one of the commands changes the
27467 selected thread, then the behaviour of subsequent commands will
27468 change. So, a frontend should either wait for response from such
27469 problematic commands, or explicitly add @code{-thread-select} for
27470 all subsequent commands. No frontend is known to do this exactly
27471 right, so it is suggested to just always pass the @samp{--thread} and
27472 @samp{--frame} options.
27474 @subsubsection Language
27476 The execution of several commands depends on which language is selected.
27477 By default, the current language (@pxref{show language}) is used.
27478 But for commands known to be language-sensitive, it is recommended
27479 to use the @samp{--language} option. This option takes one argument,
27480 which is the name of the language to use while executing the command.
27484 -data-evaluate-expression --language c "sizeof (void*)"
27489 The valid language names are the same names accepted by the
27490 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
27491 @samp{local} or @samp{unknown}.
27493 @node Asynchronous and non-stop modes
27494 @subsection Asynchronous command execution and non-stop mode
27496 On some targets, @value{GDBN} is capable of processing MI commands
27497 even while the target is running. This is called @dfn{asynchronous
27498 command execution} (@pxref{Background Execution}). The frontend may
27499 specify a preferrence for asynchronous execution using the
27500 @code{-gdb-set mi-async 1} command, which should be emitted before
27501 either running the executable or attaching to the target. After the
27502 frontend has started the executable or attached to the target, it can
27503 find if asynchronous execution is enabled using the
27504 @code{-list-target-features} command.
27507 @item -gdb-set mi-async on
27508 @item -gdb-set mi-async off
27509 Set whether MI is in asynchronous mode.
27511 When @code{off}, which is the default, MI execution commands (e.g.,
27512 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
27513 for the program to stop before processing further commands.
27515 When @code{on}, MI execution commands are background execution
27516 commands (e.g., @code{-exec-continue} becomes the equivalent of the
27517 @code{c&} CLI command), and so @value{GDBN} is capable of processing
27518 MI commands even while the target is running.
27520 @item -gdb-show mi-async
27521 Show whether MI asynchronous mode is enabled.
27524 Note: In @value{GDBN} version 7.7 and earlier, this option was called
27525 @code{target-async} instead of @code{mi-async}, and it had the effect
27526 of both putting MI in asynchronous mode and making CLI background
27527 commands possible. CLI background commands are now always possible
27528 ``out of the box'' if the target supports them. The old spelling is
27529 kept as a deprecated alias for backwards compatibility.
27531 Even if @value{GDBN} can accept a command while target is running,
27532 many commands that access the target do not work when the target is
27533 running. Therefore, asynchronous command execution is most useful
27534 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27535 it is possible to examine the state of one thread, while other threads
27538 When a given thread is running, MI commands that try to access the
27539 target in the context of that thread may not work, or may work only on
27540 some targets. In particular, commands that try to operate on thread's
27541 stack will not work, on any target. Commands that read memory, or
27542 modify breakpoints, may work or not work, depending on the target. Note
27543 that even commands that operate on global state, such as @code{print},
27544 @code{set}, and breakpoint commands, still access the target in the
27545 context of a specific thread, so frontend should try to find a
27546 stopped thread and perform the operation on that thread (using the
27547 @samp{--thread} option).
27549 Which commands will work in the context of a running thread is
27550 highly target dependent. However, the two commands
27551 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27552 to find the state of a thread, will always work.
27554 @node Thread groups
27555 @subsection Thread groups
27556 @value{GDBN} may be used to debug several processes at the same time.
27557 On some platfroms, @value{GDBN} may support debugging of several
27558 hardware systems, each one having several cores with several different
27559 processes running on each core. This section describes the MI
27560 mechanism to support such debugging scenarios.
27562 The key observation is that regardless of the structure of the
27563 target, MI can have a global list of threads, because most commands that
27564 accept the @samp{--thread} option do not need to know what process that
27565 thread belongs to. Therefore, it is not necessary to introduce
27566 neither additional @samp{--process} option, nor an notion of the
27567 current process in the MI interface. The only strictly new feature
27568 that is required is the ability to find how the threads are grouped
27571 To allow the user to discover such grouping, and to support arbitrary
27572 hierarchy of machines/cores/processes, MI introduces the concept of a
27573 @dfn{thread group}. Thread group is a collection of threads and other
27574 thread groups. A thread group always has a string identifier, a type,
27575 and may have additional attributes specific to the type. A new
27576 command, @code{-list-thread-groups}, returns the list of top-level
27577 thread groups, which correspond to processes that @value{GDBN} is
27578 debugging at the moment. By passing an identifier of a thread group
27579 to the @code{-list-thread-groups} command, it is possible to obtain
27580 the members of specific thread group.
27582 To allow the user to easily discover processes, and other objects, he
27583 wishes to debug, a concept of @dfn{available thread group} is
27584 introduced. Available thread group is an thread group that
27585 @value{GDBN} is not debugging, but that can be attached to, using the
27586 @code{-target-attach} command. The list of available top-level thread
27587 groups can be obtained using @samp{-list-thread-groups --available}.
27588 In general, the content of a thread group may be only retrieved only
27589 after attaching to that thread group.
27591 Thread groups are related to inferiors (@pxref{Inferiors and
27592 Programs}). Each inferior corresponds to a thread group of a special
27593 type @samp{process}, and some additional operations are permitted on
27594 such thread groups.
27596 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27597 @node GDB/MI Command Syntax
27598 @section @sc{gdb/mi} Command Syntax
27601 * GDB/MI Input Syntax::
27602 * GDB/MI Output Syntax::
27605 @node GDB/MI Input Syntax
27606 @subsection @sc{gdb/mi} Input Syntax
27608 @cindex input syntax for @sc{gdb/mi}
27609 @cindex @sc{gdb/mi}, input syntax
27611 @item @var{command} @expansion{}
27612 @code{@var{cli-command} | @var{mi-command}}
27614 @item @var{cli-command} @expansion{}
27615 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27616 @var{cli-command} is any existing @value{GDBN} CLI command.
27618 @item @var{mi-command} @expansion{}
27619 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27620 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27622 @item @var{token} @expansion{}
27623 "any sequence of digits"
27625 @item @var{option} @expansion{}
27626 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27628 @item @var{parameter} @expansion{}
27629 @code{@var{non-blank-sequence} | @var{c-string}}
27631 @item @var{operation} @expansion{}
27632 @emph{any of the operations described in this chapter}
27634 @item @var{non-blank-sequence} @expansion{}
27635 @emph{anything, provided it doesn't contain special characters such as
27636 "-", @var{nl}, """ and of course " "}
27638 @item @var{c-string} @expansion{}
27639 @code{""" @var{seven-bit-iso-c-string-content} """}
27641 @item @var{nl} @expansion{}
27650 The CLI commands are still handled by the @sc{mi} interpreter; their
27651 output is described below.
27654 The @code{@var{token}}, when present, is passed back when the command
27658 Some @sc{mi} commands accept optional arguments as part of the parameter
27659 list. Each option is identified by a leading @samp{-} (dash) and may be
27660 followed by an optional argument parameter. Options occur first in the
27661 parameter list and can be delimited from normal parameters using
27662 @samp{--} (this is useful when some parameters begin with a dash).
27669 We want easy access to the existing CLI syntax (for debugging).
27672 We want it to be easy to spot a @sc{mi} operation.
27675 @node GDB/MI Output Syntax
27676 @subsection @sc{gdb/mi} Output Syntax
27678 @cindex output syntax of @sc{gdb/mi}
27679 @cindex @sc{gdb/mi}, output syntax
27680 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27681 followed, optionally, by a single result record. This result record
27682 is for the most recent command. The sequence of output records is
27683 terminated by @samp{(gdb)}.
27685 If an input command was prefixed with a @code{@var{token}} then the
27686 corresponding output for that command will also be prefixed by that same
27690 @item @var{output} @expansion{}
27691 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27693 @item @var{result-record} @expansion{}
27694 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27696 @item @var{out-of-band-record} @expansion{}
27697 @code{@var{async-record} | @var{stream-record}}
27699 @item @var{async-record} @expansion{}
27700 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27702 @item @var{exec-async-output} @expansion{}
27703 @code{[ @var{token} ] "*" @var{async-output nl}}
27705 @item @var{status-async-output} @expansion{}
27706 @code{[ @var{token} ] "+" @var{async-output nl}}
27708 @item @var{notify-async-output} @expansion{}
27709 @code{[ @var{token} ] "=" @var{async-output nl}}
27711 @item @var{async-output} @expansion{}
27712 @code{@var{async-class} ( "," @var{result} )*}
27714 @item @var{result-class} @expansion{}
27715 @code{"done" | "running" | "connected" | "error" | "exit"}
27717 @item @var{async-class} @expansion{}
27718 @code{"stopped" | @var{others}} (where @var{others} will be added
27719 depending on the needs---this is still in development).
27721 @item @var{result} @expansion{}
27722 @code{ @var{variable} "=" @var{value}}
27724 @item @var{variable} @expansion{}
27725 @code{ @var{string} }
27727 @item @var{value} @expansion{}
27728 @code{ @var{const} | @var{tuple} | @var{list} }
27730 @item @var{const} @expansion{}
27731 @code{@var{c-string}}
27733 @item @var{tuple} @expansion{}
27734 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27736 @item @var{list} @expansion{}
27737 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27738 @var{result} ( "," @var{result} )* "]" }
27740 @item @var{stream-record} @expansion{}
27741 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27743 @item @var{console-stream-output} @expansion{}
27744 @code{"~" @var{c-string nl}}
27746 @item @var{target-stream-output} @expansion{}
27747 @code{"@@" @var{c-string nl}}
27749 @item @var{log-stream-output} @expansion{}
27750 @code{"&" @var{c-string nl}}
27752 @item @var{nl} @expansion{}
27755 @item @var{token} @expansion{}
27756 @emph{any sequence of digits}.
27764 All output sequences end in a single line containing a period.
27767 The @code{@var{token}} is from the corresponding request. Note that
27768 for all async output, while the token is allowed by the grammar and
27769 may be output by future versions of @value{GDBN} for select async
27770 output messages, it is generally omitted. Frontends should treat
27771 all async output as reporting general changes in the state of the
27772 target and there should be no need to associate async output to any
27776 @cindex status output in @sc{gdb/mi}
27777 @var{status-async-output} contains on-going status information about the
27778 progress of a slow operation. It can be discarded. All status output is
27779 prefixed by @samp{+}.
27782 @cindex async output in @sc{gdb/mi}
27783 @var{exec-async-output} contains asynchronous state change on the target
27784 (stopped, started, disappeared). All async output is prefixed by
27788 @cindex notify output in @sc{gdb/mi}
27789 @var{notify-async-output} contains supplementary information that the
27790 client should handle (e.g., a new breakpoint information). All notify
27791 output is prefixed by @samp{=}.
27794 @cindex console output in @sc{gdb/mi}
27795 @var{console-stream-output} is output that should be displayed as is in the
27796 console. It is the textual response to a CLI command. All the console
27797 output is prefixed by @samp{~}.
27800 @cindex target output in @sc{gdb/mi}
27801 @var{target-stream-output} is the output produced by the target program.
27802 All the target output is prefixed by @samp{@@}.
27805 @cindex log output in @sc{gdb/mi}
27806 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27807 instance messages that should be displayed as part of an error log. All
27808 the log output is prefixed by @samp{&}.
27811 @cindex list output in @sc{gdb/mi}
27812 New @sc{gdb/mi} commands should only output @var{lists} containing
27818 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27819 details about the various output records.
27821 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27822 @node GDB/MI Compatibility with CLI
27823 @section @sc{gdb/mi} Compatibility with CLI
27825 @cindex compatibility, @sc{gdb/mi} and CLI
27826 @cindex @sc{gdb/mi}, compatibility with CLI
27828 For the developers convenience CLI commands can be entered directly,
27829 but there may be some unexpected behaviour. For example, commands
27830 that query the user will behave as if the user replied yes, breakpoint
27831 command lists are not executed and some CLI commands, such as
27832 @code{if}, @code{when} and @code{define}, prompt for further input with
27833 @samp{>}, which is not valid MI output.
27835 This feature may be removed at some stage in the future and it is
27836 recommended that front ends use the @code{-interpreter-exec} command
27837 (@pxref{-interpreter-exec}).
27839 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27840 @node GDB/MI Development and Front Ends
27841 @section @sc{gdb/mi} Development and Front Ends
27842 @cindex @sc{gdb/mi} development
27844 The application which takes the MI output and presents the state of the
27845 program being debugged to the user is called a @dfn{front end}.
27847 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
27848 to the MI interface may break existing usage. This section describes how the
27849 protocol changes and how to request previous version of the protocol when it
27852 Some changes in MI need not break a carefully designed front end, and
27853 for these the MI version will remain unchanged. The following is a
27854 list of changes that may occur within one level, so front ends should
27855 parse MI output in a way that can handle them:
27859 New MI commands may be added.
27862 New fields may be added to the output of any MI command.
27865 The range of values for fields with specified values, e.g.,
27866 @code{in_scope} (@pxref{-var-update}) may be extended.
27868 @c The format of field's content e.g type prefix, may change so parse it
27869 @c at your own risk. Yes, in general?
27871 @c The order of fields may change? Shouldn't really matter but it might
27872 @c resolve inconsistencies.
27875 If the changes are likely to break front ends, the MI version level
27876 will be increased by one. The new versions of the MI protocol are not compatible
27877 with the old versions. Old versions of MI remain available, allowing front ends
27878 to keep using them until they are modified to use the latest MI version.
27880 Since @code{--interpreter=mi} always points to the latest MI version, it is
27881 recommended that front ends request a specific version of MI when launching
27882 @value{GDBN} (e.g. @code{--interpreter=mi2}) to make sure they get an
27883 interpreter with the MI version they expect.
27885 The following table gives a summary of the the released versions of the MI
27886 interface: the version number, the version of GDB in which it first appeared
27887 and the breaking changes compared to the previous version.
27889 @multitable @columnfractions .05 .05 .9
27890 @headitem MI version @tab GDB version @tab Breaking changes
27907 The @code{-environment-pwd}, @code{-environment-directory} and
27908 @code{-environment-path} commands now returns values using the MI output
27909 syntax, rather than CLI output syntax.
27912 @code{-var-list-children}'s @code{children} result field is now a list, rather
27916 @code{-var-update}'s @code{changelist} result field is now a list, rather than
27928 The output of information about multi-location breakpoints has changed in the
27929 responses to the @code{-break-insert} and @code{-break-info} commands, as well
27930 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
27931 The multiple locations are now placed in a @code{locations} field, whose value
27937 If your front end cannot yet migrate to a more recent version of the
27938 MI protocol, you can nevertheless selectively enable specific features
27939 available in those recent MI versions, using the following commands:
27943 @item -fix-multi-location-breakpoint-output
27944 Use the output for multi-location breakpoints which was introduced by
27945 MI 3, even when using MI versions 2 or 1. This command has no
27946 effect when using MI version 3 or later.
27950 The best way to avoid unexpected changes in MI that might break your front
27951 end is to make your project known to @value{GDBN} developers and
27952 follow development on @email{gdb@@sourceware.org} and
27953 @email{gdb-patches@@sourceware.org}.
27954 @cindex mailing lists
27956 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27957 @node GDB/MI Output Records
27958 @section @sc{gdb/mi} Output Records
27961 * GDB/MI Result Records::
27962 * GDB/MI Stream Records::
27963 * GDB/MI Async Records::
27964 * GDB/MI Breakpoint Information::
27965 * GDB/MI Frame Information::
27966 * GDB/MI Thread Information::
27967 * GDB/MI Ada Exception Information::
27970 @node GDB/MI Result Records
27971 @subsection @sc{gdb/mi} Result Records
27973 @cindex result records in @sc{gdb/mi}
27974 @cindex @sc{gdb/mi}, result records
27975 In addition to a number of out-of-band notifications, the response to a
27976 @sc{gdb/mi} command includes one of the following result indications:
27980 @item "^done" [ "," @var{results} ]
27981 The synchronous operation was successful, @code{@var{results}} are the return
27986 This result record is equivalent to @samp{^done}. Historically, it
27987 was output instead of @samp{^done} if the command has resumed the
27988 target. This behaviour is maintained for backward compatibility, but
27989 all frontends should treat @samp{^done} and @samp{^running}
27990 identically and rely on the @samp{*running} output record to determine
27991 which threads are resumed.
27995 @value{GDBN} has connected to a remote target.
27997 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
27999 The operation failed. The @code{msg=@var{c-string}} variable contains
28000 the corresponding error message.
28002 If present, the @code{code=@var{c-string}} variable provides an error
28003 code on which consumers can rely on to detect the corresponding
28004 error condition. At present, only one error code is defined:
28007 @item "undefined-command"
28008 Indicates that the command causing the error does not exist.
28013 @value{GDBN} has terminated.
28017 @node GDB/MI Stream Records
28018 @subsection @sc{gdb/mi} Stream Records
28020 @cindex @sc{gdb/mi}, stream records
28021 @cindex stream records in @sc{gdb/mi}
28022 @value{GDBN} internally maintains a number of output streams: the console, the
28023 target, and the log. The output intended for each of these streams is
28024 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
28026 Each stream record begins with a unique @dfn{prefix character} which
28027 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
28028 Syntax}). In addition to the prefix, each stream record contains a
28029 @code{@var{string-output}}. This is either raw text (with an implicit new
28030 line) or a quoted C string (which does not contain an implicit newline).
28033 @item "~" @var{string-output}
28034 The console output stream contains text that should be displayed in the
28035 CLI console window. It contains the textual responses to CLI commands.
28037 @item "@@" @var{string-output}
28038 The target output stream contains any textual output from the running
28039 target. This is only present when GDB's event loop is truly
28040 asynchronous, which is currently only the case for remote targets.
28042 @item "&" @var{string-output}
28043 The log stream contains debugging messages being produced by @value{GDBN}'s
28047 @node GDB/MI Async Records
28048 @subsection @sc{gdb/mi} Async Records
28050 @cindex async records in @sc{gdb/mi}
28051 @cindex @sc{gdb/mi}, async records
28052 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
28053 additional changes that have occurred. Those changes can either be a
28054 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
28055 target activity (e.g., target stopped).
28057 The following is the list of possible async records:
28061 @item *running,thread-id="@var{thread}"
28062 The target is now running. The @var{thread} field can be the global
28063 thread ID of the the thread that is now running, and it can be
28064 @samp{all} if all threads are running. The frontend should assume
28065 that no interaction with a running thread is possible after this
28066 notification is produced. The frontend should not assume that this
28067 notification is output only once for any command. @value{GDBN} may
28068 emit this notification several times, either for different threads,
28069 because it cannot resume all threads together, or even for a single
28070 thread, if the thread must be stepped though some code before letting
28073 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
28074 The target has stopped. The @var{reason} field can have one of the
28078 @item breakpoint-hit
28079 A breakpoint was reached.
28080 @item watchpoint-trigger
28081 A watchpoint was triggered.
28082 @item read-watchpoint-trigger
28083 A read watchpoint was triggered.
28084 @item access-watchpoint-trigger
28085 An access watchpoint was triggered.
28086 @item function-finished
28087 An -exec-finish or similar CLI command was accomplished.
28088 @item location-reached
28089 An -exec-until or similar CLI command was accomplished.
28090 @item watchpoint-scope
28091 A watchpoint has gone out of scope.
28092 @item end-stepping-range
28093 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
28094 similar CLI command was accomplished.
28095 @item exited-signalled
28096 The inferior exited because of a signal.
28098 The inferior exited.
28099 @item exited-normally
28100 The inferior exited normally.
28101 @item signal-received
28102 A signal was received by the inferior.
28104 The inferior has stopped due to a library being loaded or unloaded.
28105 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
28106 set or when a @code{catch load} or @code{catch unload} catchpoint is
28107 in use (@pxref{Set Catchpoints}).
28109 The inferior has forked. This is reported when @code{catch fork}
28110 (@pxref{Set Catchpoints}) has been used.
28112 The inferior has vforked. This is reported in when @code{catch vfork}
28113 (@pxref{Set Catchpoints}) has been used.
28114 @item syscall-entry
28115 The inferior entered a system call. This is reported when @code{catch
28116 syscall} (@pxref{Set Catchpoints}) has been used.
28117 @item syscall-return
28118 The inferior returned from a system call. This is reported when
28119 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
28121 The inferior called @code{exec}. This is reported when @code{catch exec}
28122 (@pxref{Set Catchpoints}) has been used.
28125 The @var{id} field identifies the global thread ID of the thread
28126 that directly caused the stop -- for example by hitting a breakpoint.
28127 Depending on whether all-stop
28128 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
28129 stop all threads, or only the thread that directly triggered the stop.
28130 If all threads are stopped, the @var{stopped} field will have the
28131 value of @code{"all"}. Otherwise, the value of the @var{stopped}
28132 field will be a list of thread identifiers. Presently, this list will
28133 always include a single thread, but frontend should be prepared to see
28134 several threads in the list. The @var{core} field reports the
28135 processor core on which the stop event has happened. This field may be absent
28136 if such information is not available.
28138 @item =thread-group-added,id="@var{id}"
28139 @itemx =thread-group-removed,id="@var{id}"
28140 A thread group was either added or removed. The @var{id} field
28141 contains the @value{GDBN} identifier of the thread group. When a thread
28142 group is added, it generally might not be associated with a running
28143 process. When a thread group is removed, its id becomes invalid and
28144 cannot be used in any way.
28146 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
28147 A thread group became associated with a running program,
28148 either because the program was just started or the thread group
28149 was attached to a program. The @var{id} field contains the
28150 @value{GDBN} identifier of the thread group. The @var{pid} field
28151 contains process identifier, specific to the operating system.
28153 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
28154 A thread group is no longer associated with a running program,
28155 either because the program has exited, or because it was detached
28156 from. The @var{id} field contains the @value{GDBN} identifier of the
28157 thread group. The @var{code} field is the exit code of the inferior; it exists
28158 only when the inferior exited with some code.
28160 @item =thread-created,id="@var{id}",group-id="@var{gid}"
28161 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
28162 A thread either was created, or has exited. The @var{id} field
28163 contains the global @value{GDBN} identifier of the thread. The @var{gid}
28164 field identifies the thread group this thread belongs to.
28166 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
28167 Informs that the selected thread or frame were changed. This notification
28168 is not emitted as result of the @code{-thread-select} or
28169 @code{-stack-select-frame} commands, but is emitted whenever an MI command
28170 that is not documented to change the selected thread and frame actually
28171 changes them. In particular, invoking, directly or indirectly
28172 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
28173 will generate this notification. Changing the thread or frame from another
28174 user interface (see @ref{Interpreters}) will also generate this notification.
28176 The @var{frame} field is only present if the newly selected thread is
28177 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
28179 We suggest that in response to this notification, front ends
28180 highlight the selected thread and cause subsequent commands to apply to
28183 @item =library-loaded,...
28184 Reports that a new library file was loaded by the program. This
28185 notification has 5 fields---@var{id}, @var{target-name},
28186 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
28187 opaque identifier of the library. For remote debugging case,
28188 @var{target-name} and @var{host-name} fields give the name of the
28189 library file on the target, and on the host respectively. For native
28190 debugging, both those fields have the same value. The
28191 @var{symbols-loaded} field is emitted only for backward compatibility
28192 and should not be relied on to convey any useful information. The
28193 @var{thread-group} field, if present, specifies the id of the thread
28194 group in whose context the library was loaded. If the field is
28195 absent, it means the library was loaded in the context of all present
28196 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
28199 @item =library-unloaded,...
28200 Reports that a library was unloaded by the program. This notification
28201 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
28202 the same meaning as for the @code{=library-loaded} notification.
28203 The @var{thread-group} field, if present, specifies the id of the
28204 thread group in whose context the library was unloaded. If the field is
28205 absent, it means the library was unloaded in the context of all present
28208 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
28209 @itemx =traceframe-changed,end
28210 Reports that the trace frame was changed and its new number is
28211 @var{tfnum}. The number of the tracepoint associated with this trace
28212 frame is @var{tpnum}.
28214 @item =tsv-created,name=@var{name},initial=@var{initial}
28215 Reports that the new trace state variable @var{name} is created with
28216 initial value @var{initial}.
28218 @item =tsv-deleted,name=@var{name}
28219 @itemx =tsv-deleted
28220 Reports that the trace state variable @var{name} is deleted or all
28221 trace state variables are deleted.
28223 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28224 Reports that the trace state variable @var{name} is modified with
28225 the initial value @var{initial}. The current value @var{current} of
28226 trace state variable is optional and is reported if the current
28227 value of trace state variable is known.
28229 @item =breakpoint-created,bkpt=@{...@}
28230 @itemx =breakpoint-modified,bkpt=@{...@}
28231 @itemx =breakpoint-deleted,id=@var{number}
28232 Reports that a breakpoint was created, modified, or deleted,
28233 respectively. Only user-visible breakpoints are reported to the MI
28236 The @var{bkpt} argument is of the same form as returned by the various
28237 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28238 @var{number} is the ordinal number of the breakpoint.
28240 Note that if a breakpoint is emitted in the result record of a
28241 command, then it will not also be emitted in an async record.
28243 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
28244 @itemx =record-stopped,thread-group="@var{id}"
28245 Execution log recording was either started or stopped on an
28246 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28247 group corresponding to the affected inferior.
28249 The @var{method} field indicates the method used to record execution. If the
28250 method in use supports multiple recording formats, @var{format} will be present
28251 and contain the currently used format. @xref{Process Record and Replay},
28252 for existing method and format values.
28254 @item =cmd-param-changed,param=@var{param},value=@var{value}
28255 Reports that a parameter of the command @code{set @var{param}} is
28256 changed to @var{value}. In the multi-word @code{set} command,
28257 the @var{param} is the whole parameter list to @code{set} command.
28258 For example, In command @code{set check type on}, @var{param}
28259 is @code{check type} and @var{value} is @code{on}.
28261 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28262 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28263 written in an inferior. The @var{id} is the identifier of the
28264 thread group corresponding to the affected inferior. The optional
28265 @code{type="code"} part is reported if the memory written to holds
28269 @node GDB/MI Breakpoint Information
28270 @subsection @sc{gdb/mi} Breakpoint Information
28272 When @value{GDBN} reports information about a breakpoint, a
28273 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28278 The breakpoint number.
28281 The type of the breakpoint. For ordinary breakpoints this will be
28282 @samp{breakpoint}, but many values are possible.
28285 If the type of the breakpoint is @samp{catchpoint}, then this
28286 indicates the exact type of catchpoint.
28289 This is the breakpoint disposition---either @samp{del}, meaning that
28290 the breakpoint will be deleted at the next stop, or @samp{keep},
28291 meaning that the breakpoint will not be deleted.
28294 This indicates whether the breakpoint is enabled, in which case the
28295 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28296 Note that this is not the same as the field @code{enable}.
28299 The address of the breakpoint. This may be a hexidecimal number,
28300 giving the address; or the string @samp{<PENDING>}, for a pending
28301 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28302 multiple locations. This field will not be present if no address can
28303 be determined. For example, a watchpoint does not have an address.
28306 If known, the function in which the breakpoint appears.
28307 If not known, this field is not present.
28310 The name of the source file which contains this function, if known.
28311 If not known, this field is not present.
28314 The full file name of the source file which contains this function, if
28315 known. If not known, this field is not present.
28318 The line number at which this breakpoint appears, if known.
28319 If not known, this field is not present.
28322 If the source file is not known, this field may be provided. If
28323 provided, this holds the address of the breakpoint, possibly followed
28327 If this breakpoint is pending, this field is present and holds the
28328 text used to set the breakpoint, as entered by the user.
28331 Where this breakpoint's condition is evaluated, either @samp{host} or
28335 If this is a thread-specific breakpoint, then this identifies the
28336 thread in which the breakpoint can trigger.
28339 If this breakpoint is restricted to a particular Ada task, then this
28340 field will hold the task identifier.
28343 If the breakpoint is conditional, this is the condition expression.
28346 The ignore count of the breakpoint.
28349 The enable count of the breakpoint.
28351 @item traceframe-usage
28354 @item static-tracepoint-marker-string-id
28355 For a static tracepoint, the name of the static tracepoint marker.
28358 For a masked watchpoint, this is the mask.
28361 A tracepoint's pass count.
28363 @item original-location
28364 The location of the breakpoint as originally specified by the user.
28365 This field is optional.
28368 The number of times the breakpoint has been hit.
28371 This field is only given for tracepoints. This is either @samp{y},
28372 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28376 Some extra data, the exact contents of which are type-dependent.
28379 This field is present if the breakpoint has multiple locations. It is also
28380 exceptionally present if the breakpoint is enabled and has a single, disabled
28383 The value is a list of locations. The format of a location is decribed below.
28387 A location in a multi-location breakpoint is represented as a tuple with the
28393 The location number as a dotted pair, like @samp{1.2}. The first digit is the
28394 number of the parent breakpoint. The second digit is the number of the
28395 location within that breakpoint.
28398 This indicates whether the location is enabled, in which case the
28399 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28400 Note that this is not the same as the field @code{enable}.
28403 The address of this location as an hexidecimal number.
28406 If known, the function in which the location appears.
28407 If not known, this field is not present.
28410 The name of the source file which contains this location, if known.
28411 If not known, this field is not present.
28414 The full file name of the source file which contains this location, if
28415 known. If not known, this field is not present.
28418 The line number at which this location appears, if known.
28419 If not known, this field is not present.
28421 @item thread-groups
28422 The thread groups this location is in.
28426 For example, here is what the output of @code{-break-insert}
28427 (@pxref{GDB/MI Breakpoint Commands}) might be:
28430 -> -break-insert main
28431 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28432 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28433 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28438 @node GDB/MI Frame Information
28439 @subsection @sc{gdb/mi} Frame Information
28441 Response from many MI commands includes an information about stack
28442 frame. This information is a tuple that may have the following
28447 The level of the stack frame. The innermost frame has the level of
28448 zero. This field is always present.
28451 The name of the function corresponding to the frame. This field may
28452 be absent if @value{GDBN} is unable to determine the function name.
28455 The code address for the frame. This field is always present.
28458 The name of the source files that correspond to the frame's code
28459 address. This field may be absent.
28462 The source line corresponding to the frames' code address. This field
28466 The name of the binary file (either executable or shared library) the
28467 corresponds to the frame's code address. This field may be absent.
28471 @node GDB/MI Thread Information
28472 @subsection @sc{gdb/mi} Thread Information
28474 Whenever @value{GDBN} has to report an information about a thread, it
28475 uses a tuple with the following fields. The fields are always present unless
28480 The global numeric id assigned to the thread by @value{GDBN}.
28483 The target-specific string identifying the thread.
28486 Additional information about the thread provided by the target.
28487 It is supposed to be human-readable and not interpreted by the
28488 frontend. This field is optional.
28491 The name of the thread. If the user specified a name using the
28492 @code{thread name} command, then this name is given. Otherwise, if
28493 @value{GDBN} can extract the thread name from the target, then that
28494 name is given. If @value{GDBN} cannot find the thread name, then this
28498 The execution state of the thread, either @samp{stopped} or @samp{running},
28499 depending on whether the thread is presently running.
28502 The stack frame currently executing in the thread. This field is only present
28503 if the thread is stopped. Its format is documented in
28504 @ref{GDB/MI Frame Information}.
28507 The value of this field is an integer number of the processor core the
28508 thread was last seen on. This field is optional.
28511 @node GDB/MI Ada Exception Information
28512 @subsection @sc{gdb/mi} Ada Exception Information
28514 Whenever a @code{*stopped} record is emitted because the program
28515 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28516 @value{GDBN} provides the name of the exception that was raised via
28517 the @code{exception-name} field. Also, for exceptions that were raised
28518 with an exception message, @value{GDBN} provides that message via
28519 the @code{exception-message} field.
28521 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28522 @node GDB/MI Simple Examples
28523 @section Simple Examples of @sc{gdb/mi} Interaction
28524 @cindex @sc{gdb/mi}, simple examples
28526 This subsection presents several simple examples of interaction using
28527 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28528 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28529 the output received from @sc{gdb/mi}.
28531 Note the line breaks shown in the examples are here only for
28532 readability, they don't appear in the real output.
28534 @subheading Setting a Breakpoint
28536 Setting a breakpoint generates synchronous output which contains detailed
28537 information of the breakpoint.
28540 -> -break-insert main
28541 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28542 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28543 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28548 @subheading Program Execution
28550 Program execution generates asynchronous records and MI gives the
28551 reason that execution stopped.
28557 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28558 frame=@{addr="0x08048564",func="main",
28559 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28560 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
28561 arch="i386:x86_64"@}
28566 <- *stopped,reason="exited-normally"
28570 @subheading Quitting @value{GDBN}
28572 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28580 Please note that @samp{^exit} is printed immediately, but it might
28581 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28582 performs necessary cleanups, including killing programs being debugged
28583 or disconnecting from debug hardware, so the frontend should wait till
28584 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28585 fails to exit in reasonable time.
28587 @subheading A Bad Command
28589 Here's what happens if you pass a non-existent command:
28593 <- ^error,msg="Undefined MI command: rubbish"
28598 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28599 @node GDB/MI Command Description Format
28600 @section @sc{gdb/mi} Command Description Format
28602 The remaining sections describe blocks of commands. Each block of
28603 commands is laid out in a fashion similar to this section.
28605 @subheading Motivation
28607 The motivation for this collection of commands.
28609 @subheading Introduction
28611 A brief introduction to this collection of commands as a whole.
28613 @subheading Commands
28615 For each command in the block, the following is described:
28617 @subsubheading Synopsis
28620 -command @var{args}@dots{}
28623 @subsubheading Result
28625 @subsubheading @value{GDBN} Command
28627 The corresponding @value{GDBN} CLI command(s), if any.
28629 @subsubheading Example
28631 Example(s) formatted for readability. Some of the described commands have
28632 not been implemented yet and these are labeled N.A.@: (not available).
28635 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28636 @node GDB/MI Breakpoint Commands
28637 @section @sc{gdb/mi} Breakpoint Commands
28639 @cindex breakpoint commands for @sc{gdb/mi}
28640 @cindex @sc{gdb/mi}, breakpoint commands
28641 This section documents @sc{gdb/mi} commands for manipulating
28644 @subheading The @code{-break-after} Command
28645 @findex -break-after
28647 @subsubheading Synopsis
28650 -break-after @var{number} @var{count}
28653 The breakpoint number @var{number} is not in effect until it has been
28654 hit @var{count} times. To see how this is reflected in the output of
28655 the @samp{-break-list} command, see the description of the
28656 @samp{-break-list} command below.
28658 @subsubheading @value{GDBN} Command
28660 The corresponding @value{GDBN} command is @samp{ignore}.
28662 @subsubheading Example
28667 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28668 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28669 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28677 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28678 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28679 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28680 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28681 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28682 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28683 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28684 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28685 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28686 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28691 @subheading The @code{-break-catch} Command
28692 @findex -break-catch
28695 @subheading The @code{-break-commands} Command
28696 @findex -break-commands
28698 @subsubheading Synopsis
28701 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28704 Specifies the CLI commands that should be executed when breakpoint
28705 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28706 are the commands. If no command is specified, any previously-set
28707 commands are cleared. @xref{Break Commands}. Typical use of this
28708 functionality is tracing a program, that is, printing of values of
28709 some variables whenever breakpoint is hit and then continuing.
28711 @subsubheading @value{GDBN} Command
28713 The corresponding @value{GDBN} command is @samp{commands}.
28715 @subsubheading Example
28720 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28721 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28722 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28725 -break-commands 1 "print v" "continue"
28730 @subheading The @code{-break-condition} Command
28731 @findex -break-condition
28733 @subsubheading Synopsis
28736 -break-condition @var{number} @var{expr}
28739 Breakpoint @var{number} will stop the program only if the condition in
28740 @var{expr} is true. The condition becomes part of the
28741 @samp{-break-list} output (see the description of the @samp{-break-list}
28744 @subsubheading @value{GDBN} Command
28746 The corresponding @value{GDBN} command is @samp{condition}.
28748 @subsubheading Example
28752 -break-condition 1 1
28756 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28757 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28758 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28759 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28760 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28761 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28762 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28763 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28764 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28765 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28769 @subheading The @code{-break-delete} Command
28770 @findex -break-delete
28772 @subsubheading Synopsis
28775 -break-delete ( @var{breakpoint} )+
28778 Delete the breakpoint(s) whose number(s) are specified in the argument
28779 list. This is obviously reflected in the breakpoint list.
28781 @subsubheading @value{GDBN} Command
28783 The corresponding @value{GDBN} command is @samp{delete}.
28785 @subsubheading Example
28793 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28794 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28795 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28796 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28797 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28798 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28799 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28804 @subheading The @code{-break-disable} Command
28805 @findex -break-disable
28807 @subsubheading Synopsis
28810 -break-disable ( @var{breakpoint} )+
28813 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28814 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28816 @subsubheading @value{GDBN} Command
28818 The corresponding @value{GDBN} command is @samp{disable}.
28820 @subsubheading Example
28828 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28829 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28830 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28831 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28832 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28833 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28834 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28835 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28836 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28837 line="5",thread-groups=["i1"],times="0"@}]@}
28841 @subheading The @code{-break-enable} Command
28842 @findex -break-enable
28844 @subsubheading Synopsis
28847 -break-enable ( @var{breakpoint} )+
28850 Enable (previously disabled) @var{breakpoint}(s).
28852 @subsubheading @value{GDBN} Command
28854 The corresponding @value{GDBN} command is @samp{enable}.
28856 @subsubheading Example
28864 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28865 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28866 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28867 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28868 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28869 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28870 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28871 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28872 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28873 line="5",thread-groups=["i1"],times="0"@}]@}
28877 @subheading The @code{-break-info} Command
28878 @findex -break-info
28880 @subsubheading Synopsis
28883 -break-info @var{breakpoint}
28887 Get information about a single breakpoint.
28889 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28890 Information}, for details on the format of each breakpoint in the
28893 @subsubheading @value{GDBN} Command
28895 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28897 @subsubheading Example
28900 @subheading The @code{-break-insert} Command
28901 @findex -break-insert
28902 @anchor{-break-insert}
28904 @subsubheading Synopsis
28907 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28908 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28909 [ -p @var{thread-id} ] [ @var{location} ]
28913 If specified, @var{location}, can be one of:
28916 @item linespec location
28917 A linespec location. @xref{Linespec Locations}.
28919 @item explicit location
28920 An explicit location. @sc{gdb/mi} explicit locations are
28921 analogous to the CLI's explicit locations using the option names
28922 listed below. @xref{Explicit Locations}.
28925 @item --source @var{filename}
28926 The source file name of the location. This option requires the use
28927 of either @samp{--function} or @samp{--line}.
28929 @item --function @var{function}
28930 The name of a function or method.
28932 @item --label @var{label}
28933 The name of a label.
28935 @item --line @var{lineoffset}
28936 An absolute or relative line offset from the start of the location.
28939 @item address location
28940 An address location, *@var{address}. @xref{Address Locations}.
28944 The possible optional parameters of this command are:
28948 Insert a temporary breakpoint.
28950 Insert a hardware breakpoint.
28952 If @var{location} cannot be parsed (for example if it
28953 refers to unknown files or functions), create a pending
28954 breakpoint. Without this flag, @value{GDBN} will report
28955 an error, and won't create a breakpoint, if @var{location}
28958 Create a disabled breakpoint.
28960 Create a tracepoint. @xref{Tracepoints}. When this parameter
28961 is used together with @samp{-h}, a fast tracepoint is created.
28962 @item -c @var{condition}
28963 Make the breakpoint conditional on @var{condition}.
28964 @item -i @var{ignore-count}
28965 Initialize the @var{ignore-count}.
28966 @item -p @var{thread-id}
28967 Restrict the breakpoint to the thread with the specified global
28971 @subsubheading Result
28973 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28974 resulting breakpoint.
28976 Note: this format is open to change.
28977 @c An out-of-band breakpoint instead of part of the result?
28979 @subsubheading @value{GDBN} Command
28981 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28982 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28984 @subsubheading Example
28989 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28990 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28993 -break-insert -t foo
28994 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28995 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28999 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29000 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29001 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29002 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29003 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29004 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29005 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29006 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29007 addr="0x0001072c", func="main",file="recursive2.c",
29008 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
29010 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
29011 addr="0x00010774",func="foo",file="recursive2.c",
29012 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
29015 @c -break-insert -r foo.*
29016 @c ~int foo(int, int);
29017 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
29018 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
29023 @subheading The @code{-dprintf-insert} Command
29024 @findex -dprintf-insert
29026 @subsubheading Synopsis
29029 -dprintf-insert [ -t ] [ -f ] [ -d ]
29030 [ -c @var{condition} ] [ -i @var{ignore-count} ]
29031 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
29036 If supplied, @var{location} may be specified the same way as for
29037 the @code{-break-insert} command. @xref{-break-insert}.
29039 The possible optional parameters of this command are:
29043 Insert a temporary breakpoint.
29045 If @var{location} cannot be parsed (for example, if it
29046 refers to unknown files or functions), create a pending
29047 breakpoint. Without this flag, @value{GDBN} will report
29048 an error, and won't create a breakpoint, if @var{location}
29051 Create a disabled breakpoint.
29052 @item -c @var{condition}
29053 Make the breakpoint conditional on @var{condition}.
29054 @item -i @var{ignore-count}
29055 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
29056 to @var{ignore-count}.
29057 @item -p @var{thread-id}
29058 Restrict the breakpoint to the thread with the specified global
29062 @subsubheading Result
29064 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29065 resulting breakpoint.
29067 @c An out-of-band breakpoint instead of part of the result?
29069 @subsubheading @value{GDBN} Command
29071 The corresponding @value{GDBN} command is @samp{dprintf}.
29073 @subsubheading Example
29077 4-dprintf-insert foo "At foo entry\n"
29078 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
29079 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
29080 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
29081 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
29082 original-location="foo"@}
29084 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
29085 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
29086 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
29087 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
29088 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
29089 original-location="mi-dprintf.c:26"@}
29093 @subheading The @code{-break-list} Command
29094 @findex -break-list
29096 @subsubheading Synopsis
29102 Displays the list of inserted breakpoints, showing the following fields:
29106 number of the breakpoint
29108 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
29110 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
29113 is the breakpoint enabled or no: @samp{y} or @samp{n}
29115 memory location at which the breakpoint is set
29117 logical location of the breakpoint, expressed by function name, file
29119 @item Thread-groups
29120 list of thread groups to which this breakpoint applies
29122 number of times the breakpoint has been hit
29125 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
29126 @code{body} field is an empty list.
29128 @subsubheading @value{GDBN} Command
29130 The corresponding @value{GDBN} command is @samp{info break}.
29132 @subsubheading Example
29137 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29138 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29139 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29140 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29141 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29142 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29143 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29144 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29145 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
29147 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
29148 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
29149 line="13",thread-groups=["i1"],times="0"@}]@}
29153 Here's an example of the result when there are no breakpoints:
29158 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
29159 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29160 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29161 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29162 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29163 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29164 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29169 @subheading The @code{-break-passcount} Command
29170 @findex -break-passcount
29172 @subsubheading Synopsis
29175 -break-passcount @var{tracepoint-number} @var{passcount}
29178 Set the passcount for tracepoint @var{tracepoint-number} to
29179 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
29180 is not a tracepoint, error is emitted. This corresponds to CLI
29181 command @samp{passcount}.
29183 @subheading The @code{-break-watch} Command
29184 @findex -break-watch
29186 @subsubheading Synopsis
29189 -break-watch [ -a | -r ]
29192 Create a watchpoint. With the @samp{-a} option it will create an
29193 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
29194 read from or on a write to the memory location. With the @samp{-r}
29195 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
29196 trigger only when the memory location is accessed for reading. Without
29197 either of the options, the watchpoint created is a regular watchpoint,
29198 i.e., it will trigger when the memory location is accessed for writing.
29199 @xref{Set Watchpoints, , Setting Watchpoints}.
29201 Note that @samp{-break-list} will report a single list of watchpoints and
29202 breakpoints inserted.
29204 @subsubheading @value{GDBN} Command
29206 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
29209 @subsubheading Example
29211 Setting a watchpoint on a variable in the @code{main} function:
29216 ^done,wpt=@{number="2",exp="x"@}
29221 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
29222 value=@{old="-268439212",new="55"@},
29223 frame=@{func="main",args=[],file="recursive2.c",
29224 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
29228 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
29229 the program execution twice: first for the variable changing value, then
29230 for the watchpoint going out of scope.
29235 ^done,wpt=@{number="5",exp="C"@}
29240 *stopped,reason="watchpoint-trigger",
29241 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
29242 frame=@{func="callee4",args=[],
29243 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29244 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29245 arch="i386:x86_64"@}
29250 *stopped,reason="watchpoint-scope",wpnum="5",
29251 frame=@{func="callee3",args=[@{name="strarg",
29252 value="0x11940 \"A string argument.\""@}],
29253 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29254 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29255 arch="i386:x86_64"@}
29259 Listing breakpoints and watchpoints, at different points in the program
29260 execution. Note that once the watchpoint goes out of scope, it is
29266 ^done,wpt=@{number="2",exp="C"@}
29269 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29270 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29271 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29272 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29273 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29274 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29275 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29276 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29277 addr="0x00010734",func="callee4",
29278 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29279 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29281 bkpt=@{number="2",type="watchpoint",disp="keep",
29282 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29287 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29288 value=@{old="-276895068",new="3"@},
29289 frame=@{func="callee4",args=[],
29290 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29291 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29292 arch="i386:x86_64"@}
29295 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29296 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29297 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29298 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29299 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29300 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29301 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29302 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29303 addr="0x00010734",func="callee4",
29304 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29305 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29307 bkpt=@{number="2",type="watchpoint",disp="keep",
29308 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29312 ^done,reason="watchpoint-scope",wpnum="2",
29313 frame=@{func="callee3",args=[@{name="strarg",
29314 value="0x11940 \"A string argument.\""@}],
29315 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29316 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29317 arch="i386:x86_64"@}
29320 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29321 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29322 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29323 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29324 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29325 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29326 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29327 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29328 addr="0x00010734",func="callee4",
29329 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29330 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29331 thread-groups=["i1"],times="1"@}]@}
29336 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29337 @node GDB/MI Catchpoint Commands
29338 @section @sc{gdb/mi} Catchpoint Commands
29340 This section documents @sc{gdb/mi} commands for manipulating
29344 * Shared Library GDB/MI Catchpoint Commands::
29345 * Ada Exception GDB/MI Catchpoint Commands::
29348 @node Shared Library GDB/MI Catchpoint Commands
29349 @subsection Shared Library @sc{gdb/mi} Catchpoints
29351 @subheading The @code{-catch-load} Command
29352 @findex -catch-load
29354 @subsubheading Synopsis
29357 -catch-load [ -t ] [ -d ] @var{regexp}
29360 Add a catchpoint for library load events. If the @samp{-t} option is used,
29361 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29362 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29363 in a disabled state. The @samp{regexp} argument is a regular
29364 expression used to match the name of the loaded library.
29367 @subsubheading @value{GDBN} Command
29369 The corresponding @value{GDBN} command is @samp{catch load}.
29371 @subsubheading Example
29374 -catch-load -t foo.so
29375 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29376 what="load of library matching foo.so",catch-type="load",times="0"@}
29381 @subheading The @code{-catch-unload} Command
29382 @findex -catch-unload
29384 @subsubheading Synopsis
29387 -catch-unload [ -t ] [ -d ] @var{regexp}
29390 Add a catchpoint for library unload events. If the @samp{-t} option is
29391 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29392 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29393 created in a disabled state. The @samp{regexp} argument is a regular
29394 expression used to match the name of the unloaded library.
29396 @subsubheading @value{GDBN} Command
29398 The corresponding @value{GDBN} command is @samp{catch unload}.
29400 @subsubheading Example
29403 -catch-unload -d bar.so
29404 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29405 what="load of library matching bar.so",catch-type="unload",times="0"@}
29409 @node Ada Exception GDB/MI Catchpoint Commands
29410 @subsection Ada Exception @sc{gdb/mi} Catchpoints
29412 The following @sc{gdb/mi} commands can be used to create catchpoints
29413 that stop the execution when Ada exceptions are being raised.
29415 @subheading The @code{-catch-assert} Command
29416 @findex -catch-assert
29418 @subsubheading Synopsis
29421 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
29424 Add a catchpoint for failed Ada assertions.
29426 The possible optional parameters for this command are:
29429 @item -c @var{condition}
29430 Make the catchpoint conditional on @var{condition}.
29432 Create a disabled catchpoint.
29434 Create a temporary catchpoint.
29437 @subsubheading @value{GDBN} Command
29439 The corresponding @value{GDBN} command is @samp{catch assert}.
29441 @subsubheading Example
29445 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
29446 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
29447 thread-groups=["i1"],times="0",
29448 original-location="__gnat_debug_raise_assert_failure"@}
29452 @subheading The @code{-catch-exception} Command
29453 @findex -catch-exception
29455 @subsubheading Synopsis
29458 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
29462 Add a catchpoint stopping when Ada exceptions are raised.
29463 By default, the command stops the program when any Ada exception
29464 gets raised. But it is also possible, by using some of the
29465 optional parameters described below, to create more selective
29468 The possible optional parameters for this command are:
29471 @item -c @var{condition}
29472 Make the catchpoint conditional on @var{condition}.
29474 Create a disabled catchpoint.
29475 @item -e @var{exception-name}
29476 Only stop when @var{exception-name} is raised. This option cannot
29477 be used combined with @samp{-u}.
29479 Create a temporary catchpoint.
29481 Stop only when an unhandled exception gets raised. This option
29482 cannot be used combined with @samp{-e}.
29485 @subsubheading @value{GDBN} Command
29487 The corresponding @value{GDBN} commands are @samp{catch exception}
29488 and @samp{catch exception unhandled}.
29490 @subsubheading Example
29493 -catch-exception -e Program_Error
29494 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
29495 enabled="y",addr="0x0000000000404874",
29496 what="`Program_Error' Ada exception", thread-groups=["i1"],
29497 times="0",original-location="__gnat_debug_raise_exception"@}
29501 @subheading The @code{-catch-handlers} Command
29502 @findex -catch-handlers
29504 @subsubheading Synopsis
29507 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
29511 Add a catchpoint stopping when Ada exceptions are handled.
29512 By default, the command stops the program when any Ada exception
29513 gets handled. But it is also possible, by using some of the
29514 optional parameters described below, to create more selective
29517 The possible optional parameters for this command are:
29520 @item -c @var{condition}
29521 Make the catchpoint conditional on @var{condition}.
29523 Create a disabled catchpoint.
29524 @item -e @var{exception-name}
29525 Only stop when @var{exception-name} is handled.
29527 Create a temporary catchpoint.
29530 @subsubheading @value{GDBN} Command
29532 The corresponding @value{GDBN} command is @samp{catch handlers}.
29534 @subsubheading Example
29537 -catch-handlers -e Constraint_Error
29538 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
29539 enabled="y",addr="0x0000000000402f68",
29540 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
29541 times="0",original-location="__gnat_begin_handler"@}
29545 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29546 @node GDB/MI Program Context
29547 @section @sc{gdb/mi} Program Context
29549 @subheading The @code{-exec-arguments} Command
29550 @findex -exec-arguments
29553 @subsubheading Synopsis
29556 -exec-arguments @var{args}
29559 Set the inferior program arguments, to be used in the next
29562 @subsubheading @value{GDBN} Command
29564 The corresponding @value{GDBN} command is @samp{set args}.
29566 @subsubheading Example
29570 -exec-arguments -v word
29577 @subheading The @code{-exec-show-arguments} Command
29578 @findex -exec-show-arguments
29580 @subsubheading Synopsis
29583 -exec-show-arguments
29586 Print the arguments of the program.
29588 @subsubheading @value{GDBN} Command
29590 The corresponding @value{GDBN} command is @samp{show args}.
29592 @subsubheading Example
29597 @subheading The @code{-environment-cd} Command
29598 @findex -environment-cd
29600 @subsubheading Synopsis
29603 -environment-cd @var{pathdir}
29606 Set @value{GDBN}'s working directory.
29608 @subsubheading @value{GDBN} Command
29610 The corresponding @value{GDBN} command is @samp{cd}.
29612 @subsubheading Example
29616 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29622 @subheading The @code{-environment-directory} Command
29623 @findex -environment-directory
29625 @subsubheading Synopsis
29628 -environment-directory [ -r ] [ @var{pathdir} ]+
29631 Add directories @var{pathdir} to beginning of search path for source files.
29632 If the @samp{-r} option is used, the search path is reset to the default
29633 search path. If directories @var{pathdir} are supplied in addition to the
29634 @samp{-r} option, the search path is first reset and then addition
29636 Multiple directories may be specified, separated by blanks. Specifying
29637 multiple directories in a single command
29638 results in the directories added to the beginning of the
29639 search path in the same order they were presented in the command.
29640 If blanks are needed as
29641 part of a directory name, double-quotes should be used around
29642 the name. In the command output, the path will show up separated
29643 by the system directory-separator character. The directory-separator
29644 character must not be used
29645 in any directory name.
29646 If no directories are specified, the current search path is displayed.
29648 @subsubheading @value{GDBN} Command
29650 The corresponding @value{GDBN} command is @samp{dir}.
29652 @subsubheading Example
29656 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29657 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29659 -environment-directory ""
29660 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29662 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29663 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29665 -environment-directory -r
29666 ^done,source-path="$cdir:$cwd"
29671 @subheading The @code{-environment-path} Command
29672 @findex -environment-path
29674 @subsubheading Synopsis
29677 -environment-path [ -r ] [ @var{pathdir} ]+
29680 Add directories @var{pathdir} to beginning of search path for object files.
29681 If the @samp{-r} option is used, the search path is reset to the original
29682 search path that existed at gdb start-up. If directories @var{pathdir} are
29683 supplied in addition to the
29684 @samp{-r} option, the search path is first reset and then addition
29686 Multiple directories may be specified, separated by blanks. Specifying
29687 multiple directories in a single command
29688 results in the directories added to the beginning of the
29689 search path in the same order they were presented in the command.
29690 If blanks are needed as
29691 part of a directory name, double-quotes should be used around
29692 the name. In the command output, the path will show up separated
29693 by the system directory-separator character. The directory-separator
29694 character must not be used
29695 in any directory name.
29696 If no directories are specified, the current path is displayed.
29699 @subsubheading @value{GDBN} Command
29701 The corresponding @value{GDBN} command is @samp{path}.
29703 @subsubheading Example
29708 ^done,path="/usr/bin"
29710 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29711 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29713 -environment-path -r /usr/local/bin
29714 ^done,path="/usr/local/bin:/usr/bin"
29719 @subheading The @code{-environment-pwd} Command
29720 @findex -environment-pwd
29722 @subsubheading Synopsis
29728 Show the current working directory.
29730 @subsubheading @value{GDBN} Command
29732 The corresponding @value{GDBN} command is @samp{pwd}.
29734 @subsubheading Example
29739 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29743 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29744 @node GDB/MI Thread Commands
29745 @section @sc{gdb/mi} Thread Commands
29748 @subheading The @code{-thread-info} Command
29749 @findex -thread-info
29751 @subsubheading Synopsis
29754 -thread-info [ @var{thread-id} ]
29757 Reports information about either a specific thread, if the
29758 @var{thread-id} parameter is present, or about all threads.
29759 @var{thread-id} is the thread's global thread ID. When printing
29760 information about all threads, also reports the global ID of the
29763 @subsubheading @value{GDBN} Command
29765 The @samp{info thread} command prints the same information
29768 @subsubheading Result
29770 The result contains the following attributes:
29774 A list of threads. The format of the elements of the list is described in
29775 @ref{GDB/MI Thread Information}.
29777 @item current-thread-id
29778 The global id of the currently selected thread. This field is omitted if there
29779 is no selected thread (for example, when the selected inferior is not running,
29780 and therefore has no threads) or if a @var{thread-id} argument was passed to
29785 @subsubheading Example
29790 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29791 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29792 args=[]@},state="running"@},
29793 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29794 frame=@{level="0",addr="0x0804891f",func="foo",
29795 args=[@{name="i",value="10"@}],
29796 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
29797 state="running"@}],
29798 current-thread-id="1"
29802 @subheading The @code{-thread-list-ids} Command
29803 @findex -thread-list-ids
29805 @subsubheading Synopsis
29811 Produces a list of the currently known global @value{GDBN} thread ids.
29812 At the end of the list it also prints the total number of such
29815 This command is retained for historical reasons, the
29816 @code{-thread-info} command should be used instead.
29818 @subsubheading @value{GDBN} Command
29820 Part of @samp{info threads} supplies the same information.
29822 @subsubheading Example
29827 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29828 current-thread-id="1",number-of-threads="3"
29833 @subheading The @code{-thread-select} Command
29834 @findex -thread-select
29836 @subsubheading Synopsis
29839 -thread-select @var{thread-id}
29842 Make thread with global thread number @var{thread-id} the current
29843 thread. It prints the number of the new current thread, and the
29844 topmost frame for that thread.
29846 This command is deprecated in favor of explicitly using the
29847 @samp{--thread} option to each command.
29849 @subsubheading @value{GDBN} Command
29851 The corresponding @value{GDBN} command is @samp{thread}.
29853 @subsubheading Example
29860 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29861 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29865 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29866 number-of-threads="3"
29869 ^done,new-thread-id="3",
29870 frame=@{level="0",func="vprintf",
29871 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29872 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
29876 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29877 @node GDB/MI Ada Tasking Commands
29878 @section @sc{gdb/mi} Ada Tasking Commands
29880 @subheading The @code{-ada-task-info} Command
29881 @findex -ada-task-info
29883 @subsubheading Synopsis
29886 -ada-task-info [ @var{task-id} ]
29889 Reports information about either a specific Ada task, if the
29890 @var{task-id} parameter is present, or about all Ada tasks.
29892 @subsubheading @value{GDBN} Command
29894 The @samp{info tasks} command prints the same information
29895 about all Ada tasks (@pxref{Ada Tasks}).
29897 @subsubheading Result
29899 The result is a table of Ada tasks. The following columns are
29900 defined for each Ada task:
29904 This field exists only for the current thread. It has the value @samp{*}.
29907 The identifier that @value{GDBN} uses to refer to the Ada task.
29910 The identifier that the target uses to refer to the Ada task.
29913 The global thread identifier of the thread corresponding to the Ada
29916 This field should always exist, as Ada tasks are always implemented
29917 on top of a thread. But if @value{GDBN} cannot find this corresponding
29918 thread for any reason, the field is omitted.
29921 This field exists only when the task was created by another task.
29922 In this case, it provides the ID of the parent task.
29925 The base priority of the task.
29928 The current state of the task. For a detailed description of the
29929 possible states, see @ref{Ada Tasks}.
29932 The name of the task.
29936 @subsubheading Example
29940 ^done,tasks=@{nr_rows="3",nr_cols="8",
29941 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29942 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29943 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29944 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29945 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29946 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29947 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29948 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29949 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29950 state="Child Termination Wait",name="main_task"@}]@}
29954 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29955 @node GDB/MI Program Execution
29956 @section @sc{gdb/mi} Program Execution
29958 These are the asynchronous commands which generate the out-of-band
29959 record @samp{*stopped}. Currently @value{GDBN} only really executes
29960 asynchronously with remote targets and this interaction is mimicked in
29963 @subheading The @code{-exec-continue} Command
29964 @findex -exec-continue
29966 @subsubheading Synopsis
29969 -exec-continue [--reverse] [--all|--thread-group N]
29972 Resumes the execution of the inferior program, which will continue
29973 to execute until it reaches a debugger stop event. If the
29974 @samp{--reverse} option is specified, execution resumes in reverse until
29975 it reaches a stop event. Stop events may include
29978 breakpoints or watchpoints
29980 signals or exceptions
29982 the end of the process (or its beginning under @samp{--reverse})
29984 the end or beginning of a replay log if one is being used.
29986 In all-stop mode (@pxref{All-Stop
29987 Mode}), may resume only one thread, or all threads, depending on the
29988 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29989 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29990 ignored in all-stop mode. If the @samp{--thread-group} options is
29991 specified, then all threads in that thread group are resumed.
29993 @subsubheading @value{GDBN} Command
29995 The corresponding @value{GDBN} corresponding is @samp{continue}.
29997 @subsubheading Example
30004 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
30005 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
30006 line="13",arch="i386:x86_64"@}
30011 @subheading The @code{-exec-finish} Command
30012 @findex -exec-finish
30014 @subsubheading Synopsis
30017 -exec-finish [--reverse]
30020 Resumes the execution of the inferior program until the current
30021 function is exited. Displays the results returned by the function.
30022 If the @samp{--reverse} option is specified, resumes the reverse
30023 execution of the inferior program until the point where current
30024 function was called.
30026 @subsubheading @value{GDBN} Command
30028 The corresponding @value{GDBN} command is @samp{finish}.
30030 @subsubheading Example
30032 Function returning @code{void}.
30039 *stopped,reason="function-finished",frame=@{func="main",args=[],
30040 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
30044 Function returning other than @code{void}. The name of the internal
30045 @value{GDBN} variable storing the result is printed, together with the
30052 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
30053 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
30054 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30055 arch="i386:x86_64"@},
30056 gdb-result-var="$1",return-value="0"
30061 @subheading The @code{-exec-interrupt} Command
30062 @findex -exec-interrupt
30064 @subsubheading Synopsis
30067 -exec-interrupt [--all|--thread-group N]
30070 Interrupts the background execution of the target. Note how the token
30071 associated with the stop message is the one for the execution command
30072 that has been interrupted. The token for the interrupt itself only
30073 appears in the @samp{^done} output. If the user is trying to
30074 interrupt a non-running program, an error message will be printed.
30076 Note that when asynchronous execution is enabled, this command is
30077 asynchronous just like other execution commands. That is, first the
30078 @samp{^done} response will be printed, and the target stop will be
30079 reported after that using the @samp{*stopped} notification.
30081 In non-stop mode, only the context thread is interrupted by default.
30082 All threads (in all inferiors) will be interrupted if the
30083 @samp{--all} option is specified. If the @samp{--thread-group}
30084 option is specified, all threads in that group will be interrupted.
30086 @subsubheading @value{GDBN} Command
30088 The corresponding @value{GDBN} command is @samp{interrupt}.
30090 @subsubheading Example
30101 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
30102 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
30103 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
30108 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
30112 @subheading The @code{-exec-jump} Command
30115 @subsubheading Synopsis
30118 -exec-jump @var{location}
30121 Resumes execution of the inferior program at the location specified by
30122 parameter. @xref{Specify Location}, for a description of the
30123 different forms of @var{location}.
30125 @subsubheading @value{GDBN} Command
30127 The corresponding @value{GDBN} command is @samp{jump}.
30129 @subsubheading Example
30132 -exec-jump foo.c:10
30133 *running,thread-id="all"
30138 @subheading The @code{-exec-next} Command
30141 @subsubheading Synopsis
30144 -exec-next [--reverse]
30147 Resumes execution of the inferior program, stopping when the beginning
30148 of the next source line is reached.
30150 If the @samp{--reverse} option is specified, resumes reverse execution
30151 of the inferior program, stopping at the beginning of the previous
30152 source line. If you issue this command on the first line of a
30153 function, it will take you back to the caller of that function, to the
30154 source line where the function was called.
30157 @subsubheading @value{GDBN} Command
30159 The corresponding @value{GDBN} command is @samp{next}.
30161 @subsubheading Example
30167 *stopped,reason="end-stepping-range",line="8",file="hello.c"
30172 @subheading The @code{-exec-next-instruction} Command
30173 @findex -exec-next-instruction
30175 @subsubheading Synopsis
30178 -exec-next-instruction [--reverse]
30181 Executes one machine instruction. If the instruction is a function
30182 call, continues until the function returns. If the program stops at an
30183 instruction in the middle of a source line, the address will be
30186 If the @samp{--reverse} option is specified, resumes reverse execution
30187 of the inferior program, stopping at the previous instruction. If the
30188 previously executed instruction was a return from another function,
30189 it will continue to execute in reverse until the call to that function
30190 (from the current stack frame) is reached.
30192 @subsubheading @value{GDBN} Command
30194 The corresponding @value{GDBN} command is @samp{nexti}.
30196 @subsubheading Example
30200 -exec-next-instruction
30204 *stopped,reason="end-stepping-range",
30205 addr="0x000100d4",line="5",file="hello.c"
30210 @subheading The @code{-exec-return} Command
30211 @findex -exec-return
30213 @subsubheading Synopsis
30219 Makes current function return immediately. Doesn't execute the inferior.
30220 Displays the new current frame.
30222 @subsubheading @value{GDBN} Command
30224 The corresponding @value{GDBN} command is @samp{return}.
30226 @subsubheading Example
30230 200-break-insert callee4
30231 200^done,bkpt=@{number="1",addr="0x00010734",
30232 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
30237 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30238 frame=@{func="callee4",args=[],
30239 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30240 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30241 arch="i386:x86_64"@}
30247 111^done,frame=@{level="0",func="callee3",
30248 args=[@{name="strarg",
30249 value="0x11940 \"A string argument.\""@}],
30250 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30251 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
30252 arch="i386:x86_64"@}
30257 @subheading The @code{-exec-run} Command
30260 @subsubheading Synopsis
30263 -exec-run [ --all | --thread-group N ] [ --start ]
30266 Starts execution of the inferior from the beginning. The inferior
30267 executes until either a breakpoint is encountered or the program
30268 exits. In the latter case the output will include an exit code, if
30269 the program has exited exceptionally.
30271 When neither the @samp{--all} nor the @samp{--thread-group} option
30272 is specified, the current inferior is started. If the
30273 @samp{--thread-group} option is specified, it should refer to a thread
30274 group of type @samp{process}, and that thread group will be started.
30275 If the @samp{--all} option is specified, then all inferiors will be started.
30277 Using the @samp{--start} option instructs the debugger to stop
30278 the execution at the start of the inferior's main subprogram,
30279 following the same behavior as the @code{start} command
30280 (@pxref{Starting}).
30282 @subsubheading @value{GDBN} Command
30284 The corresponding @value{GDBN} command is @samp{run}.
30286 @subsubheading Examples
30291 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
30296 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30297 frame=@{func="main",args=[],file="recursive2.c",
30298 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
30303 Program exited normally:
30311 *stopped,reason="exited-normally"
30316 Program exited exceptionally:
30324 *stopped,reason="exited",exit-code="01"
30328 Another way the program can terminate is if it receives a signal such as
30329 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
30333 *stopped,reason="exited-signalled",signal-name="SIGINT",
30334 signal-meaning="Interrupt"
30338 @c @subheading -exec-signal
30341 @subheading The @code{-exec-step} Command
30344 @subsubheading Synopsis
30347 -exec-step [--reverse]
30350 Resumes execution of the inferior program, stopping when the beginning
30351 of the next source line is reached, if the next source line is not a
30352 function call. If it is, stop at the first instruction of the called
30353 function. If the @samp{--reverse} option is specified, resumes reverse
30354 execution of the inferior program, stopping at the beginning of the
30355 previously executed source line.
30357 @subsubheading @value{GDBN} Command
30359 The corresponding @value{GDBN} command is @samp{step}.
30361 @subsubheading Example
30363 Stepping into a function:
30369 *stopped,reason="end-stepping-range",
30370 frame=@{func="foo",args=[@{name="a",value="10"@},
30371 @{name="b",value="0"@}],file="recursive2.c",
30372 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
30382 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
30387 @subheading The @code{-exec-step-instruction} Command
30388 @findex -exec-step-instruction
30390 @subsubheading Synopsis
30393 -exec-step-instruction [--reverse]
30396 Resumes the inferior which executes one machine instruction. If the
30397 @samp{--reverse} option is specified, resumes reverse execution of the
30398 inferior program, stopping at the previously executed instruction.
30399 The output, once @value{GDBN} has stopped, will vary depending on
30400 whether we have stopped in the middle of a source line or not. In the
30401 former case, the address at which the program stopped will be printed
30404 @subsubheading @value{GDBN} Command
30406 The corresponding @value{GDBN} command is @samp{stepi}.
30408 @subsubheading Example
30412 -exec-step-instruction
30416 *stopped,reason="end-stepping-range",
30417 frame=@{func="foo",args=[],file="try.c",
30418 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
30420 -exec-step-instruction
30424 *stopped,reason="end-stepping-range",
30425 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
30426 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
30431 @subheading The @code{-exec-until} Command
30432 @findex -exec-until
30434 @subsubheading Synopsis
30437 -exec-until [ @var{location} ]
30440 Executes the inferior until the @var{location} specified in the
30441 argument is reached. If there is no argument, the inferior executes
30442 until a source line greater than the current one is reached. The
30443 reason for stopping in this case will be @samp{location-reached}.
30445 @subsubheading @value{GDBN} Command
30447 The corresponding @value{GDBN} command is @samp{until}.
30449 @subsubheading Example
30453 -exec-until recursive2.c:6
30457 *stopped,reason="location-reached",frame=@{func="main",args=[],
30458 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
30459 arch="i386:x86_64"@}
30464 @subheading -file-clear
30465 Is this going away????
30468 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30469 @node GDB/MI Stack Manipulation
30470 @section @sc{gdb/mi} Stack Manipulation Commands
30472 @subheading The @code{-enable-frame-filters} Command
30473 @findex -enable-frame-filters
30476 -enable-frame-filters
30479 @value{GDBN} allows Python-based frame filters to affect the output of
30480 the MI commands relating to stack traces. As there is no way to
30481 implement this in a fully backward-compatible way, a front end must
30482 request that this functionality be enabled.
30484 Once enabled, this feature cannot be disabled.
30486 Note that if Python support has not been compiled into @value{GDBN},
30487 this command will still succeed (and do nothing).
30489 @subheading The @code{-stack-info-frame} Command
30490 @findex -stack-info-frame
30492 @subsubheading Synopsis
30498 Get info on the selected frame.
30500 @subsubheading @value{GDBN} Command
30502 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
30503 (without arguments).
30505 @subsubheading Example
30510 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
30511 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30512 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
30513 arch="i386:x86_64"@}
30517 @subheading The @code{-stack-info-depth} Command
30518 @findex -stack-info-depth
30520 @subsubheading Synopsis
30523 -stack-info-depth [ @var{max-depth} ]
30526 Return the depth of the stack. If the integer argument @var{max-depth}
30527 is specified, do not count beyond @var{max-depth} frames.
30529 @subsubheading @value{GDBN} Command
30531 There's no equivalent @value{GDBN} command.
30533 @subsubheading Example
30535 For a stack with frame levels 0 through 11:
30542 -stack-info-depth 4
30545 -stack-info-depth 12
30548 -stack-info-depth 11
30551 -stack-info-depth 13
30556 @anchor{-stack-list-arguments}
30557 @subheading The @code{-stack-list-arguments} Command
30558 @findex -stack-list-arguments
30560 @subsubheading Synopsis
30563 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30564 [ @var{low-frame} @var{high-frame} ]
30567 Display a list of the arguments for the frames between @var{low-frame}
30568 and @var{high-frame} (inclusive). If @var{low-frame} and
30569 @var{high-frame} are not provided, list the arguments for the whole
30570 call stack. If the two arguments are equal, show the single frame
30571 at the corresponding level. It is an error if @var{low-frame} is
30572 larger than the actual number of frames. On the other hand,
30573 @var{high-frame} may be larger than the actual number of frames, in
30574 which case only existing frames will be returned.
30576 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30577 the variables; if it is 1 or @code{--all-values}, print also their
30578 values; and if it is 2 or @code{--simple-values}, print the name,
30579 type and value for simple data types, and the name and type for arrays,
30580 structures and unions. If the option @code{--no-frame-filters} is
30581 supplied, then Python frame filters will not be executed.
30583 If the @code{--skip-unavailable} option is specified, arguments that
30584 are not available are not listed. Partially available arguments
30585 are still displayed, however.
30587 Use of this command to obtain arguments in a single frame is
30588 deprecated in favor of the @samp{-stack-list-variables} command.
30590 @subsubheading @value{GDBN} Command
30592 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30593 @samp{gdb_get_args} command which partially overlaps with the
30594 functionality of @samp{-stack-list-arguments}.
30596 @subsubheading Example
30603 frame=@{level="0",addr="0x00010734",func="callee4",
30604 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30605 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30606 arch="i386:x86_64"@},
30607 frame=@{level="1",addr="0x0001076c",func="callee3",
30608 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30609 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
30610 arch="i386:x86_64"@},
30611 frame=@{level="2",addr="0x0001078c",func="callee2",
30612 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30613 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
30614 arch="i386:x86_64"@},
30615 frame=@{level="3",addr="0x000107b4",func="callee1",
30616 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30617 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
30618 arch="i386:x86_64"@},
30619 frame=@{level="4",addr="0x000107e0",func="main",
30620 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30621 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
30622 arch="i386:x86_64"@}]
30624 -stack-list-arguments 0
30627 frame=@{level="0",args=[]@},
30628 frame=@{level="1",args=[name="strarg"]@},
30629 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30630 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30631 frame=@{level="4",args=[]@}]
30633 -stack-list-arguments 1
30636 frame=@{level="0",args=[]@},
30638 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30639 frame=@{level="2",args=[
30640 @{name="intarg",value="2"@},
30641 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30642 @{frame=@{level="3",args=[
30643 @{name="intarg",value="2"@},
30644 @{name="strarg",value="0x11940 \"A string argument.\""@},
30645 @{name="fltarg",value="3.5"@}]@},
30646 frame=@{level="4",args=[]@}]
30648 -stack-list-arguments 0 2 2
30649 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30651 -stack-list-arguments 1 2 2
30652 ^done,stack-args=[frame=@{level="2",
30653 args=[@{name="intarg",value="2"@},
30654 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30658 @c @subheading -stack-list-exception-handlers
30661 @anchor{-stack-list-frames}
30662 @subheading The @code{-stack-list-frames} Command
30663 @findex -stack-list-frames
30665 @subsubheading Synopsis
30668 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
30671 List the frames currently on the stack. For each frame it displays the
30676 The frame number, 0 being the topmost frame, i.e., the innermost function.
30678 The @code{$pc} value for that frame.
30682 File name of the source file where the function lives.
30683 @item @var{fullname}
30684 The full file name of the source file where the function lives.
30686 Line number corresponding to the @code{$pc}.
30688 The shared library where this function is defined. This is only given
30689 if the frame's function is not known.
30691 Frame's architecture.
30694 If invoked without arguments, this command prints a backtrace for the
30695 whole stack. If given two integer arguments, it shows the frames whose
30696 levels are between the two arguments (inclusive). If the two arguments
30697 are equal, it shows the single frame at the corresponding level. It is
30698 an error if @var{low-frame} is larger than the actual number of
30699 frames. On the other hand, @var{high-frame} may be larger than the
30700 actual number of frames, in which case only existing frames will be
30701 returned. If the option @code{--no-frame-filters} is supplied, then
30702 Python frame filters will not be executed.
30704 @subsubheading @value{GDBN} Command
30706 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30708 @subsubheading Example
30710 Full stack backtrace:
30716 [frame=@{level="0",addr="0x0001076c",func="foo",
30717 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
30718 arch="i386:x86_64"@},
30719 frame=@{level="1",addr="0x000107a4",func="foo",
30720 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30721 arch="i386:x86_64"@},
30722 frame=@{level="2",addr="0x000107a4",func="foo",
30723 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30724 arch="i386:x86_64"@},
30725 frame=@{level="3",addr="0x000107a4",func="foo",
30726 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30727 arch="i386:x86_64"@},
30728 frame=@{level="4",addr="0x000107a4",func="foo",
30729 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30730 arch="i386:x86_64"@},
30731 frame=@{level="5",addr="0x000107a4",func="foo",
30732 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30733 arch="i386:x86_64"@},
30734 frame=@{level="6",addr="0x000107a4",func="foo",
30735 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30736 arch="i386:x86_64"@},
30737 frame=@{level="7",addr="0x000107a4",func="foo",
30738 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30739 arch="i386:x86_64"@},
30740 frame=@{level="8",addr="0x000107a4",func="foo",
30741 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30742 arch="i386:x86_64"@},
30743 frame=@{level="9",addr="0x000107a4",func="foo",
30744 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30745 arch="i386:x86_64"@},
30746 frame=@{level="10",addr="0x000107a4",func="foo",
30747 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30748 arch="i386:x86_64"@},
30749 frame=@{level="11",addr="0x00010738",func="main",
30750 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
30751 arch="i386:x86_64"@}]
30755 Show frames between @var{low_frame} and @var{high_frame}:
30759 -stack-list-frames 3 5
30761 [frame=@{level="3",addr="0x000107a4",func="foo",
30762 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30763 arch="i386:x86_64"@},
30764 frame=@{level="4",addr="0x000107a4",func="foo",
30765 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30766 arch="i386:x86_64"@},
30767 frame=@{level="5",addr="0x000107a4",func="foo",
30768 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30769 arch="i386:x86_64"@}]
30773 Show a single frame:
30777 -stack-list-frames 3 3
30779 [frame=@{level="3",addr="0x000107a4",func="foo",
30780 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30781 arch="i386:x86_64"@}]
30786 @subheading The @code{-stack-list-locals} Command
30787 @findex -stack-list-locals
30788 @anchor{-stack-list-locals}
30790 @subsubheading Synopsis
30793 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30796 Display the local variable names for the selected frame. If
30797 @var{print-values} is 0 or @code{--no-values}, print only the names of
30798 the variables; if it is 1 or @code{--all-values}, print also their
30799 values; and if it is 2 or @code{--simple-values}, print the name,
30800 type and value for simple data types, and the name and type for arrays,
30801 structures and unions. In this last case, a frontend can immediately
30802 display the value of simple data types and create variable objects for
30803 other data types when the user wishes to explore their values in
30804 more detail. If the option @code{--no-frame-filters} is supplied, then
30805 Python frame filters will not be executed.
30807 If the @code{--skip-unavailable} option is specified, local variables
30808 that are not available are not listed. Partially available local
30809 variables are still displayed, however.
30811 This command is deprecated in favor of the
30812 @samp{-stack-list-variables} command.
30814 @subsubheading @value{GDBN} Command
30816 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30818 @subsubheading Example
30822 -stack-list-locals 0
30823 ^done,locals=[name="A",name="B",name="C"]
30825 -stack-list-locals --all-values
30826 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30827 @{name="C",value="@{1, 2, 3@}"@}]
30828 -stack-list-locals --simple-values
30829 ^done,locals=[@{name="A",type="int",value="1"@},
30830 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30834 @anchor{-stack-list-variables}
30835 @subheading The @code{-stack-list-variables} Command
30836 @findex -stack-list-variables
30838 @subsubheading Synopsis
30841 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30844 Display the names of local variables and function arguments for the selected frame. If
30845 @var{print-values} is 0 or @code{--no-values}, print only the names of
30846 the variables; if it is 1 or @code{--all-values}, print also their
30847 values; and if it is 2 or @code{--simple-values}, print the name,
30848 type and value for simple data types, and the name and type for arrays,
30849 structures and unions. If the option @code{--no-frame-filters} is
30850 supplied, then Python frame filters will not be executed.
30852 If the @code{--skip-unavailable} option is specified, local variables
30853 and arguments that are not available are not listed. Partially
30854 available arguments and local variables are still displayed, however.
30856 @subsubheading Example
30860 -stack-list-variables --thread 1 --frame 0 --all-values
30861 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30866 @subheading The @code{-stack-select-frame} Command
30867 @findex -stack-select-frame
30869 @subsubheading Synopsis
30872 -stack-select-frame @var{framenum}
30875 Change the selected frame. Select a different frame @var{framenum} on
30878 This command in deprecated in favor of passing the @samp{--frame}
30879 option to every command.
30881 @subsubheading @value{GDBN} Command
30883 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30884 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30886 @subsubheading Example
30890 -stack-select-frame 2
30895 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30896 @node GDB/MI Variable Objects
30897 @section @sc{gdb/mi} Variable Objects
30901 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30903 For the implementation of a variable debugger window (locals, watched
30904 expressions, etc.), we are proposing the adaptation of the existing code
30905 used by @code{Insight}.
30907 The two main reasons for that are:
30911 It has been proven in practice (it is already on its second generation).
30914 It will shorten development time (needless to say how important it is
30918 The original interface was designed to be used by Tcl code, so it was
30919 slightly changed so it could be used through @sc{gdb/mi}. This section
30920 describes the @sc{gdb/mi} operations that will be available and gives some
30921 hints about their use.
30923 @emph{Note}: In addition to the set of operations described here, we
30924 expect the @sc{gui} implementation of a variable window to require, at
30925 least, the following operations:
30928 @item @code{-gdb-show} @code{output-radix}
30929 @item @code{-stack-list-arguments}
30930 @item @code{-stack-list-locals}
30931 @item @code{-stack-select-frame}
30936 @subheading Introduction to Variable Objects
30938 @cindex variable objects in @sc{gdb/mi}
30940 Variable objects are "object-oriented" MI interface for examining and
30941 changing values of expressions. Unlike some other MI interfaces that
30942 work with expressions, variable objects are specifically designed for
30943 simple and efficient presentation in the frontend. A variable object
30944 is identified by string name. When a variable object is created, the
30945 frontend specifies the expression for that variable object. The
30946 expression can be a simple variable, or it can be an arbitrary complex
30947 expression, and can even involve CPU registers. After creating a
30948 variable object, the frontend can invoke other variable object
30949 operations---for example to obtain or change the value of a variable
30950 object, or to change display format.
30952 Variable objects have hierarchical tree structure. Any variable object
30953 that corresponds to a composite type, such as structure in C, has
30954 a number of child variable objects, for example corresponding to each
30955 element of a structure. A child variable object can itself have
30956 children, recursively. Recursion ends when we reach
30957 leaf variable objects, which always have built-in types. Child variable
30958 objects are created only by explicit request, so if a frontend
30959 is not interested in the children of a particular variable object, no
30960 child will be created.
30962 For a leaf variable object it is possible to obtain its value as a
30963 string, or set the value from a string. String value can be also
30964 obtained for a non-leaf variable object, but it's generally a string
30965 that only indicates the type of the object, and does not list its
30966 contents. Assignment to a non-leaf variable object is not allowed.
30968 A frontend does not need to read the values of all variable objects each time
30969 the program stops. Instead, MI provides an update command that lists all
30970 variable objects whose values has changed since the last update
30971 operation. This considerably reduces the amount of data that must
30972 be transferred to the frontend. As noted above, children variable
30973 objects are created on demand, and only leaf variable objects have a
30974 real value. As result, gdb will read target memory only for leaf
30975 variables that frontend has created.
30977 The automatic update is not always desirable. For example, a frontend
30978 might want to keep a value of some expression for future reference,
30979 and never update it. For another example, fetching memory is
30980 relatively slow for embedded targets, so a frontend might want
30981 to disable automatic update for the variables that are either not
30982 visible on the screen, or ``closed''. This is possible using so
30983 called ``frozen variable objects''. Such variable objects are never
30984 implicitly updated.
30986 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30987 fixed variable object, the expression is parsed when the variable
30988 object is created, including associating identifiers to specific
30989 variables. The meaning of expression never changes. For a floating
30990 variable object the values of variables whose names appear in the
30991 expressions are re-evaluated every time in the context of the current
30992 frame. Consider this example:
30997 struct work_state state;
31004 If a fixed variable object for the @code{state} variable is created in
31005 this function, and we enter the recursive call, the variable
31006 object will report the value of @code{state} in the top-level
31007 @code{do_work} invocation. On the other hand, a floating variable
31008 object will report the value of @code{state} in the current frame.
31010 If an expression specified when creating a fixed variable object
31011 refers to a local variable, the variable object becomes bound to the
31012 thread and frame in which the variable object is created. When such
31013 variable object is updated, @value{GDBN} makes sure that the
31014 thread/frame combination the variable object is bound to still exists,
31015 and re-evaluates the variable object in context of that thread/frame.
31017 The following is the complete set of @sc{gdb/mi} operations defined to
31018 access this functionality:
31020 @multitable @columnfractions .4 .6
31021 @item @strong{Operation}
31022 @tab @strong{Description}
31024 @item @code{-enable-pretty-printing}
31025 @tab enable Python-based pretty-printing
31026 @item @code{-var-create}
31027 @tab create a variable object
31028 @item @code{-var-delete}
31029 @tab delete the variable object and/or its children
31030 @item @code{-var-set-format}
31031 @tab set the display format of this variable
31032 @item @code{-var-show-format}
31033 @tab show the display format of this variable
31034 @item @code{-var-info-num-children}
31035 @tab tells how many children this object has
31036 @item @code{-var-list-children}
31037 @tab return a list of the object's children
31038 @item @code{-var-info-type}
31039 @tab show the type of this variable object
31040 @item @code{-var-info-expression}
31041 @tab print parent-relative expression that this variable object represents
31042 @item @code{-var-info-path-expression}
31043 @tab print full expression that this variable object represents
31044 @item @code{-var-show-attributes}
31045 @tab is this variable editable? does it exist here?
31046 @item @code{-var-evaluate-expression}
31047 @tab get the value of this variable
31048 @item @code{-var-assign}
31049 @tab set the value of this variable
31050 @item @code{-var-update}
31051 @tab update the variable and its children
31052 @item @code{-var-set-frozen}
31053 @tab set frozeness attribute
31054 @item @code{-var-set-update-range}
31055 @tab set range of children to display on update
31058 In the next subsection we describe each operation in detail and suggest
31059 how it can be used.
31061 @subheading Description And Use of Operations on Variable Objects
31063 @subheading The @code{-enable-pretty-printing} Command
31064 @findex -enable-pretty-printing
31067 -enable-pretty-printing
31070 @value{GDBN} allows Python-based visualizers to affect the output of the
31071 MI variable object commands. However, because there was no way to
31072 implement this in a fully backward-compatible way, a front end must
31073 request that this functionality be enabled.
31075 Once enabled, this feature cannot be disabled.
31077 Note that if Python support has not been compiled into @value{GDBN},
31078 this command will still succeed (and do nothing).
31080 This feature is currently (as of @value{GDBN} 7.0) experimental, and
31081 may work differently in future versions of @value{GDBN}.
31083 @subheading The @code{-var-create} Command
31084 @findex -var-create
31086 @subsubheading Synopsis
31089 -var-create @{@var{name} | "-"@}
31090 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
31093 This operation creates a variable object, which allows the monitoring of
31094 a variable, the result of an expression, a memory cell or a CPU
31097 The @var{name} parameter is the string by which the object can be
31098 referenced. It must be unique. If @samp{-} is specified, the varobj
31099 system will generate a string ``varNNNNNN'' automatically. It will be
31100 unique provided that one does not specify @var{name} of that format.
31101 The command fails if a duplicate name is found.
31103 The frame under which the expression should be evaluated can be
31104 specified by @var{frame-addr}. A @samp{*} indicates that the current
31105 frame should be used. A @samp{@@} indicates that a floating variable
31106 object must be created.
31108 @var{expression} is any expression valid on the current language set (must not
31109 begin with a @samp{*}), or one of the following:
31113 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
31116 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
31119 @samp{$@var{regname}} --- a CPU register name
31122 @cindex dynamic varobj
31123 A varobj's contents may be provided by a Python-based pretty-printer. In this
31124 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
31125 have slightly different semantics in some cases. If the
31126 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
31127 will never create a dynamic varobj. This ensures backward
31128 compatibility for existing clients.
31130 @subsubheading Result
31132 This operation returns attributes of the newly-created varobj. These
31137 The name of the varobj.
31140 The number of children of the varobj. This number is not necessarily
31141 reliable for a dynamic varobj. Instead, you must examine the
31142 @samp{has_more} attribute.
31145 The varobj's scalar value. For a varobj whose type is some sort of
31146 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
31147 will not be interesting.
31150 The varobj's type. This is a string representation of the type, as
31151 would be printed by the @value{GDBN} CLI. If @samp{print object}
31152 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31153 @emph{actual} (derived) type of the object is shown rather than the
31154 @emph{declared} one.
31157 If a variable object is bound to a specific thread, then this is the
31158 thread's global identifier.
31161 For a dynamic varobj, this indicates whether there appear to be any
31162 children available. For a non-dynamic varobj, this will be 0.
31165 This attribute will be present and have the value @samp{1} if the
31166 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31167 then this attribute will not be present.
31170 A dynamic varobj can supply a display hint to the front end. The
31171 value comes directly from the Python pretty-printer object's
31172 @code{display_hint} method. @xref{Pretty Printing API}.
31175 Typical output will look like this:
31178 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
31179 has_more="@var{has_more}"
31183 @subheading The @code{-var-delete} Command
31184 @findex -var-delete
31186 @subsubheading Synopsis
31189 -var-delete [ -c ] @var{name}
31192 Deletes a previously created variable object and all of its children.
31193 With the @samp{-c} option, just deletes the children.
31195 Returns an error if the object @var{name} is not found.
31198 @subheading The @code{-var-set-format} Command
31199 @findex -var-set-format
31201 @subsubheading Synopsis
31204 -var-set-format @var{name} @var{format-spec}
31207 Sets the output format for the value of the object @var{name} to be
31210 @anchor{-var-set-format}
31211 The syntax for the @var{format-spec} is as follows:
31214 @var{format-spec} @expansion{}
31215 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
31218 The natural format is the default format choosen automatically
31219 based on the variable type (like decimal for an @code{int}, hex
31220 for pointers, etc.).
31222 The zero-hexadecimal format has a representation similar to hexadecimal
31223 but with padding zeroes to the left of the value. For example, a 32-bit
31224 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
31225 zero-hexadecimal format.
31227 For a variable with children, the format is set only on the
31228 variable itself, and the children are not affected.
31230 @subheading The @code{-var-show-format} Command
31231 @findex -var-show-format
31233 @subsubheading Synopsis
31236 -var-show-format @var{name}
31239 Returns the format used to display the value of the object @var{name}.
31242 @var{format} @expansion{}
31247 @subheading The @code{-var-info-num-children} Command
31248 @findex -var-info-num-children
31250 @subsubheading Synopsis
31253 -var-info-num-children @var{name}
31256 Returns the number of children of a variable object @var{name}:
31262 Note that this number is not completely reliable for a dynamic varobj.
31263 It will return the current number of children, but more children may
31267 @subheading The @code{-var-list-children} Command
31268 @findex -var-list-children
31270 @subsubheading Synopsis
31273 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
31275 @anchor{-var-list-children}
31277 Return a list of the children of the specified variable object and
31278 create variable objects for them, if they do not already exist. With
31279 a single argument or if @var{print-values} has a value of 0 or
31280 @code{--no-values}, print only the names of the variables; if
31281 @var{print-values} is 1 or @code{--all-values}, also print their
31282 values; and if it is 2 or @code{--simple-values} print the name and
31283 value for simple data types and just the name for arrays, structures
31286 @var{from} and @var{to}, if specified, indicate the range of children
31287 to report. If @var{from} or @var{to} is less than zero, the range is
31288 reset and all children will be reported. Otherwise, children starting
31289 at @var{from} (zero-based) and up to and excluding @var{to} will be
31292 If a child range is requested, it will only affect the current call to
31293 @code{-var-list-children}, but not future calls to @code{-var-update}.
31294 For this, you must instead use @code{-var-set-update-range}. The
31295 intent of this approach is to enable a front end to implement any
31296 update approach it likes; for example, scrolling a view may cause the
31297 front end to request more children with @code{-var-list-children}, and
31298 then the front end could call @code{-var-set-update-range} with a
31299 different range to ensure that future updates are restricted to just
31302 For each child the following results are returned:
31307 Name of the variable object created for this child.
31310 The expression to be shown to the user by the front end to designate this child.
31311 For example this may be the name of a structure member.
31313 For a dynamic varobj, this value cannot be used to form an
31314 expression. There is no way to do this at all with a dynamic varobj.
31316 For C/C@t{++} structures there are several pseudo children returned to
31317 designate access qualifiers. For these pseudo children @var{exp} is
31318 @samp{public}, @samp{private}, or @samp{protected}. In this case the
31319 type and value are not present.
31321 A dynamic varobj will not report the access qualifying
31322 pseudo-children, regardless of the language. This information is not
31323 available at all with a dynamic varobj.
31326 Number of children this child has. For a dynamic varobj, this will be
31330 The type of the child. If @samp{print object}
31331 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31332 @emph{actual} (derived) type of the object is shown rather than the
31333 @emph{declared} one.
31336 If values were requested, this is the value.
31339 If this variable object is associated with a thread, this is the
31340 thread's global thread id. Otherwise this result is not present.
31343 If the variable object is frozen, this variable will be present with a value of 1.
31346 A dynamic varobj can supply a display hint to the front end. The
31347 value comes directly from the Python pretty-printer object's
31348 @code{display_hint} method. @xref{Pretty Printing API}.
31351 This attribute will be present and have the value @samp{1} if the
31352 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31353 then this attribute will not be present.
31357 The result may have its own attributes:
31361 A dynamic varobj can supply a display hint to the front end. The
31362 value comes directly from the Python pretty-printer object's
31363 @code{display_hint} method. @xref{Pretty Printing API}.
31366 This is an integer attribute which is nonzero if there are children
31367 remaining after the end of the selected range.
31370 @subsubheading Example
31374 -var-list-children n
31375 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
31376 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
31378 -var-list-children --all-values n
31379 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
31380 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
31384 @subheading The @code{-var-info-type} Command
31385 @findex -var-info-type
31387 @subsubheading Synopsis
31390 -var-info-type @var{name}
31393 Returns the type of the specified variable @var{name}. The type is
31394 returned as a string in the same format as it is output by the
31398 type=@var{typename}
31402 @subheading The @code{-var-info-expression} Command
31403 @findex -var-info-expression
31405 @subsubheading Synopsis
31408 -var-info-expression @var{name}
31411 Returns a string that is suitable for presenting this
31412 variable object in user interface. The string is generally
31413 not valid expression in the current language, and cannot be evaluated.
31415 For example, if @code{a} is an array, and variable object
31416 @code{A} was created for @code{a}, then we'll get this output:
31419 (gdb) -var-info-expression A.1
31420 ^done,lang="C",exp="1"
31424 Here, the value of @code{lang} is the language name, which can be
31425 found in @ref{Supported Languages}.
31427 Note that the output of the @code{-var-list-children} command also
31428 includes those expressions, so the @code{-var-info-expression} command
31431 @subheading The @code{-var-info-path-expression} Command
31432 @findex -var-info-path-expression
31434 @subsubheading Synopsis
31437 -var-info-path-expression @var{name}
31440 Returns an expression that can be evaluated in the current
31441 context and will yield the same value that a variable object has.
31442 Compare this with the @code{-var-info-expression} command, which
31443 result can be used only for UI presentation. Typical use of
31444 the @code{-var-info-path-expression} command is creating a
31445 watchpoint from a variable object.
31447 This command is currently not valid for children of a dynamic varobj,
31448 and will give an error when invoked on one.
31450 For example, suppose @code{C} is a C@t{++} class, derived from class
31451 @code{Base}, and that the @code{Base} class has a member called
31452 @code{m_size}. Assume a variable @code{c} is has the type of
31453 @code{C} and a variable object @code{C} was created for variable
31454 @code{c}. Then, we'll get this output:
31456 (gdb) -var-info-path-expression C.Base.public.m_size
31457 ^done,path_expr=((Base)c).m_size)
31460 @subheading The @code{-var-show-attributes} Command
31461 @findex -var-show-attributes
31463 @subsubheading Synopsis
31466 -var-show-attributes @var{name}
31469 List attributes of the specified variable object @var{name}:
31472 status=@var{attr} [ ( ,@var{attr} )* ]
31476 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
31478 @subheading The @code{-var-evaluate-expression} Command
31479 @findex -var-evaluate-expression
31481 @subsubheading Synopsis
31484 -var-evaluate-expression [-f @var{format-spec}] @var{name}
31487 Evaluates the expression that is represented by the specified variable
31488 object and returns its value as a string. The format of the string
31489 can be specified with the @samp{-f} option. The possible values of
31490 this option are the same as for @code{-var-set-format}
31491 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
31492 the current display format will be used. The current display format
31493 can be changed using the @code{-var-set-format} command.
31499 Note that one must invoke @code{-var-list-children} for a variable
31500 before the value of a child variable can be evaluated.
31502 @subheading The @code{-var-assign} Command
31503 @findex -var-assign
31505 @subsubheading Synopsis
31508 -var-assign @var{name} @var{expression}
31511 Assigns the value of @var{expression} to the variable object specified
31512 by @var{name}. The object must be @samp{editable}. If the variable's
31513 value is altered by the assign, the variable will show up in any
31514 subsequent @code{-var-update} list.
31516 @subsubheading Example
31524 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
31528 @subheading The @code{-var-update} Command
31529 @findex -var-update
31531 @subsubheading Synopsis
31534 -var-update [@var{print-values}] @{@var{name} | "*"@}
31537 Reevaluate the expressions corresponding to the variable object
31538 @var{name} and all its direct and indirect children, and return the
31539 list of variable objects whose values have changed; @var{name} must
31540 be a root variable object. Here, ``changed'' means that the result of
31541 @code{-var-evaluate-expression} before and after the
31542 @code{-var-update} is different. If @samp{*} is used as the variable
31543 object names, all existing variable objects are updated, except
31544 for frozen ones (@pxref{-var-set-frozen}). The option
31545 @var{print-values} determines whether both names and values, or just
31546 names are printed. The possible values of this option are the same
31547 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
31548 recommended to use the @samp{--all-values} option, to reduce the
31549 number of MI commands needed on each program stop.
31551 With the @samp{*} parameter, if a variable object is bound to a
31552 currently running thread, it will not be updated, without any
31555 If @code{-var-set-update-range} was previously used on a varobj, then
31556 only the selected range of children will be reported.
31558 @code{-var-update} reports all the changed varobjs in a tuple named
31561 Each item in the change list is itself a tuple holding:
31565 The name of the varobj.
31568 If values were requested for this update, then this field will be
31569 present and will hold the value of the varobj.
31572 @anchor{-var-update}
31573 This field is a string which may take one of three values:
31577 The variable object's current value is valid.
31580 The variable object does not currently hold a valid value but it may
31581 hold one in the future if its associated expression comes back into
31585 The variable object no longer holds a valid value.
31586 This can occur when the executable file being debugged has changed,
31587 either through recompilation or by using the @value{GDBN} @code{file}
31588 command. The front end should normally choose to delete these variable
31592 In the future new values may be added to this list so the front should
31593 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31596 This is only present if the varobj is still valid. If the type
31597 changed, then this will be the string @samp{true}; otherwise it will
31600 When a varobj's type changes, its children are also likely to have
31601 become incorrect. Therefore, the varobj's children are automatically
31602 deleted when this attribute is @samp{true}. Also, the varobj's update
31603 range, when set using the @code{-var-set-update-range} command, is
31607 If the varobj's type changed, then this field will be present and will
31610 @item new_num_children
31611 For a dynamic varobj, if the number of children changed, or if the
31612 type changed, this will be the new number of children.
31614 The @samp{numchild} field in other varobj responses is generally not
31615 valid for a dynamic varobj -- it will show the number of children that
31616 @value{GDBN} knows about, but because dynamic varobjs lazily
31617 instantiate their children, this will not reflect the number of
31618 children which may be available.
31620 The @samp{new_num_children} attribute only reports changes to the
31621 number of children known by @value{GDBN}. This is the only way to
31622 detect whether an update has removed children (which necessarily can
31623 only happen at the end of the update range).
31626 The display hint, if any.
31629 This is an integer value, which will be 1 if there are more children
31630 available outside the varobj's update range.
31633 This attribute will be present and have the value @samp{1} if the
31634 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31635 then this attribute will not be present.
31638 If new children were added to a dynamic varobj within the selected
31639 update range (as set by @code{-var-set-update-range}), then they will
31640 be listed in this attribute.
31643 @subsubheading Example
31650 -var-update --all-values var1
31651 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31652 type_changed="false"@}]
31656 @subheading The @code{-var-set-frozen} Command
31657 @findex -var-set-frozen
31658 @anchor{-var-set-frozen}
31660 @subsubheading Synopsis
31663 -var-set-frozen @var{name} @var{flag}
31666 Set the frozenness flag on the variable object @var{name}. The
31667 @var{flag} parameter should be either @samp{1} to make the variable
31668 frozen or @samp{0} to make it unfrozen. If a variable object is
31669 frozen, then neither itself, nor any of its children, are
31670 implicitly updated by @code{-var-update} of
31671 a parent variable or by @code{-var-update *}. Only
31672 @code{-var-update} of the variable itself will update its value and
31673 values of its children. After a variable object is unfrozen, it is
31674 implicitly updated by all subsequent @code{-var-update} operations.
31675 Unfreezing a variable does not update it, only subsequent
31676 @code{-var-update} does.
31678 @subsubheading Example
31682 -var-set-frozen V 1
31687 @subheading The @code{-var-set-update-range} command
31688 @findex -var-set-update-range
31689 @anchor{-var-set-update-range}
31691 @subsubheading Synopsis
31694 -var-set-update-range @var{name} @var{from} @var{to}
31697 Set the range of children to be returned by future invocations of
31698 @code{-var-update}.
31700 @var{from} and @var{to} indicate the range of children to report. If
31701 @var{from} or @var{to} is less than zero, the range is reset and all
31702 children will be reported. Otherwise, children starting at @var{from}
31703 (zero-based) and up to and excluding @var{to} will be reported.
31705 @subsubheading Example
31709 -var-set-update-range V 1 2
31713 @subheading The @code{-var-set-visualizer} command
31714 @findex -var-set-visualizer
31715 @anchor{-var-set-visualizer}
31717 @subsubheading Synopsis
31720 -var-set-visualizer @var{name} @var{visualizer}
31723 Set a visualizer for the variable object @var{name}.
31725 @var{visualizer} is the visualizer to use. The special value
31726 @samp{None} means to disable any visualizer in use.
31728 If not @samp{None}, @var{visualizer} must be a Python expression.
31729 This expression must evaluate to a callable object which accepts a
31730 single argument. @value{GDBN} will call this object with the value of
31731 the varobj @var{name} as an argument (this is done so that the same
31732 Python pretty-printing code can be used for both the CLI and MI).
31733 When called, this object must return an object which conforms to the
31734 pretty-printing interface (@pxref{Pretty Printing API}).
31736 The pre-defined function @code{gdb.default_visualizer} may be used to
31737 select a visualizer by following the built-in process
31738 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31739 a varobj is created, and so ordinarily is not needed.
31741 This feature is only available if Python support is enabled. The MI
31742 command @code{-list-features} (@pxref{GDB/MI Support Commands})
31743 can be used to check this.
31745 @subsubheading Example
31747 Resetting the visualizer:
31751 -var-set-visualizer V None
31755 Reselecting the default (type-based) visualizer:
31759 -var-set-visualizer V gdb.default_visualizer
31763 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31764 can be used to instantiate this class for a varobj:
31768 -var-set-visualizer V "lambda val: SomeClass()"
31772 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31773 @node GDB/MI Data Manipulation
31774 @section @sc{gdb/mi} Data Manipulation
31776 @cindex data manipulation, in @sc{gdb/mi}
31777 @cindex @sc{gdb/mi}, data manipulation
31778 This section describes the @sc{gdb/mi} commands that manipulate data:
31779 examine memory and registers, evaluate expressions, etc.
31781 For details about what an addressable memory unit is,
31782 @pxref{addressable memory unit}.
31784 @c REMOVED FROM THE INTERFACE.
31785 @c @subheading -data-assign
31786 @c Change the value of a program variable. Plenty of side effects.
31787 @c @subsubheading GDB Command
31789 @c @subsubheading Example
31792 @subheading The @code{-data-disassemble} Command
31793 @findex -data-disassemble
31795 @subsubheading Synopsis
31799 [ -s @var{start-addr} -e @var{end-addr} ]
31800 | [ -a @var{addr} ]
31801 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31809 @item @var{start-addr}
31810 is the beginning address (or @code{$pc})
31811 @item @var{end-addr}
31814 is an address anywhere within (or the name of) the function to
31815 disassemble. If an address is specified, the whole function
31816 surrounding that address will be disassembled. If a name is
31817 specified, the whole function with that name will be disassembled.
31818 @item @var{filename}
31819 is the name of the file to disassemble
31820 @item @var{linenum}
31821 is the line number to disassemble around
31823 is the number of disassembly lines to be produced. If it is -1,
31824 the whole function will be disassembled, in case no @var{end-addr} is
31825 specified. If @var{end-addr} is specified as a non-zero value, and
31826 @var{lines} is lower than the number of disassembly lines between
31827 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31828 displayed; if @var{lines} is higher than the number of lines between
31829 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31834 @item 0 disassembly only
31835 @item 1 mixed source and disassembly (deprecated)
31836 @item 2 disassembly with raw opcodes
31837 @item 3 mixed source and disassembly with raw opcodes (deprecated)
31838 @item 4 mixed source and disassembly
31839 @item 5 mixed source and disassembly with raw opcodes
31842 Modes 1 and 3 are deprecated. The output is ``source centric''
31843 which hasn't proved useful in practice.
31844 @xref{Machine Code}, for a discussion of the difference between
31845 @code{/m} and @code{/s} output of the @code{disassemble} command.
31848 @subsubheading Result
31850 The result of the @code{-data-disassemble} command will be a list named
31851 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31852 used with the @code{-data-disassemble} command.
31854 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31859 The address at which this instruction was disassembled.
31862 The name of the function this instruction is within.
31865 The decimal offset in bytes from the start of @samp{func-name}.
31868 The text disassembly for this @samp{address}.
31871 This field is only present for modes 2, 3 and 5. This contains the raw opcode
31872 bytes for the @samp{inst} field.
31876 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
31877 @samp{src_and_asm_line}, each of which has the following fields:
31881 The line number within @samp{file}.
31884 The file name from the compilation unit. This might be an absolute
31885 file name or a relative file name depending on the compile command
31889 Absolute file name of @samp{file}. It is converted to a canonical form
31890 using the source file search path
31891 (@pxref{Source Path, ,Specifying Source Directories})
31892 and after resolving all the symbolic links.
31894 If the source file is not found this field will contain the path as
31895 present in the debug information.
31897 @item line_asm_insn
31898 This is a list of tuples containing the disassembly for @samp{line} in
31899 @samp{file}. The fields of each tuple are the same as for
31900 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31901 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31906 Note that whatever included in the @samp{inst} field, is not
31907 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31910 @subsubheading @value{GDBN} Command
31912 The corresponding @value{GDBN} command is @samp{disassemble}.
31914 @subsubheading Example
31916 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31920 -data-disassemble -s $pc -e "$pc + 20" -- 0
31923 @{address="0x000107c0",func-name="main",offset="4",
31924 inst="mov 2, %o0"@},
31925 @{address="0x000107c4",func-name="main",offset="8",
31926 inst="sethi %hi(0x11800), %o2"@},
31927 @{address="0x000107c8",func-name="main",offset="12",
31928 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31929 @{address="0x000107cc",func-name="main",offset="16",
31930 inst="sethi %hi(0x11800), %o2"@},
31931 @{address="0x000107d0",func-name="main",offset="20",
31932 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31936 Disassemble the whole @code{main} function. Line 32 is part of
31940 -data-disassemble -f basics.c -l 32 -- 0
31942 @{address="0x000107bc",func-name="main",offset="0",
31943 inst="save %sp, -112, %sp"@},
31944 @{address="0x000107c0",func-name="main",offset="4",
31945 inst="mov 2, %o0"@},
31946 @{address="0x000107c4",func-name="main",offset="8",
31947 inst="sethi %hi(0x11800), %o2"@},
31949 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31950 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31954 Disassemble 3 instructions from the start of @code{main}:
31958 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31960 @{address="0x000107bc",func-name="main",offset="0",
31961 inst="save %sp, -112, %sp"@},
31962 @{address="0x000107c0",func-name="main",offset="4",
31963 inst="mov 2, %o0"@},
31964 @{address="0x000107c4",func-name="main",offset="8",
31965 inst="sethi %hi(0x11800), %o2"@}]
31969 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31973 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31975 src_and_asm_line=@{line="31",
31976 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31977 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31978 line_asm_insn=[@{address="0x000107bc",
31979 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31980 src_and_asm_line=@{line="32",
31981 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31982 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31983 line_asm_insn=[@{address="0x000107c0",
31984 func-name="main",offset="4",inst="mov 2, %o0"@},
31985 @{address="0x000107c4",func-name="main",offset="8",
31986 inst="sethi %hi(0x11800), %o2"@}]@}]
31991 @subheading The @code{-data-evaluate-expression} Command
31992 @findex -data-evaluate-expression
31994 @subsubheading Synopsis
31997 -data-evaluate-expression @var{expr}
32000 Evaluate @var{expr} as an expression. The expression could contain an
32001 inferior function call. The function call will execute synchronously.
32002 If the expression contains spaces, it must be enclosed in double quotes.
32004 @subsubheading @value{GDBN} Command
32006 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
32007 @samp{call}. In @code{gdbtk} only, there's a corresponding
32008 @samp{gdb_eval} command.
32010 @subsubheading Example
32012 In the following example, the numbers that precede the commands are the
32013 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
32014 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
32018 211-data-evaluate-expression A
32021 311-data-evaluate-expression &A
32022 311^done,value="0xefffeb7c"
32024 411-data-evaluate-expression A+3
32027 511-data-evaluate-expression "A + 3"
32033 @subheading The @code{-data-list-changed-registers} Command
32034 @findex -data-list-changed-registers
32036 @subsubheading Synopsis
32039 -data-list-changed-registers
32042 Display a list of the registers that have changed.
32044 @subsubheading @value{GDBN} Command
32046 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
32047 has the corresponding command @samp{gdb_changed_register_list}.
32049 @subsubheading Example
32051 On a PPC MBX board:
32059 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
32060 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
32061 line="5",arch="powerpc"@}
32063 -data-list-changed-registers
32064 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
32065 "10","11","13","14","15","16","17","18","19","20","21","22","23",
32066 "24","25","26","27","28","30","31","64","65","66","67","69"]
32071 @subheading The @code{-data-list-register-names} Command
32072 @findex -data-list-register-names
32074 @subsubheading Synopsis
32077 -data-list-register-names [ ( @var{regno} )+ ]
32080 Show a list of register names for the current target. If no arguments
32081 are given, it shows a list of the names of all the registers. If
32082 integer numbers are given as arguments, it will print a list of the
32083 names of the registers corresponding to the arguments. To ensure
32084 consistency between a register name and its number, the output list may
32085 include empty register names.
32087 @subsubheading @value{GDBN} Command
32089 @value{GDBN} does not have a command which corresponds to
32090 @samp{-data-list-register-names}. In @code{gdbtk} there is a
32091 corresponding command @samp{gdb_regnames}.
32093 @subsubheading Example
32095 For the PPC MBX board:
32098 -data-list-register-names
32099 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
32100 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
32101 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
32102 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
32103 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
32104 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
32105 "", "pc","ps","cr","lr","ctr","xer"]
32107 -data-list-register-names 1 2 3
32108 ^done,register-names=["r1","r2","r3"]
32112 @subheading The @code{-data-list-register-values} Command
32113 @findex -data-list-register-values
32115 @subsubheading Synopsis
32118 -data-list-register-values
32119 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
32122 Display the registers' contents. The format according to which the
32123 registers' contents are to be returned is given by @var{fmt}, followed
32124 by an optional list of numbers specifying the registers to display. A
32125 missing list of numbers indicates that the contents of all the
32126 registers must be returned. The @code{--skip-unavailable} option
32127 indicates that only the available registers are to be returned.
32129 Allowed formats for @var{fmt} are:
32146 @subsubheading @value{GDBN} Command
32148 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
32149 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
32151 @subsubheading Example
32153 For a PPC MBX board (note: line breaks are for readability only, they
32154 don't appear in the actual output):
32158 -data-list-register-values r 64 65
32159 ^done,register-values=[@{number="64",value="0xfe00a300"@},
32160 @{number="65",value="0x00029002"@}]
32162 -data-list-register-values x
32163 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
32164 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
32165 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
32166 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
32167 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
32168 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
32169 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
32170 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
32171 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
32172 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
32173 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
32174 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
32175 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
32176 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
32177 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
32178 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
32179 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
32180 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
32181 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
32182 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
32183 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
32184 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
32185 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
32186 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
32187 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
32188 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
32189 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
32190 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
32191 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
32192 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
32193 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
32194 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
32195 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
32196 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
32197 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
32198 @{number="69",value="0x20002b03"@}]
32203 @subheading The @code{-data-read-memory} Command
32204 @findex -data-read-memory
32206 This command is deprecated, use @code{-data-read-memory-bytes} instead.
32208 @subsubheading Synopsis
32211 -data-read-memory [ -o @var{byte-offset} ]
32212 @var{address} @var{word-format} @var{word-size}
32213 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
32220 @item @var{address}
32221 An expression specifying the address of the first memory word to be
32222 read. Complex expressions containing embedded white space should be
32223 quoted using the C convention.
32225 @item @var{word-format}
32226 The format to be used to print the memory words. The notation is the
32227 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
32230 @item @var{word-size}
32231 The size of each memory word in bytes.
32233 @item @var{nr-rows}
32234 The number of rows in the output table.
32236 @item @var{nr-cols}
32237 The number of columns in the output table.
32240 If present, indicates that each row should include an @sc{ascii} dump. The
32241 value of @var{aschar} is used as a padding character when a byte is not a
32242 member of the printable @sc{ascii} character set (printable @sc{ascii}
32243 characters are those whose code is between 32 and 126, inclusively).
32245 @item @var{byte-offset}
32246 An offset to add to the @var{address} before fetching memory.
32249 This command displays memory contents as a table of @var{nr-rows} by
32250 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
32251 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
32252 (returned as @samp{total-bytes}). Should less than the requested number
32253 of bytes be returned by the target, the missing words are identified
32254 using @samp{N/A}. The number of bytes read from the target is returned
32255 in @samp{nr-bytes} and the starting address used to read memory in
32258 The address of the next/previous row or page is available in
32259 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
32262 @subsubheading @value{GDBN} Command
32264 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
32265 @samp{gdb_get_mem} memory read command.
32267 @subsubheading Example
32269 Read six bytes of memory starting at @code{bytes+6} but then offset by
32270 @code{-6} bytes. Format as three rows of two columns. One byte per
32271 word. Display each word in hex.
32275 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
32276 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
32277 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
32278 prev-page="0x0000138a",memory=[
32279 @{addr="0x00001390",data=["0x00","0x01"]@},
32280 @{addr="0x00001392",data=["0x02","0x03"]@},
32281 @{addr="0x00001394",data=["0x04","0x05"]@}]
32285 Read two bytes of memory starting at address @code{shorts + 64} and
32286 display as a single word formatted in decimal.
32290 5-data-read-memory shorts+64 d 2 1 1
32291 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
32292 next-row="0x00001512",prev-row="0x0000150e",
32293 next-page="0x00001512",prev-page="0x0000150e",memory=[
32294 @{addr="0x00001510",data=["128"]@}]
32298 Read thirty two bytes of memory starting at @code{bytes+16} and format
32299 as eight rows of four columns. Include a string encoding with @samp{x}
32300 used as the non-printable character.
32304 4-data-read-memory bytes+16 x 1 8 4 x
32305 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
32306 next-row="0x000013c0",prev-row="0x0000139c",
32307 next-page="0x000013c0",prev-page="0x00001380",memory=[
32308 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
32309 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
32310 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
32311 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
32312 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
32313 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
32314 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
32315 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
32319 @subheading The @code{-data-read-memory-bytes} Command
32320 @findex -data-read-memory-bytes
32322 @subsubheading Synopsis
32325 -data-read-memory-bytes [ -o @var{offset} ]
32326 @var{address} @var{count}
32333 @item @var{address}
32334 An expression specifying the address of the first addressable memory unit
32335 to be read. Complex expressions containing embedded white space should be
32336 quoted using the C convention.
32339 The number of addressable memory units to read. This should be an integer
32343 The offset relative to @var{address} at which to start reading. This
32344 should be an integer literal. This option is provided so that a frontend
32345 is not required to first evaluate address and then perform address
32346 arithmetics itself.
32350 This command attempts to read all accessible memory regions in the
32351 specified range. First, all regions marked as unreadable in the memory
32352 map (if one is defined) will be skipped. @xref{Memory Region
32353 Attributes}. Second, @value{GDBN} will attempt to read the remaining
32354 regions. For each one, if reading full region results in an errors,
32355 @value{GDBN} will try to read a subset of the region.
32357 In general, every single memory unit in the region may be readable or not,
32358 and the only way to read every readable unit is to try a read at
32359 every address, which is not practical. Therefore, @value{GDBN} will
32360 attempt to read all accessible memory units at either beginning or the end
32361 of the region, using a binary division scheme. This heuristic works
32362 well for reading accross a memory map boundary. Note that if a region
32363 has a readable range that is neither at the beginning or the end,
32364 @value{GDBN} will not read it.
32366 The result record (@pxref{GDB/MI Result Records}) that is output of
32367 the command includes a field named @samp{memory} whose content is a
32368 list of tuples. Each tuple represent a successfully read memory block
32369 and has the following fields:
32373 The start address of the memory block, as hexadecimal literal.
32376 The end address of the memory block, as hexadecimal literal.
32379 The offset of the memory block, as hexadecimal literal, relative to
32380 the start address passed to @code{-data-read-memory-bytes}.
32383 The contents of the memory block, in hex.
32389 @subsubheading @value{GDBN} Command
32391 The corresponding @value{GDBN} command is @samp{x}.
32393 @subsubheading Example
32397 -data-read-memory-bytes &a 10
32398 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
32400 contents="01000000020000000300"@}]
32405 @subheading The @code{-data-write-memory-bytes} Command
32406 @findex -data-write-memory-bytes
32408 @subsubheading Synopsis
32411 -data-write-memory-bytes @var{address} @var{contents}
32412 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
32419 @item @var{address}
32420 An expression specifying the address of the first addressable memory unit
32421 to be written. Complex expressions containing embedded white space should
32422 be quoted using the C convention.
32424 @item @var{contents}
32425 The hex-encoded data to write. It is an error if @var{contents} does
32426 not represent an integral number of addressable memory units.
32429 Optional argument indicating the number of addressable memory units to be
32430 written. If @var{count} is greater than @var{contents}' length,
32431 @value{GDBN} will repeatedly write @var{contents} until it fills
32432 @var{count} memory units.
32436 @subsubheading @value{GDBN} Command
32438 There's no corresponding @value{GDBN} command.
32440 @subsubheading Example
32444 -data-write-memory-bytes &a "aabbccdd"
32451 -data-write-memory-bytes &a "aabbccdd" 16e
32456 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32457 @node GDB/MI Tracepoint Commands
32458 @section @sc{gdb/mi} Tracepoint Commands
32460 The commands defined in this section implement MI support for
32461 tracepoints. For detailed introduction, see @ref{Tracepoints}.
32463 @subheading The @code{-trace-find} Command
32464 @findex -trace-find
32466 @subsubheading Synopsis
32469 -trace-find @var{mode} [@var{parameters}@dots{}]
32472 Find a trace frame using criteria defined by @var{mode} and
32473 @var{parameters}. The following table lists permissible
32474 modes and their parameters. For details of operation, see @ref{tfind}.
32479 No parameters are required. Stops examining trace frames.
32482 An integer is required as parameter. Selects tracepoint frame with
32485 @item tracepoint-number
32486 An integer is required as parameter. Finds next
32487 trace frame that corresponds to tracepoint with the specified number.
32490 An address is required as parameter. Finds
32491 next trace frame that corresponds to any tracepoint at the specified
32494 @item pc-inside-range
32495 Two addresses are required as parameters. Finds next trace
32496 frame that corresponds to a tracepoint at an address inside the
32497 specified range. Both bounds are considered to be inside the range.
32499 @item pc-outside-range
32500 Two addresses are required as parameters. Finds
32501 next trace frame that corresponds to a tracepoint at an address outside
32502 the specified range. Both bounds are considered to be inside the range.
32505 Line specification is required as parameter. @xref{Specify Location}.
32506 Finds next trace frame that corresponds to a tracepoint at
32507 the specified location.
32511 If @samp{none} was passed as @var{mode}, the response does not
32512 have fields. Otherwise, the response may have the following fields:
32516 This field has either @samp{0} or @samp{1} as the value, depending
32517 on whether a matching tracepoint was found.
32520 The index of the found traceframe. This field is present iff
32521 the @samp{found} field has value of @samp{1}.
32524 The index of the found tracepoint. This field is present iff
32525 the @samp{found} field has value of @samp{1}.
32528 The information about the frame corresponding to the found trace
32529 frame. This field is present only if a trace frame was found.
32530 @xref{GDB/MI Frame Information}, for description of this field.
32534 @subsubheading @value{GDBN} Command
32536 The corresponding @value{GDBN} command is @samp{tfind}.
32538 @subheading -trace-define-variable
32539 @findex -trace-define-variable
32541 @subsubheading Synopsis
32544 -trace-define-variable @var{name} [ @var{value} ]
32547 Create trace variable @var{name} if it does not exist. If
32548 @var{value} is specified, sets the initial value of the specified
32549 trace variable to that value. Note that the @var{name} should start
32550 with the @samp{$} character.
32552 @subsubheading @value{GDBN} Command
32554 The corresponding @value{GDBN} command is @samp{tvariable}.
32556 @subheading The @code{-trace-frame-collected} Command
32557 @findex -trace-frame-collected
32559 @subsubheading Synopsis
32562 -trace-frame-collected
32563 [--var-print-values @var{var_pval}]
32564 [--comp-print-values @var{comp_pval}]
32565 [--registers-format @var{regformat}]
32566 [--memory-contents]
32569 This command returns the set of collected objects, register names,
32570 trace state variable names, memory ranges and computed expressions
32571 that have been collected at a particular trace frame. The optional
32572 parameters to the command affect the output format in different ways.
32573 See the output description table below for more details.
32575 The reported names can be used in the normal manner to create
32576 varobjs and inspect the objects themselves. The items returned by
32577 this command are categorized so that it is clear which is a variable,
32578 which is a register, which is a trace state variable, which is a
32579 memory range and which is a computed expression.
32581 For instance, if the actions were
32583 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
32584 collect *(int*)0xaf02bef0@@40
32588 the object collected in its entirety would be @code{myVar}. The
32589 object @code{myArray} would be partially collected, because only the
32590 element at index @code{myIndex} would be collected. The remaining
32591 objects would be computed expressions.
32593 An example output would be:
32597 -trace-frame-collected
32599 explicit-variables=[@{name="myVar",value="1"@}],
32600 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
32601 @{name="myObj.field",value="0"@},
32602 @{name="myPtr->field",value="1"@},
32603 @{name="myCount + 2",value="3"@},
32604 @{name="$tvar1 + 1",value="43970027"@}],
32605 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
32606 @{number="1",value="0x0"@},
32607 @{number="2",value="0x4"@},
32609 @{number="125",value="0x0"@}],
32610 tvars=[@{name="$tvar1",current="43970026"@}],
32611 memory=[@{address="0x0000000000602264",length="4"@},
32612 @{address="0x0000000000615bc0",length="4"@}]
32619 @item explicit-variables
32620 The set of objects that have been collected in their entirety (as
32621 opposed to collecting just a few elements of an array or a few struct
32622 members). For each object, its name and value are printed.
32623 The @code{--var-print-values} option affects how or whether the value
32624 field is output. If @var{var_pval} is 0, then print only the names;
32625 if it is 1, print also their values; and if it is 2, print the name,
32626 type and value for simple data types, and the name and type for
32627 arrays, structures and unions.
32629 @item computed-expressions
32630 The set of computed expressions that have been collected at the
32631 current trace frame. The @code{--comp-print-values} option affects
32632 this set like the @code{--var-print-values} option affects the
32633 @code{explicit-variables} set. See above.
32636 The registers that have been collected at the current trace frame.
32637 For each register collected, the name and current value are returned.
32638 The value is formatted according to the @code{--registers-format}
32639 option. See the @command{-data-list-register-values} command for a
32640 list of the allowed formats. The default is @samp{x}.
32643 The trace state variables that have been collected at the current
32644 trace frame. For each trace state variable collected, the name and
32645 current value are returned.
32648 The set of memory ranges that have been collected at the current trace
32649 frame. Its content is a list of tuples. Each tuple represents a
32650 collected memory range and has the following fields:
32654 The start address of the memory range, as hexadecimal literal.
32657 The length of the memory range, as decimal literal.
32660 The contents of the memory block, in hex. This field is only present
32661 if the @code{--memory-contents} option is specified.
32667 @subsubheading @value{GDBN} Command
32669 There is no corresponding @value{GDBN} command.
32671 @subsubheading Example
32673 @subheading -trace-list-variables
32674 @findex -trace-list-variables
32676 @subsubheading Synopsis
32679 -trace-list-variables
32682 Return a table of all defined trace variables. Each element of the
32683 table has the following fields:
32687 The name of the trace variable. This field is always present.
32690 The initial value. This is a 64-bit signed integer. This
32691 field is always present.
32694 The value the trace variable has at the moment. This is a 64-bit
32695 signed integer. This field is absent iff current value is
32696 not defined, for example if the trace was never run, or is
32701 @subsubheading @value{GDBN} Command
32703 The corresponding @value{GDBN} command is @samp{tvariables}.
32705 @subsubheading Example
32709 -trace-list-variables
32710 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32711 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32712 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32713 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32714 body=[variable=@{name="$trace_timestamp",initial="0"@}
32715 variable=@{name="$foo",initial="10",current="15"@}]@}
32719 @subheading -trace-save
32720 @findex -trace-save
32722 @subsubheading Synopsis
32725 -trace-save [ -r ] [ -ctf ] @var{filename}
32728 Saves the collected trace data to @var{filename}. Without the
32729 @samp{-r} option, the data is downloaded from the target and saved
32730 in a local file. With the @samp{-r} option the target is asked
32731 to perform the save.
32733 By default, this command will save the trace in the tfile format. You can
32734 supply the optional @samp{-ctf} argument to save it the CTF format. See
32735 @ref{Trace Files} for more information about CTF.
32737 @subsubheading @value{GDBN} Command
32739 The corresponding @value{GDBN} command is @samp{tsave}.
32742 @subheading -trace-start
32743 @findex -trace-start
32745 @subsubheading Synopsis
32751 Starts a tracing experiment. The result of this command does not
32754 @subsubheading @value{GDBN} Command
32756 The corresponding @value{GDBN} command is @samp{tstart}.
32758 @subheading -trace-status
32759 @findex -trace-status
32761 @subsubheading Synopsis
32767 Obtains the status of a tracing experiment. The result may include
32768 the following fields:
32773 May have a value of either @samp{0}, when no tracing operations are
32774 supported, @samp{1}, when all tracing operations are supported, or
32775 @samp{file} when examining trace file. In the latter case, examining
32776 of trace frame is possible but new tracing experiement cannot be
32777 started. This field is always present.
32780 May have a value of either @samp{0} or @samp{1} depending on whether
32781 tracing experiement is in progress on target. This field is present
32782 if @samp{supported} field is not @samp{0}.
32785 Report the reason why the tracing was stopped last time. This field
32786 may be absent iff tracing was never stopped on target yet. The
32787 value of @samp{request} means the tracing was stopped as result of
32788 the @code{-trace-stop} command. The value of @samp{overflow} means
32789 the tracing buffer is full. The value of @samp{disconnection} means
32790 tracing was automatically stopped when @value{GDBN} has disconnected.
32791 The value of @samp{passcount} means tracing was stopped when a
32792 tracepoint was passed a maximal number of times for that tracepoint.
32793 This field is present if @samp{supported} field is not @samp{0}.
32795 @item stopping-tracepoint
32796 The number of tracepoint whose passcount as exceeded. This field is
32797 present iff the @samp{stop-reason} field has the value of
32801 @itemx frames-created
32802 The @samp{frames} field is a count of the total number of trace frames
32803 in the trace buffer, while @samp{frames-created} is the total created
32804 during the run, including ones that were discarded, such as when a
32805 circular trace buffer filled up. Both fields are optional.
32809 These fields tell the current size of the tracing buffer and the
32810 remaining space. These fields are optional.
32813 The value of the circular trace buffer flag. @code{1} means that the
32814 trace buffer is circular and old trace frames will be discarded if
32815 necessary to make room, @code{0} means that the trace buffer is linear
32819 The value of the disconnected tracing flag. @code{1} means that
32820 tracing will continue after @value{GDBN} disconnects, @code{0} means
32821 that the trace run will stop.
32824 The filename of the trace file being examined. This field is
32825 optional, and only present when examining a trace file.
32829 @subsubheading @value{GDBN} Command
32831 The corresponding @value{GDBN} command is @samp{tstatus}.
32833 @subheading -trace-stop
32834 @findex -trace-stop
32836 @subsubheading Synopsis
32842 Stops a tracing experiment. The result of this command has the same
32843 fields as @code{-trace-status}, except that the @samp{supported} and
32844 @samp{running} fields are not output.
32846 @subsubheading @value{GDBN} Command
32848 The corresponding @value{GDBN} command is @samp{tstop}.
32851 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32852 @node GDB/MI Symbol Query
32853 @section @sc{gdb/mi} Symbol Query Commands
32857 @subheading The @code{-symbol-info-address} Command
32858 @findex -symbol-info-address
32860 @subsubheading Synopsis
32863 -symbol-info-address @var{symbol}
32866 Describe where @var{symbol} is stored.
32868 @subsubheading @value{GDBN} Command
32870 The corresponding @value{GDBN} command is @samp{info address}.
32872 @subsubheading Example
32876 @subheading The @code{-symbol-info-file} Command
32877 @findex -symbol-info-file
32879 @subsubheading Synopsis
32885 Show the file for the symbol.
32887 @subsubheading @value{GDBN} Command
32889 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32890 @samp{gdb_find_file}.
32892 @subsubheading Example
32896 @subheading The @code{-symbol-info-function} Command
32897 @findex -symbol-info-function
32899 @subsubheading Synopsis
32902 -symbol-info-function
32905 Show which function the symbol lives in.
32907 @subsubheading @value{GDBN} Command
32909 @samp{gdb_get_function} in @code{gdbtk}.
32911 @subsubheading Example
32915 @subheading The @code{-symbol-info-line} Command
32916 @findex -symbol-info-line
32918 @subsubheading Synopsis
32924 Show the core addresses of the code for a source line.
32926 @subsubheading @value{GDBN} Command
32928 The corresponding @value{GDBN} command is @samp{info line}.
32929 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32931 @subsubheading Example
32935 @subheading The @code{-symbol-info-symbol} Command
32936 @findex -symbol-info-symbol
32938 @subsubheading Synopsis
32941 -symbol-info-symbol @var{addr}
32944 Describe what symbol is at location @var{addr}.
32946 @subsubheading @value{GDBN} Command
32948 The corresponding @value{GDBN} command is @samp{info symbol}.
32950 @subsubheading Example
32954 @subheading The @code{-symbol-list-functions} Command
32955 @findex -symbol-list-functions
32957 @subsubheading Synopsis
32960 -symbol-list-functions
32963 List the functions in the executable.
32965 @subsubheading @value{GDBN} Command
32967 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32968 @samp{gdb_search} in @code{gdbtk}.
32970 @subsubheading Example
32975 @subheading The @code{-symbol-list-lines} Command
32976 @findex -symbol-list-lines
32978 @subsubheading Synopsis
32981 -symbol-list-lines @var{filename}
32984 Print the list of lines that contain code and their associated program
32985 addresses for the given source filename. The entries are sorted in
32986 ascending PC order.
32988 @subsubheading @value{GDBN} Command
32990 There is no corresponding @value{GDBN} command.
32992 @subsubheading Example
32995 -symbol-list-lines basics.c
32996 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
33002 @subheading The @code{-symbol-list-types} Command
33003 @findex -symbol-list-types
33005 @subsubheading Synopsis
33011 List all the type names.
33013 @subsubheading @value{GDBN} Command
33015 The corresponding commands are @samp{info types} in @value{GDBN},
33016 @samp{gdb_search} in @code{gdbtk}.
33018 @subsubheading Example
33022 @subheading The @code{-symbol-list-variables} Command
33023 @findex -symbol-list-variables
33025 @subsubheading Synopsis
33028 -symbol-list-variables
33031 List all the global and static variable names.
33033 @subsubheading @value{GDBN} Command
33035 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
33037 @subsubheading Example
33041 @subheading The @code{-symbol-locate} Command
33042 @findex -symbol-locate
33044 @subsubheading Synopsis
33050 @subsubheading @value{GDBN} Command
33052 @samp{gdb_loc} in @code{gdbtk}.
33054 @subsubheading Example
33058 @subheading The @code{-symbol-type} Command
33059 @findex -symbol-type
33061 @subsubheading Synopsis
33064 -symbol-type @var{variable}
33067 Show type of @var{variable}.
33069 @subsubheading @value{GDBN} Command
33071 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
33072 @samp{gdb_obj_variable}.
33074 @subsubheading Example
33079 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33080 @node GDB/MI File Commands
33081 @section @sc{gdb/mi} File Commands
33083 This section describes the GDB/MI commands to specify executable file names
33084 and to read in and obtain symbol table information.
33086 @subheading The @code{-file-exec-and-symbols} Command
33087 @findex -file-exec-and-symbols
33089 @subsubheading Synopsis
33092 -file-exec-and-symbols @var{file}
33095 Specify the executable file to be debugged. This file is the one from
33096 which the symbol table is also read. If no file is specified, the
33097 command clears the executable and symbol information. If breakpoints
33098 are set when using this command with no arguments, @value{GDBN} will produce
33099 error messages. Otherwise, no output is produced, except a completion
33102 @subsubheading @value{GDBN} Command
33104 The corresponding @value{GDBN} command is @samp{file}.
33106 @subsubheading Example
33110 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33116 @subheading The @code{-file-exec-file} Command
33117 @findex -file-exec-file
33119 @subsubheading Synopsis
33122 -file-exec-file @var{file}
33125 Specify the executable file to be debugged. Unlike
33126 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
33127 from this file. If used without argument, @value{GDBN} clears the information
33128 about the executable file. No output is produced, except a completion
33131 @subsubheading @value{GDBN} Command
33133 The corresponding @value{GDBN} command is @samp{exec-file}.
33135 @subsubheading Example
33139 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33146 @subheading The @code{-file-list-exec-sections} Command
33147 @findex -file-list-exec-sections
33149 @subsubheading Synopsis
33152 -file-list-exec-sections
33155 List the sections of the current executable file.
33157 @subsubheading @value{GDBN} Command
33159 The @value{GDBN} command @samp{info file} shows, among the rest, the same
33160 information as this command. @code{gdbtk} has a corresponding command
33161 @samp{gdb_load_info}.
33163 @subsubheading Example
33168 @subheading The @code{-file-list-exec-source-file} Command
33169 @findex -file-list-exec-source-file
33171 @subsubheading Synopsis
33174 -file-list-exec-source-file
33177 List the line number, the current source file, and the absolute path
33178 to the current source file for the current executable. The macro
33179 information field has a value of @samp{1} or @samp{0} depending on
33180 whether or not the file includes preprocessor macro information.
33182 @subsubheading @value{GDBN} Command
33184 The @value{GDBN} equivalent is @samp{info source}
33186 @subsubheading Example
33190 123-file-list-exec-source-file
33191 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
33196 @subheading The @code{-file-list-exec-source-files} Command
33197 @findex -file-list-exec-source-files
33199 @subsubheading Synopsis
33202 -file-list-exec-source-files
33205 List the source files for the current executable.
33207 It will always output both the filename and fullname (absolute file
33208 name) of a source file.
33210 @subsubheading @value{GDBN} Command
33212 The @value{GDBN} equivalent is @samp{info sources}.
33213 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
33215 @subsubheading Example
33218 -file-list-exec-source-files
33220 @{file=foo.c,fullname=/home/foo.c@},
33221 @{file=/home/bar.c,fullname=/home/bar.c@},
33222 @{file=gdb_could_not_find_fullpath.c@}]
33226 @subheading The @code{-file-list-shared-libraries} Command
33227 @findex -file-list-shared-libraries
33229 @subsubheading Synopsis
33232 -file-list-shared-libraries [ @var{regexp} ]
33235 List the shared libraries in the program.
33236 With a regular expression @var{regexp}, only those libraries whose
33237 names match @var{regexp} are listed.
33239 @subsubheading @value{GDBN} Command
33241 The corresponding @value{GDBN} command is @samp{info shared}. The fields
33242 have a similar meaning to the @code{=library-loaded} notification.
33243 The @code{ranges} field specifies the multiple segments belonging to this
33244 library. Each range has the following fields:
33248 The address defining the inclusive lower bound of the segment.
33250 The address defining the exclusive upper bound of the segment.
33253 @subsubheading Example
33256 -file-list-exec-source-files
33257 ^done,shared-libraries=[
33258 @{id="/lib/libfoo.so",target-name="/lib/libfoo.so",host-name="/lib/libfoo.so",symbols-loaded="1",thread-group="i1",ranges=[@{from="0x72815989",to="0x728162c0"@}]@},
33259 @{id="/lib/libbar.so",target-name="/lib/libbar.so",host-name="/lib/libbar.so",symbols-loaded="1",thread-group="i1",ranges=[@{from="0x76ee48c0",to="0x76ee9160"@}]@}]
33265 @subheading The @code{-file-list-symbol-files} Command
33266 @findex -file-list-symbol-files
33268 @subsubheading Synopsis
33271 -file-list-symbol-files
33276 @subsubheading @value{GDBN} Command
33278 The corresponding @value{GDBN} command is @samp{info file} (part of it).
33280 @subsubheading Example
33285 @subheading The @code{-file-symbol-file} Command
33286 @findex -file-symbol-file
33288 @subsubheading Synopsis
33291 -file-symbol-file @var{file}
33294 Read symbol table info from the specified @var{file} argument. When
33295 used without arguments, clears @value{GDBN}'s symbol table info. No output is
33296 produced, except for a completion notification.
33298 @subsubheading @value{GDBN} Command
33300 The corresponding @value{GDBN} command is @samp{symbol-file}.
33302 @subsubheading Example
33306 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33312 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33313 @node GDB/MI Memory Overlay Commands
33314 @section @sc{gdb/mi} Memory Overlay Commands
33316 The memory overlay commands are not implemented.
33318 @c @subheading -overlay-auto
33320 @c @subheading -overlay-list-mapping-state
33322 @c @subheading -overlay-list-overlays
33324 @c @subheading -overlay-map
33326 @c @subheading -overlay-off
33328 @c @subheading -overlay-on
33330 @c @subheading -overlay-unmap
33332 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33333 @node GDB/MI Signal Handling Commands
33334 @section @sc{gdb/mi} Signal Handling Commands
33336 Signal handling commands are not implemented.
33338 @c @subheading -signal-handle
33340 @c @subheading -signal-list-handle-actions
33342 @c @subheading -signal-list-signal-types
33346 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33347 @node GDB/MI Target Manipulation
33348 @section @sc{gdb/mi} Target Manipulation Commands
33351 @subheading The @code{-target-attach} Command
33352 @findex -target-attach
33354 @subsubheading Synopsis
33357 -target-attach @var{pid} | @var{gid} | @var{file}
33360 Attach to a process @var{pid} or a file @var{file} outside of
33361 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
33362 group, the id previously returned by
33363 @samp{-list-thread-groups --available} must be used.
33365 @subsubheading @value{GDBN} Command
33367 The corresponding @value{GDBN} command is @samp{attach}.
33369 @subsubheading Example
33373 =thread-created,id="1"
33374 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
33380 @subheading The @code{-target-compare-sections} Command
33381 @findex -target-compare-sections
33383 @subsubheading Synopsis
33386 -target-compare-sections [ @var{section} ]
33389 Compare data of section @var{section} on target to the exec file.
33390 Without the argument, all sections are compared.
33392 @subsubheading @value{GDBN} Command
33394 The @value{GDBN} equivalent is @samp{compare-sections}.
33396 @subsubheading Example
33401 @subheading The @code{-target-detach} Command
33402 @findex -target-detach
33404 @subsubheading Synopsis
33407 -target-detach [ @var{pid} | @var{gid} ]
33410 Detach from the remote target which normally resumes its execution.
33411 If either @var{pid} or @var{gid} is specified, detaches from either
33412 the specified process, or specified thread group. There's no output.
33414 @subsubheading @value{GDBN} Command
33416 The corresponding @value{GDBN} command is @samp{detach}.
33418 @subsubheading Example
33428 @subheading The @code{-target-disconnect} Command
33429 @findex -target-disconnect
33431 @subsubheading Synopsis
33437 Disconnect from the remote target. There's no output and the target is
33438 generally not resumed.
33440 @subsubheading @value{GDBN} Command
33442 The corresponding @value{GDBN} command is @samp{disconnect}.
33444 @subsubheading Example
33454 @subheading The @code{-target-download} Command
33455 @findex -target-download
33457 @subsubheading Synopsis
33463 Loads the executable onto the remote target.
33464 It prints out an update message every half second, which includes the fields:
33468 The name of the section.
33470 The size of what has been sent so far for that section.
33472 The size of the section.
33474 The total size of what was sent so far (the current and the previous sections).
33476 The size of the overall executable to download.
33480 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
33481 @sc{gdb/mi} Output Syntax}).
33483 In addition, it prints the name and size of the sections, as they are
33484 downloaded. These messages include the following fields:
33488 The name of the section.
33490 The size of the section.
33492 The size of the overall executable to download.
33496 At the end, a summary is printed.
33498 @subsubheading @value{GDBN} Command
33500 The corresponding @value{GDBN} command is @samp{load}.
33502 @subsubheading Example
33504 Note: each status message appears on a single line. Here the messages
33505 have been broken down so that they can fit onto a page.
33510 +download,@{section=".text",section-size="6668",total-size="9880"@}
33511 +download,@{section=".text",section-sent="512",section-size="6668",
33512 total-sent="512",total-size="9880"@}
33513 +download,@{section=".text",section-sent="1024",section-size="6668",
33514 total-sent="1024",total-size="9880"@}
33515 +download,@{section=".text",section-sent="1536",section-size="6668",
33516 total-sent="1536",total-size="9880"@}
33517 +download,@{section=".text",section-sent="2048",section-size="6668",
33518 total-sent="2048",total-size="9880"@}
33519 +download,@{section=".text",section-sent="2560",section-size="6668",
33520 total-sent="2560",total-size="9880"@}
33521 +download,@{section=".text",section-sent="3072",section-size="6668",
33522 total-sent="3072",total-size="9880"@}
33523 +download,@{section=".text",section-sent="3584",section-size="6668",
33524 total-sent="3584",total-size="9880"@}
33525 +download,@{section=".text",section-sent="4096",section-size="6668",
33526 total-sent="4096",total-size="9880"@}
33527 +download,@{section=".text",section-sent="4608",section-size="6668",
33528 total-sent="4608",total-size="9880"@}
33529 +download,@{section=".text",section-sent="5120",section-size="6668",
33530 total-sent="5120",total-size="9880"@}
33531 +download,@{section=".text",section-sent="5632",section-size="6668",
33532 total-sent="5632",total-size="9880"@}
33533 +download,@{section=".text",section-sent="6144",section-size="6668",
33534 total-sent="6144",total-size="9880"@}
33535 +download,@{section=".text",section-sent="6656",section-size="6668",
33536 total-sent="6656",total-size="9880"@}
33537 +download,@{section=".init",section-size="28",total-size="9880"@}
33538 +download,@{section=".fini",section-size="28",total-size="9880"@}
33539 +download,@{section=".data",section-size="3156",total-size="9880"@}
33540 +download,@{section=".data",section-sent="512",section-size="3156",
33541 total-sent="7236",total-size="9880"@}
33542 +download,@{section=".data",section-sent="1024",section-size="3156",
33543 total-sent="7748",total-size="9880"@}
33544 +download,@{section=".data",section-sent="1536",section-size="3156",
33545 total-sent="8260",total-size="9880"@}
33546 +download,@{section=".data",section-sent="2048",section-size="3156",
33547 total-sent="8772",total-size="9880"@}
33548 +download,@{section=".data",section-sent="2560",section-size="3156",
33549 total-sent="9284",total-size="9880"@}
33550 +download,@{section=".data",section-sent="3072",section-size="3156",
33551 total-sent="9796",total-size="9880"@}
33552 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
33559 @subheading The @code{-target-exec-status} Command
33560 @findex -target-exec-status
33562 @subsubheading Synopsis
33565 -target-exec-status
33568 Provide information on the state of the target (whether it is running or
33569 not, for instance).
33571 @subsubheading @value{GDBN} Command
33573 There's no equivalent @value{GDBN} command.
33575 @subsubheading Example
33579 @subheading The @code{-target-list-available-targets} Command
33580 @findex -target-list-available-targets
33582 @subsubheading Synopsis
33585 -target-list-available-targets
33588 List the possible targets to connect to.
33590 @subsubheading @value{GDBN} Command
33592 The corresponding @value{GDBN} command is @samp{help target}.
33594 @subsubheading Example
33598 @subheading The @code{-target-list-current-targets} Command
33599 @findex -target-list-current-targets
33601 @subsubheading Synopsis
33604 -target-list-current-targets
33607 Describe the current target.
33609 @subsubheading @value{GDBN} Command
33611 The corresponding information is printed by @samp{info file} (among
33614 @subsubheading Example
33618 @subheading The @code{-target-list-parameters} Command
33619 @findex -target-list-parameters
33621 @subsubheading Synopsis
33624 -target-list-parameters
33630 @subsubheading @value{GDBN} Command
33634 @subsubheading Example
33637 @subheading The @code{-target-flash-erase} Command
33638 @findex -target-flash-erase
33640 @subsubheading Synopsis
33643 -target-flash-erase
33646 Erases all known flash memory regions on the target.
33648 The corresponding @value{GDBN} command is @samp{flash-erase}.
33650 The output is a list of flash regions that have been erased, with starting
33651 addresses and memory region sizes.
33655 -target-flash-erase
33656 ^done,erased-regions=@{address="0x0",size="0x40000"@}
33660 @subheading The @code{-target-select} Command
33661 @findex -target-select
33663 @subsubheading Synopsis
33666 -target-select @var{type} @var{parameters @dots{}}
33669 Connect @value{GDBN} to the remote target. This command takes two args:
33673 The type of target, for instance @samp{remote}, etc.
33674 @item @var{parameters}
33675 Device names, host names and the like. @xref{Target Commands, ,
33676 Commands for Managing Targets}, for more details.
33679 The output is a connection notification, followed by the address at
33680 which the target program is, in the following form:
33683 ^connected,addr="@var{address}",func="@var{function name}",
33684 args=[@var{arg list}]
33687 @subsubheading @value{GDBN} Command
33689 The corresponding @value{GDBN} command is @samp{target}.
33691 @subsubheading Example
33695 -target-select remote /dev/ttya
33696 ^connected,addr="0xfe00a300",func="??",args=[]
33700 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33701 @node GDB/MI File Transfer Commands
33702 @section @sc{gdb/mi} File Transfer Commands
33705 @subheading The @code{-target-file-put} Command
33706 @findex -target-file-put
33708 @subsubheading Synopsis
33711 -target-file-put @var{hostfile} @var{targetfile}
33714 Copy file @var{hostfile} from the host system (the machine running
33715 @value{GDBN}) to @var{targetfile} on the target system.
33717 @subsubheading @value{GDBN} Command
33719 The corresponding @value{GDBN} command is @samp{remote put}.
33721 @subsubheading Example
33725 -target-file-put localfile remotefile
33731 @subheading The @code{-target-file-get} Command
33732 @findex -target-file-get
33734 @subsubheading Synopsis
33737 -target-file-get @var{targetfile} @var{hostfile}
33740 Copy file @var{targetfile} from the target system to @var{hostfile}
33741 on the host system.
33743 @subsubheading @value{GDBN} Command
33745 The corresponding @value{GDBN} command is @samp{remote get}.
33747 @subsubheading Example
33751 -target-file-get remotefile localfile
33757 @subheading The @code{-target-file-delete} Command
33758 @findex -target-file-delete
33760 @subsubheading Synopsis
33763 -target-file-delete @var{targetfile}
33766 Delete @var{targetfile} from the target system.
33768 @subsubheading @value{GDBN} Command
33770 The corresponding @value{GDBN} command is @samp{remote delete}.
33772 @subsubheading Example
33776 -target-file-delete remotefile
33782 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33783 @node GDB/MI Ada Exceptions Commands
33784 @section Ada Exceptions @sc{gdb/mi} Commands
33786 @subheading The @code{-info-ada-exceptions} Command
33787 @findex -info-ada-exceptions
33789 @subsubheading Synopsis
33792 -info-ada-exceptions [ @var{regexp}]
33795 List all Ada exceptions defined within the program being debugged.
33796 With a regular expression @var{regexp}, only those exceptions whose
33797 names match @var{regexp} are listed.
33799 @subsubheading @value{GDBN} Command
33801 The corresponding @value{GDBN} command is @samp{info exceptions}.
33803 @subsubheading Result
33805 The result is a table of Ada exceptions. The following columns are
33806 defined for each exception:
33810 The name of the exception.
33813 The address of the exception.
33817 @subsubheading Example
33820 -info-ada-exceptions aint
33821 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
33822 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
33823 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
33824 body=[@{name="constraint_error",address="0x0000000000613da0"@},
33825 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
33828 @subheading Catching Ada Exceptions
33830 The commands describing how to ask @value{GDBN} to stop when a program
33831 raises an exception are described at @ref{Ada Exception GDB/MI
33832 Catchpoint Commands}.
33835 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33836 @node GDB/MI Support Commands
33837 @section @sc{gdb/mi} Support Commands
33839 Since new commands and features get regularly added to @sc{gdb/mi},
33840 some commands are available to help front-ends query the debugger
33841 about support for these capabilities. Similarly, it is also possible
33842 to query @value{GDBN} about target support of certain features.
33844 @subheading The @code{-info-gdb-mi-command} Command
33845 @cindex @code{-info-gdb-mi-command}
33846 @findex -info-gdb-mi-command
33848 @subsubheading Synopsis
33851 -info-gdb-mi-command @var{cmd_name}
33854 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
33856 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
33857 is technically not part of the command name (@pxref{GDB/MI Input
33858 Syntax}), and thus should be omitted in @var{cmd_name}. However,
33859 for ease of use, this command also accepts the form with the leading
33862 @subsubheading @value{GDBN} Command
33864 There is no corresponding @value{GDBN} command.
33866 @subsubheading Result
33868 The result is a tuple. There is currently only one field:
33872 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
33873 @code{"false"} otherwise.
33877 @subsubheading Example
33879 Here is an example where the @sc{gdb/mi} command does not exist:
33882 -info-gdb-mi-command unsupported-command
33883 ^done,command=@{exists="false"@}
33887 And here is an example where the @sc{gdb/mi} command is known
33891 -info-gdb-mi-command symbol-list-lines
33892 ^done,command=@{exists="true"@}
33895 @subheading The @code{-list-features} Command
33896 @findex -list-features
33897 @cindex supported @sc{gdb/mi} features, list
33899 Returns a list of particular features of the MI protocol that
33900 this version of gdb implements. A feature can be a command,
33901 or a new field in an output of some command, or even an
33902 important bugfix. While a frontend can sometimes detect presence
33903 of a feature at runtime, it is easier to perform detection at debugger
33906 The command returns a list of strings, with each string naming an
33907 available feature. Each returned string is just a name, it does not
33908 have any internal structure. The list of possible feature names
33914 (gdb) -list-features
33915 ^done,result=["feature1","feature2"]
33918 The current list of features is:
33921 @item frozen-varobjs
33922 Indicates support for the @code{-var-set-frozen} command, as well
33923 as possible presense of the @code{frozen} field in the output
33924 of @code{-varobj-create}.
33925 @item pending-breakpoints
33926 Indicates support for the @option{-f} option to the @code{-break-insert}
33929 Indicates Python scripting support, Python-based
33930 pretty-printing commands, and possible presence of the
33931 @samp{display_hint} field in the output of @code{-var-list-children}
33933 Indicates support for the @code{-thread-info} command.
33934 @item data-read-memory-bytes
33935 Indicates support for the @code{-data-read-memory-bytes} and the
33936 @code{-data-write-memory-bytes} commands.
33937 @item breakpoint-notifications
33938 Indicates that changes to breakpoints and breakpoints created via the
33939 CLI will be announced via async records.
33940 @item ada-task-info
33941 Indicates support for the @code{-ada-task-info} command.
33942 @item language-option
33943 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
33944 option (@pxref{Context management}).
33945 @item info-gdb-mi-command
33946 Indicates support for the @code{-info-gdb-mi-command} command.
33947 @item undefined-command-error-code
33948 Indicates support for the "undefined-command" error code in error result
33949 records, produced when trying to execute an undefined @sc{gdb/mi} command
33950 (@pxref{GDB/MI Result Records}).
33951 @item exec-run-start-option
33952 Indicates that the @code{-exec-run} command supports the @option{--start}
33953 option (@pxref{GDB/MI Program Execution}).
33954 @item data-disassemble-a-option
33955 Indicates that the @code{-data-disassemble} command supports the @option{-a}
33956 option (@pxref{GDB/MI Data Manipulation}).
33959 @subheading The @code{-list-target-features} Command
33960 @findex -list-target-features
33962 Returns a list of particular features that are supported by the
33963 target. Those features affect the permitted MI commands, but
33964 unlike the features reported by the @code{-list-features} command, the
33965 features depend on which target GDB is using at the moment. Whenever
33966 a target can change, due to commands such as @code{-target-select},
33967 @code{-target-attach} or @code{-exec-run}, the list of target features
33968 may change, and the frontend should obtain it again.
33972 (gdb) -list-target-features
33973 ^done,result=["async"]
33976 The current list of features is:
33980 Indicates that the target is capable of asynchronous command
33981 execution, which means that @value{GDBN} will accept further commands
33982 while the target is running.
33985 Indicates that the target is capable of reverse execution.
33986 @xref{Reverse Execution}, for more information.
33990 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33991 @node GDB/MI Miscellaneous Commands
33992 @section Miscellaneous @sc{gdb/mi} Commands
33994 @c @subheading -gdb-complete
33996 @subheading The @code{-gdb-exit} Command
33999 @subsubheading Synopsis
34005 Exit @value{GDBN} immediately.
34007 @subsubheading @value{GDBN} Command
34009 Approximately corresponds to @samp{quit}.
34011 @subsubheading Example
34021 @subheading The @code{-exec-abort} Command
34022 @findex -exec-abort
34024 @subsubheading Synopsis
34030 Kill the inferior running program.
34032 @subsubheading @value{GDBN} Command
34034 The corresponding @value{GDBN} command is @samp{kill}.
34036 @subsubheading Example
34041 @subheading The @code{-gdb-set} Command
34044 @subsubheading Synopsis
34050 Set an internal @value{GDBN} variable.
34051 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
34053 @subsubheading @value{GDBN} Command
34055 The corresponding @value{GDBN} command is @samp{set}.
34057 @subsubheading Example
34067 @subheading The @code{-gdb-show} Command
34070 @subsubheading Synopsis
34076 Show the current value of a @value{GDBN} variable.
34078 @subsubheading @value{GDBN} Command
34080 The corresponding @value{GDBN} command is @samp{show}.
34082 @subsubheading Example
34091 @c @subheading -gdb-source
34094 @subheading The @code{-gdb-version} Command
34095 @findex -gdb-version
34097 @subsubheading Synopsis
34103 Show version information for @value{GDBN}. Used mostly in testing.
34105 @subsubheading @value{GDBN} Command
34107 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
34108 default shows this information when you start an interactive session.
34110 @subsubheading Example
34112 @c This example modifies the actual output from GDB to avoid overfull
34118 ~Copyright 2000 Free Software Foundation, Inc.
34119 ~GDB is free software, covered by the GNU General Public License, and
34120 ~you are welcome to change it and/or distribute copies of it under
34121 ~ certain conditions.
34122 ~Type "show copying" to see the conditions.
34123 ~There is absolutely no warranty for GDB. Type "show warranty" for
34125 ~This GDB was configured as
34126 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
34131 @subheading The @code{-list-thread-groups} Command
34132 @findex -list-thread-groups
34134 @subheading Synopsis
34137 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
34140 Lists thread groups (@pxref{Thread groups}). When a single thread
34141 group is passed as the argument, lists the children of that group.
34142 When several thread group are passed, lists information about those
34143 thread groups. Without any parameters, lists information about all
34144 top-level thread groups.
34146 Normally, thread groups that are being debugged are reported.
34147 With the @samp{--available} option, @value{GDBN} reports thread groups
34148 available on the target.
34150 The output of this command may have either a @samp{threads} result or
34151 a @samp{groups} result. The @samp{thread} result has a list of tuples
34152 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
34153 Information}). The @samp{groups} result has a list of tuples as value,
34154 each tuple describing a thread group. If top-level groups are
34155 requested (that is, no parameter is passed), or when several groups
34156 are passed, the output always has a @samp{groups} result. The format
34157 of the @samp{group} result is described below.
34159 To reduce the number of roundtrips it's possible to list thread groups
34160 together with their children, by passing the @samp{--recurse} option
34161 and the recursion depth. Presently, only recursion depth of 1 is
34162 permitted. If this option is present, then every reported thread group
34163 will also include its children, either as @samp{group} or
34164 @samp{threads} field.
34166 In general, any combination of option and parameters is permitted, with
34167 the following caveats:
34171 When a single thread group is passed, the output will typically
34172 be the @samp{threads} result. Because threads may not contain
34173 anything, the @samp{recurse} option will be ignored.
34176 When the @samp{--available} option is passed, limited information may
34177 be available. In particular, the list of threads of a process might
34178 be inaccessible. Further, specifying specific thread groups might
34179 not give any performance advantage over listing all thread groups.
34180 The frontend should assume that @samp{-list-thread-groups --available}
34181 is always an expensive operation and cache the results.
34185 The @samp{groups} result is a list of tuples, where each tuple may
34186 have the following fields:
34190 Identifier of the thread group. This field is always present.
34191 The identifier is an opaque string; frontends should not try to
34192 convert it to an integer, even though it might look like one.
34195 The type of the thread group. At present, only @samp{process} is a
34199 The target-specific process identifier. This field is only present
34200 for thread groups of type @samp{process} and only if the process exists.
34203 The exit code of this group's last exited thread, formatted in octal.
34204 This field is only present for thread groups of type @samp{process} and
34205 only if the process is not running.
34208 The number of children this thread group has. This field may be
34209 absent for an available thread group.
34212 This field has a list of tuples as value, each tuple describing a
34213 thread. It may be present if the @samp{--recurse} option is
34214 specified, and it's actually possible to obtain the threads.
34217 This field is a list of integers, each identifying a core that one
34218 thread of the group is running on. This field may be absent if
34219 such information is not available.
34222 The name of the executable file that corresponds to this thread group.
34223 The field is only present for thread groups of type @samp{process},
34224 and only if there is a corresponding executable file.
34228 @subheading Example
34232 -list-thread-groups
34233 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
34234 -list-thread-groups 17
34235 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
34236 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
34237 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
34238 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
34239 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
34240 -list-thread-groups --available
34241 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
34242 -list-thread-groups --available --recurse 1
34243 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34244 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34245 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
34246 -list-thread-groups --available --recurse 1 17 18
34247 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34248 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34249 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
34252 @subheading The @code{-info-os} Command
34255 @subsubheading Synopsis
34258 -info-os [ @var{type} ]
34261 If no argument is supplied, the command returns a table of available
34262 operating-system-specific information types. If one of these types is
34263 supplied as an argument @var{type}, then the command returns a table
34264 of data of that type.
34266 The types of information available depend on the target operating
34269 @subsubheading @value{GDBN} Command
34271 The corresponding @value{GDBN} command is @samp{info os}.
34273 @subsubheading Example
34275 When run on a @sc{gnu}/Linux system, the output will look something
34281 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
34282 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
34283 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
34284 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
34285 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
34287 item=@{col0="files",col1="Listing of all file descriptors",
34288 col2="File descriptors"@},
34289 item=@{col0="modules",col1="Listing of all loaded kernel modules",
34290 col2="Kernel modules"@},
34291 item=@{col0="msg",col1="Listing of all message queues",
34292 col2="Message queues"@},
34293 item=@{col0="processes",col1="Listing of all processes",
34294 col2="Processes"@},
34295 item=@{col0="procgroups",col1="Listing of all process groups",
34296 col2="Process groups"@},
34297 item=@{col0="semaphores",col1="Listing of all semaphores",
34298 col2="Semaphores"@},
34299 item=@{col0="shm",col1="Listing of all shared-memory regions",
34300 col2="Shared-memory regions"@},
34301 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
34303 item=@{col0="threads",col1="Listing of all threads",
34307 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
34308 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
34309 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
34310 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
34311 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
34312 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
34313 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
34314 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
34316 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
34317 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
34321 (Note that the MI output here includes a @code{"Title"} column that
34322 does not appear in command-line @code{info os}; this column is useful
34323 for MI clients that want to enumerate the types of data, such as in a
34324 popup menu, but is needless clutter on the command line, and
34325 @code{info os} omits it.)
34327 @subheading The @code{-add-inferior} Command
34328 @findex -add-inferior
34330 @subheading Synopsis
34336 Creates a new inferior (@pxref{Inferiors and Programs}). The created
34337 inferior is not associated with any executable. Such association may
34338 be established with the @samp{-file-exec-and-symbols} command
34339 (@pxref{GDB/MI File Commands}). The command response has a single
34340 field, @samp{inferior}, whose value is the identifier of the
34341 thread group corresponding to the new inferior.
34343 @subheading Example
34348 ^done,inferior="i3"
34351 @subheading The @code{-interpreter-exec} Command
34352 @findex -interpreter-exec
34354 @subheading Synopsis
34357 -interpreter-exec @var{interpreter} @var{command}
34359 @anchor{-interpreter-exec}
34361 Execute the specified @var{command} in the given @var{interpreter}.
34363 @subheading @value{GDBN} Command
34365 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
34367 @subheading Example
34371 -interpreter-exec console "break main"
34372 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
34373 &"During symbol reading, bad structure-type format.\n"
34374 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
34379 @subheading The @code{-inferior-tty-set} Command
34380 @findex -inferior-tty-set
34382 @subheading Synopsis
34385 -inferior-tty-set /dev/pts/1
34388 Set terminal for future runs of the program being debugged.
34390 @subheading @value{GDBN} Command
34392 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
34394 @subheading Example
34398 -inferior-tty-set /dev/pts/1
34403 @subheading The @code{-inferior-tty-show} Command
34404 @findex -inferior-tty-show
34406 @subheading Synopsis
34412 Show terminal for future runs of program being debugged.
34414 @subheading @value{GDBN} Command
34416 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
34418 @subheading Example
34422 -inferior-tty-set /dev/pts/1
34426 ^done,inferior_tty_terminal="/dev/pts/1"
34430 @subheading The @code{-enable-timings} Command
34431 @findex -enable-timings
34433 @subheading Synopsis
34436 -enable-timings [yes | no]
34439 Toggle the printing of the wallclock, user and system times for an MI
34440 command as a field in its output. This command is to help frontend
34441 developers optimize the performance of their code. No argument is
34442 equivalent to @samp{yes}.
34444 @subheading @value{GDBN} Command
34448 @subheading Example
34456 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
34457 addr="0x080484ed",func="main",file="myprog.c",
34458 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
34460 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
34468 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
34469 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
34470 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
34471 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
34476 @chapter @value{GDBN} Annotations
34478 This chapter describes annotations in @value{GDBN}. Annotations were
34479 designed to interface @value{GDBN} to graphical user interfaces or other
34480 similar programs which want to interact with @value{GDBN} at a
34481 relatively high level.
34483 The annotation mechanism has largely been superseded by @sc{gdb/mi}
34487 This is Edition @value{EDITION}, @value{DATE}.
34491 * Annotations Overview:: What annotations are; the general syntax.
34492 * Server Prefix:: Issuing a command without affecting user state.
34493 * Prompting:: Annotations marking @value{GDBN}'s need for input.
34494 * Errors:: Annotations for error messages.
34495 * Invalidation:: Some annotations describe things now invalid.
34496 * Annotations for Running::
34497 Whether the program is running, how it stopped, etc.
34498 * Source Annotations:: Annotations describing source code.
34501 @node Annotations Overview
34502 @section What is an Annotation?
34503 @cindex annotations
34505 Annotations start with a newline character, two @samp{control-z}
34506 characters, and the name of the annotation. If there is no additional
34507 information associated with this annotation, the name of the annotation
34508 is followed immediately by a newline. If there is additional
34509 information, the name of the annotation is followed by a space, the
34510 additional information, and a newline. The additional information
34511 cannot contain newline characters.
34513 Any output not beginning with a newline and two @samp{control-z}
34514 characters denotes literal output from @value{GDBN}. Currently there is
34515 no need for @value{GDBN} to output a newline followed by two
34516 @samp{control-z} characters, but if there was such a need, the
34517 annotations could be extended with an @samp{escape} annotation which
34518 means those three characters as output.
34520 The annotation @var{level}, which is specified using the
34521 @option{--annotate} command line option (@pxref{Mode Options}), controls
34522 how much information @value{GDBN} prints together with its prompt,
34523 values of expressions, source lines, and other types of output. Level 0
34524 is for no annotations, level 1 is for use when @value{GDBN} is run as a
34525 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
34526 for programs that control @value{GDBN}, and level 2 annotations have
34527 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
34528 Interface, annotate, GDB's Obsolete Annotations}).
34531 @kindex set annotate
34532 @item set annotate @var{level}
34533 The @value{GDBN} command @code{set annotate} sets the level of
34534 annotations to the specified @var{level}.
34536 @item show annotate
34537 @kindex show annotate
34538 Show the current annotation level.
34541 This chapter describes level 3 annotations.
34543 A simple example of starting up @value{GDBN} with annotations is:
34546 $ @kbd{gdb --annotate=3}
34548 Copyright 2003 Free Software Foundation, Inc.
34549 GDB is free software, covered by the GNU General Public License,
34550 and you are welcome to change it and/or distribute copies of it
34551 under certain conditions.
34552 Type "show copying" to see the conditions.
34553 There is absolutely no warranty for GDB. Type "show warranty"
34555 This GDB was configured as "i386-pc-linux-gnu"
34566 Here @samp{quit} is input to @value{GDBN}; the rest is output from
34567 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
34568 denotes a @samp{control-z} character) are annotations; the rest is
34569 output from @value{GDBN}.
34571 @node Server Prefix
34572 @section The Server Prefix
34573 @cindex server prefix
34575 If you prefix a command with @samp{server } then it will not affect
34576 the command history, nor will it affect @value{GDBN}'s notion of which
34577 command to repeat if @key{RET} is pressed on a line by itself. This
34578 means that commands can be run behind a user's back by a front-end in
34579 a transparent manner.
34581 The @code{server } prefix does not affect the recording of values into
34582 the value history; to print a value without recording it into the
34583 value history, use the @code{output} command instead of the
34584 @code{print} command.
34586 Using this prefix also disables confirmation requests
34587 (@pxref{confirmation requests}).
34590 @section Annotation for @value{GDBN} Input
34592 @cindex annotations for prompts
34593 When @value{GDBN} prompts for input, it annotates this fact so it is possible
34594 to know when to send output, when the output from a given command is
34597 Different kinds of input each have a different @dfn{input type}. Each
34598 input type has three annotations: a @code{pre-} annotation, which
34599 denotes the beginning of any prompt which is being output, a plain
34600 annotation, which denotes the end of the prompt, and then a @code{post-}
34601 annotation which denotes the end of any echo which may (or may not) be
34602 associated with the input. For example, the @code{prompt} input type
34603 features the following annotations:
34611 The input types are
34614 @findex pre-prompt annotation
34615 @findex prompt annotation
34616 @findex post-prompt annotation
34618 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
34620 @findex pre-commands annotation
34621 @findex commands annotation
34622 @findex post-commands annotation
34624 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
34625 command. The annotations are repeated for each command which is input.
34627 @findex pre-overload-choice annotation
34628 @findex overload-choice annotation
34629 @findex post-overload-choice annotation
34630 @item overload-choice
34631 When @value{GDBN} wants the user to select between various overloaded functions.
34633 @findex pre-query annotation
34634 @findex query annotation
34635 @findex post-query annotation
34637 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
34639 @findex pre-prompt-for-continue annotation
34640 @findex prompt-for-continue annotation
34641 @findex post-prompt-for-continue annotation
34642 @item prompt-for-continue
34643 When @value{GDBN} is asking the user to press return to continue. Note: Don't
34644 expect this to work well; instead use @code{set height 0} to disable
34645 prompting. This is because the counting of lines is buggy in the
34646 presence of annotations.
34651 @cindex annotations for errors, warnings and interrupts
34653 @findex quit annotation
34658 This annotation occurs right before @value{GDBN} responds to an interrupt.
34660 @findex error annotation
34665 This annotation occurs right before @value{GDBN} responds to an error.
34667 Quit and error annotations indicate that any annotations which @value{GDBN} was
34668 in the middle of may end abruptly. For example, if a
34669 @code{value-history-begin} annotation is followed by a @code{error}, one
34670 cannot expect to receive the matching @code{value-history-end}. One
34671 cannot expect not to receive it either, however; an error annotation
34672 does not necessarily mean that @value{GDBN} is immediately returning all the way
34675 @findex error-begin annotation
34676 A quit or error annotation may be preceded by
34682 Any output between that and the quit or error annotation is the error
34685 Warning messages are not yet annotated.
34686 @c If we want to change that, need to fix warning(), type_error(),
34687 @c range_error(), and possibly other places.
34690 @section Invalidation Notices
34692 @cindex annotations for invalidation messages
34693 The following annotations say that certain pieces of state may have
34697 @findex frames-invalid annotation
34698 @item ^Z^Zframes-invalid
34700 The frames (for example, output from the @code{backtrace} command) may
34703 @findex breakpoints-invalid annotation
34704 @item ^Z^Zbreakpoints-invalid
34706 The breakpoints may have changed. For example, the user just added or
34707 deleted a breakpoint.
34710 @node Annotations for Running
34711 @section Running the Program
34712 @cindex annotations for running programs
34714 @findex starting annotation
34715 @findex stopping annotation
34716 When the program starts executing due to a @value{GDBN} command such as
34717 @code{step} or @code{continue},
34723 is output. When the program stops,
34729 is output. Before the @code{stopped} annotation, a variety of
34730 annotations describe how the program stopped.
34733 @findex exited annotation
34734 @item ^Z^Zexited @var{exit-status}
34735 The program exited, and @var{exit-status} is the exit status (zero for
34736 successful exit, otherwise nonzero).
34738 @findex signalled annotation
34739 @findex signal-name annotation
34740 @findex signal-name-end annotation
34741 @findex signal-string annotation
34742 @findex signal-string-end annotation
34743 @item ^Z^Zsignalled
34744 The program exited with a signal. After the @code{^Z^Zsignalled}, the
34745 annotation continues:
34751 ^Z^Zsignal-name-end
34755 ^Z^Zsignal-string-end
34760 where @var{name} is the name of the signal, such as @code{SIGILL} or
34761 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
34762 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
34763 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
34764 user's benefit and have no particular format.
34766 @findex signal annotation
34768 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
34769 just saying that the program received the signal, not that it was
34770 terminated with it.
34772 @findex breakpoint annotation
34773 @item ^Z^Zbreakpoint @var{number}
34774 The program hit breakpoint number @var{number}.
34776 @findex watchpoint annotation
34777 @item ^Z^Zwatchpoint @var{number}
34778 The program hit watchpoint number @var{number}.
34781 @node Source Annotations
34782 @section Displaying Source
34783 @cindex annotations for source display
34785 @findex source annotation
34786 The following annotation is used instead of displaying source code:
34789 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
34792 where @var{filename} is an absolute file name indicating which source
34793 file, @var{line} is the line number within that file (where 1 is the
34794 first line in the file), @var{character} is the character position
34795 within the file (where 0 is the first character in the file) (for most
34796 debug formats this will necessarily point to the beginning of a line),
34797 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
34798 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
34799 @var{addr} is the address in the target program associated with the
34800 source which is being displayed. The @var{addr} is in the form @samp{0x}
34801 followed by one or more lowercase hex digits (note that this does not
34802 depend on the language).
34804 @node JIT Interface
34805 @chapter JIT Compilation Interface
34806 @cindex just-in-time compilation
34807 @cindex JIT compilation interface
34809 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
34810 interface. A JIT compiler is a program or library that generates native
34811 executable code at runtime and executes it, usually in order to achieve good
34812 performance while maintaining platform independence.
34814 Programs that use JIT compilation are normally difficult to debug because
34815 portions of their code are generated at runtime, instead of being loaded from
34816 object files, which is where @value{GDBN} normally finds the program's symbols
34817 and debug information. In order to debug programs that use JIT compilation,
34818 @value{GDBN} has an interface that allows the program to register in-memory
34819 symbol files with @value{GDBN} at runtime.
34821 If you are using @value{GDBN} to debug a program that uses this interface, then
34822 it should work transparently so long as you have not stripped the binary. If
34823 you are developing a JIT compiler, then the interface is documented in the rest
34824 of this chapter. At this time, the only known client of this interface is the
34827 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
34828 JIT compiler communicates with @value{GDBN} by writing data into a global
34829 variable and calling a fuction at a well-known symbol. When @value{GDBN}
34830 attaches, it reads a linked list of symbol files from the global variable to
34831 find existing code, and puts a breakpoint in the function so that it can find
34832 out about additional code.
34835 * Declarations:: Relevant C struct declarations
34836 * Registering Code:: Steps to register code
34837 * Unregistering Code:: Steps to unregister code
34838 * Custom Debug Info:: Emit debug information in a custom format
34842 @section JIT Declarations
34844 These are the relevant struct declarations that a C program should include to
34845 implement the interface:
34855 struct jit_code_entry
34857 struct jit_code_entry *next_entry;
34858 struct jit_code_entry *prev_entry;
34859 const char *symfile_addr;
34860 uint64_t symfile_size;
34863 struct jit_descriptor
34866 /* This type should be jit_actions_t, but we use uint32_t
34867 to be explicit about the bitwidth. */
34868 uint32_t action_flag;
34869 struct jit_code_entry *relevant_entry;
34870 struct jit_code_entry *first_entry;
34873 /* GDB puts a breakpoint in this function. */
34874 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34876 /* Make sure to specify the version statically, because the
34877 debugger may check the version before we can set it. */
34878 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34881 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34882 modifications to this global data properly, which can easily be done by putting
34883 a global mutex around modifications to these structures.
34885 @node Registering Code
34886 @section Registering Code
34888 To register code with @value{GDBN}, the JIT should follow this protocol:
34892 Generate an object file in memory with symbols and other desired debug
34893 information. The file must include the virtual addresses of the sections.
34896 Create a code entry for the file, which gives the start and size of the symbol
34900 Add it to the linked list in the JIT descriptor.
34903 Point the relevant_entry field of the descriptor at the entry.
34906 Set @code{action_flag} to @code{JIT_REGISTER} and call
34907 @code{__jit_debug_register_code}.
34910 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34911 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34912 new code. However, the linked list must still be maintained in order to allow
34913 @value{GDBN} to attach to a running process and still find the symbol files.
34915 @node Unregistering Code
34916 @section Unregistering Code
34918 If code is freed, then the JIT should use the following protocol:
34922 Remove the code entry corresponding to the code from the linked list.
34925 Point the @code{relevant_entry} field of the descriptor at the code entry.
34928 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34929 @code{__jit_debug_register_code}.
34932 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34933 and the JIT will leak the memory used for the associated symbol files.
34935 @node Custom Debug Info
34936 @section Custom Debug Info
34937 @cindex custom JIT debug info
34938 @cindex JIT debug info reader
34940 Generating debug information in platform-native file formats (like ELF
34941 or COFF) may be an overkill for JIT compilers; especially if all the
34942 debug info is used for is displaying a meaningful backtrace. The
34943 issue can be resolved by having the JIT writers decide on a debug info
34944 format and also provide a reader that parses the debug info generated
34945 by the JIT compiler. This section gives a brief overview on writing
34946 such a parser. More specific details can be found in the source file
34947 @file{gdb/jit-reader.in}, which is also installed as a header at
34948 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34950 The reader is implemented as a shared object (so this functionality is
34951 not available on platforms which don't allow loading shared objects at
34952 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34953 @code{jit-reader-unload} are provided, to be used to load and unload
34954 the readers from a preconfigured directory. Once loaded, the shared
34955 object is used the parse the debug information emitted by the JIT
34959 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34960 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34963 @node Using JIT Debug Info Readers
34964 @subsection Using JIT Debug Info Readers
34965 @kindex jit-reader-load
34966 @kindex jit-reader-unload
34968 Readers can be loaded and unloaded using the @code{jit-reader-load}
34969 and @code{jit-reader-unload} commands.
34972 @item jit-reader-load @var{reader}
34973 Load the JIT reader named @var{reader}, which is a shared
34974 object specified as either an absolute or a relative file name. In
34975 the latter case, @value{GDBN} will try to load the reader from a
34976 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34977 system (here @var{libdir} is the system library directory, often
34978 @file{/usr/local/lib}).
34980 Only one reader can be active at a time; trying to load a second
34981 reader when one is already loaded will result in @value{GDBN}
34982 reporting an error. A new JIT reader can be loaded by first unloading
34983 the current one using @code{jit-reader-unload} and then invoking
34984 @code{jit-reader-load}.
34986 @item jit-reader-unload
34987 Unload the currently loaded JIT reader.
34991 @node Writing JIT Debug Info Readers
34992 @subsection Writing JIT Debug Info Readers
34993 @cindex writing JIT debug info readers
34995 As mentioned, a reader is essentially a shared object conforming to a
34996 certain ABI. This ABI is described in @file{jit-reader.h}.
34998 @file{jit-reader.h} defines the structures, macros and functions
34999 required to write a reader. It is installed (along with
35000 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
35001 the system include directory.
35003 Readers need to be released under a GPL compatible license. A reader
35004 can be declared as released under such a license by placing the macro
35005 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
35007 The entry point for readers is the symbol @code{gdb_init_reader},
35008 which is expected to be a function with the prototype
35010 @findex gdb_init_reader
35012 extern struct gdb_reader_funcs *gdb_init_reader (void);
35015 @cindex @code{struct gdb_reader_funcs}
35017 @code{struct gdb_reader_funcs} contains a set of pointers to callback
35018 functions. These functions are executed to read the debug info
35019 generated by the JIT compiler (@code{read}), to unwind stack frames
35020 (@code{unwind}) and to create canonical frame IDs
35021 (@code{get_Frame_id}). It also has a callback that is called when the
35022 reader is being unloaded (@code{destroy}). The struct looks like this
35025 struct gdb_reader_funcs
35027 /* Must be set to GDB_READER_INTERFACE_VERSION. */
35028 int reader_version;
35030 /* For use by the reader. */
35033 gdb_read_debug_info *read;
35034 gdb_unwind_frame *unwind;
35035 gdb_get_frame_id *get_frame_id;
35036 gdb_destroy_reader *destroy;
35040 @cindex @code{struct gdb_symbol_callbacks}
35041 @cindex @code{struct gdb_unwind_callbacks}
35043 The callbacks are provided with another set of callbacks by
35044 @value{GDBN} to do their job. For @code{read}, these callbacks are
35045 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
35046 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
35047 @code{struct gdb_symbol_callbacks} has callbacks to create new object
35048 files and new symbol tables inside those object files. @code{struct
35049 gdb_unwind_callbacks} has callbacks to read registers off the current
35050 frame and to write out the values of the registers in the previous
35051 frame. Both have a callback (@code{target_read}) to read bytes off the
35052 target's address space.
35054 @node In-Process Agent
35055 @chapter In-Process Agent
35056 @cindex debugging agent
35057 The traditional debugging model is conceptually low-speed, but works fine,
35058 because most bugs can be reproduced in debugging-mode execution. However,
35059 as multi-core or many-core processors are becoming mainstream, and
35060 multi-threaded programs become more and more popular, there should be more
35061 and more bugs that only manifest themselves at normal-mode execution, for
35062 example, thread races, because debugger's interference with the program's
35063 timing may conceal the bugs. On the other hand, in some applications,
35064 it is not feasible for the debugger to interrupt the program's execution
35065 long enough for the developer to learn anything helpful about its behavior.
35066 If the program's correctness depends on its real-time behavior, delays
35067 introduced by a debugger might cause the program to fail, even when the
35068 code itself is correct. It is useful to be able to observe the program's
35069 behavior without interrupting it.
35071 Therefore, traditional debugging model is too intrusive to reproduce
35072 some bugs. In order to reduce the interference with the program, we can
35073 reduce the number of operations performed by debugger. The
35074 @dfn{In-Process Agent}, a shared library, is running within the same
35075 process with inferior, and is able to perform some debugging operations
35076 itself. As a result, debugger is only involved when necessary, and
35077 performance of debugging can be improved accordingly. Note that
35078 interference with program can be reduced but can't be removed completely,
35079 because the in-process agent will still stop or slow down the program.
35081 The in-process agent can interpret and execute Agent Expressions
35082 (@pxref{Agent Expressions}) during performing debugging operations. The
35083 agent expressions can be used for different purposes, such as collecting
35084 data in tracepoints, and condition evaluation in breakpoints.
35086 @anchor{Control Agent}
35087 You can control whether the in-process agent is used as an aid for
35088 debugging with the following commands:
35091 @kindex set agent on
35093 Causes the in-process agent to perform some operations on behalf of the
35094 debugger. Just which operations requested by the user will be done
35095 by the in-process agent depends on the its capabilities. For example,
35096 if you request to evaluate breakpoint conditions in the in-process agent,
35097 and the in-process agent has such capability as well, then breakpoint
35098 conditions will be evaluated in the in-process agent.
35100 @kindex set agent off
35101 @item set agent off
35102 Disables execution of debugging operations by the in-process agent. All
35103 of the operations will be performed by @value{GDBN}.
35107 Display the current setting of execution of debugging operations by
35108 the in-process agent.
35112 * In-Process Agent Protocol::
35115 @node In-Process Agent Protocol
35116 @section In-Process Agent Protocol
35117 @cindex in-process agent protocol
35119 The in-process agent is able to communicate with both @value{GDBN} and
35120 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
35121 used for communications between @value{GDBN} or GDBserver and the IPA.
35122 In general, @value{GDBN} or GDBserver sends commands
35123 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
35124 in-process agent replies back with the return result of the command, or
35125 some other information. The data sent to in-process agent is composed
35126 of primitive data types, such as 4-byte or 8-byte type, and composite
35127 types, which are called objects (@pxref{IPA Protocol Objects}).
35130 * IPA Protocol Objects::
35131 * IPA Protocol Commands::
35134 @node IPA Protocol Objects
35135 @subsection IPA Protocol Objects
35136 @cindex ipa protocol objects
35138 The commands sent to and results received from agent may contain some
35139 complex data types called @dfn{objects}.
35141 The in-process agent is running on the same machine with @value{GDBN}
35142 or GDBserver, so it doesn't have to handle as much differences between
35143 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
35144 However, there are still some differences of two ends in two processes:
35148 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
35149 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
35151 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
35152 GDBserver is compiled with one, and in-process agent is compiled with
35156 Here are the IPA Protocol Objects:
35160 agent expression object. It represents an agent expression
35161 (@pxref{Agent Expressions}).
35162 @anchor{agent expression object}
35164 tracepoint action object. It represents a tracepoint action
35165 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
35166 memory, static trace data and to evaluate expression.
35167 @anchor{tracepoint action object}
35169 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
35170 @anchor{tracepoint object}
35174 The following table describes important attributes of each IPA protocol
35177 @multitable @columnfractions .30 .20 .50
35178 @headitem Name @tab Size @tab Description
35179 @item @emph{agent expression object} @tab @tab
35180 @item length @tab 4 @tab length of bytes code
35181 @item byte code @tab @var{length} @tab contents of byte code
35182 @item @emph{tracepoint action for collecting memory} @tab @tab
35183 @item 'M' @tab 1 @tab type of tracepoint action
35184 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
35185 address of the lowest byte to collect, otherwise @var{addr} is the offset
35186 of @var{basereg} for memory collecting.
35187 @item len @tab 8 @tab length of memory for collecting
35188 @item basereg @tab 4 @tab the register number containing the starting
35189 memory address for collecting.
35190 @item @emph{tracepoint action for collecting registers} @tab @tab
35191 @item 'R' @tab 1 @tab type of tracepoint action
35192 @item @emph{tracepoint action for collecting static trace data} @tab @tab
35193 @item 'L' @tab 1 @tab type of tracepoint action
35194 @item @emph{tracepoint action for expression evaluation} @tab @tab
35195 @item 'X' @tab 1 @tab type of tracepoint action
35196 @item agent expression @tab length of @tab @ref{agent expression object}
35197 @item @emph{tracepoint object} @tab @tab
35198 @item number @tab 4 @tab number of tracepoint
35199 @item address @tab 8 @tab address of tracepoint inserted on
35200 @item type @tab 4 @tab type of tracepoint
35201 @item enabled @tab 1 @tab enable or disable of tracepoint
35202 @item step_count @tab 8 @tab step
35203 @item pass_count @tab 8 @tab pass
35204 @item numactions @tab 4 @tab number of tracepoint actions
35205 @item hit count @tab 8 @tab hit count
35206 @item trace frame usage @tab 8 @tab trace frame usage
35207 @item compiled_cond @tab 8 @tab compiled condition
35208 @item orig_size @tab 8 @tab orig size
35209 @item condition @tab 4 if condition is NULL otherwise length of
35210 @ref{agent expression object}
35211 @tab zero if condition is NULL, otherwise is
35212 @ref{agent expression object}
35213 @item actions @tab variable
35214 @tab numactions number of @ref{tracepoint action object}
35217 @node IPA Protocol Commands
35218 @subsection IPA Protocol Commands
35219 @cindex ipa protocol commands
35221 The spaces in each command are delimiters to ease reading this commands
35222 specification. They don't exist in real commands.
35226 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
35227 Installs a new fast tracepoint described by @var{tracepoint_object}
35228 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
35229 head of @dfn{jumppad}, which is used to jump to data collection routine
35234 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
35235 @var{target_address} is address of tracepoint in the inferior.
35236 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
35237 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
35238 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
35239 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
35246 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
35247 is about to kill inferiors.
35255 @item probe_marker_at:@var{address}
35256 Asks in-process agent to probe the marker at @var{address}.
35263 @item unprobe_marker_at:@var{address}
35264 Asks in-process agent to unprobe the marker at @var{address}.
35268 @chapter Reporting Bugs in @value{GDBN}
35269 @cindex bugs in @value{GDBN}
35270 @cindex reporting bugs in @value{GDBN}
35272 Your bug reports play an essential role in making @value{GDBN} reliable.
35274 Reporting a bug may help you by bringing a solution to your problem, or it
35275 may not. But in any case the principal function of a bug report is to help
35276 the entire community by making the next version of @value{GDBN} work better. Bug
35277 reports are your contribution to the maintenance of @value{GDBN}.
35279 In order for a bug report to serve its purpose, you must include the
35280 information that enables us to fix the bug.
35283 * Bug Criteria:: Have you found a bug?
35284 * Bug Reporting:: How to report bugs
35288 @section Have You Found a Bug?
35289 @cindex bug criteria
35291 If you are not sure whether you have found a bug, here are some guidelines:
35294 @cindex fatal signal
35295 @cindex debugger crash
35296 @cindex crash of debugger
35298 If the debugger gets a fatal signal, for any input whatever, that is a
35299 @value{GDBN} bug. Reliable debuggers never crash.
35301 @cindex error on valid input
35303 If @value{GDBN} produces an error message for valid input, that is a
35304 bug. (Note that if you're cross debugging, the problem may also be
35305 somewhere in the connection to the target.)
35307 @cindex invalid input
35309 If @value{GDBN} does not produce an error message for invalid input,
35310 that is a bug. However, you should note that your idea of
35311 ``invalid input'' might be our idea of ``an extension'' or ``support
35312 for traditional practice''.
35315 If you are an experienced user of debugging tools, your suggestions
35316 for improvement of @value{GDBN} are welcome in any case.
35319 @node Bug Reporting
35320 @section How to Report Bugs
35321 @cindex bug reports
35322 @cindex @value{GDBN} bugs, reporting
35324 A number of companies and individuals offer support for @sc{gnu} products.
35325 If you obtained @value{GDBN} from a support organization, we recommend you
35326 contact that organization first.
35328 You can find contact information for many support companies and
35329 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
35331 @c should add a web page ref...
35334 @ifset BUGURL_DEFAULT
35335 In any event, we also recommend that you submit bug reports for
35336 @value{GDBN}. The preferred method is to submit them directly using
35337 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
35338 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
35341 @strong{Do not send bug reports to @samp{info-gdb}, or to
35342 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
35343 not want to receive bug reports. Those that do have arranged to receive
35346 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
35347 serves as a repeater. The mailing list and the newsgroup carry exactly
35348 the same messages. Often people think of posting bug reports to the
35349 newsgroup instead of mailing them. This appears to work, but it has one
35350 problem which can be crucial: a newsgroup posting often lacks a mail
35351 path back to the sender. Thus, if we need to ask for more information,
35352 we may be unable to reach you. For this reason, it is better to send
35353 bug reports to the mailing list.
35355 @ifclear BUGURL_DEFAULT
35356 In any event, we also recommend that you submit bug reports for
35357 @value{GDBN} to @value{BUGURL}.
35361 The fundamental principle of reporting bugs usefully is this:
35362 @strong{report all the facts}. If you are not sure whether to state a
35363 fact or leave it out, state it!
35365 Often people omit facts because they think they know what causes the
35366 problem and assume that some details do not matter. Thus, you might
35367 assume that the name of the variable you use in an example does not matter.
35368 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
35369 stray memory reference which happens to fetch from the location where that
35370 name is stored in memory; perhaps, if the name were different, the contents
35371 of that location would fool the debugger into doing the right thing despite
35372 the bug. Play it safe and give a specific, complete example. That is the
35373 easiest thing for you to do, and the most helpful.
35375 Keep in mind that the purpose of a bug report is to enable us to fix the
35376 bug. It may be that the bug has been reported previously, but neither
35377 you nor we can know that unless your bug report is complete and
35380 Sometimes people give a few sketchy facts and ask, ``Does this ring a
35381 bell?'' Those bug reports are useless, and we urge everyone to
35382 @emph{refuse to respond to them} except to chide the sender to report
35385 To enable us to fix the bug, you should include all these things:
35389 The version of @value{GDBN}. @value{GDBN} announces it if you start
35390 with no arguments; you can also print it at any time using @code{show
35393 Without this, we will not know whether there is any point in looking for
35394 the bug in the current version of @value{GDBN}.
35397 The type of machine you are using, and the operating system name and
35401 The details of the @value{GDBN} build-time configuration.
35402 @value{GDBN} shows these details if you invoke it with the
35403 @option{--configuration} command-line option, or if you type
35404 @code{show configuration} at @value{GDBN}'s prompt.
35407 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
35408 ``@value{GCC}--2.8.1''.
35411 What compiler (and its version) was used to compile the program you are
35412 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
35413 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
35414 to get this information; for other compilers, see the documentation for
35418 The command arguments you gave the compiler to compile your example and
35419 observe the bug. For example, did you use @samp{-O}? To guarantee
35420 you will not omit something important, list them all. A copy of the
35421 Makefile (or the output from make) is sufficient.
35423 If we were to try to guess the arguments, we would probably guess wrong
35424 and then we might not encounter the bug.
35427 A complete input script, and all necessary source files, that will
35431 A description of what behavior you observe that you believe is
35432 incorrect. For example, ``It gets a fatal signal.''
35434 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
35435 will certainly notice it. But if the bug is incorrect output, we might
35436 not notice unless it is glaringly wrong. You might as well not give us
35437 a chance to make a mistake.
35439 Even if the problem you experience is a fatal signal, you should still
35440 say so explicitly. Suppose something strange is going on, such as, your
35441 copy of @value{GDBN} is out of synch, or you have encountered a bug in
35442 the C library on your system. (This has happened!) Your copy might
35443 crash and ours would not. If you told us to expect a crash, then when
35444 ours fails to crash, we would know that the bug was not happening for
35445 us. If you had not told us to expect a crash, then we would not be able
35446 to draw any conclusion from our observations.
35449 @cindex recording a session script
35450 To collect all this information, you can use a session recording program
35451 such as @command{script}, which is available on many Unix systems.
35452 Just run your @value{GDBN} session inside @command{script} and then
35453 include the @file{typescript} file with your bug report.
35455 Another way to record a @value{GDBN} session is to run @value{GDBN}
35456 inside Emacs and then save the entire buffer to a file.
35459 If you wish to suggest changes to the @value{GDBN} source, send us context
35460 diffs. If you even discuss something in the @value{GDBN} source, refer to
35461 it by context, not by line number.
35463 The line numbers in our development sources will not match those in your
35464 sources. Your line numbers would convey no useful information to us.
35468 Here are some things that are not necessary:
35472 A description of the envelope of the bug.
35474 Often people who encounter a bug spend a lot of time investigating
35475 which changes to the input file will make the bug go away and which
35476 changes will not affect it.
35478 This is often time consuming and not very useful, because the way we
35479 will find the bug is by running a single example under the debugger
35480 with breakpoints, not by pure deduction from a series of examples.
35481 We recommend that you save your time for something else.
35483 Of course, if you can find a simpler example to report @emph{instead}
35484 of the original one, that is a convenience for us. Errors in the
35485 output will be easier to spot, running under the debugger will take
35486 less time, and so on.
35488 However, simplification is not vital; if you do not want to do this,
35489 report the bug anyway and send us the entire test case you used.
35492 A patch for the bug.
35494 A patch for the bug does help us if it is a good one. But do not omit
35495 the necessary information, such as the test case, on the assumption that
35496 a patch is all we need. We might see problems with your patch and decide
35497 to fix the problem another way, or we might not understand it at all.
35499 Sometimes with a program as complicated as @value{GDBN} it is very hard to
35500 construct an example that will make the program follow a certain path
35501 through the code. If you do not send us the example, we will not be able
35502 to construct one, so we will not be able to verify that the bug is fixed.
35504 And if we cannot understand what bug you are trying to fix, or why your
35505 patch should be an improvement, we will not install it. A test case will
35506 help us to understand.
35509 A guess about what the bug is or what it depends on.
35511 Such guesses are usually wrong. Even we cannot guess right about such
35512 things without first using the debugger to find the facts.
35515 @c The readline documentation is distributed with the readline code
35516 @c and consists of the two following files:
35519 @c Use -I with makeinfo to point to the appropriate directory,
35520 @c environment var TEXINPUTS with TeX.
35521 @ifclear SYSTEM_READLINE
35522 @include rluser.texi
35523 @include hsuser.texi
35527 @appendix In Memoriam
35529 The @value{GDBN} project mourns the loss of the following long-time
35534 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
35535 to Free Software in general. Outside of @value{GDBN}, he was known in
35536 the Amiga world for his series of Fish Disks, and the GeekGadget project.
35538 @item Michael Snyder
35539 Michael was one of the Global Maintainers of the @value{GDBN} project,
35540 with contributions recorded as early as 1996, until 2011. In addition
35541 to his day to day participation, he was a large driving force behind
35542 adding Reverse Debugging to @value{GDBN}.
35545 Beyond their technical contributions to the project, they were also
35546 enjoyable members of the Free Software Community. We will miss them.
35548 @node Formatting Documentation
35549 @appendix Formatting Documentation
35551 @cindex @value{GDBN} reference card
35552 @cindex reference card
35553 The @value{GDBN} 4 release includes an already-formatted reference card, ready
35554 for printing with PostScript or Ghostscript, in the @file{gdb}
35555 subdirectory of the main source directory@footnote{In
35556 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
35557 release.}. If you can use PostScript or Ghostscript with your printer,
35558 you can print the reference card immediately with @file{refcard.ps}.
35560 The release also includes the source for the reference card. You
35561 can format it, using @TeX{}, by typing:
35567 The @value{GDBN} reference card is designed to print in @dfn{landscape}
35568 mode on US ``letter'' size paper;
35569 that is, on a sheet 11 inches wide by 8.5 inches
35570 high. You will need to specify this form of printing as an option to
35571 your @sc{dvi} output program.
35573 @cindex documentation
35575 All the documentation for @value{GDBN} comes as part of the machine-readable
35576 distribution. The documentation is written in Texinfo format, which is
35577 a documentation system that uses a single source file to produce both
35578 on-line information and a printed manual. You can use one of the Info
35579 formatting commands to create the on-line version of the documentation
35580 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
35582 @value{GDBN} includes an already formatted copy of the on-line Info
35583 version of this manual in the @file{gdb} subdirectory. The main Info
35584 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
35585 subordinate files matching @samp{gdb.info*} in the same directory. If
35586 necessary, you can print out these files, or read them with any editor;
35587 but they are easier to read using the @code{info} subsystem in @sc{gnu}
35588 Emacs or the standalone @code{info} program, available as part of the
35589 @sc{gnu} Texinfo distribution.
35591 If you want to format these Info files yourself, you need one of the
35592 Info formatting programs, such as @code{texinfo-format-buffer} or
35595 If you have @code{makeinfo} installed, and are in the top level
35596 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
35597 version @value{GDBVN}), you can make the Info file by typing:
35604 If you want to typeset and print copies of this manual, you need @TeX{},
35605 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
35606 Texinfo definitions file.
35608 @TeX{} is a typesetting program; it does not print files directly, but
35609 produces output files called @sc{dvi} files. To print a typeset
35610 document, you need a program to print @sc{dvi} files. If your system
35611 has @TeX{} installed, chances are it has such a program. The precise
35612 command to use depends on your system; @kbd{lpr -d} is common; another
35613 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
35614 require a file name without any extension or a @samp{.dvi} extension.
35616 @TeX{} also requires a macro definitions file called
35617 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
35618 written in Texinfo format. On its own, @TeX{} cannot either read or
35619 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
35620 and is located in the @file{gdb-@var{version-number}/texinfo}
35623 If you have @TeX{} and a @sc{dvi} printer program installed, you can
35624 typeset and print this manual. First switch to the @file{gdb}
35625 subdirectory of the main source directory (for example, to
35626 @file{gdb-@value{GDBVN}/gdb}) and type:
35632 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
35634 @node Installing GDB
35635 @appendix Installing @value{GDBN}
35636 @cindex installation
35639 * Requirements:: Requirements for building @value{GDBN}
35640 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
35641 * Separate Objdir:: Compiling @value{GDBN} in another directory
35642 * Config Names:: Specifying names for hosts and targets
35643 * Configure Options:: Summary of options for configure
35644 * System-wide configuration:: Having a system-wide init file
35648 @section Requirements for Building @value{GDBN}
35649 @cindex building @value{GDBN}, requirements for
35651 Building @value{GDBN} requires various tools and packages to be available.
35652 Other packages will be used only if they are found.
35654 @heading Tools/Packages Necessary for Building @value{GDBN}
35656 @item C@t{++}11 compiler
35657 @value{GDBN} is written in C@t{++}11. It should be buildable with any
35658 recent C@t{++}11 compiler, e.g.@: GCC.
35661 @value{GDBN}'s build system relies on features only found in the GNU
35662 make program. Other variants of @code{make} will not work.
35665 @heading Tools/Packages Optional for Building @value{GDBN}
35669 @value{GDBN} can use the Expat XML parsing library. This library may be
35670 included with your operating system distribution; if it is not, you
35671 can get the latest version from @url{http://expat.sourceforge.net}.
35672 The @file{configure} script will search for this library in several
35673 standard locations; if it is installed in an unusual path, you can
35674 use the @option{--with-libexpat-prefix} option to specify its location.
35680 Remote protocol memory maps (@pxref{Memory Map Format})
35682 Target descriptions (@pxref{Target Descriptions})
35684 Remote shared library lists (@xref{Library List Format},
35685 or alternatively @pxref{Library List Format for SVR4 Targets})
35687 MS-Windows shared libraries (@pxref{Shared Libraries})
35689 Traceframe info (@pxref{Traceframe Info Format})
35691 Branch trace (@pxref{Branch Trace Format},
35692 @pxref{Branch Trace Configuration Format})
35696 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
35697 default, @value{GDBN} will be compiled if the Guile libraries are
35698 installed and are found by @file{configure}. You can use the
35699 @code{--with-guile} option to request Guile, and pass either the Guile
35700 version number or the file name of the relevant @code{pkg-config}
35701 program to choose a particular version of Guile.
35704 @value{GDBN}'s features related to character sets (@pxref{Character
35705 Sets}) require a functioning @code{iconv} implementation. If you are
35706 on a GNU system, then this is provided by the GNU C Library. Some
35707 other systems also provide a working @code{iconv}.
35709 If @value{GDBN} is using the @code{iconv} program which is installed
35710 in a non-standard place, you will need to tell @value{GDBN} where to
35711 find it. This is done with @option{--with-iconv-bin} which specifies
35712 the directory that contains the @code{iconv} program. This program is
35713 run in order to make a list of the available character sets.
35715 On systems without @code{iconv}, you can install GNU Libiconv. If
35716 Libiconv is installed in a standard place, @value{GDBN} will
35717 automatically use it if it is needed. If you have previously
35718 installed Libiconv in a non-standard place, you can use the
35719 @option{--with-libiconv-prefix} option to @file{configure}.
35721 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
35722 arrange to build Libiconv if a directory named @file{libiconv} appears
35723 in the top-most source directory. If Libiconv is built this way, and
35724 if the operating system does not provide a suitable @code{iconv}
35725 implementation, then the just-built library will automatically be used
35726 by @value{GDBN}. One easy way to set this up is to download GNU
35727 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
35728 source tree, and then rename the directory holding the Libiconv source
35729 code to @samp{libiconv}.
35732 @value{GDBN} can support debugging sections that are compressed with
35733 the LZMA library. @xref{MiniDebugInfo}. If this library is not
35734 included with your operating system, you can find it in the xz package
35735 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
35736 the usual place, then the @file{configure} script will use it
35737 automatically. If it is installed in an unusual path, you can use the
35738 @option{--with-lzma-prefix} option to specify its location.
35742 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
35743 library. This library may be included with your operating system
35744 distribution; if it is not, you can get the latest version from
35745 @url{http://www.mpfr.org}. The @file{configure} script will search
35746 for this library in several standard locations; if it is installed
35747 in an unusual path, you can use the @option{--with-libmpfr-prefix}
35748 option to specify its location.
35750 GNU MPFR is used to emulate target floating-point arithmetic during
35751 expression evaluation when the target uses different floating-point
35752 formats than the host. If GNU MPFR it is not available, @value{GDBN}
35753 will fall back to using host floating-point arithmetic.
35756 @value{GDBN} can be scripted using Python language. @xref{Python}.
35757 By default, @value{GDBN} will be compiled if the Python libraries are
35758 installed and are found by @file{configure}. You can use the
35759 @code{--with-python} option to request Python, and pass either the
35760 file name of the relevant @code{python} executable, or the name of the
35761 directory in which Python is installed, to choose a particular
35762 installation of Python.
35765 @cindex compressed debug sections
35766 @value{GDBN} will use the @samp{zlib} library, if available, to read
35767 compressed debug sections. Some linkers, such as GNU gold, are capable
35768 of producing binaries with compressed debug sections. If @value{GDBN}
35769 is compiled with @samp{zlib}, it will be able to read the debug
35770 information in such binaries.
35772 The @samp{zlib} library is likely included with your operating system
35773 distribution; if it is not, you can get the latest version from
35774 @url{http://zlib.net}.
35777 @node Running Configure
35778 @section Invoking the @value{GDBN} @file{configure} Script
35779 @cindex configuring @value{GDBN}
35780 @value{GDBN} comes with a @file{configure} script that automates the process
35781 of preparing @value{GDBN} for installation; you can then use @code{make} to
35782 build the @code{gdb} program.
35784 @c irrelevant in info file; it's as current as the code it lives with.
35785 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
35786 look at the @file{README} file in the sources; we may have improved the
35787 installation procedures since publishing this manual.}
35790 The @value{GDBN} distribution includes all the source code you need for
35791 @value{GDBN} in a single directory, whose name is usually composed by
35792 appending the version number to @samp{gdb}.
35794 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
35795 @file{gdb-@value{GDBVN}} directory. That directory contains:
35798 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
35799 script for configuring @value{GDBN} and all its supporting libraries
35801 @item gdb-@value{GDBVN}/gdb
35802 the source specific to @value{GDBN} itself
35804 @item gdb-@value{GDBVN}/bfd
35805 source for the Binary File Descriptor library
35807 @item gdb-@value{GDBVN}/include
35808 @sc{gnu} include files
35810 @item gdb-@value{GDBVN}/libiberty
35811 source for the @samp{-liberty} free software library
35813 @item gdb-@value{GDBVN}/opcodes
35814 source for the library of opcode tables and disassemblers
35816 @item gdb-@value{GDBVN}/readline
35817 source for the @sc{gnu} command-line interface
35820 There may be other subdirectories as well.
35822 The simplest way to configure and build @value{GDBN} is to run @file{configure}
35823 from the @file{gdb-@var{version-number}} source directory, which in
35824 this example is the @file{gdb-@value{GDBVN}} directory.
35826 First switch to the @file{gdb-@var{version-number}} source directory
35827 if you are not already in it; then run @file{configure}. Pass the
35828 identifier for the platform on which @value{GDBN} will run as an
35834 cd gdb-@value{GDBVN}
35839 Running @samp{configure} and then running @code{make} builds the
35840 included supporting libraries, then @code{gdb} itself. The configured
35841 source files, and the binaries, are left in the corresponding source
35845 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
35846 system does not recognize this automatically when you run a different
35847 shell, you may need to run @code{sh} on it explicitly:
35853 You should run the @file{configure} script from the top directory in the
35854 source tree, the @file{gdb-@var{version-number}} directory. If you run
35855 @file{configure} from one of the subdirectories, you will configure only
35856 that subdirectory. That is usually not what you want. In particular,
35857 if you run the first @file{configure} from the @file{gdb} subdirectory
35858 of the @file{gdb-@var{version-number}} directory, you will omit the
35859 configuration of @file{bfd}, @file{readline}, and other sibling
35860 directories of the @file{gdb} subdirectory. This leads to build errors
35861 about missing include files such as @file{bfd/bfd.h}.
35863 You can install @code{@value{GDBN}} anywhere. The best way to do this
35864 is to pass the @code{--prefix} option to @code{configure}, and then
35865 install it with @code{make install}.
35867 @node Separate Objdir
35868 @section Compiling @value{GDBN} in Another Directory
35870 If you want to run @value{GDBN} versions for several host or target machines,
35871 you need a different @code{gdb} compiled for each combination of
35872 host and target. @file{configure} is designed to make this easy by
35873 allowing you to generate each configuration in a separate subdirectory,
35874 rather than in the source directory. If your @code{make} program
35875 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
35876 @code{make} in each of these directories builds the @code{gdb}
35877 program specified there.
35879 To build @code{gdb} in a separate directory, run @file{configure}
35880 with the @samp{--srcdir} option to specify where to find the source.
35881 (You also need to specify a path to find @file{configure}
35882 itself from your working directory. If the path to @file{configure}
35883 would be the same as the argument to @samp{--srcdir}, you can leave out
35884 the @samp{--srcdir} option; it is assumed.)
35886 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
35887 separate directory for a Sun 4 like this:
35891 cd gdb-@value{GDBVN}
35894 ../gdb-@value{GDBVN}/configure
35899 When @file{configure} builds a configuration using a remote source
35900 directory, it creates a tree for the binaries with the same structure
35901 (and using the same names) as the tree under the source directory. In
35902 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35903 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35904 @file{gdb-sun4/gdb}.
35906 Make sure that your path to the @file{configure} script has just one
35907 instance of @file{gdb} in it. If your path to @file{configure} looks
35908 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35909 one subdirectory of @value{GDBN}, not the whole package. This leads to
35910 build errors about missing include files such as @file{bfd/bfd.h}.
35912 One popular reason to build several @value{GDBN} configurations in separate
35913 directories is to configure @value{GDBN} for cross-compiling (where
35914 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35915 programs that run on another machine---the @dfn{target}).
35916 You specify a cross-debugging target by
35917 giving the @samp{--target=@var{target}} option to @file{configure}.
35919 When you run @code{make} to build a program or library, you must run
35920 it in a configured directory---whatever directory you were in when you
35921 called @file{configure} (or one of its subdirectories).
35923 The @code{Makefile} that @file{configure} generates in each source
35924 directory also runs recursively. If you type @code{make} in a source
35925 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35926 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35927 will build all the required libraries, and then build GDB.
35929 When you have multiple hosts or targets configured in separate
35930 directories, you can run @code{make} on them in parallel (for example,
35931 if they are NFS-mounted on each of the hosts); they will not interfere
35935 @section Specifying Names for Hosts and Targets
35937 The specifications used for hosts and targets in the @file{configure}
35938 script are based on a three-part naming scheme, but some short predefined
35939 aliases are also supported. The full naming scheme encodes three pieces
35940 of information in the following pattern:
35943 @var{architecture}-@var{vendor}-@var{os}
35946 For example, you can use the alias @code{sun4} as a @var{host} argument,
35947 or as the value for @var{target} in a @code{--target=@var{target}}
35948 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35950 The @file{configure} script accompanying @value{GDBN} does not provide
35951 any query facility to list all supported host and target names or
35952 aliases. @file{configure} calls the Bourne shell script
35953 @code{config.sub} to map abbreviations to full names; you can read the
35954 script, if you wish, or you can use it to test your guesses on
35955 abbreviations---for example:
35958 % sh config.sub i386-linux
35960 % sh config.sub alpha-linux
35961 alpha-unknown-linux-gnu
35962 % sh config.sub hp9k700
35964 % sh config.sub sun4
35965 sparc-sun-sunos4.1.1
35966 % sh config.sub sun3
35967 m68k-sun-sunos4.1.1
35968 % sh config.sub i986v
35969 Invalid configuration `i986v': machine `i986v' not recognized
35973 @code{config.sub} is also distributed in the @value{GDBN} source
35974 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35976 @node Configure Options
35977 @section @file{configure} Options
35979 Here is a summary of the @file{configure} options and arguments that
35980 are most often useful for building @value{GDBN}. @file{configure}
35981 also has several other options not listed here. @inforef{Running
35982 configure scripts,,autoconf.info}, for a full
35983 explanation of @file{configure}.
35986 configure @r{[}--help@r{]}
35987 @r{[}--prefix=@var{dir}@r{]}
35988 @r{[}--exec-prefix=@var{dir}@r{]}
35989 @r{[}--srcdir=@var{dirname}@r{]}
35990 @r{[}--target=@var{target}@r{]}
35994 You may introduce options with a single @samp{-} rather than
35995 @samp{--} if you prefer; but you may abbreviate option names if you use
36000 Display a quick summary of how to invoke @file{configure}.
36002 @item --prefix=@var{dir}
36003 Configure the source to install programs and files under directory
36006 @item --exec-prefix=@var{dir}
36007 Configure the source to install programs under directory
36010 @c avoid splitting the warning from the explanation:
36012 @item --srcdir=@var{dirname}
36013 Use this option to make configurations in directories separate from the
36014 @value{GDBN} source directories. Among other things, you can use this to
36015 build (or maintain) several configurations simultaneously, in separate
36016 directories. @file{configure} writes configuration-specific files in
36017 the current directory, but arranges for them to use the source in the
36018 directory @var{dirname}. @file{configure} creates directories under
36019 the working directory in parallel to the source directories below
36022 @item --target=@var{target}
36023 Configure @value{GDBN} for cross-debugging programs running on the specified
36024 @var{target}. Without this option, @value{GDBN} is configured to debug
36025 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
36027 There is no convenient way to generate a list of all available
36028 targets. Also see the @code{--enable-targets} option, below.
36031 There are many other options that are specific to @value{GDBN}. This
36032 lists just the most common ones; there are some very specialized
36033 options not described here.
36036 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
36037 @itemx --enable-targets=all
36038 Configure @value{GDBN} for cross-debugging programs running on the
36039 specified list of targets. The special value @samp{all} configures
36040 @value{GDBN} for debugging programs running on any target it supports.
36042 @item --with-gdb-datadir=@var{path}
36043 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
36044 here for certain supporting files or scripts. This defaults to the
36045 @file{gdb} subdirectory of @samp{datadi} (which can be set using
36048 @item --with-relocated-sources=@var{dir}
36049 Sets up the default source path substitution rule so that directory
36050 names recorded in debug information will be automatically adjusted for
36051 any directory under @var{dir}. @var{dir} should be a subdirectory of
36052 @value{GDBN}'s configured prefix, the one mentioned in the
36053 @code{--prefix} or @code{--exec-prefix} options to configure. This
36054 option is useful if GDB is supposed to be moved to a different place
36057 @item --enable-64-bit-bfd
36058 Enable 64-bit support in BFD on 32-bit hosts.
36060 @item --disable-gdbmi
36061 Build @value{GDBN} without the GDB/MI machine interface
36065 Build @value{GDBN} with the text-mode full-screen user interface
36066 (TUI). Requires a curses library (ncurses and cursesX are also
36069 @item --with-curses
36070 Use the curses library instead of the termcap library, for text-mode
36071 terminal operations.
36073 @item --with-libunwind-ia64
36074 Use the libunwind library for unwinding function call stack on ia64
36075 target platforms. See http://www.nongnu.org/libunwind/index.html for
36078 @item --with-system-readline
36079 Use the readline library installed on the host, rather than the
36080 library supplied as part of @value{GDBN}.
36082 @item --with-system-zlib
36083 Use the zlib library installed on the host, rather than the library
36084 supplied as part of @value{GDBN}.
36087 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
36088 default if libexpat is installed and found at configure time.) This
36089 library is used to read XML files supplied with @value{GDBN}. If it
36090 is unavailable, some features, such as remote protocol memory maps,
36091 target descriptions, and shared library lists, that are based on XML
36092 files, will not be available in @value{GDBN}. If your host does not
36093 have libexpat installed, you can get the latest version from
36094 `http://expat.sourceforge.net'.
36096 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
36098 Build @value{GDBN} with GNU libiconv, a character set encoding
36099 conversion library. This is not done by default, as on GNU systems
36100 the @code{iconv} that is built in to the C library is sufficient. If
36101 your host does not have a working @code{iconv}, you can get the latest
36102 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
36104 @value{GDBN}'s build system also supports building GNU libiconv as
36105 part of the overall build. @xref{Requirements}.
36108 Build @value{GDBN} with LZMA, a compression library. (Done by default
36109 if liblzma is installed and found at configure time.) LZMA is used by
36110 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
36111 platforms using the ELF object file format. If your host does not
36112 have liblzma installed, you can get the latest version from
36113 `https://tukaani.org/xz/'.
36116 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
36117 floating-point computation with correct rounding. (Done by default if
36118 GNU MPFR is installed and found at configure time.) This library is
36119 used to emulate target floating-point arithmetic during expression
36120 evaluation when the target uses different floating-point formats than
36121 the host. If GNU MPFR is not available, @value{GDBN} will fall back
36122 to using host floating-point arithmetic. If your host does not have
36123 GNU MPFR installed, you can get the latest version from
36124 `http://www.mpfr.org'.
36126 @item --with-python@r{[}=@var{python}@r{]}
36127 Build @value{GDBN} with Python scripting support. (Done by default if
36128 libpython is present and found at configure time.) Python makes
36129 @value{GDBN} scripting much more powerful than the restricted CLI
36130 scripting language. If your host does not have Python installed, you
36131 can find it on `http://www.python.org/download/'. The oldest version
36132 of Python supported by GDB is 2.6. The optional argument @var{python}
36133 is used to find the Python headers and libraries. It can be either
36134 the name of a Python executable, or the name of the directory in which
36135 Python is installed.
36137 @item --with-guile[=GUILE]'
36138 Build @value{GDBN} with GNU Guile scripting support. (Done by default
36139 if libguile is present and found at configure time.) If your host
36140 does not have Guile installed, you can find it at
36141 `https://www.gnu.org/software/guile/'. The optional argument GUILE
36142 can be a version number, which will cause @code{configure} to try to
36143 use that version of Guile; or the file name of a @code{pkg-config}
36144 executable, which will be queried to find the information needed to
36145 compile and link against Guile.
36147 @item --without-included-regex
36148 Don't use the regex library included with @value{GDBN} (as part of the
36149 libiberty library). This is the default on hosts with version 2 of
36152 @item --with-sysroot=@var{dir}
36153 Use @var{dir} as the default system root directory for libraries whose
36154 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
36155 @var{dir} can be modified at run time by using the @command{set
36156 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
36157 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
36158 default system root will be automatically adjusted if and when
36159 @value{GDBN} is moved to a different location.
36161 @item --with-system-gdbinit=@var{file}
36162 Configure @value{GDBN} to automatically load a system-wide init file.
36163 @var{file} should be an absolute file name. If @var{file} is in a
36164 directory under the configured prefix, and @value{GDBN} is moved to
36165 another location after being built, the location of the system-wide
36166 init file will be adjusted accordingly.
36168 @item --enable-build-warnings
36169 When building the @value{GDBN} sources, ask the compiler to warn about
36170 any code which looks even vaguely suspicious. It passes many
36171 different warning flags, depending on the exact version of the
36172 compiler you are using.
36174 @item --enable-werror
36175 Treat compiler warnings as werrors. It adds the @code{-Werror} flag
36176 to the compiler, which will fail the compilation if the compiler
36177 outputs any warning messages.
36179 @item --enable-ubsan
36180 Enable the GCC undefined behavior sanitizer. This is disabled by
36181 default, but passing @code{--enable-ubsan=yes} or
36182 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
36183 undefined behavior sanitizer checks for C@t{++} undefined behavior.
36184 It has a performance cost, so if you are looking at @value{GDBN}'s
36185 performance, you should disable it. The undefined behavior sanitizer
36186 was first introduced in GCC 4.9.
36189 @node System-wide configuration
36190 @section System-wide configuration and settings
36191 @cindex system-wide init file
36193 @value{GDBN} can be configured to have a system-wide init file;
36194 this file will be read and executed at startup (@pxref{Startup, , What
36195 @value{GDBN} does during startup}).
36197 Here is the corresponding configure option:
36200 @item --with-system-gdbinit=@var{file}
36201 Specify that the default location of the system-wide init file is
36205 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
36206 it may be subject to relocation. Two possible cases:
36210 If the default location of this init file contains @file{$prefix},
36211 it will be subject to relocation. Suppose that the configure options
36212 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
36213 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
36214 init file is looked for as @file{$install/etc/gdbinit} instead of
36215 @file{$prefix/etc/gdbinit}.
36218 By contrast, if the default location does not contain the prefix,
36219 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
36220 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
36221 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
36222 wherever @value{GDBN} is installed.
36225 If the configured location of the system-wide init file (as given by the
36226 @option{--with-system-gdbinit} option at configure time) is in the
36227 data-directory (as specified by @option{--with-gdb-datadir} at configure
36228 time) or in one of its subdirectories, then @value{GDBN} will look for the
36229 system-wide init file in the directory specified by the
36230 @option{--data-directory} command-line option.
36231 Note that the system-wide init file is only read once, during @value{GDBN}
36232 initialization. If the data-directory is changed after @value{GDBN} has
36233 started with the @code{set data-directory} command, the file will not be
36237 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
36240 @node System-wide Configuration Scripts
36241 @subsection Installed System-wide Configuration Scripts
36242 @cindex system-wide configuration scripts
36244 The @file{system-gdbinit} directory, located inside the data-directory
36245 (as specified by @option{--with-gdb-datadir} at configure time) contains
36246 a number of scripts which can be used as system-wide init files. To
36247 automatically source those scripts at startup, @value{GDBN} should be
36248 configured with @option{--with-system-gdbinit}. Otherwise, any user
36249 should be able to source them by hand as needed.
36251 The following scripts are currently available:
36254 @item @file{elinos.py}
36256 @cindex ELinOS system-wide configuration script
36257 This script is useful when debugging a program on an ELinOS target.
36258 It takes advantage of the environment variables defined in a standard
36259 ELinOS environment in order to determine the location of the system
36260 shared libraries, and then sets the @samp{solib-absolute-prefix}
36261 and @samp{solib-search-path} variables appropriately.
36263 @item @file{wrs-linux.py}
36264 @pindex wrs-linux.py
36265 @cindex Wind River Linux system-wide configuration script
36266 This script is useful when debugging a program on a target running
36267 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
36268 the host-side sysroot used by the target system.
36272 @node Maintenance Commands
36273 @appendix Maintenance Commands
36274 @cindex maintenance commands
36275 @cindex internal commands
36277 In addition to commands intended for @value{GDBN} users, @value{GDBN}
36278 includes a number of commands intended for @value{GDBN} developers,
36279 that are not documented elsewhere in this manual. These commands are
36280 provided here for reference. (For commands that turn on debugging
36281 messages, see @ref{Debugging Output}.)
36284 @kindex maint agent
36285 @kindex maint agent-eval
36286 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36287 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36288 Translate the given @var{expression} into remote agent bytecodes.
36289 This command is useful for debugging the Agent Expression mechanism
36290 (@pxref{Agent Expressions}). The @samp{agent} version produces an
36291 expression useful for data collection, such as by tracepoints, while
36292 @samp{maint agent-eval} produces an expression that evaluates directly
36293 to a result. For instance, a collection expression for @code{globa +
36294 globb} will include bytecodes to record four bytes of memory at each
36295 of the addresses of @code{globa} and @code{globb}, while discarding
36296 the result of the addition, while an evaluation expression will do the
36297 addition and return the sum.
36298 If @code{-at} is given, generate remote agent bytecode for @var{location}.
36299 If not, generate remote agent bytecode for current frame PC address.
36301 @kindex maint agent-printf
36302 @item maint agent-printf @var{format},@var{expr},...
36303 Translate the given format string and list of argument expressions
36304 into remote agent bytecodes and display them as a disassembled list.
36305 This command is useful for debugging the agent version of dynamic
36306 printf (@pxref{Dynamic Printf}).
36308 @kindex maint info breakpoints
36309 @item @anchor{maint info breakpoints}maint info breakpoints
36310 Using the same format as @samp{info breakpoints}, display both the
36311 breakpoints you've set explicitly, and those @value{GDBN} is using for
36312 internal purposes. Internal breakpoints are shown with negative
36313 breakpoint numbers. The type column identifies what kind of breakpoint
36318 Normal, explicitly set breakpoint.
36321 Normal, explicitly set watchpoint.
36324 Internal breakpoint, used to handle correctly stepping through
36325 @code{longjmp} calls.
36327 @item longjmp resume
36328 Internal breakpoint at the target of a @code{longjmp}.
36331 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
36334 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
36337 Shared library events.
36341 @kindex maint info btrace
36342 @item maint info btrace
36343 Pint information about raw branch tracing data.
36345 @kindex maint btrace packet-history
36346 @item maint btrace packet-history
36347 Print the raw branch trace packets that are used to compute the
36348 execution history for the @samp{record btrace} command. Both the
36349 information and the format in which it is printed depend on the btrace
36354 For the BTS recording format, print a list of blocks of sequential
36355 code. For each block, the following information is printed:
36359 Newer blocks have higher numbers. The oldest block has number zero.
36360 @item Lowest @samp{PC}
36361 @item Highest @samp{PC}
36365 For the Intel Processor Trace recording format, print a list of
36366 Intel Processor Trace packets. For each packet, the following
36367 information is printed:
36370 @item Packet number
36371 Newer packets have higher numbers. The oldest packet has number zero.
36373 The packet's offset in the trace stream.
36374 @item Packet opcode and payload
36378 @kindex maint btrace clear-packet-history
36379 @item maint btrace clear-packet-history
36380 Discards the cached packet history printed by the @samp{maint btrace
36381 packet-history} command. The history will be computed again when
36384 @kindex maint btrace clear
36385 @item maint btrace clear
36386 Discard the branch trace data. The data will be fetched anew and the
36387 branch trace will be recomputed when needed.
36389 This implicitly truncates the branch trace to a single branch trace
36390 buffer. When updating branch trace incrementally, the branch trace
36391 available to @value{GDBN} may be bigger than a single branch trace
36394 @kindex maint set btrace pt skip-pad
36395 @item maint set btrace pt skip-pad
36396 @kindex maint show btrace pt skip-pad
36397 @item maint show btrace pt skip-pad
36398 Control whether @value{GDBN} will skip PAD packets when computing the
36401 @kindex set displaced-stepping
36402 @kindex show displaced-stepping
36403 @cindex displaced stepping support
36404 @cindex out-of-line single-stepping
36405 @item set displaced-stepping
36406 @itemx show displaced-stepping
36407 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
36408 if the target supports it. Displaced stepping is a way to single-step
36409 over breakpoints without removing them from the inferior, by executing
36410 an out-of-line copy of the instruction that was originally at the
36411 breakpoint location. It is also known as out-of-line single-stepping.
36414 @item set displaced-stepping on
36415 If the target architecture supports it, @value{GDBN} will use
36416 displaced stepping to step over breakpoints.
36418 @item set displaced-stepping off
36419 @value{GDBN} will not use displaced stepping to step over breakpoints,
36420 even if such is supported by the target architecture.
36422 @cindex non-stop mode, and @samp{set displaced-stepping}
36423 @item set displaced-stepping auto
36424 This is the default mode. @value{GDBN} will use displaced stepping
36425 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
36426 architecture supports displaced stepping.
36429 @kindex maint check-psymtabs
36430 @item maint check-psymtabs
36431 Check the consistency of currently expanded psymtabs versus symtabs.
36432 Use this to check, for example, whether a symbol is in one but not the other.
36434 @kindex maint check-symtabs
36435 @item maint check-symtabs
36436 Check the consistency of currently expanded symtabs.
36438 @kindex maint expand-symtabs
36439 @item maint expand-symtabs [@var{regexp}]
36440 Expand symbol tables.
36441 If @var{regexp} is specified, only expand symbol tables for file
36442 names matching @var{regexp}.
36444 @kindex maint set catch-demangler-crashes
36445 @kindex maint show catch-demangler-crashes
36446 @cindex demangler crashes
36447 @item maint set catch-demangler-crashes [on|off]
36448 @itemx maint show catch-demangler-crashes
36449 Control whether @value{GDBN} should attempt to catch crashes in the
36450 symbol name demangler. The default is to attempt to catch crashes.
36451 If enabled, the first time a crash is caught, a core file is created,
36452 the offending symbol is displayed and the user is presented with the
36453 option to terminate the current session.
36455 @kindex maint cplus first_component
36456 @item maint cplus first_component @var{name}
36457 Print the first C@t{++} class/namespace component of @var{name}.
36459 @kindex maint cplus namespace
36460 @item maint cplus namespace
36461 Print the list of possible C@t{++} namespaces.
36463 @kindex maint deprecate
36464 @kindex maint undeprecate
36465 @cindex deprecated commands
36466 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
36467 @itemx maint undeprecate @var{command}
36468 Deprecate or undeprecate the named @var{command}. Deprecated commands
36469 cause @value{GDBN} to issue a warning when you use them. The optional
36470 argument @var{replacement} says which newer command should be used in
36471 favor of the deprecated one; if it is given, @value{GDBN} will mention
36472 the replacement as part of the warning.
36474 @kindex maint dump-me
36475 @item maint dump-me
36476 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
36477 Cause a fatal signal in the debugger and force it to dump its core.
36478 This is supported only on systems which support aborting a program
36479 with the @code{SIGQUIT} signal.
36481 @kindex maint internal-error
36482 @kindex maint internal-warning
36483 @kindex maint demangler-warning
36484 @cindex demangler crashes
36485 @item maint internal-error @r{[}@var{message-text}@r{]}
36486 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
36487 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
36489 Cause @value{GDBN} to call the internal function @code{internal_error},
36490 @code{internal_warning} or @code{demangler_warning} and hence behave
36491 as though an internal problem has been detected. In addition to
36492 reporting the internal problem, these functions give the user the
36493 opportunity to either quit @value{GDBN} or (for @code{internal_error}
36494 and @code{internal_warning}) create a core file of the current
36495 @value{GDBN} session.
36497 These commands take an optional parameter @var{message-text} that is
36498 used as the text of the error or warning message.
36500 Here's an example of using @code{internal-error}:
36503 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
36504 @dots{}/maint.c:121: internal-error: testing, 1, 2
36505 A problem internal to GDB has been detected. Further
36506 debugging may prove unreliable.
36507 Quit this debugging session? (y or n) @kbd{n}
36508 Create a core file? (y or n) @kbd{n}
36512 @cindex @value{GDBN} internal error
36513 @cindex internal errors, control of @value{GDBN} behavior
36514 @cindex demangler crashes
36516 @kindex maint set internal-error
36517 @kindex maint show internal-error
36518 @kindex maint set internal-warning
36519 @kindex maint show internal-warning
36520 @kindex maint set demangler-warning
36521 @kindex maint show demangler-warning
36522 @item maint set internal-error @var{action} [ask|yes|no]
36523 @itemx maint show internal-error @var{action}
36524 @itemx maint set internal-warning @var{action} [ask|yes|no]
36525 @itemx maint show internal-warning @var{action}
36526 @itemx maint set demangler-warning @var{action} [ask|yes|no]
36527 @itemx maint show demangler-warning @var{action}
36528 When @value{GDBN} reports an internal problem (error or warning) it
36529 gives the user the opportunity to both quit @value{GDBN} and create a
36530 core file of the current @value{GDBN} session. These commands let you
36531 override the default behaviour for each particular @var{action},
36532 described in the table below.
36536 You can specify that @value{GDBN} should always (yes) or never (no)
36537 quit. The default is to ask the user what to do.
36540 You can specify that @value{GDBN} should always (yes) or never (no)
36541 create a core file. The default is to ask the user what to do. Note
36542 that there is no @code{corefile} option for @code{demangler-warning}:
36543 demangler warnings always create a core file and this cannot be
36547 @kindex maint packet
36548 @item maint packet @var{text}
36549 If @value{GDBN} is talking to an inferior via the serial protocol,
36550 then this command sends the string @var{text} to the inferior, and
36551 displays the response packet. @value{GDBN} supplies the initial
36552 @samp{$} character, the terminating @samp{#} character, and the
36555 @kindex maint print architecture
36556 @item maint print architecture @r{[}@var{file}@r{]}
36557 Print the entire architecture configuration. The optional argument
36558 @var{file} names the file where the output goes.
36560 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
36561 @item maint print c-tdesc
36562 Print the target description (@pxref{Target Descriptions}) as
36563 a C source file. By default, the target description is for the current
36564 target, but if the optional argument @var{file} is provided, that file
36565 is used to produce the description. The @var{file} should be an XML
36566 document, of the form described in @ref{Target Description Format}.
36567 The created source file is built into @value{GDBN} when @value{GDBN} is
36568 built again. This command is used by developers after they add or
36569 modify XML target descriptions.
36571 @kindex maint check xml-descriptions
36572 @item maint check xml-descriptions @var{dir}
36573 Check that the target descriptions dynamically created by @value{GDBN}
36574 equal the descriptions created from XML files found in @var{dir}.
36576 @anchor{maint check libthread-db}
36577 @kindex maint check libthread-db
36578 @item maint check libthread-db
36579 Run integrity checks on the current inferior's thread debugging
36580 library. This exercises all @code{libthread_db} functionality used by
36581 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
36582 @code{proc_service} functions provided by @value{GDBN} that
36583 @code{libthread_db} uses. Note that parts of the test may be skipped
36584 on some platforms when debugging core files.
36586 @kindex maint print dummy-frames
36587 @item maint print dummy-frames
36588 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
36591 (@value{GDBP}) @kbd{b add}
36593 (@value{GDBP}) @kbd{print add(2,3)}
36594 Breakpoint 2, add (a=2, b=3) at @dots{}
36596 The program being debugged stopped while in a function called from GDB.
36598 (@value{GDBP}) @kbd{maint print dummy-frames}
36599 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
36603 Takes an optional file parameter.
36605 @kindex maint print registers
36606 @kindex maint print raw-registers
36607 @kindex maint print cooked-registers
36608 @kindex maint print register-groups
36609 @kindex maint print remote-registers
36610 @item maint print registers @r{[}@var{file}@r{]}
36611 @itemx maint print raw-registers @r{[}@var{file}@r{]}
36612 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
36613 @itemx maint print register-groups @r{[}@var{file}@r{]}
36614 @itemx maint print remote-registers @r{[}@var{file}@r{]}
36615 Print @value{GDBN}'s internal register data structures.
36617 The command @code{maint print raw-registers} includes the contents of
36618 the raw register cache; the command @code{maint print
36619 cooked-registers} includes the (cooked) value of all registers,
36620 including registers which aren't available on the target nor visible
36621 to user; the command @code{maint print register-groups} includes the
36622 groups that each register is a member of; and the command @code{maint
36623 print remote-registers} includes the remote target's register numbers
36624 and offsets in the `G' packets.
36626 These commands take an optional parameter, a file name to which to
36627 write the information.
36629 @kindex maint print reggroups
36630 @item maint print reggroups @r{[}@var{file}@r{]}
36631 Print @value{GDBN}'s internal register group data structures. The
36632 optional argument @var{file} tells to what file to write the
36635 The register groups info looks like this:
36638 (@value{GDBP}) @kbd{maint print reggroups}
36651 This command forces @value{GDBN} to flush its internal register cache.
36653 @kindex maint print objfiles
36654 @cindex info for known object files
36655 @item maint print objfiles @r{[}@var{regexp}@r{]}
36656 Print a dump of all known object files.
36657 If @var{regexp} is specified, only print object files whose names
36658 match @var{regexp}. For each object file, this command prints its name,
36659 address in memory, and all of its psymtabs and symtabs.
36661 @kindex maint print user-registers
36662 @cindex user registers
36663 @item maint print user-registers
36664 List all currently available @dfn{user registers}. User registers
36665 typically provide alternate names for actual hardware registers. They
36666 include the four ``standard'' registers @code{$fp}, @code{$pc},
36667 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
36668 registers can be used in expressions in the same way as the canonical
36669 register names, but only the latter are listed by the @code{info
36670 registers} and @code{maint print registers} commands.
36672 @kindex maint print section-scripts
36673 @cindex info for known .debug_gdb_scripts-loaded scripts
36674 @item maint print section-scripts [@var{regexp}]
36675 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
36676 If @var{regexp} is specified, only print scripts loaded by object files
36677 matching @var{regexp}.
36678 For each script, this command prints its name as specified in the objfile,
36679 and the full path if known.
36680 @xref{dotdebug_gdb_scripts section}.
36682 @kindex maint print statistics
36683 @cindex bcache statistics
36684 @item maint print statistics
36685 This command prints, for each object file in the program, various data
36686 about that object file followed by the byte cache (@dfn{bcache})
36687 statistics for the object file. The objfile data includes the number
36688 of minimal, partial, full, and stabs symbols, the number of types
36689 defined by the objfile, the number of as yet unexpanded psym tables,
36690 the number of line tables and string tables, and the amount of memory
36691 used by the various tables. The bcache statistics include the counts,
36692 sizes, and counts of duplicates of all and unique objects, max,
36693 average, and median entry size, total memory used and its overhead and
36694 savings, and various measures of the hash table size and chain
36697 @kindex maint print target-stack
36698 @cindex target stack description
36699 @item maint print target-stack
36700 A @dfn{target} is an interface between the debugger and a particular
36701 kind of file or process. Targets can be stacked in @dfn{strata},
36702 so that more than one target can potentially respond to a request.
36703 In particular, memory accesses will walk down the stack of targets
36704 until they find a target that is interested in handling that particular
36707 This command prints a short description of each layer that was pushed on
36708 the @dfn{target stack}, starting from the top layer down to the bottom one.
36710 @kindex maint print type
36711 @cindex type chain of a data type
36712 @item maint print type @var{expr}
36713 Print the type chain for a type specified by @var{expr}. The argument
36714 can be either a type name or a symbol. If it is a symbol, the type of
36715 that symbol is described. The type chain produced by this command is
36716 a recursive definition of the data type as stored in @value{GDBN}'s
36717 data structures, including its flags and contained types.
36719 @kindex maint selftest
36721 @item maint selftest @r{[}@var{filter}@r{]}
36722 Run any self tests that were compiled in to @value{GDBN}. This will
36723 print a message showing how many tests were run, and how many failed.
36724 If a @var{filter} is passed, only the tests with @var{filter} in their
36727 @kindex "maint info selftests"
36729 @item maint info selftests
36730 List the selftests compiled in to @value{GDBN}.
36732 @kindex maint set dwarf always-disassemble
36733 @kindex maint show dwarf always-disassemble
36734 @item maint set dwarf always-disassemble
36735 @item maint show dwarf always-disassemble
36736 Control the behavior of @code{info address} when using DWARF debugging
36739 The default is @code{off}, which means that @value{GDBN} should try to
36740 describe a variable's location in an easily readable format. When
36741 @code{on}, @value{GDBN} will instead display the DWARF location
36742 expression in an assembly-like format. Note that some locations are
36743 too complex for @value{GDBN} to describe simply; in this case you will
36744 always see the disassembly form.
36746 Here is an example of the resulting disassembly:
36749 (gdb) info addr argc
36750 Symbol "argc" is a complex DWARF expression:
36754 For more information on these expressions, see
36755 @uref{http://www.dwarfstd.org/, the DWARF standard}.
36757 @kindex maint set dwarf max-cache-age
36758 @kindex maint show dwarf max-cache-age
36759 @item maint set dwarf max-cache-age
36760 @itemx maint show dwarf max-cache-age
36761 Control the DWARF compilation unit cache.
36763 @cindex DWARF compilation units cache
36764 In object files with inter-compilation-unit references, such as those
36765 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
36766 reader needs to frequently refer to previously read compilation units.
36767 This setting controls how long a compilation unit will remain in the
36768 cache if it is not referenced. A higher limit means that cached
36769 compilation units will be stored in memory longer, and more total
36770 memory will be used. Setting it to zero disables caching, which will
36771 slow down @value{GDBN} startup, but reduce memory consumption.
36773 @kindex maint set dwarf unwinders
36774 @kindex maint show dwarf unwinders
36775 @item maint set dwarf unwinders
36776 @itemx maint show dwarf unwinders
36777 Control use of the DWARF frame unwinders.
36779 @cindex DWARF frame unwinders
36780 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
36781 frame unwinders to build the backtrace. Many of these targets will
36782 also have a second mechanism for building the backtrace for use in
36783 cases where DWARF information is not available, this second mechanism
36784 is often an analysis of a function's prologue.
36786 In order to extend testing coverage of the second level stack
36787 unwinding mechanisms it is helpful to be able to disable the DWARF
36788 stack unwinders, this can be done with this switch.
36790 In normal use of @value{GDBN} disabling the DWARF unwinders is not
36791 advisable, there are cases that are better handled through DWARF than
36792 prologue analysis, and the debug experience is likely to be better
36793 with the DWARF frame unwinders enabled.
36795 If DWARF frame unwinders are not supported for a particular target
36796 architecture, then enabling this flag does not cause them to be used.
36797 @kindex maint set profile
36798 @kindex maint show profile
36799 @cindex profiling GDB
36800 @item maint set profile
36801 @itemx maint show profile
36802 Control profiling of @value{GDBN}.
36804 Profiling will be disabled until you use the @samp{maint set profile}
36805 command to enable it. When you enable profiling, the system will begin
36806 collecting timing and execution count data; when you disable profiling or
36807 exit @value{GDBN}, the results will be written to a log file. Remember that
36808 if you use profiling, @value{GDBN} will overwrite the profiling log file
36809 (often called @file{gmon.out}). If you have a record of important profiling
36810 data in a @file{gmon.out} file, be sure to move it to a safe location.
36812 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
36813 compiled with the @samp{-pg} compiler option.
36815 @kindex maint set show-debug-regs
36816 @kindex maint show show-debug-regs
36817 @cindex hardware debug registers
36818 @item maint set show-debug-regs
36819 @itemx maint show show-debug-regs
36820 Control whether to show variables that mirror the hardware debug
36821 registers. Use @code{on} to enable, @code{off} to disable. If
36822 enabled, the debug registers values are shown when @value{GDBN} inserts or
36823 removes a hardware breakpoint or watchpoint, and when the inferior
36824 triggers a hardware-assisted breakpoint or watchpoint.
36826 @kindex maint set show-all-tib
36827 @kindex maint show show-all-tib
36828 @item maint set show-all-tib
36829 @itemx maint show show-all-tib
36830 Control whether to show all non zero areas within a 1k block starting
36831 at thread local base, when using the @samp{info w32 thread-information-block}
36834 @kindex maint set target-async
36835 @kindex maint show target-async
36836 @item maint set target-async
36837 @itemx maint show target-async
36838 This controls whether @value{GDBN} targets operate in synchronous or
36839 asynchronous mode (@pxref{Background Execution}). Normally the
36840 default is asynchronous, if it is available; but this can be changed
36841 to more easily debug problems occurring only in synchronous mode.
36843 @kindex maint set target-non-stop @var{mode} [on|off|auto]
36844 @kindex maint show target-non-stop
36845 @item maint set target-non-stop
36846 @itemx maint show target-non-stop
36848 This controls whether @value{GDBN} targets always operate in non-stop
36849 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
36850 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
36851 if supported by the target.
36854 @item maint set target-non-stop auto
36855 This is the default mode. @value{GDBN} controls the target in
36856 non-stop mode if the target supports it.
36858 @item maint set target-non-stop on
36859 @value{GDBN} controls the target in non-stop mode even if the target
36860 does not indicate support.
36862 @item maint set target-non-stop off
36863 @value{GDBN} does not control the target in non-stop mode even if the
36864 target supports it.
36867 @kindex maint set per-command
36868 @kindex maint show per-command
36869 @item maint set per-command
36870 @itemx maint show per-command
36871 @cindex resources used by commands
36873 @value{GDBN} can display the resources used by each command.
36874 This is useful in debugging performance problems.
36877 @item maint set per-command space [on|off]
36878 @itemx maint show per-command space
36879 Enable or disable the printing of the memory used by GDB for each command.
36880 If enabled, @value{GDBN} will display how much memory each command
36881 took, following the command's own output.
36882 This can also be requested by invoking @value{GDBN} with the
36883 @option{--statistics} command-line switch (@pxref{Mode Options}).
36885 @item maint set per-command time [on|off]
36886 @itemx maint show per-command time
36887 Enable or disable the printing of the execution time of @value{GDBN}
36889 If enabled, @value{GDBN} will display how much time it
36890 took to execute each command, following the command's own output.
36891 Both CPU time and wallclock time are printed.
36892 Printing both is useful when trying to determine whether the cost is
36893 CPU or, e.g., disk/network latency.
36894 Note that the CPU time printed is for @value{GDBN} only, it does not include
36895 the execution time of the inferior because there's no mechanism currently
36896 to compute how much time was spent by @value{GDBN} and how much time was
36897 spent by the program been debugged.
36898 This can also be requested by invoking @value{GDBN} with the
36899 @option{--statistics} command-line switch (@pxref{Mode Options}).
36901 @item maint set per-command symtab [on|off]
36902 @itemx maint show per-command symtab
36903 Enable or disable the printing of basic symbol table statistics
36905 If enabled, @value{GDBN} will display the following information:
36909 number of symbol tables
36911 number of primary symbol tables
36913 number of blocks in the blockvector
36917 @kindex maint set check-libthread-db
36918 @kindex maint show check-libthread-db
36919 @item maint set check-libthread-db [on|off]
36920 @itemx maint show check-libthread-db
36921 Control whether @value{GDBN} should run integrity checks on inferior
36922 specific thread debugging libraries as they are loaded. The default
36923 is not to perform such checks. If any check fails @value{GDBN} will
36924 unload the library and continue searching for a suitable candidate as
36925 described in @ref{set libthread-db-search-path}. For more information
36926 about the tests, see @ref{maint check libthread-db}.
36928 @kindex maint space
36929 @cindex memory used by commands
36930 @item maint space @var{value}
36931 An alias for @code{maint set per-command space}.
36932 A non-zero value enables it, zero disables it.
36935 @cindex time of command execution
36936 @item maint time @var{value}
36937 An alias for @code{maint set per-command time}.
36938 A non-zero value enables it, zero disables it.
36940 @kindex maint translate-address
36941 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
36942 Find the symbol stored at the location specified by the address
36943 @var{addr} and an optional section name @var{section}. If found,
36944 @value{GDBN} prints the name of the closest symbol and an offset from
36945 the symbol's location to the specified address. This is similar to
36946 the @code{info address} command (@pxref{Symbols}), except that this
36947 command also allows to find symbols in other sections.
36949 If section was not specified, the section in which the symbol was found
36950 is also printed. For dynamically linked executables, the name of
36951 executable or shared library containing the symbol is printed as well.
36955 The following command is useful for non-interactive invocations of
36956 @value{GDBN}, such as in the test suite.
36959 @item set watchdog @var{nsec}
36960 @kindex set watchdog
36961 @cindex watchdog timer
36962 @cindex timeout for commands
36963 Set the maximum number of seconds @value{GDBN} will wait for the
36964 target operation to finish. If this time expires, @value{GDBN}
36965 reports and error and the command is aborted.
36967 @item show watchdog
36968 Show the current setting of the target wait timeout.
36971 @node Remote Protocol
36972 @appendix @value{GDBN} Remote Serial Protocol
36977 * Stop Reply Packets::
36978 * General Query Packets::
36979 * Architecture-Specific Protocol Details::
36980 * Tracepoint Packets::
36981 * Host I/O Packets::
36983 * Notification Packets::
36984 * Remote Non-Stop::
36985 * Packet Acknowledgment::
36987 * File-I/O Remote Protocol Extension::
36988 * Library List Format::
36989 * Library List Format for SVR4 Targets::
36990 * Memory Map Format::
36991 * Thread List Format::
36992 * Traceframe Info Format::
36993 * Branch Trace Format::
36994 * Branch Trace Configuration Format::
37000 There may be occasions when you need to know something about the
37001 protocol---for example, if there is only one serial port to your target
37002 machine, you might want your program to do something special if it
37003 recognizes a packet meant for @value{GDBN}.
37005 In the examples below, @samp{->} and @samp{<-} are used to indicate
37006 transmitted and received data, respectively.
37008 @cindex protocol, @value{GDBN} remote serial
37009 @cindex serial protocol, @value{GDBN} remote
37010 @cindex remote serial protocol
37011 All @value{GDBN} commands and responses (other than acknowledgments
37012 and notifications, see @ref{Notification Packets}) are sent as a
37013 @var{packet}. A @var{packet} is introduced with the character
37014 @samp{$}, the actual @var{packet-data}, and the terminating character
37015 @samp{#} followed by a two-digit @var{checksum}:
37018 @code{$}@var{packet-data}@code{#}@var{checksum}
37022 @cindex checksum, for @value{GDBN} remote
37024 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37025 characters between the leading @samp{$} and the trailing @samp{#} (an
37026 eight bit unsigned checksum).
37028 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37029 specification also included an optional two-digit @var{sequence-id}:
37032 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37035 @cindex sequence-id, for @value{GDBN} remote
37037 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37038 has never output @var{sequence-id}s. Stubs that handle packets added
37039 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37041 When either the host or the target machine receives a packet, the first
37042 response expected is an acknowledgment: either @samp{+} (to indicate
37043 the package was received correctly) or @samp{-} (to request
37047 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37052 The @samp{+}/@samp{-} acknowledgments can be disabled
37053 once a connection is established.
37054 @xref{Packet Acknowledgment}, for details.
37056 The host (@value{GDBN}) sends @var{command}s, and the target (the
37057 debugging stub incorporated in your program) sends a @var{response}. In
37058 the case of step and continue @var{command}s, the response is only sent
37059 when the operation has completed, and the target has again stopped all
37060 threads in all attached processes. This is the default all-stop mode
37061 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37062 execution mode; see @ref{Remote Non-Stop}, for details.
37064 @var{packet-data} consists of a sequence of characters with the
37065 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37068 @cindex remote protocol, field separator
37069 Fields within the packet should be separated using @samp{,} @samp{;} or
37070 @samp{:}. Except where otherwise noted all numbers are represented in
37071 @sc{hex} with leading zeros suppressed.
37073 Implementors should note that prior to @value{GDBN} 5.0, the character
37074 @samp{:} could not appear as the third character in a packet (as it
37075 would potentially conflict with the @var{sequence-id}).
37077 @cindex remote protocol, binary data
37078 @anchor{Binary Data}
37079 Binary data in most packets is encoded either as two hexadecimal
37080 digits per byte of binary data. This allowed the traditional remote
37081 protocol to work over connections which were only seven-bit clean.
37082 Some packets designed more recently assume an eight-bit clean
37083 connection, and use a more efficient encoding to send and receive
37086 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37087 as an escape character. Any escaped byte is transmitted as the escape
37088 character followed by the original character XORed with @code{0x20}.
37089 For example, the byte @code{0x7d} would be transmitted as the two
37090 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37091 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37092 @samp{@}}) must always be escaped. Responses sent by the stub
37093 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37094 is not interpreted as the start of a run-length encoded sequence
37097 Response @var{data} can be run-length encoded to save space.
37098 Run-length encoding replaces runs of identical characters with one
37099 instance of the repeated character, followed by a @samp{*} and a
37100 repeat count. The repeat count is itself sent encoded, to avoid
37101 binary characters in @var{data}: a value of @var{n} is sent as
37102 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37103 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37104 code 32) for a repeat count of 3. (This is because run-length
37105 encoding starts to win for counts 3 or more.) Thus, for example,
37106 @samp{0* } is a run-length encoding of ``0000'': the space character
37107 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37110 The printable characters @samp{#} and @samp{$} or with a numeric value
37111 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37112 seven repeats (@samp{$}) can be expanded using a repeat count of only
37113 five (@samp{"}). For example, @samp{00000000} can be encoded as
37116 The error response returned for some packets includes a two character
37117 error number. That number is not well defined.
37119 @cindex empty response, for unsupported packets
37120 For any @var{command} not supported by the stub, an empty response
37121 (@samp{$#00}) should be returned. That way it is possible to extend the
37122 protocol. A newer @value{GDBN} can tell if a packet is supported based
37125 At a minimum, a stub is required to support the @samp{g} and @samp{G}
37126 commands for register access, and the @samp{m} and @samp{M} commands
37127 for memory access. Stubs that only control single-threaded targets
37128 can implement run control with the @samp{c} (continue), and @samp{s}
37129 (step) commands. Stubs that support multi-threading targets should
37130 support the @samp{vCont} command. All other commands are optional.
37135 The following table provides a complete list of all currently defined
37136 @var{command}s and their corresponding response @var{data}.
37137 @xref{File-I/O Remote Protocol Extension}, for details about the File
37138 I/O extension of the remote protocol.
37140 Each packet's description has a template showing the packet's overall
37141 syntax, followed by an explanation of the packet's meaning. We
37142 include spaces in some of the templates for clarity; these are not
37143 part of the packet's syntax. No @value{GDBN} packet uses spaces to
37144 separate its components. For example, a template like @samp{foo
37145 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
37146 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
37147 @var{baz}. @value{GDBN} does not transmit a space character between the
37148 @samp{foo} and the @var{bar}, or between the @var{bar} and the
37151 @cindex @var{thread-id}, in remote protocol
37152 @anchor{thread-id syntax}
37153 Several packets and replies include a @var{thread-id} field to identify
37154 a thread. Normally these are positive numbers with a target-specific
37155 interpretation, formatted as big-endian hex strings. A @var{thread-id}
37156 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
37159 In addition, the remote protocol supports a multiprocess feature in
37160 which the @var{thread-id} syntax is extended to optionally include both
37161 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
37162 The @var{pid} (process) and @var{tid} (thread) components each have the
37163 format described above: a positive number with target-specific
37164 interpretation formatted as a big-endian hex string, literal @samp{-1}
37165 to indicate all processes or threads (respectively), or @samp{0} to
37166 indicate an arbitrary process or thread. Specifying just a process, as
37167 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
37168 error to specify all processes but a specific thread, such as
37169 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
37170 for those packets and replies explicitly documented to include a process
37171 ID, rather than a @var{thread-id}.
37173 The multiprocess @var{thread-id} syntax extensions are only used if both
37174 @value{GDBN} and the stub report support for the @samp{multiprocess}
37175 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
37178 Note that all packet forms beginning with an upper- or lower-case
37179 letter, other than those described here, are reserved for future use.
37181 Here are the packet descriptions.
37186 @cindex @samp{!} packet
37187 @anchor{extended mode}
37188 Enable extended mode. In extended mode, the remote server is made
37189 persistent. The @samp{R} packet is used to restart the program being
37195 The remote target both supports and has enabled extended mode.
37199 @cindex @samp{?} packet
37201 Indicate the reason the target halted. The reply is the same as for
37202 step and continue. This packet has a special interpretation when the
37203 target is in non-stop mode; see @ref{Remote Non-Stop}.
37206 @xref{Stop Reply Packets}, for the reply specifications.
37208 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
37209 @cindex @samp{A} packet
37210 Initialized @code{argv[]} array passed into program. @var{arglen}
37211 specifies the number of bytes in the hex encoded byte stream
37212 @var{arg}. See @code{gdbserver} for more details.
37217 The arguments were set.
37223 @cindex @samp{b} packet
37224 (Don't use this packet; its behavior is not well-defined.)
37225 Change the serial line speed to @var{baud}.
37227 JTC: @emph{When does the transport layer state change? When it's
37228 received, or after the ACK is transmitted. In either case, there are
37229 problems if the command or the acknowledgment packet is dropped.}
37231 Stan: @emph{If people really wanted to add something like this, and get
37232 it working for the first time, they ought to modify ser-unix.c to send
37233 some kind of out-of-band message to a specially-setup stub and have the
37234 switch happen "in between" packets, so that from remote protocol's point
37235 of view, nothing actually happened.}
37237 @item B @var{addr},@var{mode}
37238 @cindex @samp{B} packet
37239 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
37240 breakpoint at @var{addr}.
37242 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
37243 (@pxref{insert breakpoint or watchpoint packet}).
37245 @cindex @samp{bc} packet
37248 Backward continue. Execute the target system in reverse. No parameter.
37249 @xref{Reverse Execution}, for more information.
37252 @xref{Stop Reply Packets}, for the reply specifications.
37254 @cindex @samp{bs} packet
37257 Backward single step. Execute one instruction in reverse. No parameter.
37258 @xref{Reverse Execution}, for more information.
37261 @xref{Stop Reply Packets}, for the reply specifications.
37263 @item c @r{[}@var{addr}@r{]}
37264 @cindex @samp{c} packet
37265 Continue at @var{addr}, which is the address to resume. If @var{addr}
37266 is omitted, resume at current address.
37268 This packet is deprecated for multi-threading support. @xref{vCont
37272 @xref{Stop Reply Packets}, for the reply specifications.
37274 @item C @var{sig}@r{[};@var{addr}@r{]}
37275 @cindex @samp{C} packet
37276 Continue with signal @var{sig} (hex signal number). If
37277 @samp{;@var{addr}} is omitted, resume at same address.
37279 This packet is deprecated for multi-threading support. @xref{vCont
37283 @xref{Stop Reply Packets}, for the reply specifications.
37286 @cindex @samp{d} packet
37289 Don't use this packet; instead, define a general set packet
37290 (@pxref{General Query Packets}).
37294 @cindex @samp{D} packet
37295 The first form of the packet is used to detach @value{GDBN} from the
37296 remote system. It is sent to the remote target
37297 before @value{GDBN} disconnects via the @code{detach} command.
37299 The second form, including a process ID, is used when multiprocess
37300 protocol extensions are enabled (@pxref{multiprocess extensions}), to
37301 detach only a specific process. The @var{pid} is specified as a
37302 big-endian hex string.
37312 @item F @var{RC},@var{EE},@var{CF};@var{XX}
37313 @cindex @samp{F} packet
37314 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
37315 This is part of the File-I/O protocol extension. @xref{File-I/O
37316 Remote Protocol Extension}, for the specification.
37319 @anchor{read registers packet}
37320 @cindex @samp{g} packet
37321 Read general registers.
37325 @item @var{XX@dots{}}
37326 Each byte of register data is described by two hex digits. The bytes
37327 with the register are transmitted in target byte order. The size of
37328 each register and their position within the @samp{g} packet are
37329 determined by the @value{GDBN} internal gdbarch functions
37330 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
37332 When reading registers from a trace frame (@pxref{Analyze Collected
37333 Data,,Using the Collected Data}), the stub may also return a string of
37334 literal @samp{x}'s in place of the register data digits, to indicate
37335 that the corresponding register has not been collected, thus its value
37336 is unavailable. For example, for an architecture with 4 registers of
37337 4 bytes each, the following reply indicates to @value{GDBN} that
37338 registers 0 and 2 have not been collected, while registers 1 and 3
37339 have been collected, and both have zero value:
37343 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
37350 @item G @var{XX@dots{}}
37351 @cindex @samp{G} packet
37352 Write general registers. @xref{read registers packet}, for a
37353 description of the @var{XX@dots{}} data.
37363 @item H @var{op} @var{thread-id}
37364 @cindex @samp{H} packet
37365 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
37366 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
37367 should be @samp{c} for step and continue operations (note that this
37368 is deprecated, supporting the @samp{vCont} command is a better
37369 option), and @samp{g} for other operations. The thread designator
37370 @var{thread-id} has the format and interpretation described in
37371 @ref{thread-id syntax}.
37382 @c 'H': How restrictive (or permissive) is the thread model. If a
37383 @c thread is selected and stopped, are other threads allowed
37384 @c to continue to execute? As I mentioned above, I think the
37385 @c semantics of each command when a thread is selected must be
37386 @c described. For example:
37388 @c 'g': If the stub supports threads and a specific thread is
37389 @c selected, returns the register block from that thread;
37390 @c otherwise returns current registers.
37392 @c 'G' If the stub supports threads and a specific thread is
37393 @c selected, sets the registers of the register block of
37394 @c that thread; otherwise sets current registers.
37396 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
37397 @anchor{cycle step packet}
37398 @cindex @samp{i} packet
37399 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
37400 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
37401 step starting at that address.
37404 @cindex @samp{I} packet
37405 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
37409 @cindex @samp{k} packet
37412 The exact effect of this packet is not specified.
37414 For a bare-metal target, it may power cycle or reset the target
37415 system. For that reason, the @samp{k} packet has no reply.
37417 For a single-process target, it may kill that process if possible.
37419 A multiple-process target may choose to kill just one process, or all
37420 that are under @value{GDBN}'s control. For more precise control, use
37421 the vKill packet (@pxref{vKill packet}).
37423 If the target system immediately closes the connection in response to
37424 @samp{k}, @value{GDBN} does not consider the lack of packet
37425 acknowledgment to be an error, and assumes the kill was successful.
37427 If connected using @kbd{target extended-remote}, and the target does
37428 not close the connection in response to a kill request, @value{GDBN}
37429 probes the target state as if a new connection was opened
37430 (@pxref{? packet}).
37432 @item m @var{addr},@var{length}
37433 @cindex @samp{m} packet
37434 Read @var{length} addressable memory units starting at address @var{addr}
37435 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
37436 any particular boundary.
37438 The stub need not use any particular size or alignment when gathering
37439 data from memory for the response; even if @var{addr} is word-aligned
37440 and @var{length} is a multiple of the word size, the stub is free to
37441 use byte accesses, or not. For this reason, this packet may not be
37442 suitable for accessing memory-mapped I/O devices.
37443 @cindex alignment of remote memory accesses
37444 @cindex size of remote memory accesses
37445 @cindex memory, alignment and size of remote accesses
37449 @item @var{XX@dots{}}
37450 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
37451 The reply may contain fewer addressable memory units than requested if the
37452 server was able to read only part of the region of memory.
37457 @item M @var{addr},@var{length}:@var{XX@dots{}}
37458 @cindex @samp{M} packet
37459 Write @var{length} addressable memory units starting at address @var{addr}
37460 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
37461 byte is transmitted as a two-digit hexadecimal number.
37468 for an error (this includes the case where only part of the data was
37473 @cindex @samp{p} packet
37474 Read the value of register @var{n}; @var{n} is in hex.
37475 @xref{read registers packet}, for a description of how the returned
37476 register value is encoded.
37480 @item @var{XX@dots{}}
37481 the register's value
37485 Indicating an unrecognized @var{query}.
37488 @item P @var{n@dots{}}=@var{r@dots{}}
37489 @anchor{write register packet}
37490 @cindex @samp{P} packet
37491 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
37492 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
37493 digits for each byte in the register (target byte order).
37503 @item q @var{name} @var{params}@dots{}
37504 @itemx Q @var{name} @var{params}@dots{}
37505 @cindex @samp{q} packet
37506 @cindex @samp{Q} packet
37507 General query (@samp{q}) and set (@samp{Q}). These packets are
37508 described fully in @ref{General Query Packets}.
37511 @cindex @samp{r} packet
37512 Reset the entire system.
37514 Don't use this packet; use the @samp{R} packet instead.
37517 @cindex @samp{R} packet
37518 Restart the program being debugged. The @var{XX}, while needed, is ignored.
37519 This packet is only available in extended mode (@pxref{extended mode}).
37521 The @samp{R} packet has no reply.
37523 @item s @r{[}@var{addr}@r{]}
37524 @cindex @samp{s} packet
37525 Single step, resuming at @var{addr}. If
37526 @var{addr} is omitted, resume at same address.
37528 This packet is deprecated for multi-threading support. @xref{vCont
37532 @xref{Stop Reply Packets}, for the reply specifications.
37534 @item S @var{sig}@r{[};@var{addr}@r{]}
37535 @anchor{step with signal packet}
37536 @cindex @samp{S} packet
37537 Step with signal. This is analogous to the @samp{C} packet, but
37538 requests a single-step, rather than a normal resumption of execution.
37540 This packet is deprecated for multi-threading support. @xref{vCont
37544 @xref{Stop Reply Packets}, for the reply specifications.
37546 @item t @var{addr}:@var{PP},@var{MM}
37547 @cindex @samp{t} packet
37548 Search backwards starting at address @var{addr} for a match with pattern
37549 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
37550 There must be at least 3 digits in @var{addr}.
37552 @item T @var{thread-id}
37553 @cindex @samp{T} packet
37554 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
37559 thread is still alive
37565 Packets starting with @samp{v} are identified by a multi-letter name,
37566 up to the first @samp{;} or @samp{?} (or the end of the packet).
37568 @item vAttach;@var{pid}
37569 @cindex @samp{vAttach} packet
37570 Attach to a new process with the specified process ID @var{pid}.
37571 The process ID is a
37572 hexadecimal integer identifying the process. In all-stop mode, all
37573 threads in the attached process are stopped; in non-stop mode, it may be
37574 attached without being stopped if that is supported by the target.
37576 @c In non-stop mode, on a successful vAttach, the stub should set the
37577 @c current thread to a thread of the newly-attached process. After
37578 @c attaching, GDB queries for the attached process's thread ID with qC.
37579 @c Also note that, from a user perspective, whether or not the
37580 @c target is stopped on attach in non-stop mode depends on whether you
37581 @c use the foreground or background version of the attach command, not
37582 @c on what vAttach does; GDB does the right thing with respect to either
37583 @c stopping or restarting threads.
37585 This packet is only available in extended mode (@pxref{extended mode}).
37591 @item @r{Any stop packet}
37592 for success in all-stop mode (@pxref{Stop Reply Packets})
37594 for success in non-stop mode (@pxref{Remote Non-Stop})
37597 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
37598 @cindex @samp{vCont} packet
37599 @anchor{vCont packet}
37600 Resume the inferior, specifying different actions for each thread.
37602 For each inferior thread, the leftmost action with a matching
37603 @var{thread-id} is applied. Threads that don't match any action
37604 remain in their current state. Thread IDs are specified using the
37605 syntax described in @ref{thread-id syntax}. If multiprocess
37606 extensions (@pxref{multiprocess extensions}) are supported, actions
37607 can be specified to match all threads in a process by using the
37608 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
37609 @var{thread-id} matches all threads. Specifying no actions is an
37612 Currently supported actions are:
37618 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
37622 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
37625 @item r @var{start},@var{end}
37626 Step once, and then keep stepping as long as the thread stops at
37627 addresses between @var{start} (inclusive) and @var{end} (exclusive).
37628 The remote stub reports a stop reply when either the thread goes out
37629 of the range or is stopped due to an unrelated reason, such as hitting
37630 a breakpoint. @xref{range stepping}.
37632 If the range is empty (@var{start} == @var{end}), then the action
37633 becomes equivalent to the @samp{s} action. In other words,
37634 single-step once, and report the stop (even if the stepped instruction
37635 jumps to @var{start}).
37637 (A stop reply may be sent at any point even if the PC is still within
37638 the stepping range; for example, it is valid to implement this packet
37639 in a degenerate way as a single instruction step operation.)
37643 The optional argument @var{addr} normally associated with the
37644 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
37645 not supported in @samp{vCont}.
37647 The @samp{t} action is only relevant in non-stop mode
37648 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
37649 A stop reply should be generated for any affected thread not already stopped.
37650 When a thread is stopped by means of a @samp{t} action,
37651 the corresponding stop reply should indicate that the thread has stopped with
37652 signal @samp{0}, regardless of whether the target uses some other signal
37653 as an implementation detail.
37655 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
37656 @samp{r} actions for threads that are already running. Conversely,
37657 the server must ignore @samp{t} actions for threads that are already
37660 @emph{Note:} In non-stop mode, a thread is considered running until
37661 @value{GDBN} acknowleges an asynchronous stop notification for it with
37662 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
37664 The stub must support @samp{vCont} if it reports support for
37665 multiprocess extensions (@pxref{multiprocess extensions}).
37668 @xref{Stop Reply Packets}, for the reply specifications.
37671 @cindex @samp{vCont?} packet
37672 Request a list of actions supported by the @samp{vCont} packet.
37676 @item vCont@r{[};@var{action}@dots{}@r{]}
37677 The @samp{vCont} packet is supported. Each @var{action} is a supported
37678 command in the @samp{vCont} packet.
37680 The @samp{vCont} packet is not supported.
37683 @anchor{vCtrlC packet}
37685 @cindex @samp{vCtrlC} packet
37686 Interrupt remote target as if a control-C was pressed on the remote
37687 terminal. This is the equivalent to reacting to the @code{^C}
37688 (@samp{\003}, the control-C character) character in all-stop mode
37689 while the target is running, except this works in non-stop mode.
37690 @xref{interrupting remote targets}, for more info on the all-stop
37701 @item vFile:@var{operation}:@var{parameter}@dots{}
37702 @cindex @samp{vFile} packet
37703 Perform a file operation on the target system. For details,
37704 see @ref{Host I/O Packets}.
37706 @item vFlashErase:@var{addr},@var{length}
37707 @cindex @samp{vFlashErase} packet
37708 Direct the stub to erase @var{length} bytes of flash starting at
37709 @var{addr}. The region may enclose any number of flash blocks, but
37710 its start and end must fall on block boundaries, as indicated by the
37711 flash block size appearing in the memory map (@pxref{Memory Map
37712 Format}). @value{GDBN} groups flash memory programming operations
37713 together, and sends a @samp{vFlashDone} request after each group; the
37714 stub is allowed to delay erase operation until the @samp{vFlashDone}
37715 packet is received.
37725 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
37726 @cindex @samp{vFlashWrite} packet
37727 Direct the stub to write data to flash address @var{addr}. The data
37728 is passed in binary form using the same encoding as for the @samp{X}
37729 packet (@pxref{Binary Data}). The memory ranges specified by
37730 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
37731 not overlap, and must appear in order of increasing addresses
37732 (although @samp{vFlashErase} packets for higher addresses may already
37733 have been received; the ordering is guaranteed only between
37734 @samp{vFlashWrite} packets). If a packet writes to an address that was
37735 neither erased by a preceding @samp{vFlashErase} packet nor by some other
37736 target-specific method, the results are unpredictable.
37744 for vFlashWrite addressing non-flash memory
37750 @cindex @samp{vFlashDone} packet
37751 Indicate to the stub that flash programming operation is finished.
37752 The stub is permitted to delay or batch the effects of a group of
37753 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
37754 @samp{vFlashDone} packet is received. The contents of the affected
37755 regions of flash memory are unpredictable until the @samp{vFlashDone}
37756 request is completed.
37758 @item vKill;@var{pid}
37759 @cindex @samp{vKill} packet
37760 @anchor{vKill packet}
37761 Kill the process with the specified process ID @var{pid}, which is a
37762 hexadecimal integer identifying the process. This packet is used in
37763 preference to @samp{k} when multiprocess protocol extensions are
37764 supported; see @ref{multiprocess extensions}.
37774 @item vMustReplyEmpty
37775 @cindex @samp{vMustReplyEmpty} packet
37776 The correct reply to an unknown @samp{v} packet is to return the empty
37777 string, however, some older versions of @command{gdbserver} would
37778 incorrectly return @samp{OK} for unknown @samp{v} packets.
37780 The @samp{vMustReplyEmpty} is used as a feature test to check how
37781 @command{gdbserver} handles unknown packets, it is important that this
37782 packet be handled in the same way as other unknown @samp{v} packets.
37783 If this packet is handled differently to other unknown @samp{v}
37784 packets then it is possile that @value{GDBN} may run into problems in
37785 other areas, specifically around use of @samp{vFile:setfs:}.
37787 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
37788 @cindex @samp{vRun} packet
37789 Run the program @var{filename}, passing it each @var{argument} on its
37790 command line. The file and arguments are hex-encoded strings. If
37791 @var{filename} is an empty string, the stub may use a default program
37792 (e.g.@: the last program run). The program is created in the stopped
37795 @c FIXME: What about non-stop mode?
37797 This packet is only available in extended mode (@pxref{extended mode}).
37803 @item @r{Any stop packet}
37804 for success (@pxref{Stop Reply Packets})
37808 @cindex @samp{vStopped} packet
37809 @xref{Notification Packets}.
37811 @item X @var{addr},@var{length}:@var{XX@dots{}}
37813 @cindex @samp{X} packet
37814 Write data to memory, where the data is transmitted in binary.
37815 Memory is specified by its address @var{addr} and number of addressable memory
37816 units @var{length} (@pxref{addressable memory unit});
37817 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
37827 @item z @var{type},@var{addr},@var{kind}
37828 @itemx Z @var{type},@var{addr},@var{kind}
37829 @anchor{insert breakpoint or watchpoint packet}
37830 @cindex @samp{z} packet
37831 @cindex @samp{Z} packets
37832 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
37833 watchpoint starting at address @var{address} of kind @var{kind}.
37835 Each breakpoint and watchpoint packet @var{type} is documented
37838 @emph{Implementation notes: A remote target shall return an empty string
37839 for an unrecognized breakpoint or watchpoint packet @var{type}. A
37840 remote target shall support either both or neither of a given
37841 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
37842 avoid potential problems with duplicate packets, the operations should
37843 be implemented in an idempotent way.}
37845 @item z0,@var{addr},@var{kind}
37846 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37847 @cindex @samp{z0} packet
37848 @cindex @samp{Z0} packet
37849 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
37850 @var{addr} of type @var{kind}.
37852 A software breakpoint is implemented by replacing the instruction at
37853 @var{addr} with a software breakpoint or trap instruction. The
37854 @var{kind} is target-specific and typically indicates the size of the
37855 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
37856 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
37857 architectures have additional meanings for @var{kind}
37858 (@pxref{Architecture-Specific Protocol Details}); if no
37859 architecture-specific value is being used, it should be @samp{0}.
37860 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
37861 conditional expressions in bytecode form that should be evaluated on
37862 the target's side. These are the conditions that should be taken into
37863 consideration when deciding if the breakpoint trigger should be
37864 reported back to @value{GDBN}.
37866 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
37867 for how to best report a software breakpoint event to @value{GDBN}.
37869 The @var{cond_list} parameter is comprised of a series of expressions,
37870 concatenated without separators. Each expression has the following form:
37874 @item X @var{len},@var{expr}
37875 @var{len} is the length of the bytecode expression and @var{expr} is the
37876 actual conditional expression in bytecode form.
37880 The optional @var{cmd_list} parameter introduces commands that may be
37881 run on the target, rather than being reported back to @value{GDBN}.
37882 The parameter starts with a numeric flag @var{persist}; if the flag is
37883 nonzero, then the breakpoint may remain active and the commands
37884 continue to be run even when @value{GDBN} disconnects from the target.
37885 Following this flag is a series of expressions concatenated with no
37886 separators. Each expression has the following form:
37890 @item X @var{len},@var{expr}
37891 @var{len} is the length of the bytecode expression and @var{expr} is the
37892 actual commands expression in bytecode form.
37896 @emph{Implementation note: It is possible for a target to copy or move
37897 code that contains software breakpoints (e.g., when implementing
37898 overlays). The behavior of this packet, in the presence of such a
37899 target, is not defined.}
37911 @item z1,@var{addr},@var{kind}
37912 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37913 @cindex @samp{z1} packet
37914 @cindex @samp{Z1} packet
37915 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
37916 address @var{addr}.
37918 A hardware breakpoint is implemented using a mechanism that is not
37919 dependent on being able to modify the target's memory. The
37920 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
37921 same meaning as in @samp{Z0} packets.
37923 @emph{Implementation note: A hardware breakpoint is not affected by code
37936 @item z2,@var{addr},@var{kind}
37937 @itemx Z2,@var{addr},@var{kind}
37938 @cindex @samp{z2} packet
37939 @cindex @samp{Z2} packet
37940 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
37941 The number of bytes to watch is specified by @var{kind}.
37953 @item z3,@var{addr},@var{kind}
37954 @itemx Z3,@var{addr},@var{kind}
37955 @cindex @samp{z3} packet
37956 @cindex @samp{Z3} packet
37957 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
37958 The number of bytes to watch is specified by @var{kind}.
37970 @item z4,@var{addr},@var{kind}
37971 @itemx Z4,@var{addr},@var{kind}
37972 @cindex @samp{z4} packet
37973 @cindex @samp{Z4} packet
37974 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
37975 The number of bytes to watch is specified by @var{kind}.
37989 @node Stop Reply Packets
37990 @section Stop Reply Packets
37991 @cindex stop reply packets
37993 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
37994 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
37995 receive any of the below as a reply. Except for @samp{?}
37996 and @samp{vStopped}, that reply is only returned
37997 when the target halts. In the below the exact meaning of @dfn{signal
37998 number} is defined by the header @file{include/gdb/signals.h} in the
37999 @value{GDBN} source code.
38001 In non-stop mode, the server will simply reply @samp{OK} to commands
38002 such as @samp{vCont}; any stop will be the subject of a future
38003 notification. @xref{Remote Non-Stop}.
38005 As in the description of request packets, we include spaces in the
38006 reply templates for clarity; these are not part of the reply packet's
38007 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
38013 The program received signal number @var{AA} (a two-digit hexadecimal
38014 number). This is equivalent to a @samp{T} response with no
38015 @var{n}:@var{r} pairs.
38017 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
38018 @cindex @samp{T} packet reply
38019 The program received signal number @var{AA} (a two-digit hexadecimal
38020 number). This is equivalent to an @samp{S} response, except that the
38021 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38022 and other information directly in the stop reply packet, reducing
38023 round-trip latency. Single-step and breakpoint traps are reported
38024 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38028 If @var{n} is a hexadecimal number, it is a register number, and the
38029 corresponding @var{r} gives that register's value. The data @var{r} is a
38030 series of bytes in target byte order, with each byte given by a
38031 two-digit hex number.
38034 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38035 the stopped thread, as specified in @ref{thread-id syntax}.
38038 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38039 the core on which the stop event was detected.
38042 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38043 specific event that stopped the target. The currently defined stop
38044 reasons are listed below. The @var{aa} should be @samp{05}, the trap
38045 signal. At most one stop reason should be present.
38048 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38049 and go on to the next; this allows us to extend the protocol in the
38053 The currently defined stop reasons are:
38059 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38062 @item syscall_entry
38063 @itemx syscall_return
38064 The packet indicates a syscall entry or return, and @var{r} is the
38065 syscall number, in hex.
38067 @cindex shared library events, remote reply
38069 The packet indicates that the loaded libraries have changed.
38070 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38071 list of loaded libraries. The @var{r} part is ignored.
38073 @cindex replay log events, remote reply
38075 The packet indicates that the target cannot continue replaying
38076 logged execution events, because it has reached the end (or the
38077 beginning when executing backward) of the log. The value of @var{r}
38078 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38079 for more information.
38082 @anchor{swbreak stop reason}
38083 The packet indicates a software breakpoint instruction was executed,
38084 irrespective of whether it was @value{GDBN} that planted the
38085 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
38086 part must be left empty.
38088 On some architectures, such as x86, at the architecture level, when a
38089 breakpoint instruction executes the program counter points at the
38090 breakpoint address plus an offset. On such targets, the stub is
38091 responsible for adjusting the PC to point back at the breakpoint
38094 This packet should not be sent by default; older @value{GDBN} versions
38095 did not support it. @value{GDBN} requests it, by supplying an
38096 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38097 remote stub must also supply the appropriate @samp{qSupported} feature
38098 indicating support.
38100 This packet is required for correct non-stop mode operation.
38103 The packet indicates the target stopped for a hardware breakpoint.
38104 The @var{r} part must be left empty.
38106 The same remarks about @samp{qSupported} and non-stop mode above
38109 @cindex fork events, remote reply
38111 The packet indicates that @code{fork} was called, and @var{r}
38112 is the thread ID of the new child process. Refer to
38113 @ref{thread-id syntax} for the format of the @var{thread-id}
38114 field. This packet is only applicable to targets that support
38117 This packet should not be sent by default; older @value{GDBN} versions
38118 did not support it. @value{GDBN} requests it, by supplying an
38119 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38120 remote stub must also supply the appropriate @samp{qSupported} feature
38121 indicating support.
38123 @cindex vfork events, remote reply
38125 The packet indicates that @code{vfork} was called, and @var{r}
38126 is the thread ID of the new child process. Refer to
38127 @ref{thread-id syntax} for the format of the @var{thread-id}
38128 field. This packet is only applicable to targets that support
38131 This packet should not be sent by default; older @value{GDBN} versions
38132 did not support it. @value{GDBN} requests it, by supplying an
38133 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38134 remote stub must also supply the appropriate @samp{qSupported} feature
38135 indicating support.
38137 @cindex vforkdone events, remote reply
38139 The packet indicates that a child process created by a vfork
38140 has either called @code{exec} or terminated, so that the
38141 address spaces of the parent and child process are no longer
38142 shared. The @var{r} part is ignored. This packet is only
38143 applicable to targets that support vforkdone events.
38145 This packet should not be sent by default; older @value{GDBN} versions
38146 did not support it. @value{GDBN} requests it, by supplying an
38147 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38148 remote stub must also supply the appropriate @samp{qSupported} feature
38149 indicating support.
38151 @cindex exec events, remote reply
38153 The packet indicates that @code{execve} was called, and @var{r}
38154 is the absolute pathname of the file that was executed, in hex.
38155 This packet is only applicable to targets that support exec events.
38157 This packet should not be sent by default; older @value{GDBN} versions
38158 did not support it. @value{GDBN} requests it, by supplying an
38159 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38160 remote stub must also supply the appropriate @samp{qSupported} feature
38161 indicating support.
38163 @cindex thread create event, remote reply
38164 @anchor{thread create event}
38166 The packet indicates that the thread was just created. The new thread
38167 is stopped until @value{GDBN} sets it running with a resumption packet
38168 (@pxref{vCont packet}). This packet should not be sent by default;
38169 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
38170 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
38171 @var{r} part is ignored.
38176 @itemx W @var{AA} ; process:@var{pid}
38177 The process exited, and @var{AA} is the exit status. This is only
38178 applicable to certain targets.
38180 The second form of the response, including the process ID of the
38181 exited process, can be used only when @value{GDBN} has reported
38182 support for multiprocess protocol extensions; see @ref{multiprocess
38183 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
38187 @itemx X @var{AA} ; process:@var{pid}
38188 The process terminated with signal @var{AA}.
38190 The second form of the response, including the process ID of the
38191 terminated process, can be used only when @value{GDBN} has reported
38192 support for multiprocess protocol extensions; see @ref{multiprocess
38193 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
38196 @anchor{thread exit event}
38197 @cindex thread exit event, remote reply
38198 @item w @var{AA} ; @var{tid}
38200 The thread exited, and @var{AA} is the exit status. This response
38201 should not be sent by default; @value{GDBN} requests it with the
38202 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
38203 @var{AA} is formatted as a big-endian hex string.
38206 There are no resumed threads left in the target. In other words, even
38207 though the process is alive, the last resumed thread has exited. For
38208 example, say the target process has two threads: thread 1 and thread
38209 2. The client leaves thread 1 stopped, and resumes thread 2, which
38210 subsequently exits. At this point, even though the process is still
38211 alive, and thus no @samp{W} stop reply is sent, no thread is actually
38212 executing either. The @samp{N} stop reply thus informs the client
38213 that it can stop waiting for stop replies. This packet should not be
38214 sent by default; older @value{GDBN} versions did not support it.
38215 @value{GDBN} requests it, by supplying an appropriate
38216 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
38217 also supply the appropriate @samp{qSupported} feature indicating
38220 @item O @var{XX}@dots{}
38221 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38222 written as the program's console output. This can happen at any time
38223 while the program is running and the debugger should continue to wait
38224 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38226 @item F @var{call-id},@var{parameter}@dots{}
38227 @var{call-id} is the identifier which says which host system call should
38228 be called. This is just the name of the function. Translation into the
38229 correct system call is only applicable as it's defined in @value{GDBN}.
38230 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38233 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38234 this very system call.
38236 The target replies with this packet when it expects @value{GDBN} to
38237 call a host system call on behalf of the target. @value{GDBN} replies
38238 with an appropriate @samp{F} packet and keeps up waiting for the next
38239 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38240 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38241 Protocol Extension}, for more details.
38245 @node General Query Packets
38246 @section General Query Packets
38247 @cindex remote query requests
38249 Packets starting with @samp{q} are @dfn{general query packets};
38250 packets starting with @samp{Q} are @dfn{general set packets}. General
38251 query and set packets are a semi-unified form for retrieving and
38252 sending information to and from the stub.
38254 The initial letter of a query or set packet is followed by a name
38255 indicating what sort of thing the packet applies to. For example,
38256 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38257 definitions with the stub. These packet names follow some
38262 The name must not contain commas, colons or semicolons.
38264 Most @value{GDBN} query and set packets have a leading upper case
38267 The names of custom vendor packets should use a company prefix, in
38268 lower case, followed by a period. For example, packets designed at
38269 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38270 foos) or @samp{Qacme.bar} (for setting bars).
38273 The name of a query or set packet should be separated from any
38274 parameters by a @samp{:}; the parameters themselves should be
38275 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38276 full packet name, and check for a separator or the end of the packet,
38277 in case two packet names share a common prefix. New packets should not begin
38278 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38279 packets predate these conventions, and have arguments without any terminator
38280 for the packet name; we suspect they are in widespread use in places that
38281 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38282 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38285 Like the descriptions of the other packets, each description here
38286 has a template showing the packet's overall syntax, followed by an
38287 explanation of the packet's meaning. We include spaces in some of the
38288 templates for clarity; these are not part of the packet's syntax. No
38289 @value{GDBN} packet uses spaces to separate its components.
38291 Here are the currently defined query and set packets:
38297 Turn on or off the agent as a helper to perform some debugging operations
38298 delegated from @value{GDBN} (@pxref{Control Agent}).
38300 @item QAllow:@var{op}:@var{val}@dots{}
38301 @cindex @samp{QAllow} packet
38302 Specify which operations @value{GDBN} expects to request of the
38303 target, as a semicolon-separated list of operation name and value
38304 pairs. Possible values for @var{op} include @samp{WriteReg},
38305 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38306 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38307 indicating that @value{GDBN} will not request the operation, or 1,
38308 indicating that it may. (The target can then use this to set up its
38309 own internals optimally, for instance if the debugger never expects to
38310 insert breakpoints, it may not need to install its own trap handler.)
38313 @cindex current thread, remote request
38314 @cindex @samp{qC} packet
38315 Return the current thread ID.
38319 @item QC @var{thread-id}
38320 Where @var{thread-id} is a thread ID as documented in
38321 @ref{thread-id syntax}.
38322 @item @r{(anything else)}
38323 Any other reply implies the old thread ID.
38326 @item qCRC:@var{addr},@var{length}
38327 @cindex CRC of memory block, remote request
38328 @cindex @samp{qCRC} packet
38329 @anchor{qCRC packet}
38330 Compute the CRC checksum of a block of memory using CRC-32 defined in
38331 IEEE 802.3. The CRC is computed byte at a time, taking the most
38332 significant bit of each byte first. The initial pattern code
38333 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
38335 @emph{Note:} This is the same CRC used in validating separate debug
38336 files (@pxref{Separate Debug Files, , Debugging Information in Separate
38337 Files}). However the algorithm is slightly different. When validating
38338 separate debug files, the CRC is computed taking the @emph{least}
38339 significant bit of each byte first, and the final result is inverted to
38340 detect trailing zeros.
38345 An error (such as memory fault)
38346 @item C @var{crc32}
38347 The specified memory region's checksum is @var{crc32}.
38350 @item QDisableRandomization:@var{value}
38351 @cindex disable address space randomization, remote request
38352 @cindex @samp{QDisableRandomization} packet
38353 Some target operating systems will randomize the virtual address space
38354 of the inferior process as a security feature, but provide a feature
38355 to disable such randomization, e.g.@: to allow for a more deterministic
38356 debugging experience. On such systems, this packet with a @var{value}
38357 of 1 directs the target to disable address space randomization for
38358 processes subsequently started via @samp{vRun} packets, while a packet
38359 with a @var{value} of 0 tells the target to enable address space
38362 This packet is only available in extended mode (@pxref{extended mode}).
38367 The request succeeded.
38370 An error occurred. The error number @var{nn} is given as hex digits.
38373 An empty reply indicates that @samp{QDisableRandomization} is not supported
38377 This packet is not probed by default; the remote stub must request it,
38378 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38379 This should only be done on targets that actually support disabling
38380 address space randomization.
38382 @item QStartupWithShell:@var{value}
38383 @cindex startup with shell, remote request
38384 @cindex @samp{QStartupWithShell} packet
38385 On UNIX-like targets, it is possible to start the inferior using a
38386 shell program. This is the default behavior on both @value{GDBN} and
38387 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
38388 used to inform @command{gdbserver} whether it should start the
38389 inferior using a shell or not.
38391 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
38392 to start the inferior. If @var{value} is @samp{1},
38393 @command{gdbserver} will use a shell to start the inferior. All other
38394 values are considered an error.
38396 This packet is only available in extended mode (@pxref{extended
38402 The request succeeded.
38405 An error occurred. The error number @var{nn} is given as hex digits.
38408 This packet is not probed by default; the remote stub must request it,
38409 by supplying an appropriate @samp{qSupported} response
38410 (@pxref{qSupported}). This should only be done on targets that
38411 actually support starting the inferior using a shell.
38413 Use of this packet is controlled by the @code{set startup-with-shell}
38414 command; @pxref{set startup-with-shell}.
38416 @item QEnvironmentHexEncoded:@var{hex-value}
38417 @anchor{QEnvironmentHexEncoded}
38418 @cindex set environment variable, remote request
38419 @cindex @samp{QEnvironmentHexEncoded} packet
38420 On UNIX-like targets, it is possible to set environment variables that
38421 will be passed to the inferior during the startup process. This
38422 packet is used to inform @command{gdbserver} of an environment
38423 variable that has been defined by the user on @value{GDBN} (@pxref{set
38426 The packet is composed by @var{hex-value}, an hex encoded
38427 representation of the @var{name=value} format representing an
38428 environment variable. The name of the environment variable is
38429 represented by @var{name}, and the value to be assigned to the
38430 environment variable is represented by @var{value}. If the variable
38431 has no value (i.e., the value is @code{null}), then @var{value} will
38434 This packet is only available in extended mode (@pxref{extended
38440 The request succeeded.
38443 This packet is not probed by default; the remote stub must request it,
38444 by supplying an appropriate @samp{qSupported} response
38445 (@pxref{qSupported}). This should only be done on targets that
38446 actually support passing environment variables to the starting
38449 This packet is related to the @code{set environment} command;
38450 @pxref{set environment}.
38452 @item QEnvironmentUnset:@var{hex-value}
38453 @anchor{QEnvironmentUnset}
38454 @cindex unset environment variable, remote request
38455 @cindex @samp{QEnvironmentUnset} packet
38456 On UNIX-like targets, it is possible to unset environment variables
38457 before starting the inferior in the remote target. This packet is
38458 used to inform @command{gdbserver} of an environment variable that has
38459 been unset by the user on @value{GDBN} (@pxref{unset environment}).
38461 The packet is composed by @var{hex-value}, an hex encoded
38462 representation of the name of the environment variable to be unset.
38464 This packet is only available in extended mode (@pxref{extended
38470 The request succeeded.
38473 This packet is not probed by default; the remote stub must request it,
38474 by supplying an appropriate @samp{qSupported} response
38475 (@pxref{qSupported}). This should only be done on targets that
38476 actually support passing environment variables to the starting
38479 This packet is related to the @code{unset environment} command;
38480 @pxref{unset environment}.
38482 @item QEnvironmentReset
38483 @anchor{QEnvironmentReset}
38484 @cindex reset environment, remote request
38485 @cindex @samp{QEnvironmentReset} packet
38486 On UNIX-like targets, this packet is used to reset the state of
38487 environment variables in the remote target before starting the
38488 inferior. In this context, reset means unsetting all environment
38489 variables that were previously set by the user (i.e., were not
38490 initially present in the environment). It is sent to
38491 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
38492 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
38493 (@pxref{QEnvironmentUnset}) packets.
38495 This packet is only available in extended mode (@pxref{extended
38501 The request succeeded.
38504 This packet is not probed by default; the remote stub must request it,
38505 by supplying an appropriate @samp{qSupported} response
38506 (@pxref{qSupported}). This should only be done on targets that
38507 actually support passing environment variables to the starting
38510 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
38511 @anchor{QSetWorkingDir packet}
38512 @cindex set working directory, remote request
38513 @cindex @samp{QSetWorkingDir} packet
38514 This packet is used to inform the remote server of the intended
38515 current working directory for programs that are going to be executed.
38517 The packet is composed by @var{directory}, an hex encoded
38518 representation of the directory that the remote inferior will use as
38519 its current working directory. If @var{directory} is an empty string,
38520 the remote server should reset the inferior's current working
38521 directory to its original, empty value.
38523 This packet is only available in extended mode (@pxref{extended
38529 The request succeeded.
38533 @itemx qsThreadInfo
38534 @cindex list active threads, remote request
38535 @cindex @samp{qfThreadInfo} packet
38536 @cindex @samp{qsThreadInfo} packet
38537 Obtain a list of all active thread IDs from the target (OS). Since there
38538 may be too many active threads to fit into one reply packet, this query
38539 works iteratively: it may require more than one query/reply sequence to
38540 obtain the entire list of threads. The first query of the sequence will
38541 be the @samp{qfThreadInfo} query; subsequent queries in the
38542 sequence will be the @samp{qsThreadInfo} query.
38544 NOTE: This packet replaces the @samp{qL} query (see below).
38548 @item m @var{thread-id}
38550 @item m @var{thread-id},@var{thread-id}@dots{}
38551 a comma-separated list of thread IDs
38553 (lower case letter @samp{L}) denotes end of list.
38556 In response to each query, the target will reply with a list of one or
38557 more thread IDs, separated by commas.
38558 @value{GDBN} will respond to each reply with a request for more thread
38559 ids (using the @samp{qs} form of the query), until the target responds
38560 with @samp{l} (lower-case ell, for @dfn{last}).
38561 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
38564 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
38565 initial connection with the remote target, and the very first thread ID
38566 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
38567 message. Therefore, the stub should ensure that the first thread ID in
38568 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
38570 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
38571 @cindex get thread-local storage address, remote request
38572 @cindex @samp{qGetTLSAddr} packet
38573 Fetch the address associated with thread local storage specified
38574 by @var{thread-id}, @var{offset}, and @var{lm}.
38576 @var{thread-id} is the thread ID associated with the
38577 thread for which to fetch the TLS address. @xref{thread-id syntax}.
38579 @var{offset} is the (big endian, hex encoded) offset associated with the
38580 thread local variable. (This offset is obtained from the debug
38581 information associated with the variable.)
38583 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
38584 load module associated with the thread local storage. For example,
38585 a @sc{gnu}/Linux system will pass the link map address of the shared
38586 object associated with the thread local storage under consideration.
38587 Other operating environments may choose to represent the load module
38588 differently, so the precise meaning of this parameter will vary.
38592 @item @var{XX}@dots{}
38593 Hex encoded (big endian) bytes representing the address of the thread
38594 local storage requested.
38597 An error occurred. The error number @var{nn} is given as hex digits.
38600 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
38603 @item qGetTIBAddr:@var{thread-id}
38604 @cindex get thread information block address
38605 @cindex @samp{qGetTIBAddr} packet
38606 Fetch address of the Windows OS specific Thread Information Block.
38608 @var{thread-id} is the thread ID associated with the thread.
38612 @item @var{XX}@dots{}
38613 Hex encoded (big endian) bytes representing the linear address of the
38614 thread information block.
38617 An error occured. This means that either the thread was not found, or the
38618 address could not be retrieved.
38621 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
38624 @item qL @var{startflag} @var{threadcount} @var{nextthread}
38625 Obtain thread information from RTOS. Where: @var{startflag} (one hex
38626 digit) is one to indicate the first query and zero to indicate a
38627 subsequent query; @var{threadcount} (two hex digits) is the maximum
38628 number of threads the response packet can contain; and @var{nextthread}
38629 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
38630 returned in the response as @var{argthread}.
38632 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
38636 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
38637 Where: @var{count} (two hex digits) is the number of threads being
38638 returned; @var{done} (one hex digit) is zero to indicate more threads
38639 and one indicates no further threads; @var{argthreadid} (eight hex
38640 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
38641 is a sequence of thread IDs, @var{threadid} (eight hex
38642 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
38646 @cindex section offsets, remote request
38647 @cindex @samp{qOffsets} packet
38648 Get section offsets that the target used when relocating the downloaded
38653 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
38654 Relocate the @code{Text} section by @var{xxx} from its original address.
38655 Relocate the @code{Data} section by @var{yyy} from its original address.
38656 If the object file format provides segment information (e.g.@: @sc{elf}
38657 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
38658 segments by the supplied offsets.
38660 @emph{Note: while a @code{Bss} offset may be included in the response,
38661 @value{GDBN} ignores this and instead applies the @code{Data} offset
38662 to the @code{Bss} section.}
38664 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
38665 Relocate the first segment of the object file, which conventionally
38666 contains program code, to a starting address of @var{xxx}. If
38667 @samp{DataSeg} is specified, relocate the second segment, which
38668 conventionally contains modifiable data, to a starting address of
38669 @var{yyy}. @value{GDBN} will report an error if the object file
38670 does not contain segment information, or does not contain at least
38671 as many segments as mentioned in the reply. Extra segments are
38672 kept at fixed offsets relative to the last relocated segment.
38675 @item qP @var{mode} @var{thread-id}
38676 @cindex thread information, remote request
38677 @cindex @samp{qP} packet
38678 Returns information on @var{thread-id}. Where: @var{mode} is a hex
38679 encoded 32 bit mode; @var{thread-id} is a thread ID
38680 (@pxref{thread-id syntax}).
38682 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
38685 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
38689 @cindex non-stop mode, remote request
38690 @cindex @samp{QNonStop} packet
38692 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
38693 @xref{Remote Non-Stop}, for more information.
38698 The request succeeded.
38701 An error occurred. The error number @var{nn} is given as hex digits.
38704 An empty reply indicates that @samp{QNonStop} is not supported by
38708 This packet is not probed by default; the remote stub must request it,
38709 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38710 Use of this packet is controlled by the @code{set non-stop} command;
38711 @pxref{Non-Stop Mode}.
38713 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
38714 @itemx QCatchSyscalls:0
38715 @cindex catch syscalls from inferior, remote request
38716 @cindex @samp{QCatchSyscalls} packet
38717 @anchor{QCatchSyscalls}
38718 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
38719 catching syscalls from the inferior process.
38721 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
38722 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
38723 is listed, every system call should be reported.
38725 Note that if a syscall not in the list is reported, @value{GDBN} will
38726 still filter the event according to its own list from all corresponding
38727 @code{catch syscall} commands. However, it is more efficient to only
38728 report the requested syscalls.
38730 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
38731 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
38733 If the inferior process execs, the state of @samp{QCatchSyscalls} is
38734 kept for the new process too. On targets where exec may affect syscall
38735 numbers, for example with exec between 32 and 64-bit processes, the
38736 client should send a new packet with the new syscall list.
38741 The request succeeded.
38744 An error occurred. @var{nn} are hex digits.
38747 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
38751 Use of this packet is controlled by the @code{set remote catch-syscalls}
38752 command (@pxref{Remote Configuration, set remote catch-syscalls}).
38753 This packet is not probed by default; the remote stub must request it,
38754 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38756 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38757 @cindex pass signals to inferior, remote request
38758 @cindex @samp{QPassSignals} packet
38759 @anchor{QPassSignals}
38760 Each listed @var{signal} should be passed directly to the inferior process.
38761 Signals are numbered identically to continue packets and stop replies
38762 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38763 strictly greater than the previous item. These signals do not need to stop
38764 the inferior, or be reported to @value{GDBN}. All other signals should be
38765 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
38766 combine; any earlier @samp{QPassSignals} list is completely replaced by the
38767 new list. This packet improves performance when using @samp{handle
38768 @var{signal} nostop noprint pass}.
38773 The request succeeded.
38776 An error occurred. The error number @var{nn} is given as hex digits.
38779 An empty reply indicates that @samp{QPassSignals} is not supported by
38783 Use of this packet is controlled by the @code{set remote pass-signals}
38784 command (@pxref{Remote Configuration, set remote pass-signals}).
38785 This packet is not probed by default; the remote stub must request it,
38786 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38788 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38789 @cindex signals the inferior may see, remote request
38790 @cindex @samp{QProgramSignals} packet
38791 @anchor{QProgramSignals}
38792 Each listed @var{signal} may be delivered to the inferior process.
38793 Others should be silently discarded.
38795 In some cases, the remote stub may need to decide whether to deliver a
38796 signal to the program or not without @value{GDBN} involvement. One
38797 example of that is while detaching --- the program's threads may have
38798 stopped for signals that haven't yet had a chance of being reported to
38799 @value{GDBN}, and so the remote stub can use the signal list specified
38800 by this packet to know whether to deliver or ignore those pending
38803 This does not influence whether to deliver a signal as requested by a
38804 resumption packet (@pxref{vCont packet}).
38806 Signals are numbered identically to continue packets and stop replies
38807 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38808 strictly greater than the previous item. Multiple
38809 @samp{QProgramSignals} packets do not combine; any earlier
38810 @samp{QProgramSignals} list is completely replaced by the new list.
38815 The request succeeded.
38818 An error occurred. The error number @var{nn} is given as hex digits.
38821 An empty reply indicates that @samp{QProgramSignals} is not supported
38825 Use of this packet is controlled by the @code{set remote program-signals}
38826 command (@pxref{Remote Configuration, set remote program-signals}).
38827 This packet is not probed by default; the remote stub must request it,
38828 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38830 @anchor{QThreadEvents}
38831 @item QThreadEvents:1
38832 @itemx QThreadEvents:0
38833 @cindex thread create/exit events, remote request
38834 @cindex @samp{QThreadEvents} packet
38836 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
38837 reporting of thread create and exit events. @xref{thread create
38838 event}, for the reply specifications. For example, this is used in
38839 non-stop mode when @value{GDBN} stops a set of threads and
38840 synchronously waits for the their corresponding stop replies. Without
38841 exit events, if one of the threads exits, @value{GDBN} would hang
38842 forever not knowing that it should no longer expect a stop for that
38843 same thread. @value{GDBN} does not enable this feature unless the
38844 stub reports that it supports it by including @samp{QThreadEvents+} in
38845 its @samp{qSupported} reply.
38850 The request succeeded.
38853 An error occurred. The error number @var{nn} is given as hex digits.
38856 An empty reply indicates that @samp{QThreadEvents} is not supported by
38860 Use of this packet is controlled by the @code{set remote thread-events}
38861 command (@pxref{Remote Configuration, set remote thread-events}).
38863 @item qRcmd,@var{command}
38864 @cindex execute remote command, remote request
38865 @cindex @samp{qRcmd} packet
38866 @var{command} (hex encoded) is passed to the local interpreter for
38867 execution. Invalid commands should be reported using the output
38868 string. Before the final result packet, the target may also respond
38869 with a number of intermediate @samp{O@var{output}} console output
38870 packets. @emph{Implementors should note that providing access to a
38871 stubs's interpreter may have security implications}.
38876 A command response with no output.
38878 A command response with the hex encoded output string @var{OUTPUT}.
38880 Indicate a badly formed request.
38882 An empty reply indicates that @samp{qRcmd} is not recognized.
38885 (Note that the @code{qRcmd} packet's name is separated from the
38886 command by a @samp{,}, not a @samp{:}, contrary to the naming
38887 conventions above. Please don't use this packet as a model for new
38890 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
38891 @cindex searching memory, in remote debugging
38893 @cindex @samp{qSearch:memory} packet
38895 @cindex @samp{qSearch memory} packet
38896 @anchor{qSearch memory}
38897 Search @var{length} bytes at @var{address} for @var{search-pattern}.
38898 Both @var{address} and @var{length} are encoded in hex;
38899 @var{search-pattern} is a sequence of bytes, also hex encoded.
38904 The pattern was not found.
38906 The pattern was found at @var{address}.
38908 A badly formed request or an error was encountered while searching memory.
38910 An empty reply indicates that @samp{qSearch:memory} is not recognized.
38913 @item QStartNoAckMode
38914 @cindex @samp{QStartNoAckMode} packet
38915 @anchor{QStartNoAckMode}
38916 Request that the remote stub disable the normal @samp{+}/@samp{-}
38917 protocol acknowledgments (@pxref{Packet Acknowledgment}).
38922 The stub has switched to no-acknowledgment mode.
38923 @value{GDBN} acknowledges this reponse,
38924 but neither the stub nor @value{GDBN} shall send or expect further
38925 @samp{+}/@samp{-} acknowledgments in the current connection.
38927 An empty reply indicates that the stub does not support no-acknowledgment mode.
38930 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
38931 @cindex supported packets, remote query
38932 @cindex features of the remote protocol
38933 @cindex @samp{qSupported} packet
38934 @anchor{qSupported}
38935 Tell the remote stub about features supported by @value{GDBN}, and
38936 query the stub for features it supports. This packet allows
38937 @value{GDBN} and the remote stub to take advantage of each others'
38938 features. @samp{qSupported} also consolidates multiple feature probes
38939 at startup, to improve @value{GDBN} performance---a single larger
38940 packet performs better than multiple smaller probe packets on
38941 high-latency links. Some features may enable behavior which must not
38942 be on by default, e.g.@: because it would confuse older clients or
38943 stubs. Other features may describe packets which could be
38944 automatically probed for, but are not. These features must be
38945 reported before @value{GDBN} will use them. This ``default
38946 unsupported'' behavior is not appropriate for all packets, but it
38947 helps to keep the initial connection time under control with new
38948 versions of @value{GDBN} which support increasing numbers of packets.
38952 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
38953 The stub supports or does not support each returned @var{stubfeature},
38954 depending on the form of each @var{stubfeature} (see below for the
38957 An empty reply indicates that @samp{qSupported} is not recognized,
38958 or that no features needed to be reported to @value{GDBN}.
38961 The allowed forms for each feature (either a @var{gdbfeature} in the
38962 @samp{qSupported} packet, or a @var{stubfeature} in the response)
38966 @item @var{name}=@var{value}
38967 The remote protocol feature @var{name} is supported, and associated
38968 with the specified @var{value}. The format of @var{value} depends
38969 on the feature, but it must not include a semicolon.
38971 The remote protocol feature @var{name} is supported, and does not
38972 need an associated value.
38974 The remote protocol feature @var{name} is not supported.
38976 The remote protocol feature @var{name} may be supported, and
38977 @value{GDBN} should auto-detect support in some other way when it is
38978 needed. This form will not be used for @var{gdbfeature} notifications,
38979 but may be used for @var{stubfeature} responses.
38982 Whenever the stub receives a @samp{qSupported} request, the
38983 supplied set of @value{GDBN} features should override any previous
38984 request. This allows @value{GDBN} to put the stub in a known
38985 state, even if the stub had previously been communicating with
38986 a different version of @value{GDBN}.
38988 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
38993 This feature indicates whether @value{GDBN} supports multiprocess
38994 extensions to the remote protocol. @value{GDBN} does not use such
38995 extensions unless the stub also reports that it supports them by
38996 including @samp{multiprocess+} in its @samp{qSupported} reply.
38997 @xref{multiprocess extensions}, for details.
39000 This feature indicates that @value{GDBN} supports the XML target
39001 description. If the stub sees @samp{xmlRegisters=} with target
39002 specific strings separated by a comma, it will report register
39006 This feature indicates whether @value{GDBN} supports the
39007 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
39008 instruction reply packet}).
39011 This feature indicates whether @value{GDBN} supports the swbreak stop
39012 reason in stop replies. @xref{swbreak stop reason}, for details.
39015 This feature indicates whether @value{GDBN} supports the hwbreak stop
39016 reason in stop replies. @xref{swbreak stop reason}, for details.
39019 This feature indicates whether @value{GDBN} supports fork event
39020 extensions to the remote protocol. @value{GDBN} does not use such
39021 extensions unless the stub also reports that it supports them by
39022 including @samp{fork-events+} in its @samp{qSupported} reply.
39025 This feature indicates whether @value{GDBN} supports vfork event
39026 extensions to the remote protocol. @value{GDBN} does not use such
39027 extensions unless the stub also reports that it supports them by
39028 including @samp{vfork-events+} in its @samp{qSupported} reply.
39031 This feature indicates whether @value{GDBN} supports exec event
39032 extensions to the remote protocol. @value{GDBN} does not use such
39033 extensions unless the stub also reports that it supports them by
39034 including @samp{exec-events+} in its @samp{qSupported} reply.
39036 @item vContSupported
39037 This feature indicates whether @value{GDBN} wants to know the
39038 supported actions in the reply to @samp{vCont?} packet.
39041 Stubs should ignore any unknown values for
39042 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
39043 packet supports receiving packets of unlimited length (earlier
39044 versions of @value{GDBN} may reject overly long responses). Additional values
39045 for @var{gdbfeature} may be defined in the future to let the stub take
39046 advantage of new features in @value{GDBN}, e.g.@: incompatible
39047 improvements in the remote protocol---the @samp{multiprocess} feature is
39048 an example of such a feature. The stub's reply should be independent
39049 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
39050 describes all the features it supports, and then the stub replies with
39051 all the features it supports.
39053 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
39054 responses, as long as each response uses one of the standard forms.
39056 Some features are flags. A stub which supports a flag feature
39057 should respond with a @samp{+} form response. Other features
39058 require values, and the stub should respond with an @samp{=}
39061 Each feature has a default value, which @value{GDBN} will use if
39062 @samp{qSupported} is not available or if the feature is not mentioned
39063 in the @samp{qSupported} response. The default values are fixed; a
39064 stub is free to omit any feature responses that match the defaults.
39066 Not all features can be probed, but for those which can, the probing
39067 mechanism is useful: in some cases, a stub's internal
39068 architecture may not allow the protocol layer to know some information
39069 about the underlying target in advance. This is especially common in
39070 stubs which may be configured for multiple targets.
39072 These are the currently defined stub features and their properties:
39074 @multitable @columnfractions 0.35 0.2 0.12 0.2
39075 @c NOTE: The first row should be @headitem, but we do not yet require
39076 @c a new enough version of Texinfo (4.7) to use @headitem.
39078 @tab Value Required
39082 @item @samp{PacketSize}
39087 @item @samp{qXfer:auxv:read}
39092 @item @samp{qXfer:btrace:read}
39097 @item @samp{qXfer:btrace-conf:read}
39102 @item @samp{qXfer:exec-file:read}
39107 @item @samp{qXfer:features:read}
39112 @item @samp{qXfer:libraries:read}
39117 @item @samp{qXfer:libraries-svr4:read}
39122 @item @samp{augmented-libraries-svr4-read}
39127 @item @samp{qXfer:memory-map:read}
39132 @item @samp{qXfer:sdata:read}
39137 @item @samp{qXfer:spu:read}
39142 @item @samp{qXfer:spu:write}
39147 @item @samp{qXfer:siginfo:read}
39152 @item @samp{qXfer:siginfo:write}
39157 @item @samp{qXfer:threads:read}
39162 @item @samp{qXfer:traceframe-info:read}
39167 @item @samp{qXfer:uib:read}
39172 @item @samp{qXfer:fdpic:read}
39177 @item @samp{Qbtrace:off}
39182 @item @samp{Qbtrace:bts}
39187 @item @samp{Qbtrace:pt}
39192 @item @samp{Qbtrace-conf:bts:size}
39197 @item @samp{Qbtrace-conf:pt:size}
39202 @item @samp{QNonStop}
39207 @item @samp{QCatchSyscalls}
39212 @item @samp{QPassSignals}
39217 @item @samp{QStartNoAckMode}
39222 @item @samp{multiprocess}
39227 @item @samp{ConditionalBreakpoints}
39232 @item @samp{ConditionalTracepoints}
39237 @item @samp{ReverseContinue}
39242 @item @samp{ReverseStep}
39247 @item @samp{TracepointSource}
39252 @item @samp{QAgent}
39257 @item @samp{QAllow}
39262 @item @samp{QDisableRandomization}
39267 @item @samp{EnableDisableTracepoints}
39272 @item @samp{QTBuffer:size}
39277 @item @samp{tracenz}
39282 @item @samp{BreakpointCommands}
39287 @item @samp{swbreak}
39292 @item @samp{hwbreak}
39297 @item @samp{fork-events}
39302 @item @samp{vfork-events}
39307 @item @samp{exec-events}
39312 @item @samp{QThreadEvents}
39317 @item @samp{no-resumed}
39324 These are the currently defined stub features, in more detail:
39327 @cindex packet size, remote protocol
39328 @item PacketSize=@var{bytes}
39329 The remote stub can accept packets up to at least @var{bytes} in
39330 length. @value{GDBN} will send packets up to this size for bulk
39331 transfers, and will never send larger packets. This is a limit on the
39332 data characters in the packet, including the frame and checksum.
39333 There is no trailing NUL byte in a remote protocol packet; if the stub
39334 stores packets in a NUL-terminated format, it should allow an extra
39335 byte in its buffer for the NUL. If this stub feature is not supported,
39336 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39338 @item qXfer:auxv:read
39339 The remote stub understands the @samp{qXfer:auxv:read} packet
39340 (@pxref{qXfer auxiliary vector read}).
39342 @item qXfer:btrace:read
39343 The remote stub understands the @samp{qXfer:btrace:read}
39344 packet (@pxref{qXfer btrace read}).
39346 @item qXfer:btrace-conf:read
39347 The remote stub understands the @samp{qXfer:btrace-conf:read}
39348 packet (@pxref{qXfer btrace-conf read}).
39350 @item qXfer:exec-file:read
39351 The remote stub understands the @samp{qXfer:exec-file:read} packet
39352 (@pxref{qXfer executable filename read}).
39354 @item qXfer:features:read
39355 The remote stub understands the @samp{qXfer:features:read} packet
39356 (@pxref{qXfer target description read}).
39358 @item qXfer:libraries:read
39359 The remote stub understands the @samp{qXfer:libraries:read} packet
39360 (@pxref{qXfer library list read}).
39362 @item qXfer:libraries-svr4:read
39363 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39364 (@pxref{qXfer svr4 library list read}).
39366 @item augmented-libraries-svr4-read
39367 The remote stub understands the augmented form of the
39368 @samp{qXfer:libraries-svr4:read} packet
39369 (@pxref{qXfer svr4 library list read}).
39371 @item qXfer:memory-map:read
39372 The remote stub understands the @samp{qXfer:memory-map:read} packet
39373 (@pxref{qXfer memory map read}).
39375 @item qXfer:sdata:read
39376 The remote stub understands the @samp{qXfer:sdata:read} packet
39377 (@pxref{qXfer sdata read}).
39379 @item qXfer:spu:read
39380 The remote stub understands the @samp{qXfer:spu:read} packet
39381 (@pxref{qXfer spu read}).
39383 @item qXfer:spu:write
39384 The remote stub understands the @samp{qXfer:spu:write} packet
39385 (@pxref{qXfer spu write}).
39387 @item qXfer:siginfo:read
39388 The remote stub understands the @samp{qXfer:siginfo:read} packet
39389 (@pxref{qXfer siginfo read}).
39391 @item qXfer:siginfo:write
39392 The remote stub understands the @samp{qXfer:siginfo:write} packet
39393 (@pxref{qXfer siginfo write}).
39395 @item qXfer:threads:read
39396 The remote stub understands the @samp{qXfer:threads:read} packet
39397 (@pxref{qXfer threads read}).
39399 @item qXfer:traceframe-info:read
39400 The remote stub understands the @samp{qXfer:traceframe-info:read}
39401 packet (@pxref{qXfer traceframe info read}).
39403 @item qXfer:uib:read
39404 The remote stub understands the @samp{qXfer:uib:read}
39405 packet (@pxref{qXfer unwind info block}).
39407 @item qXfer:fdpic:read
39408 The remote stub understands the @samp{qXfer:fdpic:read}
39409 packet (@pxref{qXfer fdpic loadmap read}).
39412 The remote stub understands the @samp{QNonStop} packet
39413 (@pxref{QNonStop}).
39415 @item QCatchSyscalls
39416 The remote stub understands the @samp{QCatchSyscalls} packet
39417 (@pxref{QCatchSyscalls}).
39420 The remote stub understands the @samp{QPassSignals} packet
39421 (@pxref{QPassSignals}).
39423 @item QStartNoAckMode
39424 The remote stub understands the @samp{QStartNoAckMode} packet and
39425 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39428 @anchor{multiprocess extensions}
39429 @cindex multiprocess extensions, in remote protocol
39430 The remote stub understands the multiprocess extensions to the remote
39431 protocol syntax. The multiprocess extensions affect the syntax of
39432 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39433 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39434 replies. Note that reporting this feature indicates support for the
39435 syntactic extensions only, not that the stub necessarily supports
39436 debugging of more than one process at a time. The stub must not use
39437 multiprocess extensions in packet replies unless @value{GDBN} has also
39438 indicated it supports them in its @samp{qSupported} request.
39440 @item qXfer:osdata:read
39441 The remote stub understands the @samp{qXfer:osdata:read} packet
39442 ((@pxref{qXfer osdata read}).
39444 @item ConditionalBreakpoints
39445 The target accepts and implements evaluation of conditional expressions
39446 defined for breakpoints. The target will only report breakpoint triggers
39447 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39449 @item ConditionalTracepoints
39450 The remote stub accepts and implements conditional expressions defined
39451 for tracepoints (@pxref{Tracepoint Conditions}).
39453 @item ReverseContinue
39454 The remote stub accepts and implements the reverse continue packet
39458 The remote stub accepts and implements the reverse step packet
39461 @item TracepointSource
39462 The remote stub understands the @samp{QTDPsrc} packet that supplies
39463 the source form of tracepoint definitions.
39466 The remote stub understands the @samp{QAgent} packet.
39469 The remote stub understands the @samp{QAllow} packet.
39471 @item QDisableRandomization
39472 The remote stub understands the @samp{QDisableRandomization} packet.
39474 @item StaticTracepoint
39475 @cindex static tracepoints, in remote protocol
39476 The remote stub supports static tracepoints.
39478 @item InstallInTrace
39479 @anchor{install tracepoint in tracing}
39480 The remote stub supports installing tracepoint in tracing.
39482 @item EnableDisableTracepoints
39483 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39484 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39485 to be enabled and disabled while a trace experiment is running.
39487 @item QTBuffer:size
39488 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39489 packet that allows to change the size of the trace buffer.
39492 @cindex string tracing, in remote protocol
39493 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39494 See @ref{Bytecode Descriptions} for details about the bytecode.
39496 @item BreakpointCommands
39497 @cindex breakpoint commands, in remote protocol
39498 The remote stub supports running a breakpoint's command list itself,
39499 rather than reporting the hit to @value{GDBN}.
39502 The remote stub understands the @samp{Qbtrace:off} packet.
39505 The remote stub understands the @samp{Qbtrace:bts} packet.
39508 The remote stub understands the @samp{Qbtrace:pt} packet.
39510 @item Qbtrace-conf:bts:size
39511 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
39513 @item Qbtrace-conf:pt:size
39514 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
39517 The remote stub reports the @samp{swbreak} stop reason for memory
39521 The remote stub reports the @samp{hwbreak} stop reason for hardware
39525 The remote stub reports the @samp{fork} stop reason for fork events.
39528 The remote stub reports the @samp{vfork} stop reason for vfork events
39529 and vforkdone events.
39532 The remote stub reports the @samp{exec} stop reason for exec events.
39534 @item vContSupported
39535 The remote stub reports the supported actions in the reply to
39536 @samp{vCont?} packet.
39538 @item QThreadEvents
39539 The remote stub understands the @samp{QThreadEvents} packet.
39542 The remote stub reports the @samp{N} stop reply.
39547 @cindex symbol lookup, remote request
39548 @cindex @samp{qSymbol} packet
39549 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39550 requests. Accept requests from the target for the values of symbols.
39555 The target does not need to look up any (more) symbols.
39556 @item qSymbol:@var{sym_name}
39557 The target requests the value of symbol @var{sym_name} (hex encoded).
39558 @value{GDBN} may provide the value by using the
39559 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39563 @item qSymbol:@var{sym_value}:@var{sym_name}
39564 Set the value of @var{sym_name} to @var{sym_value}.
39566 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39567 target has previously requested.
39569 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39570 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39576 The target does not need to look up any (more) symbols.
39577 @item qSymbol:@var{sym_name}
39578 The target requests the value of a new symbol @var{sym_name} (hex
39579 encoded). @value{GDBN} will continue to supply the values of symbols
39580 (if available), until the target ceases to request them.
39585 @itemx QTDisconnected
39592 @itemx qTMinFTPILen
39594 @xref{Tracepoint Packets}.
39596 @item qThreadExtraInfo,@var{thread-id}
39597 @cindex thread attributes info, remote request
39598 @cindex @samp{qThreadExtraInfo} packet
39599 Obtain from the target OS a printable string description of thread
39600 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
39601 for the forms of @var{thread-id}. This
39602 string may contain anything that the target OS thinks is interesting
39603 for @value{GDBN} to tell the user about the thread. The string is
39604 displayed in @value{GDBN}'s @code{info threads} display. Some
39605 examples of possible thread extra info strings are @samp{Runnable}, or
39606 @samp{Blocked on Mutex}.
39610 @item @var{XX}@dots{}
39611 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39612 comprising the printable string containing the extra information about
39613 the thread's attributes.
39616 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39617 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39618 conventions above. Please don't use this packet as a model for new
39637 @xref{Tracepoint Packets}.
39639 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39640 @cindex read special object, remote request
39641 @cindex @samp{qXfer} packet
39642 @anchor{qXfer read}
39643 Read uninterpreted bytes from the target's special data area
39644 identified by the keyword @var{object}. Request @var{length} bytes
39645 starting at @var{offset} bytes into the data. The content and
39646 encoding of @var{annex} is specific to @var{object}; it can supply
39647 additional details about what data to access.
39652 Data @var{data} (@pxref{Binary Data}) has been read from the
39653 target. There may be more data at a higher address (although
39654 it is permitted to return @samp{m} even for the last valid
39655 block of data, as long as at least one byte of data was read).
39656 It is possible for @var{data} to have fewer bytes than the @var{length} in the
39660 Data @var{data} (@pxref{Binary Data}) has been read from the target.
39661 There is no more data to be read. It is possible for @var{data} to
39662 have fewer bytes than the @var{length} in the request.
39665 The @var{offset} in the request is at the end of the data.
39666 There is no more data to be read.
39669 The request was malformed, or @var{annex} was invalid.
39672 The offset was invalid, or there was an error encountered reading the data.
39673 The @var{nn} part is a hex-encoded @code{errno} value.
39676 An empty reply indicates the @var{object} string was not recognized by
39677 the stub, or that the object does not support reading.
39680 Here are the specific requests of this form defined so far. All the
39681 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39682 formats, listed above.
39685 @item qXfer:auxv:read::@var{offset},@var{length}
39686 @anchor{qXfer auxiliary vector read}
39687 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39688 auxiliary vector}. Note @var{annex} must be empty.
39690 This packet is not probed by default; the remote stub must request it,
39691 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39693 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39694 @anchor{qXfer btrace read}
39696 Return a description of the current branch trace.
39697 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39698 packet may have one of the following values:
39702 Returns all available branch trace.
39705 Returns all available branch trace if the branch trace changed since
39706 the last read request.
39709 Returns the new branch trace since the last read request. Adds a new
39710 block to the end of the trace that begins at zero and ends at the source
39711 location of the first branch in the trace buffer. This extra block is
39712 used to stitch traces together.
39714 If the trace buffer overflowed, returns an error indicating the overflow.
39717 This packet is not probed by default; the remote stub must request it
39718 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39720 @item qXfer:btrace-conf:read::@var{offset},@var{length}
39721 @anchor{qXfer btrace-conf read}
39723 Return a description of the current branch trace configuration.
39724 @xref{Branch Trace Configuration Format}.
39726 This packet is not probed by default; the remote stub must request it
39727 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39729 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
39730 @anchor{qXfer executable filename read}
39731 Return the full absolute name of the file that was executed to create
39732 a process running on the remote system. The annex specifies the
39733 numeric process ID of the process to query, encoded as a hexadecimal
39734 number. If the annex part is empty the remote stub should return the
39735 filename corresponding to the currently executing process.
39737 This packet is not probed by default; the remote stub must request it,
39738 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39740 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39741 @anchor{qXfer target description read}
39742 Access the @dfn{target description}. @xref{Target Descriptions}. The
39743 annex specifies which XML document to access. The main description is
39744 always loaded from the @samp{target.xml} annex.
39746 This packet is not probed by default; the remote stub must request it,
39747 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39749 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39750 @anchor{qXfer library list read}
39751 Access the target's list of loaded libraries. @xref{Library List Format}.
39752 The annex part of the generic @samp{qXfer} packet must be empty
39753 (@pxref{qXfer read}).
39755 Targets which maintain a list of libraries in the program's memory do
39756 not need to implement this packet; it is designed for platforms where
39757 the operating system manages the list of loaded libraries.
39759 This packet is not probed by default; the remote stub must request it,
39760 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39762 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39763 @anchor{qXfer svr4 library list read}
39764 Access the target's list of loaded libraries when the target is an SVR4
39765 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39766 of the generic @samp{qXfer} packet must be empty unless the remote
39767 stub indicated it supports the augmented form of this packet
39768 by supplying an appropriate @samp{qSupported} response
39769 (@pxref{qXfer read}, @ref{qSupported}).
39771 This packet is optional for better performance on SVR4 targets.
39772 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39774 This packet is not probed by default; the remote stub must request it,
39775 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39777 If the remote stub indicates it supports the augmented form of this
39778 packet then the annex part of the generic @samp{qXfer} packet may
39779 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39780 arguments. The currently supported arguments are:
39783 @item start=@var{address}
39784 A hexadecimal number specifying the address of the @samp{struct
39785 link_map} to start reading the library list from. If unset or zero
39786 then the first @samp{struct link_map} in the library list will be
39787 chosen as the starting point.
39789 @item prev=@var{address}
39790 A hexadecimal number specifying the address of the @samp{struct
39791 link_map} immediately preceding the @samp{struct link_map}
39792 specified by the @samp{start} argument. If unset or zero then
39793 the remote stub will expect that no @samp{struct link_map}
39794 exists prior to the starting point.
39798 Arguments that are not understood by the remote stub will be silently
39801 @item qXfer:memory-map:read::@var{offset},@var{length}
39802 @anchor{qXfer memory map read}
39803 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39804 annex part of the generic @samp{qXfer} packet must be empty
39805 (@pxref{qXfer read}).
39807 This packet is not probed by default; the remote stub must request it,
39808 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39810 @item qXfer:sdata:read::@var{offset},@var{length}
39811 @anchor{qXfer sdata read}
39813 Read contents of the extra collected static tracepoint marker
39814 information. The annex part of the generic @samp{qXfer} packet must
39815 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39818 This packet is not probed by default; the remote stub must request it,
39819 by supplying an appropriate @samp{qSupported} response
39820 (@pxref{qSupported}).
39822 @item qXfer:siginfo:read::@var{offset},@var{length}
39823 @anchor{qXfer siginfo read}
39824 Read contents of the extra signal information on the target
39825 system. The annex part of the generic @samp{qXfer} packet must be
39826 empty (@pxref{qXfer read}).
39828 This packet is not probed by default; the remote stub must request it,
39829 by supplying an appropriate @samp{qSupported} response
39830 (@pxref{qSupported}).
39832 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39833 @anchor{qXfer spu read}
39834 Read contents of an @code{spufs} file on the target system. The
39835 annex specifies which file to read; it must be of the form
39836 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39837 in the target process, and @var{name} identifes the @code{spufs} file
39838 in that context to be accessed.
39840 This packet is not probed by default; the remote stub must request it,
39841 by supplying an appropriate @samp{qSupported} response
39842 (@pxref{qSupported}).
39844 @item qXfer:threads:read::@var{offset},@var{length}
39845 @anchor{qXfer threads read}
39846 Access the list of threads on target. @xref{Thread List Format}. The
39847 annex part of the generic @samp{qXfer} packet must be empty
39848 (@pxref{qXfer read}).
39850 This packet is not probed by default; the remote stub must request it,
39851 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39853 @item qXfer:traceframe-info:read::@var{offset},@var{length}
39854 @anchor{qXfer traceframe info read}
39856 Return a description of the current traceframe's contents.
39857 @xref{Traceframe Info Format}. The annex part of the generic
39858 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
39860 This packet is not probed by default; the remote stub must request it,
39861 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39863 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
39864 @anchor{qXfer unwind info block}
39866 Return the unwind information block for @var{pc}. This packet is used
39867 on OpenVMS/ia64 to ask the kernel unwind information.
39869 This packet is not probed by default.
39871 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
39872 @anchor{qXfer fdpic loadmap read}
39873 Read contents of @code{loadmap}s on the target system. The
39874 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
39875 executable @code{loadmap} or interpreter @code{loadmap} to read.
39877 This packet is not probed by default; the remote stub must request it,
39878 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39880 @item qXfer:osdata:read::@var{offset},@var{length}
39881 @anchor{qXfer osdata read}
39882 Access the target's @dfn{operating system information}.
39883 @xref{Operating System Information}.
39887 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
39888 @cindex write data into object, remote request
39889 @anchor{qXfer write}
39890 Write uninterpreted bytes into the target's special data area
39891 identified by the keyword @var{object}, starting at @var{offset} bytes
39892 into the data. The binary-encoded data (@pxref{Binary Data}) to be
39893 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
39894 is specific to @var{object}; it can supply additional details about what data
39900 @var{nn} (hex encoded) is the number of bytes written.
39901 This may be fewer bytes than supplied in the request.
39904 The request was malformed, or @var{annex} was invalid.
39907 The offset was invalid, or there was an error encountered writing the data.
39908 The @var{nn} part is a hex-encoded @code{errno} value.
39911 An empty reply indicates the @var{object} string was not
39912 recognized by the stub, or that the object does not support writing.
39915 Here are the specific requests of this form defined so far. All the
39916 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
39917 formats, listed above.
39920 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
39921 @anchor{qXfer siginfo write}
39922 Write @var{data} to the extra signal information on the target system.
39923 The annex part of the generic @samp{qXfer} packet must be
39924 empty (@pxref{qXfer write}).
39926 This packet is not probed by default; the remote stub must request it,
39927 by supplying an appropriate @samp{qSupported} response
39928 (@pxref{qSupported}).
39930 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
39931 @anchor{qXfer spu write}
39932 Write @var{data} to an @code{spufs} file on the target system. The
39933 annex specifies which file to write; it must be of the form
39934 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39935 in the target process, and @var{name} identifes the @code{spufs} file
39936 in that context to be accessed.
39938 This packet is not probed by default; the remote stub must request it,
39939 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39942 @item qXfer:@var{object}:@var{operation}:@dots{}
39943 Requests of this form may be added in the future. When a stub does
39944 not recognize the @var{object} keyword, or its support for
39945 @var{object} does not recognize the @var{operation} keyword, the stub
39946 must respond with an empty packet.
39948 @item qAttached:@var{pid}
39949 @cindex query attached, remote request
39950 @cindex @samp{qAttached} packet
39951 Return an indication of whether the remote server attached to an
39952 existing process or created a new process. When the multiprocess
39953 protocol extensions are supported (@pxref{multiprocess extensions}),
39954 @var{pid} is an integer in hexadecimal format identifying the target
39955 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
39956 the query packet will be simplified as @samp{qAttached}.
39958 This query is used, for example, to know whether the remote process
39959 should be detached or killed when a @value{GDBN} session is ended with
39960 the @code{quit} command.
39965 The remote server attached to an existing process.
39967 The remote server created a new process.
39969 A badly formed request or an error was encountered.
39973 Enable branch tracing for the current thread using Branch Trace Store.
39978 Branch tracing has been enabled.
39980 A badly formed request or an error was encountered.
39984 Enable branch tracing for the current thread using Intel Processor Trace.
39989 Branch tracing has been enabled.
39991 A badly formed request or an error was encountered.
39995 Disable branch tracing for the current thread.
40000 Branch tracing has been disabled.
40002 A badly formed request or an error was encountered.
40005 @item Qbtrace-conf:bts:size=@var{value}
40006 Set the requested ring buffer size for new threads that use the
40007 btrace recording method in bts format.
40012 The ring buffer size has been set.
40014 A badly formed request or an error was encountered.
40017 @item Qbtrace-conf:pt:size=@var{value}
40018 Set the requested ring buffer size for new threads that use the
40019 btrace recording method in pt format.
40024 The ring buffer size has been set.
40026 A badly formed request or an error was encountered.
40031 @node Architecture-Specific Protocol Details
40032 @section Architecture-Specific Protocol Details
40034 This section describes how the remote protocol is applied to specific
40035 target architectures. Also see @ref{Standard Target Features}, for
40036 details of XML target descriptions for each architecture.
40039 * ARM-Specific Protocol Details::
40040 * MIPS-Specific Protocol Details::
40043 @node ARM-Specific Protocol Details
40044 @subsection @acronym{ARM}-specific Protocol Details
40047 * ARM Breakpoint Kinds::
40050 @node ARM Breakpoint Kinds
40051 @subsubsection @acronym{ARM} Breakpoint Kinds
40052 @cindex breakpoint kinds, @acronym{ARM}
40054 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40059 16-bit Thumb mode breakpoint.
40062 32-bit Thumb mode (Thumb-2) breakpoint.
40065 32-bit @acronym{ARM} mode breakpoint.
40069 @node MIPS-Specific Protocol Details
40070 @subsection @acronym{MIPS}-specific Protocol Details
40073 * MIPS Register packet Format::
40074 * MIPS Breakpoint Kinds::
40077 @node MIPS Register packet Format
40078 @subsubsection @acronym{MIPS} Register Packet Format
40079 @cindex register packet format, @acronym{MIPS}
40081 The following @code{g}/@code{G} packets have previously been defined.
40082 In the below, some thirty-two bit registers are transferred as
40083 sixty-four bits. Those registers should be zero/sign extended (which?)
40084 to fill the space allocated. Register bytes are transferred in target
40085 byte order. The two nibbles within a register byte are transferred
40086 most-significant -- least-significant.
40091 All registers are transferred as thirty-two bit quantities in the order:
40092 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
40093 registers; fsr; fir; fp.
40096 All registers are transferred as sixty-four bit quantities (including
40097 thirty-two bit registers such as @code{sr}). The ordering is the same
40102 @node MIPS Breakpoint Kinds
40103 @subsubsection @acronym{MIPS} Breakpoint Kinds
40104 @cindex breakpoint kinds, @acronym{MIPS}
40106 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40111 16-bit @acronym{MIPS16} mode breakpoint.
40114 16-bit @acronym{microMIPS} mode breakpoint.
40117 32-bit standard @acronym{MIPS} mode breakpoint.
40120 32-bit @acronym{microMIPS} mode breakpoint.
40124 @node Tracepoint Packets
40125 @section Tracepoint Packets
40126 @cindex tracepoint packets
40127 @cindex packets, tracepoint
40129 Here we describe the packets @value{GDBN} uses to implement
40130 tracepoints (@pxref{Tracepoints}).
40134 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
40135 @cindex @samp{QTDP} packet
40136 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
40137 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
40138 the tracepoint is disabled. The @var{step} gives the tracepoint's step
40139 count, and @var{pass} gives its pass count. If an @samp{F} is present,
40140 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
40141 the number of bytes that the target should copy elsewhere to make room
40142 for the tracepoint. If an @samp{X} is present, it introduces a
40143 tracepoint condition, which consists of a hexadecimal length, followed
40144 by a comma and hex-encoded bytes, in a manner similar to action
40145 encodings as described below. If the trailing @samp{-} is present,
40146 further @samp{QTDP} packets will follow to specify this tracepoint's
40152 The packet was understood and carried out.
40154 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40156 The packet was not recognized.
40159 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
40160 Define actions to be taken when a tracepoint is hit. The @var{n} and
40161 @var{addr} must be the same as in the initial @samp{QTDP} packet for
40162 this tracepoint. This packet may only be sent immediately after
40163 another @samp{QTDP} packet that ended with a @samp{-}. If the
40164 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
40165 specifying more actions for this tracepoint.
40167 In the series of action packets for a given tracepoint, at most one
40168 can have an @samp{S} before its first @var{action}. If such a packet
40169 is sent, it and the following packets define ``while-stepping''
40170 actions. Any prior packets define ordinary actions --- that is, those
40171 taken when the tracepoint is first hit. If no action packet has an
40172 @samp{S}, then all the packets in the series specify ordinary
40173 tracepoint actions.
40175 The @samp{@var{action}@dots{}} portion of the packet is a series of
40176 actions, concatenated without separators. Each action has one of the
40182 Collect the registers whose bits are set in @var{mask},
40183 a hexadecimal number whose @var{i}'th bit is set if register number
40184 @var{i} should be collected. (The least significant bit is numbered
40185 zero.) Note that @var{mask} may be any number of digits long; it may
40186 not fit in a 32-bit word.
40188 @item M @var{basereg},@var{offset},@var{len}
40189 Collect @var{len} bytes of memory starting at the address in register
40190 number @var{basereg}, plus @var{offset}. If @var{basereg} is
40191 @samp{-1}, then the range has a fixed address: @var{offset} is the
40192 address of the lowest byte to collect. The @var{basereg},
40193 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
40194 values (the @samp{-1} value for @var{basereg} is a special case).
40196 @item X @var{len},@var{expr}
40197 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
40198 it directs. The agent expression @var{expr} is as described in
40199 @ref{Agent Expressions}. Each byte of the expression is encoded as a
40200 two-digit hex number in the packet; @var{len} is the number of bytes
40201 in the expression (and thus one-half the number of hex digits in the
40206 Any number of actions may be packed together in a single @samp{QTDP}
40207 packet, as long as the packet does not exceed the maximum packet
40208 length (400 bytes, for many stubs). There may be only one @samp{R}
40209 action per tracepoint, and it must precede any @samp{M} or @samp{X}
40210 actions. Any registers referred to by @samp{M} and @samp{X} actions
40211 must be collected by a preceding @samp{R} action. (The
40212 ``while-stepping'' actions are treated as if they were attached to a
40213 separate tracepoint, as far as these restrictions are concerned.)
40218 The packet was understood and carried out.
40220 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40222 The packet was not recognized.
40225 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
40226 @cindex @samp{QTDPsrc} packet
40227 Specify a source string of tracepoint @var{n} at address @var{addr}.
40228 This is useful to get accurate reproduction of the tracepoints
40229 originally downloaded at the beginning of the trace run. The @var{type}
40230 is the name of the tracepoint part, such as @samp{cond} for the
40231 tracepoint's conditional expression (see below for a list of types), while
40232 @var{bytes} is the string, encoded in hexadecimal.
40234 @var{start} is the offset of the @var{bytes} within the overall source
40235 string, while @var{slen} is the total length of the source string.
40236 This is intended for handling source strings that are longer than will
40237 fit in a single packet.
40238 @c Add detailed example when this info is moved into a dedicated
40239 @c tracepoint descriptions section.
40241 The available string types are @samp{at} for the location,
40242 @samp{cond} for the conditional, and @samp{cmd} for an action command.
40243 @value{GDBN} sends a separate packet for each command in the action
40244 list, in the same order in which the commands are stored in the list.
40246 The target does not need to do anything with source strings except
40247 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
40250 Although this packet is optional, and @value{GDBN} will only send it
40251 if the target replies with @samp{TracepointSource} @xref{General
40252 Query Packets}, it makes both disconnected tracing and trace files
40253 much easier to use. Otherwise the user must be careful that the
40254 tracepoints in effect while looking at trace frames are identical to
40255 the ones in effect during the trace run; even a small discrepancy
40256 could cause @samp{tdump} not to work, or a particular trace frame not
40259 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
40260 @cindex define trace state variable, remote request
40261 @cindex @samp{QTDV} packet
40262 Create a new trace state variable, number @var{n}, with an initial
40263 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
40264 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
40265 the option of not using this packet for initial values of zero; the
40266 target should simply create the trace state variables as they are
40267 mentioned in expressions. The value @var{builtin} should be 1 (one)
40268 if the trace state variable is builtin and 0 (zero) if it is not builtin.
40269 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
40270 @samp{qTsV} packet had it set. The contents of @var{name} is the
40271 hex-encoded name (without the leading @samp{$}) of the trace state
40274 @item QTFrame:@var{n}
40275 @cindex @samp{QTFrame} packet
40276 Select the @var{n}'th tracepoint frame from the buffer, and use the
40277 register and memory contents recorded there to answer subsequent
40278 request packets from @value{GDBN}.
40280 A successful reply from the stub indicates that the stub has found the
40281 requested frame. The response is a series of parts, concatenated
40282 without separators, describing the frame we selected. Each part has
40283 one of the following forms:
40287 The selected frame is number @var{n} in the trace frame buffer;
40288 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40289 was no frame matching the criteria in the request packet.
40292 The selected trace frame records a hit of tracepoint number @var{t};
40293 @var{t} is a hexadecimal number.
40297 @item QTFrame:pc:@var{addr}
40298 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40299 currently selected frame whose PC is @var{addr};
40300 @var{addr} is a hexadecimal number.
40302 @item QTFrame:tdp:@var{t}
40303 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40304 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40305 is a hexadecimal number.
40307 @item QTFrame:range:@var{start}:@var{end}
40308 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40309 currently selected frame whose PC is between @var{start} (inclusive)
40310 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40313 @item QTFrame:outside:@var{start}:@var{end}
40314 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40315 frame @emph{outside} the given range of addresses (exclusive).
40318 @cindex @samp{qTMinFTPILen} packet
40319 This packet requests the minimum length of instruction at which a fast
40320 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40321 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40322 it depends on the target system being able to create trampolines in
40323 the first 64K of memory, which might or might not be possible for that
40324 system. So the reply to this packet will be 4 if it is able to
40331 The minimum instruction length is currently unknown.
40333 The minimum instruction length is @var{length}, where @var{length}
40334 is a hexadecimal number greater or equal to 1. A reply
40335 of 1 means that a fast tracepoint may be placed on any instruction
40336 regardless of size.
40338 An error has occurred.
40340 An empty reply indicates that the request is not supported by the stub.
40344 @cindex @samp{QTStart} packet
40345 Begin the tracepoint experiment. Begin collecting data from
40346 tracepoint hits in the trace frame buffer. This packet supports the
40347 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40348 instruction reply packet}).
40351 @cindex @samp{QTStop} packet
40352 End the tracepoint experiment. Stop collecting trace frames.
40354 @item QTEnable:@var{n}:@var{addr}
40356 @cindex @samp{QTEnable} packet
40357 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40358 experiment. If the tracepoint was previously disabled, then collection
40359 of data from it will resume.
40361 @item QTDisable:@var{n}:@var{addr}
40363 @cindex @samp{QTDisable} packet
40364 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40365 experiment. No more data will be collected from the tracepoint unless
40366 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40369 @cindex @samp{QTinit} packet
40370 Clear the table of tracepoints, and empty the trace frame buffer.
40372 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40373 @cindex @samp{QTro} packet
40374 Establish the given ranges of memory as ``transparent''. The stub
40375 will answer requests for these ranges from memory's current contents,
40376 if they were not collected as part of the tracepoint hit.
40378 @value{GDBN} uses this to mark read-only regions of memory, like those
40379 containing program code. Since these areas never change, they should
40380 still have the same contents they did when the tracepoint was hit, so
40381 there's no reason for the stub to refuse to provide their contents.
40383 @item QTDisconnected:@var{value}
40384 @cindex @samp{QTDisconnected} packet
40385 Set the choice to what to do with the tracing run when @value{GDBN}
40386 disconnects from the target. A @var{value} of 1 directs the target to
40387 continue the tracing run, while 0 tells the target to stop tracing if
40388 @value{GDBN} is no longer in the picture.
40391 @cindex @samp{qTStatus} packet
40392 Ask the stub if there is a trace experiment running right now.
40394 The reply has the form:
40398 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40399 @var{running} is a single digit @code{1} if the trace is presently
40400 running, or @code{0} if not. It is followed by semicolon-separated
40401 optional fields that an agent may use to report additional status.
40405 If the trace is not running, the agent may report any of several
40406 explanations as one of the optional fields:
40411 No trace has been run yet.
40413 @item tstop[:@var{text}]:0
40414 The trace was stopped by a user-originated stop command. The optional
40415 @var{text} field is a user-supplied string supplied as part of the
40416 stop command (for instance, an explanation of why the trace was
40417 stopped manually). It is hex-encoded.
40420 The trace stopped because the trace buffer filled up.
40422 @item tdisconnected:0
40423 The trace stopped because @value{GDBN} disconnected from the target.
40425 @item tpasscount:@var{tpnum}
40426 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40428 @item terror:@var{text}:@var{tpnum}
40429 The trace stopped because tracepoint @var{tpnum} had an error. The
40430 string @var{text} is available to describe the nature of the error
40431 (for instance, a divide by zero in the condition expression); it
40435 The trace stopped for some other reason.
40439 Additional optional fields supply statistical and other information.
40440 Although not required, they are extremely useful for users monitoring
40441 the progress of a trace run. If a trace has stopped, and these
40442 numbers are reported, they must reflect the state of the just-stopped
40447 @item tframes:@var{n}
40448 The number of trace frames in the buffer.
40450 @item tcreated:@var{n}
40451 The total number of trace frames created during the run. This may
40452 be larger than the trace frame count, if the buffer is circular.
40454 @item tsize:@var{n}
40455 The total size of the trace buffer, in bytes.
40457 @item tfree:@var{n}
40458 The number of bytes still unused in the buffer.
40460 @item circular:@var{n}
40461 The value of the circular trace buffer flag. @code{1} means that the
40462 trace buffer is circular and old trace frames will be discarded if
40463 necessary to make room, @code{0} means that the trace buffer is linear
40466 @item disconn:@var{n}
40467 The value of the disconnected tracing flag. @code{1} means that
40468 tracing will continue after @value{GDBN} disconnects, @code{0} means
40469 that the trace run will stop.
40473 @item qTP:@var{tp}:@var{addr}
40474 @cindex tracepoint status, remote request
40475 @cindex @samp{qTP} packet
40476 Ask the stub for the current state of tracepoint number @var{tp} at
40477 address @var{addr}.
40481 @item V@var{hits}:@var{usage}
40482 The tracepoint has been hit @var{hits} times so far during the trace
40483 run, and accounts for @var{usage} in the trace buffer. Note that
40484 @code{while-stepping} steps are not counted as separate hits, but the
40485 steps' space consumption is added into the usage number.
40489 @item qTV:@var{var}
40490 @cindex trace state variable value, remote request
40491 @cindex @samp{qTV} packet
40492 Ask the stub for the value of the trace state variable number @var{var}.
40497 The value of the variable is @var{value}. This will be the current
40498 value of the variable if the user is examining a running target, or a
40499 saved value if the variable was collected in the trace frame that the
40500 user is looking at. Note that multiple requests may result in
40501 different reply values, such as when requesting values while the
40502 program is running.
40505 The value of the variable is unknown. This would occur, for example,
40506 if the user is examining a trace frame in which the requested variable
40511 @cindex @samp{qTfP} packet
40513 @cindex @samp{qTsP} packet
40514 These packets request data about tracepoints that are being used by
40515 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40516 of data, and multiple @code{qTsP} to get additional pieces. Replies
40517 to these packets generally take the form of the @code{QTDP} packets
40518 that define tracepoints. (FIXME add detailed syntax)
40521 @cindex @samp{qTfV} packet
40523 @cindex @samp{qTsV} packet
40524 These packets request data about trace state variables that are on the
40525 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40526 and multiple @code{qTsV} to get additional variables. Replies to
40527 these packets follow the syntax of the @code{QTDV} packets that define
40528 trace state variables.
40534 @cindex @samp{qTfSTM} packet
40535 @cindex @samp{qTsSTM} packet
40536 These packets request data about static tracepoint markers that exist
40537 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40538 first piece of data, and multiple @code{qTsSTM} to get additional
40539 pieces. Replies to these packets take the following form:
40543 @item m @var{address}:@var{id}:@var{extra}
40545 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40546 a comma-separated list of markers
40548 (lower case letter @samp{L}) denotes end of list.
40550 An error occurred. The error number @var{nn} is given as hex digits.
40552 An empty reply indicates that the request is not supported by the
40556 The @var{address} is encoded in hex;
40557 @var{id} and @var{extra} are strings encoded in hex.
40559 In response to each query, the target will reply with a list of one or
40560 more markers, separated by commas. @value{GDBN} will respond to each
40561 reply with a request for more markers (using the @samp{qs} form of the
40562 query), until the target responds with @samp{l} (lower-case ell, for
40565 @item qTSTMat:@var{address}
40567 @cindex @samp{qTSTMat} packet
40568 This packets requests data about static tracepoint markers in the
40569 target program at @var{address}. Replies to this packet follow the
40570 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40571 tracepoint markers.
40573 @item QTSave:@var{filename}
40574 @cindex @samp{QTSave} packet
40575 This packet directs the target to save trace data to the file name
40576 @var{filename} in the target's filesystem. The @var{filename} is encoded
40577 as a hex string; the interpretation of the file name (relative vs
40578 absolute, wild cards, etc) is up to the target.
40580 @item qTBuffer:@var{offset},@var{len}
40581 @cindex @samp{qTBuffer} packet
40582 Return up to @var{len} bytes of the current contents of trace buffer,
40583 starting at @var{offset}. The trace buffer is treated as if it were
40584 a contiguous collection of traceframes, as per the trace file format.
40585 The reply consists as many hex-encoded bytes as the target can deliver
40586 in a packet; it is not an error to return fewer than were asked for.
40587 A reply consisting of just @code{l} indicates that no bytes are
40590 @item QTBuffer:circular:@var{value}
40591 This packet directs the target to use a circular trace buffer if
40592 @var{value} is 1, or a linear buffer if the value is 0.
40594 @item QTBuffer:size:@var{size}
40595 @anchor{QTBuffer-size}
40596 @cindex @samp{QTBuffer size} packet
40597 This packet directs the target to make the trace buffer be of size
40598 @var{size} if possible. A value of @code{-1} tells the target to
40599 use whatever size it prefers.
40601 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40602 @cindex @samp{QTNotes} packet
40603 This packet adds optional textual notes to the trace run. Allowable
40604 types include @code{user}, @code{notes}, and @code{tstop}, the
40605 @var{text} fields are arbitrary strings, hex-encoded.
40609 @subsection Relocate instruction reply packet
40610 When installing fast tracepoints in memory, the target may need to
40611 relocate the instruction currently at the tracepoint address to a
40612 different address in memory. For most instructions, a simple copy is
40613 enough, but, for example, call instructions that implicitly push the
40614 return address on the stack, and relative branches or other
40615 PC-relative instructions require offset adjustment, so that the effect
40616 of executing the instruction at a different address is the same as if
40617 it had executed in the original location.
40619 In response to several of the tracepoint packets, the target may also
40620 respond with a number of intermediate @samp{qRelocInsn} request
40621 packets before the final result packet, to have @value{GDBN} handle
40622 this relocation operation. If a packet supports this mechanism, its
40623 documentation will explicitly say so. See for example the above
40624 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40625 format of the request is:
40628 @item qRelocInsn:@var{from};@var{to}
40630 This requests @value{GDBN} to copy instruction at address @var{from}
40631 to address @var{to}, possibly adjusted so that executing the
40632 instruction at @var{to} has the same effect as executing it at
40633 @var{from}. @value{GDBN} writes the adjusted instruction to target
40634 memory starting at @var{to}.
40639 @item qRelocInsn:@var{adjusted_size}
40640 Informs the stub the relocation is complete. The @var{adjusted_size} is
40641 the length in bytes of resulting relocated instruction sequence.
40643 A badly formed request was detected, or an error was encountered while
40644 relocating the instruction.
40647 @node Host I/O Packets
40648 @section Host I/O Packets
40649 @cindex Host I/O, remote protocol
40650 @cindex file transfer, remote protocol
40652 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40653 operations on the far side of a remote link. For example, Host I/O is
40654 used to upload and download files to a remote target with its own
40655 filesystem. Host I/O uses the same constant values and data structure
40656 layout as the target-initiated File-I/O protocol. However, the
40657 Host I/O packets are structured differently. The target-initiated
40658 protocol relies on target memory to store parameters and buffers.
40659 Host I/O requests are initiated by @value{GDBN}, and the
40660 target's memory is not involved. @xref{File-I/O Remote Protocol
40661 Extension}, for more details on the target-initiated protocol.
40663 The Host I/O request packets all encode a single operation along with
40664 its arguments. They have this format:
40668 @item vFile:@var{operation}: @var{parameter}@dots{}
40669 @var{operation} is the name of the particular request; the target
40670 should compare the entire packet name up to the second colon when checking
40671 for a supported operation. The format of @var{parameter} depends on
40672 the operation. Numbers are always passed in hexadecimal. Negative
40673 numbers have an explicit minus sign (i.e.@: two's complement is not
40674 used). Strings (e.g.@: filenames) are encoded as a series of
40675 hexadecimal bytes. The last argument to a system call may be a
40676 buffer of escaped binary data (@pxref{Binary Data}).
40680 The valid responses to Host I/O packets are:
40684 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40685 @var{result} is the integer value returned by this operation, usually
40686 non-negative for success and -1 for errors. If an error has occured,
40687 @var{errno} will be included in the result specifying a
40688 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40689 operations which return data, @var{attachment} supplies the data as a
40690 binary buffer. Binary buffers in response packets are escaped in the
40691 normal way (@pxref{Binary Data}). See the individual packet
40692 documentation for the interpretation of @var{result} and
40696 An empty response indicates that this operation is not recognized.
40700 These are the supported Host I/O operations:
40703 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
40704 Open a file at @var{filename} and return a file descriptor for it, or
40705 return -1 if an error occurs. The @var{filename} is a string,
40706 @var{flags} is an integer indicating a mask of open flags
40707 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40708 of mode bits to use if the file is created (@pxref{mode_t Values}).
40709 @xref{open}, for details of the open flags and mode values.
40711 @item vFile:close: @var{fd}
40712 Close the open file corresponding to @var{fd} and return 0, or
40713 -1 if an error occurs.
40715 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40716 Read data from the open file corresponding to @var{fd}. Up to
40717 @var{count} bytes will be read from the file, starting at @var{offset}
40718 relative to the start of the file. The target may read fewer bytes;
40719 common reasons include packet size limits and an end-of-file
40720 condition. The number of bytes read is returned. Zero should only be
40721 returned for a successful read at the end of the file, or if
40722 @var{count} was zero.
40724 The data read should be returned as a binary attachment on success.
40725 If zero bytes were read, the response should include an empty binary
40726 attachment (i.e.@: a trailing semicolon). The return value is the
40727 number of target bytes read; the binary attachment may be longer if
40728 some characters were escaped.
40730 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40731 Write @var{data} (a binary buffer) to the open file corresponding
40732 to @var{fd}. Start the write at @var{offset} from the start of the
40733 file. Unlike many @code{write} system calls, there is no
40734 separate @var{count} argument; the length of @var{data} in the
40735 packet is used. @samp{vFile:write} returns the number of bytes written,
40736 which may be shorter than the length of @var{data}, or -1 if an
40739 @item vFile:fstat: @var{fd}
40740 Get information about the open file corresponding to @var{fd}.
40741 On success the information is returned as a binary attachment
40742 and the return value is the size of this attachment in bytes.
40743 If an error occurs the return value is -1. The format of the
40744 returned binary attachment is as described in @ref{struct stat}.
40746 @item vFile:unlink: @var{filename}
40747 Delete the file at @var{filename} on the target. Return 0,
40748 or -1 if an error occurs. The @var{filename} is a string.
40750 @item vFile:readlink: @var{filename}
40751 Read value of symbolic link @var{filename} on the target. Return
40752 the number of bytes read, or -1 if an error occurs.
40754 The data read should be returned as a binary attachment on success.
40755 If zero bytes were read, the response should include an empty binary
40756 attachment (i.e.@: a trailing semicolon). The return value is the
40757 number of target bytes read; the binary attachment may be longer if
40758 some characters were escaped.
40760 @item vFile:setfs: @var{pid}
40761 Select the filesystem on which @code{vFile} operations with
40762 @var{filename} arguments will operate. This is required for
40763 @value{GDBN} to be able to access files on remote targets where
40764 the remote stub does not share a common filesystem with the
40767 If @var{pid} is nonzero, select the filesystem as seen by process
40768 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
40769 the remote stub. Return 0 on success, or -1 if an error occurs.
40770 If @code{vFile:setfs:} indicates success, the selected filesystem
40771 remains selected until the next successful @code{vFile:setfs:}
40777 @section Interrupts
40778 @cindex interrupts (remote protocol)
40779 @anchor{interrupting remote targets}
40781 In all-stop mode, when a program on the remote target is running,
40782 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
40783 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
40784 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40786 The precise meaning of @code{BREAK} is defined by the transport
40787 mechanism and may, in fact, be undefined. @value{GDBN} does not
40788 currently define a @code{BREAK} mechanism for any of the network
40789 interfaces except for TCP, in which case @value{GDBN} sends the
40790 @code{telnet} BREAK sequence.
40792 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40793 transport mechanisms. It is represented by sending the single byte
40794 @code{0x03} without any of the usual packet overhead described in
40795 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40796 transmitted as part of a packet, it is considered to be packet data
40797 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40798 (@pxref{X packet}), used for binary downloads, may include an unescaped
40799 @code{0x03} as part of its packet.
40801 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40802 When Linux kernel receives this sequence from serial port,
40803 it stops execution and connects to gdb.
40805 In non-stop mode, because packet resumptions are asynchronous
40806 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
40807 command to the remote stub, even when the target is running. For that
40808 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
40809 packet}) with the usual packet framing instead of the single byte
40812 Stubs are not required to recognize these interrupt mechanisms and the
40813 precise meaning associated with receipt of the interrupt is
40814 implementation defined. If the target supports debugging of multiple
40815 threads and/or processes, it should attempt to interrupt all
40816 currently-executing threads and processes.
40817 If the stub is successful at interrupting the
40818 running program, it should send one of the stop
40819 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40820 of successfully stopping the program in all-stop mode, and a stop reply
40821 for each stopped thread in non-stop mode.
40822 Interrupts received while the
40823 program is stopped are queued and the program will be interrupted when
40824 it is resumed next time.
40826 @node Notification Packets
40827 @section Notification Packets
40828 @cindex notification packets
40829 @cindex packets, notification
40831 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40832 packets that require no acknowledgment. Both the GDB and the stub
40833 may send notifications (although the only notifications defined at
40834 present are sent by the stub). Notifications carry information
40835 without incurring the round-trip latency of an acknowledgment, and so
40836 are useful for low-impact communications where occasional packet loss
40839 A notification packet has the form @samp{% @var{data} #
40840 @var{checksum}}, where @var{data} is the content of the notification,
40841 and @var{checksum} is a checksum of @var{data}, computed and formatted
40842 as for ordinary @value{GDBN} packets. A notification's @var{data}
40843 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40844 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40845 to acknowledge the notification's receipt or to report its corruption.
40847 Every notification's @var{data} begins with a name, which contains no
40848 colon characters, followed by a colon character.
40850 Recipients should silently ignore corrupted notifications and
40851 notifications they do not understand. Recipients should restart
40852 timeout periods on receipt of a well-formed notification, whether or
40853 not they understand it.
40855 Senders should only send the notifications described here when this
40856 protocol description specifies that they are permitted. In the
40857 future, we may extend the protocol to permit existing notifications in
40858 new contexts; this rule helps older senders avoid confusing newer
40861 (Older versions of @value{GDBN} ignore bytes received until they see
40862 the @samp{$} byte that begins an ordinary packet, so new stubs may
40863 transmit notifications without fear of confusing older clients. There
40864 are no notifications defined for @value{GDBN} to send at the moment, but we
40865 assume that most older stubs would ignore them, as well.)
40867 Each notification is comprised of three parts:
40869 @item @var{name}:@var{event}
40870 The notification packet is sent by the side that initiates the
40871 exchange (currently, only the stub does that), with @var{event}
40872 carrying the specific information about the notification, and
40873 @var{name} specifying the name of the notification.
40875 The acknowledge sent by the other side, usually @value{GDBN}, to
40876 acknowledge the exchange and request the event.
40879 The purpose of an asynchronous notification mechanism is to report to
40880 @value{GDBN} that something interesting happened in the remote stub.
40882 The remote stub may send notification @var{name}:@var{event}
40883 at any time, but @value{GDBN} acknowledges the notification when
40884 appropriate. The notification event is pending before @value{GDBN}
40885 acknowledges. Only one notification at a time may be pending; if
40886 additional events occur before @value{GDBN} has acknowledged the
40887 previous notification, they must be queued by the stub for later
40888 synchronous transmission in response to @var{ack} packets from
40889 @value{GDBN}. Because the notification mechanism is unreliable,
40890 the stub is permitted to resend a notification if it believes
40891 @value{GDBN} may not have received it.
40893 Specifically, notifications may appear when @value{GDBN} is not
40894 otherwise reading input from the stub, or when @value{GDBN} is
40895 expecting to read a normal synchronous response or a
40896 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
40897 Notification packets are distinct from any other communication from
40898 the stub so there is no ambiguity.
40900 After receiving a notification, @value{GDBN} shall acknowledge it by
40901 sending a @var{ack} packet as a regular, synchronous request to the
40902 stub. Such acknowledgment is not required to happen immediately, as
40903 @value{GDBN} is permitted to send other, unrelated packets to the
40904 stub first, which the stub should process normally.
40906 Upon receiving a @var{ack} packet, if the stub has other queued
40907 events to report to @value{GDBN}, it shall respond by sending a
40908 normal @var{event}. @value{GDBN} shall then send another @var{ack}
40909 packet to solicit further responses; again, it is permitted to send
40910 other, unrelated packets as well which the stub should process
40913 If the stub receives a @var{ack} packet and there are no additional
40914 @var{event} to report, the stub shall return an @samp{OK} response.
40915 At this point, @value{GDBN} has finished processing a notification
40916 and the stub has completed sending any queued events. @value{GDBN}
40917 won't accept any new notifications until the final @samp{OK} is
40918 received . If further notification events occur, the stub shall send
40919 a new notification, @value{GDBN} shall accept the notification, and
40920 the process shall be repeated.
40922 The process of asynchronous notification can be illustrated by the
40925 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
40928 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
40930 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
40935 The following notifications are defined:
40936 @multitable @columnfractions 0.12 0.12 0.38 0.38
40945 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
40946 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
40947 for information on how these notifications are acknowledged by
40949 @tab Report an asynchronous stop event in non-stop mode.
40953 @node Remote Non-Stop
40954 @section Remote Protocol Support for Non-Stop Mode
40956 @value{GDBN}'s remote protocol supports non-stop debugging of
40957 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
40958 supports non-stop mode, it should report that to @value{GDBN} by including
40959 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
40961 @value{GDBN} typically sends a @samp{QNonStop} packet only when
40962 establishing a new connection with the stub. Entering non-stop mode
40963 does not alter the state of any currently-running threads, but targets
40964 must stop all threads in any already-attached processes when entering
40965 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
40966 probe the target state after a mode change.
40968 In non-stop mode, when an attached process encounters an event that
40969 would otherwise be reported with a stop reply, it uses the
40970 asynchronous notification mechanism (@pxref{Notification Packets}) to
40971 inform @value{GDBN}. In contrast to all-stop mode, where all threads
40972 in all processes are stopped when a stop reply is sent, in non-stop
40973 mode only the thread reporting the stop event is stopped. That is,
40974 when reporting a @samp{S} or @samp{T} response to indicate completion
40975 of a step operation, hitting a breakpoint, or a fault, only the
40976 affected thread is stopped; any other still-running threads continue
40977 to run. When reporting a @samp{W} or @samp{X} response, all running
40978 threads belonging to other attached processes continue to run.
40980 In non-stop mode, the target shall respond to the @samp{?} packet as
40981 follows. First, any incomplete stop reply notification/@samp{vStopped}
40982 sequence in progress is abandoned. The target must begin a new
40983 sequence reporting stop events for all stopped threads, whether or not
40984 it has previously reported those events to @value{GDBN}. The first
40985 stop reply is sent as a synchronous reply to the @samp{?} packet, and
40986 subsequent stop replies are sent as responses to @samp{vStopped} packets
40987 using the mechanism described above. The target must not send
40988 asynchronous stop reply notifications until the sequence is complete.
40989 If all threads are running when the target receives the @samp{?} packet,
40990 or if the target is not attached to any process, it shall respond
40993 If the stub supports non-stop mode, it should also support the
40994 @samp{swbreak} stop reason if software breakpoints are supported, and
40995 the @samp{hwbreak} stop reason if hardware breakpoints are supported
40996 (@pxref{swbreak stop reason}). This is because given the asynchronous
40997 nature of non-stop mode, between the time a thread hits a breakpoint
40998 and the time the event is finally processed by @value{GDBN}, the
40999 breakpoint may have already been removed from the target. Due to
41000 this, @value{GDBN} needs to be able to tell whether a trap stop was
41001 caused by a delayed breakpoint event, which should be ignored, as
41002 opposed to a random trap signal, which should be reported to the user.
41003 Note the @samp{swbreak} feature implies that the target is responsible
41004 for adjusting the PC when a software breakpoint triggers, if
41005 necessary, such as on the x86 architecture.
41007 @node Packet Acknowledgment
41008 @section Packet Acknowledgment
41010 @cindex acknowledgment, for @value{GDBN} remote
41011 @cindex packet acknowledgment, for @value{GDBN} remote
41012 By default, when either the host or the target machine receives a packet,
41013 the first response expected is an acknowledgment: either @samp{+} (to indicate
41014 the package was received correctly) or @samp{-} (to request retransmission).
41015 This mechanism allows the @value{GDBN} remote protocol to operate over
41016 unreliable transport mechanisms, such as a serial line.
41018 In cases where the transport mechanism is itself reliable (such as a pipe or
41019 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
41020 It may be desirable to disable them in that case to reduce communication
41021 overhead, or for other reasons. This can be accomplished by means of the
41022 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
41024 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
41025 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
41026 and response format still includes the normal checksum, as described in
41027 @ref{Overview}, but the checksum may be ignored by the receiver.
41029 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
41030 no-acknowledgment mode, it should report that to @value{GDBN}
41031 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
41032 @pxref{qSupported}.
41033 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
41034 disabled via the @code{set remote noack-packet off} command
41035 (@pxref{Remote Configuration}),
41036 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
41037 Only then may the stub actually turn off packet acknowledgments.
41038 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
41039 response, which can be safely ignored by the stub.
41041 Note that @code{set remote noack-packet} command only affects negotiation
41042 between @value{GDBN} and the stub when subsequent connections are made;
41043 it does not affect the protocol acknowledgment state for any current
41045 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
41046 new connection is established,
41047 there is also no protocol request to re-enable the acknowledgments
41048 for the current connection, once disabled.
41053 Example sequence of a target being re-started. Notice how the restart
41054 does not get any direct output:
41059 @emph{target restarts}
41062 <- @code{T001:1234123412341234}
41066 Example sequence of a target being stepped by a single instruction:
41069 -> @code{G1445@dots{}}
41074 <- @code{T001:1234123412341234}
41078 <- @code{1455@dots{}}
41082 @node File-I/O Remote Protocol Extension
41083 @section File-I/O Remote Protocol Extension
41084 @cindex File-I/O remote protocol extension
41087 * File-I/O Overview::
41088 * Protocol Basics::
41089 * The F Request Packet::
41090 * The F Reply Packet::
41091 * The Ctrl-C Message::
41093 * List of Supported Calls::
41094 * Protocol-specific Representation of Datatypes::
41096 * File-I/O Examples::
41099 @node File-I/O Overview
41100 @subsection File-I/O Overview
41101 @cindex file-i/o overview
41103 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
41104 target to use the host's file system and console I/O to perform various
41105 system calls. System calls on the target system are translated into a
41106 remote protocol packet to the host system, which then performs the needed
41107 actions and returns a response packet to the target system.
41108 This simulates file system operations even on targets that lack file systems.
41110 The protocol is defined to be independent of both the host and target systems.
41111 It uses its own internal representation of datatypes and values. Both
41112 @value{GDBN} and the target's @value{GDBN} stub are responsible for
41113 translating the system-dependent value representations into the internal
41114 protocol representations when data is transmitted.
41116 The communication is synchronous. A system call is possible only when
41117 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
41118 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
41119 the target is stopped to allow deterministic access to the target's
41120 memory. Therefore File-I/O is not interruptible by target signals. On
41121 the other hand, it is possible to interrupt File-I/O by a user interrupt
41122 (@samp{Ctrl-C}) within @value{GDBN}.
41124 The target's request to perform a host system call does not finish
41125 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
41126 after finishing the system call, the target returns to continuing the
41127 previous activity (continue, step). No additional continue or step
41128 request from @value{GDBN} is required.
41131 (@value{GDBP}) continue
41132 <- target requests 'system call X'
41133 target is stopped, @value{GDBN} executes system call
41134 -> @value{GDBN} returns result
41135 ... target continues, @value{GDBN} returns to wait for the target
41136 <- target hits breakpoint and sends a Txx packet
41139 The protocol only supports I/O on the console and to regular files on
41140 the host file system. Character or block special devices, pipes,
41141 named pipes, sockets or any other communication method on the host
41142 system are not supported by this protocol.
41144 File I/O is not supported in non-stop mode.
41146 @node Protocol Basics
41147 @subsection Protocol Basics
41148 @cindex protocol basics, file-i/o
41150 The File-I/O protocol uses the @code{F} packet as the request as well
41151 as reply packet. Since a File-I/O system call can only occur when
41152 @value{GDBN} is waiting for a response from the continuing or stepping target,
41153 the File-I/O request is a reply that @value{GDBN} has to expect as a result
41154 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
41155 This @code{F} packet contains all information needed to allow @value{GDBN}
41156 to call the appropriate host system call:
41160 A unique identifier for the requested system call.
41163 All parameters to the system call. Pointers are given as addresses
41164 in the target memory address space. Pointers to strings are given as
41165 pointer/length pair. Numerical values are given as they are.
41166 Numerical control flags are given in a protocol-specific representation.
41170 At this point, @value{GDBN} has to perform the following actions.
41174 If the parameters include pointer values to data needed as input to a
41175 system call, @value{GDBN} requests this data from the target with a
41176 standard @code{m} packet request. This additional communication has to be
41177 expected by the target implementation and is handled as any other @code{m}
41181 @value{GDBN} translates all value from protocol representation to host
41182 representation as needed. Datatypes are coerced into the host types.
41185 @value{GDBN} calls the system call.
41188 It then coerces datatypes back to protocol representation.
41191 If the system call is expected to return data in buffer space specified
41192 by pointer parameters to the call, the data is transmitted to the
41193 target using a @code{M} or @code{X} packet. This packet has to be expected
41194 by the target implementation and is handled as any other @code{M} or @code{X}
41199 Eventually @value{GDBN} replies with another @code{F} packet which contains all
41200 necessary information for the target to continue. This at least contains
41207 @code{errno}, if has been changed by the system call.
41214 After having done the needed type and value coercion, the target continues
41215 the latest continue or step action.
41217 @node The F Request Packet
41218 @subsection The @code{F} Request Packet
41219 @cindex file-i/o request packet
41220 @cindex @code{F} request packet
41222 The @code{F} request packet has the following format:
41225 @item F@var{call-id},@var{parameter@dots{}}
41227 @var{call-id} is the identifier to indicate the host system call to be called.
41228 This is just the name of the function.
41230 @var{parameter@dots{}} are the parameters to the system call.
41231 Parameters are hexadecimal integer values, either the actual values in case
41232 of scalar datatypes, pointers to target buffer space in case of compound
41233 datatypes and unspecified memory areas, or pointer/length pairs in case
41234 of string parameters. These are appended to the @var{call-id} as a
41235 comma-delimited list. All values are transmitted in ASCII
41236 string representation, pointer/length pairs separated by a slash.
41242 @node The F Reply Packet
41243 @subsection The @code{F} Reply Packet
41244 @cindex file-i/o reply packet
41245 @cindex @code{F} reply packet
41247 The @code{F} reply packet has the following format:
41251 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
41253 @var{retcode} is the return code of the system call as hexadecimal value.
41255 @var{errno} is the @code{errno} set by the call, in protocol-specific
41257 This parameter can be omitted if the call was successful.
41259 @var{Ctrl-C flag} is only sent if the user requested a break. In this
41260 case, @var{errno} must be sent as well, even if the call was successful.
41261 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
41268 or, if the call was interrupted before the host call has been performed:
41275 assuming 4 is the protocol-specific representation of @code{EINTR}.
41280 @node The Ctrl-C Message
41281 @subsection The @samp{Ctrl-C} Message
41282 @cindex ctrl-c message, in file-i/o protocol
41284 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
41285 reply packet (@pxref{The F Reply Packet}),
41286 the target should behave as if it had
41287 gotten a break message. The meaning for the target is ``system call
41288 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
41289 (as with a break message) and return to @value{GDBN} with a @code{T02}
41292 It's important for the target to know in which
41293 state the system call was interrupted. There are two possible cases:
41297 The system call hasn't been performed on the host yet.
41300 The system call on the host has been finished.
41304 These two states can be distinguished by the target by the value of the
41305 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
41306 call hasn't been performed. This is equivalent to the @code{EINTR} handling
41307 on POSIX systems. In any other case, the target may presume that the
41308 system call has been finished --- successfully or not --- and should behave
41309 as if the break message arrived right after the system call.
41311 @value{GDBN} must behave reliably. If the system call has not been called
41312 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
41313 @code{errno} in the packet. If the system call on the host has been finished
41314 before the user requests a break, the full action must be finished by
41315 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
41316 The @code{F} packet may only be sent when either nothing has happened
41317 or the full action has been completed.
41320 @subsection Console I/O
41321 @cindex console i/o as part of file-i/o
41323 By default and if not explicitly closed by the target system, the file
41324 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41325 on the @value{GDBN} console is handled as any other file output operation
41326 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41327 by @value{GDBN} so that after the target read request from file descriptor
41328 0 all following typing is buffered until either one of the following
41333 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41335 system call is treated as finished.
41338 The user presses @key{RET}. This is treated as end of input with a trailing
41342 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41343 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41347 If the user has typed more characters than fit in the buffer given to
41348 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41349 either another @code{read(0, @dots{})} is requested by the target, or debugging
41350 is stopped at the user's request.
41353 @node List of Supported Calls
41354 @subsection List of Supported Calls
41355 @cindex list of supported file-i/o calls
41372 @unnumberedsubsubsec open
41373 @cindex open, file-i/o system call
41378 int open(const char *pathname, int flags);
41379 int open(const char *pathname, int flags, mode_t mode);
41383 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41386 @var{flags} is the bitwise @code{OR} of the following values:
41390 If the file does not exist it will be created. The host
41391 rules apply as far as file ownership and time stamps
41395 When used with @code{O_CREAT}, if the file already exists it is
41396 an error and open() fails.
41399 If the file already exists and the open mode allows
41400 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41401 truncated to zero length.
41404 The file is opened in append mode.
41407 The file is opened for reading only.
41410 The file is opened for writing only.
41413 The file is opened for reading and writing.
41417 Other bits are silently ignored.
41421 @var{mode} is the bitwise @code{OR} of the following values:
41425 User has read permission.
41428 User has write permission.
41431 Group has read permission.
41434 Group has write permission.
41437 Others have read permission.
41440 Others have write permission.
41444 Other bits are silently ignored.
41447 @item Return value:
41448 @code{open} returns the new file descriptor or -1 if an error
41455 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41458 @var{pathname} refers to a directory.
41461 The requested access is not allowed.
41464 @var{pathname} was too long.
41467 A directory component in @var{pathname} does not exist.
41470 @var{pathname} refers to a device, pipe, named pipe or socket.
41473 @var{pathname} refers to a file on a read-only filesystem and
41474 write access was requested.
41477 @var{pathname} is an invalid pointer value.
41480 No space on device to create the file.
41483 The process already has the maximum number of files open.
41486 The limit on the total number of files open on the system
41490 The call was interrupted by the user.
41496 @unnumberedsubsubsec close
41497 @cindex close, file-i/o system call
41506 @samp{Fclose,@var{fd}}
41508 @item Return value:
41509 @code{close} returns zero on success, or -1 if an error occurred.
41515 @var{fd} isn't a valid open file descriptor.
41518 The call was interrupted by the user.
41524 @unnumberedsubsubsec read
41525 @cindex read, file-i/o system call
41530 int read(int fd, void *buf, unsigned int count);
41534 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41536 @item Return value:
41537 On success, the number of bytes read is returned.
41538 Zero indicates end of file. If count is zero, read
41539 returns zero as well. On error, -1 is returned.
41545 @var{fd} is not a valid file descriptor or is not open for
41549 @var{bufptr} is an invalid pointer value.
41552 The call was interrupted by the user.
41558 @unnumberedsubsubsec write
41559 @cindex write, file-i/o system call
41564 int write(int fd, const void *buf, unsigned int count);
41568 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41570 @item Return value:
41571 On success, the number of bytes written are returned.
41572 Zero indicates nothing was written. On error, -1
41579 @var{fd} is not a valid file descriptor or is not open for
41583 @var{bufptr} is an invalid pointer value.
41586 An attempt was made to write a file that exceeds the
41587 host-specific maximum file size allowed.
41590 No space on device to write the data.
41593 The call was interrupted by the user.
41599 @unnumberedsubsubsec lseek
41600 @cindex lseek, file-i/o system call
41605 long lseek (int fd, long offset, int flag);
41609 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41611 @var{flag} is one of:
41615 The offset is set to @var{offset} bytes.
41618 The offset is set to its current location plus @var{offset}
41622 The offset is set to the size of the file plus @var{offset}
41626 @item Return value:
41627 On success, the resulting unsigned offset in bytes from
41628 the beginning of the file is returned. Otherwise, a
41629 value of -1 is returned.
41635 @var{fd} is not a valid open file descriptor.
41638 @var{fd} is associated with the @value{GDBN} console.
41641 @var{flag} is not a proper value.
41644 The call was interrupted by the user.
41650 @unnumberedsubsubsec rename
41651 @cindex rename, file-i/o system call
41656 int rename(const char *oldpath, const char *newpath);
41660 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41662 @item Return value:
41663 On success, zero is returned. On error, -1 is returned.
41669 @var{newpath} is an existing directory, but @var{oldpath} is not a
41673 @var{newpath} is a non-empty directory.
41676 @var{oldpath} or @var{newpath} is a directory that is in use by some
41680 An attempt was made to make a directory a subdirectory
41684 A component used as a directory in @var{oldpath} or new
41685 path is not a directory. Or @var{oldpath} is a directory
41686 and @var{newpath} exists but is not a directory.
41689 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41692 No access to the file or the path of the file.
41696 @var{oldpath} or @var{newpath} was too long.
41699 A directory component in @var{oldpath} or @var{newpath} does not exist.
41702 The file is on a read-only filesystem.
41705 The device containing the file has no room for the new
41709 The call was interrupted by the user.
41715 @unnumberedsubsubsec unlink
41716 @cindex unlink, file-i/o system call
41721 int unlink(const char *pathname);
41725 @samp{Funlink,@var{pathnameptr}/@var{len}}
41727 @item Return value:
41728 On success, zero is returned. On error, -1 is returned.
41734 No access to the file or the path of the file.
41737 The system does not allow unlinking of directories.
41740 The file @var{pathname} cannot be unlinked because it's
41741 being used by another process.
41744 @var{pathnameptr} is an invalid pointer value.
41747 @var{pathname} was too long.
41750 A directory component in @var{pathname} does not exist.
41753 A component of the path is not a directory.
41756 The file is on a read-only filesystem.
41759 The call was interrupted by the user.
41765 @unnumberedsubsubsec stat/fstat
41766 @cindex fstat, file-i/o system call
41767 @cindex stat, file-i/o system call
41772 int stat(const char *pathname, struct stat *buf);
41773 int fstat(int fd, struct stat *buf);
41777 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41778 @samp{Ffstat,@var{fd},@var{bufptr}}
41780 @item Return value:
41781 On success, zero is returned. On error, -1 is returned.
41787 @var{fd} is not a valid open file.
41790 A directory component in @var{pathname} does not exist or the
41791 path is an empty string.
41794 A component of the path is not a directory.
41797 @var{pathnameptr} is an invalid pointer value.
41800 No access to the file or the path of the file.
41803 @var{pathname} was too long.
41806 The call was interrupted by the user.
41812 @unnumberedsubsubsec gettimeofday
41813 @cindex gettimeofday, file-i/o system call
41818 int gettimeofday(struct timeval *tv, void *tz);
41822 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41824 @item Return value:
41825 On success, 0 is returned, -1 otherwise.
41831 @var{tz} is a non-NULL pointer.
41834 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41840 @unnumberedsubsubsec isatty
41841 @cindex isatty, file-i/o system call
41846 int isatty(int fd);
41850 @samp{Fisatty,@var{fd}}
41852 @item Return value:
41853 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
41859 The call was interrupted by the user.
41864 Note that the @code{isatty} call is treated as a special case: it returns
41865 1 to the target if the file descriptor is attached
41866 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
41867 would require implementing @code{ioctl} and would be more complex than
41872 @unnumberedsubsubsec system
41873 @cindex system, file-i/o system call
41878 int system(const char *command);
41882 @samp{Fsystem,@var{commandptr}/@var{len}}
41884 @item Return value:
41885 If @var{len} is zero, the return value indicates whether a shell is
41886 available. A zero return value indicates a shell is not available.
41887 For non-zero @var{len}, the value returned is -1 on error and the
41888 return status of the command otherwise. Only the exit status of the
41889 command is returned, which is extracted from the host's @code{system}
41890 return value by calling @code{WEXITSTATUS(retval)}. In case
41891 @file{/bin/sh} could not be executed, 127 is returned.
41897 The call was interrupted by the user.
41902 @value{GDBN} takes over the full task of calling the necessary host calls
41903 to perform the @code{system} call. The return value of @code{system} on
41904 the host is simplified before it's returned
41905 to the target. Any termination signal information from the child process
41906 is discarded, and the return value consists
41907 entirely of the exit status of the called command.
41909 Due to security concerns, the @code{system} call is by default refused
41910 by @value{GDBN}. The user has to allow this call explicitly with the
41911 @code{set remote system-call-allowed 1} command.
41914 @item set remote system-call-allowed
41915 @kindex set remote system-call-allowed
41916 Control whether to allow the @code{system} calls in the File I/O
41917 protocol for the remote target. The default is zero (disabled).
41919 @item show remote system-call-allowed
41920 @kindex show remote system-call-allowed
41921 Show whether the @code{system} calls are allowed in the File I/O
41925 @node Protocol-specific Representation of Datatypes
41926 @subsection Protocol-specific Representation of Datatypes
41927 @cindex protocol-specific representation of datatypes, in file-i/o protocol
41930 * Integral Datatypes::
41932 * Memory Transfer::
41937 @node Integral Datatypes
41938 @unnumberedsubsubsec Integral Datatypes
41939 @cindex integral datatypes, in file-i/o protocol
41941 The integral datatypes used in the system calls are @code{int},
41942 @code{unsigned int}, @code{long}, @code{unsigned long},
41943 @code{mode_t}, and @code{time_t}.
41945 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
41946 implemented as 32 bit values in this protocol.
41948 @code{long} and @code{unsigned long} are implemented as 64 bit types.
41950 @xref{Limits}, for corresponding MIN and MAX values (similar to those
41951 in @file{limits.h}) to allow range checking on host and target.
41953 @code{time_t} datatypes are defined as seconds since the Epoch.
41955 All integral datatypes transferred as part of a memory read or write of a
41956 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
41959 @node Pointer Values
41960 @unnumberedsubsubsec Pointer Values
41961 @cindex pointer values, in file-i/o protocol
41963 Pointers to target data are transmitted as they are. An exception
41964 is made for pointers to buffers for which the length isn't
41965 transmitted as part of the function call, namely strings. Strings
41966 are transmitted as a pointer/length pair, both as hex values, e.g.@:
41973 which is a pointer to data of length 18 bytes at position 0x1aaf.
41974 The length is defined as the full string length in bytes, including
41975 the trailing null byte. For example, the string @code{"hello world"}
41976 at address 0x123456 is transmitted as
41982 @node Memory Transfer
41983 @unnumberedsubsubsec Memory Transfer
41984 @cindex memory transfer, in file-i/o protocol
41986 Structured data which is transferred using a memory read or write (for
41987 example, a @code{struct stat}) is expected to be in a protocol-specific format
41988 with all scalar multibyte datatypes being big endian. Translation to
41989 this representation needs to be done both by the target before the @code{F}
41990 packet is sent, and by @value{GDBN} before
41991 it transfers memory to the target. Transferred pointers to structured
41992 data should point to the already-coerced data at any time.
41996 @unnumberedsubsubsec struct stat
41997 @cindex struct stat, in file-i/o protocol
41999 The buffer of type @code{struct stat} used by the target and @value{GDBN}
42000 is defined as follows:
42004 unsigned int st_dev; /* device */
42005 unsigned int st_ino; /* inode */
42006 mode_t st_mode; /* protection */
42007 unsigned int st_nlink; /* number of hard links */
42008 unsigned int st_uid; /* user ID of owner */
42009 unsigned int st_gid; /* group ID of owner */
42010 unsigned int st_rdev; /* device type (if inode device) */
42011 unsigned long st_size; /* total size, in bytes */
42012 unsigned long st_blksize; /* blocksize for filesystem I/O */
42013 unsigned long st_blocks; /* number of blocks allocated */
42014 time_t st_atime; /* time of last access */
42015 time_t st_mtime; /* time of last modification */
42016 time_t st_ctime; /* time of last change */
42020 The integral datatypes conform to the definitions given in the
42021 appropriate section (see @ref{Integral Datatypes}, for details) so this
42022 structure is of size 64 bytes.
42024 The values of several fields have a restricted meaning and/or
42030 A value of 0 represents a file, 1 the console.
42033 No valid meaning for the target. Transmitted unchanged.
42036 Valid mode bits are described in @ref{Constants}. Any other
42037 bits have currently no meaning for the target.
42042 No valid meaning for the target. Transmitted unchanged.
42047 These values have a host and file system dependent
42048 accuracy. Especially on Windows hosts, the file system may not
42049 support exact timing values.
42052 The target gets a @code{struct stat} of the above representation and is
42053 responsible for coercing it to the target representation before
42056 Note that due to size differences between the host, target, and protocol
42057 representations of @code{struct stat} members, these members could eventually
42058 get truncated on the target.
42060 @node struct timeval
42061 @unnumberedsubsubsec struct timeval
42062 @cindex struct timeval, in file-i/o protocol
42064 The buffer of type @code{struct timeval} used by the File-I/O protocol
42065 is defined as follows:
42069 time_t tv_sec; /* second */
42070 long tv_usec; /* microsecond */
42074 The integral datatypes conform to the definitions given in the
42075 appropriate section (see @ref{Integral Datatypes}, for details) so this
42076 structure is of size 8 bytes.
42079 @subsection Constants
42080 @cindex constants, in file-i/o protocol
42082 The following values are used for the constants inside of the
42083 protocol. @value{GDBN} and target are responsible for translating these
42084 values before and after the call as needed.
42095 @unnumberedsubsubsec Open Flags
42096 @cindex open flags, in file-i/o protocol
42098 All values are given in hexadecimal representation.
42110 @node mode_t Values
42111 @unnumberedsubsubsec mode_t Values
42112 @cindex mode_t values, in file-i/o protocol
42114 All values are given in octal representation.
42131 @unnumberedsubsubsec Errno Values
42132 @cindex errno values, in file-i/o protocol
42134 All values are given in decimal representation.
42159 @code{EUNKNOWN} is used as a fallback error value if a host system returns
42160 any error value not in the list of supported error numbers.
42163 @unnumberedsubsubsec Lseek Flags
42164 @cindex lseek flags, in file-i/o protocol
42173 @unnumberedsubsubsec Limits
42174 @cindex limits, in file-i/o protocol
42176 All values are given in decimal representation.
42179 INT_MIN -2147483648
42181 UINT_MAX 4294967295
42182 LONG_MIN -9223372036854775808
42183 LONG_MAX 9223372036854775807
42184 ULONG_MAX 18446744073709551615
42187 @node File-I/O Examples
42188 @subsection File-I/O Examples
42189 @cindex file-i/o examples
42191 Example sequence of a write call, file descriptor 3, buffer is at target
42192 address 0x1234, 6 bytes should be written:
42195 <- @code{Fwrite,3,1234,6}
42196 @emph{request memory read from target}
42199 @emph{return "6 bytes written"}
42203 Example sequence of a read call, file descriptor 3, buffer is at target
42204 address 0x1234, 6 bytes should be read:
42207 <- @code{Fread,3,1234,6}
42208 @emph{request memory write to target}
42209 -> @code{X1234,6:XXXXXX}
42210 @emph{return "6 bytes read"}
42214 Example sequence of a read call, call fails on the host due to invalid
42215 file descriptor (@code{EBADF}):
42218 <- @code{Fread,3,1234,6}
42222 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
42226 <- @code{Fread,3,1234,6}
42231 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
42235 <- @code{Fread,3,1234,6}
42236 -> @code{X1234,6:XXXXXX}
42240 @node Library List Format
42241 @section Library List Format
42242 @cindex library list format, remote protocol
42244 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
42245 same process as your application to manage libraries. In this case,
42246 @value{GDBN} can use the loader's symbol table and normal memory
42247 operations to maintain a list of shared libraries. On other
42248 platforms, the operating system manages loaded libraries.
42249 @value{GDBN} can not retrieve the list of currently loaded libraries
42250 through memory operations, so it uses the @samp{qXfer:libraries:read}
42251 packet (@pxref{qXfer library list read}) instead. The remote stub
42252 queries the target's operating system and reports which libraries
42255 The @samp{qXfer:libraries:read} packet returns an XML document which
42256 lists loaded libraries and their offsets. Each library has an
42257 associated name and one or more segment or section base addresses,
42258 which report where the library was loaded in memory.
42260 For the common case of libraries that are fully linked binaries, the
42261 library should have a list of segments. If the target supports
42262 dynamic linking of a relocatable object file, its library XML element
42263 should instead include a list of allocated sections. The segment or
42264 section bases are start addresses, not relocation offsets; they do not
42265 depend on the library's link-time base addresses.
42267 @value{GDBN} must be linked with the Expat library to support XML
42268 library lists. @xref{Expat}.
42270 A simple memory map, with one loaded library relocated by a single
42271 offset, looks like this:
42275 <library name="/lib/libc.so.6">
42276 <segment address="0x10000000"/>
42281 Another simple memory map, with one loaded library with three
42282 allocated sections (.text, .data, .bss), looks like this:
42286 <library name="sharedlib.o">
42287 <section address="0x10000000"/>
42288 <section address="0x20000000"/>
42289 <section address="0x30000000"/>
42294 The format of a library list is described by this DTD:
42297 <!-- library-list: Root element with versioning -->
42298 <!ELEMENT library-list (library)*>
42299 <!ATTLIST library-list version CDATA #FIXED "1.0">
42300 <!ELEMENT library (segment*, section*)>
42301 <!ATTLIST library name CDATA #REQUIRED>
42302 <!ELEMENT segment EMPTY>
42303 <!ATTLIST segment address CDATA #REQUIRED>
42304 <!ELEMENT section EMPTY>
42305 <!ATTLIST section address CDATA #REQUIRED>
42308 In addition, segments and section descriptors cannot be mixed within a
42309 single library element, and you must supply at least one segment or
42310 section for each library.
42312 @node Library List Format for SVR4 Targets
42313 @section Library List Format for SVR4 Targets
42314 @cindex library list format, remote protocol
42316 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
42317 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42318 shared libraries. Still a special library list provided by this packet is
42319 more efficient for the @value{GDBN} remote protocol.
42321 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42322 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42323 target, the following parameters are reported:
42327 @code{name}, the absolute file name from the @code{l_name} field of
42328 @code{struct link_map}.
42330 @code{lm} with address of @code{struct link_map} used for TLS
42331 (Thread Local Storage) access.
42333 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42334 @code{struct link_map}. For prelinked libraries this is not an absolute
42335 memory address. It is a displacement of absolute memory address against
42336 address the file was prelinked to during the library load.
42338 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42341 Additionally the single @code{main-lm} attribute specifies address of
42342 @code{struct link_map} used for the main executable. This parameter is used
42343 for TLS access and its presence is optional.
42345 @value{GDBN} must be linked with the Expat library to support XML
42346 SVR4 library lists. @xref{Expat}.
42348 A simple memory map, with two loaded libraries (which do not use prelink),
42352 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42353 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42355 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42357 </library-list-svr>
42360 The format of an SVR4 library list is described by this DTD:
42363 <!-- library-list-svr4: Root element with versioning -->
42364 <!ELEMENT library-list-svr4 (library)*>
42365 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42366 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42367 <!ELEMENT library EMPTY>
42368 <!ATTLIST library name CDATA #REQUIRED>
42369 <!ATTLIST library lm CDATA #REQUIRED>
42370 <!ATTLIST library l_addr CDATA #REQUIRED>
42371 <!ATTLIST library l_ld CDATA #REQUIRED>
42374 @node Memory Map Format
42375 @section Memory Map Format
42376 @cindex memory map format
42378 To be able to write into flash memory, @value{GDBN} needs to obtain a
42379 memory map from the target. This section describes the format of the
42382 The memory map is obtained using the @samp{qXfer:memory-map:read}
42383 (@pxref{qXfer memory map read}) packet and is an XML document that
42384 lists memory regions.
42386 @value{GDBN} must be linked with the Expat library to support XML
42387 memory maps. @xref{Expat}.
42389 The top-level structure of the document is shown below:
42392 <?xml version="1.0"?>
42393 <!DOCTYPE memory-map
42394 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42395 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42401 Each region can be either:
42406 A region of RAM starting at @var{addr} and extending for @var{length}
42410 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42415 A region of read-only memory:
42418 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42423 A region of flash memory, with erasure blocks @var{blocksize}
42427 <memory type="flash" start="@var{addr}" length="@var{length}">
42428 <property name="blocksize">@var{blocksize}</property>
42434 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42435 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42436 packets to write to addresses in such ranges.
42438 The formal DTD for memory map format is given below:
42441 <!-- ................................................... -->
42442 <!-- Memory Map XML DTD ................................ -->
42443 <!-- File: memory-map.dtd .............................. -->
42444 <!-- .................................... .............. -->
42445 <!-- memory-map.dtd -->
42446 <!-- memory-map: Root element with versioning -->
42447 <!ELEMENT memory-map (memory)*>
42448 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42449 <!ELEMENT memory (property)*>
42450 <!-- memory: Specifies a memory region,
42451 and its type, or device. -->
42452 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
42453 start CDATA #REQUIRED
42454 length CDATA #REQUIRED>
42455 <!-- property: Generic attribute tag -->
42456 <!ELEMENT property (#PCDATA | property)*>
42457 <!ATTLIST property name (blocksize) #REQUIRED>
42460 @node Thread List Format
42461 @section Thread List Format
42462 @cindex thread list format
42464 To efficiently update the list of threads and their attributes,
42465 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42466 (@pxref{qXfer threads read}) and obtains the XML document with
42467 the following structure:
42470 <?xml version="1.0"?>
42472 <thread id="id" core="0" name="name">
42473 ... description ...
42478 Each @samp{thread} element must have the @samp{id} attribute that
42479 identifies the thread (@pxref{thread-id syntax}). The
42480 @samp{core} attribute, if present, specifies which processor core
42481 the thread was last executing on. The @samp{name} attribute, if
42482 present, specifies the human-readable name of the thread. The content
42483 of the of @samp{thread} element is interpreted as human-readable
42484 auxiliary information. The @samp{handle} attribute, if present,
42485 is a hex encoded representation of the thread handle.
42488 @node Traceframe Info Format
42489 @section Traceframe Info Format
42490 @cindex traceframe info format
42492 To be able to know which objects in the inferior can be examined when
42493 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42494 memory ranges, registers and trace state variables that have been
42495 collected in a traceframe.
42497 This list is obtained using the @samp{qXfer:traceframe-info:read}
42498 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42500 @value{GDBN} must be linked with the Expat library to support XML
42501 traceframe info discovery. @xref{Expat}.
42503 The top-level structure of the document is shown below:
42506 <?xml version="1.0"?>
42507 <!DOCTYPE traceframe-info
42508 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42509 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42515 Each traceframe block can be either:
42520 A region of collected memory starting at @var{addr} and extending for
42521 @var{length} bytes from there:
42524 <memory start="@var{addr}" length="@var{length}"/>
42528 A block indicating trace state variable numbered @var{number} has been
42532 <tvar id="@var{number}"/>
42537 The formal DTD for the traceframe info format is given below:
42540 <!ELEMENT traceframe-info (memory | tvar)* >
42541 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42543 <!ELEMENT memory EMPTY>
42544 <!ATTLIST memory start CDATA #REQUIRED
42545 length CDATA #REQUIRED>
42547 <!ATTLIST tvar id CDATA #REQUIRED>
42550 @node Branch Trace Format
42551 @section Branch Trace Format
42552 @cindex branch trace format
42554 In order to display the branch trace of an inferior thread,
42555 @value{GDBN} needs to obtain the list of branches. This list is
42556 represented as list of sequential code blocks that are connected via
42557 branches. The code in each block has been executed sequentially.
42559 This list is obtained using the @samp{qXfer:btrace:read}
42560 (@pxref{qXfer btrace read}) packet and is an XML document.
42562 @value{GDBN} must be linked with the Expat library to support XML
42563 traceframe info discovery. @xref{Expat}.
42565 The top-level structure of the document is shown below:
42568 <?xml version="1.0"?>
42570 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42571 "http://sourceware.org/gdb/gdb-btrace.dtd">
42580 A block of sequentially executed instructions starting at @var{begin}
42581 and ending at @var{end}:
42584 <block begin="@var{begin}" end="@var{end}"/>
42589 The formal DTD for the branch trace format is given below:
42592 <!ELEMENT btrace (block* | pt) >
42593 <!ATTLIST btrace version CDATA #FIXED "1.0">
42595 <!ELEMENT block EMPTY>
42596 <!ATTLIST block begin CDATA #REQUIRED
42597 end CDATA #REQUIRED>
42599 <!ELEMENT pt (pt-config?, raw?)>
42601 <!ELEMENT pt-config (cpu?)>
42603 <!ELEMENT cpu EMPTY>
42604 <!ATTLIST cpu vendor CDATA #REQUIRED
42605 family CDATA #REQUIRED
42606 model CDATA #REQUIRED
42607 stepping CDATA #REQUIRED>
42609 <!ELEMENT raw (#PCDATA)>
42612 @node Branch Trace Configuration Format
42613 @section Branch Trace Configuration Format
42614 @cindex branch trace configuration format
42616 For each inferior thread, @value{GDBN} can obtain the branch trace
42617 configuration using the @samp{qXfer:btrace-conf:read}
42618 (@pxref{qXfer btrace-conf read}) packet.
42620 The configuration describes the branch trace format and configuration
42621 settings for that format. The following information is described:
42625 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
42628 The size of the @acronym{BTS} ring buffer in bytes.
42631 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
42635 The size of the @acronym{Intel PT} ring buffer in bytes.
42639 @value{GDBN} must be linked with the Expat library to support XML
42640 branch trace configuration discovery. @xref{Expat}.
42642 The formal DTD for the branch trace configuration format is given below:
42645 <!ELEMENT btrace-conf (bts?, pt?)>
42646 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
42648 <!ELEMENT bts EMPTY>
42649 <!ATTLIST bts size CDATA #IMPLIED>
42651 <!ELEMENT pt EMPTY>
42652 <!ATTLIST pt size CDATA #IMPLIED>
42655 @include agentexpr.texi
42657 @node Target Descriptions
42658 @appendix Target Descriptions
42659 @cindex target descriptions
42661 One of the challenges of using @value{GDBN} to debug embedded systems
42662 is that there are so many minor variants of each processor
42663 architecture in use. It is common practice for vendors to start with
42664 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42665 and then make changes to adapt it to a particular market niche. Some
42666 architectures have hundreds of variants, available from dozens of
42667 vendors. This leads to a number of problems:
42671 With so many different customized processors, it is difficult for
42672 the @value{GDBN} maintainers to keep up with the changes.
42674 Since individual variants may have short lifetimes or limited
42675 audiences, it may not be worthwhile to carry information about every
42676 variant in the @value{GDBN} source tree.
42678 When @value{GDBN} does support the architecture of the embedded system
42679 at hand, the task of finding the correct architecture name to give the
42680 @command{set architecture} command can be error-prone.
42683 To address these problems, the @value{GDBN} remote protocol allows a
42684 target system to not only identify itself to @value{GDBN}, but to
42685 actually describe its own features. This lets @value{GDBN} support
42686 processor variants it has never seen before --- to the extent that the
42687 descriptions are accurate, and that @value{GDBN} understands them.
42689 @value{GDBN} must be linked with the Expat library to support XML
42690 target descriptions. @xref{Expat}.
42693 * Retrieving Descriptions:: How descriptions are fetched from a target.
42694 * Target Description Format:: The contents of a target description.
42695 * Predefined Target Types:: Standard types available for target
42697 * Enum Target Types:: How to define enum target types.
42698 * Standard Target Features:: Features @value{GDBN} knows about.
42701 @node Retrieving Descriptions
42702 @section Retrieving Descriptions
42704 Target descriptions can be read from the target automatically, or
42705 specified by the user manually. The default behavior is to read the
42706 description from the target. @value{GDBN} retrieves it via the remote
42707 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42708 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42709 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42710 XML document, of the form described in @ref{Target Description
42713 Alternatively, you can specify a file to read for the target description.
42714 If a file is set, the target will not be queried. The commands to
42715 specify a file are:
42718 @cindex set tdesc filename
42719 @item set tdesc filename @var{path}
42720 Read the target description from @var{path}.
42722 @cindex unset tdesc filename
42723 @item unset tdesc filename
42724 Do not read the XML target description from a file. @value{GDBN}
42725 will use the description supplied by the current target.
42727 @cindex show tdesc filename
42728 @item show tdesc filename
42729 Show the filename to read for a target description, if any.
42733 @node Target Description Format
42734 @section Target Description Format
42735 @cindex target descriptions, XML format
42737 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42738 document which complies with the Document Type Definition provided in
42739 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42740 means you can use generally available tools like @command{xmllint} to
42741 check that your feature descriptions are well-formed and valid.
42742 However, to help people unfamiliar with XML write descriptions for
42743 their targets, we also describe the grammar here.
42745 Target descriptions can identify the architecture of the remote target
42746 and (for some architectures) provide information about custom register
42747 sets. They can also identify the OS ABI of the remote target.
42748 @value{GDBN} can use this information to autoconfigure for your
42749 target, or to warn you if you connect to an unsupported target.
42751 Here is a simple target description:
42754 <target version="1.0">
42755 <architecture>i386:x86-64</architecture>
42760 This minimal description only says that the target uses
42761 the x86-64 architecture.
42763 A target description has the following overall form, with [ ] marking
42764 optional elements and @dots{} marking repeatable elements. The elements
42765 are explained further below.
42768 <?xml version="1.0"?>
42769 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42770 <target version="1.0">
42771 @r{[}@var{architecture}@r{]}
42772 @r{[}@var{osabi}@r{]}
42773 @r{[}@var{compatible}@r{]}
42774 @r{[}@var{feature}@dots{}@r{]}
42779 The description is generally insensitive to whitespace and line
42780 breaks, under the usual common-sense rules. The XML version
42781 declaration and document type declaration can generally be omitted
42782 (@value{GDBN} does not require them), but specifying them may be
42783 useful for XML validation tools. The @samp{version} attribute for
42784 @samp{<target>} may also be omitted, but we recommend
42785 including it; if future versions of @value{GDBN} use an incompatible
42786 revision of @file{gdb-target.dtd}, they will detect and report
42787 the version mismatch.
42789 @subsection Inclusion
42790 @cindex target descriptions, inclusion
42793 @cindex <xi:include>
42796 It can sometimes be valuable to split a target description up into
42797 several different annexes, either for organizational purposes, or to
42798 share files between different possible target descriptions. You can
42799 divide a description into multiple files by replacing any element of
42800 the target description with an inclusion directive of the form:
42803 <xi:include href="@var{document}"/>
42807 When @value{GDBN} encounters an element of this form, it will retrieve
42808 the named XML @var{document}, and replace the inclusion directive with
42809 the contents of that document. If the current description was read
42810 using @samp{qXfer}, then so will be the included document;
42811 @var{document} will be interpreted as the name of an annex. If the
42812 current description was read from a file, @value{GDBN} will look for
42813 @var{document} as a file in the same directory where it found the
42814 original description.
42816 @subsection Architecture
42817 @cindex <architecture>
42819 An @samp{<architecture>} element has this form:
42822 <architecture>@var{arch}</architecture>
42825 @var{arch} is one of the architectures from the set accepted by
42826 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42829 @cindex @code{<osabi>}
42831 This optional field was introduced in @value{GDBN} version 7.0.
42832 Previous versions of @value{GDBN} ignore it.
42834 An @samp{<osabi>} element has this form:
42837 <osabi>@var{abi-name}</osabi>
42840 @var{abi-name} is an OS ABI name from the same selection accepted by
42841 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42843 @subsection Compatible Architecture
42844 @cindex @code{<compatible>}
42846 This optional field was introduced in @value{GDBN} version 7.0.
42847 Previous versions of @value{GDBN} ignore it.
42849 A @samp{<compatible>} element has this form:
42852 <compatible>@var{arch}</compatible>
42855 @var{arch} is one of the architectures from the set accepted by
42856 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42858 A @samp{<compatible>} element is used to specify that the target
42859 is able to run binaries in some other than the main target architecture
42860 given by the @samp{<architecture>} element. For example, on the
42861 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42862 or @code{powerpc:common64}, but the system is able to run binaries
42863 in the @code{spu} architecture as well. The way to describe this
42864 capability with @samp{<compatible>} is as follows:
42867 <architecture>powerpc:common</architecture>
42868 <compatible>spu</compatible>
42871 @subsection Features
42874 Each @samp{<feature>} describes some logical portion of the target
42875 system. Features are currently used to describe available CPU
42876 registers and the types of their contents. A @samp{<feature>} element
42880 <feature name="@var{name}">
42881 @r{[}@var{type}@dots{}@r{]}
42887 Each feature's name should be unique within the description. The name
42888 of a feature does not matter unless @value{GDBN} has some special
42889 knowledge of the contents of that feature; if it does, the feature
42890 should have its standard name. @xref{Standard Target Features}.
42894 Any register's value is a collection of bits which @value{GDBN} must
42895 interpret. The default interpretation is a two's complement integer,
42896 but other types can be requested by name in the register description.
42897 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
42898 Target Types}), and the description can define additional composite
42901 Each type element must have an @samp{id} attribute, which gives
42902 a unique (within the containing @samp{<feature>}) name to the type.
42903 Types must be defined before they are used.
42906 Some targets offer vector registers, which can be treated as arrays
42907 of scalar elements. These types are written as @samp{<vector>} elements,
42908 specifying the array element type, @var{type}, and the number of elements,
42912 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
42916 If a register's value is usefully viewed in multiple ways, define it
42917 with a union type containing the useful representations. The
42918 @samp{<union>} element contains one or more @samp{<field>} elements,
42919 each of which has a @var{name} and a @var{type}:
42922 <union id="@var{id}">
42923 <field name="@var{name}" type="@var{type}"/>
42930 If a register's value is composed from several separate values, define
42931 it with either a structure type or a flags type.
42932 A flags type may only contain bitfields.
42933 A structure type may either contain only bitfields or contain no bitfields.
42934 If the value contains only bitfields, its total size in bytes must be
42937 Non-bitfield values have a @var{name} and @var{type}.
42940 <struct id="@var{id}">
42941 <field name="@var{name}" type="@var{type}"/>
42946 Both @var{name} and @var{type} values are required.
42947 No implicit padding is added.
42949 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
42952 <struct id="@var{id}" size="@var{size}">
42953 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
42959 <flags id="@var{id}" size="@var{size}">
42960 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
42965 The @var{name} value is required.
42966 Bitfield values may be named with the empty string, @samp{""},
42967 in which case the field is ``filler'' and its value is not printed.
42968 Not all bits need to be specified, so ``filler'' fields are optional.
42970 The @var{start} and @var{end} values are required, and @var{type}
42972 The field's @var{start} must be less than or equal to its @var{end},
42973 and zero represents the least significant bit.
42975 The default value of @var{type} is @code{bool} for single bit fields,
42976 and an unsigned integer otherwise.
42978 Which to choose? Structures or flags?
42980 Registers defined with @samp{flags} have these advantages over
42981 defining them with @samp{struct}:
42985 Arithmetic may be performed on them as if they were integers.
42987 They are printed in a more readable fashion.
42990 Registers defined with @samp{struct} have one advantage over
42991 defining them with @samp{flags}:
42995 One can fetch individual fields like in @samp{C}.
42998 (gdb) print $my_struct_reg.field3
43004 @subsection Registers
43007 Each register is represented as an element with this form:
43010 <reg name="@var{name}"
43011 bitsize="@var{size}"
43012 @r{[}regnum="@var{num}"@r{]}
43013 @r{[}save-restore="@var{save-restore}"@r{]}
43014 @r{[}type="@var{type}"@r{]}
43015 @r{[}group="@var{group}"@r{]}/>
43019 The components are as follows:
43024 The register's name; it must be unique within the target description.
43027 The register's size, in bits.
43030 The register's number. If omitted, a register's number is one greater
43031 than that of the previous register (either in the current feature or in
43032 a preceding feature); the first register in the target description
43033 defaults to zero. This register number is used to read or write
43034 the register; e.g.@: it is used in the remote @code{p} and @code{P}
43035 packets, and registers appear in the @code{g} and @code{G} packets
43036 in order of increasing register number.
43039 Whether the register should be preserved across inferior function
43040 calls; this must be either @code{yes} or @code{no}. The default is
43041 @code{yes}, which is appropriate for most registers except for
43042 some system control registers; this is not related to the target's
43046 The type of the register. It may be a predefined type, a type
43047 defined in the current feature, or one of the special types @code{int}
43048 and @code{float}. @code{int} is an integer type of the correct size
43049 for @var{bitsize}, and @code{float} is a floating point type (in the
43050 architecture's normal floating point format) of the correct size for
43051 @var{bitsize}. The default is @code{int}.
43054 The register group to which this register belongs. It can be one of the
43055 standard register groups @code{general}, @code{float}, @code{vector} or an
43056 arbitrary string. Group names should be limited to alphanumeric characters.
43057 If a group name is made up of multiple words the words may be separated by
43058 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
43059 @var{group} is specified, @value{GDBN} will not display the register in
43060 @code{info registers}.
43064 @node Predefined Target Types
43065 @section Predefined Target Types
43066 @cindex target descriptions, predefined types
43068 Type definitions in the self-description can build up composite types
43069 from basic building blocks, but can not define fundamental types. Instead,
43070 standard identifiers are provided by @value{GDBN} for the fundamental
43071 types. The currently supported types are:
43076 Boolean type, occupying a single bit.
43084 Signed integer types holding the specified number of bits.
43092 Unsigned integer types holding the specified number of bits.
43096 Pointers to unspecified code and data. The program counter and
43097 any dedicated return address register may be marked as code
43098 pointers; printing a code pointer converts it into a symbolic
43099 address. The stack pointer and any dedicated address registers
43100 may be marked as data pointers.
43103 Single precision IEEE floating point.
43106 Double precision IEEE floating point.
43109 The 12-byte extended precision format used by ARM FPA registers.
43112 The 10-byte extended precision format used by x87 registers.
43115 32bit @sc{eflags} register used by x86.
43118 32bit @sc{mxcsr} register used by x86.
43122 @node Enum Target Types
43123 @section Enum Target Types
43124 @cindex target descriptions, enum types
43126 Enum target types are useful in @samp{struct} and @samp{flags}
43127 register descriptions. @xref{Target Description Format}.
43129 Enum types have a name, size and a list of name/value pairs.
43132 <enum id="@var{id}" size="@var{size}">
43133 <evalue name="@var{name}" value="@var{value}"/>
43138 Enums must be defined before they are used.
43141 <enum id="levels_type" size="4">
43142 <evalue name="low" value="0"/>
43143 <evalue name="high" value="1"/>
43145 <flags id="flags_type" size="4">
43146 <field name="X" start="0"/>
43147 <field name="LEVEL" start="1" end="1" type="levels_type"/>
43149 <reg name="flags" bitsize="32" type="flags_type"/>
43152 Given that description, a value of 3 for the @samp{flags} register
43153 would be printed as:
43156 (gdb) info register flags
43157 flags 0x3 [ X LEVEL=high ]
43160 @node Standard Target Features
43161 @section Standard Target Features
43162 @cindex target descriptions, standard features
43164 A target description must contain either no registers or all the
43165 target's registers. If the description contains no registers, then
43166 @value{GDBN} will assume a default register layout, selected based on
43167 the architecture. If the description contains any registers, the
43168 default layout will not be used; the standard registers must be
43169 described in the target description, in such a way that @value{GDBN}
43170 can recognize them.
43172 This is accomplished by giving specific names to feature elements
43173 which contain standard registers. @value{GDBN} will look for features
43174 with those names and verify that they contain the expected registers;
43175 if any known feature is missing required registers, or if any required
43176 feature is missing, @value{GDBN} will reject the target
43177 description. You can add additional registers to any of the
43178 standard features --- @value{GDBN} will display them just as if
43179 they were added to an unrecognized feature.
43181 This section lists the known features and their expected contents.
43182 Sample XML documents for these features are included in the
43183 @value{GDBN} source tree, in the directory @file{gdb/features}.
43185 Names recognized by @value{GDBN} should include the name of the
43186 company or organization which selected the name, and the overall
43187 architecture to which the feature applies; so e.g.@: the feature
43188 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
43190 The names of registers are not case sensitive for the purpose
43191 of recognizing standard features, but @value{GDBN} will only display
43192 registers using the capitalization used in the description.
43195 * AArch64 Features::
43199 * MicroBlaze Features::
43203 * Nios II Features::
43204 * OpenRISC 1000 Features::
43205 * PowerPC Features::
43206 * RISC-V Features::
43207 * S/390 and System z Features::
43213 @node AArch64 Features
43214 @subsection AArch64 Features
43215 @cindex target descriptions, AArch64 features
43217 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
43218 targets. It should contain registers @samp{x0} through @samp{x30},
43219 @samp{sp}, @samp{pc}, and @samp{cpsr}.
43221 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
43222 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
43225 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
43226 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
43227 through @samp{p15}, @samp{ffr} and @samp{vg}.
43229 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
43230 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
43233 @subsection ARC Features
43234 @cindex target descriptions, ARC Features
43236 ARC processors are highly configurable, so even core registers and their number
43237 are not completely predetermined. In addition flags and PC registers which are
43238 important to @value{GDBN} are not ``core'' registers in ARC. It is required
43239 that one of the core registers features is present.
43240 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
43242 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
43243 targets with a normal register file. It should contain registers @samp{r0}
43244 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
43245 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
43246 and any of extension core registers @samp{r32} through @samp{r59/acch}.
43247 @samp{ilink} and extension core registers are not available to read/write, when
43248 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
43250 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
43251 ARC HS targets with a reduced register file. It should contain registers
43252 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
43253 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
43254 This feature may contain register @samp{ilink} and any of extension core
43255 registers @samp{r32} through @samp{r59/acch}.
43257 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
43258 targets with a normal register file. It should contain registers @samp{r0}
43259 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
43260 @samp{lp_count} and @samp{pcl}. This feature may contain registers
43261 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
43262 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
43263 registers are not available when debugging GNU/Linux applications. The only
43264 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
43265 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
43266 ARC v2, but @samp{ilink2} is optional on ARCompact.
43268 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
43269 targets. It should contain registers @samp{pc} and @samp{status32}.
43272 @subsection ARM Features
43273 @cindex target descriptions, ARM features
43275 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
43277 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
43278 @samp{lr}, @samp{pc}, and @samp{cpsr}.
43280 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
43281 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
43282 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
43285 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
43286 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
43288 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
43289 it should contain at least registers @samp{wR0} through @samp{wR15} and
43290 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
43291 @samp{wCSSF}, and @samp{wCASF} registers are optional.
43293 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
43294 should contain at least registers @samp{d0} through @samp{d15}. If
43295 they are present, @samp{d16} through @samp{d31} should also be included.
43296 @value{GDBN} will synthesize the single-precision registers from
43297 halves of the double-precision registers.
43299 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
43300 need to contain registers; it instructs @value{GDBN} to display the
43301 VFP double-precision registers as vectors and to synthesize the
43302 quad-precision registers from pairs of double-precision registers.
43303 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
43304 be present and include 32 double-precision registers.
43306 @node i386 Features
43307 @subsection i386 Features
43308 @cindex target descriptions, i386 features
43310 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
43311 targets. It should describe the following registers:
43315 @samp{eax} through @samp{edi} plus @samp{eip} for i386
43317 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
43319 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
43320 @samp{fs}, @samp{gs}
43322 @samp{st0} through @samp{st7}
43324 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
43325 @samp{foseg}, @samp{fooff} and @samp{fop}
43328 The register sets may be different, depending on the target.
43330 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
43331 describe registers:
43335 @samp{xmm0} through @samp{xmm7} for i386
43337 @samp{xmm0} through @samp{xmm15} for amd64
43342 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
43343 @samp{org.gnu.gdb.i386.sse} feature. It should
43344 describe the upper 128 bits of @sc{ymm} registers:
43348 @samp{ymm0h} through @samp{ymm7h} for i386
43350 @samp{ymm0h} through @samp{ymm15h} for amd64
43353 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
43354 Memory Protection Extension (MPX). It should describe the following registers:
43358 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
43360 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
43363 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
43364 describe a single register, @samp{orig_eax}.
43366 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
43367 describe two system registers: @samp{fs_base} and @samp{gs_base}.
43369 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
43370 @samp{org.gnu.gdb.i386.avx} feature. It should
43371 describe additional @sc{xmm} registers:
43375 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
43378 It should describe the upper 128 bits of additional @sc{ymm} registers:
43382 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
43386 describe the upper 256 bits of @sc{zmm} registers:
43390 @samp{zmm0h} through @samp{zmm7h} for i386.
43392 @samp{zmm0h} through @samp{zmm15h} for amd64.
43396 describe the additional @sc{zmm} registers:
43400 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
43403 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
43404 describe a single register, @samp{pkru}. It is a 32-bit register
43405 valid for i386 and amd64.
43407 @node MicroBlaze Features
43408 @subsection MicroBlaze Features
43409 @cindex target descriptions, MicroBlaze features
43411 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
43412 targets. It should contain registers @samp{r0} through @samp{r31},
43413 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
43414 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
43415 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
43417 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
43418 If present, it should contain registers @samp{rshr} and @samp{rslr}
43420 @node MIPS Features
43421 @subsection @acronym{MIPS} Features
43422 @cindex target descriptions, @acronym{MIPS} features
43424 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
43425 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
43426 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
43429 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
43430 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
43431 registers. They may be 32-bit or 64-bit depending on the target.
43433 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
43434 it may be optional in a future version of @value{GDBN}. It should
43435 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
43436 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
43438 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
43439 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
43440 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
43441 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
43443 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
43444 contain a single register, @samp{restart}, which is used by the
43445 Linux kernel to control restartable syscalls.
43447 @node M68K Features
43448 @subsection M68K Features
43449 @cindex target descriptions, M68K features
43452 @item @samp{org.gnu.gdb.m68k.core}
43453 @itemx @samp{org.gnu.gdb.coldfire.core}
43454 @itemx @samp{org.gnu.gdb.fido.core}
43455 One of those features must be always present.
43456 The feature that is present determines which flavor of m68k is
43457 used. The feature that is present should contain registers
43458 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
43459 @samp{sp}, @samp{ps} and @samp{pc}.
43461 @item @samp{org.gnu.gdb.coldfire.fp}
43462 This feature is optional. If present, it should contain registers
43463 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
43467 @node NDS32 Features
43468 @subsection NDS32 Features
43469 @cindex target descriptions, NDS32 features
43471 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
43472 targets. It should contain at least registers @samp{r0} through
43473 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
43476 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
43477 it should contain 64-bit double-precision floating-point registers
43478 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
43479 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
43481 @emph{Note:} The first sixteen 64-bit double-precision floating-point
43482 registers are overlapped with the thirty-two 32-bit single-precision
43483 floating-point registers. The 32-bit single-precision registers, if
43484 not being listed explicitly, will be synthesized from halves of the
43485 overlapping 64-bit double-precision registers. Listing 32-bit
43486 single-precision registers explicitly is deprecated, and the
43487 support to it could be totally removed some day.
43489 @node Nios II Features
43490 @subsection Nios II Features
43491 @cindex target descriptions, Nios II features
43493 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
43494 targets. It should contain the 32 core registers (@samp{zero},
43495 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
43496 @samp{pc}, and the 16 control registers (@samp{status} through
43499 @node OpenRISC 1000 Features
43500 @subsection Openrisc 1000 Features
43501 @cindex target descriptions, OpenRISC 1000 features
43503 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
43504 targets. It should contain the 32 general purpose registers (@samp{r0}
43505 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
43507 @node PowerPC Features
43508 @subsection PowerPC Features
43509 @cindex target descriptions, PowerPC features
43511 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
43512 targets. It should contain registers @samp{r0} through @samp{r31},
43513 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
43514 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
43516 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
43517 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
43519 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
43520 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
43521 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
43522 through @samp{v31} as aliases for the corresponding @samp{vrX}
43525 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
43526 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
43527 combine these registers with the floating point registers (@samp{f0}
43528 through @samp{f31}) and the altivec registers (@samp{vr0} through
43529 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
43530 @samp{vs63}, the set of vector-scalar registers for POWER7.
43531 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
43532 @samp{org.gnu.gdb.power.altivec}.
43534 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
43535 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
43536 @samp{spefscr}. SPE targets should provide 32-bit registers in
43537 @samp{org.gnu.gdb.power.core} and provide the upper halves in
43538 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
43539 these to present registers @samp{ev0} through @samp{ev31} to the
43542 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
43543 contain the 64-bit register @samp{ppr}.
43545 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
43546 contain the 64-bit register @samp{dscr}.
43548 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
43549 contain the 64-bit register @samp{tar}.
43551 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
43552 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
43555 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
43556 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
43557 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
43558 server PMU registers provided by @sc{gnu}/Linux.
43560 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
43561 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
43564 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
43565 contain the checkpointed general-purpose registers @samp{cr0} through
43566 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
43567 @samp{cctr}. These registers may all be either 32-bit or 64-bit
43568 depending on the target. It should also contain the checkpointed
43569 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
43572 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
43573 contain the checkpointed 64-bit floating-point registers @samp{cf0}
43574 through @samp{cf31}, as well as the checkpointed 64-bit register
43577 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
43578 should contain the checkpointed altivec registers @samp{cvr0} through
43579 @samp{cvr31}, all 128-bit wide. It should also contain the
43580 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
43583 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
43584 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
43585 will combine these registers with the checkpointed floating point
43586 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
43587 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
43588 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
43589 @samp{cvs63}. Therefore, this feature requires both
43590 @samp{org.gnu.gdb.power.htm.altivec} and
43591 @samp{org.gnu.gdb.power.htm.fpu}.
43593 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
43594 contain the 64-bit checkpointed register @samp{cppr}.
43596 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
43597 contain the 64-bit checkpointed register @samp{cdscr}.
43599 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
43600 contain the 64-bit checkpointed register @samp{ctar}.
43603 @node RISC-V Features
43604 @subsection RISC-V Features
43605 @cindex target descriptions, RISC-V Features
43607 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
43608 targets. It should contain the registers @samp{x0} through
43609 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
43610 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
43613 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
43614 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
43615 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
43616 architectural register names, or the ABI names can be used.
43618 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
43619 it should contain registers that are not backed by real registers on
43620 the target, but are instead virtual, where the register value is
43621 derived from other target state. In many ways these are like
43622 @value{GDBN}s pseudo-registers, except implemented by the target.
43623 Currently the only register expected in this set is the one byte
43624 @samp{priv} register that contains the target's privilege level in the
43625 least significant two bits.
43627 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
43628 should contain all of the target's standard CSRs. Standard CSRs are
43629 those defined in the RISC-V specification documents. There is some
43630 overlap between this feature and the fpu feature; the @samp{fflags},
43631 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
43632 expectation is that these registers will be in the fpu feature if the
43633 target has floating point hardware, but can be moved into the csr
43634 feature if the target has the floating point control registers, but no
43635 other floating point hardware.
43637 @node S/390 and System z Features
43638 @subsection S/390 and System z Features
43639 @cindex target descriptions, S/390 features
43640 @cindex target descriptions, System z features
43642 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
43643 System z targets. It should contain the PSW and the 16 general
43644 registers. In particular, System z targets should provide the 64-bit
43645 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
43646 S/390 targets should provide the 32-bit versions of these registers.
43647 A System z target that runs in 31-bit addressing mode should provide
43648 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
43649 register's upper halves @samp{r0h} through @samp{r15h}, and their
43650 lower halves @samp{r0l} through @samp{r15l}.
43652 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
43653 contain the 64-bit registers @samp{f0} through @samp{f15}, and
43656 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
43657 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
43659 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
43660 contain the register @samp{orig_r2}, which is 64-bit wide on System z
43661 targets and 32-bit otherwise. In addition, the feature may contain
43662 the @samp{last_break} register, whose width depends on the addressing
43663 mode, as well as the @samp{system_call} register, which is always
43666 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
43667 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
43668 @samp{atia}, and @samp{tr0} through @samp{tr15}.
43670 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
43671 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
43672 combined by @value{GDBN} with the floating point registers @samp{f0}
43673 through @samp{f15} to present the 128-bit wide vector registers
43674 @samp{v0} through @samp{v15}. In addition, this feature should
43675 contain the 128-bit wide vector registers @samp{v16} through
43678 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
43679 the 64-bit wide guarded-storage-control registers @samp{gsd},
43680 @samp{gssm}, and @samp{gsepla}.
43682 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
43683 the 64-bit wide guarded-storage broadcast control registers
43684 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
43686 @node Sparc Features
43687 @subsection Sparc Features
43688 @cindex target descriptions, sparc32 features
43689 @cindex target descriptions, sparc64 features
43690 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
43691 targets. It should describe the following registers:
43695 @samp{g0} through @samp{g7}
43697 @samp{o0} through @samp{o7}
43699 @samp{l0} through @samp{l7}
43701 @samp{i0} through @samp{i7}
43704 They may be 32-bit or 64-bit depending on the target.
43706 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
43707 targets. It should describe the following registers:
43711 @samp{f0} through @samp{f31}
43713 @samp{f32} through @samp{f62} for sparc64
43716 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
43717 targets. It should describe the following registers:
43721 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
43722 @samp{fsr}, and @samp{csr} for sparc32
43724 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
43728 @node TIC6x Features
43729 @subsection TMS320C6x Features
43730 @cindex target descriptions, TIC6x features
43731 @cindex target descriptions, TMS320C6x features
43732 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
43733 targets. It should contain registers @samp{A0} through @samp{A15},
43734 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
43736 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
43737 contain registers @samp{A16} through @samp{A31} and @samp{B16}
43738 through @samp{B31}.
43740 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
43741 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
43743 @node Operating System Information
43744 @appendix Operating System Information
43745 @cindex operating system information
43751 Users of @value{GDBN} often wish to obtain information about the state of
43752 the operating system running on the target---for example the list of
43753 processes, or the list of open files. This section describes the
43754 mechanism that makes it possible. This mechanism is similar to the
43755 target features mechanism (@pxref{Target Descriptions}), but focuses
43756 on a different aspect of target.
43758 Operating system information is retrived from the target via the
43759 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
43760 read}). The object name in the request should be @samp{osdata}, and
43761 the @var{annex} identifies the data to be fetched.
43764 @appendixsection Process list
43765 @cindex operating system information, process list
43767 When requesting the process list, the @var{annex} field in the
43768 @samp{qXfer} request should be @samp{processes}. The returned data is
43769 an XML document. The formal syntax of this document is defined in
43770 @file{gdb/features/osdata.dtd}.
43772 An example document is:
43775 <?xml version="1.0"?>
43776 <!DOCTYPE target SYSTEM "osdata.dtd">
43777 <osdata type="processes">
43779 <column name="pid">1</column>
43780 <column name="user">root</column>
43781 <column name="command">/sbin/init</column>
43782 <column name="cores">1,2,3</column>
43787 Each item should include a column whose name is @samp{pid}. The value
43788 of that column should identify the process on the target. The
43789 @samp{user} and @samp{command} columns are optional, and will be
43790 displayed by @value{GDBN}. The @samp{cores} column, if present,
43791 should contain a comma-separated list of cores that this process
43792 is running on. Target may provide additional columns,
43793 which @value{GDBN} currently ignores.
43795 @node Trace File Format
43796 @appendix Trace File Format
43797 @cindex trace file format
43799 The trace file comes in three parts: a header, a textual description
43800 section, and a trace frame section with binary data.
43802 The header has the form @code{\x7fTRACE0\n}. The first byte is
43803 @code{0x7f} so as to indicate that the file contains binary data,
43804 while the @code{0} is a version number that may have different values
43807 The description section consists of multiple lines of @sc{ascii} text
43808 separated by newline characters (@code{0xa}). The lines may include a
43809 variety of optional descriptive or context-setting information, such
43810 as tracepoint definitions or register set size. @value{GDBN} will
43811 ignore any line that it does not recognize. An empty line marks the end
43816 Specifies the size of a register block in bytes. This is equal to the
43817 size of a @code{g} packet payload in the remote protocol. @var{size}
43818 is an ascii decimal number. There should be only one such line in
43819 a single trace file.
43821 @item status @var{status}
43822 Trace status. @var{status} has the same format as a @code{qTStatus}
43823 remote packet reply. There should be only one such line in a single trace
43826 @item tp @var{payload}
43827 Tracepoint definition. The @var{payload} has the same format as
43828 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
43829 may take multiple lines of definition, corresponding to the multiple
43832 @item tsv @var{payload}
43833 Trace state variable definition. The @var{payload} has the same format as
43834 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
43835 may take multiple lines of definition, corresponding to the multiple
43838 @item tdesc @var{payload}
43839 Target description in XML format. The @var{payload} is a single line of
43840 the XML file. All such lines should be concatenated together to get
43841 the original XML file. This file is in the same format as @code{qXfer}
43842 @code{features} payload, and corresponds to the main @code{target.xml}
43843 file. Includes are not allowed.
43847 The trace frame section consists of a number of consecutive frames.
43848 Each frame begins with a two-byte tracepoint number, followed by a
43849 four-byte size giving the amount of data in the frame. The data in
43850 the frame consists of a number of blocks, each introduced by a
43851 character indicating its type (at least register, memory, and trace
43852 state variable). The data in this section is raw binary, not a
43853 hexadecimal or other encoding; its endianness matches the target's
43856 @c FIXME bi-arch may require endianness/arch info in description section
43859 @item R @var{bytes}
43860 Register block. The number and ordering of bytes matches that of a
43861 @code{g} packet in the remote protocol. Note that these are the
43862 actual bytes, in target order, not a hexadecimal encoding.
43864 @item M @var{address} @var{length} @var{bytes}...
43865 Memory block. This is a contiguous block of memory, at the 8-byte
43866 address @var{address}, with a 2-byte length @var{length}, followed by
43867 @var{length} bytes.
43869 @item V @var{number} @var{value}
43870 Trace state variable block. This records the 8-byte signed value
43871 @var{value} of trace state variable numbered @var{number}.
43875 Future enhancements of the trace file format may include additional types
43878 @node Index Section Format
43879 @appendix @code{.gdb_index} section format
43880 @cindex .gdb_index section format
43881 @cindex index section format
43883 This section documents the index section that is created by @code{save
43884 gdb-index} (@pxref{Index Files}). The index section is
43885 DWARF-specific; some knowledge of DWARF is assumed in this
43888 The mapped index file format is designed to be directly
43889 @code{mmap}able on any architecture. In most cases, a datum is
43890 represented using a little-endian 32-bit integer value, called an
43891 @code{offset_type}. Big endian machines must byte-swap the values
43892 before using them. Exceptions to this rule are noted. The data is
43893 laid out such that alignment is always respected.
43895 A mapped index consists of several areas, laid out in order.
43899 The file header. This is a sequence of values, of @code{offset_type}
43900 unless otherwise noted:
43904 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43905 Version 4 uses a different hashing function from versions 5 and 6.
43906 Version 6 includes symbols for inlined functions, whereas versions 4
43907 and 5 do not. Version 7 adds attributes to the CU indices in the
43908 symbol table. Version 8 specifies that symbols from DWARF type units
43909 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43910 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43912 @value{GDBN} will only read version 4, 5, or 6 indices
43913 by specifying @code{set use-deprecated-index-sections on}.
43914 GDB has a workaround for potentially broken version 7 indices so it is
43915 currently not flagged as deprecated.
43918 The offset, from the start of the file, of the CU list.
43921 The offset, from the start of the file, of the types CU list. Note
43922 that this area can be empty, in which case this offset will be equal
43923 to the next offset.
43926 The offset, from the start of the file, of the address area.
43929 The offset, from the start of the file, of the symbol table.
43932 The offset, from the start of the file, of the constant pool.
43936 The CU list. This is a sequence of pairs of 64-bit little-endian
43937 values, sorted by the CU offset. The first element in each pair is
43938 the offset of a CU in the @code{.debug_info} section. The second
43939 element in each pair is the length of that CU. References to a CU
43940 elsewhere in the map are done using a CU index, which is just the
43941 0-based index into this table. Note that if there are type CUs, then
43942 conceptually CUs and type CUs form a single list for the purposes of
43946 The types CU list. This is a sequence of triplets of 64-bit
43947 little-endian values. In a triplet, the first value is the CU offset,
43948 the second value is the type offset in the CU, and the third value is
43949 the type signature. The types CU list is not sorted.
43952 The address area. The address area consists of a sequence of address
43953 entries. Each address entry has three elements:
43957 The low address. This is a 64-bit little-endian value.
43960 The high address. This is a 64-bit little-endian value. Like
43961 @code{DW_AT_high_pc}, the value is one byte beyond the end.
43964 The CU index. This is an @code{offset_type} value.
43968 The symbol table. This is an open-addressed hash table. The size of
43969 the hash table is always a power of 2.
43971 Each slot in the hash table consists of a pair of @code{offset_type}
43972 values. The first value is the offset of the symbol's name in the
43973 constant pool. The second value is the offset of the CU vector in the
43976 If both values are 0, then this slot in the hash table is empty. This
43977 is ok because while 0 is a valid constant pool index, it cannot be a
43978 valid index for both a string and a CU vector.
43980 The hash value for a table entry is computed by applying an
43981 iterative hash function to the symbol's name. Starting with an
43982 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
43983 the string is incorporated into the hash using the formula depending on the
43988 The formula is @code{r = r * 67 + c - 113}.
43990 @item Versions 5 to 7
43991 The formula is @code{r = r * 67 + tolower (c) - 113}.
43994 The terminating @samp{\0} is not incorporated into the hash.
43996 The step size used in the hash table is computed via
43997 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43998 value, and @samp{size} is the size of the hash table. The step size
43999 is used to find the next candidate slot when handling a hash
44002 The names of C@t{++} symbols in the hash table are canonicalized. We
44003 don't currently have a simple description of the canonicalization
44004 algorithm; if you intend to create new index sections, you must read
44008 The constant pool. This is simply a bunch of bytes. It is organized
44009 so that alignment is correct: CU vectors are stored first, followed by
44012 A CU vector in the constant pool is a sequence of @code{offset_type}
44013 values. The first value is the number of CU indices in the vector.
44014 Each subsequent value is the index and symbol attributes of a CU in
44015 the CU list. This element in the hash table is used to indicate which
44016 CUs define the symbol and how the symbol is used.
44017 See below for the format of each CU index+attributes entry.
44019 A string in the constant pool is zero-terminated.
44022 Attributes were added to CU index values in @code{.gdb_index} version 7.
44023 If a symbol has multiple uses within a CU then there is one
44024 CU index+attributes value for each use.
44026 The format of each CU index+attributes entry is as follows
44032 This is the index of the CU in the CU list.
44034 These bits are reserved for future purposes and must be zero.
44036 The kind of the symbol in the CU.
44040 This value is reserved and should not be used.
44041 By reserving zero the full @code{offset_type} value is backwards compatible
44042 with previous versions of the index.
44044 The symbol is a type.
44046 The symbol is a variable or an enum value.
44048 The symbol is a function.
44050 Any other kind of symbol.
44052 These values are reserved.
44056 This bit is zero if the value is global and one if it is static.
44058 The determination of whether a symbol is global or static is complicated.
44059 The authorative reference is the file @file{dwarf2read.c} in
44060 @value{GDBN} sources.
44064 This pseudo-code describes the computation of a symbol's kind and
44065 global/static attributes in the index.
44068 is_external = get_attribute (die, DW_AT_external);
44069 language = get_attribute (cu_die, DW_AT_language);
44072 case DW_TAG_typedef:
44073 case DW_TAG_base_type:
44074 case DW_TAG_subrange_type:
44078 case DW_TAG_enumerator:
44080 is_static = language != CPLUS;
44082 case DW_TAG_subprogram:
44084 is_static = ! (is_external || language == ADA);
44086 case DW_TAG_constant:
44088 is_static = ! is_external;
44090 case DW_TAG_variable:
44092 is_static = ! is_external;
44094 case DW_TAG_namespace:
44098 case DW_TAG_class_type:
44099 case DW_TAG_interface_type:
44100 case DW_TAG_structure_type:
44101 case DW_TAG_union_type:
44102 case DW_TAG_enumeration_type:
44104 is_static = language != CPLUS;
44112 @appendix Manual pages
44116 * gdb man:: The GNU Debugger man page
44117 * gdbserver man:: Remote Server for the GNU Debugger man page
44118 * gcore man:: Generate a core file of a running program
44119 * gdbinit man:: gdbinit scripts
44120 * gdb-add-index man:: Add index files to speed up GDB
44126 @c man title gdb The GNU Debugger
44128 @c man begin SYNOPSIS gdb
44129 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
44130 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
44131 [@option{-b}@w{ }@var{bps}]
44132 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
44133 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
44134 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
44135 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
44136 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
44139 @c man begin DESCRIPTION gdb
44140 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
44141 going on ``inside'' another program while it executes -- or what another
44142 program was doing at the moment it crashed.
44144 @value{GDBN} can do four main kinds of things (plus other things in support of
44145 these) to help you catch bugs in the act:
44149 Start your program, specifying anything that might affect its behavior.
44152 Make your program stop on specified conditions.
44155 Examine what has happened, when your program has stopped.
44158 Change things in your program, so you can experiment with correcting the
44159 effects of one bug and go on to learn about another.
44162 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
44165 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
44166 commands from the terminal until you tell it to exit with the @value{GDBN}
44167 command @code{quit}. You can get online help from @value{GDBN} itself
44168 by using the command @code{help}.
44170 You can run @code{gdb} with no arguments or options; but the most
44171 usual way to start @value{GDBN} is with one argument or two, specifying an
44172 executable program as the argument:
44178 You can also start with both an executable program and a core file specified:
44184 You can, instead, specify a process ID as a second argument, if you want
44185 to debug a running process:
44193 would attach @value{GDBN} to process @code{1234} (unless you also have a file
44194 named @file{1234}; @value{GDBN} does check for a core file first).
44195 With option @option{-p} you can omit the @var{program} filename.
44197 Here are some of the most frequently needed @value{GDBN} commands:
44199 @c pod2man highlights the right hand side of the @item lines.
44201 @item break [@var{file}:]@var{function}
44202 Set a breakpoint at @var{function} (in @var{file}).
44204 @item run [@var{arglist}]
44205 Start your program (with @var{arglist}, if specified).
44208 Backtrace: display the program stack.
44210 @item print @var{expr}
44211 Display the value of an expression.
44214 Continue running your program (after stopping, e.g. at a breakpoint).
44217 Execute next program line (after stopping); step @emph{over} any
44218 function calls in the line.
44220 @item edit [@var{file}:]@var{function}
44221 look at the program line where it is presently stopped.
44223 @item list [@var{file}:]@var{function}
44224 type the text of the program in the vicinity of where it is presently stopped.
44227 Execute next program line (after stopping); step @emph{into} any
44228 function calls in the line.
44230 @item help [@var{name}]
44231 Show information about @value{GDBN} command @var{name}, or general information
44232 about using @value{GDBN}.
44235 Exit from @value{GDBN}.
44239 For full details on @value{GDBN},
44240 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44241 by Richard M. Stallman and Roland H. Pesch. The same text is available online
44242 as the @code{gdb} entry in the @code{info} program.
44246 @c man begin OPTIONS gdb
44247 Any arguments other than options specify an executable
44248 file and core file (or process ID); that is, the first argument
44249 encountered with no
44250 associated option flag is equivalent to a @option{-se} option, and the second,
44251 if any, is equivalent to a @option{-c} option if it's the name of a file.
44253 both long and short forms; both are shown here. The long forms are also
44254 recognized if you truncate them, so long as enough of the option is
44255 present to be unambiguous. (If you prefer, you can flag option
44256 arguments with @option{+} rather than @option{-}, though we illustrate the
44257 more usual convention.)
44259 All the options and command line arguments you give are processed
44260 in sequential order. The order makes a difference when the @option{-x}
44266 List all options, with brief explanations.
44268 @item -symbols=@var{file}
44269 @itemx -s @var{file}
44270 Read symbol table from file @var{file}.
44273 Enable writing into executable and core files.
44275 @item -exec=@var{file}
44276 @itemx -e @var{file}
44277 Use file @var{file} as the executable file to execute when
44278 appropriate, and for examining pure data in conjunction with a core
44281 @item -se=@var{file}
44282 Read symbol table from file @var{file} and use it as the executable
44285 @item -core=@var{file}
44286 @itemx -c @var{file}
44287 Use file @var{file} as a core dump to examine.
44289 @item -command=@var{file}
44290 @itemx -x @var{file}
44291 Execute @value{GDBN} commands from file @var{file}.
44293 @item -ex @var{command}
44294 Execute given @value{GDBN} @var{command}.
44296 @item -directory=@var{directory}
44297 @itemx -d @var{directory}
44298 Add @var{directory} to the path to search for source files.
44301 Do not execute commands from @file{~/.gdbinit}.
44305 Do not execute commands from any @file{.gdbinit} initialization files.
44309 ``Quiet''. Do not print the introductory and copyright messages. These
44310 messages are also suppressed in batch mode.
44313 Run in batch mode. Exit with status @code{0} after processing all the command
44314 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
44315 Exit with nonzero status if an error occurs in executing the @value{GDBN}
44316 commands in the command files.
44318 Batch mode may be useful for running @value{GDBN} as a filter, for example to
44319 download and run a program on another computer; in order to make this
44320 more useful, the message
44323 Program exited normally.
44327 (which is ordinarily issued whenever a program running under @value{GDBN} control
44328 terminates) is not issued when running in batch mode.
44330 @item -cd=@var{directory}
44331 Run @value{GDBN} using @var{directory} as its working directory,
44332 instead of the current directory.
44336 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
44337 @value{GDBN} to output the full file name and line number in a standard,
44338 recognizable fashion each time a stack frame is displayed (which
44339 includes each time the program stops). This recognizable format looks
44340 like two @samp{\032} characters, followed by the file name, line number
44341 and character position separated by colons, and a newline. The
44342 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
44343 characters as a signal to display the source code for the frame.
44346 Set the line speed (baud rate or bits per second) of any serial
44347 interface used by @value{GDBN} for remote debugging.
44349 @item -tty=@var{device}
44350 Run using @var{device} for your program's standard input and output.
44354 @c man begin SEEALSO gdb
44356 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44357 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44358 documentation are properly installed at your site, the command
44365 should give you access to the complete manual.
44367 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44368 Richard M. Stallman and Roland H. Pesch, July 1991.
44372 @node gdbserver man
44373 @heading gdbserver man
44375 @c man title gdbserver Remote Server for the GNU Debugger
44377 @c man begin SYNOPSIS gdbserver
44378 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44380 gdbserver --attach @var{comm} @var{pid}
44382 gdbserver --multi @var{comm}
44386 @c man begin DESCRIPTION gdbserver
44387 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
44388 than the one which is running the program being debugged.
44391 @subheading Usage (server (target) side)
44394 Usage (server (target) side):
44397 First, you need to have a copy of the program you want to debug put onto
44398 the target system. The program can be stripped to save space if needed, as
44399 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
44400 the @value{GDBN} running on the host system.
44402 To use the server, you log on to the target system, and run the @command{gdbserver}
44403 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
44404 your program, and (c) its arguments. The general syntax is:
44407 target> gdbserver @var{comm} @var{program} [@var{args} ...]
44410 For example, using a serial port, you might say:
44414 @c @file would wrap it as F</dev/com1>.
44415 target> gdbserver /dev/com1 emacs foo.txt
44418 target> gdbserver @file{/dev/com1} emacs foo.txt
44422 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
44423 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
44424 waits patiently for the host @value{GDBN} to communicate with it.
44426 To use a TCP connection, you could say:
44429 target> gdbserver host:2345 emacs foo.txt
44432 This says pretty much the same thing as the last example, except that we are
44433 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
44434 that we are expecting to see a TCP connection from @code{host} to local TCP port
44435 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
44436 want for the port number as long as it does not conflict with any existing TCP
44437 ports on the target system. This same port number must be used in the host
44438 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
44439 you chose a port number that conflicts with another service, @command{gdbserver} will
44440 print an error message and exit.
44442 @command{gdbserver} can also attach to running programs.
44443 This is accomplished via the @option{--attach} argument. The syntax is:
44446 target> gdbserver --attach @var{comm} @var{pid}
44449 @var{pid} is the process ID of a currently running process. It isn't
44450 necessary to point @command{gdbserver} at a binary for the running process.
44452 To start @code{gdbserver} without supplying an initial command to run
44453 or process ID to attach, use the @option{--multi} command line option.
44454 In such case you should connect using @kbd{target extended-remote} to start
44455 the program you want to debug.
44458 target> gdbserver --multi @var{comm}
44462 @subheading Usage (host side)
44468 You need an unstripped copy of the target program on your host system, since
44469 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
44470 would, with the target program as the first argument. (You may need to use the
44471 @option{--baud} option if the serial line is running at anything except 9600 baud.)
44472 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
44473 new command you need to know about is @code{target remote}
44474 (or @code{target extended-remote}). Its argument is either
44475 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
44476 descriptor. For example:
44480 @c @file would wrap it as F</dev/ttyb>.
44481 (gdb) target remote /dev/ttyb
44484 (gdb) target remote @file{/dev/ttyb}
44489 communicates with the server via serial line @file{/dev/ttyb}, and:
44492 (gdb) target remote the-target:2345
44496 communicates via a TCP connection to port 2345 on host `the-target', where
44497 you previously started up @command{gdbserver} with the same port number. Note that for
44498 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
44499 command, otherwise you may get an error that looks something like
44500 `Connection refused'.
44502 @command{gdbserver} can also debug multiple inferiors at once,
44505 the @value{GDBN} manual in node @code{Inferiors and Programs}
44506 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
44509 @ref{Inferiors and Programs}.
44511 In such case use the @code{extended-remote} @value{GDBN} command variant:
44514 (gdb) target extended-remote the-target:2345
44517 The @command{gdbserver} option @option{--multi} may or may not be used in such
44521 @c man begin OPTIONS gdbserver
44522 There are three different modes for invoking @command{gdbserver}:
44527 Debug a specific program specified by its program name:
44530 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44533 The @var{comm} parameter specifies how should the server communicate
44534 with @value{GDBN}; it is either a device name (to use a serial line),
44535 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
44536 stdin/stdout of @code{gdbserver}. Specify the name of the program to
44537 debug in @var{prog}. Any remaining arguments will be passed to the
44538 program verbatim. When the program exits, @value{GDBN} will close the
44539 connection, and @code{gdbserver} will exit.
44542 Debug a specific program by specifying the process ID of a running
44546 gdbserver --attach @var{comm} @var{pid}
44549 The @var{comm} parameter is as described above. Supply the process ID
44550 of a running program in @var{pid}; @value{GDBN} will do everything
44551 else. Like with the previous mode, when the process @var{pid} exits,
44552 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
44555 Multi-process mode -- debug more than one program/process:
44558 gdbserver --multi @var{comm}
44561 In this mode, @value{GDBN} can instruct @command{gdbserver} which
44562 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
44563 close the connection when a process being debugged exits, so you can
44564 debug several processes in the same session.
44567 In each of the modes you may specify these options:
44572 List all options, with brief explanations.
44575 This option causes @command{gdbserver} to print its version number and exit.
44578 @command{gdbserver} will attach to a running program. The syntax is:
44581 target> gdbserver --attach @var{comm} @var{pid}
44584 @var{pid} is the process ID of a currently running process. It isn't
44585 necessary to point @command{gdbserver} at a binary for the running process.
44588 To start @code{gdbserver} without supplying an initial command to run
44589 or process ID to attach, use this command line option.
44590 Then you can connect using @kbd{target extended-remote} and start
44591 the program you want to debug. The syntax is:
44594 target> gdbserver --multi @var{comm}
44598 Instruct @code{gdbserver} to display extra status information about the debugging
44600 This option is intended for @code{gdbserver} development and for bug reports to
44603 @item --remote-debug
44604 Instruct @code{gdbserver} to display remote protocol debug output.
44605 This option is intended for @code{gdbserver} development and for bug reports to
44608 @item --debug-file=@var{filename}
44609 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
44610 This option is intended for @code{gdbserver} development and for bug reports to
44613 @item --debug-format=option1@r{[},option2,...@r{]}
44614 Instruct @code{gdbserver} to include extra information in each line
44615 of debugging output.
44616 @xref{Other Command-Line Arguments for gdbserver}.
44619 Specify a wrapper to launch programs
44620 for debugging. The option should be followed by the name of the
44621 wrapper, then any command-line arguments to pass to the wrapper, then
44622 @kbd{--} indicating the end of the wrapper arguments.
44625 By default, @command{gdbserver} keeps the listening TCP port open, so that
44626 additional connections are possible. However, if you start @code{gdbserver}
44627 with the @option{--once} option, it will stop listening for any further
44628 connection attempts after connecting to the first @value{GDBN} session.
44630 @c --disable-packet is not documented for users.
44632 @c --disable-randomization and --no-disable-randomization are superseded by
44633 @c QDisableRandomization.
44638 @c man begin SEEALSO gdbserver
44640 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44641 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44642 documentation are properly installed at your site, the command
44648 should give you access to the complete manual.
44650 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44651 Richard M. Stallman and Roland H. Pesch, July 1991.
44658 @c man title gcore Generate a core file of a running program
44661 @c man begin SYNOPSIS gcore
44662 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
44666 @c man begin DESCRIPTION gcore
44667 Generate core dumps of one or more running programs with process IDs
44668 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
44669 is equivalent to one produced by the kernel when the process crashes
44670 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
44671 limit). However, unlike after a crash, after @command{gcore} finishes
44672 its job the program remains running without any change.
44675 @c man begin OPTIONS gcore
44678 Dump all memory mappings. The actual effect of this option depends on
44679 the Operating System. On @sc{gnu}/Linux, it will disable
44680 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
44681 enable @code{dump-excluded-mappings} (@pxref{set
44682 dump-excluded-mappings}).
44684 @item -o @var{prefix}
44685 The optional argument @var{prefix} specifies the prefix to be used
44686 when composing the file names of the core dumps. The file name is
44687 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
44688 process ID of the running program being analyzed by @command{gcore}.
44689 If not specified, @var{prefix} defaults to @var{gcore}.
44693 @c man begin SEEALSO gcore
44695 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44696 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44697 documentation are properly installed at your site, the command
44704 should give you access to the complete manual.
44706 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44707 Richard M. Stallman and Roland H. Pesch, July 1991.
44714 @c man title gdbinit GDB initialization scripts
44717 @c man begin SYNOPSIS gdbinit
44718 @ifset SYSTEM_GDBINIT
44719 @value{SYSTEM_GDBINIT}
44728 @c man begin DESCRIPTION gdbinit
44729 These files contain @value{GDBN} commands to automatically execute during
44730 @value{GDBN} startup. The lines of contents are canned sequences of commands,
44733 the @value{GDBN} manual in node @code{Sequences}
44734 -- shell command @code{info -f gdb -n Sequences}.
44740 Please read more in
44742 the @value{GDBN} manual in node @code{Startup}
44743 -- shell command @code{info -f gdb -n Startup}.
44750 @ifset SYSTEM_GDBINIT
44751 @item @value{SYSTEM_GDBINIT}
44753 @ifclear SYSTEM_GDBINIT
44754 @item (not enabled with @code{--with-system-gdbinit} during compilation)
44756 System-wide initialization file. It is executed unless user specified
44757 @value{GDBN} option @code{-nx} or @code{-n}.
44760 the @value{GDBN} manual in node @code{System-wide configuration}
44761 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
44764 @ref{System-wide configuration}.
44768 User initialization file. It is executed unless user specified
44769 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
44772 Initialization file for current directory. It may need to be enabled with
44773 @value{GDBN} security command @code{set auto-load local-gdbinit}.
44776 the @value{GDBN} manual in node @code{Init File in the Current Directory}
44777 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
44780 @ref{Init File in the Current Directory}.
44785 @c man begin SEEALSO gdbinit
44787 gdb(1), @code{info -f gdb -n Startup}
44789 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44790 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44791 documentation are properly installed at your site, the command
44797 should give you access to the complete manual.
44799 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44800 Richard M. Stallman and Roland H. Pesch, July 1991.
44804 @node gdb-add-index man
44805 @heading gdb-add-index
44806 @pindex gdb-add-index
44807 @anchor{gdb-add-index}
44809 @c man title gdb-add-index Add index files to speed up GDB
44811 @c man begin SYNOPSIS gdb-add-index
44812 gdb-add-index @var{filename}
44815 @c man begin DESCRIPTION gdb-add-index
44816 When @value{GDBN} finds a symbol file, it scans the symbols in the
44817 file in order to construct an internal symbol table. This lets most
44818 @value{GDBN} operations work quickly--at the cost of a delay early on.
44819 For large programs, this delay can be quite lengthy, so @value{GDBN}
44820 provides a way to build an index, which speeds up startup.
44822 To determine whether a file contains such an index, use the command
44823 @kbd{readelf -S filename}: the index is stored in a section named
44824 @code{.gdb_index}. The index file can only be produced on systems
44825 which use ELF binaries and DWARF debug information (i.e., sections
44826 named @code{.debug_*}).
44828 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
44829 in the @env{PATH} environment variable. If you want to use different
44830 versions of these programs, you can specify them through the
44831 @env{GDB} and @env{OBJDUMP} environment variables.
44835 the @value{GDBN} manual in node @code{Index Files}
44836 -- shell command @kbd{info -f gdb -n "Index Files"}.
44843 @c man begin SEEALSO gdb-add-index
44845 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44846 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44847 documentation are properly installed at your site, the command
44853 should give you access to the complete manual.
44855 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44856 Richard M. Stallman and Roland H. Pesch, July 1991.
44862 @node GNU Free Documentation License
44863 @appendix GNU Free Documentation License
44866 @node Concept Index
44867 @unnumbered Concept Index
44871 @node Command and Variable Index
44872 @unnumbered Command, Variable, and Function Index
44877 % I think something like @@colophon should be in texinfo. In the
44879 \long\def\colophon{\hbox to0pt{}\vfill
44880 \centerline{The body of this manual is set in}
44881 \centerline{\fontname\tenrm,}
44882 \centerline{with headings in {\bf\fontname\tenbf}}
44883 \centerline{and examples in {\tt\fontname\tentt}.}
44884 \centerline{{\it\fontname\tenit\/},}
44885 \centerline{{\bf\fontname\tenbf}, and}
44886 \centerline{{\sl\fontname\tensl\/}}
44887 \centerline{are used for emphasis.}\vfill}
44889 % Blame: doc@@cygnus.com, 1991.