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 If you are debugging in a target environment that supports
6701 reverse execution, @value{GDBN} provides the following commands.
6704 @kindex reverse-continue
6705 @kindex rc @r{(@code{reverse-continue})}
6706 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6707 @itemx rc @r{[}@var{ignore-count}@r{]}
6708 Beginning at the point where your program last stopped, start executing
6709 in reverse. Reverse execution will stop for breakpoints and synchronous
6710 exceptions (signals), just like normal execution. Behavior of
6711 asynchronous signals depends on the target environment.
6713 @kindex reverse-step
6714 @kindex rs @r{(@code{step})}
6715 @item reverse-step @r{[}@var{count}@r{]}
6716 Run the program backward until control reaches the start of a
6717 different source line; then stop it, and return control to @value{GDBN}.
6719 Like the @code{step} command, @code{reverse-step} will only stop
6720 at the beginning of a source line. It ``un-executes'' the previously
6721 executed source line. If the previous source line included calls to
6722 debuggable functions, @code{reverse-step} will step (backward) into
6723 the called function, stopping at the beginning of the @emph{last}
6724 statement in the called function (typically a return statement).
6726 Also, as with the @code{step} command, if non-debuggable functions are
6727 called, @code{reverse-step} will run thru them backward without stopping.
6729 @kindex reverse-stepi
6730 @kindex rsi @r{(@code{reverse-stepi})}
6731 @item reverse-stepi @r{[}@var{count}@r{]}
6732 Reverse-execute one machine instruction. Note that the instruction
6733 to be reverse-executed is @emph{not} the one pointed to by the program
6734 counter, but the instruction executed prior to that one. For instance,
6735 if the last instruction was a jump, @code{reverse-stepi} will take you
6736 back from the destination of the jump to the jump instruction itself.
6738 @kindex reverse-next
6739 @kindex rn @r{(@code{reverse-next})}
6740 @item reverse-next @r{[}@var{count}@r{]}
6741 Run backward to the beginning of the previous line executed in
6742 the current (innermost) stack frame. If the line contains function
6743 calls, they will be ``un-executed'' without stopping. Starting from
6744 the first line of a function, @code{reverse-next} will take you back
6745 to the caller of that function, @emph{before} the function was called,
6746 just as the normal @code{next} command would take you from the last
6747 line of a function back to its return to its caller
6748 @footnote{Unless the code is too heavily optimized.}.
6750 @kindex reverse-nexti
6751 @kindex rni @r{(@code{reverse-nexti})}
6752 @item reverse-nexti @r{[}@var{count}@r{]}
6753 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6754 in reverse, except that called functions are ``un-executed'' atomically.
6755 That is, if the previously executed instruction was a return from
6756 another function, @code{reverse-nexti} will continue to execute
6757 in reverse until the call to that function (from the current stack
6760 @kindex reverse-finish
6761 @item reverse-finish
6762 Just as the @code{finish} command takes you to the point where the
6763 current function returns, @code{reverse-finish} takes you to the point
6764 where it was called. Instead of ending up at the end of the current
6765 function invocation, you end up at the beginning.
6767 @kindex set exec-direction
6768 @item set exec-direction
6769 Set the direction of target execution.
6770 @item set exec-direction reverse
6771 @cindex execute forward or backward in time
6772 @value{GDBN} will perform all execution commands in reverse, until the
6773 exec-direction mode is changed to ``forward''. Affected commands include
6774 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6775 command cannot be used in reverse mode.
6776 @item set exec-direction forward
6777 @value{GDBN} will perform all execution commands in the normal fashion.
6778 This is the default.
6782 @node Process Record and Replay
6783 @chapter Recording Inferior's Execution and Replaying It
6784 @cindex process record and replay
6785 @cindex recording inferior's execution and replaying it
6787 On some platforms, @value{GDBN} provides a special @dfn{process record
6788 and replay} target that can record a log of the process execution, and
6789 replay it later with both forward and reverse execution commands.
6792 When this target is in use, if the execution log includes the record
6793 for the next instruction, @value{GDBN} will debug in @dfn{replay
6794 mode}. In the replay mode, the inferior does not really execute code
6795 instructions. Instead, all the events that normally happen during
6796 code execution are taken from the execution log. While code is not
6797 really executed in replay mode, the values of registers (including the
6798 program counter register) and the memory of the inferior are still
6799 changed as they normally would. Their contents are taken from the
6803 If the record for the next instruction is not in the execution log,
6804 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6805 inferior executes normally, and @value{GDBN} records the execution log
6808 The process record and replay target supports reverse execution
6809 (@pxref{Reverse Execution}), even if the platform on which the
6810 inferior runs does not. However, the reverse execution is limited in
6811 this case by the range of the instructions recorded in the execution
6812 log. In other words, reverse execution on platforms that don't
6813 support it directly can only be done in the replay mode.
6815 When debugging in the reverse direction, @value{GDBN} will work in
6816 replay mode as long as the execution log includes the record for the
6817 previous instruction; otherwise, it will work in record mode, if the
6818 platform supports reverse execution, or stop if not.
6820 For architecture environments that support process record and replay,
6821 @value{GDBN} provides the following commands:
6824 @kindex target record
6825 @kindex target record-full
6826 @kindex target record-btrace
6829 @kindex record btrace
6830 @kindex record btrace bts
6831 @kindex record btrace pt
6837 @kindex rec btrace bts
6838 @kindex rec btrace pt
6841 @item record @var{method}
6842 This command starts the process record and replay target. The
6843 recording method can be specified as parameter. Without a parameter
6844 the command uses the @code{full} recording method. The following
6845 recording methods are available:
6849 Full record/replay recording using @value{GDBN}'s software record and
6850 replay implementation. This method allows replaying and reverse
6853 @item btrace @var{format}
6854 Hardware-supported instruction recording. This method does not record
6855 data. Further, the data is collected in a ring buffer so old data will
6856 be overwritten when the buffer is full. It allows limited reverse
6857 execution. Variables and registers are not available during reverse
6858 execution. In remote debugging, recording continues on disconnect.
6859 Recorded data can be inspected after reconnecting. The recording may
6860 be stopped using @code{record stop}.
6862 The recording format can be specified as parameter. Without a parameter
6863 the command chooses the recording format. The following recording
6864 formats are available:
6868 @cindex branch trace store
6869 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6870 this format, the processor stores a from/to record for each executed
6871 branch in the btrace ring buffer.
6874 @cindex Intel Processor Trace
6875 Use the @dfn{Intel Processor Trace} recording format. In this
6876 format, the processor stores the execution trace in a compressed form
6877 that is afterwards decoded by @value{GDBN}.
6879 The trace can be recorded with very low overhead. The compressed
6880 trace format also allows small trace buffers to already contain a big
6881 number of instructions compared to @acronym{BTS}.
6883 Decoding the recorded execution trace, on the other hand, is more
6884 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6885 increased number of instructions to process. You should increase the
6886 buffer-size with care.
6889 Not all recording formats may be available on all processors.
6892 The process record and replay target can only debug a process that is
6893 already running. Therefore, you need first to start the process with
6894 the @kbd{run} or @kbd{start} commands, and then start the recording
6895 with the @kbd{record @var{method}} command.
6897 @cindex displaced stepping, and process record and replay
6898 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6899 will be automatically disabled when process record and replay target
6900 is started. That's because the process record and replay target
6901 doesn't support displaced stepping.
6903 @cindex non-stop mode, and process record and replay
6904 @cindex asynchronous execution, and process record and replay
6905 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6906 the asynchronous execution mode (@pxref{Background Execution}), not
6907 all recording methods are available. The @code{full} recording method
6908 does not support these two modes.
6913 Stop the process record and replay target. When process record and
6914 replay target stops, the entire execution log will be deleted and the
6915 inferior will either be terminated, or will remain in its final state.
6917 When you stop the process record and replay target in record mode (at
6918 the end of the execution log), the inferior will be stopped at the
6919 next instruction that would have been recorded. In other words, if
6920 you record for a while and then stop recording, the inferior process
6921 will be left in the same state as if the recording never happened.
6923 On the other hand, if the process record and replay target is stopped
6924 while in replay mode (that is, not at the end of the execution log,
6925 but at some earlier point), the inferior process will become ``live''
6926 at that earlier state, and it will then be possible to continue the
6927 usual ``live'' debugging of the process from that state.
6929 When the inferior process exits, or @value{GDBN} detaches from it,
6930 process record and replay target will automatically stop itself.
6934 Go to a specific location in the execution log. There are several
6935 ways to specify the location to go to:
6938 @item record goto begin
6939 @itemx record goto start
6940 Go to the beginning of the execution log.
6942 @item record goto end
6943 Go to the end of the execution log.
6945 @item record goto @var{n}
6946 Go to instruction number @var{n} in the execution log.
6950 @item record save @var{filename}
6951 Save the execution log to a file @file{@var{filename}}.
6952 Default filename is @file{gdb_record.@var{process_id}}, where
6953 @var{process_id} is the process ID of the inferior.
6955 This command may not be available for all recording methods.
6957 @kindex record restore
6958 @item record restore @var{filename}
6959 Restore the execution log from a file @file{@var{filename}}.
6960 File must have been created with @code{record save}.
6962 @kindex set record full
6963 @item set record full insn-number-max @var{limit}
6964 @itemx set record full insn-number-max unlimited
6965 Set the limit of instructions to be recorded for the @code{full}
6966 recording method. Default value is 200000.
6968 If @var{limit} is a positive number, then @value{GDBN} will start
6969 deleting instructions from the log once the number of the record
6970 instructions becomes greater than @var{limit}. For every new recorded
6971 instruction, @value{GDBN} will delete the earliest recorded
6972 instruction to keep the number of recorded instructions at the limit.
6973 (Since deleting recorded instructions loses information, @value{GDBN}
6974 lets you control what happens when the limit is reached, by means of
6975 the @code{stop-at-limit} option, described below.)
6977 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6978 delete recorded instructions from the execution log. The number of
6979 recorded instructions is limited only by the available memory.
6981 @kindex show record full
6982 @item show record full insn-number-max
6983 Show the limit of instructions to be recorded with the @code{full}
6986 @item set record full stop-at-limit
6987 Control the behavior of the @code{full} recording method when the
6988 number of recorded instructions reaches the limit. If ON (the
6989 default), @value{GDBN} will stop when the limit is reached for the
6990 first time and ask you whether you want to stop the inferior or
6991 continue running it and recording the execution log. If you decide
6992 to continue recording, each new recorded instruction will cause the
6993 oldest one to be deleted.
6995 If this option is OFF, @value{GDBN} will automatically delete the
6996 oldest record to make room for each new one, without asking.
6998 @item show record full stop-at-limit
6999 Show the current setting of @code{stop-at-limit}.
7001 @item set record full memory-query
7002 Control the behavior when @value{GDBN} is unable to record memory
7003 changes caused by an instruction for the @code{full} recording method.
7004 If ON, @value{GDBN} will query whether to stop the inferior in that
7007 If this option is OFF (the default), @value{GDBN} will automatically
7008 ignore the effect of such instructions on memory. Later, when
7009 @value{GDBN} replays this execution log, it will mark the log of this
7010 instruction as not accessible, and it will not affect the replay
7013 @item show record full memory-query
7014 Show the current setting of @code{memory-query}.
7016 @kindex set record btrace
7017 The @code{btrace} record target does not trace data. As a
7018 convenience, when replaying, @value{GDBN} reads read-only memory off
7019 the live program directly, assuming that the addresses of the
7020 read-only areas don't change. This for example makes it possible to
7021 disassemble code while replaying, but not to print variables.
7022 In some cases, being able to inspect variables might be useful.
7023 You can use the following command for that:
7025 @item set record btrace replay-memory-access
7026 Control the behavior of the @code{btrace} recording method when
7027 accessing memory during replay. If @code{read-only} (the default),
7028 @value{GDBN} will only allow accesses to read-only memory.
7029 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7030 and to read-write memory. Beware that the accessed memory corresponds
7031 to the live target and not necessarily to the current replay
7034 @item set record btrace cpu @var{identifier}
7035 Set the processor to be used for enabling workarounds for processor
7036 errata when decoding the trace.
7038 Processor errata are defects in processor operation, caused by its
7039 design or manufacture. They can cause a trace not to match the
7040 specification. This, in turn, may cause trace decode to fail.
7041 @value{GDBN} can detect erroneous trace packets and correct them, thus
7042 avoiding the decoding failures. These corrections are known as
7043 @dfn{errata workarounds}, and are enabled based on the processor on
7044 which the trace was recorded.
7046 By default, @value{GDBN} attempts to detect the processor
7047 automatically, and apply the necessary workarounds for it. However,
7048 you may need to specify the processor if @value{GDBN} does not yet
7049 support it. This command allows you to do that, and also allows to
7050 disable the workarounds.
7052 The argument @var{identifier} identifies the @sc{cpu} and is of the
7053 form: @code{@var{vendor}:@var{procesor identifier}}. In addition,
7054 there are two special identifiers, @code{none} and @code{auto}
7057 The following vendor identifiers and corresponding processor
7058 identifiers are currently supported:
7060 @multitable @columnfractions .1 .9
7063 @tab @var{family}/@var{model}[/@var{stepping}]
7067 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7068 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7070 If @var{identifier} is @code{auto}, enable errata workarounds for the
7071 processor on which the trace was recorded. If @var{identifier} is
7072 @code{none}, errata workarounds are disabled.
7074 For example, when using an old @value{GDBN} on a new system, decode
7075 may fail because @value{GDBN} does not support the new processor. It
7076 often suffices to specify an older processor that @value{GDBN}
7081 Active record target: record-btrace
7082 Recording format: Intel Processor Trace.
7084 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7085 (gdb) set record btrace cpu intel:6/158
7087 Active record target: record-btrace
7088 Recording format: Intel Processor Trace.
7090 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7093 @kindex show record btrace
7094 @item show record btrace replay-memory-access
7095 Show the current setting of @code{replay-memory-access}.
7097 @item show record btrace cpu
7098 Show the processor to be used for enabling trace decode errata
7101 @kindex set record btrace bts
7102 @item set record btrace bts buffer-size @var{size}
7103 @itemx set record btrace bts buffer-size unlimited
7104 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7105 format. Default is 64KB.
7107 If @var{size} is a positive number, then @value{GDBN} will try to
7108 allocate a buffer of at least @var{size} bytes for each new thread
7109 that uses the btrace recording method and the @acronym{BTS} format.
7110 The actually obtained buffer size may differ from the requested
7111 @var{size}. Use the @code{info record} command to see the actual
7112 buffer size for each thread that uses the btrace recording method and
7113 the @acronym{BTS} format.
7115 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7116 allocate a buffer of 4MB.
7118 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7119 also need longer to process the branch trace data before it can be used.
7121 @item show record btrace bts buffer-size @var{size}
7122 Show the current setting of the requested ring buffer size for branch
7123 tracing in @acronym{BTS} format.
7125 @kindex set record btrace pt
7126 @item set record btrace pt buffer-size @var{size}
7127 @itemx set record btrace pt buffer-size unlimited
7128 Set the requested ring buffer size for branch tracing in Intel
7129 Processor Trace format. Default is 16KB.
7131 If @var{size} is a positive number, then @value{GDBN} will try to
7132 allocate a buffer of at least @var{size} bytes for each new thread
7133 that uses the btrace recording method and the Intel Processor Trace
7134 format. The actually obtained buffer size may differ from the
7135 requested @var{size}. Use the @code{info record} command to see the
7136 actual buffer size for each thread.
7138 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7139 allocate a buffer of 4MB.
7141 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7142 also need longer to process the branch trace data before it can be used.
7144 @item show record btrace pt buffer-size @var{size}
7145 Show the current setting of the requested ring buffer size for branch
7146 tracing in Intel Processor Trace format.
7150 Show various statistics about the recording depending on the recording
7155 For the @code{full} recording method, it shows the state of process
7156 record and its in-memory execution log buffer, including:
7160 Whether in record mode or replay mode.
7162 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7164 Highest recorded instruction number.
7166 Current instruction about to be replayed (if in replay mode).
7168 Number of instructions contained in the execution log.
7170 Maximum number of instructions that may be contained in the execution log.
7174 For the @code{btrace} recording method, it shows:
7180 Number of instructions that have been recorded.
7182 Number of blocks of sequential control-flow formed by the recorded
7185 Whether in record mode or replay mode.
7188 For the @code{bts} recording format, it also shows:
7191 Size of the perf ring buffer.
7194 For the @code{pt} recording format, it also shows:
7197 Size of the perf ring buffer.
7201 @kindex record delete
7204 When record target runs in replay mode (``in the past''), delete the
7205 subsequent execution log and begin to record a new execution log starting
7206 from the current address. This means you will abandon the previously
7207 recorded ``future'' and begin recording a new ``future''.
7209 @kindex record instruction-history
7210 @kindex rec instruction-history
7211 @item record instruction-history
7212 Disassembles instructions from the recorded execution log. By
7213 default, ten instructions are disassembled. This can be changed using
7214 the @code{set record instruction-history-size} command. Instructions
7215 are printed in execution order.
7217 It can also print mixed source+disassembly if you specify the the
7218 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7219 as well as in symbolic form by specifying the @code{/r} modifier.
7221 The current position marker is printed for the instruction at the
7222 current program counter value. This instruction can appear multiple
7223 times in the trace and the current position marker will be printed
7224 every time. To omit the current position marker, specify the
7227 To better align the printed instructions when the trace contains
7228 instructions from more than one function, the function name may be
7229 omitted by specifying the @code{/f} modifier.
7231 Speculatively executed instructions are prefixed with @samp{?}. This
7232 feature is not available for all recording formats.
7234 There are several ways to specify what part of the execution log to
7238 @item record instruction-history @var{insn}
7239 Disassembles ten instructions starting from instruction number
7242 @item record instruction-history @var{insn}, +/-@var{n}
7243 Disassembles @var{n} instructions around instruction number
7244 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7245 @var{n} instructions after instruction number @var{insn}. If
7246 @var{n} is preceded with @code{-}, disassembles @var{n}
7247 instructions before instruction number @var{insn}.
7249 @item record instruction-history
7250 Disassembles ten more instructions after the last disassembly.
7252 @item record instruction-history -
7253 Disassembles ten more instructions before the last disassembly.
7255 @item record instruction-history @var{begin}, @var{end}
7256 Disassembles instructions beginning with instruction number
7257 @var{begin} until instruction number @var{end}. The instruction
7258 number @var{end} is included.
7261 This command may not be available for all recording methods.
7264 @item set record instruction-history-size @var{size}
7265 @itemx set record instruction-history-size unlimited
7266 Define how many instructions to disassemble in the @code{record
7267 instruction-history} command. The default value is 10.
7268 A @var{size} of @code{unlimited} means unlimited instructions.
7271 @item show record instruction-history-size
7272 Show how many instructions to disassemble in the @code{record
7273 instruction-history} command.
7275 @kindex record function-call-history
7276 @kindex rec function-call-history
7277 @item record function-call-history
7278 Prints the execution history at function granularity. It prints one
7279 line for each sequence of instructions that belong to the same
7280 function giving the name of that function, the source lines
7281 for this instruction sequence (if the @code{/l} modifier is
7282 specified), and the instructions numbers that form the sequence (if
7283 the @code{/i} modifier is specified). The function names are indented
7284 to reflect the call stack depth if the @code{/c} modifier is
7285 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7289 (@value{GDBP}) @b{list 1, 10}
7300 (@value{GDBP}) @b{record function-call-history /ilc}
7301 1 bar inst 1,4 at foo.c:6,8
7302 2 foo inst 5,10 at foo.c:2,3
7303 3 bar inst 11,13 at foo.c:9,10
7306 By default, ten lines are printed. This can be changed using the
7307 @code{set record function-call-history-size} command. Functions are
7308 printed in execution order. There are several ways to specify what
7312 @item record function-call-history @var{func}
7313 Prints ten functions starting from function number @var{func}.
7315 @item record function-call-history @var{func}, +/-@var{n}
7316 Prints @var{n} functions around function number @var{func}. If
7317 @var{n} is preceded with @code{+}, prints @var{n} functions after
7318 function number @var{func}. If @var{n} is preceded with @code{-},
7319 prints @var{n} functions before function number @var{func}.
7321 @item record function-call-history
7322 Prints ten more functions after the last ten-line print.
7324 @item record function-call-history -
7325 Prints ten more functions before the last ten-line print.
7327 @item record function-call-history @var{begin}, @var{end}
7328 Prints functions beginning with function number @var{begin} until
7329 function number @var{end}. The function number @var{end} is included.
7332 This command may not be available for all recording methods.
7334 @item set record function-call-history-size @var{size}
7335 @itemx set record function-call-history-size unlimited
7336 Define how many lines to print in the
7337 @code{record function-call-history} command. The default value is 10.
7338 A size of @code{unlimited} means unlimited lines.
7340 @item show record function-call-history-size
7341 Show how many lines to print in the
7342 @code{record function-call-history} command.
7347 @chapter Examining the Stack
7349 When your program has stopped, the first thing you need to know is where it
7350 stopped and how it got there.
7353 Each time your program performs a function call, information about the call
7355 That information includes the location of the call in your program,
7356 the arguments of the call,
7357 and the local variables of the function being called.
7358 The information is saved in a block of data called a @dfn{stack frame}.
7359 The stack frames are allocated in a region of memory called the @dfn{call
7362 When your program stops, the @value{GDBN} commands for examining the
7363 stack allow you to see all of this information.
7365 @cindex selected frame
7366 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7367 @value{GDBN} commands refer implicitly to the selected frame. In
7368 particular, whenever you ask @value{GDBN} for the value of a variable in
7369 your program, the value is found in the selected frame. There are
7370 special @value{GDBN} commands to select whichever frame you are
7371 interested in. @xref{Selection, ,Selecting a Frame}.
7373 When your program stops, @value{GDBN} automatically selects the
7374 currently executing frame and describes it briefly, similar to the
7375 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7378 * Frames:: Stack frames
7379 * Backtrace:: Backtraces
7380 * Selection:: Selecting a frame
7381 * Frame Info:: Information on a frame
7382 * Frame Apply:: Applying a command to several frames
7383 * Frame Filter Management:: Managing frame filters
7388 @section Stack Frames
7390 @cindex frame, definition
7392 The call stack is divided up into contiguous pieces called @dfn{stack
7393 frames}, or @dfn{frames} for short; each frame is the data associated
7394 with one call to one function. The frame contains the arguments given
7395 to the function, the function's local variables, and the address at
7396 which the function is executing.
7398 @cindex initial frame
7399 @cindex outermost frame
7400 @cindex innermost frame
7401 When your program is started, the stack has only one frame, that of the
7402 function @code{main}. This is called the @dfn{initial} frame or the
7403 @dfn{outermost} frame. Each time a function is called, a new frame is
7404 made. Each time a function returns, the frame for that function invocation
7405 is eliminated. If a function is recursive, there can be many frames for
7406 the same function. The frame for the function in which execution is
7407 actually occurring is called the @dfn{innermost} frame. This is the most
7408 recently created of all the stack frames that still exist.
7410 @cindex frame pointer
7411 Inside your program, stack frames are identified by their addresses. A
7412 stack frame consists of many bytes, each of which has its own address; each
7413 kind of computer has a convention for choosing one byte whose
7414 address serves as the address of the frame. Usually this address is kept
7415 in a register called the @dfn{frame pointer register}
7416 (@pxref{Registers, $fp}) while execution is going on in that frame.
7419 @cindex frame number
7420 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
7421 number that is zero for the innermost frame, one for the frame that
7422 called it, and so on upward. These level numbers give you a way of
7423 designating stack frames in @value{GDBN} commands. The terms
7424 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
7425 describe this number.
7427 @c The -fomit-frame-pointer below perennially causes hbox overflow
7428 @c underflow problems.
7429 @cindex frameless execution
7430 Some compilers provide a way to compile functions so that they operate
7431 without stack frames. (For example, the @value{NGCC} option
7433 @samp{-fomit-frame-pointer}
7435 generates functions without a frame.)
7436 This is occasionally done with heavily used library functions to save
7437 the frame setup time. @value{GDBN} has limited facilities for dealing
7438 with these function invocations. If the innermost function invocation
7439 has no stack frame, @value{GDBN} nevertheless regards it as though
7440 it had a separate frame, which is numbered zero as usual, allowing
7441 correct tracing of the function call chain. However, @value{GDBN} has
7442 no provision for frameless functions elsewhere in the stack.
7448 @cindex call stack traces
7449 A backtrace is a summary of how your program got where it is. It shows one
7450 line per frame, for many frames, starting with the currently executing
7451 frame (frame zero), followed by its caller (frame one), and on up the
7454 @anchor{backtrace-command}
7456 @kindex bt @r{(@code{backtrace})}
7457 To print a backtrace of the entire stack, use the @code{backtrace}
7458 command, or its alias @code{bt}. This command will print one line per
7459 frame for frames in the stack. By default, all stack frames are
7460 printed. You can stop the backtrace at any time by typing the system
7461 interrupt character, normally @kbd{Ctrl-c}.
7464 @item backtrace [@var{args}@dots{}]
7465 @itemx bt [@var{args}@dots{}]
7466 Print the backtrace of the entire stack. The optional @var{args} can
7467 be one of the following:
7472 Print only the innermost @var{n} frames, where @var{n} is a positive
7477 Print only the outermost @var{n} frames, where @var{n} is a positive
7481 Print the values of the local variables also. This can be combined
7482 with a number to limit the number of frames shown.
7485 Do not run Python frame filters on this backtrace. @xref{Frame
7486 Filter API}, for more information. Additionally use @ref{disable
7487 frame-filter all} to turn off all frame filters. This is only
7488 relevant when @value{GDBN} has been configured with @code{Python}
7492 A Python frame filter might decide to ``elide'' some frames. Normally
7493 such elided frames are still printed, but they are indented relative
7494 to the filtered frames that cause them to be elided. The @code{hide}
7495 option causes elided frames to not be printed at all.
7501 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7502 are additional aliases for @code{backtrace}.
7504 @cindex multiple threads, backtrace
7505 In a multi-threaded program, @value{GDBN} by default shows the
7506 backtrace only for the current thread. To display the backtrace for
7507 several or all of the threads, use the command @code{thread apply}
7508 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7509 apply all backtrace}, @value{GDBN} will display the backtrace for all
7510 the threads; this is handy when you debug a core dump of a
7511 multi-threaded program.
7513 Each line in the backtrace shows the frame number and the function name.
7514 The program counter value is also shown---unless you use @code{set
7515 print address off}. The backtrace also shows the source file name and
7516 line number, as well as the arguments to the function. The program
7517 counter value is omitted if it is at the beginning of the code for that
7520 Here is an example of a backtrace. It was made with the command
7521 @samp{bt 3}, so it shows the innermost three frames.
7525 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7527 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7528 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7530 (More stack frames follow...)
7535 The display for frame zero does not begin with a program counter
7536 value, indicating that your program has stopped at the beginning of the
7537 code for line @code{993} of @code{builtin.c}.
7540 The value of parameter @code{data} in frame 1 has been replaced by
7541 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7542 only if it is a scalar (integer, pointer, enumeration, etc). See command
7543 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7544 on how to configure the way function parameter values are printed.
7546 @cindex optimized out, in backtrace
7547 @cindex function call arguments, optimized out
7548 If your program was compiled with optimizations, some compilers will
7549 optimize away arguments passed to functions if those arguments are
7550 never used after the call. Such optimizations generate code that
7551 passes arguments through registers, but doesn't store those arguments
7552 in the stack frame. @value{GDBN} has no way of displaying such
7553 arguments in stack frames other than the innermost one. Here's what
7554 such a backtrace might look like:
7558 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7560 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7561 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7563 (More stack frames follow...)
7568 The values of arguments that were not saved in their stack frames are
7569 shown as @samp{<optimized out>}.
7571 If you need to display the values of such optimized-out arguments,
7572 either deduce that from other variables whose values depend on the one
7573 you are interested in, or recompile without optimizations.
7575 @cindex backtrace beyond @code{main} function
7576 @cindex program entry point
7577 @cindex startup code, and backtrace
7578 Most programs have a standard user entry point---a place where system
7579 libraries and startup code transition into user code. For C this is
7580 @code{main}@footnote{
7581 Note that embedded programs (the so-called ``free-standing''
7582 environment) are not required to have a @code{main} function as the
7583 entry point. They could even have multiple entry points.}.
7584 When @value{GDBN} finds the entry function in a backtrace
7585 it will terminate the backtrace, to avoid tracing into highly
7586 system-specific (and generally uninteresting) code.
7588 If you need to examine the startup code, or limit the number of levels
7589 in a backtrace, you can change this behavior:
7592 @item set backtrace past-main
7593 @itemx set backtrace past-main on
7594 @kindex set backtrace
7595 Backtraces will continue past the user entry point.
7597 @item set backtrace past-main off
7598 Backtraces will stop when they encounter the user entry point. This is the
7601 @item show backtrace past-main
7602 @kindex show backtrace
7603 Display the current user entry point backtrace policy.
7605 @item set backtrace past-entry
7606 @itemx set backtrace past-entry on
7607 Backtraces will continue past the internal entry point of an application.
7608 This entry point is encoded by the linker when the application is built,
7609 and is likely before the user entry point @code{main} (or equivalent) is called.
7611 @item set backtrace past-entry off
7612 Backtraces will stop when they encounter the internal entry point of an
7613 application. This is the default.
7615 @item show backtrace past-entry
7616 Display the current internal entry point backtrace policy.
7618 @item set backtrace limit @var{n}
7619 @itemx set backtrace limit 0
7620 @itemx set backtrace limit unlimited
7621 @cindex backtrace limit
7622 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7623 or zero means unlimited levels.
7625 @item show backtrace limit
7626 Display the current limit on backtrace levels.
7629 You can control how file names are displayed.
7632 @item set filename-display
7633 @itemx set filename-display relative
7634 @cindex filename-display
7635 Display file names relative to the compilation directory. This is the default.
7637 @item set filename-display basename
7638 Display only basename of a filename.
7640 @item set filename-display absolute
7641 Display an absolute filename.
7643 @item show filename-display
7644 Show the current way to display filenames.
7648 @section Selecting a Frame
7650 Most commands for examining the stack and other data in your program work on
7651 whichever stack frame is selected at the moment. Here are the commands for
7652 selecting a stack frame; all of them finish by printing a brief description
7653 of the stack frame just selected.
7656 @kindex frame@r{, selecting}
7657 @kindex f @r{(@code{frame})}
7658 @item frame @r{[} @var{frame-selection-spec} @r{]}
7659 @item f @r{[} @var{frame-selection-spec} @r{]}
7660 The @command{frame} command allows different stack frames to be
7661 selected. The @var{frame-selection-spec} can be any of the following:
7666 @item level @var{num}
7667 Select frame level @var{num}. Recall that frame zero is the innermost
7668 (currently executing) frame, frame one is the frame that called the
7669 innermost one, and so on. The highest level frame is usually the one
7672 As this is the most common method of navigating the frame stack, the
7673 string @command{level} can be omitted. For example, the following two
7674 commands are equivalent:
7677 (@value{GDBP}) frame 3
7678 (@value{GDBP}) frame level 3
7681 @kindex frame address
7682 @item address @var{stack-address}
7683 Select the frame with stack address @var{stack-address}. The
7684 @var{stack-address} for a frame can be seen in the output of
7685 @command{info frame}, for example:
7689 Stack level 1, frame at 0x7fffffffda30:
7690 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
7691 tail call frame, caller of frame at 0x7fffffffda30
7692 source language c++.
7693 Arglist at unknown address.
7694 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
7697 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
7698 indicated by the line:
7701 Stack level 1, frame at 0x7fffffffda30:
7704 @kindex frame function
7705 @item function @var{function-name}
7706 Select the stack frame for function @var{function-name}. If there are
7707 multiple stack frames for function @var{function-name} then the inner
7708 most stack frame is selected.
7711 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
7712 View a frame that is not part of @value{GDBN}'s backtrace. The frame
7713 viewed has stack address @var{stack-addr}, and optionally, a program
7714 counter address of @var{pc-addr}.
7716 This is useful mainly if the chaining of stack frames has been
7717 damaged by a bug, making it impossible for @value{GDBN} to assign
7718 numbers properly to all frames. In addition, this can be useful
7719 when your program has multiple stacks and switches between them.
7721 When viewing a frame outside the current backtrace using
7722 @command{frame view} then you can always return to the original
7723 stack using one of the previous stack frame selection instructions,
7724 for example @command{frame level 0}.
7730 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7731 numbers @var{n}, this advances toward the outermost frame, to higher
7732 frame numbers, to frames that have existed longer.
7735 @kindex do @r{(@code{down})}
7737 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7738 positive numbers @var{n}, this advances toward the innermost frame, to
7739 lower frame numbers, to frames that were created more recently.
7740 You may abbreviate @code{down} as @code{do}.
7743 All of these commands end by printing two lines of output describing the
7744 frame. The first line shows the frame number, the function name, the
7745 arguments, and the source file and line number of execution in that
7746 frame. The second line shows the text of that source line.
7754 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7756 10 read_input_file (argv[i]);
7760 After such a printout, the @code{list} command with no arguments
7761 prints ten lines centered on the point of execution in the frame.
7762 You can also edit the program at the point of execution with your favorite
7763 editing program by typing @code{edit}.
7764 @xref{List, ,Printing Source Lines},
7768 @kindex select-frame
7769 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
7770 The @code{select-frame} command is a variant of @code{frame} that does
7771 not display the new frame after selecting it. This command is
7772 intended primarily for use in @value{GDBN} command scripts, where the
7773 output might be unnecessary and distracting. The
7774 @var{frame-selection-spec} is as for the @command{frame} command
7775 described in @ref{Selection, ,Selecting a Frame}.
7777 @kindex down-silently
7779 @item up-silently @var{n}
7780 @itemx down-silently @var{n}
7781 These two commands are variants of @code{up} and @code{down},
7782 respectively; they differ in that they do their work silently, without
7783 causing display of the new frame. They are intended primarily for use
7784 in @value{GDBN} command scripts, where the output might be unnecessary and
7789 @section Information About a Frame
7791 There are several other commands to print information about the selected
7797 When used without any argument, this command does not change which
7798 frame is selected, but prints a brief description of the currently
7799 selected stack frame. It can be abbreviated @code{f}. With an
7800 argument, this command is used to select a stack frame.
7801 @xref{Selection, ,Selecting a Frame}.
7804 @kindex info f @r{(@code{info frame})}
7807 This command prints a verbose description of the selected stack frame,
7812 the address of the frame
7814 the address of the next frame down (called by this frame)
7816 the address of the next frame up (caller of this frame)
7818 the language in which the source code corresponding to this frame is written
7820 the address of the frame's arguments
7822 the address of the frame's local variables
7824 the program counter saved in it (the address of execution in the caller frame)
7826 which registers were saved in the frame
7829 @noindent The verbose description is useful when
7830 something has gone wrong that has made the stack format fail to fit
7831 the usual conventions.
7833 @item info frame @r{[} @var{frame-selection-spec} @r{]}
7834 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
7835 Print a verbose description of the frame selected by
7836 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
7837 same as for the @command{frame} command (@pxref{Selection, ,Selecting
7838 a Frame}). The selected frame remains unchanged by this command.
7841 @item info args [-q]
7842 Print the arguments of the selected frame, each on a separate line.
7844 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
7845 printing header information and messages explaining why no argument
7848 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
7849 Like @kbd{info args}, but only print the arguments selected
7850 with the provided regexp(s).
7852 If @var{regexp} is provided, print only the arguments whose names
7853 match the regular expression @var{regexp}.
7855 If @var{type_regexp} is provided, print only the arguments whose
7856 types, as printed by the @code{whatis} command, match
7857 the regular expression @var{type_regexp}.
7858 If @var{type_regexp} contains space(s), it should be enclosed in
7859 quote characters. If needed, use backslash to escape the meaning
7860 of special characters or quotes.
7862 If both @var{regexp} and @var{type_regexp} are provided, an argument
7863 is printed only if its name matches @var{regexp} and its type matches
7866 @item info locals [-q]
7868 Print the local variables of the selected frame, each on a separate
7869 line. These are all variables (declared either static or automatic)
7870 accessible at the point of execution of the selected frame.
7872 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
7873 printing header information and messages explaining why no local variables
7876 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
7877 Like @kbd{info locals}, but only print the local variables selected
7878 with the provided regexp(s).
7880 If @var{regexp} is provided, print only the local variables whose names
7881 match the regular expression @var{regexp}.
7883 If @var{type_regexp} is provided, print only the local variables whose
7884 types, as printed by the @code{whatis} command, match
7885 the regular expression @var{type_regexp}.
7886 If @var{type_regexp} contains space(s), it should be enclosed in
7887 quote characters. If needed, use backslash to escape the meaning
7888 of special characters or quotes.
7890 If both @var{regexp} and @var{type_regexp} are provided, a local variable
7891 is printed only if its name matches @var{regexp} and its type matches
7894 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
7895 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
7896 For example, your program might use Resource Acquisition Is
7897 Initialization types (RAII) such as @code{lock_something_t}: each
7898 local variable of type @code{lock_something_t} automatically places a
7899 lock that is destroyed when the variable goes out of scope. You can
7900 then list all acquired locks in your program by doing
7902 thread apply all -s frame apply all -s info locals -q -t lock_something_t
7905 or the equivalent shorter form
7907 tfaas i lo -q -t lock_something_t
7913 @section Applying a Command to Several Frames.
7915 @cindex apply command to several frames
7917 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{flag}]@dots{} @var{command}
7918 The @code{frame apply} command allows you to apply the named
7919 @var{command} to one or more frames.
7923 Specify @code{all} to apply @var{command} to all frames.
7926 Use @var{count} to apply @var{command} to the innermost @var{count}
7927 frames, where @var{count} is a positive number.
7930 Use @var{-count} to apply @var{command} to the outermost @var{count}
7931 frames, where @var{count} is a positive number.
7934 Use @code{level} to apply @var{command} to the set of frames identified
7935 by the @var{level} list. @var{level} is a frame level or a range of frame
7936 levels as @var{level1}-@var{level2}. The frame level is the number shown
7937 in the first field of the @samp{backtrace} command output.
7938 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
7939 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
7945 Note that the frames on which @code{frame apply} applies a command are
7946 also influenced by the @code{set backtrace} settings such as @code{set
7947 backtrace past-main} and @code{set backtrace limit N}. See
7948 @xref{Backtrace,,Backtraces}.
7950 The @var{flag} arguments control what output to produce and how to handle
7951 errors raised when applying @var{command} to a frame. @var{flag}
7952 must start with a @code{-} directly followed by one letter in
7953 @code{qcs}. If several flags are provided, they must be given
7954 individually, such as @code{-c -q}.
7956 By default, @value{GDBN} displays some frame information before the
7957 output produced by @var{command}, and an error raised during the
7958 execution of a @var{command} will abort @code{frame apply}. The
7959 following flags can be used to fine-tune this behavior:
7963 The flag @code{-c}, which stands for @samp{continue}, causes any
7964 errors in @var{command} to be displayed, and the execution of
7965 @code{frame apply} then continues.
7967 The flag @code{-s}, which stands for @samp{silent}, causes any errors
7968 or empty output produced by a @var{command} to be silently ignored.
7969 That is, the execution continues, but the frame information and errors
7972 The flag @code{-q} (@samp{quiet}) disables printing the frame
7976 The following example shows how the flags @code{-c} and @code{-s} are
7977 working when applying the command @code{p j} to all frames, where
7978 variable @code{j} can only be successfully printed in the outermost
7979 @code{#1 main} frame.
7983 (gdb) frame apply all p j
7984 #0 some_function (i=5) at fun.c:4
7985 No symbol "j" in current context.
7986 (gdb) frame apply all -c p j
7987 #0 some_function (i=5) at fun.c:4
7988 No symbol "j" in current context.
7989 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
7991 (gdb) frame apply all -s p j
7992 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
7998 By default, @samp{frame apply}, prints the frame location
7999 information before the command output:
8003 (gdb) frame apply all p $sp
8004 #0 some_function (i=5) at fun.c:4
8005 $4 = (void *) 0xffffd1e0
8006 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8007 $5 = (void *) 0xffffd1f0
8012 If flag @code{-q} is given, no frame information is printed:
8015 (gdb) frame apply all -q p $sp
8016 $12 = (void *) 0xffffd1e0
8017 $13 = (void *) 0xffffd1f0
8025 @cindex apply a command to all frames (ignoring errors and empty output)
8026 @item faas @var{command}
8027 Shortcut for @code{frame apply all -s @var{command}}.
8028 Applies @var{command} on all frames, ignoring errors and empty output.
8030 It can for example be used to print a local variable or a function
8031 argument without knowing the frame where this variable or argument
8034 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8037 Note that the command @code{tfaas @var{command}} applies @var{command}
8038 on all frames of all threads. See @xref{Threads,,Threads}.
8042 @node Frame Filter Management
8043 @section Management of Frame Filters.
8044 @cindex managing frame filters
8046 Frame filters are Python based utilities to manage and decorate the
8047 output of frames. @xref{Frame Filter API}, for further information.
8049 Managing frame filters is performed by several commands available
8050 within @value{GDBN}, detailed here.
8053 @kindex info frame-filter
8054 @item info frame-filter
8055 Print a list of installed frame filters from all dictionaries, showing
8056 their name, priority and enabled status.
8058 @kindex disable frame-filter
8059 @anchor{disable frame-filter all}
8060 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8061 Disable a frame filter in the dictionary matching
8062 @var{filter-dictionary} and @var{filter-name}. The
8063 @var{filter-dictionary} may be @code{all}, @code{global},
8064 @code{progspace}, or the name of the object file where the frame filter
8065 dictionary resides. When @code{all} is specified, all frame filters
8066 across all dictionaries are disabled. The @var{filter-name} is the name
8067 of the frame filter and is used when @code{all} is not the option for
8068 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8069 may be enabled again later.
8071 @kindex enable frame-filter
8072 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8073 Enable 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 across
8078 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8079 filter and is used when @code{all} is not the option for
8080 @var{filter-dictionary}.
8085 (gdb) info frame-filter
8087 global frame-filters:
8088 Priority Enabled Name
8089 1000 No PrimaryFunctionFilter
8092 progspace /build/test frame-filters:
8093 Priority Enabled Name
8094 100 Yes ProgspaceFilter
8096 objfile /build/test frame-filters:
8097 Priority Enabled Name
8098 999 Yes BuildProgra Filter
8100 (gdb) disable frame-filter /build/test BuildProgramFilter
8101 (gdb) info frame-filter
8103 global frame-filters:
8104 Priority Enabled Name
8105 1000 No PrimaryFunctionFilter
8108 progspace /build/test frame-filters:
8109 Priority Enabled Name
8110 100 Yes ProgspaceFilter
8112 objfile /build/test frame-filters:
8113 Priority Enabled Name
8114 999 No BuildProgramFilter
8116 (gdb) enable frame-filter global PrimaryFunctionFilter
8117 (gdb) info frame-filter
8119 global frame-filters:
8120 Priority Enabled Name
8121 1000 Yes PrimaryFunctionFilter
8124 progspace /build/test frame-filters:
8125 Priority Enabled Name
8126 100 Yes ProgspaceFilter
8128 objfile /build/test frame-filters:
8129 Priority Enabled Name
8130 999 No BuildProgramFilter
8133 @kindex set frame-filter priority
8134 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8135 Set the @var{priority} of a frame filter in the dictionary matching
8136 @var{filter-dictionary}, and the frame filter name matching
8137 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8138 @code{progspace} or the name of the object file where the frame filter
8139 dictionary resides. The @var{priority} is an integer.
8141 @kindex show frame-filter priority
8142 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8143 Show the @var{priority} of a frame filter in the dictionary matching
8144 @var{filter-dictionary}, and the frame filter name matching
8145 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8146 @code{progspace} or the name of the object file where the frame filter
8152 (gdb) info frame-filter
8154 global frame-filters:
8155 Priority Enabled Name
8156 1000 Yes PrimaryFunctionFilter
8159 progspace /build/test frame-filters:
8160 Priority Enabled Name
8161 100 Yes ProgspaceFilter
8163 objfile /build/test frame-filters:
8164 Priority Enabled Name
8165 999 No BuildProgramFilter
8167 (gdb) set frame-filter priority global Reverse 50
8168 (gdb) info frame-filter
8170 global frame-filters:
8171 Priority Enabled Name
8172 1000 Yes PrimaryFunctionFilter
8175 progspace /build/test frame-filters:
8176 Priority Enabled Name
8177 100 Yes ProgspaceFilter
8179 objfile /build/test frame-filters:
8180 Priority Enabled Name
8181 999 No BuildProgramFilter
8186 @chapter Examining Source Files
8188 @value{GDBN} can print parts of your program's source, since the debugging
8189 information recorded in the program tells @value{GDBN} what source files were
8190 used to build it. When your program stops, @value{GDBN} spontaneously prints
8191 the line where it stopped. Likewise, when you select a stack frame
8192 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8193 execution in that frame has stopped. You can print other portions of
8194 source files by explicit command.
8196 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8197 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8198 @value{GDBN} under @sc{gnu} Emacs}.
8201 * List:: Printing source lines
8202 * Specify Location:: How to specify code locations
8203 * Edit:: Editing source files
8204 * Search:: Searching source files
8205 * Source Path:: Specifying source directories
8206 * Machine Code:: Source and machine code
8210 @section Printing Source Lines
8213 @kindex l @r{(@code{list})}
8214 To print lines from a source file, use the @code{list} command
8215 (abbreviated @code{l}). By default, ten lines are printed.
8216 There are several ways to specify what part of the file you want to
8217 print; see @ref{Specify Location}, for the full list.
8219 Here are the forms of the @code{list} command most commonly used:
8222 @item list @var{linenum}
8223 Print lines centered around line number @var{linenum} in the
8224 current source file.
8226 @item list @var{function}
8227 Print lines centered around the beginning of function
8231 Print more lines. If the last lines printed were printed with a
8232 @code{list} command, this prints lines following the last lines
8233 printed; however, if the last line printed was a solitary line printed
8234 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8235 Stack}), this prints lines centered around that line.
8238 Print lines just before the lines last printed.
8241 @cindex @code{list}, how many lines to display
8242 By default, @value{GDBN} prints ten source lines with any of these forms of
8243 the @code{list} command. You can change this using @code{set listsize}:
8246 @kindex set listsize
8247 @item set listsize @var{count}
8248 @itemx set listsize unlimited
8249 Make the @code{list} command display @var{count} source lines (unless
8250 the @code{list} argument explicitly specifies some other number).
8251 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8253 @kindex show listsize
8255 Display the number of lines that @code{list} prints.
8258 Repeating a @code{list} command with @key{RET} discards the argument,
8259 so it is equivalent to typing just @code{list}. This is more useful
8260 than listing the same lines again. An exception is made for an
8261 argument of @samp{-}; that argument is preserved in repetition so that
8262 each repetition moves up in the source file.
8264 In general, the @code{list} command expects you to supply zero, one or two
8265 @dfn{locations}. Locations specify source lines; there are several ways
8266 of writing them (@pxref{Specify Location}), but the effect is always
8267 to specify some source line.
8269 Here is a complete description of the possible arguments for @code{list}:
8272 @item list @var{location}
8273 Print lines centered around the line specified by @var{location}.
8275 @item list @var{first},@var{last}
8276 Print lines from @var{first} to @var{last}. Both arguments are
8277 locations. When a @code{list} command has two locations, and the
8278 source file of the second location is omitted, this refers to
8279 the same source file as the first location.
8281 @item list ,@var{last}
8282 Print lines ending with @var{last}.
8284 @item list @var{first},
8285 Print lines starting with @var{first}.
8288 Print lines just after the lines last printed.
8291 Print lines just before the lines last printed.
8294 As described in the preceding table.
8297 @node Specify Location
8298 @section Specifying a Location
8299 @cindex specifying location
8301 @cindex source location
8304 * Linespec Locations:: Linespec locations
8305 * Explicit Locations:: Explicit locations
8306 * Address Locations:: Address locations
8309 Several @value{GDBN} commands accept arguments that specify a location
8310 of your program's code. Since @value{GDBN} is a source-level
8311 debugger, a location usually specifies some line in the source code.
8312 Locations may be specified using three different formats:
8313 linespec locations, explicit locations, or address locations.
8315 @node Linespec Locations
8316 @subsection Linespec Locations
8317 @cindex linespec locations
8319 A @dfn{linespec} is a colon-separated list of source location parameters such
8320 as file name, function name, etc. Here are all the different ways of
8321 specifying a linespec:
8325 Specifies the line number @var{linenum} of the current source file.
8328 @itemx +@var{offset}
8329 Specifies the line @var{offset} lines before or after the @dfn{current
8330 line}. For the @code{list} command, the current line is the last one
8331 printed; for the breakpoint commands, this is the line at which
8332 execution stopped in the currently selected @dfn{stack frame}
8333 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
8334 used as the second of the two linespecs in a @code{list} command,
8335 this specifies the line @var{offset} lines up or down from the first
8338 @item @var{filename}:@var{linenum}
8339 Specifies the line @var{linenum} in the source file @var{filename}.
8340 If @var{filename} is a relative file name, then it will match any
8341 source file name with the same trailing components. For example, if
8342 @var{filename} is @samp{gcc/expr.c}, then it will match source file
8343 name of @file{/build/trunk/gcc/expr.c}, but not
8344 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
8346 @item @var{function}
8347 Specifies the line that begins the body of the function @var{function}.
8348 For example, in C, this is the line with the open brace.
8350 By default, in C@t{++} and Ada, @var{function} is interpreted as
8351 specifying all functions named @var{function} in all scopes. For
8352 C@t{++}, this means in all namespaces and classes. For Ada, this
8353 means in all packages.
8355 For example, assuming a program with C@t{++} symbols named
8356 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8357 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
8359 Commands that accept a linespec let you override this with the
8360 @code{-qualified} option. For example, @w{@kbd{break -qualified
8361 func}} sets a breakpoint on a free-function named @code{func} ignoring
8362 any C@t{++} class methods and namespace functions called @code{func}.
8364 @xref{Explicit Locations}.
8366 @item @var{function}:@var{label}
8367 Specifies the line where @var{label} appears in @var{function}.
8369 @item @var{filename}:@var{function}
8370 Specifies the line that begins the body of the function @var{function}
8371 in the file @var{filename}. You only need the file name with a
8372 function name to avoid ambiguity when there are identically named
8373 functions in different source files.
8376 Specifies the line at which the label named @var{label} appears
8377 in the function corresponding to the currently selected stack frame.
8378 If there is no current selected stack frame (for instance, if the inferior
8379 is not running), then @value{GDBN} will not search for a label.
8381 @cindex breakpoint at static probe point
8382 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
8383 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
8384 applications to embed static probes. @xref{Static Probe Points}, for more
8385 information on finding and using static probes. This form of linespec
8386 specifies the location of such a static probe.
8388 If @var{objfile} is given, only probes coming from that shared library
8389 or executable matching @var{objfile} as a regular expression are considered.
8390 If @var{provider} is given, then only probes from that provider are considered.
8391 If several probes match the spec, @value{GDBN} will insert a breakpoint at
8392 each one of those probes.
8395 @node Explicit Locations
8396 @subsection Explicit Locations
8397 @cindex explicit locations
8399 @dfn{Explicit locations} allow the user to directly specify the source
8400 location's parameters using option-value pairs.
8402 Explicit locations are useful when several functions, labels, or
8403 file names have the same name (base name for files) in the program's
8404 sources. In these cases, explicit locations point to the source
8405 line you meant more accurately and unambiguously. Also, using
8406 explicit locations might be faster in large programs.
8408 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
8409 defined in the file named @file{foo} or the label @code{bar} in a function
8410 named @code{foo}. @value{GDBN} must search either the file system or
8411 the symbol table to know.
8413 The list of valid explicit location options is summarized in the
8417 @item -source @var{filename}
8418 The value specifies the source file name. To differentiate between
8419 files with the same base name, prepend as many directories as is necessary
8420 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8421 @value{GDBN} will use the first file it finds with the given base
8422 name. This option requires the use of either @code{-function} or @code{-line}.
8424 @item -function @var{function}
8425 The value specifies the name of a function. Operations
8426 on function locations unmodified by other options (such as @code{-label}
8427 or @code{-line}) refer to the line that begins the body of the function.
8428 In C, for example, this is the line with the open brace.
8430 By default, in C@t{++} and Ada, @var{function} is interpreted as
8431 specifying all functions named @var{function} in all scopes. For
8432 C@t{++}, this means in all namespaces and classes. For Ada, this
8433 means in all packages.
8435 For example, assuming a program with C@t{++} symbols named
8436 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8437 -function func}} and @w{@kbd{break -function B::func}} set a
8438 breakpoint on both symbols.
8440 You can use the @kbd{-qualified} flag to override this (see below).
8444 This flag makes @value{GDBN} interpret a function name specified with
8445 @kbd{-function} as a complete fully-qualified name.
8447 For example, assuming a C@t{++} program with symbols named
8448 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8449 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8451 (Note: the @kbd{-qualified} option can precede a linespec as well
8452 (@pxref{Linespec Locations}), so the particular example above could be
8453 simplified as @w{@kbd{break -qualified B::func}}.)
8455 @item -label @var{label}
8456 The value specifies the name of a label. When the function
8457 name is not specified, the label is searched in the function of the currently
8458 selected stack frame.
8460 @item -line @var{number}
8461 The value specifies a line offset for the location. The offset may either
8462 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8463 the command. When specified without any other options, the line offset is
8464 relative to the current line.
8467 Explicit location options may be abbreviated by omitting any non-unique
8468 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8470 @node Address Locations
8471 @subsection Address Locations
8472 @cindex address locations
8474 @dfn{Address locations} indicate a specific program address. They have
8475 the generalized form *@var{address}.
8477 For line-oriented commands, such as @code{list} and @code{edit}, this
8478 specifies a source line that contains @var{address}. For @code{break} and
8479 other breakpoint-oriented commands, this can be used to set breakpoints in
8480 parts of your program which do not have debugging information or
8483 Here @var{address} may be any expression valid in the current working
8484 language (@pxref{Languages, working language}) that specifies a code
8485 address. In addition, as a convenience, @value{GDBN} extends the
8486 semantics of expressions used in locations to cover several situations
8487 that frequently occur during debugging. Here are the various forms
8491 @item @var{expression}
8492 Any expression valid in the current working language.
8494 @item @var{funcaddr}
8495 An address of a function or procedure derived from its name. In C,
8496 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8497 simply the function's name @var{function} (and actually a special case
8498 of a valid expression). In Pascal and Modula-2, this is
8499 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8500 (although the Pascal form also works).
8502 This form specifies the address of the function's first instruction,
8503 before the stack frame and arguments have been set up.
8505 @item '@var{filename}':@var{funcaddr}
8506 Like @var{funcaddr} above, but also specifies the name of the source
8507 file explicitly. This is useful if the name of the function does not
8508 specify the function unambiguously, e.g., if there are several
8509 functions with identical names in different source files.
8513 @section Editing Source Files
8514 @cindex editing source files
8517 @kindex e @r{(@code{edit})}
8518 To edit the lines in a source file, use the @code{edit} command.
8519 The editing program of your choice
8520 is invoked with the current line set to
8521 the active line in the program.
8522 Alternatively, there are several ways to specify what part of the file you
8523 want to print if you want to see other parts of the program:
8526 @item edit @var{location}
8527 Edit the source file specified by @code{location}. Editing starts at
8528 that @var{location}, e.g., at the specified source line of the
8529 specified file. @xref{Specify Location}, for all the possible forms
8530 of the @var{location} argument; here are the forms of the @code{edit}
8531 command most commonly used:
8534 @item edit @var{number}
8535 Edit the current source file with @var{number} as the active line number.
8537 @item edit @var{function}
8538 Edit the file containing @var{function} at the beginning of its definition.
8543 @subsection Choosing your Editor
8544 You can customize @value{GDBN} to use any editor you want
8546 The only restriction is that your editor (say @code{ex}), recognizes the
8547 following command-line syntax:
8549 ex +@var{number} file
8551 The optional numeric value +@var{number} specifies the number of the line in
8552 the file where to start editing.}.
8553 By default, it is @file{@value{EDITOR}}, but you can change this
8554 by setting the environment variable @code{EDITOR} before using
8555 @value{GDBN}. For example, to configure @value{GDBN} to use the
8556 @code{vi} editor, you could use these commands with the @code{sh} shell:
8562 or in the @code{csh} shell,
8564 setenv EDITOR /usr/bin/vi
8569 @section Searching Source Files
8570 @cindex searching source files
8572 There are two commands for searching through the current source file for a
8577 @kindex forward-search
8578 @kindex fo @r{(@code{forward-search})}
8579 @item forward-search @var{regexp}
8580 @itemx search @var{regexp}
8581 The command @samp{forward-search @var{regexp}} checks each line,
8582 starting with the one following the last line listed, for a match for
8583 @var{regexp}. It lists the line that is found. You can use the
8584 synonym @samp{search @var{regexp}} or abbreviate the command name as
8587 @kindex reverse-search
8588 @item reverse-search @var{regexp}
8589 The command @samp{reverse-search @var{regexp}} checks each line, starting
8590 with the one before the last line listed and going backward, for a match
8591 for @var{regexp}. It lists the line that is found. You can abbreviate
8592 this command as @code{rev}.
8596 @section Specifying Source Directories
8599 @cindex directories for source files
8600 Executable programs sometimes do not record the directories of the source
8601 files from which they were compiled, just the names. Even when they do,
8602 the directories could be moved between the compilation and your debugging
8603 session. @value{GDBN} has a list of directories to search for source files;
8604 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8605 it tries all the directories in the list, in the order they are present
8606 in the list, until it finds a file with the desired name.
8608 For example, suppose an executable references the file
8609 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8610 @file{/mnt/cross}. The file is first looked up literally; if this
8611 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8612 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8613 message is printed. @value{GDBN} does not look up the parts of the
8614 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8615 Likewise, the subdirectories of the source path are not searched: if
8616 the source path is @file{/mnt/cross}, and the binary refers to
8617 @file{foo.c}, @value{GDBN} would not find it under
8618 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8620 Plain file names, relative file names with leading directories, file
8621 names containing dots, etc.@: are all treated as described above; for
8622 instance, if the source path is @file{/mnt/cross}, and the source file
8623 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8624 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8625 that---@file{/mnt/cross/foo.c}.
8627 Note that the executable search path is @emph{not} used to locate the
8630 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8631 any information it has cached about where source files are found and where
8632 each line is in the file.
8636 When you start @value{GDBN}, its source path includes only @samp{cdir}
8637 and @samp{cwd}, in that order.
8638 To add other directories, use the @code{directory} command.
8640 The search path is used to find both program source files and @value{GDBN}
8641 script files (read using the @samp{-command} option and @samp{source} command).
8643 In addition to the source path, @value{GDBN} provides a set of commands
8644 that manage a list of source path substitution rules. A @dfn{substitution
8645 rule} specifies how to rewrite source directories stored in the program's
8646 debug information in case the sources were moved to a different
8647 directory between compilation and debugging. A rule is made of
8648 two strings, the first specifying what needs to be rewritten in
8649 the path, and the second specifying how it should be rewritten.
8650 In @ref{set substitute-path}, we name these two parts @var{from} and
8651 @var{to} respectively. @value{GDBN} does a simple string replacement
8652 of @var{from} with @var{to} at the start of the directory part of the
8653 source file name, and uses that result instead of the original file
8654 name to look up the sources.
8656 Using the previous example, suppose the @file{foo-1.0} tree has been
8657 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8658 @value{GDBN} to replace @file{/usr/src} in all source path names with
8659 @file{/mnt/cross}. The first lookup will then be
8660 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8661 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8662 substitution rule, use the @code{set substitute-path} command
8663 (@pxref{set substitute-path}).
8665 To avoid unexpected substitution results, a rule is applied only if the
8666 @var{from} part of the directory name ends at a directory separator.
8667 For instance, a rule substituting @file{/usr/source} into
8668 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8669 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8670 is applied only at the beginning of the directory name, this rule will
8671 not be applied to @file{/root/usr/source/baz.c} either.
8673 In many cases, you can achieve the same result using the @code{directory}
8674 command. However, @code{set substitute-path} can be more efficient in
8675 the case where the sources are organized in a complex tree with multiple
8676 subdirectories. With the @code{directory} command, you need to add each
8677 subdirectory of your project. If you moved the entire tree while
8678 preserving its internal organization, then @code{set substitute-path}
8679 allows you to direct the debugger to all the sources with one single
8682 @code{set substitute-path} is also more than just a shortcut command.
8683 The source path is only used if the file at the original location no
8684 longer exists. On the other hand, @code{set substitute-path} modifies
8685 the debugger behavior to look at the rewritten location instead. So, if
8686 for any reason a source file that is not relevant to your executable is
8687 located at the original location, a substitution rule is the only
8688 method available to point @value{GDBN} at the new location.
8690 @cindex @samp{--with-relocated-sources}
8691 @cindex default source path substitution
8692 You can configure a default source path substitution rule by
8693 configuring @value{GDBN} with the
8694 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8695 should be the name of a directory under @value{GDBN}'s configured
8696 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8697 directory names in debug information under @var{dir} will be adjusted
8698 automatically if the installed @value{GDBN} is moved to a new
8699 location. This is useful if @value{GDBN}, libraries or executables
8700 with debug information and corresponding source code are being moved
8704 @item directory @var{dirname} @dots{}
8705 @item dir @var{dirname} @dots{}
8706 Add directory @var{dirname} to the front of the source path. Several
8707 directory names may be given to this command, separated by @samp{:}
8708 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8709 part of absolute file names) or
8710 whitespace. You may specify a directory that is already in the source
8711 path; this moves it forward, so @value{GDBN} searches it sooner.
8715 @vindex $cdir@r{, convenience variable}
8716 @vindex $cwd@r{, convenience variable}
8717 @cindex compilation directory
8718 @cindex current directory
8719 @cindex working directory
8720 @cindex directory, current
8721 @cindex directory, compilation
8722 You can use the string @samp{$cdir} to refer to the compilation
8723 directory (if one is recorded), and @samp{$cwd} to refer to the current
8724 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8725 tracks the current working directory as it changes during your @value{GDBN}
8726 session, while the latter is immediately expanded to the current
8727 directory at the time you add an entry to the source path.
8730 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8732 @c RET-repeat for @code{directory} is explicitly disabled, but since
8733 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8735 @item set directories @var{path-list}
8736 @kindex set directories
8737 Set the source path to @var{path-list}.
8738 @samp{$cdir:$cwd} are added if missing.
8740 @item show directories
8741 @kindex show directories
8742 Print the source path: show which directories it contains.
8744 @anchor{set substitute-path}
8745 @item set substitute-path @var{from} @var{to}
8746 @kindex set substitute-path
8747 Define a source path substitution rule, and add it at the end of the
8748 current list of existing substitution rules. If a rule with the same
8749 @var{from} was already defined, then the old rule is also deleted.
8751 For example, if the file @file{/foo/bar/baz.c} was moved to
8752 @file{/mnt/cross/baz.c}, then the command
8755 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8759 will tell @value{GDBN} to replace @samp{/foo/bar} with
8760 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8761 @file{baz.c} even though it was moved.
8763 In the case when more than one substitution rule have been defined,
8764 the rules are evaluated one by one in the order where they have been
8765 defined. The first one matching, if any, is selected to perform
8768 For instance, if we had entered the following commands:
8771 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8772 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8776 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8777 @file{/mnt/include/defs.h} by using the first rule. However, it would
8778 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8779 @file{/mnt/src/lib/foo.c}.
8782 @item unset substitute-path [path]
8783 @kindex unset substitute-path
8784 If a path is specified, search the current list of substitution rules
8785 for a rule that would rewrite that path. Delete that rule if found.
8786 A warning is emitted by the debugger if no rule could be found.
8788 If no path is specified, then all substitution rules are deleted.
8790 @item show substitute-path [path]
8791 @kindex show substitute-path
8792 If a path is specified, then print the source path substitution rule
8793 which would rewrite that path, if any.
8795 If no path is specified, then print all existing source path substitution
8800 If your source path is cluttered with directories that are no longer of
8801 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8802 versions of source. You can correct the situation as follows:
8806 Use @code{directory} with no argument to reset the source path to its default value.
8809 Use @code{directory} with suitable arguments to reinstall the
8810 directories you want in the source path. You can add all the
8811 directories in one command.
8815 @section Source and Machine Code
8816 @cindex source line and its code address
8818 You can use the command @code{info line} to map source lines to program
8819 addresses (and vice versa), and the command @code{disassemble} to display
8820 a range of addresses as machine instructions. You can use the command
8821 @code{set disassemble-next-line} to set whether to disassemble next
8822 source line when execution stops. When run under @sc{gnu} Emacs
8823 mode, the @code{info line} command causes the arrow to point to the
8824 line specified. Also, @code{info line} prints addresses in symbolic form as
8830 @itemx info line @var{location}
8831 Print the starting and ending addresses of the compiled code for
8832 source line @var{location}. You can specify source lines in any of
8833 the ways documented in @ref{Specify Location}. With no @var{location}
8834 information about the current source line is printed.
8837 For example, we can use @code{info line} to discover the location of
8838 the object code for the first line of function
8839 @code{m4_changequote}:
8842 (@value{GDBP}) info line m4_changequote
8843 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
8844 ends at 0x6350 <m4_changequote+4>.
8848 @cindex code address and its source line
8849 We can also inquire (using @code{*@var{addr}} as the form for
8850 @var{location}) what source line covers a particular address:
8852 (@value{GDBP}) info line *0x63ff
8853 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
8854 ends at 0x6404 <m4_changequote+184>.
8857 @cindex @code{$_} and @code{info line}
8858 @cindex @code{x} command, default address
8859 @kindex x@r{(examine), and} info line
8860 After @code{info line}, the default address for the @code{x} command
8861 is changed to the starting address of the line, so that @samp{x/i} is
8862 sufficient to begin examining the machine code (@pxref{Memory,
8863 ,Examining Memory}). Also, this address is saved as the value of the
8864 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8867 @cindex info line, repeated calls
8868 After @code{info line}, using @code{info line} again without
8869 specifying a location will display information about the next source
8874 @cindex assembly instructions
8875 @cindex instructions, assembly
8876 @cindex machine instructions
8877 @cindex listing machine instructions
8879 @itemx disassemble /m
8880 @itemx disassemble /s
8881 @itemx disassemble /r
8882 This specialized command dumps a range of memory as machine
8883 instructions. It can also print mixed source+disassembly by specifying
8884 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8885 as well as in symbolic form by specifying the @code{/r} modifier.
8886 The default memory range is the function surrounding the
8887 program counter of the selected frame. A single argument to this
8888 command is a program counter value; @value{GDBN} dumps the function
8889 surrounding this value. When two arguments are given, they should
8890 be separated by a comma, possibly surrounded by whitespace. The
8891 arguments specify a range of addresses to dump, in one of two forms:
8894 @item @var{start},@var{end}
8895 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8896 @item @var{start},+@var{length}
8897 the addresses from @var{start} (inclusive) to
8898 @code{@var{start}+@var{length}} (exclusive).
8902 When 2 arguments are specified, the name of the function is also
8903 printed (since there could be several functions in the given range).
8905 The argument(s) can be any expression yielding a numeric value, such as
8906 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8908 If the range of memory being disassembled contains current program counter,
8909 the instruction at that location is shown with a @code{=>} marker.
8912 The following example shows the disassembly of a range of addresses of
8913 HP PA-RISC 2.0 code:
8916 (@value{GDBP}) disas 0x32c4, 0x32e4
8917 Dump of assembler code from 0x32c4 to 0x32e4:
8918 0x32c4 <main+204>: addil 0,dp
8919 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8920 0x32cc <main+212>: ldil 0x3000,r31
8921 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8922 0x32d4 <main+220>: ldo 0(r31),rp
8923 0x32d8 <main+224>: addil -0x800,dp
8924 0x32dc <main+228>: ldo 0x588(r1),r26
8925 0x32e0 <main+232>: ldil 0x3000,r31
8926 End of assembler dump.
8929 Here is an example showing mixed source+assembly for Intel x86
8930 with @code{/m} or @code{/s}, when the program is stopped just after
8931 function prologue in a non-optimized function with no inline code.
8934 (@value{GDBP}) disas /m main
8935 Dump of assembler code for function main:
8937 0x08048330 <+0>: push %ebp
8938 0x08048331 <+1>: mov %esp,%ebp
8939 0x08048333 <+3>: sub $0x8,%esp
8940 0x08048336 <+6>: and $0xfffffff0,%esp
8941 0x08048339 <+9>: sub $0x10,%esp
8943 6 printf ("Hello.\n");
8944 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8945 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8949 0x08048348 <+24>: mov $0x0,%eax
8950 0x0804834d <+29>: leave
8951 0x0804834e <+30>: ret
8953 End of assembler dump.
8956 The @code{/m} option is deprecated as its output is not useful when
8957 there is either inlined code or re-ordered code.
8958 The @code{/s} option is the preferred choice.
8959 Here is an example for AMD x86-64 showing the difference between
8960 @code{/m} output and @code{/s} output.
8961 This example has one inline function defined in a header file,
8962 and the code is compiled with @samp{-O2} optimization.
8963 Note how the @code{/m} output is missing the disassembly of
8964 several instructions that are present in the @code{/s} output.
8994 (@value{GDBP}) disas /m main
8995 Dump of assembler code for function main:
8999 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9000 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9004 0x000000000040041d <+29>: xor %eax,%eax
9005 0x000000000040041f <+31>: retq
9006 0x0000000000400420 <+32>: add %eax,%eax
9007 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9009 End of assembler dump.
9010 (@value{GDBP}) disas /s main
9011 Dump of assembler code for function main:
9015 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9019 0x0000000000400406 <+6>: test %eax,%eax
9020 0x0000000000400408 <+8>: js 0x400420 <main+32>
9025 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9026 0x000000000040040d <+13>: test %eax,%eax
9027 0x000000000040040f <+15>: mov $0x1,%eax
9028 0x0000000000400414 <+20>: cmovne %edx,%eax
9032 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9036 0x000000000040041d <+29>: xor %eax,%eax
9037 0x000000000040041f <+31>: retq
9041 0x0000000000400420 <+32>: add %eax,%eax
9042 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9043 End of assembler dump.
9046 Here is another example showing raw instructions in hex for AMD x86-64,
9049 (gdb) disas /r 0x400281,+10
9050 Dump of assembler code from 0x400281 to 0x40028b:
9051 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9052 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9053 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9054 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9055 End of assembler dump.
9058 Addresses cannot be specified as a location (@pxref{Specify Location}).
9059 So, for example, if you want to disassemble function @code{bar}
9060 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9061 and not @samp{disassemble foo.c:bar}.
9063 Some architectures have more than one commonly-used set of instruction
9064 mnemonics or other syntax.
9066 For programs that were dynamically linked and use shared libraries,
9067 instructions that call functions or branch to locations in the shared
9068 libraries might show a seemingly bogus location---it's actually a
9069 location of the relocation table. On some architectures, @value{GDBN}
9070 might be able to resolve these to actual function names.
9073 @kindex set disassembler-options
9074 @cindex disassembler options
9075 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9076 This command controls the passing of target specific information to
9077 the disassembler. For a list of valid options, please refer to the
9078 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9079 manual and/or the output of @kbd{objdump --help}
9080 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9081 The default value is the empty string.
9083 If it is necessary to specify more than one disassembler option, then
9084 multiple options can be placed together into a comma separated list.
9085 Currently this command is only supported on targets ARM, MIPS, PowerPC
9088 @kindex show disassembler-options
9089 @item show disassembler-options
9090 Show the current setting of the disassembler options.
9094 @kindex set disassembly-flavor
9095 @cindex Intel disassembly flavor
9096 @cindex AT&T disassembly flavor
9097 @item set disassembly-flavor @var{instruction-set}
9098 Select the instruction set to use when disassembling the
9099 program via the @code{disassemble} or @code{x/i} commands.
9101 Currently this command is only defined for the Intel x86 family. You
9102 can set @var{instruction-set} to either @code{intel} or @code{att}.
9103 The default is @code{att}, the AT&T flavor used by default by Unix
9104 assemblers for x86-based targets.
9106 @kindex show disassembly-flavor
9107 @item show disassembly-flavor
9108 Show the current setting of the disassembly flavor.
9112 @kindex set disassemble-next-line
9113 @kindex show disassemble-next-line
9114 @item set disassemble-next-line
9115 @itemx show disassemble-next-line
9116 Control whether or not @value{GDBN} will disassemble the next source
9117 line or instruction when execution stops. If ON, @value{GDBN} will
9118 display disassembly of the next source line when execution of the
9119 program being debugged stops. This is @emph{in addition} to
9120 displaying the source line itself, which @value{GDBN} always does if
9121 possible. If the next source line cannot be displayed for some reason
9122 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9123 info in the debug info), @value{GDBN} will display disassembly of the
9124 next @emph{instruction} instead of showing the next source line. If
9125 AUTO, @value{GDBN} will display disassembly of next instruction only
9126 if the source line cannot be displayed. This setting causes
9127 @value{GDBN} to display some feedback when you step through a function
9128 with no line info or whose source file is unavailable. The default is
9129 OFF, which means never display the disassembly of the next line or
9135 @chapter Examining Data
9137 @cindex printing data
9138 @cindex examining data
9141 The usual way to examine data in your program is with the @code{print}
9142 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9143 evaluates and prints the value of an expression of the language your
9144 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9145 Different Languages}). It may also print the expression using a
9146 Python-based pretty-printer (@pxref{Pretty Printing}).
9149 @item print @var{expr}
9150 @itemx print /@var{f} @var{expr}
9151 @var{expr} is an expression (in the source language). By default the
9152 value of @var{expr} is printed in a format appropriate to its data type;
9153 you can choose a different format by specifying @samp{/@var{f}}, where
9154 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9158 @itemx print /@var{f}
9159 @cindex reprint the last value
9160 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
9161 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
9162 conveniently inspect the same value in an alternative format.
9165 A more low-level way of examining data is with the @code{x} command.
9166 It examines data in memory at a specified address and prints it in a
9167 specified format. @xref{Memory, ,Examining Memory}.
9169 If you are interested in information about types, or about how the
9170 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
9171 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
9174 @cindex exploring hierarchical data structures
9176 Another way of examining values of expressions and type information is
9177 through the Python extension command @code{explore} (available only if
9178 the @value{GDBN} build is configured with @code{--with-python}). It
9179 offers an interactive way to start at the highest level (or, the most
9180 abstract level) of the data type of an expression (or, the data type
9181 itself) and explore all the way down to leaf scalar values/fields
9182 embedded in the higher level data types.
9185 @item explore @var{arg}
9186 @var{arg} is either an expression (in the source language), or a type
9187 visible in the current context of the program being debugged.
9190 The working of the @code{explore} command can be illustrated with an
9191 example. If a data type @code{struct ComplexStruct} is defined in your
9201 struct ComplexStruct
9203 struct SimpleStruct *ss_p;
9209 followed by variable declarations as
9212 struct SimpleStruct ss = @{ 10, 1.11 @};
9213 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
9217 then, the value of the variable @code{cs} can be explored using the
9218 @code{explore} command as follows.
9222 The value of `cs' is a struct/class of type `struct ComplexStruct' with
9223 the following fields:
9225 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
9226 arr = <Enter 1 to explore this field of type `int [10]'>
9228 Enter the field number of choice:
9232 Since the fields of @code{cs} are not scalar values, you are being
9233 prompted to chose the field you want to explore. Let's say you choose
9234 the field @code{ss_p} by entering @code{0}. Then, since this field is a
9235 pointer, you will be asked if it is pointing to a single value. From
9236 the declaration of @code{cs} above, it is indeed pointing to a single
9237 value, hence you enter @code{y}. If you enter @code{n}, then you will
9238 be asked if it were pointing to an array of values, in which case this
9239 field will be explored as if it were an array.
9242 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
9243 Continue exploring it as a pointer to a single value [y/n]: y
9244 The value of `*(cs.ss_p)' is a struct/class of type `struct
9245 SimpleStruct' with the following fields:
9247 i = 10 .. (Value of type `int')
9248 d = 1.1100000000000001 .. (Value of type `double')
9250 Press enter to return to parent value:
9254 If the field @code{arr} of @code{cs} was chosen for exploration by
9255 entering @code{1} earlier, then since it is as array, you will be
9256 prompted to enter the index of the element in the array that you want
9260 `cs.arr' is an array of `int'.
9261 Enter the index of the element you want to explore in `cs.arr': 5
9263 `(cs.arr)[5]' is a scalar value of type `int'.
9267 Press enter to return to parent value:
9270 In general, at any stage of exploration, you can go deeper towards the
9271 leaf values by responding to the prompts appropriately, or hit the
9272 return key to return to the enclosing data structure (the @i{higher}
9273 level data structure).
9275 Similar to exploring values, you can use the @code{explore} command to
9276 explore types. Instead of specifying a value (which is typically a
9277 variable name or an expression valid in the current context of the
9278 program being debugged), you specify a type name. If you consider the
9279 same example as above, your can explore the type
9280 @code{struct ComplexStruct} by passing the argument
9281 @code{struct ComplexStruct} to the @code{explore} command.
9284 (gdb) explore struct ComplexStruct
9288 By responding to the prompts appropriately in the subsequent interactive
9289 session, you can explore the type @code{struct ComplexStruct} in a
9290 manner similar to how the value @code{cs} was explored in the above
9293 The @code{explore} command also has two sub-commands,
9294 @code{explore value} and @code{explore type}. The former sub-command is
9295 a way to explicitly specify that value exploration of the argument is
9296 being invoked, while the latter is a way to explicitly specify that type
9297 exploration of the argument is being invoked.
9300 @item explore value @var{expr}
9301 @cindex explore value
9302 This sub-command of @code{explore} explores the value of the
9303 expression @var{expr} (if @var{expr} is an expression valid in the
9304 current context of the program being debugged). The behavior of this
9305 command is identical to that of the behavior of the @code{explore}
9306 command being passed the argument @var{expr}.
9308 @item explore type @var{arg}
9309 @cindex explore type
9310 This sub-command of @code{explore} explores the type of @var{arg} (if
9311 @var{arg} is a type visible in the current context of program being
9312 debugged), or the type of the value/expression @var{arg} (if @var{arg}
9313 is an expression valid in the current context of the program being
9314 debugged). If @var{arg} is a type, then the behavior of this command is
9315 identical to that of the @code{explore} command being passed the
9316 argument @var{arg}. If @var{arg} is an expression, then the behavior of
9317 this command will be identical to that of the @code{explore} command
9318 being passed the type of @var{arg} as the argument.
9322 * Expressions:: Expressions
9323 * Ambiguous Expressions:: Ambiguous Expressions
9324 * Variables:: Program variables
9325 * Arrays:: Artificial arrays
9326 * Output Formats:: Output formats
9327 * Memory:: Examining memory
9328 * Auto Display:: Automatic display
9329 * Print Settings:: Print settings
9330 * Pretty Printing:: Python pretty printing
9331 * Value History:: Value history
9332 * Convenience Vars:: Convenience variables
9333 * Convenience Funs:: Convenience functions
9334 * Registers:: Registers
9335 * Floating Point Hardware:: Floating point hardware
9336 * Vector Unit:: Vector Unit
9337 * OS Information:: Auxiliary data provided by operating system
9338 * Memory Region Attributes:: Memory region attributes
9339 * Dump/Restore Files:: Copy between memory and a file
9340 * Core File Generation:: Cause a program dump its core
9341 * Character Sets:: Debugging programs that use a different
9342 character set than GDB does
9343 * Caching Target Data:: Data caching for targets
9344 * Searching Memory:: Searching memory for a sequence of bytes
9345 * Value Sizes:: Managing memory allocated for values
9349 @section Expressions
9352 @code{print} and many other @value{GDBN} commands accept an expression and
9353 compute its value. Any kind of constant, variable or operator defined
9354 by the programming language you are using is valid in an expression in
9355 @value{GDBN}. This includes conditional expressions, function calls,
9356 casts, and string constants. It also includes preprocessor macros, if
9357 you compiled your program to include this information; see
9360 @cindex arrays in expressions
9361 @value{GDBN} supports array constants in expressions input by
9362 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
9363 you can use the command @code{print @{1, 2, 3@}} to create an array
9364 of three integers. If you pass an array to a function or assign it
9365 to a program variable, @value{GDBN} copies the array to memory that
9366 is @code{malloc}ed in the target program.
9368 Because C is so widespread, most of the expressions shown in examples in
9369 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
9370 Languages}, for information on how to use expressions in other
9373 In this section, we discuss operators that you can use in @value{GDBN}
9374 expressions regardless of your programming language.
9376 @cindex casts, in expressions
9377 Casts are supported in all languages, not just in C, because it is so
9378 useful to cast a number into a pointer in order to examine a structure
9379 at that address in memory.
9380 @c FIXME: casts supported---Mod2 true?
9382 @value{GDBN} supports these operators, in addition to those common
9383 to programming languages:
9387 @samp{@@} is a binary operator for treating parts of memory as arrays.
9388 @xref{Arrays, ,Artificial Arrays}, for more information.
9391 @samp{::} allows you to specify a variable in terms of the file or
9392 function where it is defined. @xref{Variables, ,Program Variables}.
9394 @cindex @{@var{type}@}
9395 @cindex type casting memory
9396 @cindex memory, viewing as typed object
9397 @cindex casts, to view memory
9398 @item @{@var{type}@} @var{addr}
9399 Refers to an object of type @var{type} stored at address @var{addr} in
9400 memory. The address @var{addr} may be any expression whose value is
9401 an integer or pointer (but parentheses are required around binary
9402 operators, just as in a cast). This construct is allowed regardless
9403 of what kind of data is normally supposed to reside at @var{addr}.
9406 @node Ambiguous Expressions
9407 @section Ambiguous Expressions
9408 @cindex ambiguous expressions
9410 Expressions can sometimes contain some ambiguous elements. For instance,
9411 some programming languages (notably Ada, C@t{++} and Objective-C) permit
9412 a single function name to be defined several times, for application in
9413 different contexts. This is called @dfn{overloading}. Another example
9414 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
9415 templates and is typically instantiated several times, resulting in
9416 the same function name being defined in different contexts.
9418 In some cases and depending on the language, it is possible to adjust
9419 the expression to remove the ambiguity. For instance in C@t{++}, you
9420 can specify the signature of the function you want to break on, as in
9421 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
9422 qualified name of your function often makes the expression unambiguous
9425 When an ambiguity that needs to be resolved is detected, the debugger
9426 has the capability to display a menu of numbered choices for each
9427 possibility, and then waits for the selection with the prompt @samp{>}.
9428 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9429 aborts the current command. If the command in which the expression was
9430 used allows more than one choice to be selected, the next option in the
9431 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9434 For example, the following session excerpt shows an attempt to set a
9435 breakpoint at the overloaded symbol @code{String::after}.
9436 We choose three particular definitions of that function name:
9438 @c FIXME! This is likely to change to show arg type lists, at least
9441 (@value{GDBP}) b String::after
9444 [2] file:String.cc; line number:867
9445 [3] file:String.cc; line number:860
9446 [4] file:String.cc; line number:875
9447 [5] file:String.cc; line number:853
9448 [6] file:String.cc; line number:846
9449 [7] file:String.cc; line number:735
9451 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9452 Breakpoint 2 at 0xb344: file String.cc, line 875.
9453 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9454 Multiple breakpoints were set.
9455 Use the "delete" command to delete unwanted
9462 @kindex set multiple-symbols
9463 @item set multiple-symbols @var{mode}
9464 @cindex multiple-symbols menu
9466 This option allows you to adjust the debugger behavior when an expression
9469 By default, @var{mode} is set to @code{all}. If the command with which
9470 the expression is used allows more than one choice, then @value{GDBN}
9471 automatically selects all possible choices. For instance, inserting
9472 a breakpoint on a function using an ambiguous name results in a breakpoint
9473 inserted on each possible match. However, if a unique choice must be made,
9474 then @value{GDBN} uses the menu to help you disambiguate the expression.
9475 For instance, printing the address of an overloaded function will result
9476 in the use of the menu.
9478 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9479 when an ambiguity is detected.
9481 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9482 an error due to the ambiguity and the command is aborted.
9484 @kindex show multiple-symbols
9485 @item show multiple-symbols
9486 Show the current value of the @code{multiple-symbols} setting.
9490 @section Program Variables
9492 The most common kind of expression to use is the name of a variable
9495 Variables in expressions are understood in the selected stack frame
9496 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9500 global (or file-static)
9507 visible according to the scope rules of the
9508 programming language from the point of execution in that frame
9511 @noindent This means that in the function
9526 you can examine and use the variable @code{a} whenever your program is
9527 executing within the function @code{foo}, but you can only use or
9528 examine the variable @code{b} while your program is executing inside
9529 the block where @code{b} is declared.
9531 @cindex variable name conflict
9532 There is an exception: you can refer to a variable or function whose
9533 scope is a single source file even if the current execution point is not
9534 in this file. But it is possible to have more than one such variable or
9535 function with the same name (in different source files). If that
9536 happens, referring to that name has unpredictable effects. If you wish,
9537 you can specify a static variable in a particular function or file by
9538 using the colon-colon (@code{::}) notation:
9540 @cindex colon-colon, context for variables/functions
9542 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9543 @cindex @code{::}, context for variables/functions
9546 @var{file}::@var{variable}
9547 @var{function}::@var{variable}
9551 Here @var{file} or @var{function} is the name of the context for the
9552 static @var{variable}. In the case of file names, you can use quotes to
9553 make sure @value{GDBN} parses the file name as a single word---for example,
9554 to print a global value of @code{x} defined in @file{f2.c}:
9557 (@value{GDBP}) p 'f2.c'::x
9560 The @code{::} notation is normally used for referring to
9561 static variables, since you typically disambiguate uses of local variables
9562 in functions by selecting the appropriate frame and using the
9563 simple name of the variable. However, you may also use this notation
9564 to refer to local variables in frames enclosing the selected frame:
9573 process (a); /* Stop here */
9584 For example, if there is a breakpoint at the commented line,
9585 here is what you might see
9586 when the program stops after executing the call @code{bar(0)}:
9591 (@value{GDBP}) p bar::a
9594 #2 0x080483d0 in foo (a=5) at foobar.c:12
9597 (@value{GDBP}) p bar::a
9601 @cindex C@t{++} scope resolution
9602 These uses of @samp{::} are very rarely in conflict with the very
9603 similar use of the same notation in C@t{++}. When they are in
9604 conflict, the C@t{++} meaning takes precedence; however, this can be
9605 overridden by quoting the file or function name with single quotes.
9607 For example, suppose the program is stopped in a method of a class
9608 that has a field named @code{includefile}, and there is also an
9609 include file named @file{includefile} that defines a variable,
9613 (@value{GDBP}) p includefile
9615 (@value{GDBP}) p includefile::some_global
9616 A syntax error in expression, near `'.
9617 (@value{GDBP}) p 'includefile'::some_global
9621 @cindex wrong values
9622 @cindex variable values, wrong
9623 @cindex function entry/exit, wrong values of variables
9624 @cindex optimized code, wrong values of variables
9626 @emph{Warning:} Occasionally, a local variable may appear to have the
9627 wrong value at certain points in a function---just after entry to a new
9628 scope, and just before exit.
9630 You may see this problem when you are stepping by machine instructions.
9631 This is because, on most machines, it takes more than one instruction to
9632 set up a stack frame (including local variable definitions); if you are
9633 stepping by machine instructions, variables may appear to have the wrong
9634 values until the stack frame is completely built. On exit, it usually
9635 also takes more than one machine instruction to destroy a stack frame;
9636 after you begin stepping through that group of instructions, local
9637 variable definitions may be gone.
9639 This may also happen when the compiler does significant optimizations.
9640 To be sure of always seeing accurate values, turn off all optimization
9643 @cindex ``No symbol "foo" in current context''
9644 Another possible effect of compiler optimizations is to optimize
9645 unused variables out of existence, or assign variables to registers (as
9646 opposed to memory addresses). Depending on the support for such cases
9647 offered by the debug info format used by the compiler, @value{GDBN}
9648 might not be able to display values for such local variables. If that
9649 happens, @value{GDBN} will print a message like this:
9652 No symbol "foo" in current context.
9655 To solve such problems, either recompile without optimizations, or use a
9656 different debug info format, if the compiler supports several such
9657 formats. @xref{Compilation}, for more information on choosing compiler
9658 options. @xref{C, ,C and C@t{++}}, for more information about debug
9659 info formats that are best suited to C@t{++} programs.
9661 If you ask to print an object whose contents are unknown to
9662 @value{GDBN}, e.g., because its data type is not completely specified
9663 by the debug information, @value{GDBN} will say @samp{<incomplete
9664 type>}. @xref{Symbols, incomplete type}, for more about this.
9666 @cindex no debug info variables
9667 If you try to examine or use the value of a (global) variable for
9668 which @value{GDBN} has no type information, e.g., because the program
9669 includes no debug information, @value{GDBN} displays an error message.
9670 @xref{Symbols, unknown type}, for more about unknown types. If you
9671 cast the variable to its declared type, @value{GDBN} gets the
9672 variable's value using the cast-to type as the variable's type. For
9673 example, in a C program:
9676 (@value{GDBP}) p var
9677 'var' has unknown type; cast it to its declared type
9678 (@value{GDBP}) p (float) var
9682 If you append @kbd{@@entry} string to a function parameter name you get its
9683 value at the time the function got called. If the value is not available an
9684 error message is printed. Entry values are available only with some compilers.
9685 Entry values are normally also printed at the function parameter list according
9686 to @ref{set print entry-values}.
9689 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9695 (gdb) print i@@entry
9699 Strings are identified as arrays of @code{char} values without specified
9700 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9701 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9702 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9703 defines literal string type @code{"char"} as @code{char} without a sign.
9708 signed char var1[] = "A";
9711 You get during debugging
9716 $2 = @{65 'A', 0 '\0'@}
9720 @section Artificial Arrays
9722 @cindex artificial array
9724 @kindex @@@r{, referencing memory as an array}
9725 It is often useful to print out several successive objects of the
9726 same type in memory; a section of an array, or an array of
9727 dynamically determined size for which only a pointer exists in the
9730 You can do this by referring to a contiguous span of memory as an
9731 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9732 operand of @samp{@@} should be the first element of the desired array
9733 and be an individual object. The right operand should be the desired length
9734 of the array. The result is an array value whose elements are all of
9735 the type of the left argument. The first element is actually the left
9736 argument; the second element comes from bytes of memory immediately
9737 following those that hold the first element, and so on. Here is an
9738 example. If a program says
9741 int *array = (int *) malloc (len * sizeof (int));
9745 you can print the contents of @code{array} with
9751 The left operand of @samp{@@} must reside in memory. Array values made
9752 with @samp{@@} in this way behave just like other arrays in terms of
9753 subscripting, and are coerced to pointers when used in expressions.
9754 Artificial arrays most often appear in expressions via the value history
9755 (@pxref{Value History, ,Value History}), after printing one out.
9757 Another way to create an artificial array is to use a cast.
9758 This re-interprets a value as if it were an array.
9759 The value need not be in memory:
9761 (@value{GDBP}) p/x (short[2])0x12345678
9762 $1 = @{0x1234, 0x5678@}
9765 As a convenience, if you leave the array length out (as in
9766 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9767 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9769 (@value{GDBP}) p/x (short[])0x12345678
9770 $2 = @{0x1234, 0x5678@}
9773 Sometimes the artificial array mechanism is not quite enough; in
9774 moderately complex data structures, the elements of interest may not
9775 actually be adjacent---for example, if you are interested in the values
9776 of pointers in an array. One useful work-around in this situation is
9777 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9778 Variables}) as a counter in an expression that prints the first
9779 interesting value, and then repeat that expression via @key{RET}. For
9780 instance, suppose you have an array @code{dtab} of pointers to
9781 structures, and you are interested in the values of a field @code{fv}
9782 in each structure. Here is an example of what you might type:
9792 @node Output Formats
9793 @section Output Formats
9795 @cindex formatted output
9796 @cindex output formats
9797 By default, @value{GDBN} prints a value according to its data type. Sometimes
9798 this is not what you want. For example, you might want to print a number
9799 in hex, or a pointer in decimal. Or you might want to view data in memory
9800 at a certain address as a character string or as an instruction. To do
9801 these things, specify an @dfn{output format} when you print a value.
9803 The simplest use of output formats is to say how to print a value
9804 already computed. This is done by starting the arguments of the
9805 @code{print} command with a slash and a format letter. The format
9806 letters supported are:
9810 Regard the bits of the value as an integer, and print the integer in
9814 Print as integer in signed decimal.
9817 Print as integer in unsigned decimal.
9820 Print as integer in octal.
9823 Print as integer in binary. The letter @samp{t} stands for ``two''.
9824 @footnote{@samp{b} cannot be used because these format letters are also
9825 used with the @code{x} command, where @samp{b} stands for ``byte'';
9826 see @ref{Memory,,Examining Memory}.}
9829 @cindex unknown address, locating
9830 @cindex locate address
9831 Print as an address, both absolute in hexadecimal and as an offset from
9832 the nearest preceding symbol. You can use this format used to discover
9833 where (in what function) an unknown address is located:
9836 (@value{GDBP}) p/a 0x54320
9837 $3 = 0x54320 <_initialize_vx+396>
9841 The command @code{info symbol 0x54320} yields similar results.
9842 @xref{Symbols, info symbol}.
9845 Regard as an integer and print it as a character constant. This
9846 prints both the numerical value and its character representation. The
9847 character representation is replaced with the octal escape @samp{\nnn}
9848 for characters outside the 7-bit @sc{ascii} range.
9850 Without this format, @value{GDBN} displays @code{char},
9851 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9852 constants. Single-byte members of vectors are displayed as integer
9856 Regard the bits of the value as a floating point number and print
9857 using typical floating point syntax.
9860 @cindex printing strings
9861 @cindex printing byte arrays
9862 Regard as a string, if possible. With this format, pointers to single-byte
9863 data are displayed as null-terminated strings and arrays of single-byte data
9864 are displayed as fixed-length strings. Other values are displayed in their
9867 Without this format, @value{GDBN} displays pointers to and arrays of
9868 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9869 strings. Single-byte members of a vector are displayed as an integer
9873 Like @samp{x} formatting, the value is treated as an integer and
9874 printed as hexadecimal, but leading zeros are printed to pad the value
9875 to the size of the integer type.
9878 @cindex raw printing
9879 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9880 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9881 Printing}). This typically results in a higher-level display of the
9882 value's contents. The @samp{r} format bypasses any Python
9883 pretty-printer which might exist.
9886 For example, to print the program counter in hex (@pxref{Registers}), type
9893 Note that no space is required before the slash; this is because command
9894 names in @value{GDBN} cannot contain a slash.
9896 To reprint the last value in the value history with a different format,
9897 you can use the @code{print} command with just a format and no
9898 expression. For example, @samp{p/x} reprints the last value in hex.
9901 @section Examining Memory
9903 You can use the command @code{x} (for ``examine'') to examine memory in
9904 any of several formats, independently of your program's data types.
9906 @cindex examining memory
9908 @kindex x @r{(examine memory)}
9909 @item x/@var{nfu} @var{addr}
9912 Use the @code{x} command to examine memory.
9915 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9916 much memory to display and how to format it; @var{addr} is an
9917 expression giving the address where you want to start displaying memory.
9918 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9919 Several commands set convenient defaults for @var{addr}.
9922 @item @var{n}, the repeat count
9923 The repeat count is a decimal integer; the default is 1. It specifies
9924 how much memory (counting by units @var{u}) to display. If a negative
9925 number is specified, memory is examined backward from @var{addr}.
9926 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9929 @item @var{f}, the display format
9930 The display format is one of the formats used by @code{print}
9931 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9932 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9933 The default is @samp{x} (hexadecimal) initially. The default changes
9934 each time you use either @code{x} or @code{print}.
9936 @item @var{u}, the unit size
9937 The unit size is any of
9943 Halfwords (two bytes).
9945 Words (four bytes). This is the initial default.
9947 Giant words (eight bytes).
9950 Each time you specify a unit size with @code{x}, that size becomes the
9951 default unit the next time you use @code{x}. For the @samp{i} format,
9952 the unit size is ignored and is normally not written. For the @samp{s} format,
9953 the unit size defaults to @samp{b}, unless it is explicitly given.
9954 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9955 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9956 Note that the results depend on the programming language of the
9957 current compilation unit. If the language is C, the @samp{s}
9958 modifier will use the UTF-16 encoding while @samp{w} will use
9959 UTF-32. The encoding is set by the programming language and cannot
9962 @item @var{addr}, starting display address
9963 @var{addr} is the address where you want @value{GDBN} to begin displaying
9964 memory. The expression need not have a pointer value (though it may);
9965 it is always interpreted as an integer address of a byte of memory.
9966 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9967 @var{addr} is usually just after the last address examined---but several
9968 other commands also set the default address: @code{info breakpoints} (to
9969 the address of the last breakpoint listed), @code{info line} (to the
9970 starting address of a line), and @code{print} (if you use it to display
9971 a value from memory).
9974 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9975 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9976 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9977 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9978 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9980 You can also specify a negative repeat count to examine memory backward
9981 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9982 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9984 Since the letters indicating unit sizes are all distinct from the
9985 letters specifying output formats, you do not have to remember whether
9986 unit size or format comes first; either order works. The output
9987 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9988 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9990 Even though the unit size @var{u} is ignored for the formats @samp{s}
9991 and @samp{i}, you might still want to use a count @var{n}; for example,
9992 @samp{3i} specifies that you want to see three machine instructions,
9993 including any operands. For convenience, especially when used with
9994 the @code{display} command, the @samp{i} format also prints branch delay
9995 slot instructions, if any, beyond the count specified, which immediately
9996 follow the last instruction that is within the count. The command
9997 @code{disassemble} gives an alternative way of inspecting machine
9998 instructions; see @ref{Machine Code,,Source and Machine Code}.
10000 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
10001 the command displays null-terminated strings or instructions before the given
10002 address as many as the absolute value of the given number. For the @samp{i}
10003 format, we use line number information in the debug info to accurately locate
10004 instruction boundaries while disassembling backward. If line info is not
10005 available, the command stops examining memory with an error message.
10007 All the defaults for the arguments to @code{x} are designed to make it
10008 easy to continue scanning memory with minimal specifications each time
10009 you use @code{x}. For example, after you have inspected three machine
10010 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10011 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10012 the repeat count @var{n} is used again; the other arguments default as
10013 for successive uses of @code{x}.
10015 When examining machine instructions, the instruction at current program
10016 counter is shown with a @code{=>} marker. For example:
10019 (@value{GDBP}) x/5i $pc-6
10020 0x804837f <main+11>: mov %esp,%ebp
10021 0x8048381 <main+13>: push %ecx
10022 0x8048382 <main+14>: sub $0x4,%esp
10023 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10024 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10027 @cindex @code{$_}, @code{$__}, and value history
10028 The addresses and contents printed by the @code{x} command are not saved
10029 in the value history because there is often too much of them and they
10030 would get in the way. Instead, @value{GDBN} makes these values available for
10031 subsequent use in expressions as values of the convenience variables
10032 @code{$_} and @code{$__}. After an @code{x} command, the last address
10033 examined is available for use in expressions in the convenience variable
10034 @code{$_}. The contents of that address, as examined, are available in
10035 the convenience variable @code{$__}.
10037 If the @code{x} command has a repeat count, the address and contents saved
10038 are from the last memory unit printed; this is not the same as the last
10039 address printed if several units were printed on the last line of output.
10041 @anchor{addressable memory unit}
10042 @cindex addressable memory unit
10043 Most targets have an addressable memory unit size of 8 bits. This means
10044 that to each memory address are associated 8 bits of data. Some
10045 targets, however, have other addressable memory unit sizes.
10046 Within @value{GDBN} and this document, the term
10047 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
10048 when explicitly referring to a chunk of data of that size. The word
10049 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
10050 the addressable memory unit size of the target. For most systems,
10051 addressable memory unit is a synonym of byte.
10053 @cindex remote memory comparison
10054 @cindex target memory comparison
10055 @cindex verify remote memory image
10056 @cindex verify target memory image
10057 When you are debugging a program running on a remote target machine
10058 (@pxref{Remote Debugging}), you may wish to verify the program's image
10059 in the remote machine's memory against the executable file you
10060 downloaded to the target. Or, on any target, you may want to check
10061 whether the program has corrupted its own read-only sections. The
10062 @code{compare-sections} command is provided for such situations.
10065 @kindex compare-sections
10066 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
10067 Compare the data of a loadable section @var{section-name} in the
10068 executable file of the program being debugged with the same section in
10069 the target machine's memory, and report any mismatches. With no
10070 arguments, compares all loadable sections. With an argument of
10071 @code{-r}, compares all loadable read-only sections.
10073 Note: for remote targets, this command can be accelerated if the
10074 target supports computing the CRC checksum of a block of memory
10075 (@pxref{qCRC packet}).
10079 @section Automatic Display
10080 @cindex automatic display
10081 @cindex display of expressions
10083 If you find that you want to print the value of an expression frequently
10084 (to see how it changes), you might want to add it to the @dfn{automatic
10085 display list} so that @value{GDBN} prints its value each time your program stops.
10086 Each expression added to the list is given a number to identify it;
10087 to remove an expression from the list, you specify that number.
10088 The automatic display looks like this:
10092 3: bar[5] = (struct hack *) 0x3804
10096 This display shows item numbers, expressions and their current values. As with
10097 displays you request manually using @code{x} or @code{print}, you can
10098 specify the output format you prefer; in fact, @code{display} decides
10099 whether to use @code{print} or @code{x} depending your format
10100 specification---it uses @code{x} if you specify either the @samp{i}
10101 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
10105 @item display @var{expr}
10106 Add the expression @var{expr} to the list of expressions to display
10107 each time your program stops. @xref{Expressions, ,Expressions}.
10109 @code{display} does not repeat if you press @key{RET} again after using it.
10111 @item display/@var{fmt} @var{expr}
10112 For @var{fmt} specifying only a display format and not a size or
10113 count, add the expression @var{expr} to the auto-display list but
10114 arrange to display it each time in the specified format @var{fmt}.
10115 @xref{Output Formats,,Output Formats}.
10117 @item display/@var{fmt} @var{addr}
10118 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
10119 number of units, add the expression @var{addr} as a memory address to
10120 be examined each time your program stops. Examining means in effect
10121 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
10124 For example, @samp{display/i $pc} can be helpful, to see the machine
10125 instruction about to be executed each time execution stops (@samp{$pc}
10126 is a common name for the program counter; @pxref{Registers, ,Registers}).
10129 @kindex delete display
10131 @item undisplay @var{dnums}@dots{}
10132 @itemx delete display @var{dnums}@dots{}
10133 Remove items from the list of expressions to display. Specify the
10134 numbers of the displays that you want affected with the command
10135 argument @var{dnums}. It can be a single display number, one of the
10136 numbers shown in the first field of the @samp{info display} display;
10137 or it could be a range of display numbers, as in @code{2-4}.
10139 @code{undisplay} does not repeat if you press @key{RET} after using it.
10140 (Otherwise you would just get the error @samp{No display number @dots{}}.)
10142 @kindex disable display
10143 @item disable display @var{dnums}@dots{}
10144 Disable the display of item numbers @var{dnums}. A disabled display
10145 item is not printed automatically, but is not forgotten. It may be
10146 enabled again later. Specify the numbers of the displays that you
10147 want affected with the command argument @var{dnums}. It can be a
10148 single display number, one of the numbers shown in the first field of
10149 the @samp{info display} display; or it could be a range of display
10150 numbers, as in @code{2-4}.
10152 @kindex enable display
10153 @item enable display @var{dnums}@dots{}
10154 Enable display of item numbers @var{dnums}. It becomes effective once
10155 again in auto display of its expression, until you specify otherwise.
10156 Specify the numbers of the displays that you want affected with the
10157 command argument @var{dnums}. It can be a single display number, one
10158 of the numbers shown in the first field of the @samp{info display}
10159 display; or it could be a range of display numbers, as in @code{2-4}.
10162 Display the current values of the expressions on the list, just as is
10163 done when your program stops.
10165 @kindex info display
10167 Print the list of expressions previously set up to display
10168 automatically, each one with its item number, but without showing the
10169 values. This includes disabled expressions, which are marked as such.
10170 It also includes expressions which would not be displayed right now
10171 because they refer to automatic variables not currently available.
10174 @cindex display disabled out of scope
10175 If a display expression refers to local variables, then it does not make
10176 sense outside the lexical context for which it was set up. Such an
10177 expression is disabled when execution enters a context where one of its
10178 variables is not defined. For example, if you give the command
10179 @code{display last_char} while inside a function with an argument
10180 @code{last_char}, @value{GDBN} displays this argument while your program
10181 continues to stop inside that function. When it stops elsewhere---where
10182 there is no variable @code{last_char}---the display is disabled
10183 automatically. The next time your program stops where @code{last_char}
10184 is meaningful, you can enable the display expression once again.
10186 @node Print Settings
10187 @section Print Settings
10189 @cindex format options
10190 @cindex print settings
10191 @value{GDBN} provides the following ways to control how arrays, structures,
10192 and symbols are printed.
10195 These settings are useful for debugging programs in any language:
10199 @item set print address
10200 @itemx set print address on
10201 @cindex print/don't print memory addresses
10202 @value{GDBN} prints memory addresses showing the location of stack
10203 traces, structure values, pointer values, breakpoints, and so forth,
10204 even when it also displays the contents of those addresses. The default
10205 is @code{on}. For example, this is what a stack frame display looks like with
10206 @code{set print address on}:
10211 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
10213 530 if (lquote != def_lquote)
10217 @item set print address off
10218 Do not print addresses when displaying their contents. For example,
10219 this is the same stack frame displayed with @code{set print address off}:
10223 (@value{GDBP}) set print addr off
10225 #0 set_quotes (lq="<<", rq=">>") at input.c:530
10226 530 if (lquote != def_lquote)
10230 You can use @samp{set print address off} to eliminate all machine
10231 dependent displays from the @value{GDBN} interface. For example, with
10232 @code{print address off}, you should get the same text for backtraces on
10233 all machines---whether or not they involve pointer arguments.
10236 @item show print address
10237 Show whether or not addresses are to be printed.
10240 When @value{GDBN} prints a symbolic address, it normally prints the
10241 closest earlier symbol plus an offset. If that symbol does not uniquely
10242 identify the address (for example, it is a name whose scope is a single
10243 source file), you may need to clarify. One way to do this is with
10244 @code{info line}, for example @samp{info line *0x4537}. Alternately,
10245 you can set @value{GDBN} to print the source file and line number when
10246 it prints a symbolic address:
10249 @item set print symbol-filename on
10250 @cindex source file and line of a symbol
10251 @cindex symbol, source file and line
10252 Tell @value{GDBN} to print the source file name and line number of a
10253 symbol in the symbolic form of an address.
10255 @item set print symbol-filename off
10256 Do not print source file name and line number of a symbol. This is the
10259 @item show print symbol-filename
10260 Show whether or not @value{GDBN} will print the source file name and
10261 line number of a symbol in the symbolic form of an address.
10264 Another situation where it is helpful to show symbol filenames and line
10265 numbers is when disassembling code; @value{GDBN} shows you the line
10266 number and source file that corresponds to each instruction.
10268 Also, you may wish to see the symbolic form only if the address being
10269 printed is reasonably close to the closest earlier symbol:
10272 @item set print max-symbolic-offset @var{max-offset}
10273 @itemx set print max-symbolic-offset unlimited
10274 @cindex maximum value for offset of closest symbol
10275 Tell @value{GDBN} to only display the symbolic form of an address if the
10276 offset between the closest earlier symbol and the address is less than
10277 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
10278 to always print the symbolic form of an address if any symbol precedes
10279 it. Zero is equivalent to @code{unlimited}.
10281 @item show print max-symbolic-offset
10282 Ask how large the maximum offset is that @value{GDBN} prints in a
10286 @cindex wild pointer, interpreting
10287 @cindex pointer, finding referent
10288 If you have a pointer and you are not sure where it points, try
10289 @samp{set print symbol-filename on}. Then you can determine the name
10290 and source file location of the variable where it points, using
10291 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
10292 For example, here @value{GDBN} shows that a variable @code{ptt} points
10293 at another variable @code{t}, defined in @file{hi2.c}:
10296 (@value{GDBP}) set print symbol-filename on
10297 (@value{GDBP}) p/a ptt
10298 $4 = 0xe008 <t in hi2.c>
10302 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
10303 does not show the symbol name and filename of the referent, even with
10304 the appropriate @code{set print} options turned on.
10307 You can also enable @samp{/a}-like formatting all the time using
10308 @samp{set print symbol on}:
10311 @item set print symbol on
10312 Tell @value{GDBN} to print the symbol corresponding to an address, if
10315 @item set print symbol off
10316 Tell @value{GDBN} not to print the symbol corresponding to an
10317 address. In this mode, @value{GDBN} will still print the symbol
10318 corresponding to pointers to functions. This is the default.
10320 @item show print symbol
10321 Show whether @value{GDBN} will display the symbol corresponding to an
10325 Other settings control how different kinds of objects are printed:
10328 @item set print array
10329 @itemx set print array on
10330 @cindex pretty print arrays
10331 Pretty print arrays. This format is more convenient to read,
10332 but uses more space. The default is off.
10334 @item set print array off
10335 Return to compressed format for arrays.
10337 @item show print array
10338 Show whether compressed or pretty format is selected for displaying
10341 @cindex print array indexes
10342 @item set print array-indexes
10343 @itemx set print array-indexes on
10344 Print the index of each element when displaying arrays. May be more
10345 convenient to locate a given element in the array or quickly find the
10346 index of a given element in that printed array. The default is off.
10348 @item set print array-indexes off
10349 Stop printing element indexes when displaying arrays.
10351 @item show print array-indexes
10352 Show whether the index of each element is printed when displaying
10355 @item set print elements @var{number-of-elements}
10356 @itemx set print elements unlimited
10357 @cindex number of array elements to print
10358 @cindex limit on number of printed array elements
10359 Set a limit on how many elements of an array @value{GDBN} will print.
10360 If @value{GDBN} is printing a large array, it stops printing after it has
10361 printed the number of elements set by the @code{set print elements} command.
10362 This limit also applies to the display of strings.
10363 When @value{GDBN} starts, this limit is set to 200.
10364 Setting @var{number-of-elements} to @code{unlimited} or zero means
10365 that the number of elements to print is unlimited.
10367 @item show print elements
10368 Display the number of elements of a large array that @value{GDBN} will print.
10369 If the number is 0, then the printing is unlimited.
10371 @item set print frame-arguments @var{value}
10372 @kindex set print frame-arguments
10373 @cindex printing frame argument values
10374 @cindex print all frame argument values
10375 @cindex print frame argument values for scalars only
10376 @cindex do not print frame argument values
10377 This command allows to control how the values of arguments are printed
10378 when the debugger prints a frame (@pxref{Frames}). The possible
10383 The values of all arguments are printed.
10386 Print the value of an argument only if it is a scalar. The value of more
10387 complex arguments such as arrays, structures, unions, etc, is replaced
10388 by @code{@dots{}}. This is the default. Here is an example where
10389 only scalar arguments are shown:
10392 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
10397 None of the argument values are printed. Instead, the value of each argument
10398 is replaced by @code{@dots{}}. In this case, the example above now becomes:
10401 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
10406 By default, only scalar arguments are printed. This command can be used
10407 to configure the debugger to print the value of all arguments, regardless
10408 of their type. However, it is often advantageous to not print the value
10409 of more complex parameters. For instance, it reduces the amount of
10410 information printed in each frame, making the backtrace more readable.
10411 Also, it improves performance when displaying Ada frames, because
10412 the computation of large arguments can sometimes be CPU-intensive,
10413 especially in large applications. Setting @code{print frame-arguments}
10414 to @code{scalars} (the default) or @code{none} avoids this computation,
10415 thus speeding up the display of each Ada frame.
10417 @item show print frame-arguments
10418 Show how the value of arguments should be displayed when printing a frame.
10420 @item set print raw frame-arguments on
10421 Print frame arguments in raw, non pretty-printed, form.
10423 @item set print raw frame-arguments off
10424 Print frame arguments in pretty-printed form, if there is a pretty-printer
10425 for the value (@pxref{Pretty Printing}),
10426 otherwise print the value in raw form.
10427 This is the default.
10429 @item show print raw frame-arguments
10430 Show whether to print frame arguments in raw form.
10432 @anchor{set print entry-values}
10433 @item set print entry-values @var{value}
10434 @kindex set print entry-values
10435 Set printing of frame argument values at function entry. In some cases
10436 @value{GDBN} can determine the value of function argument which was passed by
10437 the function caller, even if the value was modified inside the called function
10438 and therefore is different. With optimized code, the current value could be
10439 unavailable, but the entry value may still be known.
10441 The default value is @code{default} (see below for its description). Older
10442 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10443 this feature will behave in the @code{default} setting the same way as with the
10446 This functionality is currently supported only by DWARF 2 debugging format and
10447 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10448 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10451 The @var{value} parameter can be one of the following:
10455 Print only actual parameter values, never print values from function entry
10459 #0 different (val=6)
10460 #0 lost (val=<optimized out>)
10462 #0 invalid (val=<optimized out>)
10466 Print only parameter values from function entry point. The actual parameter
10467 values are never printed.
10469 #0 equal (val@@entry=5)
10470 #0 different (val@@entry=5)
10471 #0 lost (val@@entry=5)
10472 #0 born (val@@entry=<optimized out>)
10473 #0 invalid (val@@entry=<optimized out>)
10477 Print only parameter values from function entry point. If value from function
10478 entry point is not known while the actual value is known, print the actual
10479 value for such parameter.
10481 #0 equal (val@@entry=5)
10482 #0 different (val@@entry=5)
10483 #0 lost (val@@entry=5)
10485 #0 invalid (val@@entry=<optimized out>)
10489 Print actual parameter values. If actual parameter value is not known while
10490 value from function entry point is known, print the entry point value for such
10494 #0 different (val=6)
10495 #0 lost (val@@entry=5)
10497 #0 invalid (val=<optimized out>)
10501 Always print both the actual parameter value and its value from function entry
10502 point, even if values of one or both are not available due to compiler
10505 #0 equal (val=5, val@@entry=5)
10506 #0 different (val=6, val@@entry=5)
10507 #0 lost (val=<optimized out>, val@@entry=5)
10508 #0 born (val=10, val@@entry=<optimized out>)
10509 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10513 Print the actual parameter value if it is known and also its value from
10514 function entry point if it is known. If neither is known, print for the actual
10515 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10516 values are known and identical, print the shortened
10517 @code{param=param@@entry=VALUE} notation.
10519 #0 equal (val=val@@entry=5)
10520 #0 different (val=6, val@@entry=5)
10521 #0 lost (val@@entry=5)
10523 #0 invalid (val=<optimized out>)
10527 Always print the actual parameter value. Print also its value from function
10528 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10529 if both values are known and identical, print the shortened
10530 @code{param=param@@entry=VALUE} notation.
10532 #0 equal (val=val@@entry=5)
10533 #0 different (val=6, val@@entry=5)
10534 #0 lost (val=<optimized out>, val@@entry=5)
10536 #0 invalid (val=<optimized out>)
10540 For analysis messages on possible failures of frame argument values at function
10541 entry resolution see @ref{set debug entry-values}.
10543 @item show print entry-values
10544 Show the method being used for printing of frame argument values at function
10547 @item set print repeats @var{number-of-repeats}
10548 @itemx set print repeats unlimited
10549 @cindex repeated array elements
10550 Set the threshold for suppressing display of repeated array
10551 elements. When the number of consecutive identical elements of an
10552 array exceeds the threshold, @value{GDBN} prints the string
10553 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10554 identical repetitions, instead of displaying the identical elements
10555 themselves. Setting the threshold to @code{unlimited} or zero will
10556 cause all elements to be individually printed. The default threshold
10559 @item show print repeats
10560 Display the current threshold for printing repeated identical
10563 @item set print null-stop
10564 @cindex @sc{null} elements in arrays
10565 Cause @value{GDBN} to stop printing the characters of an array when the first
10566 @sc{null} is encountered. This is useful when large arrays actually
10567 contain only short strings.
10568 The default is off.
10570 @item show print null-stop
10571 Show whether @value{GDBN} stops printing an array on the first
10572 @sc{null} character.
10574 @item set print pretty on
10575 @cindex print structures in indented form
10576 @cindex indentation in structure display
10577 Cause @value{GDBN} to print structures in an indented format with one member
10578 per line, like this:
10593 @item set print pretty off
10594 Cause @value{GDBN} to print structures in a compact format, like this:
10598 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10599 meat = 0x54 "Pork"@}
10604 This is the default format.
10606 @item show print pretty
10607 Show which format @value{GDBN} is using to print structures.
10609 @item set print sevenbit-strings on
10610 @cindex eight-bit characters in strings
10611 @cindex octal escapes in strings
10612 Print using only seven-bit characters; if this option is set,
10613 @value{GDBN} displays any eight-bit characters (in strings or
10614 character values) using the notation @code{\}@var{nnn}. This setting is
10615 best if you are working in English (@sc{ascii}) and you use the
10616 high-order bit of characters as a marker or ``meta'' bit.
10618 @item set print sevenbit-strings off
10619 Print full eight-bit characters. This allows the use of more
10620 international character sets, and is the default.
10622 @item show print sevenbit-strings
10623 Show whether or not @value{GDBN} is printing only seven-bit characters.
10625 @item set print union on
10626 @cindex unions in structures, printing
10627 Tell @value{GDBN} to print unions which are contained in structures
10628 and other unions. This is the default setting.
10630 @item set print union off
10631 Tell @value{GDBN} not to print unions which are contained in
10632 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10635 @item show print union
10636 Ask @value{GDBN} whether or not it will print unions which are contained in
10637 structures and other unions.
10639 For example, given the declarations
10642 typedef enum @{Tree, Bug@} Species;
10643 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10644 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10655 struct thing foo = @{Tree, @{Acorn@}@};
10659 with @code{set print union on} in effect @samp{p foo} would print
10662 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10666 and with @code{set print union off} in effect it would print
10669 $1 = @{it = Tree, form = @{...@}@}
10673 @code{set print union} affects programs written in C-like languages
10679 These settings are of interest when debugging C@t{++} programs:
10682 @cindex demangling C@t{++} names
10683 @item set print demangle
10684 @itemx set print demangle on
10685 Print C@t{++} names in their source form rather than in the encoded
10686 (``mangled'') form passed to the assembler and linker for type-safe
10687 linkage. The default is on.
10689 @item show print demangle
10690 Show whether C@t{++} names are printed in mangled or demangled form.
10692 @item set print asm-demangle
10693 @itemx set print asm-demangle on
10694 Print C@t{++} names in their source form rather than their mangled form, even
10695 in assembler code printouts such as instruction disassemblies.
10696 The default is off.
10698 @item show print asm-demangle
10699 Show whether C@t{++} names in assembly listings are printed in mangled
10702 @cindex C@t{++} symbol decoding style
10703 @cindex symbol decoding style, C@t{++}
10704 @kindex set demangle-style
10705 @item set demangle-style @var{style}
10706 Choose among several encoding schemes used by different compilers to represent
10707 C@t{++} names. If you omit @var{style}, you will see a list of possible
10708 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
10709 decoding style by inspecting your program.
10711 @item show demangle-style
10712 Display the encoding style currently in use for decoding C@t{++} symbols.
10714 @item set print object
10715 @itemx set print object on
10716 @cindex derived type of an object, printing
10717 @cindex display derived types
10718 When displaying a pointer to an object, identify the @emph{actual}
10719 (derived) type of the object rather than the @emph{declared} type, using
10720 the virtual function table. Note that the virtual function table is
10721 required---this feature can only work for objects that have run-time
10722 type identification; a single virtual method in the object's declared
10723 type is sufficient. Note that this setting is also taken into account when
10724 working with variable objects via MI (@pxref{GDB/MI}).
10726 @item set print object off
10727 Display only the declared type of objects, without reference to the
10728 virtual function table. This is the default setting.
10730 @item show print object
10731 Show whether actual, or declared, object types are displayed.
10733 @item set print static-members
10734 @itemx set print static-members on
10735 @cindex static members of C@t{++} objects
10736 Print static members when displaying a C@t{++} object. The default is on.
10738 @item set print static-members off
10739 Do not print static members when displaying a C@t{++} object.
10741 @item show print static-members
10742 Show whether C@t{++} static members are printed or not.
10744 @item set print pascal_static-members
10745 @itemx set print pascal_static-members on
10746 @cindex static members of Pascal objects
10747 @cindex Pascal objects, static members display
10748 Print static members when displaying a Pascal object. The default is on.
10750 @item set print pascal_static-members off
10751 Do not print static members when displaying a Pascal object.
10753 @item show print pascal_static-members
10754 Show whether Pascal static members are printed or not.
10756 @c These don't work with HP ANSI C++ yet.
10757 @item set print vtbl
10758 @itemx set print vtbl on
10759 @cindex pretty print C@t{++} virtual function tables
10760 @cindex virtual functions (C@t{++}) display
10761 @cindex VTBL display
10762 Pretty print C@t{++} virtual function tables. The default is off.
10763 (The @code{vtbl} commands do not work on programs compiled with the HP
10764 ANSI C@t{++} compiler (@code{aCC}).)
10766 @item set print vtbl off
10767 Do not pretty print C@t{++} virtual function tables.
10769 @item show print vtbl
10770 Show whether C@t{++} virtual function tables are pretty printed, or not.
10773 @node Pretty Printing
10774 @section Pretty Printing
10776 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10777 Python code. It greatly simplifies the display of complex objects. This
10778 mechanism works for both MI and the CLI.
10781 * Pretty-Printer Introduction:: Introduction to pretty-printers
10782 * Pretty-Printer Example:: An example pretty-printer
10783 * Pretty-Printer Commands:: Pretty-printer commands
10786 @node Pretty-Printer Introduction
10787 @subsection Pretty-Printer Introduction
10789 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10790 registered for the value. If there is then @value{GDBN} invokes the
10791 pretty-printer to print the value. Otherwise the value is printed normally.
10793 Pretty-printers are normally named. This makes them easy to manage.
10794 The @samp{info pretty-printer} command will list all the installed
10795 pretty-printers with their names.
10796 If a pretty-printer can handle multiple data types, then its
10797 @dfn{subprinters} are the printers for the individual data types.
10798 Each such subprinter has its own name.
10799 The format of the name is @var{printer-name};@var{subprinter-name}.
10801 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10802 Typically they are automatically loaded and registered when the corresponding
10803 debug information is loaded, thus making them available without having to
10804 do anything special.
10806 There are three places where a pretty-printer can be registered.
10810 Pretty-printers registered globally are available when debugging
10814 Pretty-printers registered with a program space are available only
10815 when debugging that program.
10816 @xref{Progspaces In Python}, for more details on program spaces in Python.
10819 Pretty-printers registered with an objfile are loaded and unloaded
10820 with the corresponding objfile (e.g., shared library).
10821 @xref{Objfiles In Python}, for more details on objfiles in Python.
10824 @xref{Selecting Pretty-Printers}, for further information on how
10825 pretty-printers are selected,
10827 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10830 @node Pretty-Printer Example
10831 @subsection Pretty-Printer Example
10833 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10836 (@value{GDBP}) print s
10838 static npos = 4294967295,
10840 <std::allocator<char>> = @{
10841 <__gnu_cxx::new_allocator<char>> = @{
10842 <No data fields>@}, <No data fields>
10844 members of std::basic_string<char, std::char_traits<char>,
10845 std::allocator<char> >::_Alloc_hider:
10846 _M_p = 0x804a014 "abcd"
10851 With a pretty-printer for @code{std::string} only the contents are printed:
10854 (@value{GDBP}) print s
10858 @node Pretty-Printer Commands
10859 @subsection Pretty-Printer Commands
10860 @cindex pretty-printer commands
10863 @kindex info pretty-printer
10864 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10865 Print the list of installed pretty-printers.
10866 This includes disabled pretty-printers, which are marked as such.
10868 @var{object-regexp} is a regular expression matching the objects
10869 whose pretty-printers to list.
10870 Objects can be @code{global}, the program space's file
10871 (@pxref{Progspaces In Python}),
10872 and the object files within that program space (@pxref{Objfiles In Python}).
10873 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10874 looks up a printer from these three objects.
10876 @var{name-regexp} is a regular expression matching the name of the printers
10879 @kindex disable pretty-printer
10880 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10881 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10882 A disabled pretty-printer is not forgotten, it may be enabled again later.
10884 @kindex enable pretty-printer
10885 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10886 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10891 Suppose we have three pretty-printers installed: one from library1.so
10892 named @code{foo} that prints objects of type @code{foo}, and
10893 another from library2.so named @code{bar} that prints two types of objects,
10894 @code{bar1} and @code{bar2}.
10897 (gdb) info pretty-printer
10904 (gdb) info pretty-printer library2
10909 (gdb) disable pretty-printer library1
10911 2 of 3 printers enabled
10912 (gdb) info pretty-printer
10919 (gdb) disable pretty-printer library2 bar;bar1
10921 1 of 3 printers enabled
10922 (gdb) info pretty-printer library2
10929 (gdb) disable pretty-printer library2 bar
10931 0 of 3 printers enabled
10932 (gdb) info pretty-printer library2
10941 Note that for @code{bar} the entire printer can be disabled,
10942 as can each individual subprinter.
10944 @node Value History
10945 @section Value History
10947 @cindex value history
10948 @cindex history of values printed by @value{GDBN}
10949 Values printed by the @code{print} command are saved in the @value{GDBN}
10950 @dfn{value history}. This allows you to refer to them in other expressions.
10951 Values are kept until the symbol table is re-read or discarded
10952 (for example with the @code{file} or @code{symbol-file} commands).
10953 When the symbol table changes, the value history is discarded,
10954 since the values may contain pointers back to the types defined in the
10959 @cindex history number
10960 The values printed are given @dfn{history numbers} by which you can
10961 refer to them. These are successive integers starting with one.
10962 @code{print} shows you the history number assigned to a value by
10963 printing @samp{$@var{num} = } before the value; here @var{num} is the
10966 To refer to any previous value, use @samp{$} followed by the value's
10967 history number. The way @code{print} labels its output is designed to
10968 remind you of this. Just @code{$} refers to the most recent value in
10969 the history, and @code{$$} refers to the value before that.
10970 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10971 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10972 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10974 For example, suppose you have just printed a pointer to a structure and
10975 want to see the contents of the structure. It suffices to type
10981 If you have a chain of structures where the component @code{next} points
10982 to the next one, you can print the contents of the next one with this:
10989 You can print successive links in the chain by repeating this
10990 command---which you can do by just typing @key{RET}.
10992 Note that the history records values, not expressions. If the value of
10993 @code{x} is 4 and you type these commands:
11001 then the value recorded in the value history by the @code{print} command
11002 remains 4 even though the value of @code{x} has changed.
11005 @kindex show values
11007 Print the last ten values in the value history, with their item numbers.
11008 This is like @samp{p@ $$9} repeated ten times, except that @code{show
11009 values} does not change the history.
11011 @item show values @var{n}
11012 Print ten history values centered on history item number @var{n}.
11014 @item show values +
11015 Print ten history values just after the values last printed. If no more
11016 values are available, @code{show values +} produces no display.
11019 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
11020 same effect as @samp{show values +}.
11022 @node Convenience Vars
11023 @section Convenience Variables
11025 @cindex convenience variables
11026 @cindex user-defined variables
11027 @value{GDBN} provides @dfn{convenience variables} that you can use within
11028 @value{GDBN} to hold on to a value and refer to it later. These variables
11029 exist entirely within @value{GDBN}; they are not part of your program, and
11030 setting a convenience variable has no direct effect on further execution
11031 of your program. That is why you can use them freely.
11033 Convenience variables are prefixed with @samp{$}. Any name preceded by
11034 @samp{$} can be used for a convenience variable, unless it is one of
11035 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
11036 (Value history references, in contrast, are @emph{numbers} preceded
11037 by @samp{$}. @xref{Value History, ,Value History}.)
11039 You can save a value in a convenience variable with an assignment
11040 expression, just as you would set a variable in your program.
11044 set $foo = *object_ptr
11048 would save in @code{$foo} the value contained in the object pointed to by
11051 Using a convenience variable for the first time creates it, but its
11052 value is @code{void} until you assign a new value. You can alter the
11053 value with another assignment at any time.
11055 Convenience variables have no fixed types. You can assign a convenience
11056 variable any type of value, including structures and arrays, even if
11057 that variable already has a value of a different type. The convenience
11058 variable, when used as an expression, has the type of its current value.
11061 @kindex show convenience
11062 @cindex show all user variables and functions
11063 @item show convenience
11064 Print a list of convenience variables used so far, and their values,
11065 as well as a list of the convenience functions.
11066 Abbreviated @code{show conv}.
11068 @kindex init-if-undefined
11069 @cindex convenience variables, initializing
11070 @item init-if-undefined $@var{variable} = @var{expression}
11071 Set a convenience variable if it has not already been set. This is useful
11072 for user-defined commands that keep some state. It is similar, in concept,
11073 to using local static variables with initializers in C (except that
11074 convenience variables are global). It can also be used to allow users to
11075 override default values used in a command script.
11077 If the variable is already defined then the expression is not evaluated so
11078 any side-effects do not occur.
11081 One of the ways to use a convenience variable is as a counter to be
11082 incremented or a pointer to be advanced. For example, to print
11083 a field from successive elements of an array of structures:
11087 print bar[$i++]->contents
11091 Repeat that command by typing @key{RET}.
11093 Some convenience variables are created automatically by @value{GDBN} and given
11094 values likely to be useful.
11097 @vindex $_@r{, convenience variable}
11099 The variable @code{$_} is automatically set by the @code{x} command to
11100 the last address examined (@pxref{Memory, ,Examining Memory}). Other
11101 commands which provide a default address for @code{x} to examine also
11102 set @code{$_} to that address; these commands include @code{info line}
11103 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
11104 except when set by the @code{x} command, in which case it is a pointer
11105 to the type of @code{$__}.
11107 @vindex $__@r{, convenience variable}
11109 The variable @code{$__} is automatically set by the @code{x} command
11110 to the value found in the last address examined. Its type is chosen
11111 to match the format in which the data was printed.
11114 @vindex $_exitcode@r{, convenience variable}
11115 When the program being debugged terminates normally, @value{GDBN}
11116 automatically sets this variable to the exit code of the program, and
11117 resets @code{$_exitsignal} to @code{void}.
11120 @vindex $_exitsignal@r{, convenience variable}
11121 When the program being debugged dies due to an uncaught signal,
11122 @value{GDBN} automatically sets this variable to that signal's number,
11123 and resets @code{$_exitcode} to @code{void}.
11125 To distinguish between whether the program being debugged has exited
11126 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
11127 @code{$_exitsignal} is not @code{void}), the convenience function
11128 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
11129 Functions}). For example, considering the following source code:
11132 #include <signal.h>
11135 main (int argc, char *argv[])
11142 A valid way of telling whether the program being debugged has exited
11143 or signalled would be:
11146 (@value{GDBP}) define has_exited_or_signalled
11147 Type commands for definition of ``has_exited_or_signalled''.
11148 End with a line saying just ``end''.
11149 >if $_isvoid ($_exitsignal)
11150 >echo The program has exited\n
11152 >echo The program has signalled\n
11158 Program terminated with signal SIGALRM, Alarm clock.
11159 The program no longer exists.
11160 (@value{GDBP}) has_exited_or_signalled
11161 The program has signalled
11164 As can be seen, @value{GDBN} correctly informs that the program being
11165 debugged has signalled, since it calls @code{raise} and raises a
11166 @code{SIGALRM} signal. If the program being debugged had not called
11167 @code{raise}, then @value{GDBN} would report a normal exit:
11170 (@value{GDBP}) has_exited_or_signalled
11171 The program has exited
11175 The variable @code{$_exception} is set to the exception object being
11176 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
11179 @itemx $_probe_arg0@dots{}$_probe_arg11
11180 Arguments to a static probe. @xref{Static Probe Points}.
11183 @vindex $_sdata@r{, inspect, convenience variable}
11184 The variable @code{$_sdata} contains extra collected static tracepoint
11185 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
11186 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
11187 if extra static tracepoint data has not been collected.
11190 @vindex $_siginfo@r{, convenience variable}
11191 The variable @code{$_siginfo} contains extra signal information
11192 (@pxref{extra signal information}). Note that @code{$_siginfo}
11193 could be empty, if the application has not yet received any signals.
11194 For example, it will be empty before you execute the @code{run} command.
11197 @vindex $_tlb@r{, convenience variable}
11198 The variable @code{$_tlb} is automatically set when debugging
11199 applications running on MS-Windows in native mode or connected to
11200 gdbserver that supports the @code{qGetTIBAddr} request.
11201 @xref{General Query Packets}.
11202 This variable contains the address of the thread information block.
11205 The number of the current inferior. @xref{Inferiors and
11206 Programs, ,Debugging Multiple Inferiors and Programs}.
11209 The thread number of the current thread. @xref{thread numbers}.
11212 The global number of the current thread. @xref{global thread numbers}.
11216 @vindex $_gdb_major@r{, convenience variable}
11217 @vindex $_gdb_minor@r{, convenience variable}
11218 The major and minor version numbers of the running @value{GDBN}.
11219 Development snapshots and pretest versions have their minor version
11220 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
11221 the value 12 for @code{$_gdb_minor}. These variables allow you to
11222 write scripts that work with different versions of @value{GDBN}
11223 without errors caused by features unavailable in some of those
11227 @node Convenience Funs
11228 @section Convenience Functions
11230 @cindex convenience functions
11231 @value{GDBN} also supplies some @dfn{convenience functions}. These
11232 have a syntax similar to convenience variables. A convenience
11233 function can be used in an expression just like an ordinary function;
11234 however, a convenience function is implemented internally to
11237 These functions do not require @value{GDBN} to be configured with
11238 @code{Python} support, which means that they are always available.
11242 @item $_isvoid (@var{expr})
11243 @findex $_isvoid@r{, convenience function}
11244 Return one if the expression @var{expr} is @code{void}. Otherwise it
11247 A @code{void} expression is an expression where the type of the result
11248 is @code{void}. For example, you can examine a convenience variable
11249 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
11253 (@value{GDBP}) print $_exitcode
11255 (@value{GDBP}) print $_isvoid ($_exitcode)
11258 Starting program: ./a.out
11259 [Inferior 1 (process 29572) exited normally]
11260 (@value{GDBP}) print $_exitcode
11262 (@value{GDBP}) print $_isvoid ($_exitcode)
11266 In the example above, we used @code{$_isvoid} to check whether
11267 @code{$_exitcode} is @code{void} before and after the execution of the
11268 program being debugged. Before the execution there is no exit code to
11269 be examined, therefore @code{$_exitcode} is @code{void}. After the
11270 execution the program being debugged returned zero, therefore
11271 @code{$_exitcode} is zero, which means that it is not @code{void}
11274 The @code{void} expression can also be a call of a function from the
11275 program being debugged. For example, given the following function:
11284 The result of calling it inside @value{GDBN} is @code{void}:
11287 (@value{GDBP}) print foo ()
11289 (@value{GDBP}) print $_isvoid (foo ())
11291 (@value{GDBP}) set $v = foo ()
11292 (@value{GDBP}) print $v
11294 (@value{GDBP}) print $_isvoid ($v)
11300 These functions require @value{GDBN} to be configured with
11301 @code{Python} support.
11305 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
11306 @findex $_memeq@r{, convenience function}
11307 Returns one if the @var{length} bytes at the addresses given by
11308 @var{buf1} and @var{buf2} are equal.
11309 Otherwise it returns zero.
11311 @item $_regex(@var{str}, @var{regex})
11312 @findex $_regex@r{, convenience function}
11313 Returns one if the string @var{str} matches the regular expression
11314 @var{regex}. Otherwise it returns zero.
11315 The syntax of the regular expression is that specified by @code{Python}'s
11316 regular expression support.
11318 @item $_streq(@var{str1}, @var{str2})
11319 @findex $_streq@r{, convenience function}
11320 Returns one if the strings @var{str1} and @var{str2} are equal.
11321 Otherwise it returns zero.
11323 @item $_strlen(@var{str})
11324 @findex $_strlen@r{, convenience function}
11325 Returns the length of string @var{str}.
11327 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11328 @findex $_caller_is@r{, convenience function}
11329 Returns one if the calling function's name is equal to @var{name}.
11330 Otherwise it returns zero.
11332 If the optional argument @var{number_of_frames} is provided,
11333 it is the number of frames up in the stack to look.
11341 at testsuite/gdb.python/py-caller-is.c:21
11342 #1 0x00000000004005a0 in middle_func ()
11343 at testsuite/gdb.python/py-caller-is.c:27
11344 #2 0x00000000004005ab in top_func ()
11345 at testsuite/gdb.python/py-caller-is.c:33
11346 #3 0x00000000004005b6 in main ()
11347 at testsuite/gdb.python/py-caller-is.c:39
11348 (gdb) print $_caller_is ("middle_func")
11350 (gdb) print $_caller_is ("top_func", 2)
11354 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11355 @findex $_caller_matches@r{, convenience function}
11356 Returns one if the calling function's name matches the regular expression
11357 @var{regexp}. Otherwise it returns zero.
11359 If the optional argument @var{number_of_frames} is provided,
11360 it is the number of frames up in the stack to look.
11363 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11364 @findex $_any_caller_is@r{, convenience function}
11365 Returns one if any calling function's name is equal to @var{name}.
11366 Otherwise it returns zero.
11368 If the optional argument @var{number_of_frames} is provided,
11369 it is the number of frames up in the stack to look.
11372 This function differs from @code{$_caller_is} in that this function
11373 checks all stack frames from the immediate caller to the frame specified
11374 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
11375 frame specified by @var{number_of_frames}.
11377 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11378 @findex $_any_caller_matches@r{, convenience function}
11379 Returns one if any calling function's name matches the regular expression
11380 @var{regexp}. Otherwise it returns zero.
11382 If the optional argument @var{number_of_frames} is provided,
11383 it is the number of frames up in the stack to look.
11386 This function differs from @code{$_caller_matches} in that this function
11387 checks all stack frames from the immediate caller to the frame specified
11388 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
11389 frame specified by @var{number_of_frames}.
11391 @item $_as_string(@var{value})
11392 @findex $_as_string@r{, convenience function}
11393 Return the string representation of @var{value}.
11395 This function is useful to obtain the textual label (enumerator) of an
11396 enumeration value. For example, assuming the variable @var{node} is of
11397 an enumerated type:
11400 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
11401 Visiting node of type NODE_INTEGER
11404 @item $_cimag(@var{value})
11405 @itemx $_creal(@var{value})
11406 @findex $_cimag@r{, convenience function}
11407 @findex $_creal@r{, convenience function}
11408 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
11409 the complex number @var{value}.
11411 The type of the imaginary or real part depends on the type of the
11412 complex number, e.g., using @code{$_cimag} on a @code{float complex}
11413 will return an imaginary part of type @code{float}.
11417 @value{GDBN} provides the ability to list and get help on
11418 convenience functions.
11421 @item help function
11422 @kindex help function
11423 @cindex show all convenience functions
11424 Print a list of all convenience functions.
11431 You can refer to machine register contents, in expressions, as variables
11432 with names starting with @samp{$}. The names of registers are different
11433 for each machine; use @code{info registers} to see the names used on
11437 @kindex info registers
11438 @item info registers
11439 Print the names and values of all registers except floating-point
11440 and vector registers (in the selected stack frame).
11442 @kindex info all-registers
11443 @cindex floating point registers
11444 @item info all-registers
11445 Print the names and values of all registers, including floating-point
11446 and vector registers (in the selected stack frame).
11448 @item info registers @var{reggroup} @dots{}
11449 Print the name and value of the registers in each of the specified
11450 @var{reggroup}s. The @var{reggoup} can be any of those returned by
11451 @code{maint print reggroups} (@pxref{Maintenance Commands}).
11453 @item info registers @var{regname} @dots{}
11454 Print the @dfn{relativized} value of each specified register @var{regname}.
11455 As discussed in detail below, register values are normally relative to
11456 the selected stack frame. The @var{regname} may be any register name valid on
11457 the machine you are using, with or without the initial @samp{$}.
11460 @anchor{standard registers}
11461 @cindex stack pointer register
11462 @cindex program counter register
11463 @cindex process status register
11464 @cindex frame pointer register
11465 @cindex standard registers
11466 @value{GDBN} has four ``standard'' register names that are available (in
11467 expressions) on most machines---whenever they do not conflict with an
11468 architecture's canonical mnemonics for registers. The register names
11469 @code{$pc} and @code{$sp} are used for the program counter register and
11470 the stack pointer. @code{$fp} is used for a register that contains a
11471 pointer to the current stack frame, and @code{$ps} is used for a
11472 register that contains the processor status. For example,
11473 you could print the program counter in hex with
11480 or print the instruction to be executed next with
11487 or add four to the stack pointer@footnote{This is a way of removing
11488 one word from the stack, on machines where stacks grow downward in
11489 memory (most machines, nowadays). This assumes that the innermost
11490 stack frame is selected; setting @code{$sp} is not allowed when other
11491 stack frames are selected. To pop entire frames off the stack,
11492 regardless of machine architecture, use @code{return};
11493 see @ref{Returning, ,Returning from a Function}.} with
11499 Whenever possible, these four standard register names are available on
11500 your machine even though the machine has different canonical mnemonics,
11501 so long as there is no conflict. The @code{info registers} command
11502 shows the canonical names. For example, on the SPARC, @code{info
11503 registers} displays the processor status register as @code{$psr} but you
11504 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11505 is an alias for the @sc{eflags} register.
11507 @value{GDBN} always considers the contents of an ordinary register as an
11508 integer when the register is examined in this way. Some machines have
11509 special registers which can hold nothing but floating point; these
11510 registers are considered to have floating point values. There is no way
11511 to refer to the contents of an ordinary register as floating point value
11512 (although you can @emph{print} it as a floating point value with
11513 @samp{print/f $@var{regname}}).
11515 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11516 means that the data format in which the register contents are saved by
11517 the operating system is not the same one that your program normally
11518 sees. For example, the registers of the 68881 floating point
11519 coprocessor are always saved in ``extended'' (raw) format, but all C
11520 programs expect to work with ``double'' (virtual) format. In such
11521 cases, @value{GDBN} normally works with the virtual format only (the format
11522 that makes sense for your program), but the @code{info registers} command
11523 prints the data in both formats.
11525 @cindex SSE registers (x86)
11526 @cindex MMX registers (x86)
11527 Some machines have special registers whose contents can be interpreted
11528 in several different ways. For example, modern x86-based machines
11529 have SSE and MMX registers that can hold several values packed
11530 together in several different formats. @value{GDBN} refers to such
11531 registers in @code{struct} notation:
11534 (@value{GDBP}) print $xmm1
11536 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11537 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11538 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11539 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11540 v4_int32 = @{0, 20657912, 11, 13@},
11541 v2_int64 = @{88725056443645952, 55834574859@},
11542 uint128 = 0x0000000d0000000b013b36f800000000
11547 To set values of such registers, you need to tell @value{GDBN} which
11548 view of the register you wish to change, as if you were assigning
11549 value to a @code{struct} member:
11552 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11555 Normally, register values are relative to the selected stack frame
11556 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11557 value that the register would contain if all stack frames farther in
11558 were exited and their saved registers restored. In order to see the
11559 true contents of hardware registers, you must select the innermost
11560 frame (with @samp{frame 0}).
11562 @cindex caller-saved registers
11563 @cindex call-clobbered registers
11564 @cindex volatile registers
11565 @cindex <not saved> values
11566 Usually ABIs reserve some registers as not needed to be saved by the
11567 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11568 registers). It may therefore not be possible for @value{GDBN} to know
11569 the value a register had before the call (in other words, in the outer
11570 frame), if the register value has since been changed by the callee.
11571 @value{GDBN} tries to deduce where the inner frame saved
11572 (``callee-saved'') registers, from the debug info, unwind info, or the
11573 machine code generated by your compiler. If some register is not
11574 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11575 its own knowledge of the ABI, or because the debug/unwind info
11576 explicitly says the register's value is undefined), @value{GDBN}
11577 displays @w{@samp{<not saved>}} as the register's value. With targets
11578 that @value{GDBN} has no knowledge of the register saving convention,
11579 if a register was not saved by the callee, then its value and location
11580 in the outer frame are assumed to be the same of the inner frame.
11581 This is usually harmless, because if the register is call-clobbered,
11582 the caller either does not care what is in the register after the
11583 call, or has code to restore the value that it does care about. Note,
11584 however, that if you change such a register in the outer frame, you
11585 may also be affecting the inner frame. Also, the more ``outer'' the
11586 frame is you're looking at, the more likely a call-clobbered
11587 register's value is to be wrong, in the sense that it doesn't actually
11588 represent the value the register had just before the call.
11590 @node Floating Point Hardware
11591 @section Floating Point Hardware
11592 @cindex floating point
11594 Depending on the configuration, @value{GDBN} may be able to give
11595 you more information about the status of the floating point hardware.
11600 Display hardware-dependent information about the floating
11601 point unit. The exact contents and layout vary depending on the
11602 floating point chip. Currently, @samp{info float} is supported on
11603 the ARM and x86 machines.
11607 @section Vector Unit
11608 @cindex vector unit
11610 Depending on the configuration, @value{GDBN} may be able to give you
11611 more information about the status of the vector unit.
11614 @kindex info vector
11616 Display information about the vector unit. The exact contents and
11617 layout vary depending on the hardware.
11620 @node OS Information
11621 @section Operating System Auxiliary Information
11622 @cindex OS information
11624 @value{GDBN} provides interfaces to useful OS facilities that can help
11625 you debug your program.
11627 @cindex auxiliary vector
11628 @cindex vector, auxiliary
11629 Some operating systems supply an @dfn{auxiliary vector} to programs at
11630 startup. This is akin to the arguments and environment that you
11631 specify for a program, but contains a system-dependent variety of
11632 binary values that tell system libraries important details about the
11633 hardware, operating system, and process. Each value's purpose is
11634 identified by an integer tag; the meanings are well-known but system-specific.
11635 Depending on the configuration and operating system facilities,
11636 @value{GDBN} may be able to show you this information. For remote
11637 targets, this functionality may further depend on the remote stub's
11638 support of the @samp{qXfer:auxv:read} packet, see
11639 @ref{qXfer auxiliary vector read}.
11644 Display the auxiliary vector of the inferior, which can be either a
11645 live process or a core dump file. @value{GDBN} prints each tag value
11646 numerically, and also shows names and text descriptions for recognized
11647 tags. Some values in the vector are numbers, some bit masks, and some
11648 pointers to strings or other data. @value{GDBN} displays each value in the
11649 most appropriate form for a recognized tag, and in hexadecimal for
11650 an unrecognized tag.
11653 On some targets, @value{GDBN} can access operating system-specific
11654 information and show it to you. The types of information available
11655 will differ depending on the type of operating system running on the
11656 target. The mechanism used to fetch the data is described in
11657 @ref{Operating System Information}. For remote targets, this
11658 functionality depends on the remote stub's support of the
11659 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11663 @item info os @var{infotype}
11665 Display OS information of the requested type.
11667 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11669 @anchor{linux info os infotypes}
11671 @kindex info os cpus
11673 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11674 the available fields from /proc/cpuinfo. For each supported architecture
11675 different fields are available. Two common entries are processor which gives
11676 CPU number and bogomips; a system constant that is calculated during
11677 kernel initialization.
11679 @kindex info os files
11681 Display the list of open file descriptors on the target. For each
11682 file descriptor, @value{GDBN} prints the identifier of the process
11683 owning the descriptor, the command of the owning process, the value
11684 of the descriptor, and the target of the descriptor.
11686 @kindex info os modules
11688 Display the list of all loaded kernel modules on the target. For each
11689 module, @value{GDBN} prints the module name, the size of the module in
11690 bytes, the number of times the module is used, the dependencies of the
11691 module, the status of the module, and the address of the loaded module
11694 @kindex info os msg
11696 Display the list of all System V message queues on the target. For each
11697 message queue, @value{GDBN} prints the message queue key, the message
11698 queue identifier, the access permissions, the current number of bytes
11699 on the queue, the current number of messages on the queue, the processes
11700 that last sent and received a message on the queue, the user and group
11701 of the owner and creator of the message queue, the times at which a
11702 message was last sent and received on the queue, and the time at which
11703 the message queue was last changed.
11705 @kindex info os processes
11707 Display the list of processes on the target. For each process,
11708 @value{GDBN} prints the process identifier, the name of the user, the
11709 command corresponding to the process, and the list of processor cores
11710 that the process is currently running on. (To understand what these
11711 properties mean, for this and the following info types, please consult
11712 the general @sc{gnu}/Linux documentation.)
11714 @kindex info os procgroups
11716 Display the list of process groups on the target. For each process,
11717 @value{GDBN} prints the identifier of the process group that it belongs
11718 to, the command corresponding to the process group leader, the process
11719 identifier, and the command line of the process. The list is sorted
11720 first by the process group identifier, then by the process identifier,
11721 so that processes belonging to the same process group are grouped together
11722 and the process group leader is listed first.
11724 @kindex info os semaphores
11726 Display the list of all System V semaphore sets on the target. For each
11727 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11728 set identifier, the access permissions, the number of semaphores in the
11729 set, the user and group of the owner and creator of the semaphore set,
11730 and the times at which the semaphore set was operated upon and changed.
11732 @kindex info os shm
11734 Display the list of all System V shared-memory regions on the target.
11735 For each shared-memory region, @value{GDBN} prints the region key,
11736 the shared-memory identifier, the access permissions, the size of the
11737 region, the process that created the region, the process that last
11738 attached to or detached from the region, the current number of live
11739 attaches to the region, and the times at which the region was last
11740 attached to, detach from, and changed.
11742 @kindex info os sockets
11744 Display the list of Internet-domain sockets on the target. For each
11745 socket, @value{GDBN} prints the address and port of the local and
11746 remote endpoints, the current state of the connection, the creator of
11747 the socket, the IP address family of the socket, and the type of the
11750 @kindex info os threads
11752 Display the list of threads running on the target. For each thread,
11753 @value{GDBN} prints the identifier of the process that the thread
11754 belongs to, the command of the process, the thread identifier, and the
11755 processor core that it is currently running on. The main thread of a
11756 process is not listed.
11760 If @var{infotype} is omitted, then list the possible values for
11761 @var{infotype} and the kind of OS information available for each
11762 @var{infotype}. If the target does not return a list of possible
11763 types, this command will report an error.
11766 @node Memory Region Attributes
11767 @section Memory Region Attributes
11768 @cindex memory region attributes
11770 @dfn{Memory region attributes} allow you to describe special handling
11771 required by regions of your target's memory. @value{GDBN} uses
11772 attributes to determine whether to allow certain types of memory
11773 accesses; whether to use specific width accesses; and whether to cache
11774 target memory. By default the description of memory regions is
11775 fetched from the target (if the current target supports this), but the
11776 user can override the fetched regions.
11778 Defined memory regions can be individually enabled and disabled. When a
11779 memory region is disabled, @value{GDBN} uses the default attributes when
11780 accessing memory in that region. Similarly, if no memory regions have
11781 been defined, @value{GDBN} uses the default attributes when accessing
11784 When a memory region is defined, it is given a number to identify it;
11785 to enable, disable, or remove a memory region, you specify that number.
11789 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11790 Define a memory region bounded by @var{lower} and @var{upper} with
11791 attributes @var{attributes}@dots{}, and add it to the list of regions
11792 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11793 case: it is treated as the target's maximum memory address.
11794 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11797 Discard any user changes to the memory regions and use target-supplied
11798 regions, if available, or no regions if the target does not support.
11801 @item delete mem @var{nums}@dots{}
11802 Remove memory regions @var{nums}@dots{} from the list of regions
11803 monitored by @value{GDBN}.
11805 @kindex disable mem
11806 @item disable mem @var{nums}@dots{}
11807 Disable monitoring of memory regions @var{nums}@dots{}.
11808 A disabled memory region is not forgotten.
11809 It may be enabled again later.
11812 @item enable mem @var{nums}@dots{}
11813 Enable monitoring of memory regions @var{nums}@dots{}.
11817 Print a table of all defined memory regions, with the following columns
11821 @item Memory Region Number
11822 @item Enabled or Disabled.
11823 Enabled memory regions are marked with @samp{y}.
11824 Disabled memory regions are marked with @samp{n}.
11827 The address defining the inclusive lower bound of the memory region.
11830 The address defining the exclusive upper bound of the memory region.
11833 The list of attributes set for this memory region.
11838 @subsection Attributes
11840 @subsubsection Memory Access Mode
11841 The access mode attributes set whether @value{GDBN} may make read or
11842 write accesses to a memory region.
11844 While these attributes prevent @value{GDBN} from performing invalid
11845 memory accesses, they do nothing to prevent the target system, I/O DMA,
11846 etc.@: from accessing memory.
11850 Memory is read only.
11852 Memory is write only.
11854 Memory is read/write. This is the default.
11857 @subsubsection Memory Access Size
11858 The access size attribute tells @value{GDBN} to use specific sized
11859 accesses in the memory region. Often memory mapped device registers
11860 require specific sized accesses. If no access size attribute is
11861 specified, @value{GDBN} may use accesses of any size.
11865 Use 8 bit memory accesses.
11867 Use 16 bit memory accesses.
11869 Use 32 bit memory accesses.
11871 Use 64 bit memory accesses.
11874 @c @subsubsection Hardware/Software Breakpoints
11875 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11876 @c will use hardware or software breakpoints for the internal breakpoints
11877 @c used by the step, next, finish, until, etc. commands.
11881 @c Always use hardware breakpoints
11882 @c @item swbreak (default)
11885 @subsubsection Data Cache
11886 The data cache attributes set whether @value{GDBN} will cache target
11887 memory. While this generally improves performance by reducing debug
11888 protocol overhead, it can lead to incorrect results because @value{GDBN}
11889 does not know about volatile variables or memory mapped device
11894 Enable @value{GDBN} to cache target memory.
11896 Disable @value{GDBN} from caching target memory. This is the default.
11899 @subsection Memory Access Checking
11900 @value{GDBN} can be instructed to refuse accesses to memory that is
11901 not explicitly described. This can be useful if accessing such
11902 regions has undesired effects for a specific target, or to provide
11903 better error checking. The following commands control this behaviour.
11906 @kindex set mem inaccessible-by-default
11907 @item set mem inaccessible-by-default [on|off]
11908 If @code{on} is specified, make @value{GDBN} treat memory not
11909 explicitly described by the memory ranges as non-existent and refuse accesses
11910 to such memory. The checks are only performed if there's at least one
11911 memory range defined. If @code{off} is specified, make @value{GDBN}
11912 treat the memory not explicitly described by the memory ranges as RAM.
11913 The default value is @code{on}.
11914 @kindex show mem inaccessible-by-default
11915 @item show mem inaccessible-by-default
11916 Show the current handling of accesses to unknown memory.
11920 @c @subsubsection Memory Write Verification
11921 @c The memory write verification attributes set whether @value{GDBN}
11922 @c will re-reads data after each write to verify the write was successful.
11926 @c @item noverify (default)
11929 @node Dump/Restore Files
11930 @section Copy Between Memory and a File
11931 @cindex dump/restore files
11932 @cindex append data to a file
11933 @cindex dump data to a file
11934 @cindex restore data from a file
11936 You can use the commands @code{dump}, @code{append}, and
11937 @code{restore} to copy data between target memory and a file. The
11938 @code{dump} and @code{append} commands write data to a file, and the
11939 @code{restore} command reads data from a file back into the inferior's
11940 memory. Files may be in binary, Motorola S-record, Intel hex,
11941 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11942 append to binary files, and cannot read from Verilog Hex files.
11947 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11948 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11949 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11950 or the value of @var{expr}, to @var{filename} in the given format.
11952 The @var{format} parameter may be any one of:
11959 Motorola S-record format.
11961 Tektronix Hex format.
11963 Verilog Hex format.
11966 @value{GDBN} uses the same definitions of these formats as the
11967 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11968 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11972 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11973 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11974 Append the contents of memory from @var{start_addr} to @var{end_addr},
11975 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11976 (@value{GDBN} can only append data to files in raw binary form.)
11979 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11980 Restore the contents of file @var{filename} into memory. The
11981 @code{restore} command can automatically recognize any known @sc{bfd}
11982 file format, except for raw binary. To restore a raw binary file you
11983 must specify the optional keyword @code{binary} after the filename.
11985 If @var{bias} is non-zero, its value will be added to the addresses
11986 contained in the file. Binary files always start at address zero, so
11987 they will be restored at address @var{bias}. Other bfd files have
11988 a built-in location; they will be restored at offset @var{bias}
11989 from that location.
11991 If @var{start} and/or @var{end} are non-zero, then only data between
11992 file offset @var{start} and file offset @var{end} will be restored.
11993 These offsets are relative to the addresses in the file, before
11994 the @var{bias} argument is applied.
11998 @node Core File Generation
11999 @section How to Produce a Core File from Your Program
12000 @cindex dump core from inferior
12002 A @dfn{core file} or @dfn{core dump} is a file that records the memory
12003 image of a running process and its process status (register values
12004 etc.). Its primary use is post-mortem debugging of a program that
12005 crashed while it ran outside a debugger. A program that crashes
12006 automatically produces a core file, unless this feature is disabled by
12007 the user. @xref{Files}, for information on invoking @value{GDBN} in
12008 the post-mortem debugging mode.
12010 Occasionally, you may wish to produce a core file of the program you
12011 are debugging in order to preserve a snapshot of its state.
12012 @value{GDBN} has a special command for that.
12016 @kindex generate-core-file
12017 @item generate-core-file [@var{file}]
12018 @itemx gcore [@var{file}]
12019 Produce a core dump of the inferior process. The optional argument
12020 @var{file} specifies the file name where to put the core dump. If not
12021 specified, the file name defaults to @file{core.@var{pid}}, where
12022 @var{pid} is the inferior process ID.
12024 Note that this command is implemented only for some systems (as of
12025 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
12027 On @sc{gnu}/Linux, this command can take into account the value of the
12028 file @file{/proc/@var{pid}/coredump_filter} when generating the core
12029 dump (@pxref{set use-coredump-filter}), and by default honors the
12030 @code{VM_DONTDUMP} flag for mappings where it is present in the file
12031 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
12033 @kindex set use-coredump-filter
12034 @anchor{set use-coredump-filter}
12035 @item set use-coredump-filter on
12036 @itemx set use-coredump-filter off
12037 Enable or disable the use of the file
12038 @file{/proc/@var{pid}/coredump_filter} when generating core dump
12039 files. This file is used by the Linux kernel to decide what types of
12040 memory mappings will be dumped or ignored when generating a core dump
12041 file. @var{pid} is the process ID of a currently running process.
12043 To make use of this feature, you have to write in the
12044 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
12045 which is a bit mask representing the memory mapping types. If a bit
12046 is set in the bit mask, then the memory mappings of the corresponding
12047 types will be dumped; otherwise, they will be ignored. This
12048 configuration is inherited by child processes. For more information
12049 about the bits that can be set in the
12050 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
12051 manpage of @code{core(5)}.
12053 By default, this option is @code{on}. If this option is turned
12054 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
12055 and instead uses the same default value as the Linux kernel in order
12056 to decide which pages will be dumped in the core dump file. This
12057 value is currently @code{0x33}, which means that bits @code{0}
12058 (anonymous private mappings), @code{1} (anonymous shared mappings),
12059 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
12060 This will cause these memory mappings to be dumped automatically.
12062 @kindex set dump-excluded-mappings
12063 @anchor{set dump-excluded-mappings}
12064 @item set dump-excluded-mappings on
12065 @itemx set dump-excluded-mappings off
12066 If @code{on} is specified, @value{GDBN} will dump memory mappings
12067 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
12068 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
12070 The default value is @code{off}.
12073 @node Character Sets
12074 @section Character Sets
12075 @cindex character sets
12077 @cindex translating between character sets
12078 @cindex host character set
12079 @cindex target character set
12081 If the program you are debugging uses a different character set to
12082 represent characters and strings than the one @value{GDBN} uses itself,
12083 @value{GDBN} can automatically translate between the character sets for
12084 you. The character set @value{GDBN} uses we call the @dfn{host
12085 character set}; the one the inferior program uses we call the
12086 @dfn{target character set}.
12088 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
12089 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
12090 remote protocol (@pxref{Remote Debugging}) to debug a program
12091 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
12092 then the host character set is Latin-1, and the target character set is
12093 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
12094 target-charset EBCDIC-US}, then @value{GDBN} translates between
12095 @sc{ebcdic} and Latin 1 as you print character or string values, or use
12096 character and string literals in expressions.
12098 @value{GDBN} has no way to automatically recognize which character set
12099 the inferior program uses; you must tell it, using the @code{set
12100 target-charset} command, described below.
12102 Here are the commands for controlling @value{GDBN}'s character set
12106 @item set target-charset @var{charset}
12107 @kindex set target-charset
12108 Set the current target character set to @var{charset}. To display the
12109 list of supported target character sets, type
12110 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
12112 @item set host-charset @var{charset}
12113 @kindex set host-charset
12114 Set the current host character set to @var{charset}.
12116 By default, @value{GDBN} uses a host character set appropriate to the
12117 system it is running on; you can override that default using the
12118 @code{set host-charset} command. On some systems, @value{GDBN} cannot
12119 automatically determine the appropriate host character set. In this
12120 case, @value{GDBN} uses @samp{UTF-8}.
12122 @value{GDBN} can only use certain character sets as its host character
12123 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
12124 @value{GDBN} will list the host character sets it supports.
12126 @item set charset @var{charset}
12127 @kindex set charset
12128 Set the current host and target character sets to @var{charset}. As
12129 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
12130 @value{GDBN} will list the names of the character sets that can be used
12131 for both host and target.
12134 @kindex show charset
12135 Show the names of the current host and target character sets.
12137 @item show host-charset
12138 @kindex show host-charset
12139 Show the name of the current host character set.
12141 @item show target-charset
12142 @kindex show target-charset
12143 Show the name of the current target character set.
12145 @item set target-wide-charset @var{charset}
12146 @kindex set target-wide-charset
12147 Set the current target's wide character set to @var{charset}. This is
12148 the character set used by the target's @code{wchar_t} type. To
12149 display the list of supported wide character sets, type
12150 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
12152 @item show target-wide-charset
12153 @kindex show target-wide-charset
12154 Show the name of the current target's wide character set.
12157 Here is an example of @value{GDBN}'s character set support in action.
12158 Assume that the following source code has been placed in the file
12159 @file{charset-test.c}:
12165 = @{72, 101, 108, 108, 111, 44, 32, 119,
12166 111, 114, 108, 100, 33, 10, 0@};
12167 char ibm1047_hello[]
12168 = @{200, 133, 147, 147, 150, 107, 64, 166,
12169 150, 153, 147, 132, 90, 37, 0@};
12173 printf ("Hello, world!\n");
12177 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
12178 containing the string @samp{Hello, world!} followed by a newline,
12179 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
12181 We compile the program, and invoke the debugger on it:
12184 $ gcc -g charset-test.c -o charset-test
12185 $ gdb -nw charset-test
12186 GNU gdb 2001-12-19-cvs
12187 Copyright 2001 Free Software Foundation, Inc.
12192 We can use the @code{show charset} command to see what character sets
12193 @value{GDBN} is currently using to interpret and display characters and
12197 (@value{GDBP}) show charset
12198 The current host and target character set is `ISO-8859-1'.
12202 For the sake of printing this manual, let's use @sc{ascii} as our
12203 initial character set:
12205 (@value{GDBP}) set charset ASCII
12206 (@value{GDBP}) show charset
12207 The current host and target character set is `ASCII'.
12211 Let's assume that @sc{ascii} is indeed the correct character set for our
12212 host system --- in other words, let's assume that if @value{GDBN} prints
12213 characters using the @sc{ascii} character set, our terminal will display
12214 them properly. Since our current target character set is also
12215 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
12218 (@value{GDBP}) print ascii_hello
12219 $1 = 0x401698 "Hello, world!\n"
12220 (@value{GDBP}) print ascii_hello[0]
12225 @value{GDBN} uses the target character set for character and string
12226 literals you use in expressions:
12229 (@value{GDBP}) print '+'
12234 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
12237 @value{GDBN} relies on the user to tell it which character set the
12238 target program uses. If we print @code{ibm1047_hello} while our target
12239 character set is still @sc{ascii}, we get jibberish:
12242 (@value{GDBP}) print ibm1047_hello
12243 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
12244 (@value{GDBP}) print ibm1047_hello[0]
12249 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
12250 @value{GDBN} tells us the character sets it supports:
12253 (@value{GDBP}) set target-charset
12254 ASCII EBCDIC-US IBM1047 ISO-8859-1
12255 (@value{GDBP}) set target-charset
12258 We can select @sc{ibm1047} as our target character set, and examine the
12259 program's strings again. Now the @sc{ascii} string is wrong, but
12260 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
12261 target character set, @sc{ibm1047}, to the host character set,
12262 @sc{ascii}, and they display correctly:
12265 (@value{GDBP}) set target-charset IBM1047
12266 (@value{GDBP}) show charset
12267 The current host character set is `ASCII'.
12268 The current target character set is `IBM1047'.
12269 (@value{GDBP}) print ascii_hello
12270 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
12271 (@value{GDBP}) print ascii_hello[0]
12273 (@value{GDBP}) print ibm1047_hello
12274 $8 = 0x4016a8 "Hello, world!\n"
12275 (@value{GDBP}) print ibm1047_hello[0]
12280 As above, @value{GDBN} uses the target character set for character and
12281 string literals you use in expressions:
12284 (@value{GDBP}) print '+'
12289 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
12292 @node Caching Target Data
12293 @section Caching Data of Targets
12294 @cindex caching data of targets
12296 @value{GDBN} caches data exchanged between the debugger and a target.
12297 Each cache is associated with the address space of the inferior.
12298 @xref{Inferiors and Programs}, about inferior and address space.
12299 Such caching generally improves performance in remote debugging
12300 (@pxref{Remote Debugging}), because it reduces the overhead of the
12301 remote protocol by bundling memory reads and writes into large chunks.
12302 Unfortunately, simply caching everything would lead to incorrect results,
12303 since @value{GDBN} does not necessarily know anything about volatile
12304 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
12305 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
12307 Therefore, by default, @value{GDBN} only caches data
12308 known to be on the stack@footnote{In non-stop mode, it is moderately
12309 rare for a running thread to modify the stack of a stopped thread
12310 in a way that would interfere with a backtrace, and caching of
12311 stack reads provides a significant speed up of remote backtraces.} or
12312 in the code segment.
12313 Other regions of memory can be explicitly marked as
12314 cacheable; @pxref{Memory Region Attributes}.
12317 @kindex set remotecache
12318 @item set remotecache on
12319 @itemx set remotecache off
12320 This option no longer does anything; it exists for compatibility
12323 @kindex show remotecache
12324 @item show remotecache
12325 Show the current state of the obsolete remotecache flag.
12327 @kindex set stack-cache
12328 @item set stack-cache on
12329 @itemx set stack-cache off
12330 Enable or disable caching of stack accesses. When @code{on}, use
12331 caching. By default, this option is @code{on}.
12333 @kindex show stack-cache
12334 @item show stack-cache
12335 Show the current state of data caching for memory accesses.
12337 @kindex set code-cache
12338 @item set code-cache on
12339 @itemx set code-cache off
12340 Enable or disable caching of code segment accesses. When @code{on},
12341 use caching. By default, this option is @code{on}. This improves
12342 performance of disassembly in remote debugging.
12344 @kindex show code-cache
12345 @item show code-cache
12346 Show the current state of target memory cache for code segment
12349 @kindex info dcache
12350 @item info dcache @r{[}line@r{]}
12351 Print the information about the performance of data cache of the
12352 current inferior's address space. The information displayed
12353 includes the dcache width and depth, and for each cache line, its
12354 number, address, and how many times it was referenced. This
12355 command is useful for debugging the data cache operation.
12357 If a line number is specified, the contents of that line will be
12360 @item set dcache size @var{size}
12361 @cindex dcache size
12362 @kindex set dcache size
12363 Set maximum number of entries in dcache (dcache depth above).
12365 @item set dcache line-size @var{line-size}
12366 @cindex dcache line-size
12367 @kindex set dcache line-size
12368 Set number of bytes each dcache entry caches (dcache width above).
12369 Must be a power of 2.
12371 @item show dcache size
12372 @kindex show dcache size
12373 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
12375 @item show dcache line-size
12376 @kindex show dcache line-size
12377 Show default size of dcache lines.
12381 @node Searching Memory
12382 @section Search Memory
12383 @cindex searching memory
12385 Memory can be searched for a particular sequence of bytes with the
12386 @code{find} command.
12390 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12391 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12392 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
12393 etc. The search begins at address @var{start_addr} and continues for either
12394 @var{len} bytes or through to @var{end_addr} inclusive.
12397 @var{s} and @var{n} are optional parameters.
12398 They may be specified in either order, apart or together.
12401 @item @var{s}, search query size
12402 The size of each search query value.
12408 halfwords (two bytes)
12412 giant words (eight bytes)
12415 All values are interpreted in the current language.
12416 This means, for example, that if the current source language is C/C@t{++}
12417 then searching for the string ``hello'' includes the trailing '\0'.
12418 The null terminator can be removed from searching by using casts,
12419 e.g.: @samp{@{char[5]@}"hello"}.
12421 If the value size is not specified, it is taken from the
12422 value's type in the current language.
12423 This is useful when one wants to specify the search
12424 pattern as a mixture of types.
12425 Note that this means, for example, that in the case of C-like languages
12426 a search for an untyped 0x42 will search for @samp{(int) 0x42}
12427 which is typically four bytes.
12429 @item @var{n}, maximum number of finds
12430 The maximum number of matches to print. The default is to print all finds.
12433 You can use strings as search values. Quote them with double-quotes
12435 The string value is copied into the search pattern byte by byte,
12436 regardless of the endianness of the target and the size specification.
12438 The address of each match found is printed as well as a count of the
12439 number of matches found.
12441 The address of the last value found is stored in convenience variable
12443 A count of the number of matches is stored in @samp{$numfound}.
12445 For example, if stopped at the @code{printf} in this function:
12451 static char hello[] = "hello-hello";
12452 static struct @{ char c; short s; int i; @}
12453 __attribute__ ((packed)) mixed
12454 = @{ 'c', 0x1234, 0x87654321 @};
12455 printf ("%s\n", hello);
12460 you get during debugging:
12463 (gdb) find &hello[0], +sizeof(hello), "hello"
12464 0x804956d <hello.1620+6>
12466 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12467 0x8049567 <hello.1620>
12468 0x804956d <hello.1620+6>
12470 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12471 0x8049567 <hello.1620>
12472 0x804956d <hello.1620+6>
12474 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12475 0x8049567 <hello.1620>
12477 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12478 0x8049560 <mixed.1625>
12480 (gdb) print $numfound
12483 $2 = (void *) 0x8049560
12487 @section Value Sizes
12489 Whenever @value{GDBN} prints a value memory will be allocated within
12490 @value{GDBN} to hold the contents of the value. It is possible in
12491 some languages with dynamic typing systems, that an invalid program
12492 may indicate a value that is incorrectly large, this in turn may cause
12493 @value{GDBN} to try and allocate an overly large ammount of memory.
12496 @kindex set max-value-size
12497 @item set max-value-size @var{bytes}
12498 @itemx set max-value-size unlimited
12499 Set the maximum size of memory that @value{GDBN} will allocate for the
12500 contents of a value to @var{bytes}, trying to display a value that
12501 requires more memory than that will result in an error.
12503 Setting this variable does not effect values that have already been
12504 allocated within @value{GDBN}, only future allocations.
12506 There's a minimum size that @code{max-value-size} can be set to in
12507 order that @value{GDBN} can still operate correctly, this minimum is
12508 currently 16 bytes.
12510 The limit applies to the results of some subexpressions as well as to
12511 complete expressions. For example, an expression denoting a simple
12512 integer component, such as @code{x.y.z}, may fail if the size of
12513 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12514 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12515 @var{A} is an array variable with non-constant size, will generally
12516 succeed regardless of the bounds on @var{A}, as long as the component
12517 size is less than @var{bytes}.
12519 The default value of @code{max-value-size} is currently 64k.
12521 @kindex show max-value-size
12522 @item show max-value-size
12523 Show the maximum size of memory, in bytes, that @value{GDBN} will
12524 allocate for the contents of a value.
12527 @node Optimized Code
12528 @chapter Debugging Optimized Code
12529 @cindex optimized code, debugging
12530 @cindex debugging optimized code
12532 Almost all compilers support optimization. With optimization
12533 disabled, the compiler generates assembly code that corresponds
12534 directly to your source code, in a simplistic way. As the compiler
12535 applies more powerful optimizations, the generated assembly code
12536 diverges from your original source code. With help from debugging
12537 information generated by the compiler, @value{GDBN} can map from
12538 the running program back to constructs from your original source.
12540 @value{GDBN} is more accurate with optimization disabled. If you
12541 can recompile without optimization, it is easier to follow the
12542 progress of your program during debugging. But, there are many cases
12543 where you may need to debug an optimized version.
12545 When you debug a program compiled with @samp{-g -O}, remember that the
12546 optimizer has rearranged your code; the debugger shows you what is
12547 really there. Do not be too surprised when the execution path does not
12548 exactly match your source file! An extreme example: if you define a
12549 variable, but never use it, @value{GDBN} never sees that
12550 variable---because the compiler optimizes it out of existence.
12552 Some things do not work as well with @samp{-g -O} as with just
12553 @samp{-g}, particularly on machines with instruction scheduling. If in
12554 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12555 please report it to us as a bug (including a test case!).
12556 @xref{Variables}, for more information about debugging optimized code.
12559 * Inline Functions:: How @value{GDBN} presents inlining
12560 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12563 @node Inline Functions
12564 @section Inline Functions
12565 @cindex inline functions, debugging
12567 @dfn{Inlining} is an optimization that inserts a copy of the function
12568 body directly at each call site, instead of jumping to a shared
12569 routine. @value{GDBN} displays inlined functions just like
12570 non-inlined functions. They appear in backtraces. You can view their
12571 arguments and local variables, step into them with @code{step}, skip
12572 them with @code{next}, and escape from them with @code{finish}.
12573 You can check whether a function was inlined by using the
12574 @code{info frame} command.
12576 For @value{GDBN} to support inlined functions, the compiler must
12577 record information about inlining in the debug information ---
12578 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12579 other compilers do also. @value{GDBN} only supports inlined functions
12580 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12581 do not emit two required attributes (@samp{DW_AT_call_file} and
12582 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12583 function calls with earlier versions of @value{NGCC}. It instead
12584 displays the arguments and local variables of inlined functions as
12585 local variables in the caller.
12587 The body of an inlined function is directly included at its call site;
12588 unlike a non-inlined function, there are no instructions devoted to
12589 the call. @value{GDBN} still pretends that the call site and the
12590 start of the inlined function are different instructions. Stepping to
12591 the call site shows the call site, and then stepping again shows
12592 the first line of the inlined function, even though no additional
12593 instructions are executed.
12595 This makes source-level debugging much clearer; you can see both the
12596 context of the call and then the effect of the call. Only stepping by
12597 a single instruction using @code{stepi} or @code{nexti} does not do
12598 this; single instruction steps always show the inlined body.
12600 There are some ways that @value{GDBN} does not pretend that inlined
12601 function calls are the same as normal calls:
12605 Setting breakpoints at the call site of an inlined function may not
12606 work, because the call site does not contain any code. @value{GDBN}
12607 may incorrectly move the breakpoint to the next line of the enclosing
12608 function, after the call. This limitation will be removed in a future
12609 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12610 or inside the inlined function instead.
12613 @value{GDBN} cannot locate the return value of inlined calls after
12614 using the @code{finish} command. This is a limitation of compiler-generated
12615 debugging information; after @code{finish}, you can step to the next line
12616 and print a variable where your program stored the return value.
12620 @node Tail Call Frames
12621 @section Tail Call Frames
12622 @cindex tail call frames, debugging
12624 Function @code{B} can call function @code{C} in its very last statement. In
12625 unoptimized compilation the call of @code{C} is immediately followed by return
12626 instruction at the end of @code{B} code. Optimizing compiler may replace the
12627 call and return in function @code{B} into one jump to function @code{C}
12628 instead. Such use of a jump instruction is called @dfn{tail call}.
12630 During execution of function @code{C}, there will be no indication in the
12631 function call stack frames that it was tail-called from @code{B}. If function
12632 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12633 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12634 some cases @value{GDBN} can determine that @code{C} was tail-called from
12635 @code{B}, and it will then create fictitious call frame for that, with the
12636 return address set up as if @code{B} called @code{C} normally.
12638 This functionality is currently supported only by DWARF 2 debugging format and
12639 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12640 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12643 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12644 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12648 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12650 Stack level 1, frame at 0x7fffffffda30:
12651 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12652 tail call frame, caller of frame at 0x7fffffffda30
12653 source language c++.
12654 Arglist at unknown address.
12655 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12658 The detection of all the possible code path executions can find them ambiguous.
12659 There is no execution history stored (possible @ref{Reverse Execution} is never
12660 used for this purpose) and the last known caller could have reached the known
12661 callee by multiple different jump sequences. In such case @value{GDBN} still
12662 tries to show at least all the unambiguous top tail callers and all the
12663 unambiguous bottom tail calees, if any.
12666 @anchor{set debug entry-values}
12667 @item set debug entry-values
12668 @kindex set debug entry-values
12669 When set to on, enables printing of analysis messages for both frame argument
12670 values at function entry and tail calls. It will show all the possible valid
12671 tail calls code paths it has considered. It will also print the intersection
12672 of them with the final unambiguous (possibly partial or even empty) code path
12675 @item show debug entry-values
12676 @kindex show debug entry-values
12677 Show the current state of analysis messages printing for both frame argument
12678 values at function entry and tail calls.
12681 The analysis messages for tail calls can for example show why the virtual tail
12682 call frame for function @code{c} has not been recognized (due to the indirect
12683 reference by variable @code{x}):
12686 static void __attribute__((noinline, noclone)) c (void);
12687 void (*x) (void) = c;
12688 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12689 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12690 int main (void) @{ x (); return 0; @}
12692 Breakpoint 1, DW_OP_entry_value resolving cannot find
12693 DW_TAG_call_site 0x40039a in main
12695 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12698 #1 0x000000000040039a in main () at t.c:5
12701 Another possibility is an ambiguous virtual tail call frames resolution:
12705 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12706 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12707 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12708 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12709 static void __attribute__((noinline, noclone)) b (void)
12710 @{ if (i) c (); else e (); @}
12711 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12712 int main (void) @{ a (); return 0; @}
12714 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12715 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12716 tailcall: reduced: 0x4004d2(a) |
12719 #1 0x00000000004004d2 in a () at t.c:8
12720 #2 0x0000000000400395 in main () at t.c:9
12723 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12724 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12726 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12727 @ifset HAVE_MAKEINFO_CLICK
12728 @set ARROW @click{}
12729 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12730 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12732 @ifclear HAVE_MAKEINFO_CLICK
12734 @set CALLSEQ1B @value{CALLSEQ1A}
12735 @set CALLSEQ2B @value{CALLSEQ2A}
12738 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12739 The code can have possible execution paths @value{CALLSEQ1B} or
12740 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12742 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12743 has found. It then finds another possible calling sequcen - that one is
12744 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12745 printed as the @code{reduced:} calling sequence. That one could have many
12746 futher @code{compare:} and @code{reduced:} statements as long as there remain
12747 any non-ambiguous sequence entries.
12749 For the frame of function @code{b} in both cases there are different possible
12750 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12751 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12752 therefore this one is displayed to the user while the ambiguous frames are
12755 There can be also reasons why printing of frame argument values at function
12760 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12761 static void __attribute__((noinline, noclone)) a (int i);
12762 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12763 static void __attribute__((noinline, noclone)) a (int i)
12764 @{ if (i) b (i - 1); else c (0); @}
12765 int main (void) @{ a (5); return 0; @}
12768 #0 c (i=i@@entry=0) at t.c:2
12769 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12770 function "a" at 0x400420 can call itself via tail calls
12771 i=<optimized out>) at t.c:6
12772 #2 0x000000000040036e in main () at t.c:7
12775 @value{GDBN} cannot find out from the inferior state if and how many times did
12776 function @code{a} call itself (via function @code{b}) as these calls would be
12777 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12778 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12779 prints @code{<optimized out>} instead.
12782 @chapter C Preprocessor Macros
12784 Some languages, such as C and C@t{++}, provide a way to define and invoke
12785 ``preprocessor macros'' which expand into strings of tokens.
12786 @value{GDBN} can evaluate expressions containing macro invocations, show
12787 the result of macro expansion, and show a macro's definition, including
12788 where it was defined.
12790 You may need to compile your program specially to provide @value{GDBN}
12791 with information about preprocessor macros. Most compilers do not
12792 include macros in their debugging information, even when you compile
12793 with the @option{-g} flag. @xref{Compilation}.
12795 A program may define a macro at one point, remove that definition later,
12796 and then provide a different definition after that. Thus, at different
12797 points in the program, a macro may have different definitions, or have
12798 no definition at all. If there is a current stack frame, @value{GDBN}
12799 uses the macros in scope at that frame's source code line. Otherwise,
12800 @value{GDBN} uses the macros in scope at the current listing location;
12803 Whenever @value{GDBN} evaluates an expression, it always expands any
12804 macro invocations present in the expression. @value{GDBN} also provides
12805 the following commands for working with macros explicitly.
12809 @kindex macro expand
12810 @cindex macro expansion, showing the results of preprocessor
12811 @cindex preprocessor macro expansion, showing the results of
12812 @cindex expanding preprocessor macros
12813 @item macro expand @var{expression}
12814 @itemx macro exp @var{expression}
12815 Show the results of expanding all preprocessor macro invocations in
12816 @var{expression}. Since @value{GDBN} simply expands macros, but does
12817 not parse the result, @var{expression} need not be a valid expression;
12818 it can be any string of tokens.
12821 @item macro expand-once @var{expression}
12822 @itemx macro exp1 @var{expression}
12823 @cindex expand macro once
12824 @i{(This command is not yet implemented.)} Show the results of
12825 expanding those preprocessor macro invocations that appear explicitly in
12826 @var{expression}. Macro invocations appearing in that expansion are
12827 left unchanged. This command allows you to see the effect of a
12828 particular macro more clearly, without being confused by further
12829 expansions. Since @value{GDBN} simply expands macros, but does not
12830 parse the result, @var{expression} need not be a valid expression; it
12831 can be any string of tokens.
12834 @cindex macro definition, showing
12835 @cindex definition of a macro, showing
12836 @cindex macros, from debug info
12837 @item info macro [-a|-all] [--] @var{macro}
12838 Show the current definition or all definitions of the named @var{macro},
12839 and describe the source location or compiler command-line where that
12840 definition was established. The optional double dash is to signify the end of
12841 argument processing and the beginning of @var{macro} for non C-like macros where
12842 the macro may begin with a hyphen.
12844 @kindex info macros
12845 @item info macros @var{location}
12846 Show all macro definitions that are in effect at the location specified
12847 by @var{location}, and describe the source location or compiler
12848 command-line where those definitions were established.
12850 @kindex macro define
12851 @cindex user-defined macros
12852 @cindex defining macros interactively
12853 @cindex macros, user-defined
12854 @item macro define @var{macro} @var{replacement-list}
12855 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12856 Introduce a definition for a preprocessor macro named @var{macro},
12857 invocations of which are replaced by the tokens given in
12858 @var{replacement-list}. The first form of this command defines an
12859 ``object-like'' macro, which takes no arguments; the second form
12860 defines a ``function-like'' macro, which takes the arguments given in
12863 A definition introduced by this command is in scope in every
12864 expression evaluated in @value{GDBN}, until it is removed with the
12865 @code{macro undef} command, described below. The definition overrides
12866 all definitions for @var{macro} present in the program being debugged,
12867 as well as any previous user-supplied definition.
12869 @kindex macro undef
12870 @item macro undef @var{macro}
12871 Remove any user-supplied definition for the macro named @var{macro}.
12872 This command only affects definitions provided with the @code{macro
12873 define} command, described above; it cannot remove definitions present
12874 in the program being debugged.
12878 List all the macros defined using the @code{macro define} command.
12881 @cindex macros, example of debugging with
12882 Here is a transcript showing the above commands in action. First, we
12883 show our source files:
12888 #include "sample.h"
12891 #define ADD(x) (M + x)
12896 printf ("Hello, world!\n");
12898 printf ("We're so creative.\n");
12900 printf ("Goodbye, world!\n");
12907 Now, we compile the program using the @sc{gnu} C compiler,
12908 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12909 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12910 and @option{-gdwarf-4}; we recommend always choosing the most recent
12911 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12912 includes information about preprocessor macros in the debugging
12916 $ gcc -gdwarf-2 -g3 sample.c -o sample
12920 Now, we start @value{GDBN} on our sample program:
12924 GNU gdb 2002-05-06-cvs
12925 Copyright 2002 Free Software Foundation, Inc.
12926 GDB is free software, @dots{}
12930 We can expand macros and examine their definitions, even when the
12931 program is not running. @value{GDBN} uses the current listing position
12932 to decide which macro definitions are in scope:
12935 (@value{GDBP}) list main
12938 5 #define ADD(x) (M + x)
12943 10 printf ("Hello, world!\n");
12945 12 printf ("We're so creative.\n");
12946 (@value{GDBP}) info macro ADD
12947 Defined at /home/jimb/gdb/macros/play/sample.c:5
12948 #define ADD(x) (M + x)
12949 (@value{GDBP}) info macro Q
12950 Defined at /home/jimb/gdb/macros/play/sample.h:1
12951 included at /home/jimb/gdb/macros/play/sample.c:2
12953 (@value{GDBP}) macro expand ADD(1)
12954 expands to: (42 + 1)
12955 (@value{GDBP}) macro expand-once ADD(1)
12956 expands to: once (M + 1)
12960 In the example above, note that @code{macro expand-once} expands only
12961 the macro invocation explicit in the original text --- the invocation of
12962 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12963 which was introduced by @code{ADD}.
12965 Once the program is running, @value{GDBN} uses the macro definitions in
12966 force at the source line of the current stack frame:
12969 (@value{GDBP}) break main
12970 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12972 Starting program: /home/jimb/gdb/macros/play/sample
12974 Breakpoint 1, main () at sample.c:10
12975 10 printf ("Hello, world!\n");
12979 At line 10, the definition of the macro @code{N} at line 9 is in force:
12982 (@value{GDBP}) info macro N
12983 Defined at /home/jimb/gdb/macros/play/sample.c:9
12985 (@value{GDBP}) macro expand N Q M
12986 expands to: 28 < 42
12987 (@value{GDBP}) print N Q M
12992 As we step over directives that remove @code{N}'s definition, and then
12993 give it a new definition, @value{GDBN} finds the definition (or lack
12994 thereof) in force at each point:
12997 (@value{GDBP}) next
12999 12 printf ("We're so creative.\n");
13000 (@value{GDBP}) info macro N
13001 The symbol `N' has no definition as a C/C++ preprocessor macro
13002 at /home/jimb/gdb/macros/play/sample.c:12
13003 (@value{GDBP}) next
13005 14 printf ("Goodbye, world!\n");
13006 (@value{GDBP}) info macro N
13007 Defined at /home/jimb/gdb/macros/play/sample.c:13
13009 (@value{GDBP}) macro expand N Q M
13010 expands to: 1729 < 42
13011 (@value{GDBP}) print N Q M
13016 In addition to source files, macros can be defined on the compilation command
13017 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
13018 such a way, @value{GDBN} displays the location of their definition as line zero
13019 of the source file submitted to the compiler.
13022 (@value{GDBP}) info macro __STDC__
13023 Defined at /home/jimb/gdb/macros/play/sample.c:0
13030 @chapter Tracepoints
13031 @c This chapter is based on the documentation written by Michael
13032 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
13034 @cindex tracepoints
13035 In some applications, it is not feasible for the debugger to interrupt
13036 the program's execution long enough for the developer to learn
13037 anything helpful about its behavior. If the program's correctness
13038 depends on its real-time behavior, delays introduced by a debugger
13039 might cause the program to change its behavior drastically, or perhaps
13040 fail, even when the code itself is correct. It is useful to be able
13041 to observe the program's behavior without interrupting it.
13043 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
13044 specify locations in the program, called @dfn{tracepoints}, and
13045 arbitrary expressions to evaluate when those tracepoints are reached.
13046 Later, using the @code{tfind} command, you can examine the values
13047 those expressions had when the program hit the tracepoints. The
13048 expressions may also denote objects in memory---structures or arrays,
13049 for example---whose values @value{GDBN} should record; while visiting
13050 a particular tracepoint, you may inspect those objects as if they were
13051 in memory at that moment. However, because @value{GDBN} records these
13052 values without interacting with you, it can do so quickly and
13053 unobtrusively, hopefully not disturbing the program's behavior.
13055 The tracepoint facility is currently available only for remote
13056 targets. @xref{Targets}. In addition, your remote target must know
13057 how to collect trace data. This functionality is implemented in the
13058 remote stub; however, none of the stubs distributed with @value{GDBN}
13059 support tracepoints as of this writing. The format of the remote
13060 packets used to implement tracepoints are described in @ref{Tracepoint
13063 It is also possible to get trace data from a file, in a manner reminiscent
13064 of corefiles; you specify the filename, and use @code{tfind} to search
13065 through the file. @xref{Trace Files}, for more details.
13067 This chapter describes the tracepoint commands and features.
13070 * Set Tracepoints::
13071 * Analyze Collected Data::
13072 * Tracepoint Variables::
13076 @node Set Tracepoints
13077 @section Commands to Set Tracepoints
13079 Before running such a @dfn{trace experiment}, an arbitrary number of
13080 tracepoints can be set. A tracepoint is actually a special type of
13081 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
13082 standard breakpoint commands. For instance, as with breakpoints,
13083 tracepoint numbers are successive integers starting from one, and many
13084 of the commands associated with tracepoints take the tracepoint number
13085 as their argument, to identify which tracepoint to work on.
13087 For each tracepoint, you can specify, in advance, some arbitrary set
13088 of data that you want the target to collect in the trace buffer when
13089 it hits that tracepoint. The collected data can include registers,
13090 local variables, or global data. Later, you can use @value{GDBN}
13091 commands to examine the values these data had at the time the
13092 tracepoint was hit.
13094 Tracepoints do not support every breakpoint feature. Ignore counts on
13095 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
13096 commands when they are hit. Tracepoints may not be thread-specific
13099 @cindex fast tracepoints
13100 Some targets may support @dfn{fast tracepoints}, which are inserted in
13101 a different way (such as with a jump instead of a trap), that is
13102 faster but possibly restricted in where they may be installed.
13104 @cindex static tracepoints
13105 @cindex markers, static tracepoints
13106 @cindex probing markers, static tracepoints
13107 Regular and fast tracepoints are dynamic tracing facilities, meaning
13108 that they can be used to insert tracepoints at (almost) any location
13109 in the target. Some targets may also support controlling @dfn{static
13110 tracepoints} from @value{GDBN}. With static tracing, a set of
13111 instrumentation points, also known as @dfn{markers}, are embedded in
13112 the target program, and can be activated or deactivated by name or
13113 address. These are usually placed at locations which facilitate
13114 investigating what the target is actually doing. @value{GDBN}'s
13115 support for static tracing includes being able to list instrumentation
13116 points, and attach them with @value{GDBN} defined high level
13117 tracepoints that expose the whole range of convenience of
13118 @value{GDBN}'s tracepoints support. Namely, support for collecting
13119 registers values and values of global or local (to the instrumentation
13120 point) variables; tracepoint conditions and trace state variables.
13121 The act of installing a @value{GDBN} static tracepoint on an
13122 instrumentation point, or marker, is referred to as @dfn{probing} a
13123 static tracepoint marker.
13125 @code{gdbserver} supports tracepoints on some target systems.
13126 @xref{Server,,Tracepoints support in @code{gdbserver}}.
13128 This section describes commands to set tracepoints and associated
13129 conditions and actions.
13132 * Create and Delete Tracepoints::
13133 * Enable and Disable Tracepoints::
13134 * Tracepoint Passcounts::
13135 * Tracepoint Conditions::
13136 * Trace State Variables::
13137 * Tracepoint Actions::
13138 * Listing Tracepoints::
13139 * Listing Static Tracepoint Markers::
13140 * Starting and Stopping Trace Experiments::
13141 * Tracepoint Restrictions::
13144 @node Create and Delete Tracepoints
13145 @subsection Create and Delete Tracepoints
13148 @cindex set tracepoint
13150 @item trace @var{location}
13151 The @code{trace} command is very similar to the @code{break} command.
13152 Its argument @var{location} can be any valid location.
13153 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
13154 which is a point in the target program where the debugger will briefly stop,
13155 collect some data, and then allow the program to continue. Setting a tracepoint
13156 or changing its actions takes effect immediately if the remote stub
13157 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
13159 If remote stub doesn't support the @samp{InstallInTrace} feature, all
13160 these changes don't take effect until the next @code{tstart}
13161 command, and once a trace experiment is running, further changes will
13162 not have any effect until the next trace experiment starts. In addition,
13163 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
13164 address is not yet resolved. (This is similar to pending breakpoints.)
13165 Pending tracepoints are not downloaded to the target and not installed
13166 until they are resolved. The resolution of pending tracepoints requires
13167 @value{GDBN} support---when debugging with the remote target, and
13168 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
13169 tracing}), pending tracepoints can not be resolved (and downloaded to
13170 the remote stub) while @value{GDBN} is disconnected.
13172 Here are some examples of using the @code{trace} command:
13175 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
13177 (@value{GDBP}) @b{trace +2} // 2 lines forward
13179 (@value{GDBP}) @b{trace my_function} // first source line of function
13181 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
13183 (@value{GDBP}) @b{trace *0x2117c4} // an address
13187 You can abbreviate @code{trace} as @code{tr}.
13189 @item trace @var{location} if @var{cond}
13190 Set a tracepoint with condition @var{cond}; evaluate the expression
13191 @var{cond} each time the tracepoint is reached, and collect data only
13192 if the value is nonzero---that is, if @var{cond} evaluates as true.
13193 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
13194 information on tracepoint conditions.
13196 @item ftrace @var{location} [ if @var{cond} ]
13197 @cindex set fast tracepoint
13198 @cindex fast tracepoints, setting
13200 The @code{ftrace} command sets a fast tracepoint. For targets that
13201 support them, fast tracepoints will use a more efficient but possibly
13202 less general technique to trigger data collection, such as a jump
13203 instruction instead of a trap, or some sort of hardware support. It
13204 may not be possible to create a fast tracepoint at the desired
13205 location, in which case the command will exit with an explanatory
13208 @value{GDBN} handles arguments to @code{ftrace} exactly as for
13211 On 32-bit x86-architecture systems, fast tracepoints normally need to
13212 be placed at an instruction that is 5 bytes or longer, but can be
13213 placed at 4-byte instructions if the low 64K of memory of the target
13214 program is available to install trampolines. Some Unix-type systems,
13215 such as @sc{gnu}/Linux, exclude low addresses from the program's
13216 address space; but for instance with the Linux kernel it is possible
13217 to let @value{GDBN} use this area by doing a @command{sysctl} command
13218 to set the @code{mmap_min_addr} kernel parameter, as in
13221 sudo sysctl -w vm.mmap_min_addr=32768
13225 which sets the low address to 32K, which leaves plenty of room for
13226 trampolines. The minimum address should be set to a page boundary.
13228 @item strace @var{location} [ if @var{cond} ]
13229 @cindex set static tracepoint
13230 @cindex static tracepoints, setting
13231 @cindex probe static tracepoint marker
13233 The @code{strace} command sets a static tracepoint. For targets that
13234 support it, setting a static tracepoint probes a static
13235 instrumentation point, or marker, found at @var{location}. It may not
13236 be possible to set a static tracepoint at the desired location, in
13237 which case the command will exit with an explanatory message.
13239 @value{GDBN} handles arguments to @code{strace} exactly as for
13240 @code{trace}, with the addition that the user can also specify
13241 @code{-m @var{marker}} as @var{location}. This probes the marker
13242 identified by the @var{marker} string identifier. This identifier
13243 depends on the static tracepoint backend library your program is
13244 using. You can find all the marker identifiers in the @samp{ID} field
13245 of the @code{info static-tracepoint-markers} command output.
13246 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
13247 Markers}. For example, in the following small program using the UST
13253 trace_mark(ust, bar33, "str %s", "FOOBAZ");
13258 the marker id is composed of joining the first two arguments to the
13259 @code{trace_mark} call with a slash, which translates to:
13262 (@value{GDBP}) info static-tracepoint-markers
13263 Cnt Enb ID Address What
13264 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
13270 so you may probe the marker above with:
13273 (@value{GDBP}) strace -m ust/bar33
13276 Static tracepoints accept an extra collect action --- @code{collect
13277 $_sdata}. This collects arbitrary user data passed in the probe point
13278 call to the tracing library. In the UST example above, you'll see
13279 that the third argument to @code{trace_mark} is a printf-like format
13280 string. The user data is then the result of running that formating
13281 string against the following arguments. Note that @code{info
13282 static-tracepoint-markers} command output lists that format string in
13283 the @samp{Data:} field.
13285 You can inspect this data when analyzing the trace buffer, by printing
13286 the $_sdata variable like any other variable available to
13287 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
13290 @cindex last tracepoint number
13291 @cindex recent tracepoint number
13292 @cindex tracepoint number
13293 The convenience variable @code{$tpnum} records the tracepoint number
13294 of the most recently set tracepoint.
13296 @kindex delete tracepoint
13297 @cindex tracepoint deletion
13298 @item delete tracepoint @r{[}@var{num}@r{]}
13299 Permanently delete one or more tracepoints. With no argument, the
13300 default is to delete all tracepoints. Note that the regular
13301 @code{delete} command can remove tracepoints also.
13306 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
13308 (@value{GDBP}) @b{delete trace} // remove all tracepoints
13312 You can abbreviate this command as @code{del tr}.
13315 @node Enable and Disable Tracepoints
13316 @subsection Enable and Disable Tracepoints
13318 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
13321 @kindex disable tracepoint
13322 @item disable tracepoint @r{[}@var{num}@r{]}
13323 Disable tracepoint @var{num}, or all tracepoints if no argument
13324 @var{num} is given. A disabled tracepoint will have no effect during
13325 a trace experiment, but it is not forgotten. You can re-enable
13326 a disabled tracepoint using the @code{enable tracepoint} command.
13327 If the command is issued during a trace experiment and the debug target
13328 has support for disabling tracepoints during a trace experiment, then the
13329 change will be effective immediately. Otherwise, it will be applied to the
13330 next trace experiment.
13332 @kindex enable tracepoint
13333 @item enable tracepoint @r{[}@var{num}@r{]}
13334 Enable tracepoint @var{num}, or all tracepoints. If this command is
13335 issued during a trace experiment and the debug target supports enabling
13336 tracepoints during a trace experiment, then the enabled tracepoints will
13337 become effective immediately. Otherwise, they will become effective the
13338 next time a trace experiment is run.
13341 @node Tracepoint Passcounts
13342 @subsection Tracepoint Passcounts
13346 @cindex tracepoint pass count
13347 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
13348 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
13349 automatically stop a trace experiment. If a tracepoint's passcount is
13350 @var{n}, then the trace experiment will be automatically stopped on
13351 the @var{n}'th time that tracepoint is hit. If the tracepoint number
13352 @var{num} is not specified, the @code{passcount} command sets the
13353 passcount of the most recently defined tracepoint. If no passcount is
13354 given, the trace experiment will run until stopped explicitly by the
13360 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
13361 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
13363 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
13364 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
13365 (@value{GDBP}) @b{trace foo}
13366 (@value{GDBP}) @b{pass 3}
13367 (@value{GDBP}) @b{trace bar}
13368 (@value{GDBP}) @b{pass 2}
13369 (@value{GDBP}) @b{trace baz}
13370 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
13371 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
13372 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
13373 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
13377 @node Tracepoint Conditions
13378 @subsection Tracepoint Conditions
13379 @cindex conditional tracepoints
13380 @cindex tracepoint conditions
13382 The simplest sort of tracepoint collects data every time your program
13383 reaches a specified place. You can also specify a @dfn{condition} for
13384 a tracepoint. A condition is just a Boolean expression in your
13385 programming language (@pxref{Expressions, ,Expressions}). A
13386 tracepoint with a condition evaluates the expression each time your
13387 program reaches it, and data collection happens only if the condition
13390 Tracepoint conditions can be specified when a tracepoint is set, by
13391 using @samp{if} in the arguments to the @code{trace} command.
13392 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
13393 also be set or changed at any time with the @code{condition} command,
13394 just as with breakpoints.
13396 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
13397 the conditional expression itself. Instead, @value{GDBN} encodes the
13398 expression into an agent expression (@pxref{Agent Expressions})
13399 suitable for execution on the target, independently of @value{GDBN}.
13400 Global variables become raw memory locations, locals become stack
13401 accesses, and so forth.
13403 For instance, suppose you have a function that is usually called
13404 frequently, but should not be called after an error has occurred. You
13405 could use the following tracepoint command to collect data about calls
13406 of that function that happen while the error code is propagating
13407 through the program; an unconditional tracepoint could end up
13408 collecting thousands of useless trace frames that you would have to
13412 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
13415 @node Trace State Variables
13416 @subsection Trace State Variables
13417 @cindex trace state variables
13419 A @dfn{trace state variable} is a special type of variable that is
13420 created and managed by target-side code. The syntax is the same as
13421 that for GDB's convenience variables (a string prefixed with ``$''),
13422 but they are stored on the target. They must be created explicitly,
13423 using a @code{tvariable} command. They are always 64-bit signed
13426 Trace state variables are remembered by @value{GDBN}, and downloaded
13427 to the target along with tracepoint information when the trace
13428 experiment starts. There are no intrinsic limits on the number of
13429 trace state variables, beyond memory limitations of the target.
13431 @cindex convenience variables, and trace state variables
13432 Although trace state variables are managed by the target, you can use
13433 them in print commands and expressions as if they were convenience
13434 variables; @value{GDBN} will get the current value from the target
13435 while the trace experiment is running. Trace state variables share
13436 the same namespace as other ``$'' variables, which means that you
13437 cannot have trace state variables with names like @code{$23} or
13438 @code{$pc}, nor can you have a trace state variable and a convenience
13439 variable with the same name.
13443 @item tvariable $@var{name} [ = @var{expression} ]
13445 The @code{tvariable} command creates a new trace state variable named
13446 @code{$@var{name}}, and optionally gives it an initial value of
13447 @var{expression}. The @var{expression} is evaluated when this command is
13448 entered; the result will be converted to an integer if possible,
13449 otherwise @value{GDBN} will report an error. A subsequent
13450 @code{tvariable} command specifying the same name does not create a
13451 variable, but instead assigns the supplied initial value to the
13452 existing variable of that name, overwriting any previous initial
13453 value. The default initial value is 0.
13455 @item info tvariables
13456 @kindex info tvariables
13457 List all the trace state variables along with their initial values.
13458 Their current values may also be displayed, if the trace experiment is
13461 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13462 @kindex delete tvariable
13463 Delete the given trace state variables, or all of them if no arguments
13468 @node Tracepoint Actions
13469 @subsection Tracepoint Action Lists
13473 @cindex tracepoint actions
13474 @item actions @r{[}@var{num}@r{]}
13475 This command will prompt for a list of actions to be taken when the
13476 tracepoint is hit. If the tracepoint number @var{num} is not
13477 specified, this command sets the actions for the one that was most
13478 recently defined (so that you can define a tracepoint and then say
13479 @code{actions} without bothering about its number). You specify the
13480 actions themselves on the following lines, one action at a time, and
13481 terminate the actions list with a line containing just @code{end}. So
13482 far, the only defined actions are @code{collect}, @code{teval}, and
13483 @code{while-stepping}.
13485 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13486 Commands, ,Breakpoint Command Lists}), except that only the defined
13487 actions are allowed; any other @value{GDBN} command is rejected.
13489 @cindex remove actions from a tracepoint
13490 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13491 and follow it immediately with @samp{end}.
13494 (@value{GDBP}) @b{collect @var{data}} // collect some data
13496 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13498 (@value{GDBP}) @b{end} // signals the end of actions.
13501 In the following example, the action list begins with @code{collect}
13502 commands indicating the things to be collected when the tracepoint is
13503 hit. Then, in order to single-step and collect additional data
13504 following the tracepoint, a @code{while-stepping} command is used,
13505 followed by the list of things to be collected after each step in a
13506 sequence of single steps. The @code{while-stepping} command is
13507 terminated by its own separate @code{end} command. Lastly, the action
13508 list is terminated by an @code{end} command.
13511 (@value{GDBP}) @b{trace foo}
13512 (@value{GDBP}) @b{actions}
13513 Enter actions for tracepoint 1, one per line:
13516 > while-stepping 12
13517 > collect $pc, arr[i]
13522 @kindex collect @r{(tracepoints)}
13523 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13524 Collect values of the given expressions when the tracepoint is hit.
13525 This command accepts a comma-separated list of any valid expressions.
13526 In addition to global, static, or local variables, the following
13527 special arguments are supported:
13531 Collect all registers.
13534 Collect all function arguments.
13537 Collect all local variables.
13540 Collect the return address. This is helpful if you want to see more
13543 @emph{Note:} The return address location can not always be reliably
13544 determined up front, and the wrong address / registers may end up
13545 collected instead. On some architectures the reliability is higher
13546 for tracepoints at function entry, while on others it's the opposite.
13547 When this happens, backtracing will stop because the return address is
13548 found unavailable (unless another collect rule happened to match it).
13551 Collects the number of arguments from the static probe at which the
13552 tracepoint is located.
13553 @xref{Static Probe Points}.
13555 @item $_probe_arg@var{n}
13556 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13557 from the static probe at which the tracepoint is located.
13558 @xref{Static Probe Points}.
13561 @vindex $_sdata@r{, collect}
13562 Collect static tracepoint marker specific data. Only available for
13563 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13564 Lists}. On the UST static tracepoints library backend, an
13565 instrumentation point resembles a @code{printf} function call. The
13566 tracing library is able to collect user specified data formatted to a
13567 character string using the format provided by the programmer that
13568 instrumented the program. Other backends have similar mechanisms.
13569 Here's an example of a UST marker call:
13572 const char master_name[] = "$your_name";
13573 trace_mark(channel1, marker1, "hello %s", master_name)
13576 In this case, collecting @code{$_sdata} collects the string
13577 @samp{hello $yourname}. When analyzing the trace buffer, you can
13578 inspect @samp{$_sdata} like any other variable available to
13582 You can give several consecutive @code{collect} commands, each one
13583 with a single argument, or one @code{collect} command with several
13584 arguments separated by commas; the effect is the same.
13586 The optional @var{mods} changes the usual handling of the arguments.
13587 @code{s} requests that pointers to chars be handled as strings, in
13588 particular collecting the contents of the memory being pointed at, up
13589 to the first zero. The upper bound is by default the value of the
13590 @code{print elements} variable; if @code{s} is followed by a decimal
13591 number, that is the upper bound instead. So for instance
13592 @samp{collect/s25 mystr} collects as many as 25 characters at
13595 The command @code{info scope} (@pxref{Symbols, info scope}) is
13596 particularly useful for figuring out what data to collect.
13598 @kindex teval @r{(tracepoints)}
13599 @item teval @var{expr1}, @var{expr2}, @dots{}
13600 Evaluate the given expressions when the tracepoint is hit. This
13601 command accepts a comma-separated list of expressions. The results
13602 are discarded, so this is mainly useful for assigning values to trace
13603 state variables (@pxref{Trace State Variables}) without adding those
13604 values to the trace buffer, as would be the case if the @code{collect}
13607 @kindex while-stepping @r{(tracepoints)}
13608 @item while-stepping @var{n}
13609 Perform @var{n} single-step instruction traces after the tracepoint,
13610 collecting new data after each step. The @code{while-stepping}
13611 command is followed by the list of what to collect while stepping
13612 (followed by its own @code{end} command):
13615 > while-stepping 12
13616 > collect $regs, myglobal
13622 Note that @code{$pc} is not automatically collected by
13623 @code{while-stepping}; you need to explicitly collect that register if
13624 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13627 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13628 @kindex set default-collect
13629 @cindex default collection action
13630 This variable is a list of expressions to collect at each tracepoint
13631 hit. It is effectively an additional @code{collect} action prepended
13632 to every tracepoint action list. The expressions are parsed
13633 individually for each tracepoint, so for instance a variable named
13634 @code{xyz} may be interpreted as a global for one tracepoint, and a
13635 local for another, as appropriate to the tracepoint's location.
13637 @item show default-collect
13638 @kindex show default-collect
13639 Show the list of expressions that are collected by default at each
13644 @node Listing Tracepoints
13645 @subsection Listing Tracepoints
13648 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13649 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13650 @cindex information about tracepoints
13651 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13652 Display information about the tracepoint @var{num}. If you don't
13653 specify a tracepoint number, displays information about all the
13654 tracepoints defined so far. The format is similar to that used for
13655 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13656 command, simply restricting itself to tracepoints.
13658 A tracepoint's listing may include additional information specific to
13663 its passcount as given by the @code{passcount @var{n}} command
13666 the state about installed on target of each location
13670 (@value{GDBP}) @b{info trace}
13671 Num Type Disp Enb Address What
13672 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13674 collect globfoo, $regs
13679 2 tracepoint keep y <MULTIPLE>
13681 2.1 y 0x0804859c in func4 at change-loc.h:35
13682 installed on target
13683 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13684 installed on target
13685 2.3 y <PENDING> set_tracepoint
13686 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13687 not installed on target
13692 This command can be abbreviated @code{info tp}.
13695 @node Listing Static Tracepoint Markers
13696 @subsection Listing Static Tracepoint Markers
13699 @kindex info static-tracepoint-markers
13700 @cindex information about static tracepoint markers
13701 @item info static-tracepoint-markers
13702 Display information about all static tracepoint markers defined in the
13705 For each marker, the following columns are printed:
13709 An incrementing counter, output to help readability. This is not a
13712 The marker ID, as reported by the target.
13713 @item Enabled or Disabled
13714 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13715 that are not enabled.
13717 Where the marker is in your program, as a memory address.
13719 Where the marker is in the source for your program, as a file and line
13720 number. If the debug information included in the program does not
13721 allow @value{GDBN} to locate the source of the marker, this column
13722 will be left blank.
13726 In addition, the following information may be printed for each marker:
13730 User data passed to the tracing library by the marker call. In the
13731 UST backend, this is the format string passed as argument to the
13733 @item Static tracepoints probing the marker
13734 The list of static tracepoints attached to the marker.
13738 (@value{GDBP}) info static-tracepoint-markers
13739 Cnt ID Enb Address What
13740 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13741 Data: number1 %d number2 %d
13742 Probed by static tracepoints: #2
13743 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13749 @node Starting and Stopping Trace Experiments
13750 @subsection Starting and Stopping Trace Experiments
13753 @kindex tstart [ @var{notes} ]
13754 @cindex start a new trace experiment
13755 @cindex collected data discarded
13757 This command starts the trace experiment, and begins collecting data.
13758 It has the side effect of discarding all the data collected in the
13759 trace buffer during the previous trace experiment. If any arguments
13760 are supplied, they are taken as a note and stored with the trace
13761 experiment's state. The notes may be arbitrary text, and are
13762 especially useful with disconnected tracing in a multi-user context;
13763 the notes can explain what the trace is doing, supply user contact
13764 information, and so forth.
13766 @kindex tstop [ @var{notes} ]
13767 @cindex stop a running trace experiment
13769 This command stops the trace experiment. If any arguments are
13770 supplied, they are recorded with the experiment as a note. This is
13771 useful if you are stopping a trace started by someone else, for
13772 instance if the trace is interfering with the system's behavior and
13773 needs to be stopped quickly.
13775 @strong{Note}: a trace experiment and data collection may stop
13776 automatically if any tracepoint's passcount is reached
13777 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13780 @cindex status of trace data collection
13781 @cindex trace experiment, status of
13783 This command displays the status of the current trace data
13787 Here is an example of the commands we described so far:
13790 (@value{GDBP}) @b{trace gdb_c_test}
13791 (@value{GDBP}) @b{actions}
13792 Enter actions for tracepoint #1, one per line.
13793 > collect $regs,$locals,$args
13794 > while-stepping 11
13798 (@value{GDBP}) @b{tstart}
13799 [time passes @dots{}]
13800 (@value{GDBP}) @b{tstop}
13803 @anchor{disconnected tracing}
13804 @cindex disconnected tracing
13805 You can choose to continue running the trace experiment even if
13806 @value{GDBN} disconnects from the target, voluntarily or
13807 involuntarily. For commands such as @code{detach}, the debugger will
13808 ask what you want to do with the trace. But for unexpected
13809 terminations (@value{GDBN} crash, network outage), it would be
13810 unfortunate to lose hard-won trace data, so the variable
13811 @code{disconnected-tracing} lets you decide whether the trace should
13812 continue running without @value{GDBN}.
13815 @item set disconnected-tracing on
13816 @itemx set disconnected-tracing off
13817 @kindex set disconnected-tracing
13818 Choose whether a tracing run should continue to run if @value{GDBN}
13819 has disconnected from the target. Note that @code{detach} or
13820 @code{quit} will ask you directly what to do about a running trace no
13821 matter what this variable's setting, so the variable is mainly useful
13822 for handling unexpected situations, such as loss of the network.
13824 @item show disconnected-tracing
13825 @kindex show disconnected-tracing
13826 Show the current choice for disconnected tracing.
13830 When you reconnect to the target, the trace experiment may or may not
13831 still be running; it might have filled the trace buffer in the
13832 meantime, or stopped for one of the other reasons. If it is running,
13833 it will continue after reconnection.
13835 Upon reconnection, the target will upload information about the
13836 tracepoints in effect. @value{GDBN} will then compare that
13837 information to the set of tracepoints currently defined, and attempt
13838 to match them up, allowing for the possibility that the numbers may
13839 have changed due to creation and deletion in the meantime. If one of
13840 the target's tracepoints does not match any in @value{GDBN}, the
13841 debugger will create a new tracepoint, so that you have a number with
13842 which to specify that tracepoint. This matching-up process is
13843 necessarily heuristic, and it may result in useless tracepoints being
13844 created; you may simply delete them if they are of no use.
13846 @cindex circular trace buffer
13847 If your target agent supports a @dfn{circular trace buffer}, then you
13848 can run a trace experiment indefinitely without filling the trace
13849 buffer; when space runs out, the agent deletes already-collected trace
13850 frames, oldest first, until there is enough room to continue
13851 collecting. This is especially useful if your tracepoints are being
13852 hit too often, and your trace gets terminated prematurely because the
13853 buffer is full. To ask for a circular trace buffer, simply set
13854 @samp{circular-trace-buffer} to on. You can set this at any time,
13855 including during tracing; if the agent can do it, it will change
13856 buffer handling on the fly, otherwise it will not take effect until
13860 @item set circular-trace-buffer on
13861 @itemx set circular-trace-buffer off
13862 @kindex set circular-trace-buffer
13863 Choose whether a tracing run should use a linear or circular buffer
13864 for trace data. A linear buffer will not lose any trace data, but may
13865 fill up prematurely, while a circular buffer will discard old trace
13866 data, but it will have always room for the latest tracepoint hits.
13868 @item show circular-trace-buffer
13869 @kindex show circular-trace-buffer
13870 Show the current choice for the trace buffer. Note that this may not
13871 match the agent's current buffer handling, nor is it guaranteed to
13872 match the setting that might have been in effect during a past run,
13873 for instance if you are looking at frames from a trace file.
13878 @item set trace-buffer-size @var{n}
13879 @itemx set trace-buffer-size unlimited
13880 @kindex set trace-buffer-size
13881 Request that the target use a trace buffer of @var{n} bytes. Not all
13882 targets will honor the request; they may have a compiled-in size for
13883 the trace buffer, or some other limitation. Set to a value of
13884 @code{unlimited} or @code{-1} to let the target use whatever size it
13885 likes. This is also the default.
13887 @item show trace-buffer-size
13888 @kindex show trace-buffer-size
13889 Show the current requested size for the trace buffer. Note that this
13890 will only match the actual size if the target supports size-setting,
13891 and was able to handle the requested size. For instance, if the
13892 target can only change buffer size between runs, this variable will
13893 not reflect the change until the next run starts. Use @code{tstatus}
13894 to get a report of the actual buffer size.
13898 @item set trace-user @var{text}
13899 @kindex set trace-user
13901 @item show trace-user
13902 @kindex show trace-user
13904 @item set trace-notes @var{text}
13905 @kindex set trace-notes
13906 Set the trace run's notes.
13908 @item show trace-notes
13909 @kindex show trace-notes
13910 Show the trace run's notes.
13912 @item set trace-stop-notes @var{text}
13913 @kindex set trace-stop-notes
13914 Set the trace run's stop notes. The handling of the note is as for
13915 @code{tstop} arguments; the set command is convenient way to fix a
13916 stop note that is mistaken or incomplete.
13918 @item show trace-stop-notes
13919 @kindex show trace-stop-notes
13920 Show the trace run's stop notes.
13924 @node Tracepoint Restrictions
13925 @subsection Tracepoint Restrictions
13927 @cindex tracepoint restrictions
13928 There are a number of restrictions on the use of tracepoints. As
13929 described above, tracepoint data gathering occurs on the target
13930 without interaction from @value{GDBN}. Thus the full capabilities of
13931 the debugger are not available during data gathering, and then at data
13932 examination time, you will be limited by only having what was
13933 collected. The following items describe some common problems, but it
13934 is not exhaustive, and you may run into additional difficulties not
13940 Tracepoint expressions are intended to gather objects (lvalues). Thus
13941 the full flexibility of GDB's expression evaluator is not available.
13942 You cannot call functions, cast objects to aggregate types, access
13943 convenience variables or modify values (except by assignment to trace
13944 state variables). Some language features may implicitly call
13945 functions (for instance Objective-C fields with accessors), and therefore
13946 cannot be collected either.
13949 Collection of local variables, either individually or in bulk with
13950 @code{$locals} or @code{$args}, during @code{while-stepping} may
13951 behave erratically. The stepping action may enter a new scope (for
13952 instance by stepping into a function), or the location of the variable
13953 may change (for instance it is loaded into a register). The
13954 tracepoint data recorded uses the location information for the
13955 variables that is correct for the tracepoint location. When the
13956 tracepoint is created, it is not possible, in general, to determine
13957 where the steps of a @code{while-stepping} sequence will advance the
13958 program---particularly if a conditional branch is stepped.
13961 Collection of an incompletely-initialized or partially-destroyed object
13962 may result in something that @value{GDBN} cannot display, or displays
13963 in a misleading way.
13966 When @value{GDBN} displays a pointer to character it automatically
13967 dereferences the pointer to also display characters of the string
13968 being pointed to. However, collecting the pointer during tracing does
13969 not automatically collect the string. You need to explicitly
13970 dereference the pointer and provide size information if you want to
13971 collect not only the pointer, but the memory pointed to. For example,
13972 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13976 It is not possible to collect a complete stack backtrace at a
13977 tracepoint. Instead, you may collect the registers and a few hundred
13978 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13979 (adjust to use the name of the actual stack pointer register on your
13980 target architecture, and the amount of stack you wish to capture).
13981 Then the @code{backtrace} command will show a partial backtrace when
13982 using a trace frame. The number of stack frames that can be examined
13983 depends on the sizes of the frames in the collected stack. Note that
13984 if you ask for a block so large that it goes past the bottom of the
13985 stack, the target agent may report an error trying to read from an
13989 If you do not collect registers at a tracepoint, @value{GDBN} can
13990 infer that the value of @code{$pc} must be the same as the address of
13991 the tracepoint and use that when you are looking at a trace frame
13992 for that tracepoint. However, this cannot work if the tracepoint has
13993 multiple locations (for instance if it was set in a function that was
13994 inlined), or if it has a @code{while-stepping} loop. In those cases
13995 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
14000 @node Analyze Collected Data
14001 @section Using the Collected Data
14003 After the tracepoint experiment ends, you use @value{GDBN} commands
14004 for examining the trace data. The basic idea is that each tracepoint
14005 collects a trace @dfn{snapshot} every time it is hit and another
14006 snapshot every time it single-steps. All these snapshots are
14007 consecutively numbered from zero and go into a buffer, and you can
14008 examine them later. The way you examine them is to @dfn{focus} on a
14009 specific trace snapshot. When the remote stub is focused on a trace
14010 snapshot, it will respond to all @value{GDBN} requests for memory and
14011 registers by reading from the buffer which belongs to that snapshot,
14012 rather than from @emph{real} memory or registers of the program being
14013 debugged. This means that @strong{all} @value{GDBN} commands
14014 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
14015 behave as if we were currently debugging the program state as it was
14016 when the tracepoint occurred. Any requests for data that are not in
14017 the buffer will fail.
14020 * tfind:: How to select a trace snapshot
14021 * tdump:: How to display all data for a snapshot
14022 * save tracepoints:: How to save tracepoints for a future run
14026 @subsection @code{tfind @var{n}}
14029 @cindex select trace snapshot
14030 @cindex find trace snapshot
14031 The basic command for selecting a trace snapshot from the buffer is
14032 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
14033 counting from zero. If no argument @var{n} is given, the next
14034 snapshot is selected.
14036 Here are the various forms of using the @code{tfind} command.
14040 Find the first snapshot in the buffer. This is a synonym for
14041 @code{tfind 0} (since 0 is the number of the first snapshot).
14044 Stop debugging trace snapshots, resume @emph{live} debugging.
14047 Same as @samp{tfind none}.
14050 No argument means find the next trace snapshot or find the first
14051 one if no trace snapshot is selected.
14054 Find the previous trace snapshot before the current one. This permits
14055 retracing earlier steps.
14057 @item tfind tracepoint @var{num}
14058 Find the next snapshot associated with tracepoint @var{num}. Search
14059 proceeds forward from the last examined trace snapshot. If no
14060 argument @var{num} is given, it means find the next snapshot collected
14061 for the same tracepoint as the current snapshot.
14063 @item tfind pc @var{addr}
14064 Find the next snapshot associated with the value @var{addr} of the
14065 program counter. Search proceeds forward from the last examined trace
14066 snapshot. If no argument @var{addr} is given, it means find the next
14067 snapshot with the same value of PC as the current snapshot.
14069 @item tfind outside @var{addr1}, @var{addr2}
14070 Find the next snapshot whose PC is outside the given range of
14071 addresses (exclusive).
14073 @item tfind range @var{addr1}, @var{addr2}
14074 Find the next snapshot whose PC is between @var{addr1} and
14075 @var{addr2} (inclusive).
14077 @item tfind line @r{[}@var{file}:@r{]}@var{n}
14078 Find the next snapshot associated with the source line @var{n}. If
14079 the optional argument @var{file} is given, refer to line @var{n} in
14080 that source file. Search proceeds forward from the last examined
14081 trace snapshot. If no argument @var{n} is given, it means find the
14082 next line other than the one currently being examined; thus saying
14083 @code{tfind line} repeatedly can appear to have the same effect as
14084 stepping from line to line in a @emph{live} debugging session.
14087 The default arguments for the @code{tfind} commands are specifically
14088 designed to make it easy to scan through the trace buffer. For
14089 instance, @code{tfind} with no argument selects the next trace
14090 snapshot, and @code{tfind -} with no argument selects the previous
14091 trace snapshot. So, by giving one @code{tfind} command, and then
14092 simply hitting @key{RET} repeatedly you can examine all the trace
14093 snapshots in order. Or, by saying @code{tfind -} and then hitting
14094 @key{RET} repeatedly you can examine the snapshots in reverse order.
14095 The @code{tfind line} command with no argument selects the snapshot
14096 for the next source line executed. The @code{tfind pc} command with
14097 no argument selects the next snapshot with the same program counter
14098 (PC) as the current frame. The @code{tfind tracepoint} command with
14099 no argument selects the next trace snapshot collected by the same
14100 tracepoint as the current one.
14102 In addition to letting you scan through the trace buffer manually,
14103 these commands make it easy to construct @value{GDBN} scripts that
14104 scan through the trace buffer and print out whatever collected data
14105 you are interested in. Thus, if we want to examine the PC, FP, and SP
14106 registers from each trace frame in the buffer, we can say this:
14109 (@value{GDBP}) @b{tfind start}
14110 (@value{GDBP}) @b{while ($trace_frame != -1)}
14111 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
14112 $trace_frame, $pc, $sp, $fp
14116 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
14117 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
14118 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
14119 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
14120 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
14121 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
14122 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
14123 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
14124 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
14125 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
14126 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
14129 Or, if we want to examine the variable @code{X} at each source line in
14133 (@value{GDBP}) @b{tfind start}
14134 (@value{GDBP}) @b{while ($trace_frame != -1)}
14135 > printf "Frame %d, X == %d\n", $trace_frame, X
14145 @subsection @code{tdump}
14147 @cindex dump all data collected at tracepoint
14148 @cindex tracepoint data, display
14150 This command takes no arguments. It prints all the data collected at
14151 the current trace snapshot.
14154 (@value{GDBP}) @b{trace 444}
14155 (@value{GDBP}) @b{actions}
14156 Enter actions for tracepoint #2, one per line:
14157 > collect $regs, $locals, $args, gdb_long_test
14160 (@value{GDBP}) @b{tstart}
14162 (@value{GDBP}) @b{tfind line 444}
14163 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
14165 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
14167 (@value{GDBP}) @b{tdump}
14168 Data collected at tracepoint 2, trace frame 1:
14169 d0 0xc4aa0085 -995491707
14173 d4 0x71aea3d 119204413
14176 d7 0x380035 3670069
14177 a0 0x19e24a 1696330
14178 a1 0x3000668 50333288
14180 a3 0x322000 3284992
14181 a4 0x3000698 50333336
14182 a5 0x1ad3cc 1758156
14183 fp 0x30bf3c 0x30bf3c
14184 sp 0x30bf34 0x30bf34
14186 pc 0x20b2c8 0x20b2c8
14190 p = 0x20e5b4 "gdb-test"
14197 gdb_long_test = 17 '\021'
14202 @code{tdump} works by scanning the tracepoint's current collection
14203 actions and printing the value of each expression listed. So
14204 @code{tdump} can fail, if after a run, you change the tracepoint's
14205 actions to mention variables that were not collected during the run.
14207 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
14208 uses the collected value of @code{$pc} to distinguish between trace
14209 frames that were collected at the tracepoint hit, and frames that were
14210 collected while stepping. This allows it to correctly choose whether
14211 to display the basic list of collections, or the collections from the
14212 body of the while-stepping loop. However, if @code{$pc} was not collected,
14213 then @code{tdump} will always attempt to dump using the basic collection
14214 list, and may fail if a while-stepping frame does not include all the
14215 same data that is collected at the tracepoint hit.
14216 @c This is getting pretty arcane, example would be good.
14218 @node save tracepoints
14219 @subsection @code{save tracepoints @var{filename}}
14220 @kindex save tracepoints
14221 @kindex save-tracepoints
14222 @cindex save tracepoints for future sessions
14224 This command saves all current tracepoint definitions together with
14225 their actions and passcounts, into a file @file{@var{filename}}
14226 suitable for use in a later debugging session. To read the saved
14227 tracepoint definitions, use the @code{source} command (@pxref{Command
14228 Files}). The @w{@code{save-tracepoints}} command is a deprecated
14229 alias for @w{@code{save tracepoints}}
14231 @node Tracepoint Variables
14232 @section Convenience Variables for Tracepoints
14233 @cindex tracepoint variables
14234 @cindex convenience variables for tracepoints
14237 @vindex $trace_frame
14238 @item (int) $trace_frame
14239 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
14240 snapshot is selected.
14242 @vindex $tracepoint
14243 @item (int) $tracepoint
14244 The tracepoint for the current trace snapshot.
14246 @vindex $trace_line
14247 @item (int) $trace_line
14248 The line number for the current trace snapshot.
14250 @vindex $trace_file
14251 @item (char []) $trace_file
14252 The source file for the current trace snapshot.
14254 @vindex $trace_func
14255 @item (char []) $trace_func
14256 The name of the function containing @code{$tracepoint}.
14259 Note: @code{$trace_file} is not suitable for use in @code{printf},
14260 use @code{output} instead.
14262 Here's a simple example of using these convenience variables for
14263 stepping through all the trace snapshots and printing some of their
14264 data. Note that these are not the same as trace state variables,
14265 which are managed by the target.
14268 (@value{GDBP}) @b{tfind start}
14270 (@value{GDBP}) @b{while $trace_frame != -1}
14271 > output $trace_file
14272 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
14278 @section Using Trace Files
14279 @cindex trace files
14281 In some situations, the target running a trace experiment may no
14282 longer be available; perhaps it crashed, or the hardware was needed
14283 for a different activity. To handle these cases, you can arrange to
14284 dump the trace data into a file, and later use that file as a source
14285 of trace data, via the @code{target tfile} command.
14290 @item tsave [ -r ] @var{filename}
14291 @itemx tsave [-ctf] @var{dirname}
14292 Save the trace data to @var{filename}. By default, this command
14293 assumes that @var{filename} refers to the host filesystem, so if
14294 necessary @value{GDBN} will copy raw trace data up from the target and
14295 then save it. If the target supports it, you can also supply the
14296 optional argument @code{-r} (``remote'') to direct the target to save
14297 the data directly into @var{filename} in its own filesystem, which may be
14298 more efficient if the trace buffer is very large. (Note, however, that
14299 @code{target tfile} can only read from files accessible to the host.)
14300 By default, this command will save trace frame in tfile format.
14301 You can supply the optional argument @code{-ctf} to save data in CTF
14302 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
14303 that can be shared by multiple debugging and tracing tools. Please go to
14304 @indicateurl{http://www.efficios.com/ctf} to get more information.
14306 @kindex target tfile
14310 @item target tfile @var{filename}
14311 @itemx target ctf @var{dirname}
14312 Use the file named @var{filename} or directory named @var{dirname} as
14313 a source of trace data. Commands that examine data work as they do with
14314 a live target, but it is not possible to run any new trace experiments.
14315 @code{tstatus} will report the state of the trace run at the moment
14316 the data was saved, as well as the current trace frame you are examining.
14317 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
14321 (@value{GDBP}) target ctf ctf.ctf
14322 (@value{GDBP}) tfind
14323 Found trace frame 0, tracepoint 2
14324 39 ++a; /* set tracepoint 1 here */
14325 (@value{GDBP}) tdump
14326 Data collected at tracepoint 2, trace frame 0:
14330 c = @{"123", "456", "789", "123", "456", "789"@}
14331 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
14339 @chapter Debugging Programs That Use Overlays
14342 If your program is too large to fit completely in your target system's
14343 memory, you can sometimes use @dfn{overlays} to work around this
14344 problem. @value{GDBN} provides some support for debugging programs that
14348 * How Overlays Work:: A general explanation of overlays.
14349 * Overlay Commands:: Managing overlays in @value{GDBN}.
14350 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
14351 mapped by asking the inferior.
14352 * Overlay Sample Program:: A sample program using overlays.
14355 @node How Overlays Work
14356 @section How Overlays Work
14357 @cindex mapped overlays
14358 @cindex unmapped overlays
14359 @cindex load address, overlay's
14360 @cindex mapped address
14361 @cindex overlay area
14363 Suppose you have a computer whose instruction address space is only 64
14364 kilobytes long, but which has much more memory which can be accessed by
14365 other means: special instructions, segment registers, or memory
14366 management hardware, for example. Suppose further that you want to
14367 adapt a program which is larger than 64 kilobytes to run on this system.
14369 One solution is to identify modules of your program which are relatively
14370 independent, and need not call each other directly; call these modules
14371 @dfn{overlays}. Separate the overlays from the main program, and place
14372 their machine code in the larger memory. Place your main program in
14373 instruction memory, but leave at least enough space there to hold the
14374 largest overlay as well.
14376 Now, to call a function located in an overlay, you must first copy that
14377 overlay's machine code from the large memory into the space set aside
14378 for it in the instruction memory, and then jump to its entry point
14381 @c NB: In the below the mapped area's size is greater or equal to the
14382 @c size of all overlays. This is intentional to remind the developer
14383 @c that overlays don't necessarily need to be the same size.
14387 Data Instruction Larger
14388 Address Space Address Space Address Space
14389 +-----------+ +-----------+ +-----------+
14391 +-----------+ +-----------+ +-----------+<-- overlay 1
14392 | program | | main | .----| overlay 1 | load address
14393 | variables | | program | | +-----------+
14394 | and heap | | | | | |
14395 +-----------+ | | | +-----------+<-- overlay 2
14396 | | +-----------+ | | | load address
14397 +-----------+ | | | .-| overlay 2 |
14399 mapped --->+-----------+ | | +-----------+
14400 address | | | | | |
14401 | overlay | <-' | | |
14402 | area | <---' +-----------+<-- overlay 3
14403 | | <---. | | load address
14404 +-----------+ `--| overlay 3 |
14411 @anchor{A code overlay}A code overlay
14415 The diagram (@pxref{A code overlay}) shows a system with separate data
14416 and instruction address spaces. To map an overlay, the program copies
14417 its code from the larger address space to the instruction address space.
14418 Since the overlays shown here all use the same mapped address, only one
14419 may be mapped at a time. For a system with a single address space for
14420 data and instructions, the diagram would be similar, except that the
14421 program variables and heap would share an address space with the main
14422 program and the overlay area.
14424 An overlay loaded into instruction memory and ready for use is called a
14425 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
14426 instruction memory. An overlay not present (or only partially present)
14427 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
14428 is its address in the larger memory. The mapped address is also called
14429 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
14430 called the @dfn{load memory address}, or @dfn{LMA}.
14432 Unfortunately, overlays are not a completely transparent way to adapt a
14433 program to limited instruction memory. They introduce a new set of
14434 global constraints you must keep in mind as you design your program:
14439 Before calling or returning to a function in an overlay, your program
14440 must make sure that overlay is actually mapped. Otherwise, the call or
14441 return will transfer control to the right address, but in the wrong
14442 overlay, and your program will probably crash.
14445 If the process of mapping an overlay is expensive on your system, you
14446 will need to choose your overlays carefully to minimize their effect on
14447 your program's performance.
14450 The executable file you load onto your system must contain each
14451 overlay's instructions, appearing at the overlay's load address, not its
14452 mapped address. However, each overlay's instructions must be relocated
14453 and its symbols defined as if the overlay were at its mapped address.
14454 You can use GNU linker scripts to specify different load and relocation
14455 addresses for pieces of your program; see @ref{Overlay Description,,,
14456 ld.info, Using ld: the GNU linker}.
14459 The procedure for loading executable files onto your system must be able
14460 to load their contents into the larger address space as well as the
14461 instruction and data spaces.
14465 The overlay system described above is rather simple, and could be
14466 improved in many ways:
14471 If your system has suitable bank switch registers or memory management
14472 hardware, you could use those facilities to make an overlay's load area
14473 contents simply appear at their mapped address in instruction space.
14474 This would probably be faster than copying the overlay to its mapped
14475 area in the usual way.
14478 If your overlays are small enough, you could set aside more than one
14479 overlay area, and have more than one overlay mapped at a time.
14482 You can use overlays to manage data, as well as instructions. In
14483 general, data overlays are even less transparent to your design than
14484 code overlays: whereas code overlays only require care when you call or
14485 return to functions, data overlays require care every time you access
14486 the data. Also, if you change the contents of a data overlay, you
14487 must copy its contents back out to its load address before you can copy a
14488 different data overlay into the same mapped area.
14493 @node Overlay Commands
14494 @section Overlay Commands
14496 To use @value{GDBN}'s overlay support, each overlay in your program must
14497 correspond to a separate section of the executable file. The section's
14498 virtual memory address and load memory address must be the overlay's
14499 mapped and load addresses. Identifying overlays with sections allows
14500 @value{GDBN} to determine the appropriate address of a function or
14501 variable, depending on whether the overlay is mapped or not.
14503 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14504 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14509 Disable @value{GDBN}'s overlay support. When overlay support is
14510 disabled, @value{GDBN} assumes that all functions and variables are
14511 always present at their mapped addresses. By default, @value{GDBN}'s
14512 overlay support is disabled.
14514 @item overlay manual
14515 @cindex manual overlay debugging
14516 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14517 relies on you to tell it which overlays are mapped, and which are not,
14518 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14519 commands described below.
14521 @item overlay map-overlay @var{overlay}
14522 @itemx overlay map @var{overlay}
14523 @cindex map an overlay
14524 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14525 be the name of the object file section containing the overlay. When an
14526 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14527 functions and variables at their mapped addresses. @value{GDBN} assumes
14528 that any other overlays whose mapped ranges overlap that of
14529 @var{overlay} are now unmapped.
14531 @item overlay unmap-overlay @var{overlay}
14532 @itemx overlay unmap @var{overlay}
14533 @cindex unmap an overlay
14534 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14535 must be the name of the object file section containing the overlay.
14536 When an overlay is unmapped, @value{GDBN} assumes it can find the
14537 overlay's functions and variables at their load addresses.
14540 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14541 consults a data structure the overlay manager maintains in the inferior
14542 to see which overlays are mapped. For details, see @ref{Automatic
14543 Overlay Debugging}.
14545 @item overlay load-target
14546 @itemx overlay load
14547 @cindex reloading the overlay table
14548 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14549 re-reads the table @value{GDBN} automatically each time the inferior
14550 stops, so this command should only be necessary if you have changed the
14551 overlay mapping yourself using @value{GDBN}. This command is only
14552 useful when using automatic overlay debugging.
14554 @item overlay list-overlays
14555 @itemx overlay list
14556 @cindex listing mapped overlays
14557 Display a list of the overlays currently mapped, along with their mapped
14558 addresses, load addresses, and sizes.
14562 Normally, when @value{GDBN} prints a code address, it includes the name
14563 of the function the address falls in:
14566 (@value{GDBP}) print main
14567 $3 = @{int ()@} 0x11a0 <main>
14570 When overlay debugging is enabled, @value{GDBN} recognizes code in
14571 unmapped overlays, and prints the names of unmapped functions with
14572 asterisks around them. For example, if @code{foo} is a function in an
14573 unmapped overlay, @value{GDBN} prints it this way:
14576 (@value{GDBP}) overlay list
14577 No sections are mapped.
14578 (@value{GDBP}) print foo
14579 $5 = @{int (int)@} 0x100000 <*foo*>
14582 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14586 (@value{GDBP}) overlay list
14587 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14588 mapped at 0x1016 - 0x104a
14589 (@value{GDBP}) print foo
14590 $6 = @{int (int)@} 0x1016 <foo>
14593 When overlay debugging is enabled, @value{GDBN} can find the correct
14594 address for functions and variables in an overlay, whether or not the
14595 overlay is mapped. This allows most @value{GDBN} commands, like
14596 @code{break} and @code{disassemble}, to work normally, even on unmapped
14597 code. However, @value{GDBN}'s breakpoint support has some limitations:
14601 @cindex breakpoints in overlays
14602 @cindex overlays, setting breakpoints in
14603 You can set breakpoints in functions in unmapped overlays, as long as
14604 @value{GDBN} can write to the overlay at its load address.
14606 @value{GDBN} can not set hardware or simulator-based breakpoints in
14607 unmapped overlays. However, if you set a breakpoint at the end of your
14608 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14609 you are using manual overlay management), @value{GDBN} will re-set its
14610 breakpoints properly.
14614 @node Automatic Overlay Debugging
14615 @section Automatic Overlay Debugging
14616 @cindex automatic overlay debugging
14618 @value{GDBN} can automatically track which overlays are mapped and which
14619 are not, given some simple co-operation from the overlay manager in the
14620 inferior. If you enable automatic overlay debugging with the
14621 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14622 looks in the inferior's memory for certain variables describing the
14623 current state of the overlays.
14625 Here are the variables your overlay manager must define to support
14626 @value{GDBN}'s automatic overlay debugging:
14630 @item @code{_ovly_table}:
14631 This variable must be an array of the following structures:
14636 /* The overlay's mapped address. */
14639 /* The size of the overlay, in bytes. */
14640 unsigned long size;
14642 /* The overlay's load address. */
14645 /* Non-zero if the overlay is currently mapped;
14647 unsigned long mapped;
14651 @item @code{_novlys}:
14652 This variable must be a four-byte signed integer, holding the total
14653 number of elements in @code{_ovly_table}.
14657 To decide whether a particular overlay is mapped or not, @value{GDBN}
14658 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14659 @code{lma} members equal the VMA and LMA of the overlay's section in the
14660 executable file. When @value{GDBN} finds a matching entry, it consults
14661 the entry's @code{mapped} member to determine whether the overlay is
14664 In addition, your overlay manager may define a function called
14665 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14666 will silently set a breakpoint there. If the overlay manager then
14667 calls this function whenever it has changed the overlay table, this
14668 will enable @value{GDBN} to accurately keep track of which overlays
14669 are in program memory, and update any breakpoints that may be set
14670 in overlays. This will allow breakpoints to work even if the
14671 overlays are kept in ROM or other non-writable memory while they
14672 are not being executed.
14674 @node Overlay Sample Program
14675 @section Overlay Sample Program
14676 @cindex overlay example program
14678 When linking a program which uses overlays, you must place the overlays
14679 at their load addresses, while relocating them to run at their mapped
14680 addresses. To do this, you must write a linker script (@pxref{Overlay
14681 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14682 since linker scripts are specific to a particular host system, target
14683 architecture, and target memory layout, this manual cannot provide
14684 portable sample code demonstrating @value{GDBN}'s overlay support.
14686 However, the @value{GDBN} source distribution does contain an overlaid
14687 program, with linker scripts for a few systems, as part of its test
14688 suite. The program consists of the following files from
14689 @file{gdb/testsuite/gdb.base}:
14693 The main program file.
14695 A simple overlay manager, used by @file{overlays.c}.
14700 Overlay modules, loaded and used by @file{overlays.c}.
14703 Linker scripts for linking the test program on the @code{d10v-elf}
14704 and @code{m32r-elf} targets.
14707 You can build the test program using the @code{d10v-elf} GCC
14708 cross-compiler like this:
14711 $ d10v-elf-gcc -g -c overlays.c
14712 $ d10v-elf-gcc -g -c ovlymgr.c
14713 $ d10v-elf-gcc -g -c foo.c
14714 $ d10v-elf-gcc -g -c bar.c
14715 $ d10v-elf-gcc -g -c baz.c
14716 $ d10v-elf-gcc -g -c grbx.c
14717 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14718 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14721 The build process is identical for any other architecture, except that
14722 you must substitute the appropriate compiler and linker script for the
14723 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14727 @chapter Using @value{GDBN} with Different Languages
14730 Although programming languages generally have common aspects, they are
14731 rarely expressed in the same manner. For instance, in ANSI C,
14732 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14733 Modula-2, it is accomplished by @code{p^}. Values can also be
14734 represented (and displayed) differently. Hex numbers in C appear as
14735 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14737 @cindex working language
14738 Language-specific information is built into @value{GDBN} for some languages,
14739 allowing you to express operations like the above in your program's
14740 native language, and allowing @value{GDBN} to output values in a manner
14741 consistent with the syntax of your program's native language. The
14742 language you use to build expressions is called the @dfn{working
14746 * Setting:: Switching between source languages
14747 * Show:: Displaying the language
14748 * Checks:: Type and range checks
14749 * Supported Languages:: Supported languages
14750 * Unsupported Languages:: Unsupported languages
14754 @section Switching Between Source Languages
14756 There are two ways to control the working language---either have @value{GDBN}
14757 set it automatically, or select it manually yourself. You can use the
14758 @code{set language} command for either purpose. On startup, @value{GDBN}
14759 defaults to setting the language automatically. The working language is
14760 used to determine how expressions you type are interpreted, how values
14763 In addition to the working language, every source file that
14764 @value{GDBN} knows about has its own working language. For some object
14765 file formats, the compiler might indicate which language a particular
14766 source file is in. However, most of the time @value{GDBN} infers the
14767 language from the name of the file. The language of a source file
14768 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14769 show each frame appropriately for its own language. There is no way to
14770 set the language of a source file from within @value{GDBN}, but you can
14771 set the language associated with a filename extension. @xref{Show, ,
14772 Displaying the Language}.
14774 This is most commonly a problem when you use a program, such
14775 as @code{cfront} or @code{f2c}, that generates C but is written in
14776 another language. In that case, make the
14777 program use @code{#line} directives in its C output; that way
14778 @value{GDBN} will know the correct language of the source code of the original
14779 program, and will display that source code, not the generated C code.
14782 * Filenames:: Filename extensions and languages.
14783 * Manually:: Setting the working language manually
14784 * Automatically:: Having @value{GDBN} infer the source language
14788 @subsection List of Filename Extensions and Languages
14790 If a source file name ends in one of the following extensions, then
14791 @value{GDBN} infers that its language is the one indicated.
14809 C@t{++} source file
14815 Objective-C source file
14819 Fortran source file
14822 Modula-2 source file
14826 Assembler source file. This actually behaves almost like C, but
14827 @value{GDBN} does not skip over function prologues when stepping.
14830 In addition, you may set the language associated with a filename
14831 extension. @xref{Show, , Displaying the Language}.
14834 @subsection Setting the Working Language
14836 If you allow @value{GDBN} to set the language automatically,
14837 expressions are interpreted the same way in your debugging session and
14840 @kindex set language
14841 If you wish, you may set the language manually. To do this, issue the
14842 command @samp{set language @var{lang}}, where @var{lang} is the name of
14843 a language, such as
14844 @code{c} or @code{modula-2}.
14845 For a list of the supported languages, type @samp{set language}.
14847 Setting the language manually prevents @value{GDBN} from updating the working
14848 language automatically. This can lead to confusion if you try
14849 to debug a program when the working language is not the same as the
14850 source language, when an expression is acceptable to both
14851 languages---but means different things. For instance, if the current
14852 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14860 might not have the effect you intended. In C, this means to add
14861 @code{b} and @code{c} and place the result in @code{a}. The result
14862 printed would be the value of @code{a}. In Modula-2, this means to compare
14863 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14865 @node Automatically
14866 @subsection Having @value{GDBN} Infer the Source Language
14868 To have @value{GDBN} set the working language automatically, use
14869 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14870 then infers the working language. That is, when your program stops in a
14871 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14872 working language to the language recorded for the function in that
14873 frame. If the language for a frame is unknown (that is, if the function
14874 or block corresponding to the frame was defined in a source file that
14875 does not have a recognized extension), the current working language is
14876 not changed, and @value{GDBN} issues a warning.
14878 This may not seem necessary for most programs, which are written
14879 entirely in one source language. However, program modules and libraries
14880 written in one source language can be used by a main program written in
14881 a different source language. Using @samp{set language auto} in this
14882 case frees you from having to set the working language manually.
14885 @section Displaying the Language
14887 The following commands help you find out which language is the
14888 working language, and also what language source files were written in.
14891 @item show language
14892 @anchor{show language}
14893 @kindex show language
14894 Display the current working language. This is the
14895 language you can use with commands such as @code{print} to
14896 build and compute expressions that may involve variables in your program.
14899 @kindex info frame@r{, show the source language}
14900 Display the source language for this frame. This language becomes the
14901 working language if you use an identifier from this frame.
14902 @xref{Frame Info, ,Information about a Frame}, to identify the other
14903 information listed here.
14906 @kindex info source@r{, show the source language}
14907 Display the source language of this source file.
14908 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14909 information listed here.
14912 In unusual circumstances, you may have source files with extensions
14913 not in the standard list. You can then set the extension associated
14914 with a language explicitly:
14917 @item set extension-language @var{ext} @var{language}
14918 @kindex set extension-language
14919 Tell @value{GDBN} that source files with extension @var{ext} are to be
14920 assumed as written in the source language @var{language}.
14922 @item info extensions
14923 @kindex info extensions
14924 List all the filename extensions and the associated languages.
14928 @section Type and Range Checking
14930 Some languages are designed to guard you against making seemingly common
14931 errors through a series of compile- and run-time checks. These include
14932 checking the type of arguments to functions and operators and making
14933 sure mathematical overflows are caught at run time. Checks such as
14934 these help to ensure a program's correctness once it has been compiled
14935 by eliminating type mismatches and providing active checks for range
14936 errors when your program is running.
14938 By default @value{GDBN} checks for these errors according to the
14939 rules of the current source language. Although @value{GDBN} does not check
14940 the statements in your program, it can check expressions entered directly
14941 into @value{GDBN} for evaluation via the @code{print} command, for example.
14944 * Type Checking:: An overview of type checking
14945 * Range Checking:: An overview of range checking
14948 @cindex type checking
14949 @cindex checks, type
14950 @node Type Checking
14951 @subsection An Overview of Type Checking
14953 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14954 arguments to operators and functions have to be of the correct type,
14955 otherwise an error occurs. These checks prevent type mismatch
14956 errors from ever causing any run-time problems. For example,
14959 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14961 (@value{GDBP}) print obj.my_method (0)
14964 (@value{GDBP}) print obj.my_method (0x1234)
14965 Cannot resolve method klass::my_method to any overloaded instance
14968 The second example fails because in C@t{++} the integer constant
14969 @samp{0x1234} is not type-compatible with the pointer parameter type.
14971 For the expressions you use in @value{GDBN} commands, you can tell
14972 @value{GDBN} to not enforce strict type checking or
14973 to treat any mismatches as errors and abandon the expression;
14974 When type checking is disabled, @value{GDBN} successfully evaluates
14975 expressions like the second example above.
14977 Even if type checking is off, there may be other reasons
14978 related to type that prevent @value{GDBN} from evaluating an expression.
14979 For instance, @value{GDBN} does not know how to add an @code{int} and
14980 a @code{struct foo}. These particular type errors have nothing to do
14981 with the language in use and usually arise from expressions which make
14982 little sense to evaluate anyway.
14984 @value{GDBN} provides some additional commands for controlling type checking:
14986 @kindex set check type
14987 @kindex show check type
14989 @item set check type on
14990 @itemx set check type off
14991 Set strict type checking on or off. If any type mismatches occur in
14992 evaluating an expression while type checking is on, @value{GDBN} prints a
14993 message and aborts evaluation of the expression.
14995 @item show check type
14996 Show the current setting of type checking and whether @value{GDBN}
14997 is enforcing strict type checking rules.
15000 @cindex range checking
15001 @cindex checks, range
15002 @node Range Checking
15003 @subsection An Overview of Range Checking
15005 In some languages (such as Modula-2), it is an error to exceed the
15006 bounds of a type; this is enforced with run-time checks. Such range
15007 checking is meant to ensure program correctness by making sure
15008 computations do not overflow, or indices on an array element access do
15009 not exceed the bounds of the array.
15011 For expressions you use in @value{GDBN} commands, you can tell
15012 @value{GDBN} to treat range errors in one of three ways: ignore them,
15013 always treat them as errors and abandon the expression, or issue
15014 warnings but evaluate the expression anyway.
15016 A range error can result from numerical overflow, from exceeding an
15017 array index bound, or when you type a constant that is not a member
15018 of any type. Some languages, however, do not treat overflows as an
15019 error. In many implementations of C, mathematical overflow causes the
15020 result to ``wrap around'' to lower values---for example, if @var{m} is
15021 the largest integer value, and @var{s} is the smallest, then
15024 @var{m} + 1 @result{} @var{s}
15027 This, too, is specific to individual languages, and in some cases
15028 specific to individual compilers or machines. @xref{Supported Languages, ,
15029 Supported Languages}, for further details on specific languages.
15031 @value{GDBN} provides some additional commands for controlling the range checker:
15033 @kindex set check range
15034 @kindex show check range
15036 @item set check range auto
15037 Set range checking on or off based on the current working language.
15038 @xref{Supported Languages, ,Supported Languages}, for the default settings for
15041 @item set check range on
15042 @itemx set check range off
15043 Set range checking on or off, overriding the default setting for the
15044 current working language. A warning is issued if the setting does not
15045 match the language default. If a range error occurs and range checking is on,
15046 then a message is printed and evaluation of the expression is aborted.
15048 @item set check range warn
15049 Output messages when the @value{GDBN} range checker detects a range error,
15050 but attempt to evaluate the expression anyway. Evaluating the
15051 expression may still be impossible for other reasons, such as accessing
15052 memory that the process does not own (a typical example from many Unix
15056 Show the current setting of the range checker, and whether or not it is
15057 being set automatically by @value{GDBN}.
15060 @node Supported Languages
15061 @section Supported Languages
15063 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
15064 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
15065 @c This is false ...
15066 Some @value{GDBN} features may be used in expressions regardless of the
15067 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
15068 and the @samp{@{type@}addr} construct (@pxref{Expressions,
15069 ,Expressions}) can be used with the constructs of any supported
15072 The following sections detail to what degree each source language is
15073 supported by @value{GDBN}. These sections are not meant to be language
15074 tutorials or references, but serve only as a reference guide to what the
15075 @value{GDBN} expression parser accepts, and what input and output
15076 formats should look like for different languages. There are many good
15077 books written on each of these languages; please look to these for a
15078 language reference or tutorial.
15081 * C:: C and C@t{++}
15084 * Objective-C:: Objective-C
15085 * OpenCL C:: OpenCL C
15086 * Fortran:: Fortran
15089 * Modula-2:: Modula-2
15094 @subsection C and C@t{++}
15096 @cindex C and C@t{++}
15097 @cindex expressions in C or C@t{++}
15099 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
15100 to both languages. Whenever this is the case, we discuss those languages
15104 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
15105 @cindex @sc{gnu} C@t{++}
15106 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
15107 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
15108 effectively, you must compile your C@t{++} programs with a supported
15109 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
15110 compiler (@code{aCC}).
15113 * C Operators:: C and C@t{++} operators
15114 * C Constants:: C and C@t{++} constants
15115 * C Plus Plus Expressions:: C@t{++} expressions
15116 * C Defaults:: Default settings for C and C@t{++}
15117 * C Checks:: C and C@t{++} type and range checks
15118 * Debugging C:: @value{GDBN} and C
15119 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
15120 * Decimal Floating Point:: Numbers in Decimal Floating Point format
15124 @subsubsection C and C@t{++} Operators
15126 @cindex C and C@t{++} operators
15128 Operators must be defined on values of specific types. For instance,
15129 @code{+} is defined on numbers, but not on structures. Operators are
15130 often defined on groups of types.
15132 For the purposes of C and C@t{++}, the following definitions hold:
15137 @emph{Integral types} include @code{int} with any of its storage-class
15138 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
15141 @emph{Floating-point types} include @code{float}, @code{double}, and
15142 @code{long double} (if supported by the target platform).
15145 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
15148 @emph{Scalar types} include all of the above.
15153 The following operators are supported. They are listed here
15154 in order of increasing precedence:
15158 The comma or sequencing operator. Expressions in a comma-separated list
15159 are evaluated from left to right, with the result of the entire
15160 expression being the last expression evaluated.
15163 Assignment. The value of an assignment expression is the value
15164 assigned. Defined on scalar types.
15167 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
15168 and translated to @w{@code{@var{a} = @var{a op b}}}.
15169 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
15170 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
15171 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
15174 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
15175 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
15176 should be of an integral type.
15179 Logical @sc{or}. Defined on integral types.
15182 Logical @sc{and}. Defined on integral types.
15185 Bitwise @sc{or}. Defined on integral types.
15188 Bitwise exclusive-@sc{or}. Defined on integral types.
15191 Bitwise @sc{and}. Defined on integral types.
15194 Equality and inequality. Defined on scalar types. The value of these
15195 expressions is 0 for false and non-zero for true.
15197 @item <@r{, }>@r{, }<=@r{, }>=
15198 Less than, greater than, less than or equal, greater than or equal.
15199 Defined on scalar types. The value of these expressions is 0 for false
15200 and non-zero for true.
15203 left shift, and right shift. Defined on integral types.
15206 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15209 Addition and subtraction. Defined on integral types, floating-point types and
15212 @item *@r{, }/@r{, }%
15213 Multiplication, division, and modulus. Multiplication and division are
15214 defined on integral and floating-point types. Modulus is defined on
15218 Increment and decrement. When appearing before a variable, the
15219 operation is performed before the variable is used in an expression;
15220 when appearing after it, the variable's value is used before the
15221 operation takes place.
15224 Pointer dereferencing. Defined on pointer types. Same precedence as
15228 Address operator. Defined on variables. Same precedence as @code{++}.
15230 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
15231 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
15232 to examine the address
15233 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
15237 Negative. Defined on integral and floating-point types. Same
15238 precedence as @code{++}.
15241 Logical negation. Defined on integral types. Same precedence as
15245 Bitwise complement operator. Defined on integral types. Same precedence as
15250 Structure member, and pointer-to-structure member. For convenience,
15251 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
15252 pointer based on the stored type information.
15253 Defined on @code{struct} and @code{union} data.
15256 Dereferences of pointers to members.
15259 Array indexing. @code{@var{a}[@var{i}]} is defined as
15260 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
15263 Function parameter list. Same precedence as @code{->}.
15266 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
15267 and @code{class} types.
15270 Doubled colons also represent the @value{GDBN} scope operator
15271 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
15275 If an operator is redefined in the user code, @value{GDBN} usually
15276 attempts to invoke the redefined version instead of using the operator's
15277 predefined meaning.
15280 @subsubsection C and C@t{++} Constants
15282 @cindex C and C@t{++} constants
15284 @value{GDBN} allows you to express the constants of C and C@t{++} in the
15289 Integer constants are a sequence of digits. Octal constants are
15290 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
15291 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
15292 @samp{l}, specifying that the constant should be treated as a
15296 Floating point constants are a sequence of digits, followed by a decimal
15297 point, followed by a sequence of digits, and optionally followed by an
15298 exponent. An exponent is of the form:
15299 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
15300 sequence of digits. The @samp{+} is optional for positive exponents.
15301 A floating-point constant may also end with a letter @samp{f} or
15302 @samp{F}, specifying that the constant should be treated as being of
15303 the @code{float} (as opposed to the default @code{double}) type; or with
15304 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
15308 Enumerated constants consist of enumerated identifiers, or their
15309 integral equivalents.
15312 Character constants are a single character surrounded by single quotes
15313 (@code{'}), or a number---the ordinal value of the corresponding character
15314 (usually its @sc{ascii} value). Within quotes, the single character may
15315 be represented by a letter or by @dfn{escape sequences}, which are of
15316 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
15317 of the character's ordinal value; or of the form @samp{\@var{x}}, where
15318 @samp{@var{x}} is a predefined special character---for example,
15319 @samp{\n} for newline.
15321 Wide character constants can be written by prefixing a character
15322 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
15323 form of @samp{x}. The target wide character set is used when
15324 computing the value of this constant (@pxref{Character Sets}).
15327 String constants are a sequence of character constants surrounded by
15328 double quotes (@code{"}). Any valid character constant (as described
15329 above) may appear. Double quotes within the string must be preceded by
15330 a backslash, so for instance @samp{"a\"b'c"} is a string of five
15333 Wide string constants can be written by prefixing a string constant
15334 with @samp{L}, as in C. The target wide character set is used when
15335 computing the value of this constant (@pxref{Character Sets}).
15338 Pointer constants are an integral value. You can also write pointers
15339 to constants using the C operator @samp{&}.
15342 Array constants are comma-separated lists surrounded by braces @samp{@{}
15343 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
15344 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
15345 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
15348 @node C Plus Plus Expressions
15349 @subsubsection C@t{++} Expressions
15351 @cindex expressions in C@t{++}
15352 @value{GDBN} expression handling can interpret most C@t{++} expressions.
15354 @cindex debugging C@t{++} programs
15355 @cindex C@t{++} compilers
15356 @cindex debug formats and C@t{++}
15357 @cindex @value{NGCC} and C@t{++}
15359 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
15360 the proper compiler and the proper debug format. Currently,
15361 @value{GDBN} works best when debugging C@t{++} code that is compiled
15362 with the most recent version of @value{NGCC} possible. The DWARF
15363 debugging format is preferred; @value{NGCC} defaults to this on most
15364 popular platforms. Other compilers and/or debug formats are likely to
15365 work badly or not at all when using @value{GDBN} to debug C@t{++}
15366 code. @xref{Compilation}.
15371 @cindex member functions
15373 Member function calls are allowed; you can use expressions like
15376 count = aml->GetOriginal(x, y)
15379 @vindex this@r{, inside C@t{++} member functions}
15380 @cindex namespace in C@t{++}
15382 While a member function is active (in the selected stack frame), your
15383 expressions have the same namespace available as the member function;
15384 that is, @value{GDBN} allows implicit references to the class instance
15385 pointer @code{this} following the same rules as C@t{++}. @code{using}
15386 declarations in the current scope are also respected by @value{GDBN}.
15388 @cindex call overloaded functions
15389 @cindex overloaded functions, calling
15390 @cindex type conversions in C@t{++}
15392 You can call overloaded functions; @value{GDBN} resolves the function
15393 call to the right definition, with some restrictions. @value{GDBN} does not
15394 perform overload resolution involving user-defined type conversions,
15395 calls to constructors, or instantiations of templates that do not exist
15396 in the program. It also cannot handle ellipsis argument lists or
15399 It does perform integral conversions and promotions, floating-point
15400 promotions, arithmetic conversions, pointer conversions, conversions of
15401 class objects to base classes, and standard conversions such as those of
15402 functions or arrays to pointers; it requires an exact match on the
15403 number of function arguments.
15405 Overload resolution is always performed, unless you have specified
15406 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
15407 ,@value{GDBN} Features for C@t{++}}.
15409 You must specify @code{set overload-resolution off} in order to use an
15410 explicit function signature to call an overloaded function, as in
15412 p 'foo(char,int)'('x', 13)
15415 The @value{GDBN} command-completion facility can simplify this;
15416 see @ref{Completion, ,Command Completion}.
15418 @cindex reference declarations
15420 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
15421 references; you can use them in expressions just as you do in C@t{++}
15422 source---they are automatically dereferenced.
15424 In the parameter list shown when @value{GDBN} displays a frame, the values of
15425 reference variables are not displayed (unlike other variables); this
15426 avoids clutter, since references are often used for large structures.
15427 The @emph{address} of a reference variable is always shown, unless
15428 you have specified @samp{set print address off}.
15431 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
15432 expressions can use it just as expressions in your program do. Since
15433 one scope may be defined in another, you can use @code{::} repeatedly if
15434 necessary, for example in an expression like
15435 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
15436 resolving name scope by reference to source files, in both C and C@t{++}
15437 debugging (@pxref{Variables, ,Program Variables}).
15440 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15445 @subsubsection C and C@t{++} Defaults
15447 @cindex C and C@t{++} defaults
15449 If you allow @value{GDBN} to set range checking automatically, it
15450 defaults to @code{off} whenever the working language changes to
15451 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15452 selects the working language.
15454 If you allow @value{GDBN} to set the language automatically, it
15455 recognizes source files whose names end with @file{.c}, @file{.C}, or
15456 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15457 these files, it sets the working language to C or C@t{++}.
15458 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15459 for further details.
15462 @subsubsection C and C@t{++} Type and Range Checks
15464 @cindex C and C@t{++} checks
15466 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15467 checking is used. However, if you turn type checking off, @value{GDBN}
15468 will allow certain non-standard conversions, such as promoting integer
15469 constants to pointers.
15471 Range checking, if turned on, is done on mathematical operations. Array
15472 indices are not checked, since they are often used to index a pointer
15473 that is not itself an array.
15476 @subsubsection @value{GDBN} and C
15478 The @code{set print union} and @code{show print union} commands apply to
15479 the @code{union} type. When set to @samp{on}, any @code{union} that is
15480 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15481 appears as @samp{@{...@}}.
15483 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15484 with pointers and a memory allocation function. @xref{Expressions,
15487 @node Debugging C Plus Plus
15488 @subsubsection @value{GDBN} Features for C@t{++}
15490 @cindex commands for C@t{++}
15492 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15493 designed specifically for use with C@t{++}. Here is a summary:
15496 @cindex break in overloaded functions
15497 @item @r{breakpoint menus}
15498 When you want a breakpoint in a function whose name is overloaded,
15499 @value{GDBN} has the capability to display a menu of possible breakpoint
15500 locations to help you specify which function definition you want.
15501 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15503 @cindex overloading in C@t{++}
15504 @item rbreak @var{regex}
15505 Setting breakpoints using regular expressions is helpful for setting
15506 breakpoints on overloaded functions that are not members of any special
15508 @xref{Set Breaks, ,Setting Breakpoints}.
15510 @cindex C@t{++} exception handling
15512 @itemx catch rethrow
15514 Debug C@t{++} exception handling using these commands. @xref{Set
15515 Catchpoints, , Setting Catchpoints}.
15517 @cindex inheritance
15518 @item ptype @var{typename}
15519 Print inheritance relationships as well as other information for type
15521 @xref{Symbols, ,Examining the Symbol Table}.
15523 @item info vtbl @var{expression}.
15524 The @code{info vtbl} command can be used to display the virtual
15525 method tables of the object computed by @var{expression}. This shows
15526 one entry per virtual table; there may be multiple virtual tables when
15527 multiple inheritance is in use.
15529 @cindex C@t{++} demangling
15530 @item demangle @var{name}
15531 Demangle @var{name}.
15532 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15534 @cindex C@t{++} symbol display
15535 @item set print demangle
15536 @itemx show print demangle
15537 @itemx set print asm-demangle
15538 @itemx show print asm-demangle
15539 Control whether C@t{++} symbols display in their source form, both when
15540 displaying code as C@t{++} source and when displaying disassemblies.
15541 @xref{Print Settings, ,Print Settings}.
15543 @item set print object
15544 @itemx show print object
15545 Choose whether to print derived (actual) or declared types of objects.
15546 @xref{Print Settings, ,Print Settings}.
15548 @item set print vtbl
15549 @itemx show print vtbl
15550 Control the format for printing virtual function tables.
15551 @xref{Print Settings, ,Print Settings}.
15552 (The @code{vtbl} commands do not work on programs compiled with the HP
15553 ANSI C@t{++} compiler (@code{aCC}).)
15555 @kindex set overload-resolution
15556 @cindex overloaded functions, overload resolution
15557 @item set overload-resolution on
15558 Enable overload resolution for C@t{++} expression evaluation. The default
15559 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15560 and searches for a function whose signature matches the argument types,
15561 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15562 Expressions, ,C@t{++} Expressions}, for details).
15563 If it cannot find a match, it emits a message.
15565 @item set overload-resolution off
15566 Disable overload resolution for C@t{++} expression evaluation. For
15567 overloaded functions that are not class member functions, @value{GDBN}
15568 chooses the first function of the specified name that it finds in the
15569 symbol table, whether or not its arguments are of the correct type. For
15570 overloaded functions that are class member functions, @value{GDBN}
15571 searches for a function whose signature @emph{exactly} matches the
15574 @kindex show overload-resolution
15575 @item show overload-resolution
15576 Show the current setting of overload resolution.
15578 @item @r{Overloaded symbol names}
15579 You can specify a particular definition of an overloaded symbol, using
15580 the same notation that is used to declare such symbols in C@t{++}: type
15581 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15582 also use the @value{GDBN} command-line word completion facilities to list the
15583 available choices, or to finish the type list for you.
15584 @xref{Completion,, Command Completion}, for details on how to do this.
15586 @item @r{Breakpoints in functions with ABI tags}
15588 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15589 correspond to changes in the ABI of a type, function, or variable that
15590 would not otherwise be reflected in a mangled name. See
15591 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15594 The ABI tags are visible in C@t{++} demangled names. For example, a
15595 function that returns a std::string:
15598 std::string function(int);
15602 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15603 tag, and @value{GDBN} displays the symbol like this:
15606 function[abi:cxx11](int)
15609 You can set a breakpoint on such functions simply as if they had no
15613 (gdb) b function(int)
15614 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15615 (gdb) info breakpoints
15616 Num Type Disp Enb Address What
15617 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15621 On the rare occasion you need to disambiguate between different ABI
15622 tags, you can do so by simply including the ABI tag in the function
15626 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15630 @node Decimal Floating Point
15631 @subsubsection Decimal Floating Point format
15632 @cindex decimal floating point format
15634 @value{GDBN} can examine, set and perform computations with numbers in
15635 decimal floating point format, which in the C language correspond to the
15636 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15637 specified by the extension to support decimal floating-point arithmetic.
15639 There are two encodings in use, depending on the architecture: BID (Binary
15640 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15641 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15644 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15645 to manipulate decimal floating point numbers, it is not possible to convert
15646 (using a cast, for example) integers wider than 32-bit to decimal float.
15648 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15649 point computations, error checking in decimal float operations ignores
15650 underflow, overflow and divide by zero exceptions.
15652 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15653 to inspect @code{_Decimal128} values stored in floating point registers.
15654 See @ref{PowerPC,,PowerPC} for more details.
15660 @value{GDBN} can be used to debug programs written in D and compiled with
15661 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15662 specific feature --- dynamic arrays.
15667 @cindex Go (programming language)
15668 @value{GDBN} can be used to debug programs written in Go and compiled with
15669 @file{gccgo} or @file{6g} compilers.
15671 Here is a summary of the Go-specific features and restrictions:
15674 @cindex current Go package
15675 @item The current Go package
15676 The name of the current package does not need to be specified when
15677 specifying global variables and functions.
15679 For example, given the program:
15683 var myglob = "Shall we?"
15689 When stopped inside @code{main} either of these work:
15693 (gdb) p main.myglob
15696 @cindex builtin Go types
15697 @item Builtin Go types
15698 The @code{string} type is recognized by @value{GDBN} and is printed
15701 @cindex builtin Go functions
15702 @item Builtin Go functions
15703 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15704 function and handles it internally.
15706 @cindex restrictions on Go expressions
15707 @item Restrictions on Go expressions
15708 All Go operators are supported except @code{&^}.
15709 The Go @code{_} ``blank identifier'' is not supported.
15710 Automatic dereferencing of pointers is not supported.
15714 @subsection Objective-C
15716 @cindex Objective-C
15717 This section provides information about some commands and command
15718 options that are useful for debugging Objective-C code. See also
15719 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15720 few more commands specific to Objective-C support.
15723 * Method Names in Commands::
15724 * The Print Command with Objective-C::
15727 @node Method Names in Commands
15728 @subsubsection Method Names in Commands
15730 The following commands have been extended to accept Objective-C method
15731 names as line specifications:
15733 @kindex clear@r{, and Objective-C}
15734 @kindex break@r{, and Objective-C}
15735 @kindex info line@r{, and Objective-C}
15736 @kindex jump@r{, and Objective-C}
15737 @kindex list@r{, and Objective-C}
15741 @item @code{info line}
15746 A fully qualified Objective-C method name is specified as
15749 -[@var{Class} @var{methodName}]
15752 where the minus sign is used to indicate an instance method and a
15753 plus sign (not shown) is used to indicate a class method. The class
15754 name @var{Class} and method name @var{methodName} are enclosed in
15755 brackets, similar to the way messages are specified in Objective-C
15756 source code. For example, to set a breakpoint at the @code{create}
15757 instance method of class @code{Fruit} in the program currently being
15761 break -[Fruit create]
15764 To list ten program lines around the @code{initialize} class method,
15768 list +[NSText initialize]
15771 In the current version of @value{GDBN}, the plus or minus sign is
15772 required. In future versions of @value{GDBN}, the plus or minus
15773 sign will be optional, but you can use it to narrow the search. It
15774 is also possible to specify just a method name:
15780 You must specify the complete method name, including any colons. If
15781 your program's source files contain more than one @code{create} method,
15782 you'll be presented with a numbered list of classes that implement that
15783 method. Indicate your choice by number, or type @samp{0} to exit if
15786 As another example, to clear a breakpoint established at the
15787 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15790 clear -[NSWindow makeKeyAndOrderFront:]
15793 @node The Print Command with Objective-C
15794 @subsubsection The Print Command With Objective-C
15795 @cindex Objective-C, print objects
15796 @kindex print-object
15797 @kindex po @r{(@code{print-object})}
15799 The print command has also been extended to accept methods. For example:
15802 print -[@var{object} hash]
15805 @cindex print an Objective-C object description
15806 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15808 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15809 and print the result. Also, an additional command has been added,
15810 @code{print-object} or @code{po} for short, which is meant to print
15811 the description of an object. However, this command may only work
15812 with certain Objective-C libraries that have a particular hook
15813 function, @code{_NSPrintForDebugger}, defined.
15816 @subsection OpenCL C
15819 This section provides information about @value{GDBN}s OpenCL C support.
15822 * OpenCL C Datatypes::
15823 * OpenCL C Expressions::
15824 * OpenCL C Operators::
15827 @node OpenCL C Datatypes
15828 @subsubsection OpenCL C Datatypes
15830 @cindex OpenCL C Datatypes
15831 @value{GDBN} supports the builtin scalar and vector datatypes specified
15832 by OpenCL 1.1. In addition the half- and double-precision floating point
15833 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15834 extensions are also known to @value{GDBN}.
15836 @node OpenCL C Expressions
15837 @subsubsection OpenCL C Expressions
15839 @cindex OpenCL C Expressions
15840 @value{GDBN} supports accesses to vector components including the access as
15841 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15842 supported by @value{GDBN} can be used as well.
15844 @node OpenCL C Operators
15845 @subsubsection OpenCL C Operators
15847 @cindex OpenCL C Operators
15848 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15852 @subsection Fortran
15853 @cindex Fortran-specific support in @value{GDBN}
15855 @value{GDBN} can be used to debug programs written in Fortran, but it
15856 currently supports only the features of Fortran 77 language.
15858 @cindex trailing underscore, in Fortran symbols
15859 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15860 among them) append an underscore to the names of variables and
15861 functions. When you debug programs compiled by those compilers, you
15862 will need to refer to variables and functions with a trailing
15866 * Fortran Operators:: Fortran operators and expressions
15867 * Fortran Defaults:: Default settings for Fortran
15868 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15871 @node Fortran Operators
15872 @subsubsection Fortran Operators and Expressions
15874 @cindex Fortran operators and expressions
15876 Operators must be defined on values of specific types. For instance,
15877 @code{+} is defined on numbers, but not on characters or other non-
15878 arithmetic types. Operators are often defined on groups of types.
15882 The exponentiation operator. It raises the first operand to the power
15886 The range operator. Normally used in the form of array(low:high) to
15887 represent a section of array.
15890 The access component operator. Normally used to access elements in derived
15891 types. Also suitable for unions. As unions aren't part of regular Fortran,
15892 this can only happen when accessing a register that uses a gdbarch-defined
15896 @node Fortran Defaults
15897 @subsubsection Fortran Defaults
15899 @cindex Fortran Defaults
15901 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15902 default uses case-insensitive matches for Fortran symbols. You can
15903 change that with the @samp{set case-insensitive} command, see
15904 @ref{Symbols}, for the details.
15906 @node Special Fortran Commands
15907 @subsubsection Special Fortran Commands
15909 @cindex Special Fortran commands
15911 @value{GDBN} has some commands to support Fortran-specific features,
15912 such as displaying common blocks.
15915 @cindex @code{COMMON} blocks, Fortran
15916 @kindex info common
15917 @item info common @r{[}@var{common-name}@r{]}
15918 This command prints the values contained in the Fortran @code{COMMON}
15919 block whose name is @var{common-name}. With no argument, the names of
15920 all @code{COMMON} blocks visible at the current program location are
15927 @cindex Pascal support in @value{GDBN}, limitations
15928 Debugging Pascal programs which use sets, subranges, file variables, or
15929 nested functions does not currently work. @value{GDBN} does not support
15930 entering expressions, printing values, or similar features using Pascal
15933 The Pascal-specific command @code{set print pascal_static-members}
15934 controls whether static members of Pascal objects are displayed.
15935 @xref{Print Settings, pascal_static-members}.
15940 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15941 Programming Language}. Type- and value-printing, and expression
15942 parsing, are reasonably complete. However, there are a few
15943 peculiarities and holes to be aware of.
15947 Linespecs (@pxref{Specify Location}) are never relative to the current
15948 crate. Instead, they act as if there were a global namespace of
15949 crates, somewhat similar to the way @code{extern crate} behaves.
15951 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15952 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15953 to set a breakpoint in a function named @samp{f} in a crate named
15956 As a consequence of this approach, linespecs also cannot refer to
15957 items using @samp{self::} or @samp{super::}.
15960 Because @value{GDBN} implements Rust name-lookup semantics in
15961 expressions, it will sometimes prepend the current crate to a name.
15962 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15963 @samp{K}, then @code{print ::x::y} will try to find the symbol
15966 However, since it is useful to be able to refer to other crates when
15967 debugging, @value{GDBN} provides the @code{extern} extension to
15968 circumvent this. To use the extension, just put @code{extern} before
15969 a path expression to refer to the otherwise unavailable ``global''
15972 In the above example, if you wanted to refer to the symbol @samp{y} in
15973 the crate @samp{x}, you would use @code{print extern x::y}.
15976 The Rust expression evaluator does not support ``statement-like''
15977 expressions such as @code{if} or @code{match}, or lambda expressions.
15980 Tuple expressions are not implemented.
15983 The Rust expression evaluator does not currently implement the
15984 @code{Drop} trait. Objects that may be created by the evaluator will
15985 never be destroyed.
15988 @value{GDBN} does not implement type inference for generics. In order
15989 to call generic functions or otherwise refer to generic items, you
15990 will have to specify the type parameters manually.
15993 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15994 cases this does not cause any problems. However, in an expression
15995 context, completing a generic function name will give syntactically
15996 invalid results. This happens because Rust requires the @samp{::}
15997 operator between the function name and its generic arguments. For
15998 example, @value{GDBN} might provide a completion like
15999 @code{crate::f<u32>}, where the parser would require
16000 @code{crate::f::<u32>}.
16003 As of this writing, the Rust compiler (version 1.8) has a few holes in
16004 the debugging information it generates. These holes prevent certain
16005 features from being implemented by @value{GDBN}:
16009 Method calls cannot be made via traits.
16012 Operator overloading is not implemented.
16015 When debugging in a monomorphized function, you cannot use the generic
16019 The type @code{Self} is not available.
16022 @code{use} statements are not available, so some names may not be
16023 available in the crate.
16028 @subsection Modula-2
16030 @cindex Modula-2, @value{GDBN} support
16032 The extensions made to @value{GDBN} to support Modula-2 only support
16033 output from the @sc{gnu} Modula-2 compiler (which is currently being
16034 developed). Other Modula-2 compilers are not currently supported, and
16035 attempting to debug executables produced by them is most likely
16036 to give an error as @value{GDBN} reads in the executable's symbol
16039 @cindex expressions in Modula-2
16041 * M2 Operators:: Built-in operators
16042 * Built-In Func/Proc:: Built-in functions and procedures
16043 * M2 Constants:: Modula-2 constants
16044 * M2 Types:: Modula-2 types
16045 * M2 Defaults:: Default settings for Modula-2
16046 * Deviations:: Deviations from standard Modula-2
16047 * M2 Checks:: Modula-2 type and range checks
16048 * M2 Scope:: The scope operators @code{::} and @code{.}
16049 * GDB/M2:: @value{GDBN} and Modula-2
16053 @subsubsection Operators
16054 @cindex Modula-2 operators
16056 Operators must be defined on values of specific types. For instance,
16057 @code{+} is defined on numbers, but not on structures. Operators are
16058 often defined on groups of types. For the purposes of Modula-2, the
16059 following definitions hold:
16064 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
16068 @emph{Character types} consist of @code{CHAR} and its subranges.
16071 @emph{Floating-point types} consist of @code{REAL}.
16074 @emph{Pointer types} consist of anything declared as @code{POINTER TO
16078 @emph{Scalar types} consist of all of the above.
16081 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
16084 @emph{Boolean types} consist of @code{BOOLEAN}.
16088 The following operators are supported, and appear in order of
16089 increasing precedence:
16093 Function argument or array index separator.
16096 Assignment. The value of @var{var} @code{:=} @var{value} is
16100 Less than, greater than on integral, floating-point, or enumerated
16104 Less than or equal to, greater than or equal to
16105 on integral, floating-point and enumerated types, or set inclusion on
16106 set types. Same precedence as @code{<}.
16108 @item =@r{, }<>@r{, }#
16109 Equality and two ways of expressing inequality, valid on scalar types.
16110 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
16111 available for inequality, since @code{#} conflicts with the script
16115 Set membership. Defined on set types and the types of their members.
16116 Same precedence as @code{<}.
16119 Boolean disjunction. Defined on boolean types.
16122 Boolean conjunction. Defined on boolean types.
16125 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16128 Addition and subtraction on integral and floating-point types, or union
16129 and difference on set types.
16132 Multiplication on integral and floating-point types, or set intersection
16136 Division on floating-point types, or symmetric set difference on set
16137 types. Same precedence as @code{*}.
16140 Integer division and remainder. Defined on integral types. Same
16141 precedence as @code{*}.
16144 Negative. Defined on @code{INTEGER} and @code{REAL} data.
16147 Pointer dereferencing. Defined on pointer types.
16150 Boolean negation. Defined on boolean types. Same precedence as
16154 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
16155 precedence as @code{^}.
16158 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
16161 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
16165 @value{GDBN} and Modula-2 scope operators.
16169 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
16170 treats the use of the operator @code{IN}, or the use of operators
16171 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
16172 @code{<=}, and @code{>=} on sets as an error.
16176 @node Built-In Func/Proc
16177 @subsubsection Built-in Functions and Procedures
16178 @cindex Modula-2 built-ins
16180 Modula-2 also makes available several built-in procedures and functions.
16181 In describing these, the following metavariables are used:
16186 represents an @code{ARRAY} variable.
16189 represents a @code{CHAR} constant or variable.
16192 represents a variable or constant of integral type.
16195 represents an identifier that belongs to a set. Generally used in the
16196 same function with the metavariable @var{s}. The type of @var{s} should
16197 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
16200 represents a variable or constant of integral or floating-point type.
16203 represents a variable or constant of floating-point type.
16209 represents a variable.
16212 represents a variable or constant of one of many types. See the
16213 explanation of the function for details.
16216 All Modula-2 built-in procedures also return a result, described below.
16220 Returns the absolute value of @var{n}.
16223 If @var{c} is a lower case letter, it returns its upper case
16224 equivalent, otherwise it returns its argument.
16227 Returns the character whose ordinal value is @var{i}.
16230 Decrements the value in the variable @var{v} by one. Returns the new value.
16232 @item DEC(@var{v},@var{i})
16233 Decrements the value in the variable @var{v} by @var{i}. Returns the
16236 @item EXCL(@var{m},@var{s})
16237 Removes the element @var{m} from the set @var{s}. Returns the new
16240 @item FLOAT(@var{i})
16241 Returns the floating point equivalent of the integer @var{i}.
16243 @item HIGH(@var{a})
16244 Returns the index of the last member of @var{a}.
16247 Increments the value in the variable @var{v} by one. Returns the new value.
16249 @item INC(@var{v},@var{i})
16250 Increments the value in the variable @var{v} by @var{i}. Returns the
16253 @item INCL(@var{m},@var{s})
16254 Adds the element @var{m} to the set @var{s} if it is not already
16255 there. Returns the new set.
16258 Returns the maximum value of the type @var{t}.
16261 Returns the minimum value of the type @var{t}.
16264 Returns boolean TRUE if @var{i} is an odd number.
16267 Returns the ordinal value of its argument. For example, the ordinal
16268 value of a character is its @sc{ascii} value (on machines supporting
16269 the @sc{ascii} character set). The argument @var{x} must be of an
16270 ordered type, which include integral, character and enumerated types.
16272 @item SIZE(@var{x})
16273 Returns the size of its argument. The argument @var{x} can be a
16274 variable or a type.
16276 @item TRUNC(@var{r})
16277 Returns the integral part of @var{r}.
16279 @item TSIZE(@var{x})
16280 Returns the size of its argument. The argument @var{x} can be a
16281 variable or a type.
16283 @item VAL(@var{t},@var{i})
16284 Returns the member of the type @var{t} whose ordinal value is @var{i}.
16288 @emph{Warning:} Sets and their operations are not yet supported, so
16289 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
16293 @cindex Modula-2 constants
16295 @subsubsection Constants
16297 @value{GDBN} allows you to express the constants of Modula-2 in the following
16303 Integer constants are simply a sequence of digits. When used in an
16304 expression, a constant is interpreted to be type-compatible with the
16305 rest of the expression. Hexadecimal integers are specified by a
16306 trailing @samp{H}, and octal integers by a trailing @samp{B}.
16309 Floating point constants appear as a sequence of digits, followed by a
16310 decimal point and another sequence of digits. An optional exponent can
16311 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
16312 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
16313 digits of the floating point constant must be valid decimal (base 10)
16317 Character constants consist of a single character enclosed by a pair of
16318 like quotes, either single (@code{'}) or double (@code{"}). They may
16319 also be expressed by their ordinal value (their @sc{ascii} value, usually)
16320 followed by a @samp{C}.
16323 String constants consist of a sequence of characters enclosed by a
16324 pair of like quotes, either single (@code{'}) or double (@code{"}).
16325 Escape sequences in the style of C are also allowed. @xref{C
16326 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
16330 Enumerated constants consist of an enumerated identifier.
16333 Boolean constants consist of the identifiers @code{TRUE} and
16337 Pointer constants consist of integral values only.
16340 Set constants are not yet supported.
16344 @subsubsection Modula-2 Types
16345 @cindex Modula-2 types
16347 Currently @value{GDBN} can print the following data types in Modula-2
16348 syntax: array types, record types, set types, pointer types, procedure
16349 types, enumerated types, subrange types and base types. You can also
16350 print the contents of variables declared using these type.
16351 This section gives a number of simple source code examples together with
16352 sample @value{GDBN} sessions.
16354 The first example contains the following section of code:
16363 and you can request @value{GDBN} to interrogate the type and value of
16364 @code{r} and @code{s}.
16367 (@value{GDBP}) print s
16369 (@value{GDBP}) ptype s
16371 (@value{GDBP}) print r
16373 (@value{GDBP}) ptype r
16378 Likewise if your source code declares @code{s} as:
16382 s: SET ['A'..'Z'] ;
16386 then you may query the type of @code{s} by:
16389 (@value{GDBP}) ptype s
16390 type = SET ['A'..'Z']
16394 Note that at present you cannot interactively manipulate set
16395 expressions using the debugger.
16397 The following example shows how you might declare an array in Modula-2
16398 and how you can interact with @value{GDBN} to print its type and contents:
16402 s: ARRAY [-10..10] OF CHAR ;
16406 (@value{GDBP}) ptype s
16407 ARRAY [-10..10] OF CHAR
16410 Note that the array handling is not yet complete and although the type
16411 is printed correctly, expression handling still assumes that all
16412 arrays have a lower bound of zero and not @code{-10} as in the example
16415 Here are some more type related Modula-2 examples:
16419 colour = (blue, red, yellow, green) ;
16420 t = [blue..yellow] ;
16428 The @value{GDBN} interaction shows how you can query the data type
16429 and value of a variable.
16432 (@value{GDBP}) print s
16434 (@value{GDBP}) ptype t
16435 type = [blue..yellow]
16439 In this example a Modula-2 array is declared and its contents
16440 displayed. Observe that the contents are written in the same way as
16441 their @code{C} counterparts.
16445 s: ARRAY [1..5] OF CARDINAL ;
16451 (@value{GDBP}) print s
16452 $1 = @{1, 0, 0, 0, 0@}
16453 (@value{GDBP}) ptype s
16454 type = ARRAY [1..5] OF CARDINAL
16457 The Modula-2 language interface to @value{GDBN} also understands
16458 pointer types as shown in this example:
16462 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16469 and you can request that @value{GDBN} describes the type of @code{s}.
16472 (@value{GDBP}) ptype s
16473 type = POINTER TO ARRAY [1..5] OF CARDINAL
16476 @value{GDBN} handles compound types as we can see in this example.
16477 Here we combine array types, record types, pointer types and subrange
16488 myarray = ARRAY myrange OF CARDINAL ;
16489 myrange = [-2..2] ;
16491 s: POINTER TO ARRAY myrange OF foo ;
16495 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16499 (@value{GDBP}) ptype s
16500 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16503 f3 : ARRAY [-2..2] OF CARDINAL;
16508 @subsubsection Modula-2 Defaults
16509 @cindex Modula-2 defaults
16511 If type and range checking are set automatically by @value{GDBN}, they
16512 both default to @code{on} whenever the working language changes to
16513 Modula-2. This happens regardless of whether you or @value{GDBN}
16514 selected the working language.
16516 If you allow @value{GDBN} to set the language automatically, then entering
16517 code compiled from a file whose name ends with @file{.mod} sets the
16518 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16519 Infer the Source Language}, for further details.
16522 @subsubsection Deviations from Standard Modula-2
16523 @cindex Modula-2, deviations from
16525 A few changes have been made to make Modula-2 programs easier to debug.
16526 This is done primarily via loosening its type strictness:
16530 Unlike in standard Modula-2, pointer constants can be formed by
16531 integers. This allows you to modify pointer variables during
16532 debugging. (In standard Modula-2, the actual address contained in a
16533 pointer variable is hidden from you; it can only be modified
16534 through direct assignment to another pointer variable or expression that
16535 returned a pointer.)
16538 C escape sequences can be used in strings and characters to represent
16539 non-printable characters. @value{GDBN} prints out strings with these
16540 escape sequences embedded. Single non-printable characters are
16541 printed using the @samp{CHR(@var{nnn})} format.
16544 The assignment operator (@code{:=}) returns the value of its right-hand
16548 All built-in procedures both modify @emph{and} return their argument.
16552 @subsubsection Modula-2 Type and Range Checks
16553 @cindex Modula-2 checks
16556 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16559 @c FIXME remove warning when type/range checks added
16561 @value{GDBN} considers two Modula-2 variables type equivalent if:
16565 They are of types that have been declared equivalent via a @code{TYPE
16566 @var{t1} = @var{t2}} statement
16569 They have been declared on the same line. (Note: This is true of the
16570 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16573 As long as type checking is enabled, any attempt to combine variables
16574 whose types are not equivalent is an error.
16576 Range checking is done on all mathematical operations, assignment, array
16577 index bounds, and all built-in functions and procedures.
16580 @subsubsection The Scope Operators @code{::} and @code{.}
16582 @cindex @code{.}, Modula-2 scope operator
16583 @cindex colon, doubled as scope operator
16585 @vindex colon-colon@r{, in Modula-2}
16586 @c Info cannot handle :: but TeX can.
16589 @vindex ::@r{, in Modula-2}
16592 There are a few subtle differences between the Modula-2 scope operator
16593 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16598 @var{module} . @var{id}
16599 @var{scope} :: @var{id}
16603 where @var{scope} is the name of a module or a procedure,
16604 @var{module} the name of a module, and @var{id} is any declared
16605 identifier within your program, except another module.
16607 Using the @code{::} operator makes @value{GDBN} search the scope
16608 specified by @var{scope} for the identifier @var{id}. If it is not
16609 found in the specified scope, then @value{GDBN} searches all scopes
16610 enclosing the one specified by @var{scope}.
16612 Using the @code{.} operator makes @value{GDBN} search the current scope for
16613 the identifier specified by @var{id} that was imported from the
16614 definition module specified by @var{module}. With this operator, it is
16615 an error if the identifier @var{id} was not imported from definition
16616 module @var{module}, or if @var{id} is not an identifier in
16620 @subsubsection @value{GDBN} and Modula-2
16622 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16623 Five subcommands of @code{set print} and @code{show print} apply
16624 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16625 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16626 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16627 analogue in Modula-2.
16629 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16630 with any language, is not useful with Modula-2. Its
16631 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16632 created in Modula-2 as they can in C or C@t{++}. However, because an
16633 address can be specified by an integral constant, the construct
16634 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16636 @cindex @code{#} in Modula-2
16637 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16638 interpreted as the beginning of a comment. Use @code{<>} instead.
16644 The extensions made to @value{GDBN} for Ada only support
16645 output from the @sc{gnu} Ada (GNAT) compiler.
16646 Other Ada compilers are not currently supported, and
16647 attempting to debug executables produced by them is most likely
16651 @cindex expressions in Ada
16653 * Ada Mode Intro:: General remarks on the Ada syntax
16654 and semantics supported by Ada mode
16656 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16657 * Additions to Ada:: Extensions of the Ada expression syntax.
16658 * Overloading support for Ada:: Support for expressions involving overloaded
16660 * Stopping Before Main Program:: Debugging the program during elaboration.
16661 * Ada Exceptions:: Ada Exceptions
16662 * Ada Tasks:: Listing and setting breakpoints in tasks.
16663 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16664 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16666 * Ada Settings:: New settable GDB parameters for Ada.
16667 * Ada Glitches:: Known peculiarities of Ada mode.
16670 @node Ada Mode Intro
16671 @subsubsection Introduction
16672 @cindex Ada mode, general
16674 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16675 syntax, with some extensions.
16676 The philosophy behind the design of this subset is
16680 That @value{GDBN} should provide basic literals and access to operations for
16681 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16682 leaving more sophisticated computations to subprograms written into the
16683 program (which therefore may be called from @value{GDBN}).
16686 That type safety and strict adherence to Ada language restrictions
16687 are not particularly important to the @value{GDBN} user.
16690 That brevity is important to the @value{GDBN} user.
16693 Thus, for brevity, the debugger acts as if all names declared in
16694 user-written packages are directly visible, even if they are not visible
16695 according to Ada rules, thus making it unnecessary to fully qualify most
16696 names with their packages, regardless of context. Where this causes
16697 ambiguity, @value{GDBN} asks the user's intent.
16699 The debugger will start in Ada mode if it detects an Ada main program.
16700 As for other languages, it will enter Ada mode when stopped in a program that
16701 was translated from an Ada source file.
16703 While in Ada mode, you may use `@t{--}' for comments. This is useful
16704 mostly for documenting command files. The standard @value{GDBN} comment
16705 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16706 middle (to allow based literals).
16708 @node Omissions from Ada
16709 @subsubsection Omissions from Ada
16710 @cindex Ada, omissions from
16712 Here are the notable omissions from the subset:
16716 Only a subset of the attributes are supported:
16720 @t{'First}, @t{'Last}, and @t{'Length}
16721 on array objects (not on types and subtypes).
16724 @t{'Min} and @t{'Max}.
16727 @t{'Pos} and @t{'Val}.
16733 @t{'Range} on array objects (not subtypes), but only as the right
16734 operand of the membership (@code{in}) operator.
16737 @t{'Access}, @t{'Unchecked_Access}, and
16738 @t{'Unrestricted_Access} (a GNAT extension).
16746 @code{Characters.Latin_1} are not available and
16747 concatenation is not implemented. Thus, escape characters in strings are
16748 not currently available.
16751 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16752 equality of representations. They will generally work correctly
16753 for strings and arrays whose elements have integer or enumeration types.
16754 They may not work correctly for arrays whose element
16755 types have user-defined equality, for arrays of real values
16756 (in particular, IEEE-conformant floating point, because of negative
16757 zeroes and NaNs), and for arrays whose elements contain unused bits with
16758 indeterminate values.
16761 The other component-by-component array operations (@code{and}, @code{or},
16762 @code{xor}, @code{not}, and relational tests other than equality)
16763 are not implemented.
16766 @cindex array aggregates (Ada)
16767 @cindex record aggregates (Ada)
16768 @cindex aggregates (Ada)
16769 There is limited support for array and record aggregates. They are
16770 permitted only on the right sides of assignments, as in these examples:
16773 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16774 (@value{GDBP}) set An_Array := (1, others => 0)
16775 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16776 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16777 (@value{GDBP}) set A_Record := (1, "Peter", True);
16778 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16782 discriminant's value by assigning an aggregate has an
16783 undefined effect if that discriminant is used within the record.
16784 However, you can first modify discriminants by directly assigning to
16785 them (which normally would not be allowed in Ada), and then performing an
16786 aggregate assignment. For example, given a variable @code{A_Rec}
16787 declared to have a type such as:
16790 type Rec (Len : Small_Integer := 0) is record
16792 Vals : IntArray (1 .. Len);
16796 you can assign a value with a different size of @code{Vals} with two
16800 (@value{GDBP}) set A_Rec.Len := 4
16801 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16804 As this example also illustrates, @value{GDBN} is very loose about the usual
16805 rules concerning aggregates. You may leave out some of the
16806 components of an array or record aggregate (such as the @code{Len}
16807 component in the assignment to @code{A_Rec} above); they will retain their
16808 original values upon assignment. You may freely use dynamic values as
16809 indices in component associations. You may even use overlapping or
16810 redundant component associations, although which component values are
16811 assigned in such cases is not defined.
16814 Calls to dispatching subprograms are not implemented.
16817 The overloading algorithm is much more limited (i.e., less selective)
16818 than that of real Ada. It makes only limited use of the context in
16819 which a subexpression appears to resolve its meaning, and it is much
16820 looser in its rules for allowing type matches. As a result, some
16821 function calls will be ambiguous, and the user will be asked to choose
16822 the proper resolution.
16825 The @code{new} operator is not implemented.
16828 Entry calls are not implemented.
16831 Aside from printing, arithmetic operations on the native VAX floating-point
16832 formats are not supported.
16835 It is not possible to slice a packed array.
16838 The names @code{True} and @code{False}, when not part of a qualified name,
16839 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16841 Should your program
16842 redefine these names in a package or procedure (at best a dubious practice),
16843 you will have to use fully qualified names to access their new definitions.
16846 @node Additions to Ada
16847 @subsubsection Additions to Ada
16848 @cindex Ada, deviations from
16850 As it does for other languages, @value{GDBN} makes certain generic
16851 extensions to Ada (@pxref{Expressions}):
16855 If the expression @var{E} is a variable residing in memory (typically
16856 a local variable or array element) and @var{N} is a positive integer,
16857 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16858 @var{N}-1 adjacent variables following it in memory as an array. In
16859 Ada, this operator is generally not necessary, since its prime use is
16860 in displaying parts of an array, and slicing will usually do this in
16861 Ada. However, there are occasional uses when debugging programs in
16862 which certain debugging information has been optimized away.
16865 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16866 appears in function or file @var{B}.'' When @var{B} is a file name,
16867 you must typically surround it in single quotes.
16870 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16871 @var{type} that appears at address @var{addr}.''
16874 A name starting with @samp{$} is a convenience variable
16875 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16878 In addition, @value{GDBN} provides a few other shortcuts and outright
16879 additions specific to Ada:
16883 The assignment statement is allowed as an expression, returning
16884 its right-hand operand as its value. Thus, you may enter
16887 (@value{GDBP}) set x := y + 3
16888 (@value{GDBP}) print A(tmp := y + 1)
16892 The semicolon is allowed as an ``operator,'' returning as its value
16893 the value of its right-hand operand.
16894 This allows, for example,
16895 complex conditional breaks:
16898 (@value{GDBP}) break f
16899 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16903 Rather than use catenation and symbolic character names to introduce special
16904 characters into strings, one may instead use a special bracket notation,
16905 which is also used to print strings. A sequence of characters of the form
16906 @samp{["@var{XX}"]} within a string or character literal denotes the
16907 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16908 sequence of characters @samp{["""]} also denotes a single quotation mark
16909 in strings. For example,
16911 "One line.["0a"]Next line.["0a"]"
16914 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16918 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16919 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16923 (@value{GDBP}) print 'max(x, y)
16927 When printing arrays, @value{GDBN} uses positional notation when the
16928 array has a lower bound of 1, and uses a modified named notation otherwise.
16929 For example, a one-dimensional array of three integers with a lower bound
16930 of 3 might print as
16937 That is, in contrast to valid Ada, only the first component has a @code{=>}
16941 You may abbreviate attributes in expressions with any unique,
16942 multi-character subsequence of
16943 their names (an exact match gets preference).
16944 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16945 in place of @t{a'length}.
16948 @cindex quoting Ada internal identifiers
16949 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16950 to lower case. The GNAT compiler uses upper-case characters for
16951 some of its internal identifiers, which are normally of no interest to users.
16952 For the rare occasions when you actually have to look at them,
16953 enclose them in angle brackets to avoid the lower-case mapping.
16956 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16960 Printing an object of class-wide type or dereferencing an
16961 access-to-class-wide value will display all the components of the object's
16962 specific type (as indicated by its run-time tag). Likewise, component
16963 selection on such a value will operate on the specific type of the
16968 @node Overloading support for Ada
16969 @subsubsection Overloading support for Ada
16970 @cindex overloading, Ada
16972 The debugger supports limited overloading. Given a subprogram call in which
16973 the function symbol has multiple definitions, it will use the number of
16974 actual parameters and some information about their types to attempt to narrow
16975 the set of definitions. It also makes very limited use of context, preferring
16976 procedures to functions in the context of the @code{call} command, and
16977 functions to procedures elsewhere.
16979 If, after narrowing, the set of matching definitions still contains more than
16980 one definition, @value{GDBN} will display a menu to query which one it should
16984 (@value{GDBP}) print f(1)
16985 Multiple matches for f
16987 [1] foo.f (integer) return boolean at foo.adb:23
16988 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16992 In this case, just select one menu entry either to cancel expression evaluation
16993 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16994 instance (type the corresponding number and press @key{RET}).
16996 Here are a couple of commands to customize @value{GDBN}'s behavior in this
17001 @kindex set ada print-signatures
17002 @item set ada print-signatures
17003 Control whether parameter types and return types are displayed in overloads
17004 selection menus. It is @code{on} by default.
17005 @xref{Overloading support for Ada}.
17007 @kindex show ada print-signatures
17008 @item show ada print-signatures
17009 Show the current setting for displaying parameter types and return types in
17010 overloads selection menu.
17011 @xref{Overloading support for Ada}.
17015 @node Stopping Before Main Program
17016 @subsubsection Stopping at the Very Beginning
17018 @cindex breakpointing Ada elaboration code
17019 It is sometimes necessary to debug the program during elaboration, and
17020 before reaching the main procedure.
17021 As defined in the Ada Reference
17022 Manual, the elaboration code is invoked from a procedure called
17023 @code{adainit}. To run your program up to the beginning of
17024 elaboration, simply use the following two commands:
17025 @code{tbreak adainit} and @code{run}.
17027 @node Ada Exceptions
17028 @subsubsection Ada Exceptions
17030 A command is provided to list all Ada exceptions:
17033 @kindex info exceptions
17034 @item info exceptions
17035 @itemx info exceptions @var{regexp}
17036 The @code{info exceptions} command allows you to list all Ada exceptions
17037 defined within the program being debugged, as well as their addresses.
17038 With a regular expression, @var{regexp}, as argument, only those exceptions
17039 whose names match @var{regexp} are listed.
17042 Below is a small example, showing how the command can be used, first
17043 without argument, and next with a regular expression passed as an
17047 (@value{GDBP}) info exceptions
17048 All defined Ada exceptions:
17049 constraint_error: 0x613da0
17050 program_error: 0x613d20
17051 storage_error: 0x613ce0
17052 tasking_error: 0x613ca0
17053 const.aint_global_e: 0x613b00
17054 (@value{GDBP}) info exceptions const.aint
17055 All Ada exceptions matching regular expression "const.aint":
17056 constraint_error: 0x613da0
17057 const.aint_global_e: 0x613b00
17060 It is also possible to ask @value{GDBN} to stop your program's execution
17061 when an exception is raised. For more details, see @ref{Set Catchpoints}.
17064 @subsubsection Extensions for Ada Tasks
17065 @cindex Ada, tasking
17067 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
17068 @value{GDBN} provides the following task-related commands:
17073 This command shows a list of current Ada tasks, as in the following example:
17080 (@value{GDBP}) info tasks
17081 ID TID P-ID Pri State Name
17082 1 8088000 0 15 Child Activation Wait main_task
17083 2 80a4000 1 15 Accept Statement b
17084 3 809a800 1 15 Child Activation Wait a
17085 * 4 80ae800 3 15 Runnable c
17090 In this listing, the asterisk before the last task indicates it to be the
17091 task currently being inspected.
17095 Represents @value{GDBN}'s internal task number.
17101 The parent's task ID (@value{GDBN}'s internal task number).
17104 The base priority of the task.
17107 Current state of the task.
17111 The task has been created but has not been activated. It cannot be
17115 The task is not blocked for any reason known to Ada. (It may be waiting
17116 for a mutex, though.) It is conceptually "executing" in normal mode.
17119 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
17120 that were waiting on terminate alternatives have been awakened and have
17121 terminated themselves.
17123 @item Child Activation Wait
17124 The task is waiting for created tasks to complete activation.
17126 @item Accept Statement
17127 The task is waiting on an accept or selective wait statement.
17129 @item Waiting on entry call
17130 The task is waiting on an entry call.
17132 @item Async Select Wait
17133 The task is waiting to start the abortable part of an asynchronous
17137 The task is waiting on a select statement with only a delay
17140 @item Child Termination Wait
17141 The task is sleeping having completed a master within itself, and is
17142 waiting for the tasks dependent on that master to become terminated or
17143 waiting on a terminate Phase.
17145 @item Wait Child in Term Alt
17146 The task is sleeping waiting for tasks on terminate alternatives to
17147 finish terminating.
17149 @item Accepting RV with @var{taskno}
17150 The task is accepting a rendez-vous with the task @var{taskno}.
17154 Name of the task in the program.
17158 @kindex info task @var{taskno}
17159 @item info task @var{taskno}
17160 This command shows detailled informations on the specified task, as in
17161 the following example:
17166 (@value{GDBP}) info tasks
17167 ID TID P-ID Pri State Name
17168 1 8077880 0 15 Child Activation Wait main_task
17169 * 2 807c468 1 15 Runnable task_1
17170 (@value{GDBP}) info task 2
17171 Ada Task: 0x807c468
17175 Parent: 1 (main_task)
17181 @kindex task@r{ (Ada)}
17182 @cindex current Ada task ID
17183 This command prints the ID of the current task.
17189 (@value{GDBP}) info tasks
17190 ID TID P-ID Pri State Name
17191 1 8077870 0 15 Child Activation Wait main_task
17192 * 2 807c458 1 15 Runnable t
17193 (@value{GDBP}) task
17194 [Current task is 2]
17197 @item task @var{taskno}
17198 @cindex Ada task switching
17199 This command is like the @code{thread @var{thread-id}}
17200 command (@pxref{Threads}). It switches the context of debugging
17201 from the current task to the given task.
17207 (@value{GDBP}) info tasks
17208 ID TID P-ID Pri State Name
17209 1 8077870 0 15 Child Activation Wait main_task
17210 * 2 807c458 1 15 Runnable t
17211 (@value{GDBP}) task 1
17212 [Switching to task 1]
17213 #0 0x8067726 in pthread_cond_wait ()
17215 #0 0x8067726 in pthread_cond_wait ()
17216 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
17217 #2 0x805cb63 in system.task_primitives.operations.sleep ()
17218 #3 0x806153e in system.tasking.stages.activate_tasks ()
17219 #4 0x804aacc in un () at un.adb:5
17222 @item break @var{location} task @var{taskno}
17223 @itemx break @var{location} task @var{taskno} if @dots{}
17224 @cindex breakpoints and tasks, in Ada
17225 @cindex task breakpoints, in Ada
17226 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
17227 These commands are like the @code{break @dots{} thread @dots{}}
17228 command (@pxref{Thread Stops}). The
17229 @var{location} argument specifies source lines, as described
17230 in @ref{Specify Location}.
17232 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
17233 to specify that you only want @value{GDBN} to stop the program when a
17234 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
17235 numeric task identifiers assigned by @value{GDBN}, shown in the first
17236 column of the @samp{info tasks} display.
17238 If you do not specify @samp{task @var{taskno}} when you set a
17239 breakpoint, the breakpoint applies to @emph{all} tasks of your
17242 You can use the @code{task} qualifier on conditional breakpoints as
17243 well; in this case, place @samp{task @var{taskno}} before the
17244 breakpoint condition (before the @code{if}).
17252 (@value{GDBP}) info tasks
17253 ID TID P-ID Pri State Name
17254 1 140022020 0 15 Child Activation Wait main_task
17255 2 140045060 1 15 Accept/Select Wait t2
17256 3 140044840 1 15 Runnable t1
17257 * 4 140056040 1 15 Runnable t3
17258 (@value{GDBP}) b 15 task 2
17259 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
17260 (@value{GDBP}) cont
17265 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
17267 (@value{GDBP}) info tasks
17268 ID TID P-ID Pri State Name
17269 1 140022020 0 15 Child Activation Wait main_task
17270 * 2 140045060 1 15 Runnable t2
17271 3 140044840 1 15 Runnable t1
17272 4 140056040 1 15 Delay Sleep t3
17276 @node Ada Tasks and Core Files
17277 @subsubsection Tasking Support when Debugging Core Files
17278 @cindex Ada tasking and core file debugging
17280 When inspecting a core file, as opposed to debugging a live program,
17281 tasking support may be limited or even unavailable, depending on
17282 the platform being used.
17283 For instance, on x86-linux, the list of tasks is available, but task
17284 switching is not supported.
17286 On certain platforms, the debugger needs to perform some
17287 memory writes in order to provide Ada tasking support. When inspecting
17288 a core file, this means that the core file must be opened with read-write
17289 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
17290 Under these circumstances, you should make a backup copy of the core
17291 file before inspecting it with @value{GDBN}.
17293 @node Ravenscar Profile
17294 @subsubsection Tasking Support when using the Ravenscar Profile
17295 @cindex Ravenscar Profile
17297 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
17298 specifically designed for systems with safety-critical real-time
17302 @kindex set ravenscar task-switching on
17303 @cindex task switching with program using Ravenscar Profile
17304 @item set ravenscar task-switching on
17305 Allows task switching when debugging a program that uses the Ravenscar
17306 Profile. This is the default.
17308 @kindex set ravenscar task-switching off
17309 @item set ravenscar task-switching off
17310 Turn off task switching when debugging a program that uses the Ravenscar
17311 Profile. This is mostly intended to disable the code that adds support
17312 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
17313 the Ravenscar runtime is preventing @value{GDBN} from working properly.
17314 To be effective, this command should be run before the program is started.
17316 @kindex show ravenscar task-switching
17317 @item show ravenscar task-switching
17318 Show whether it is possible to switch from task to task in a program
17319 using the Ravenscar Profile.
17324 @subsubsection Ada Settings
17325 @cindex Ada settings
17328 @kindex set varsize-limit
17329 @item set varsize-limit @var{size}
17330 Prevent @value{GDBN} from attempting to evaluate objects whose size
17331 is above the given limit (@var{size}) when those sizes are computed
17332 from run-time quantities. This is typically the case when the object
17333 has a variable size, such as an array whose bounds are not known at
17334 compile time for example. Setting @var{size} to @code{unlimited}
17335 removes the size limitation. By default, the limit is about 65KB.
17337 The purpose of having such a limit is to prevent @value{GDBN} from
17338 trying to grab enormous chunks of virtual memory when asked to evaluate
17339 a quantity whose bounds have been corrupted or have not yet been fully
17340 initialized. The limit applies to the results of some subexpressions
17341 as well as to complete expressions. For example, an expression denoting
17342 a simple integer component, such as @code{x.y.z}, may fail if the size of
17343 @code{x.y} is variable and exceeds @code{size}. On the other hand,
17344 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
17345 @code{A} is an array variable with non-constant size, will generally
17346 succeed regardless of the bounds on @code{A}, as long as the component
17347 size is less than @var{size}.
17349 @kindex show varsize-limit
17350 @item show varsize-limit
17351 Show the limit on types whose size is determined by run-time quantities.
17355 @subsubsection Known Peculiarities of Ada Mode
17356 @cindex Ada, problems
17358 Besides the omissions listed previously (@pxref{Omissions from Ada}),
17359 we know of several problems with and limitations of Ada mode in
17361 some of which will be fixed with planned future releases of the debugger
17362 and the GNU Ada compiler.
17366 Static constants that the compiler chooses not to materialize as objects in
17367 storage are invisible to the debugger.
17370 Named parameter associations in function argument lists are ignored (the
17371 argument lists are treated as positional).
17374 Many useful library packages are currently invisible to the debugger.
17377 Fixed-point arithmetic, conversions, input, and output is carried out using
17378 floating-point arithmetic, and may give results that only approximate those on
17382 The GNAT compiler never generates the prefix @code{Standard} for any of
17383 the standard symbols defined by the Ada language. @value{GDBN} knows about
17384 this: it will strip the prefix from names when you use it, and will never
17385 look for a name you have so qualified among local symbols, nor match against
17386 symbols in other packages or subprograms. If you have
17387 defined entities anywhere in your program other than parameters and
17388 local variables whose simple names match names in @code{Standard},
17389 GNAT's lack of qualification here can cause confusion. When this happens,
17390 you can usually resolve the confusion
17391 by qualifying the problematic names with package
17392 @code{Standard} explicitly.
17395 Older versions of the compiler sometimes generate erroneous debugging
17396 information, resulting in the debugger incorrectly printing the value
17397 of affected entities. In some cases, the debugger is able to work
17398 around an issue automatically. In other cases, the debugger is able
17399 to work around the issue, but the work-around has to be specifically
17402 @kindex set ada trust-PAD-over-XVS
17403 @kindex show ada trust-PAD-over-XVS
17406 @item set ada trust-PAD-over-XVS on
17407 Configure GDB to strictly follow the GNAT encoding when computing the
17408 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
17409 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
17410 a complete description of the encoding used by the GNAT compiler).
17411 This is the default.
17413 @item set ada trust-PAD-over-XVS off
17414 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
17415 sometimes prints the wrong value for certain entities, changing @code{ada
17416 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
17417 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
17418 @code{off}, but this incurs a slight performance penalty, so it is
17419 recommended to leave this setting to @code{on} unless necessary.
17423 @cindex GNAT descriptive types
17424 @cindex GNAT encoding
17425 Internally, the debugger also relies on the compiler following a number
17426 of conventions known as the @samp{GNAT Encoding}, all documented in
17427 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
17428 how the debugging information should be generated for certain types.
17429 In particular, this convention makes use of @dfn{descriptive types},
17430 which are artificial types generated purely to help the debugger.
17432 These encodings were defined at a time when the debugging information
17433 format used was not powerful enough to describe some of the more complex
17434 types available in Ada. Since DWARF allows us to express nearly all
17435 Ada features, the long-term goal is to slowly replace these descriptive
17436 types by their pure DWARF equivalent. To facilitate that transition,
17437 a new maintenance option is available to force the debugger to ignore
17438 those descriptive types. It allows the user to quickly evaluate how
17439 well @value{GDBN} works without them.
17443 @kindex maint ada set ignore-descriptive-types
17444 @item maintenance ada set ignore-descriptive-types [on|off]
17445 Control whether the debugger should ignore descriptive types.
17446 The default is not to ignore descriptives types (@code{off}).
17448 @kindex maint ada show ignore-descriptive-types
17449 @item maintenance ada show ignore-descriptive-types
17450 Show if descriptive types are ignored by @value{GDBN}.
17454 @node Unsupported Languages
17455 @section Unsupported Languages
17457 @cindex unsupported languages
17458 @cindex minimal language
17459 In addition to the other fully-supported programming languages,
17460 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
17461 It does not represent a real programming language, but provides a set
17462 of capabilities close to what the C or assembly languages provide.
17463 This should allow most simple operations to be performed while debugging
17464 an application that uses a language currently not supported by @value{GDBN}.
17466 If the language is set to @code{auto}, @value{GDBN} will automatically
17467 select this language if the current frame corresponds to an unsupported
17471 @chapter Examining the Symbol Table
17473 The commands described in this chapter allow you to inquire about the
17474 symbols (names of variables, functions and types) defined in your
17475 program. This information is inherent in the text of your program and
17476 does not change as your program executes. @value{GDBN} finds it in your
17477 program's symbol table, in the file indicated when you started @value{GDBN}
17478 (@pxref{File Options, ,Choosing Files}), or by one of the
17479 file-management commands (@pxref{Files, ,Commands to Specify Files}).
17481 @cindex symbol names
17482 @cindex names of symbols
17483 @cindex quoting names
17484 @anchor{quoting names}
17485 Occasionally, you may need to refer to symbols that contain unusual
17486 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17487 most frequent case is in referring to static variables in other
17488 source files (@pxref{Variables,,Program Variables}). File names
17489 are recorded in object files as debugging symbols, but @value{GDBN} would
17490 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17491 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17492 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17499 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17502 @cindex case-insensitive symbol names
17503 @cindex case sensitivity in symbol names
17504 @kindex set case-sensitive
17505 @item set case-sensitive on
17506 @itemx set case-sensitive off
17507 @itemx set case-sensitive auto
17508 Normally, when @value{GDBN} looks up symbols, it matches their names
17509 with case sensitivity determined by the current source language.
17510 Occasionally, you may wish to control that. The command @code{set
17511 case-sensitive} lets you do that by specifying @code{on} for
17512 case-sensitive matches or @code{off} for case-insensitive ones. If
17513 you specify @code{auto}, case sensitivity is reset to the default
17514 suitable for the source language. The default is case-sensitive
17515 matches for all languages except for Fortran, for which the default is
17516 case-insensitive matches.
17518 @kindex show case-sensitive
17519 @item show case-sensitive
17520 This command shows the current setting of case sensitivity for symbols
17523 @kindex set print type methods
17524 @item set print type methods
17525 @itemx set print type methods on
17526 @itemx set print type methods off
17527 Normally, when @value{GDBN} prints a class, it displays any methods
17528 declared in that class. You can control this behavior either by
17529 passing the appropriate flag to @code{ptype}, or using @command{set
17530 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17531 display the methods; this is the default. Specifying @code{off} will
17532 cause @value{GDBN} to omit the methods.
17534 @kindex show print type methods
17535 @item show print type methods
17536 This command shows the current setting of method display when printing
17539 @kindex set print type nested-type-limit
17540 @item set print type nested-type-limit @var{limit}
17541 @itemx set print type nested-type-limit unlimited
17542 Set the limit of displayed nested types that the type printer will
17543 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
17544 nested definitions. By default, the type printer will not show any nested
17545 types defined in classes.
17547 @kindex show print type nested-type-limit
17548 @item show print type nested-type-limit
17549 This command shows the current display limit of nested types when
17552 @kindex set print type typedefs
17553 @item set print type typedefs
17554 @itemx set print type typedefs on
17555 @itemx set print type typedefs off
17557 Normally, when @value{GDBN} prints a class, it displays any typedefs
17558 defined in that class. You can control this behavior either by
17559 passing the appropriate flag to @code{ptype}, or using @command{set
17560 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17561 display the typedef definitions; this is the default. Specifying
17562 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17563 Note that this controls whether the typedef definition itself is
17564 printed, not whether typedef names are substituted when printing other
17567 @kindex show print type typedefs
17568 @item show print type typedefs
17569 This command shows the current setting of typedef display when
17572 @kindex info address
17573 @cindex address of a symbol
17574 @item info address @var{symbol}
17575 Describe where the data for @var{symbol} is stored. For a register
17576 variable, this says which register it is kept in. For a non-register
17577 local variable, this prints the stack-frame offset at which the variable
17580 Note the contrast with @samp{print &@var{symbol}}, which does not work
17581 at all for a register variable, and for a stack local variable prints
17582 the exact address of the current instantiation of the variable.
17584 @kindex info symbol
17585 @cindex symbol from address
17586 @cindex closest symbol and offset for an address
17587 @item info symbol @var{addr}
17588 Print the name of a symbol which is stored at the address @var{addr}.
17589 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17590 nearest symbol and an offset from it:
17593 (@value{GDBP}) info symbol 0x54320
17594 _initialize_vx + 396 in section .text
17598 This is the opposite of the @code{info address} command. You can use
17599 it to find out the name of a variable or a function given its address.
17601 For dynamically linked executables, the name of executable or shared
17602 library containing the symbol is also printed:
17605 (@value{GDBP}) info symbol 0x400225
17606 _start + 5 in section .text of /tmp/a.out
17607 (@value{GDBP}) info symbol 0x2aaaac2811cf
17608 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17613 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17614 Demangle @var{name}.
17615 If @var{language} is provided it is the name of the language to demangle
17616 @var{name} in. Otherwise @var{name} is demangled in the current language.
17618 The @samp{--} option specifies the end of options,
17619 and is useful when @var{name} begins with a dash.
17621 The parameter @code{demangle-style} specifies how to interpret the kind
17622 of mangling used. @xref{Print Settings}.
17625 @item whatis[/@var{flags}] [@var{arg}]
17626 Print the data type of @var{arg}, which can be either an expression
17627 or a name of a data type. With no argument, print the data type of
17628 @code{$}, the last value in the value history.
17630 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17631 is not actually evaluated, and any side-effecting operations (such as
17632 assignments or function calls) inside it do not take place.
17634 If @var{arg} is a variable or an expression, @code{whatis} prints its
17635 literal type as it is used in the source code. If the type was
17636 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17637 the data type underlying the @code{typedef}. If the type of the
17638 variable or the expression is a compound data type, such as
17639 @code{struct} or @code{class}, @code{whatis} never prints their
17640 fields or methods. It just prints the @code{struct}/@code{class}
17641 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17642 such a compound data type, use @code{ptype}.
17644 If @var{arg} is a type name that was defined using @code{typedef},
17645 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17646 Unrolling means that @code{whatis} will show the underlying type used
17647 in the @code{typedef} declaration of @var{arg}. However, if that
17648 underlying type is also a @code{typedef}, @code{whatis} will not
17651 For C code, the type names may also have the form @samp{class
17652 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17653 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17655 @var{flags} can be used to modify how the type is displayed.
17656 Available flags are:
17660 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17661 parameters and typedefs defined in a class when printing the class'
17662 members. The @code{/r} flag disables this.
17665 Do not print methods defined in the class.
17668 Print methods defined in the class. This is the default, but the flag
17669 exists in case you change the default with @command{set print type methods}.
17672 Do not print typedefs defined in the class. Note that this controls
17673 whether the typedef definition itself is printed, not whether typedef
17674 names are substituted when printing other types.
17677 Print typedefs defined in the class. This is the default, but the flag
17678 exists in case you change the default with @command{set print type typedefs}.
17681 Print the offsets and sizes of fields in a struct, similar to what the
17682 @command{pahole} tool does. This option implies the @code{/tm} flags.
17684 For example, given the following declarations:
17720 Issuing a @kbd{ptype /o struct tuv} command would print:
17723 (@value{GDBP}) ptype /o struct tuv
17724 /* offset | size */ type = struct tuv @{
17725 /* 0 | 4 */ int a1;
17726 /* XXX 4-byte hole */
17727 /* 8 | 8 */ char *a2;
17728 /* 16 | 4 */ int a3;
17730 /* total size (bytes): 24 */
17734 Notice the format of the first column of comments. There, you can
17735 find two parts separated by the @samp{|} character: the @emph{offset},
17736 which indicates where the field is located inside the struct, in
17737 bytes, and the @emph{size} of the field. Another interesting line is
17738 the marker of a @emph{hole} in the struct, indicating that it may be
17739 possible to pack the struct and make it use less space by reorganizing
17742 It is also possible to print offsets inside an union:
17745 (@value{GDBP}) ptype /o union qwe
17746 /* offset | size */ type = union qwe @{
17747 /* 24 */ struct tuv @{
17748 /* 0 | 4 */ int a1;
17749 /* XXX 4-byte hole */
17750 /* 8 | 8 */ char *a2;
17751 /* 16 | 4 */ int a3;
17753 /* total size (bytes): 24 */
17755 /* 40 */ struct xyz @{
17756 /* 0 | 4 */ int f1;
17757 /* 4 | 1 */ char f2;
17758 /* XXX 3-byte hole */
17759 /* 8 | 8 */ void *f3;
17760 /* 16 | 24 */ struct tuv @{
17761 /* 16 | 4 */ int a1;
17762 /* XXX 4-byte hole */
17763 /* 24 | 8 */ char *a2;
17764 /* 32 | 4 */ int a3;
17766 /* total size (bytes): 24 */
17769 /* total size (bytes): 40 */
17772 /* total size (bytes): 40 */
17776 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
17777 same space (because we are dealing with an union), the offset is not
17778 printed for them. However, you can still examine the offset of each
17779 of these structures' fields.
17781 Another useful scenario is printing the offsets of a struct containing
17785 (@value{GDBP}) ptype /o struct tyu
17786 /* offset | size */ type = struct tyu @{
17787 /* 0:31 | 4 */ int a1 : 1;
17788 /* 0:28 | 4 */ int a2 : 3;
17789 /* 0: 5 | 4 */ int a3 : 23;
17790 /* 3: 3 | 1 */ signed char a4 : 2;
17791 /* XXX 3-bit hole */
17792 /* XXX 4-byte hole */
17793 /* 8 | 8 */ int64_t a5;
17794 /* 16:27 | 4 */ int a6 : 5;
17795 /* 16:56 | 8 */ int64_t a7 : 3;
17797 /* total size (bytes): 24 */
17801 Note how the offset information is now extended to also include how
17802 many bits are left to be used in each bitfield.
17806 @item ptype[/@var{flags}] [@var{arg}]
17807 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17808 detailed description of the type, instead of just the name of the type.
17809 @xref{Expressions, ,Expressions}.
17811 Contrary to @code{whatis}, @code{ptype} always unrolls any
17812 @code{typedef}s in its argument declaration, whether the argument is
17813 a variable, expression, or a data type. This means that @code{ptype}
17814 of a variable or an expression will not print literally its type as
17815 present in the source code---use @code{whatis} for that. @code{typedef}s at
17816 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17817 fields, methods and inner @code{class typedef}s of @code{struct}s,
17818 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17820 For example, for this variable declaration:
17823 typedef double real_t;
17824 struct complex @{ real_t real; double imag; @};
17825 typedef struct complex complex_t;
17827 real_t *real_pointer_var;
17831 the two commands give this output:
17835 (@value{GDBP}) whatis var
17837 (@value{GDBP}) ptype var
17838 type = struct complex @{
17842 (@value{GDBP}) whatis complex_t
17843 type = struct complex
17844 (@value{GDBP}) whatis struct complex
17845 type = struct complex
17846 (@value{GDBP}) ptype struct complex
17847 type = struct complex @{
17851 (@value{GDBP}) whatis real_pointer_var
17853 (@value{GDBP}) ptype real_pointer_var
17859 As with @code{whatis}, using @code{ptype} without an argument refers to
17860 the type of @code{$}, the last value in the value history.
17862 @cindex incomplete type
17863 Sometimes, programs use opaque data types or incomplete specifications
17864 of complex data structure. If the debug information included in the
17865 program does not allow @value{GDBN} to display a full declaration of
17866 the data type, it will say @samp{<incomplete type>}. For example,
17867 given these declarations:
17871 struct foo *fooptr;
17875 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17878 (@value{GDBP}) ptype foo
17879 $1 = <incomplete type>
17883 ``Incomplete type'' is C terminology for data types that are not
17884 completely specified.
17886 @cindex unknown type
17887 Othertimes, information about a variable's type is completely absent
17888 from the debug information included in the program. This most often
17889 happens when the program or library where the variable is defined
17890 includes no debug information at all. @value{GDBN} knows the variable
17891 exists from inspecting the linker/loader symbol table (e.g., the ELF
17892 dynamic symbol table), but such symbols do not contain type
17893 information. Inspecting the type of a (global) variable for which
17894 @value{GDBN} has no type information shows:
17897 (@value{GDBP}) ptype var
17898 type = <data variable, no debug info>
17901 @xref{Variables, no debug info variables}, for how to print the values
17905 @item info types @var{regexp}
17907 Print a brief description of all types whose names match the regular
17908 expression @var{regexp} (or all types in your program, if you supply
17909 no argument). Each complete typename is matched as though it were a
17910 complete line; thus, @samp{i type value} gives information on all
17911 types in your program whose names include the string @code{value}, but
17912 @samp{i type ^value$} gives information only on types whose complete
17913 name is @code{value}.
17915 In programs using different languages, @value{GDBN} chooses the syntax
17916 to print the type description according to the
17917 @samp{set language} value: using @samp{set language auto}
17918 (see @ref{Automatically, ,Set Language Automatically}) means to use the
17919 language of the type, other values mean to use
17920 the manually specified language (see @ref{Manually, ,Set Language Manually}).
17922 This command differs from @code{ptype} in two ways: first, like
17923 @code{whatis}, it does not print a detailed description; second, it
17924 lists all source files and line numbers where a type is defined.
17926 @kindex info type-printers
17927 @item info type-printers
17928 Versions of @value{GDBN} that ship with Python scripting enabled may
17929 have ``type printers'' available. When using @command{ptype} or
17930 @command{whatis}, these printers are consulted when the name of a type
17931 is needed. @xref{Type Printing API}, for more information on writing
17934 @code{info type-printers} displays all the available type printers.
17936 @kindex enable type-printer
17937 @kindex disable type-printer
17938 @item enable type-printer @var{name}@dots{}
17939 @item disable type-printer @var{name}@dots{}
17940 These commands can be used to enable or disable type printers.
17943 @cindex local variables
17944 @item info scope @var{location}
17945 List all the variables local to a particular scope. This command
17946 accepts a @var{location} argument---a function name, a source line, or
17947 an address preceded by a @samp{*}, and prints all the variables local
17948 to the scope defined by that location. (@xref{Specify Location}, for
17949 details about supported forms of @var{location}.) For example:
17952 (@value{GDBP}) @b{info scope command_line_handler}
17953 Scope for command_line_handler:
17954 Symbol rl is an argument at stack/frame offset 8, length 4.
17955 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17956 Symbol linelength is in static storage at address 0x150a1c, length 4.
17957 Symbol p is a local variable in register $esi, length 4.
17958 Symbol p1 is a local variable in register $ebx, length 4.
17959 Symbol nline is a local variable in register $edx, length 4.
17960 Symbol repeat is a local variable at frame offset -8, length 4.
17964 This command is especially useful for determining what data to collect
17965 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17968 @kindex info source
17970 Show information about the current source file---that is, the source file for
17971 the function containing the current point of execution:
17974 the name of the source file, and the directory containing it,
17976 the directory it was compiled in,
17978 its length, in lines,
17980 which programming language it is written in,
17982 if the debug information provides it, the program that compiled the file
17983 (which may include, e.g., the compiler version and command line arguments),
17985 whether the executable includes debugging information for that file, and
17986 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17988 whether the debugging information includes information about
17989 preprocessor macros.
17993 @kindex info sources
17995 Print the names of all source files in your program for which there is
17996 debugging information, organized into two lists: files whose symbols
17997 have already been read, and files whose symbols will be read when needed.
17999 @kindex info functions
18000 @item info functions [-q]
18001 Print the names and data types of all defined functions.
18002 Similarly to @samp{info types}, this command groups its output by source
18003 files and annotates each function definition with its source line
18006 In programs using different languages, @value{GDBN} chooses the syntax
18007 to print the function name and type according to the
18008 @samp{set language} value: using @samp{set language auto}
18009 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18010 language of the function, other values mean to use
18011 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18013 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18014 printing header information and messages explaining why no functions
18017 @item info functions [-q] [-t @var{type_regexp}] [@var{regexp}]
18018 Like @samp{info functions}, but only print the names and data types
18019 of the functions selected with the provided regexp(s).
18021 If @var{regexp} is provided, print only the functions whose names
18022 match the regular expression @var{regexp}.
18023 Thus, @samp{info fun step} finds all functions whose
18024 names include @code{step}; @samp{info fun ^step} finds those whose names
18025 start with @code{step}. If a function name contains characters that
18026 conflict with the regular expression language (e.g.@:
18027 @samp{operator*()}), they may be quoted with a backslash.
18029 If @var{type_regexp} is provided, print only the functions whose
18030 types, as printed by the @code{whatis} command, match
18031 the regular expression @var{type_regexp}.
18032 If @var{type_regexp} contains space(s), it should be enclosed in
18033 quote characters. If needed, use backslash to escape the meaning
18034 of special characters or quotes.
18035 Thus, @samp{info fun -t '^int ('} finds the functions that return
18036 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
18037 have an argument type containing int; @samp{info fun -t '^int (' ^step}
18038 finds the functions whose names start with @code{step} and that return
18041 If both @var{regexp} and @var{type_regexp} are provided, a function
18042 is printed only if its name matches @var{regexp} and its type matches
18046 @kindex info variables
18047 @item info variables [-q]
18048 Print the names and data types of all variables that are defined
18049 outside of functions (i.e.@: excluding local variables).
18050 The printed variables are grouped by source files and annotated with
18051 their respective source line numbers.
18053 In programs using different languages, @value{GDBN} chooses the syntax
18054 to print the variable name and type according to the
18055 @samp{set language} value: using @samp{set language auto}
18056 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18057 language of the variable, other values mean to use
18058 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18060 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18061 printing header information and messages explaining why no variables
18064 @item info variables [-q] [-t @var{type_regexp}] [@var{regexp}]
18065 Like @kbd{info variables}, but only print the variables selected
18066 with the provided regexp(s).
18068 If @var{regexp} is provided, print only the variables whose names
18069 match the regular expression @var{regexp}.
18071 If @var{type_regexp} is provided, print only the variables whose
18072 types, as printed by the @code{whatis} command, match
18073 the regular expression @var{type_regexp}.
18074 If @var{type_regexp} contains space(s), it should be enclosed in
18075 quote characters. If needed, use backslash to escape the meaning
18076 of special characters or quotes.
18078 If both @var{regexp} and @var{type_regexp} are provided, an argument
18079 is printed only if its name matches @var{regexp} and its type matches
18082 @kindex info classes
18083 @cindex Objective-C, classes and selectors
18085 @itemx info classes @var{regexp}
18086 Display all Objective-C classes in your program, or
18087 (with the @var{regexp} argument) all those matching a particular regular
18090 @kindex info selectors
18091 @item info selectors
18092 @itemx info selectors @var{regexp}
18093 Display all Objective-C selectors in your program, or
18094 (with the @var{regexp} argument) all those matching a particular regular
18098 This was never implemented.
18099 @kindex info methods
18101 @itemx info methods @var{regexp}
18102 The @code{info methods} command permits the user to examine all defined
18103 methods within C@t{++} program, or (with the @var{regexp} argument) a
18104 specific set of methods found in the various C@t{++} classes. Many
18105 C@t{++} classes provide a large number of methods. Thus, the output
18106 from the @code{ptype} command can be overwhelming and hard to use. The
18107 @code{info-methods} command filters the methods, printing only those
18108 which match the regular-expression @var{regexp}.
18111 @cindex opaque data types
18112 @kindex set opaque-type-resolution
18113 @item set opaque-type-resolution on
18114 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
18115 declared as a pointer to a @code{struct}, @code{class}, or
18116 @code{union}---for example, @code{struct MyType *}---that is used in one
18117 source file although the full declaration of @code{struct MyType} is in
18118 another source file. The default is on.
18120 A change in the setting of this subcommand will not take effect until
18121 the next time symbols for a file are loaded.
18123 @item set opaque-type-resolution off
18124 Tell @value{GDBN} not to resolve opaque types. In this case, the type
18125 is printed as follows:
18127 @{<no data fields>@}
18130 @kindex show opaque-type-resolution
18131 @item show opaque-type-resolution
18132 Show whether opaque types are resolved or not.
18134 @kindex set print symbol-loading
18135 @cindex print messages when symbols are loaded
18136 @item set print symbol-loading
18137 @itemx set print symbol-loading full
18138 @itemx set print symbol-loading brief
18139 @itemx set print symbol-loading off
18140 The @code{set print symbol-loading} command allows you to control the
18141 printing of messages when @value{GDBN} loads symbol information.
18142 By default a message is printed for the executable and one for each
18143 shared library, and normally this is what you want. However, when
18144 debugging apps with large numbers of shared libraries these messages
18146 When set to @code{brief} a message is printed for each executable,
18147 and when @value{GDBN} loads a collection of shared libraries at once
18148 it will only print one message regardless of the number of shared
18149 libraries. When set to @code{off} no messages are printed.
18151 @kindex show print symbol-loading
18152 @item show print symbol-loading
18153 Show whether messages will be printed when a @value{GDBN} command
18154 entered from the keyboard causes symbol information to be loaded.
18156 @kindex maint print symbols
18157 @cindex symbol dump
18158 @kindex maint print psymbols
18159 @cindex partial symbol dump
18160 @kindex maint print msymbols
18161 @cindex minimal symbol dump
18162 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
18163 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18164 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18165 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18166 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18167 Write a dump of debugging symbol data into the file @var{filename} or
18168 the terminal if @var{filename} is unspecified.
18169 If @code{-objfile @var{objfile}} is specified, only dump symbols for
18171 If @code{-pc @var{address}} is specified, only dump symbols for the file
18172 with code at that address. Note that @var{address} may be a symbol like
18174 If @code{-source @var{source}} is specified, only dump symbols for that
18177 These commands are used to debug the @value{GDBN} symbol-reading code.
18178 These commands do not modify internal @value{GDBN} state, therefore
18179 @samp{maint print symbols} will only print symbols for already expanded symbol
18181 You can use the command @code{info sources} to find out which files these are.
18182 If you use @samp{maint print psymbols} instead, the dump shows information
18183 about symbols that @value{GDBN} only knows partially---that is, symbols
18184 defined in files that @value{GDBN} has skimmed, but not yet read completely.
18185 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
18188 @xref{Files, ,Commands to Specify Files}, for a discussion of how
18189 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
18191 @kindex maint info symtabs
18192 @kindex maint info psymtabs
18193 @cindex listing @value{GDBN}'s internal symbol tables
18194 @cindex symbol tables, listing @value{GDBN}'s internal
18195 @cindex full symbol tables, listing @value{GDBN}'s internal
18196 @cindex partial symbol tables, listing @value{GDBN}'s internal
18197 @item maint info symtabs @r{[} @var{regexp} @r{]}
18198 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
18200 List the @code{struct symtab} or @code{struct partial_symtab}
18201 structures whose names match @var{regexp}. If @var{regexp} is not
18202 given, list them all. The output includes expressions which you can
18203 copy into a @value{GDBN} debugging this one to examine a particular
18204 structure in more detail. For example:
18207 (@value{GDBP}) maint info psymtabs dwarf2read
18208 @{ objfile /home/gnu/build/gdb/gdb
18209 ((struct objfile *) 0x82e69d0)
18210 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
18211 ((struct partial_symtab *) 0x8474b10)
18214 text addresses 0x814d3c8 -- 0x8158074
18215 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
18216 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
18217 dependencies (none)
18220 (@value{GDBP}) maint info symtabs
18224 We see that there is one partial symbol table whose filename contains
18225 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
18226 and we see that @value{GDBN} has not read in any symtabs yet at all.
18227 If we set a breakpoint on a function, that will cause @value{GDBN} to
18228 read the symtab for the compilation unit containing that function:
18231 (@value{GDBP}) break dwarf2_psymtab_to_symtab
18232 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
18234 (@value{GDBP}) maint info symtabs
18235 @{ objfile /home/gnu/build/gdb/gdb
18236 ((struct objfile *) 0x82e69d0)
18237 @{ symtab /home/gnu/src/gdb/dwarf2read.c
18238 ((struct symtab *) 0x86c1f38)
18241 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
18242 linetable ((struct linetable *) 0x8370fa0)
18243 debugformat DWARF 2
18249 @kindex maint info line-table
18250 @cindex listing @value{GDBN}'s internal line tables
18251 @cindex line tables, listing @value{GDBN}'s internal
18252 @item maint info line-table @r{[} @var{regexp} @r{]}
18254 List the @code{struct linetable} from all @code{struct symtab}
18255 instances whose name matches @var{regexp}. If @var{regexp} is not
18256 given, list the @code{struct linetable} from all @code{struct symtab}.
18258 @kindex maint set symbol-cache-size
18259 @cindex symbol cache size
18260 @item maint set symbol-cache-size @var{size}
18261 Set the size of the symbol cache to @var{size}.
18262 The default size is intended to be good enough for debugging
18263 most applications. This option exists to allow for experimenting
18264 with different sizes.
18266 @kindex maint show symbol-cache-size
18267 @item maint show symbol-cache-size
18268 Show the size of the symbol cache.
18270 @kindex maint print symbol-cache
18271 @cindex symbol cache, printing its contents
18272 @item maint print symbol-cache
18273 Print the contents of the symbol cache.
18274 This is useful when debugging symbol cache issues.
18276 @kindex maint print symbol-cache-statistics
18277 @cindex symbol cache, printing usage statistics
18278 @item maint print symbol-cache-statistics
18279 Print symbol cache usage statistics.
18280 This helps determine how well the cache is being utilized.
18282 @kindex maint flush-symbol-cache
18283 @cindex symbol cache, flushing
18284 @item maint flush-symbol-cache
18285 Flush the contents of the symbol cache, all entries are removed.
18286 This command is useful when debugging the symbol cache.
18287 It is also useful when collecting performance data.
18292 @chapter Altering Execution
18294 Once you think you have found an error in your program, you might want to
18295 find out for certain whether correcting the apparent error would lead to
18296 correct results in the rest of the run. You can find the answer by
18297 experiment, using the @value{GDBN} features for altering execution of the
18300 For example, you can store new values into variables or memory
18301 locations, give your program a signal, restart it at a different
18302 address, or even return prematurely from a function.
18305 * Assignment:: Assignment to variables
18306 * Jumping:: Continuing at a different address
18307 * Signaling:: Giving your program a signal
18308 * Returning:: Returning from a function
18309 * Calling:: Calling your program's functions
18310 * Patching:: Patching your program
18311 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
18315 @section Assignment to Variables
18318 @cindex setting variables
18319 To alter the value of a variable, evaluate an assignment expression.
18320 @xref{Expressions, ,Expressions}. For example,
18327 stores the value 4 into the variable @code{x}, and then prints the
18328 value of the assignment expression (which is 4).
18329 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
18330 information on operators in supported languages.
18332 @kindex set variable
18333 @cindex variables, setting
18334 If you are not interested in seeing the value of the assignment, use the
18335 @code{set} command instead of the @code{print} command. @code{set} is
18336 really the same as @code{print} except that the expression's value is
18337 not printed and is not put in the value history (@pxref{Value History,
18338 ,Value History}). The expression is evaluated only for its effects.
18340 If the beginning of the argument string of the @code{set} command
18341 appears identical to a @code{set} subcommand, use the @code{set
18342 variable} command instead of just @code{set}. This command is identical
18343 to @code{set} except for its lack of subcommands. For example, if your
18344 program has a variable @code{width}, you get an error if you try to set
18345 a new value with just @samp{set width=13}, because @value{GDBN} has the
18346 command @code{set width}:
18349 (@value{GDBP}) whatis width
18351 (@value{GDBP}) p width
18353 (@value{GDBP}) set width=47
18354 Invalid syntax in expression.
18358 The invalid expression, of course, is @samp{=47}. In
18359 order to actually set the program's variable @code{width}, use
18362 (@value{GDBP}) set var width=47
18365 Because the @code{set} command has many subcommands that can conflict
18366 with the names of program variables, it is a good idea to use the
18367 @code{set variable} command instead of just @code{set}. For example, if
18368 your program has a variable @code{g}, you run into problems if you try
18369 to set a new value with just @samp{set g=4}, because @value{GDBN} has
18370 the command @code{set gnutarget}, abbreviated @code{set g}:
18374 (@value{GDBP}) whatis g
18378 (@value{GDBP}) set g=4
18382 The program being debugged has been started already.
18383 Start it from the beginning? (y or n) y
18384 Starting program: /home/smith/cc_progs/a.out
18385 "/home/smith/cc_progs/a.out": can't open to read symbols:
18386 Invalid bfd target.
18387 (@value{GDBP}) show g
18388 The current BFD target is "=4".
18393 The program variable @code{g} did not change, and you silently set the
18394 @code{gnutarget} to an invalid value. In order to set the variable
18398 (@value{GDBP}) set var g=4
18401 @value{GDBN} allows more implicit conversions in assignments than C; you can
18402 freely store an integer value into a pointer variable or vice versa,
18403 and you can convert any structure to any other structure that is the
18404 same length or shorter.
18405 @comment FIXME: how do structs align/pad in these conversions?
18406 @comment /doc@cygnus.com 18dec1990
18408 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
18409 construct to generate a value of specified type at a specified address
18410 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
18411 to memory location @code{0x83040} as an integer (which implies a certain size
18412 and representation in memory), and
18415 set @{int@}0x83040 = 4
18419 stores the value 4 into that memory location.
18422 @section Continuing at a Different Address
18424 Ordinarily, when you continue your program, you do so at the place where
18425 it stopped, with the @code{continue} command. You can instead continue at
18426 an address of your own choosing, with the following commands:
18430 @kindex j @r{(@code{jump})}
18431 @item jump @var{location}
18432 @itemx j @var{location}
18433 Resume execution at @var{location}. Execution stops again immediately
18434 if there is a breakpoint there. @xref{Specify Location}, for a description
18435 of the different forms of @var{location}. It is common
18436 practice to use the @code{tbreak} command in conjunction with
18437 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
18439 The @code{jump} command does not change the current stack frame, or
18440 the stack pointer, or the contents of any memory location or any
18441 register other than the program counter. If @var{location} is in
18442 a different function from the one currently executing, the results may
18443 be bizarre if the two functions expect different patterns of arguments or
18444 of local variables. For this reason, the @code{jump} command requests
18445 confirmation if the specified line is not in the function currently
18446 executing. However, even bizarre results are predictable if you are
18447 well acquainted with the machine-language code of your program.
18450 On many systems, you can get much the same effect as the @code{jump}
18451 command by storing a new value into the register @code{$pc}. The
18452 difference is that this does not start your program running; it only
18453 changes the address of where it @emph{will} run when you continue. For
18461 makes the next @code{continue} command or stepping command execute at
18462 address @code{0x485}, rather than at the address where your program stopped.
18463 @xref{Continuing and Stepping, ,Continuing and Stepping}.
18465 The most common occasion to use the @code{jump} command is to back
18466 up---perhaps with more breakpoints set---over a portion of a program
18467 that has already executed, in order to examine its execution in more
18472 @section Giving your Program a Signal
18473 @cindex deliver a signal to a program
18477 @item signal @var{signal}
18478 Resume execution where your program is stopped, but immediately give it the
18479 signal @var{signal}. The @var{signal} can be the name or the number of a
18480 signal. For example, on many systems @code{signal 2} and @code{signal
18481 SIGINT} are both ways of sending an interrupt signal.
18483 Alternatively, if @var{signal} is zero, continue execution without
18484 giving a signal. This is useful when your program stopped on account of
18485 a signal and would ordinarily see the signal when resumed with the
18486 @code{continue} command; @samp{signal 0} causes it to resume without a
18489 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
18490 delivered to the currently selected thread, not the thread that last
18491 reported a stop. This includes the situation where a thread was
18492 stopped due to a signal. So if you want to continue execution
18493 suppressing the signal that stopped a thread, you should select that
18494 same thread before issuing the @samp{signal 0} command. If you issue
18495 the @samp{signal 0} command with another thread as the selected one,
18496 @value{GDBN} detects that and asks for confirmation.
18498 Invoking the @code{signal} command is not the same as invoking the
18499 @code{kill} utility from the shell. Sending a signal with @code{kill}
18500 causes @value{GDBN} to decide what to do with the signal depending on
18501 the signal handling tables (@pxref{Signals}). The @code{signal} command
18502 passes the signal directly to your program.
18504 @code{signal} does not repeat when you press @key{RET} a second time
18505 after executing the command.
18507 @kindex queue-signal
18508 @item queue-signal @var{signal}
18509 Queue @var{signal} to be delivered immediately to the current thread
18510 when execution of the thread resumes. The @var{signal} can be the name or
18511 the number of a signal. For example, on many systems @code{signal 2} and
18512 @code{signal SIGINT} are both ways of sending an interrupt signal.
18513 The handling of the signal must be set to pass the signal to the program,
18514 otherwise @value{GDBN} will report an error.
18515 You can control the handling of signals from @value{GDBN} with the
18516 @code{handle} command (@pxref{Signals}).
18518 Alternatively, if @var{signal} is zero, any currently queued signal
18519 for the current thread is discarded and when execution resumes no signal
18520 will be delivered. This is useful when your program stopped on account
18521 of a signal and would ordinarily see the signal when resumed with the
18522 @code{continue} command.
18524 This command differs from the @code{signal} command in that the signal
18525 is just queued, execution is not resumed. And @code{queue-signal} cannot
18526 be used to pass a signal whose handling state has been set to @code{nopass}
18531 @xref{stepping into signal handlers}, for information on how stepping
18532 commands behave when the thread has a signal queued.
18535 @section Returning from a Function
18538 @cindex returning from a function
18541 @itemx return @var{expression}
18542 You can cancel execution of a function call with the @code{return}
18543 command. If you give an
18544 @var{expression} argument, its value is used as the function's return
18548 When you use @code{return}, @value{GDBN} discards the selected stack frame
18549 (and all frames within it). You can think of this as making the
18550 discarded frame return prematurely. If you wish to specify a value to
18551 be returned, give that value as the argument to @code{return}.
18553 This pops the selected stack frame (@pxref{Selection, ,Selecting a
18554 Frame}), and any other frames inside of it, leaving its caller as the
18555 innermost remaining frame. That frame becomes selected. The
18556 specified value is stored in the registers used for returning values
18559 The @code{return} command does not resume execution; it leaves the
18560 program stopped in the state that would exist if the function had just
18561 returned. In contrast, the @code{finish} command (@pxref{Continuing
18562 and Stepping, ,Continuing and Stepping}) resumes execution until the
18563 selected stack frame returns naturally.
18565 @value{GDBN} needs to know how the @var{expression} argument should be set for
18566 the inferior. The concrete registers assignment depends on the OS ABI and the
18567 type being returned by the selected stack frame. For example it is common for
18568 OS ABI to return floating point values in FPU registers while integer values in
18569 CPU registers. Still some ABIs return even floating point values in CPU
18570 registers. Larger integer widths (such as @code{long long int}) also have
18571 specific placement rules. @value{GDBN} already knows the OS ABI from its
18572 current target so it needs to find out also the type being returned to make the
18573 assignment into the right register(s).
18575 Normally, the selected stack frame has debug info. @value{GDBN} will always
18576 use the debug info instead of the implicit type of @var{expression} when the
18577 debug info is available. For example, if you type @kbd{return -1}, and the
18578 function in the current stack frame is declared to return a @code{long long
18579 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
18580 into a @code{long long int}:
18583 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
18585 (@value{GDBP}) return -1
18586 Make func return now? (y or n) y
18587 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
18588 43 printf ("result=%lld\n", func ());
18592 However, if the selected stack frame does not have a debug info, e.g., if the
18593 function was compiled without debug info, @value{GDBN} has to find out the type
18594 to return from user. Specifying a different type by mistake may set the value
18595 in different inferior registers than the caller code expects. For example,
18596 typing @kbd{return -1} with its implicit type @code{int} would set only a part
18597 of a @code{long long int} result for a debug info less function (on 32-bit
18598 architectures). Therefore the user is required to specify the return type by
18599 an appropriate cast explicitly:
18602 Breakpoint 2, 0x0040050b in func ()
18603 (@value{GDBP}) return -1
18604 Return value type not available for selected stack frame.
18605 Please use an explicit cast of the value to return.
18606 (@value{GDBP}) return (long long int) -1
18607 Make selected stack frame return now? (y or n) y
18608 #0 0x00400526 in main ()
18613 @section Calling Program Functions
18616 @cindex calling functions
18617 @cindex inferior functions, calling
18618 @item print @var{expr}
18619 Evaluate the expression @var{expr} and display the resulting value.
18620 The expression may include calls to functions in the program being
18624 @item call @var{expr}
18625 Evaluate the expression @var{expr} without displaying @code{void}
18628 You can use this variant of the @code{print} command if you want to
18629 execute a function from your program that does not return anything
18630 (a.k.a.@: @dfn{a void function}), but without cluttering the output
18631 with @code{void} returned values that @value{GDBN} will otherwise
18632 print. If the result is not void, it is printed and saved in the
18636 It is possible for the function you call via the @code{print} or
18637 @code{call} command to generate a signal (e.g., if there's a bug in
18638 the function, or if you passed it incorrect arguments). What happens
18639 in that case is controlled by the @code{set unwindonsignal} command.
18641 Similarly, with a C@t{++} program it is possible for the function you
18642 call via the @code{print} or @code{call} command to generate an
18643 exception that is not handled due to the constraints of the dummy
18644 frame. In this case, any exception that is raised in the frame, but has
18645 an out-of-frame exception handler will not be found. GDB builds a
18646 dummy-frame for the inferior function call, and the unwinder cannot
18647 seek for exception handlers outside of this dummy-frame. What happens
18648 in that case is controlled by the
18649 @code{set unwind-on-terminating-exception} command.
18652 @item set unwindonsignal
18653 @kindex set unwindonsignal
18654 @cindex unwind stack in called functions
18655 @cindex call dummy stack unwinding
18656 Set unwinding of the stack if a signal is received while in a function
18657 that @value{GDBN} called in the program being debugged. If set to on,
18658 @value{GDBN} unwinds the stack it created for the call and restores
18659 the context to what it was before the call. If set to off (the
18660 default), @value{GDBN} stops in the frame where the signal was
18663 @item show unwindonsignal
18664 @kindex show unwindonsignal
18665 Show the current setting of stack unwinding in the functions called by
18668 @item set unwind-on-terminating-exception
18669 @kindex set unwind-on-terminating-exception
18670 @cindex unwind stack in called functions with unhandled exceptions
18671 @cindex call dummy stack unwinding on unhandled exception.
18672 Set unwinding of the stack if a C@t{++} exception is raised, but left
18673 unhandled while in a function that @value{GDBN} called in the program being
18674 debugged. If set to on (the default), @value{GDBN} unwinds the stack
18675 it created for the call and restores the context to what it was before
18676 the call. If set to off, @value{GDBN} the exception is delivered to
18677 the default C@t{++} exception handler and the inferior terminated.
18679 @item show unwind-on-terminating-exception
18680 @kindex show unwind-on-terminating-exception
18681 Show the current setting of stack unwinding in the functions called by
18686 @subsection Calling functions with no debug info
18688 @cindex no debug info functions
18689 Sometimes, a function you wish to call is missing debug information.
18690 In such case, @value{GDBN} does not know the type of the function,
18691 including the types of the function's parameters. To avoid calling
18692 the inferior function incorrectly, which could result in the called
18693 function functioning erroneously and even crash, @value{GDBN} refuses
18694 to call the function unless you tell it the type of the function.
18696 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18697 to do that. The simplest is to cast the call to the function's
18698 declared return type. For example:
18701 (@value{GDBP}) p getenv ("PATH")
18702 'getenv' has unknown return type; cast the call to its declared return type
18703 (@value{GDBP}) p (char *) getenv ("PATH")
18704 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18707 Casting the return type of a no-debug function is equivalent to
18708 casting the function to a pointer to a prototyped function that has a
18709 prototype that matches the types of the passed-in arguments, and
18710 calling that. I.e., the call above is equivalent to:
18713 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18717 and given this prototyped C or C++ function with float parameters:
18720 float multiply (float v1, float v2) @{ return v1 * v2; @}
18724 these calls are equivalent:
18727 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18728 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18731 If the function you wish to call is declared as unprototyped (i.e.@:
18732 old K&R style), you must use the cast-to-function-pointer syntax, so
18733 that @value{GDBN} knows that it needs to apply default argument
18734 promotions (promote float arguments to double). @xref{ABI, float
18735 promotion}. For example, given this unprototyped C function with
18736 float parameters, and no debug info:
18740 multiply_noproto (v1, v2)
18748 you call it like this:
18751 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18755 @section Patching Programs
18757 @cindex patching binaries
18758 @cindex writing into executables
18759 @cindex writing into corefiles
18761 By default, @value{GDBN} opens the file containing your program's
18762 executable code (or the corefile) read-only. This prevents accidental
18763 alterations to machine code; but it also prevents you from intentionally
18764 patching your program's binary.
18766 If you'd like to be able to patch the binary, you can specify that
18767 explicitly with the @code{set write} command. For example, you might
18768 want to turn on internal debugging flags, or even to make emergency
18774 @itemx set write off
18775 If you specify @samp{set write on}, @value{GDBN} opens executable and
18776 core files for both reading and writing; if you specify @kbd{set write
18777 off} (the default), @value{GDBN} opens them read-only.
18779 If you have already loaded a file, you must load it again (using the
18780 @code{exec-file} or @code{core-file} command) after changing @code{set
18781 write}, for your new setting to take effect.
18785 Display whether executable files and core files are opened for writing
18786 as well as reading.
18789 @node Compiling and Injecting Code
18790 @section Compiling and injecting code in @value{GDBN}
18791 @cindex injecting code
18792 @cindex writing into executables
18793 @cindex compiling code
18795 @value{GDBN} supports on-demand compilation and code injection into
18796 programs running under @value{GDBN}. GCC 5.0 or higher built with
18797 @file{libcc1.so} must be installed for this functionality to be enabled.
18798 This functionality is implemented with the following commands.
18801 @kindex compile code
18802 @item compile code @var{source-code}
18803 @itemx compile code -raw @var{--} @var{source-code}
18804 Compile @var{source-code} with the compiler language found as the current
18805 language in @value{GDBN} (@pxref{Languages}). If compilation and
18806 injection is not supported with the current language specified in
18807 @value{GDBN}, or the compiler does not support this feature, an error
18808 message will be printed. If @var{source-code} compiles and links
18809 successfully, @value{GDBN} will load the object-code emitted,
18810 and execute it within the context of the currently selected inferior.
18811 It is important to note that the compiled code is executed immediately.
18812 After execution, the compiled code is removed from @value{GDBN} and any
18813 new types or variables you have defined will be deleted.
18815 The command allows you to specify @var{source-code} in two ways.
18816 The simplest method is to provide a single line of code to the command.
18820 compile code printf ("hello world\n");
18823 If you specify options on the command line as well as source code, they
18824 may conflict. The @samp{--} delimiter can be used to separate options
18825 from actual source code. E.g.:
18828 compile code -r -- printf ("hello world\n");
18831 Alternatively you can enter source code as multiple lines of text. To
18832 enter this mode, invoke the @samp{compile code} command without any text
18833 following the command. This will start the multiple-line editor and
18834 allow you to type as many lines of source code as required. When you
18835 have completed typing, enter @samp{end} on its own line to exit the
18840 >printf ("hello\n");
18841 >printf ("world\n");
18845 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18846 provided @var{source-code} in a callable scope. In this case, you must
18847 specify the entry point of the code by defining a function named
18848 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18849 inferior. Using @samp{-raw} option may be needed for example when
18850 @var{source-code} requires @samp{#include} lines which may conflict with
18851 inferior symbols otherwise.
18853 @kindex compile file
18854 @item compile file @var{filename}
18855 @itemx compile file -raw @var{filename}
18856 Like @code{compile code}, but take the source code from @var{filename}.
18859 compile file /home/user/example.c
18864 @item compile print @var{expr}
18865 @itemx compile print /@var{f} @var{expr}
18866 Compile and execute @var{expr} with the compiler language found as the
18867 current language in @value{GDBN} (@pxref{Languages}). By default the
18868 value of @var{expr} is printed in a format appropriate to its data type;
18869 you can choose a different format by specifying @samp{/@var{f}}, where
18870 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18873 @item compile print
18874 @itemx compile print /@var{f}
18875 @cindex reprint the last value
18876 Alternatively you can enter the expression (source code producing it) as
18877 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18878 command without any text following the command. This will start the
18879 multiple-line editor.
18883 The process of compiling and injecting the code can be inspected using:
18886 @anchor{set debug compile}
18887 @item set debug compile
18888 @cindex compile command debugging info
18889 Turns on or off display of @value{GDBN} process of compiling and
18890 injecting the code. The default is off.
18892 @item show debug compile
18893 Displays the current state of displaying @value{GDBN} process of
18894 compiling and injecting the code.
18896 @anchor{set debug compile-cplus-types}
18897 @item set debug compile-cplus-types
18898 @cindex compile C@t{++} type conversion
18899 Turns on or off the display of C@t{++} type conversion debugging information.
18900 The default is off.
18902 @item show debug compile-cplus-types
18903 Displays the current state of displaying debugging information for
18904 C@t{++} type conversion.
18907 @subsection Compilation options for the @code{compile} command
18909 @value{GDBN} needs to specify the right compilation options for the code
18910 to be injected, in part to make its ABI compatible with the inferior
18911 and in part to make the injected code compatible with @value{GDBN}'s
18915 The options used, in increasing precedence:
18918 @item target architecture and OS options (@code{gdbarch})
18919 These options depend on target processor type and target operating
18920 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18921 (@code{-m64}) compilation option.
18923 @item compilation options recorded in the target
18924 @value{NGCC} (since version 4.7) stores the options used for compilation
18925 into @code{DW_AT_producer} part of DWARF debugging information according
18926 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18927 explicitly specify @code{-g} during inferior compilation otherwise
18928 @value{NGCC} produces no DWARF. This feature is only relevant for
18929 platforms where @code{-g} produces DWARF by default, otherwise one may
18930 try to enforce DWARF by using @code{-gdwarf-4}.
18932 @item compilation options set by @code{set compile-args}
18936 You can override compilation options using the following command:
18939 @item set compile-args
18940 @cindex compile command options override
18941 Set compilation options used for compiling and injecting code with the
18942 @code{compile} commands. These options override any conflicting ones
18943 from the target architecture and/or options stored during inferior
18946 @item show compile-args
18947 Displays the current state of compilation options override.
18948 This does not show all the options actually used during compilation,
18949 use @ref{set debug compile} for that.
18952 @subsection Caveats when using the @code{compile} command
18954 There are a few caveats to keep in mind when using the @code{compile}
18955 command. As the caveats are different per language, the table below
18956 highlights specific issues on a per language basis.
18959 @item C code examples and caveats
18960 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18961 attempt to compile the source code with a @samp{C} compiler. The source
18962 code provided to the @code{compile} command will have much the same
18963 access to variables and types as it normally would if it were part of
18964 the program currently being debugged in @value{GDBN}.
18966 Below is a sample program that forms the basis of the examples that
18967 follow. This program has been compiled and loaded into @value{GDBN},
18968 much like any other normal debugging session.
18971 void function1 (void)
18974 printf ("function 1\n");
18977 void function2 (void)
18992 For the purposes of the examples in this section, the program above has
18993 been compiled, loaded into @value{GDBN}, stopped at the function
18994 @code{main}, and @value{GDBN} is awaiting input from the user.
18996 To access variables and types for any program in @value{GDBN}, the
18997 program must be compiled and packaged with debug information. The
18998 @code{compile} command is not an exception to this rule. Without debug
18999 information, you can still use the @code{compile} command, but you will
19000 be very limited in what variables and types you can access.
19002 So with that in mind, the example above has been compiled with debug
19003 information enabled. The @code{compile} command will have access to
19004 all variables and types (except those that may have been optimized
19005 out). Currently, as @value{GDBN} has stopped the program in the
19006 @code{main} function, the @code{compile} command would have access to
19007 the variable @code{k}. You could invoke the @code{compile} command
19008 and type some source code to set the value of @code{k}. You can also
19009 read it, or do anything with that variable you would normally do in
19010 @code{C}. Be aware that changes to inferior variables in the
19011 @code{compile} command are persistent. In the following example:
19014 compile code k = 3;
19018 the variable @code{k} is now 3. It will retain that value until
19019 something else in the example program changes it, or another
19020 @code{compile} command changes it.
19022 Normal scope and access rules apply to source code compiled and
19023 injected by the @code{compile} command. In the example, the variables
19024 @code{j} and @code{k} are not accessible yet, because the program is
19025 currently stopped in the @code{main} function, where these variables
19026 are not in scope. Therefore, the following command
19029 compile code j = 3;
19033 will result in a compilation error message.
19035 Once the program is continued, execution will bring these variables in
19036 scope, and they will become accessible; then the code you specify via
19037 the @code{compile} command will be able to access them.
19039 You can create variables and types with the @code{compile} command as
19040 part of your source code. Variables and types that are created as part
19041 of the @code{compile} command are not visible to the rest of the program for
19042 the duration of its run. This example is valid:
19045 compile code int ff = 5; printf ("ff is %d\n", ff);
19048 However, if you were to type the following into @value{GDBN} after that
19049 command has completed:
19052 compile code printf ("ff is %d\n'', ff);
19056 a compiler error would be raised as the variable @code{ff} no longer
19057 exists. Object code generated and injected by the @code{compile}
19058 command is removed when its execution ends. Caution is advised
19059 when assigning to program variables values of variables created by the
19060 code submitted to the @code{compile} command. This example is valid:
19063 compile code int ff = 5; k = ff;
19066 The value of the variable @code{ff} is assigned to @code{k}. The variable
19067 @code{k} does not require the existence of @code{ff} to maintain the value
19068 it has been assigned. However, pointers require particular care in
19069 assignment. If the source code compiled with the @code{compile} command
19070 changed the address of a pointer in the example program, perhaps to a
19071 variable created in the @code{compile} command, that pointer would point
19072 to an invalid location when the command exits. The following example
19073 would likely cause issues with your debugged program:
19076 compile code int ff = 5; p = &ff;
19079 In this example, @code{p} would point to @code{ff} when the
19080 @code{compile} command is executing the source code provided to it.
19081 However, as variables in the (example) program persist with their
19082 assigned values, the variable @code{p} would point to an invalid
19083 location when the command exists. A general rule should be followed
19084 in that you should either assign @code{NULL} to any assigned pointers,
19085 or restore a valid location to the pointer before the command exits.
19087 Similar caution must be exercised with any structs, unions, and typedefs
19088 defined in @code{compile} command. Types defined in the @code{compile}
19089 command will no longer be available in the next @code{compile} command.
19090 Therefore, if you cast a variable to a type defined in the
19091 @code{compile} command, care must be taken to ensure that any future
19092 need to resolve the type can be achieved.
19095 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
19096 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
19097 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
19098 Compilation failed.
19099 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
19103 Variables that have been optimized away by the compiler are not
19104 accessible to the code submitted to the @code{compile} command.
19105 Access to those variables will generate a compiler error which @value{GDBN}
19106 will print to the console.
19109 @subsection Compiler search for the @code{compile} command
19111 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
19112 which may not be obvious for remote targets of different architecture
19113 than where @value{GDBN} is running. Environment variable @code{PATH} on
19114 @value{GDBN} host is searched for @value{NGCC} binary matching the
19115 target architecture and operating system. This search can be overriden
19116 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
19117 taken from shell that executed @value{GDBN}, it is not the value set by
19118 @value{GDBN} command @code{set environment}). @xref{Environment}.
19121 Specifically @code{PATH} is searched for binaries matching regular expression
19122 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
19123 debugged. @var{arch} is processor name --- multiarch is supported, so for
19124 example both @code{i386} and @code{x86_64} targets look for pattern
19125 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
19126 for pattern @code{s390x?}. @var{os} is currently supported only for
19127 pattern @code{linux(-gnu)?}.
19129 On Posix hosts the compiler driver @value{GDBN} needs to find also
19130 shared library @file{libcc1.so} from the compiler. It is searched in
19131 default shared library search path (overridable with usual environment
19132 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
19133 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
19134 according to the installation of the found compiler --- as possibly
19135 specified by the @code{set compile-gcc} command.
19138 @item set compile-gcc
19139 @cindex compile command driver filename override
19140 Set compilation command used for compiling and injecting code with the
19141 @code{compile} commands. If this option is not set (it is set to
19142 an empty string), the search described above will occur --- that is the
19145 @item show compile-gcc
19146 Displays the current compile command @value{NGCC} driver filename.
19147 If set, it is the main command @command{gcc}, found usually for example
19148 under name @file{x86_64-linux-gnu-gcc}.
19152 @chapter @value{GDBN} Files
19154 @value{GDBN} needs to know the file name of the program to be debugged,
19155 both in order to read its symbol table and in order to start your
19156 program. To debug a core dump of a previous run, you must also tell
19157 @value{GDBN} the name of the core dump file.
19160 * Files:: Commands to specify files
19161 * File Caching:: Information about @value{GDBN}'s file caching
19162 * Separate Debug Files:: Debugging information in separate files
19163 * MiniDebugInfo:: Debugging information in a special section
19164 * Index Files:: Index files speed up GDB
19165 * Symbol Errors:: Errors reading symbol files
19166 * Data Files:: GDB data files
19170 @section Commands to Specify Files
19172 @cindex symbol table
19173 @cindex core dump file
19175 You may want to specify executable and core dump file names. The usual
19176 way to do this is at start-up time, using the arguments to
19177 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
19178 Out of @value{GDBN}}).
19180 Occasionally it is necessary to change to a different file during a
19181 @value{GDBN} session. Or you may run @value{GDBN} and forget to
19182 specify a file you want to use. Or you are debugging a remote target
19183 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
19184 Program}). In these situations the @value{GDBN} commands to specify
19185 new files are useful.
19188 @cindex executable file
19190 @item file @var{filename}
19191 Use @var{filename} as the program to be debugged. It is read for its
19192 symbols and for the contents of pure memory. It is also the program
19193 executed when you use the @code{run} command. If you do not specify a
19194 directory and the file is not found in the @value{GDBN} working directory,
19195 @value{GDBN} uses the environment variable @code{PATH} as a list of
19196 directories to search, just as the shell does when looking for a program
19197 to run. You can change the value of this variable, for both @value{GDBN}
19198 and your program, using the @code{path} command.
19200 @cindex unlinked object files
19201 @cindex patching object files
19202 You can load unlinked object @file{.o} files into @value{GDBN} using
19203 the @code{file} command. You will not be able to ``run'' an object
19204 file, but you can disassemble functions and inspect variables. Also,
19205 if the underlying BFD functionality supports it, you could use
19206 @kbd{gdb -write} to patch object files using this technique. Note
19207 that @value{GDBN} can neither interpret nor modify relocations in this
19208 case, so branches and some initialized variables will appear to go to
19209 the wrong place. But this feature is still handy from time to time.
19212 @code{file} with no argument makes @value{GDBN} discard any information it
19213 has on both executable file and the symbol table.
19216 @item exec-file @r{[} @var{filename} @r{]}
19217 Specify that the program to be run (but not the symbol table) is found
19218 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
19219 if necessary to locate your program. Omitting @var{filename} means to
19220 discard information on the executable file.
19222 @kindex symbol-file
19223 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
19224 Read symbol table information from file @var{filename}. @code{PATH} is
19225 searched when necessary. Use the @code{file} command to get both symbol
19226 table and program to run from the same file.
19228 If an optional @var{offset} is specified, it is added to the start
19229 address of each section in the symbol file. This is useful if the
19230 program is relocated at runtime, such as the Linux kernel with kASLR
19233 @code{symbol-file} with no argument clears out @value{GDBN} information on your
19234 program's symbol table.
19236 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
19237 some breakpoints and auto-display expressions. This is because they may
19238 contain pointers to the internal data recording symbols and data types,
19239 which are part of the old symbol table data being discarded inside
19242 @code{symbol-file} does not repeat if you press @key{RET} again after
19245 When @value{GDBN} is configured for a particular environment, it
19246 understands debugging information in whatever format is the standard
19247 generated for that environment; you may use either a @sc{gnu} compiler, or
19248 other compilers that adhere to the local conventions.
19249 Best results are usually obtained from @sc{gnu} compilers; for example,
19250 using @code{@value{NGCC}} you can generate debugging information for
19253 For most kinds of object files, with the exception of old SVR3 systems
19254 using COFF, the @code{symbol-file} command does not normally read the
19255 symbol table in full right away. Instead, it scans the symbol table
19256 quickly to find which source files and which symbols are present. The
19257 details are read later, one source file at a time, as they are needed.
19259 The purpose of this two-stage reading strategy is to make @value{GDBN}
19260 start up faster. For the most part, it is invisible except for
19261 occasional pauses while the symbol table details for a particular source
19262 file are being read. (The @code{set verbose} command can turn these
19263 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
19264 Warnings and Messages}.)
19266 We have not implemented the two-stage strategy for COFF yet. When the
19267 symbol table is stored in COFF format, @code{symbol-file} reads the
19268 symbol table data in full right away. Note that ``stabs-in-COFF''
19269 still does the two-stage strategy, since the debug info is actually
19273 @cindex reading symbols immediately
19274 @cindex symbols, reading immediately
19275 @item symbol-file @r{[} -readnow @r{]} @var{filename}
19276 @itemx file @r{[} -readnow @r{]} @var{filename}
19277 You can override the @value{GDBN} two-stage strategy for reading symbol
19278 tables by using the @samp{-readnow} option with any of the commands that
19279 load symbol table information, if you want to be sure @value{GDBN} has the
19280 entire symbol table available.
19282 @cindex @code{-readnever}, option for symbol-file command
19283 @cindex never read symbols
19284 @cindex symbols, never read
19285 @item symbol-file @r{[} -readnever @r{]} @var{filename}
19286 @itemx file @r{[} -readnever @r{]} @var{filename}
19287 You can instruct @value{GDBN} to never read the symbolic information
19288 contained in @var{filename} by using the @samp{-readnever} option.
19289 @xref{--readnever}.
19291 @c FIXME: for now no mention of directories, since this seems to be in
19292 @c flux. 13mar1992 status is that in theory GDB would look either in
19293 @c current dir or in same dir as myprog; but issues like competing
19294 @c GDB's, or clutter in system dirs, mean that in practice right now
19295 @c only current dir is used. FFish says maybe a special GDB hierarchy
19296 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
19300 @item core-file @r{[}@var{filename}@r{]}
19302 Specify the whereabouts of a core dump file to be used as the ``contents
19303 of memory''. Traditionally, core files contain only some parts of the
19304 address space of the process that generated them; @value{GDBN} can access the
19305 executable file itself for other parts.
19307 @code{core-file} with no argument specifies that no core file is
19310 Note that the core file is ignored when your program is actually running
19311 under @value{GDBN}. So, if you have been running your program and you
19312 wish to debug a core file instead, you must kill the subprocess in which
19313 the program is running. To do this, use the @code{kill} command
19314 (@pxref{Kill Process, ,Killing the Child Process}).
19316 @kindex add-symbol-file
19317 @cindex dynamic linking
19318 @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{]}
19319 The @code{add-symbol-file} command reads additional symbol table
19320 information from the file @var{filename}. You would use this command
19321 when @var{filename} has been dynamically loaded (by some other means)
19322 into the program that is running. The @var{textaddress} parameter gives
19323 the memory address at which the file's text section has been loaded.
19324 You can additionally specify the base address of other sections using
19325 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
19326 If a section is omitted, @value{GDBN} will use its default addresses
19327 as found in @var{filename}. Any @var{address} or @var{textaddress}
19328 can be given as an expression.
19330 If an optional @var{offset} is specified, it is added to the start
19331 address of each section, except those for which the address was
19332 specified explicitly.
19334 The symbol table of the file @var{filename} is added to the symbol table
19335 originally read with the @code{symbol-file} command. You can use the
19336 @code{add-symbol-file} command any number of times; the new symbol data
19337 thus read is kept in addition to the old.
19339 Changes can be reverted using the command @code{remove-symbol-file}.
19341 @cindex relocatable object files, reading symbols from
19342 @cindex object files, relocatable, reading symbols from
19343 @cindex reading symbols from relocatable object files
19344 @cindex symbols, reading from relocatable object files
19345 @cindex @file{.o} files, reading symbols from
19346 Although @var{filename} is typically a shared library file, an
19347 executable file, or some other object file which has been fully
19348 relocated for loading into a process, you can also load symbolic
19349 information from relocatable @file{.o} files, as long as:
19353 the file's symbolic information refers only to linker symbols defined in
19354 that file, not to symbols defined by other object files,
19356 every section the file's symbolic information refers to has actually
19357 been loaded into the inferior, as it appears in the file, and
19359 you can determine the address at which every section was loaded, and
19360 provide these to the @code{add-symbol-file} command.
19364 Some embedded operating systems, like Sun Chorus and VxWorks, can load
19365 relocatable files into an already running program; such systems
19366 typically make the requirements above easy to meet. However, it's
19367 important to recognize that many native systems use complex link
19368 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
19369 assembly, for example) that make the requirements difficult to meet. In
19370 general, one cannot assume that using @code{add-symbol-file} to read a
19371 relocatable object file's symbolic information will have the same effect
19372 as linking the relocatable object file into the program in the normal
19375 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
19377 @kindex remove-symbol-file
19378 @item remove-symbol-file @var{filename}
19379 @item remove-symbol-file -a @var{address}
19380 Remove a symbol file added via the @code{add-symbol-file} command. The
19381 file to remove can be identified by its @var{filename} or by an @var{address}
19382 that lies within the boundaries of this symbol file in memory. Example:
19385 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
19386 add symbol table from file "/home/user/gdb/mylib.so" at
19387 .text_addr = 0x7ffff7ff9480
19389 Reading symbols from /home/user/gdb/mylib.so...done.
19390 (gdb) remove-symbol-file -a 0x7ffff7ff9480
19391 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
19396 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
19398 @kindex add-symbol-file-from-memory
19399 @cindex @code{syscall DSO}
19400 @cindex load symbols from memory
19401 @item add-symbol-file-from-memory @var{address}
19402 Load symbols from the given @var{address} in a dynamically loaded
19403 object file whose image is mapped directly into the inferior's memory.
19404 For example, the Linux kernel maps a @code{syscall DSO} into each
19405 process's address space; this DSO provides kernel-specific code for
19406 some system calls. The argument can be any expression whose
19407 evaluation yields the address of the file's shared object file header.
19408 For this command to work, you must have used @code{symbol-file} or
19409 @code{exec-file} commands in advance.
19412 @item section @var{section} @var{addr}
19413 The @code{section} command changes the base address of the named
19414 @var{section} of the exec file to @var{addr}. This can be used if the
19415 exec file does not contain section addresses, (such as in the
19416 @code{a.out} format), or when the addresses specified in the file
19417 itself are wrong. Each section must be changed separately. The
19418 @code{info files} command, described below, lists all the sections and
19422 @kindex info target
19425 @code{info files} and @code{info target} are synonymous; both print the
19426 current target (@pxref{Targets, ,Specifying a Debugging Target}),
19427 including the names of the executable and core dump files currently in
19428 use by @value{GDBN}, and the files from which symbols were loaded. The
19429 command @code{help target} lists all possible targets rather than
19432 @kindex maint info sections
19433 @item maint info sections
19434 Another command that can give you extra information about program sections
19435 is @code{maint info sections}. In addition to the section information
19436 displayed by @code{info files}, this command displays the flags and file
19437 offset of each section in the executable and core dump files. In addition,
19438 @code{maint info sections} provides the following command options (which
19439 may be arbitrarily combined):
19443 Display sections for all loaded object files, including shared libraries.
19444 @item @var{sections}
19445 Display info only for named @var{sections}.
19446 @item @var{section-flags}
19447 Display info only for sections for which @var{section-flags} are true.
19448 The section flags that @value{GDBN} currently knows about are:
19451 Section will have space allocated in the process when loaded.
19452 Set for all sections except those containing debug information.
19454 Section will be loaded from the file into the child process memory.
19455 Set for pre-initialized code and data, clear for @code{.bss} sections.
19457 Section needs to be relocated before loading.
19459 Section cannot be modified by the child process.
19461 Section contains executable code only.
19463 Section contains data only (no executable code).
19465 Section will reside in ROM.
19467 Section contains data for constructor/destructor lists.
19469 Section is not empty.
19471 An instruction to the linker to not output the section.
19472 @item COFF_SHARED_LIBRARY
19473 A notification to the linker that the section contains
19474 COFF shared library information.
19476 Section contains common symbols.
19479 @kindex set trust-readonly-sections
19480 @cindex read-only sections
19481 @item set trust-readonly-sections on
19482 Tell @value{GDBN} that readonly sections in your object file
19483 really are read-only (i.e.@: that their contents will not change).
19484 In that case, @value{GDBN} can fetch values from these sections
19485 out of the object file, rather than from the target program.
19486 For some targets (notably embedded ones), this can be a significant
19487 enhancement to debugging performance.
19489 The default is off.
19491 @item set trust-readonly-sections off
19492 Tell @value{GDBN} not to trust readonly sections. This means that
19493 the contents of the section might change while the program is running,
19494 and must therefore be fetched from the target when needed.
19496 @item show trust-readonly-sections
19497 Show the current setting of trusting readonly sections.
19500 All file-specifying commands allow both absolute and relative file names
19501 as arguments. @value{GDBN} always converts the file name to an absolute file
19502 name and remembers it that way.
19504 @cindex shared libraries
19505 @anchor{Shared Libraries}
19506 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
19507 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
19508 DSBT (TIC6X) shared libraries.
19510 On MS-Windows @value{GDBN} must be linked with the Expat library to support
19511 shared libraries. @xref{Expat}.
19513 @value{GDBN} automatically loads symbol definitions from shared libraries
19514 when you use the @code{run} command, or when you examine a core file.
19515 (Before you issue the @code{run} command, @value{GDBN} does not understand
19516 references to a function in a shared library, however---unless you are
19517 debugging a core file).
19519 @c FIXME: some @value{GDBN} release may permit some refs to undef
19520 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
19521 @c FIXME...lib; check this from time to time when updating manual
19523 There are times, however, when you may wish to not automatically load
19524 symbol definitions from shared libraries, such as when they are
19525 particularly large or there are many of them.
19527 To control the automatic loading of shared library symbols, use the
19531 @kindex set auto-solib-add
19532 @item set auto-solib-add @var{mode}
19533 If @var{mode} is @code{on}, symbols from all shared object libraries
19534 will be loaded automatically when the inferior begins execution, you
19535 attach to an independently started inferior, or when the dynamic linker
19536 informs @value{GDBN} that a new library has been loaded. If @var{mode}
19537 is @code{off}, symbols must be loaded manually, using the
19538 @code{sharedlibrary} command. The default value is @code{on}.
19540 @cindex memory used for symbol tables
19541 If your program uses lots of shared libraries with debug info that
19542 takes large amounts of memory, you can decrease the @value{GDBN}
19543 memory footprint by preventing it from automatically loading the
19544 symbols from shared libraries. To that end, type @kbd{set
19545 auto-solib-add off} before running the inferior, then load each
19546 library whose debug symbols you do need with @kbd{sharedlibrary
19547 @var{regexp}}, where @var{regexp} is a regular expression that matches
19548 the libraries whose symbols you want to be loaded.
19550 @kindex show auto-solib-add
19551 @item show auto-solib-add
19552 Display the current autoloading mode.
19555 @cindex load shared library
19556 To explicitly load shared library symbols, use the @code{sharedlibrary}
19560 @kindex info sharedlibrary
19562 @item info share @var{regex}
19563 @itemx info sharedlibrary @var{regex}
19564 Print the names of the shared libraries which are currently loaded
19565 that match @var{regex}. If @var{regex} is omitted then print
19566 all shared libraries that are loaded.
19569 @item info dll @var{regex}
19570 This is an alias of @code{info sharedlibrary}.
19572 @kindex sharedlibrary
19574 @item sharedlibrary @var{regex}
19575 @itemx share @var{regex}
19576 Load shared object library symbols for files matching a
19577 Unix regular expression.
19578 As with files loaded automatically, it only loads shared libraries
19579 required by your program for a core file or after typing @code{run}. If
19580 @var{regex} is omitted all shared libraries required by your program are
19583 @item nosharedlibrary
19584 @kindex nosharedlibrary
19585 @cindex unload symbols from shared libraries
19586 Unload all shared object library symbols. This discards all symbols
19587 that have been loaded from all shared libraries. Symbols from shared
19588 libraries that were loaded by explicit user requests are not
19592 Sometimes you may wish that @value{GDBN} stops and gives you control
19593 when any of shared library events happen. The best way to do this is
19594 to use @code{catch load} and @code{catch unload} (@pxref{Set
19597 @value{GDBN} also supports the the @code{set stop-on-solib-events}
19598 command for this. This command exists for historical reasons. It is
19599 less useful than setting a catchpoint, because it does not allow for
19600 conditions or commands as a catchpoint does.
19603 @item set stop-on-solib-events
19604 @kindex set stop-on-solib-events
19605 This command controls whether @value{GDBN} should give you control
19606 when the dynamic linker notifies it about some shared library event.
19607 The most common event of interest is loading or unloading of a new
19610 @item show stop-on-solib-events
19611 @kindex show stop-on-solib-events
19612 Show whether @value{GDBN} stops and gives you control when shared
19613 library events happen.
19616 Shared libraries are also supported in many cross or remote debugging
19617 configurations. @value{GDBN} needs to have access to the target's libraries;
19618 this can be accomplished either by providing copies of the libraries
19619 on the host system, or by asking @value{GDBN} to automatically retrieve the
19620 libraries from the target. If copies of the target libraries are
19621 provided, they need to be the same as the target libraries, although the
19622 copies on the target can be stripped as long as the copies on the host are
19625 @cindex where to look for shared libraries
19626 For remote debugging, you need to tell @value{GDBN} where the target
19627 libraries are, so that it can load the correct copies---otherwise, it
19628 may try to load the host's libraries. @value{GDBN} has two variables
19629 to specify the search directories for target libraries.
19632 @cindex prefix for executable and shared library file names
19633 @cindex system root, alternate
19634 @kindex set solib-absolute-prefix
19635 @kindex set sysroot
19636 @item set sysroot @var{path}
19637 Use @var{path} as the system root for the program being debugged. Any
19638 absolute shared library paths will be prefixed with @var{path}; many
19639 runtime loaders store the absolute paths to the shared library in the
19640 target program's memory. When starting processes remotely, and when
19641 attaching to already-running processes (local or remote), their
19642 executable filenames will be prefixed with @var{path} if reported to
19643 @value{GDBN} as absolute by the operating system. If you use
19644 @code{set sysroot} to find executables and shared libraries, they need
19645 to be laid out in the same way that they are on the target, with
19646 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
19649 If @var{path} starts with the sequence @file{target:} and the target
19650 system is remote then @value{GDBN} will retrieve the target binaries
19651 from the remote system. This is only supported when using a remote
19652 target that supports the @code{remote get} command (@pxref{File
19653 Transfer,,Sending files to a remote system}). The part of @var{path}
19654 following the initial @file{target:} (if present) is used as system
19655 root prefix on the remote file system. If @var{path} starts with the
19656 sequence @file{remote:} this is converted to the sequence
19657 @file{target:} by @code{set sysroot}@footnote{Historically the
19658 functionality to retrieve binaries from the remote system was
19659 provided by prefixing @var{path} with @file{remote:}}. If you want
19660 to specify a local system root using a directory that happens to be
19661 named @file{target:} or @file{remote:}, you need to use some
19662 equivalent variant of the name like @file{./target:}.
19664 For targets with an MS-DOS based filesystem, such as MS-Windows and
19665 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
19666 absolute file name with @var{path}. But first, on Unix hosts,
19667 @value{GDBN} converts all backslash directory separators into forward
19668 slashes, because the backslash is not a directory separator on Unix:
19671 c:\foo\bar.dll @result{} c:/foo/bar.dll
19674 Then, @value{GDBN} attempts prefixing the target file name with
19675 @var{path}, and looks for the resulting file name in the host file
19679 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
19682 If that does not find the binary, @value{GDBN} tries removing
19683 the @samp{:} character from the drive spec, both for convenience, and,
19684 for the case of the host file system not supporting file names with
19688 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
19691 This makes it possible to have a system root that mirrors a target
19692 with more than one drive. E.g., you may want to setup your local
19693 copies of the target system shared libraries like so (note @samp{c} vs
19697 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19698 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19699 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19703 and point the system root at @file{/path/to/sysroot}, so that
19704 @value{GDBN} can find the correct copies of both
19705 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19707 If that still does not find the binary, @value{GDBN} tries
19708 removing the whole drive spec from the target file name:
19711 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19714 This last lookup makes it possible to not care about the drive name,
19715 if you don't want or need to.
19717 The @code{set solib-absolute-prefix} command is an alias for @code{set
19720 @cindex default system root
19721 @cindex @samp{--with-sysroot}
19722 You can set the default system root by using the configure-time
19723 @samp{--with-sysroot} option. If the system root is inside
19724 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19725 @samp{--exec-prefix}), then the default system root will be updated
19726 automatically if the installed @value{GDBN} is moved to a new
19729 @kindex show sysroot
19731 Display the current executable and shared library prefix.
19733 @kindex set solib-search-path
19734 @item set solib-search-path @var{path}
19735 If this variable is set, @var{path} is a colon-separated list of
19736 directories to search for shared libraries. @samp{solib-search-path}
19737 is used after @samp{sysroot} fails to locate the library, or if the
19738 path to the library is relative instead of absolute. If you want to
19739 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19740 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19741 finding your host's libraries. @samp{sysroot} is preferred; setting
19742 it to a nonexistent directory may interfere with automatic loading
19743 of shared library symbols.
19745 @kindex show solib-search-path
19746 @item show solib-search-path
19747 Display the current shared library search path.
19749 @cindex DOS file-name semantics of file names.
19750 @kindex set target-file-system-kind (unix|dos-based|auto)
19751 @kindex show target-file-system-kind
19752 @item set target-file-system-kind @var{kind}
19753 Set assumed file system kind for target reported file names.
19755 Shared library file names as reported by the target system may not
19756 make sense as is on the system @value{GDBN} is running on. For
19757 example, when remote debugging a target that has MS-DOS based file
19758 system semantics, from a Unix host, the target may be reporting to
19759 @value{GDBN} a list of loaded shared libraries with file names such as
19760 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19761 drive letters, so the @samp{c:\} prefix is not normally understood as
19762 indicating an absolute file name, and neither is the backslash
19763 normally considered a directory separator character. In that case,
19764 the native file system would interpret this whole absolute file name
19765 as a relative file name with no directory components. This would make
19766 it impossible to point @value{GDBN} at a copy of the remote target's
19767 shared libraries on the host using @code{set sysroot}, and impractical
19768 with @code{set solib-search-path}. Setting
19769 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19770 to interpret such file names similarly to how the target would, and to
19771 map them to file names valid on @value{GDBN}'s native file system
19772 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19773 to one of the supported file system kinds. In that case, @value{GDBN}
19774 tries to determine the appropriate file system variant based on the
19775 current target's operating system (@pxref{ABI, ,Configuring the
19776 Current ABI}). The supported file system settings are:
19780 Instruct @value{GDBN} to assume the target file system is of Unix
19781 kind. Only file names starting the forward slash (@samp{/}) character
19782 are considered absolute, and the directory separator character is also
19786 Instruct @value{GDBN} to assume the target file system is DOS based.
19787 File names starting with either a forward slash, or a drive letter
19788 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19789 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19790 considered directory separators.
19793 Instruct @value{GDBN} to use the file system kind associated with the
19794 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19795 This is the default.
19799 @cindex file name canonicalization
19800 @cindex base name differences
19801 When processing file names provided by the user, @value{GDBN}
19802 frequently needs to compare them to the file names recorded in the
19803 program's debug info. Normally, @value{GDBN} compares just the
19804 @dfn{base names} of the files as strings, which is reasonably fast
19805 even for very large programs. (The base name of a file is the last
19806 portion of its name, after stripping all the leading directories.)
19807 This shortcut in comparison is based upon the assumption that files
19808 cannot have more than one base name. This is usually true, but
19809 references to files that use symlinks or similar filesystem
19810 facilities violate that assumption. If your program records files
19811 using such facilities, or if you provide file names to @value{GDBN}
19812 using symlinks etc., you can set @code{basenames-may-differ} to
19813 @code{true} to instruct @value{GDBN} to completely canonicalize each
19814 pair of file names it needs to compare. This will make file-name
19815 comparisons accurate, but at a price of a significant slowdown.
19818 @item set basenames-may-differ
19819 @kindex set basenames-may-differ
19820 Set whether a source file may have multiple base names.
19822 @item show basenames-may-differ
19823 @kindex show basenames-may-differ
19824 Show whether a source file may have multiple base names.
19828 @section File Caching
19829 @cindex caching of opened files
19830 @cindex caching of bfd objects
19832 To speed up file loading, and reduce memory usage, @value{GDBN} will
19833 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19834 BFD, bfd, The Binary File Descriptor Library}. The following commands
19835 allow visibility and control of the caching behavior.
19838 @kindex maint info bfds
19839 @item maint info bfds
19840 This prints information about each @code{bfd} object that is known to
19843 @kindex maint set bfd-sharing
19844 @kindex maint show bfd-sharing
19845 @kindex bfd caching
19846 @item maint set bfd-sharing
19847 @item maint show bfd-sharing
19848 Control whether @code{bfd} objects can be shared. When sharing is
19849 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19850 than reopening the same file. Turning sharing off does not cause
19851 already shared @code{bfd} objects to be unshared, but all future files
19852 that are opened will create a new @code{bfd} object. Similarly,
19853 re-enabling sharing does not cause multiple existing @code{bfd}
19854 objects to be collapsed into a single shared @code{bfd} object.
19856 @kindex set debug bfd-cache @var{level}
19857 @kindex bfd caching
19858 @item set debug bfd-cache @var{level}
19859 Turns on debugging of the bfd cache, setting the level to @var{level}.
19861 @kindex show debug bfd-cache
19862 @kindex bfd caching
19863 @item show debug bfd-cache
19864 Show the current debugging level of the bfd cache.
19867 @node Separate Debug Files
19868 @section Debugging Information in Separate Files
19869 @cindex separate debugging information files
19870 @cindex debugging information in separate files
19871 @cindex @file{.debug} subdirectories
19872 @cindex debugging information directory, global
19873 @cindex global debugging information directories
19874 @cindex build ID, and separate debugging files
19875 @cindex @file{.build-id} directory
19877 @value{GDBN} allows you to put a program's debugging information in a
19878 file separate from the executable itself, in a way that allows
19879 @value{GDBN} to find and load the debugging information automatically.
19880 Since debugging information can be very large---sometimes larger
19881 than the executable code itself---some systems distribute debugging
19882 information for their executables in separate files, which users can
19883 install only when they need to debug a problem.
19885 @value{GDBN} supports two ways of specifying the separate debug info
19890 The executable contains a @dfn{debug link} that specifies the name of
19891 the separate debug info file. The separate debug file's name is
19892 usually @file{@var{executable}.debug}, where @var{executable} is the
19893 name of the corresponding executable file without leading directories
19894 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19895 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19896 checksum for the debug file, which @value{GDBN} uses to validate that
19897 the executable and the debug file came from the same build.
19900 The executable contains a @dfn{build ID}, a unique bit string that is
19901 also present in the corresponding debug info file. (This is supported
19902 only on some operating systems, when using the ELF or PE file formats
19903 for binary files and the @sc{gnu} Binutils.) For more details about
19904 this feature, see the description of the @option{--build-id}
19905 command-line option in @ref{Options, , Command Line Options, ld,
19906 The GNU Linker}. The debug info file's name is not specified
19907 explicitly by the build ID, but can be computed from the build ID, see
19911 Depending on the way the debug info file is specified, @value{GDBN}
19912 uses two different methods of looking for the debug file:
19916 For the ``debug link'' method, @value{GDBN} looks up the named file in
19917 the directory of the executable file, then in a subdirectory of that
19918 directory named @file{.debug}, and finally under each one of the global debug
19919 directories, in a subdirectory whose name is identical to the leading
19920 directories of the executable's absolute file name.
19923 For the ``build ID'' method, @value{GDBN} looks in the
19924 @file{.build-id} subdirectory of each one of the global debug directories for
19925 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19926 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19927 are the rest of the bit string. (Real build ID strings are 32 or more
19928 hex characters, not 10.)
19931 So, for example, suppose you ask @value{GDBN} to debug
19932 @file{/usr/bin/ls}, which has a debug link that specifies the
19933 file @file{ls.debug}, and a build ID whose value in hex is
19934 @code{abcdef1234}. If the list of the global debug directories includes
19935 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19936 debug information files, in the indicated order:
19940 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19942 @file{/usr/bin/ls.debug}
19944 @file{/usr/bin/.debug/ls.debug}
19946 @file{/usr/lib/debug/usr/bin/ls.debug}.
19949 @anchor{debug-file-directory}
19950 Global debugging info directories default to what is set by @value{GDBN}
19951 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19952 you can also set the global debugging info directories, and view the list
19953 @value{GDBN} is currently using.
19957 @kindex set debug-file-directory
19958 @item set debug-file-directory @var{directories}
19959 Set the directories which @value{GDBN} searches for separate debugging
19960 information files to @var{directory}. Multiple path components can be set
19961 concatenating them by a path separator.
19963 @kindex show debug-file-directory
19964 @item show debug-file-directory
19965 Show the directories @value{GDBN} searches for separate debugging
19970 @cindex @code{.gnu_debuglink} sections
19971 @cindex debug link sections
19972 A debug link is a special section of the executable file named
19973 @code{.gnu_debuglink}. The section must contain:
19977 A filename, with any leading directory components removed, followed by
19980 zero to three bytes of padding, as needed to reach the next four-byte
19981 boundary within the section, and
19983 a four-byte CRC checksum, stored in the same endianness used for the
19984 executable file itself. The checksum is computed on the debugging
19985 information file's full contents by the function given below, passing
19986 zero as the @var{crc} argument.
19989 Any executable file format can carry a debug link, as long as it can
19990 contain a section named @code{.gnu_debuglink} with the contents
19993 @cindex @code{.note.gnu.build-id} sections
19994 @cindex build ID sections
19995 The build ID is a special section in the executable file (and in other
19996 ELF binary files that @value{GDBN} may consider). This section is
19997 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19998 It contains unique identification for the built files---the ID remains
19999 the same across multiple builds of the same build tree. The default
20000 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
20001 content for the build ID string. The same section with an identical
20002 value is present in the original built binary with symbols, in its
20003 stripped variant, and in the separate debugging information file.
20005 The debugging information file itself should be an ordinary
20006 executable, containing a full set of linker symbols, sections, and
20007 debugging information. The sections of the debugging information file
20008 should have the same names, addresses, and sizes as the original file,
20009 but they need not contain any data---much like a @code{.bss} section
20010 in an ordinary executable.
20012 The @sc{gnu} binary utilities (Binutils) package includes the
20013 @samp{objcopy} utility that can produce
20014 the separated executable / debugging information file pairs using the
20015 following commands:
20018 @kbd{objcopy --only-keep-debug foo foo.debug}
20023 These commands remove the debugging
20024 information from the executable file @file{foo} and place it in the file
20025 @file{foo.debug}. You can use the first, second or both methods to link the
20030 The debug link method needs the following additional command to also leave
20031 behind a debug link in @file{foo}:
20034 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
20037 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
20038 a version of the @code{strip} command such that the command @kbd{strip foo -f
20039 foo.debug} has the same functionality as the two @code{objcopy} commands and
20040 the @code{ln -s} command above, together.
20043 Build ID gets embedded into the main executable using @code{ld --build-id} or
20044 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
20045 compatibility fixes for debug files separation are present in @sc{gnu} binary
20046 utilities (Binutils) package since version 2.18.
20051 @cindex CRC algorithm definition
20052 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
20053 IEEE 802.3 using the polynomial:
20055 @c TexInfo requires naked braces for multi-digit exponents for Tex
20056 @c output, but this causes HTML output to barf. HTML has to be set using
20057 @c raw commands. So we end up having to specify this equation in 2
20062 <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>
20063 + <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
20069 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
20070 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
20074 The function is computed byte at a time, taking the least
20075 significant bit of each byte first. The initial pattern
20076 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
20077 the final result is inverted to ensure trailing zeros also affect the
20080 @emph{Note:} This is the same CRC polynomial as used in handling the
20081 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
20082 However in the case of the Remote Serial Protocol, the CRC is computed
20083 @emph{most} significant bit first, and the result is not inverted, so
20084 trailing zeros have no effect on the CRC value.
20086 To complete the description, we show below the code of the function
20087 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
20088 initially supplied @code{crc} argument means that an initial call to
20089 this function passing in zero will start computing the CRC using
20092 @kindex gnu_debuglink_crc32
20095 gnu_debuglink_crc32 (unsigned long crc,
20096 unsigned char *buf, size_t len)
20098 static const unsigned long crc32_table[256] =
20100 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
20101 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
20102 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
20103 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
20104 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
20105 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
20106 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
20107 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
20108 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
20109 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
20110 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
20111 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
20112 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
20113 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
20114 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
20115 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
20116 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
20117 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
20118 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
20119 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
20120 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
20121 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
20122 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
20123 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
20124 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
20125 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
20126 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
20127 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
20128 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
20129 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
20130 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
20131 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
20132 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
20133 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
20134 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
20135 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
20136 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
20137 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
20138 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
20139 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
20140 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
20141 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
20142 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
20143 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
20144 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
20145 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
20146 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
20147 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
20148 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
20149 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
20150 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
20153 unsigned char *end;
20155 crc = ~crc & 0xffffffff;
20156 for (end = buf + len; buf < end; ++buf)
20157 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
20158 return ~crc & 0xffffffff;
20163 This computation does not apply to the ``build ID'' method.
20165 @node MiniDebugInfo
20166 @section Debugging information in a special section
20167 @cindex separate debug sections
20168 @cindex @samp{.gnu_debugdata} section
20170 Some systems ship pre-built executables and libraries that have a
20171 special @samp{.gnu_debugdata} section. This feature is called
20172 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
20173 is used to supply extra symbols for backtraces.
20175 The intent of this section is to provide extra minimal debugging
20176 information for use in simple backtraces. It is not intended to be a
20177 replacement for full separate debugging information (@pxref{Separate
20178 Debug Files}). The example below shows the intended use; however,
20179 @value{GDBN} does not currently put restrictions on what sort of
20180 debugging information might be included in the section.
20182 @value{GDBN} has support for this extension. If the section exists,
20183 then it is used provided that no other source of debugging information
20184 can be found, and that @value{GDBN} was configured with LZMA support.
20186 This section can be easily created using @command{objcopy} and other
20187 standard utilities:
20190 # Extract the dynamic symbols from the main binary, there is no need
20191 # to also have these in the normal symbol table.
20192 nm -D @var{binary} --format=posix --defined-only \
20193 | awk '@{ print $1 @}' | sort > dynsyms
20195 # Extract all the text (i.e. function) symbols from the debuginfo.
20196 # (Note that we actually also accept "D" symbols, for the benefit
20197 # of platforms like PowerPC64 that use function descriptors.)
20198 nm @var{binary} --format=posix --defined-only \
20199 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
20202 # Keep all the function symbols not already in the dynamic symbol
20204 comm -13 dynsyms funcsyms > keep_symbols
20206 # Separate full debug info into debug binary.
20207 objcopy --only-keep-debug @var{binary} debug
20209 # Copy the full debuginfo, keeping only a minimal set of symbols and
20210 # removing some unnecessary sections.
20211 objcopy -S --remove-section .gdb_index --remove-section .comment \
20212 --keep-symbols=keep_symbols debug mini_debuginfo
20214 # Drop the full debug info from the original binary.
20215 strip --strip-all -R .comment @var{binary}
20217 # Inject the compressed data into the .gnu_debugdata section of the
20220 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
20224 @section Index Files Speed Up @value{GDBN}
20225 @cindex index files
20226 @cindex @samp{.gdb_index} section
20228 When @value{GDBN} finds a symbol file, it scans the symbols in the
20229 file in order to construct an internal symbol table. This lets most
20230 @value{GDBN} operations work quickly---at the cost of a delay early
20231 on. For large programs, this delay can be quite lengthy, so
20232 @value{GDBN} provides a way to build an index, which speeds up
20235 For convenience, @value{GDBN} comes with a program,
20236 @command{gdb-add-index}, which can be used to add the index to a
20237 symbol file. It takes the symbol file as its only argument:
20240 $ gdb-add-index symfile
20243 @xref{gdb-add-index}.
20245 It is also possible to do the work manually. Here is what
20246 @command{gdb-add-index} does behind the curtains.
20248 The index is stored as a section in the symbol file. @value{GDBN} can
20249 write the index to a file, then you can put it into the symbol file
20250 using @command{objcopy}.
20252 To create an index file, use the @code{save gdb-index} command:
20255 @item save gdb-index [-dwarf-5] @var{directory}
20256 @kindex save gdb-index
20257 Create index files for all symbol files currently known by
20258 @value{GDBN}. For each known @var{symbol-file}, this command by
20259 default creates it produces a single file
20260 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
20261 the @option{-dwarf-5} option, it produces 2 files:
20262 @file{@var{symbol-file}.debug_names} and
20263 @file{@var{symbol-file}.debug_str}. The files are created in the
20264 given @var{directory}.
20267 Once you have created an index file you can merge it into your symbol
20268 file, here named @file{symfile}, using @command{objcopy}:
20271 $ objcopy --add-section .gdb_index=symfile.gdb-index \
20272 --set-section-flags .gdb_index=readonly symfile symfile
20275 Or for @code{-dwarf-5}:
20278 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
20279 $ cat symfile.debug_str >>symfile.debug_str.new
20280 $ objcopy --add-section .debug_names=symfile.gdb-index \
20281 --set-section-flags .debug_names=readonly \
20282 --update-section .debug_str=symfile.debug_str.new symfile symfile
20285 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
20286 sections that have been deprecated. Usually they are deprecated because
20287 they are missing a new feature or have performance issues.
20288 To tell @value{GDBN} to use a deprecated index section anyway
20289 specify @code{set use-deprecated-index-sections on}.
20290 The default is @code{off}.
20291 This can speed up startup, but may result in some functionality being lost.
20292 @xref{Index Section Format}.
20294 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
20295 must be done before gdb reads the file. The following will not work:
20298 $ gdb -ex "set use-deprecated-index-sections on" <program>
20301 Instead you must do, for example,
20304 $ gdb -iex "set use-deprecated-index-sections on" <program>
20307 There are currently some limitation on indices. They only work when
20308 for DWARF debugging information, not stabs. And, they do not
20309 currently work for programs using Ada.
20311 @subsection Automatic symbol index cache
20313 It is possible for @value{GDBN} to automatically save a copy of this index in a
20314 cache on disk and retrieve it from there when loading the same binary in the
20315 future. This feature can be turned on with @kbd{set index-cache on}. The
20316 following commands can be used to tweak the behavior of the index cache.
20320 @item set index-cache on
20321 @itemx set index-cache off
20322 Enable or disable the use of the symbol index cache.
20324 @item set index-cache directory @var{directory}
20325 @itemx show index-cache directory
20326 Set/show the directory where index files will be saved.
20328 The default value for this directory depends on the host platform. On
20329 most systems, the index is cached in the @file{gdb} subdirectory of
20330 the directory pointed to by the @env{XDG_CACHE_HOME} environment
20331 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
20332 of your home directory. However, on some systems, the default may
20333 differ according to local convention.
20335 There is no limit on the disk space used by index cache. It is perfectly safe
20336 to delete the content of that directory to free up disk space.
20338 @item show index-cache stats
20339 Print the number of cache hits and misses since the launch of @value{GDBN}.
20343 @node Symbol Errors
20344 @section Errors Reading Symbol Files
20346 While reading a symbol file, @value{GDBN} occasionally encounters problems,
20347 such as symbol types it does not recognize, or known bugs in compiler
20348 output. By default, @value{GDBN} does not notify you of such problems, since
20349 they are relatively common and primarily of interest to people
20350 debugging compilers. If you are interested in seeing information
20351 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
20352 only one message about each such type of problem, no matter how many
20353 times the problem occurs; or you can ask @value{GDBN} to print more messages,
20354 to see how many times the problems occur, with the @code{set
20355 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
20358 The messages currently printed, and their meanings, include:
20361 @item inner block not inside outer block in @var{symbol}
20363 The symbol information shows where symbol scopes begin and end
20364 (such as at the start of a function or a block of statements). This
20365 error indicates that an inner scope block is not fully contained
20366 in its outer scope blocks.
20368 @value{GDBN} circumvents the problem by treating the inner block as if it had
20369 the same scope as the outer block. In the error message, @var{symbol}
20370 may be shown as ``@code{(don't know)}'' if the outer block is not a
20373 @item block at @var{address} out of order
20375 The symbol information for symbol scope blocks should occur in
20376 order of increasing addresses. This error indicates that it does not
20379 @value{GDBN} does not circumvent this problem, and has trouble
20380 locating symbols in the source file whose symbols it is reading. (You
20381 can often determine what source file is affected by specifying
20382 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
20385 @item bad block start address patched
20387 The symbol information for a symbol scope block has a start address
20388 smaller than the address of the preceding source line. This is known
20389 to occur in the SunOS 4.1.1 (and earlier) C compiler.
20391 @value{GDBN} circumvents the problem by treating the symbol scope block as
20392 starting on the previous source line.
20394 @item bad string table offset in symbol @var{n}
20397 Symbol number @var{n} contains a pointer into the string table which is
20398 larger than the size of the string table.
20400 @value{GDBN} circumvents the problem by considering the symbol to have the
20401 name @code{foo}, which may cause other problems if many symbols end up
20404 @item unknown symbol type @code{0x@var{nn}}
20406 The symbol information contains new data types that @value{GDBN} does
20407 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
20408 uncomprehended information, in hexadecimal.
20410 @value{GDBN} circumvents the error by ignoring this symbol information.
20411 This usually allows you to debug your program, though certain symbols
20412 are not accessible. If you encounter such a problem and feel like
20413 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
20414 on @code{complain}, then go up to the function @code{read_dbx_symtab}
20415 and examine @code{*bufp} to see the symbol.
20417 @item stub type has NULL name
20419 @value{GDBN} could not find the full definition for a struct or class.
20421 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
20422 The symbol information for a C@t{++} member function is missing some
20423 information that recent versions of the compiler should have output for
20426 @item info mismatch between compiler and debugger
20428 @value{GDBN} could not parse a type specification output by the compiler.
20433 @section GDB Data Files
20435 @cindex prefix for data files
20436 @value{GDBN} will sometimes read an auxiliary data file. These files
20437 are kept in a directory known as the @dfn{data directory}.
20439 You can set the data directory's name, and view the name @value{GDBN}
20440 is currently using.
20443 @kindex set data-directory
20444 @item set data-directory @var{directory}
20445 Set the directory which @value{GDBN} searches for auxiliary data files
20446 to @var{directory}.
20448 @kindex show data-directory
20449 @item show data-directory
20450 Show the directory @value{GDBN} searches for auxiliary data files.
20453 @cindex default data directory
20454 @cindex @samp{--with-gdb-datadir}
20455 You can set the default data directory by using the configure-time
20456 @samp{--with-gdb-datadir} option. If the data directory is inside
20457 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
20458 @samp{--exec-prefix}), then the default data directory will be updated
20459 automatically if the installed @value{GDBN} is moved to a new
20462 The data directory may also be specified with the
20463 @code{--data-directory} command line option.
20464 @xref{Mode Options}.
20467 @chapter Specifying a Debugging Target
20469 @cindex debugging target
20470 A @dfn{target} is the execution environment occupied by your program.
20472 Often, @value{GDBN} runs in the same host environment as your program;
20473 in that case, the debugging target is specified as a side effect when
20474 you use the @code{file} or @code{core} commands. When you need more
20475 flexibility---for example, running @value{GDBN} on a physically separate
20476 host, or controlling a standalone system over a serial port or a
20477 realtime system over a TCP/IP connection---you can use the @code{target}
20478 command to specify one of the target types configured for @value{GDBN}
20479 (@pxref{Target Commands, ,Commands for Managing Targets}).
20481 @cindex target architecture
20482 It is possible to build @value{GDBN} for several different @dfn{target
20483 architectures}. When @value{GDBN} is built like that, you can choose
20484 one of the available architectures with the @kbd{set architecture}
20488 @kindex set architecture
20489 @kindex show architecture
20490 @item set architecture @var{arch}
20491 This command sets the current target architecture to @var{arch}. The
20492 value of @var{arch} can be @code{"auto"}, in addition to one of the
20493 supported architectures.
20495 @item show architecture
20496 Show the current target architecture.
20498 @item set processor
20500 @kindex set processor
20501 @kindex show processor
20502 These are alias commands for, respectively, @code{set architecture}
20503 and @code{show architecture}.
20507 * Active Targets:: Active targets
20508 * Target Commands:: Commands for managing targets
20509 * Byte Order:: Choosing target byte order
20512 @node Active Targets
20513 @section Active Targets
20515 @cindex stacking targets
20516 @cindex active targets
20517 @cindex multiple targets
20519 There are multiple classes of targets such as: processes, executable files or
20520 recording sessions. Core files belong to the process class, making core file
20521 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
20522 on multiple active targets, one in each class. This allows you to (for
20523 example) start a process and inspect its activity, while still having access to
20524 the executable file after the process finishes. Or if you start process
20525 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
20526 presented a virtual layer of the recording target, while the process target
20527 remains stopped at the chronologically last point of the process execution.
20529 Use the @code{core-file} and @code{exec-file} commands to select a new core
20530 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
20531 specify as a target a process that is already running, use the @code{attach}
20532 command (@pxref{Attach, ,Debugging an Already-running Process}).
20534 @node Target Commands
20535 @section Commands for Managing Targets
20538 @item target @var{type} @var{parameters}
20539 Connects the @value{GDBN} host environment to a target machine or
20540 process. A target is typically a protocol for talking to debugging
20541 facilities. You use the argument @var{type} to specify the type or
20542 protocol of the target machine.
20544 Further @var{parameters} are interpreted by the target protocol, but
20545 typically include things like device names or host names to connect
20546 with, process numbers, and baud rates.
20548 The @code{target} command does not repeat if you press @key{RET} again
20549 after executing the command.
20551 @kindex help target
20553 Displays the names of all targets available. To display targets
20554 currently selected, use either @code{info target} or @code{info files}
20555 (@pxref{Files, ,Commands to Specify Files}).
20557 @item help target @var{name}
20558 Describe a particular target, including any parameters necessary to
20561 @kindex set gnutarget
20562 @item set gnutarget @var{args}
20563 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
20564 knows whether it is reading an @dfn{executable},
20565 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
20566 with the @code{set gnutarget} command. Unlike most @code{target} commands,
20567 with @code{gnutarget} the @code{target} refers to a program, not a machine.
20570 @emph{Warning:} To specify a file format with @code{set gnutarget},
20571 you must know the actual BFD name.
20575 @xref{Files, , Commands to Specify Files}.
20577 @kindex show gnutarget
20578 @item show gnutarget
20579 Use the @code{show gnutarget} command to display what file format
20580 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
20581 @value{GDBN} will determine the file format for each file automatically,
20582 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
20585 @cindex common targets
20586 Here are some common targets (available, or not, depending on the GDB
20591 @item target exec @var{program}
20592 @cindex executable file target
20593 An executable file. @samp{target exec @var{program}} is the same as
20594 @samp{exec-file @var{program}}.
20596 @item target core @var{filename}
20597 @cindex core dump file target
20598 A core dump file. @samp{target core @var{filename}} is the same as
20599 @samp{core-file @var{filename}}.
20601 @item target remote @var{medium}
20602 @cindex remote target
20603 A remote system connected to @value{GDBN} via a serial line or network
20604 connection. This command tells @value{GDBN} to use its own remote
20605 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
20607 For example, if you have a board connected to @file{/dev/ttya} on the
20608 machine running @value{GDBN}, you could say:
20611 target remote /dev/ttya
20614 @code{target remote} supports the @code{load} command. This is only
20615 useful if you have some other way of getting the stub to the target
20616 system, and you can put it somewhere in memory where it won't get
20617 clobbered by the download.
20619 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20620 @cindex built-in simulator target
20621 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
20629 works; however, you cannot assume that a specific memory map, device
20630 drivers, or even basic I/O is available, although some simulators do
20631 provide these. For info about any processor-specific simulator details,
20632 see the appropriate section in @ref{Embedded Processors, ,Embedded
20635 @item target native
20636 @cindex native target
20637 Setup for local/native process debugging. Useful to make the
20638 @code{run} command spawn native processes (likewise @code{attach},
20639 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
20640 (@pxref{set auto-connect-native-target}).
20644 Different targets are available on different configurations of @value{GDBN};
20645 your configuration may have more or fewer targets.
20647 Many remote targets require you to download the executable's code once
20648 you've successfully established a connection. You may wish to control
20649 various aspects of this process.
20654 @kindex set hash@r{, for remote monitors}
20655 @cindex hash mark while downloading
20656 This command controls whether a hash mark @samp{#} is displayed while
20657 downloading a file to the remote monitor. If on, a hash mark is
20658 displayed after each S-record is successfully downloaded to the
20662 @kindex show hash@r{, for remote monitors}
20663 Show the current status of displaying the hash mark.
20665 @item set debug monitor
20666 @kindex set debug monitor
20667 @cindex display remote monitor communications
20668 Enable or disable display of communications messages between
20669 @value{GDBN} and the remote monitor.
20671 @item show debug monitor
20672 @kindex show debug monitor
20673 Show the current status of displaying communications between
20674 @value{GDBN} and the remote monitor.
20679 @kindex load @var{filename} @var{offset}
20680 @item load @var{filename} @var{offset}
20682 Depending on what remote debugging facilities are configured into
20683 @value{GDBN}, the @code{load} command may be available. Where it exists, it
20684 is meant to make @var{filename} (an executable) available for debugging
20685 on the remote system---by downloading, or dynamic linking, for example.
20686 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
20687 the @code{add-symbol-file} command.
20689 If your @value{GDBN} does not have a @code{load} command, attempting to
20690 execute it gets the error message ``@code{You can't do that when your
20691 target is @dots{}}''
20693 The file is loaded at whatever address is specified in the executable.
20694 For some object file formats, you can specify the load address when you
20695 link the program; for other formats, like a.out, the object file format
20696 specifies a fixed address.
20697 @c FIXME! This would be a good place for an xref to the GNU linker doc.
20699 It is also possible to tell @value{GDBN} to load the executable file at a
20700 specific offset described by the optional argument @var{offset}. When
20701 @var{offset} is provided, @var{filename} must also be provided.
20703 Depending on the remote side capabilities, @value{GDBN} may be able to
20704 load programs into flash memory.
20706 @code{load} does not repeat if you press @key{RET} again after using it.
20711 @kindex flash-erase
20713 @anchor{flash-erase}
20715 Erases all known flash memory regions on the target.
20720 @section Choosing Target Byte Order
20722 @cindex choosing target byte order
20723 @cindex target byte order
20725 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
20726 offer the ability to run either big-endian or little-endian byte
20727 orders. Usually the executable or symbol will include a bit to
20728 designate the endian-ness, and you will not need to worry about
20729 which to use. However, you may still find it useful to adjust
20730 @value{GDBN}'s idea of processor endian-ness manually.
20734 @item set endian big
20735 Instruct @value{GDBN} to assume the target is big-endian.
20737 @item set endian little
20738 Instruct @value{GDBN} to assume the target is little-endian.
20740 @item set endian auto
20741 Instruct @value{GDBN} to use the byte order associated with the
20745 Display @value{GDBN}'s current idea of the target byte order.
20749 If the @code{set endian auto} mode is in effect and no executable has
20750 been selected, then the endianness used is the last one chosen either
20751 by one of the @code{set endian big} and @code{set endian little}
20752 commands or by inferring from the last executable used. If no
20753 endianness has been previously chosen, then the default for this mode
20754 is inferred from the target @value{GDBN} has been built for, and is
20755 @code{little} if the name of the target CPU has an @code{el} suffix
20756 and @code{big} otherwise.
20758 Note that these commands merely adjust interpretation of symbolic
20759 data on the host, and that they have absolutely no effect on the
20763 @node Remote Debugging
20764 @chapter Debugging Remote Programs
20765 @cindex remote debugging
20767 If you are trying to debug a program running on a machine that cannot run
20768 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20769 For example, you might use remote debugging on an operating system kernel,
20770 or on a small system which does not have a general purpose operating system
20771 powerful enough to run a full-featured debugger.
20773 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20774 to make this work with particular debugging targets. In addition,
20775 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20776 but not specific to any particular target system) which you can use if you
20777 write the remote stubs---the code that runs on the remote system to
20778 communicate with @value{GDBN}.
20780 Other remote targets may be available in your
20781 configuration of @value{GDBN}; use @code{help target} to list them.
20784 * Connecting:: Connecting to a remote target
20785 * File Transfer:: Sending files to a remote system
20786 * Server:: Using the gdbserver program
20787 * Remote Configuration:: Remote configuration
20788 * Remote Stub:: Implementing a remote stub
20792 @section Connecting to a Remote Target
20793 @cindex remote debugging, connecting
20794 @cindex @code{gdbserver}, connecting
20795 @cindex remote debugging, types of connections
20796 @cindex @code{gdbserver}, types of connections
20797 @cindex @code{gdbserver}, @code{target remote} mode
20798 @cindex @code{gdbserver}, @code{target extended-remote} mode
20800 This section describes how to connect to a remote target, including the
20801 types of connections and their differences, how to set up executable and
20802 symbol files on the host and target, and the commands used for
20803 connecting to and disconnecting from the remote target.
20805 @subsection Types of Remote Connections
20807 @value{GDBN} supports two types of remote connections, @code{target remote}
20808 mode and @code{target extended-remote} mode. Note that many remote targets
20809 support only @code{target remote} mode. There are several major
20810 differences between the two types of connections, enumerated here:
20814 @cindex remote debugging, detach and program exit
20815 @item Result of detach or program exit
20816 @strong{With target remote mode:} When the debugged program exits or you
20817 detach from it, @value{GDBN} disconnects from the target. When using
20818 @code{gdbserver}, @code{gdbserver} will exit.
20820 @strong{With target extended-remote mode:} When the debugged program exits or
20821 you detach from it, @value{GDBN} remains connected to the target, even
20822 though no program is running. You can rerun the program, attach to a
20823 running program, or use @code{monitor} commands specific to the target.
20825 When using @code{gdbserver} in this case, it does not exit unless it was
20826 invoked using the @option{--once} option. If the @option{--once} option
20827 was not used, you can ask @code{gdbserver} to exit using the
20828 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20830 @item Specifying the program to debug
20831 For both connection types you use the @code{file} command to specify the
20832 program on the host system. If you are using @code{gdbserver} there are
20833 some differences in how to specify the location of the program on the
20836 @strong{With target remote mode:} You must either specify the program to debug
20837 on the @code{gdbserver} command line or use the @option{--attach} option
20838 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20840 @cindex @option{--multi}, @code{gdbserver} option
20841 @strong{With target extended-remote mode:} You may specify the program to debug
20842 on the @code{gdbserver} command line, or you can load the program or attach
20843 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20845 @anchor{--multi Option in Types of Remote Connnections}
20846 You can start @code{gdbserver} without supplying an initial command to run
20847 or process ID to attach. To do this, use the @option{--multi} command line
20848 option. Then you can connect using @code{target extended-remote} and start
20849 the program you want to debug (see below for details on using the
20850 @code{run} command in this scenario). Note that the conditions under which
20851 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20852 (@code{target remote} or @code{target extended-remote}). The
20853 @option{--multi} option to @code{gdbserver} has no influence on that.
20855 @item The @code{run} command
20856 @strong{With target remote mode:} The @code{run} command is not
20857 supported. Once a connection has been established, you can use all
20858 the usual @value{GDBN} commands to examine and change data. The
20859 remote program is already running, so you can use commands like
20860 @kbd{step} and @kbd{continue}.
20862 @strong{With target extended-remote mode:} The @code{run} command is
20863 supported. The @code{run} command uses the value set by
20864 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20865 the program to run. Command line arguments are supported, except for
20866 wildcard expansion and I/O redirection (@pxref{Arguments}).
20868 If you specify the program to debug on the command line, then the
20869 @code{run} command is not required to start execution, and you can
20870 resume using commands like @kbd{step} and @kbd{continue} as with
20871 @code{target remote} mode.
20873 @anchor{Attaching in Types of Remote Connections}
20875 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20876 not supported. To attach to a running program using @code{gdbserver}, you
20877 must use the @option{--attach} option (@pxref{Running gdbserver}).
20879 @strong{With target extended-remote mode:} To attach to a running program,
20880 you may use the @code{attach} command after the connection has been
20881 established. If you are using @code{gdbserver}, you may also invoke
20882 @code{gdbserver} using the @option{--attach} option
20883 (@pxref{Running gdbserver}).
20887 @anchor{Host and target files}
20888 @subsection Host and Target Files
20889 @cindex remote debugging, symbol files
20890 @cindex symbol files, remote debugging
20892 @value{GDBN}, running on the host, needs access to symbol and debugging
20893 information for your program running on the target. This requires
20894 access to an unstripped copy of your program, and possibly any associated
20895 symbol files. Note that this section applies equally to both @code{target
20896 remote} mode and @code{target extended-remote} mode.
20898 Some remote targets (@pxref{qXfer executable filename read}, and
20899 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20900 the same connection used to communicate with @value{GDBN}. With such a
20901 target, if the remote program is unstripped, the only command you need is
20902 @code{target remote} (or @code{target extended-remote}).
20904 If the remote program is stripped, or the target does not support remote
20905 program file access, start up @value{GDBN} using the name of the local
20906 unstripped copy of your program as the first argument, or use the
20907 @code{file} command. Use @code{set sysroot} to specify the location (on
20908 the host) of target libraries (unless your @value{GDBN} was compiled with
20909 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20910 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20913 The symbol file and target libraries must exactly match the executable
20914 and libraries on the target, with one exception: the files on the host
20915 system should not be stripped, even if the files on the target system
20916 are. Mismatched or missing files will lead to confusing results
20917 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20918 files may also prevent @code{gdbserver} from debugging multi-threaded
20921 @subsection Remote Connection Commands
20922 @cindex remote connection commands
20923 @value{GDBN} can communicate with the target over a serial line, a
20924 local Unix domain socket, or
20925 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20926 each case, @value{GDBN} uses the same protocol for debugging your
20927 program; only the medium carrying the debugging packets varies. The
20928 @code{target remote} and @code{target extended-remote} commands
20929 establish a connection to the target. Both commands accept the same
20930 arguments, which indicate the medium to use:
20934 @item target remote @var{serial-device}
20935 @itemx target extended-remote @var{serial-device}
20936 @cindex serial line, @code{target remote}
20937 Use @var{serial-device} to communicate with the target. For example,
20938 to use a serial line connected to the device named @file{/dev/ttyb}:
20941 target remote /dev/ttyb
20944 If you're using a serial line, you may want to give @value{GDBN} the
20945 @samp{--baud} option, or use the @code{set serial baud} command
20946 (@pxref{Remote Configuration, set serial baud}) before the
20947 @code{target} command.
20949 @item target remote @var{local-socket}
20950 @itemx target extended-remote @var{local-socket}
20951 @cindex local socket, @code{target remote}
20952 @cindex Unix domain socket
20953 Use @var{local-socket} to communicate with the target. For example,
20954 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
20957 target remote /tmp/gdb-socket0
20960 Note that this command has the same form as the command to connect
20961 to a serial line. @value{GDBN} will automatically determine which
20962 kind of file you have specified and will make the appropriate kind
20964 This feature is not available if the host system does not support
20965 Unix domain sockets.
20967 @item target remote @code{@var{host}:@var{port}}
20968 @itemx target remote @code{@var{[host]}:@var{port}}
20969 @itemx target remote @code{tcp:@var{host}:@var{port}}
20970 @itemx target remote @code{tcp:@var{[host]}:@var{port}}
20971 @itemx target remote @code{tcp4:@var{host}:@var{port}}
20972 @itemx target remote @code{tcp6:@var{host}:@var{port}}
20973 @itemx target remote @code{tcp6:@var{[host]}:@var{port}}
20974 @itemx target extended-remote @code{@var{host}:@var{port}}
20975 @itemx target extended-remote @code{@var{[host]}:@var{port}}
20976 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
20977 @itemx target extended-remote @code{tcp:@var{[host]}:@var{port}}
20978 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
20979 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
20980 @itemx target extended-remote @code{tcp6:@var{[host]}:@var{port}}
20981 @cindex @acronym{TCP} port, @code{target remote}
20982 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
20983 The @var{host} may be either a host name, a numeric @acronym{IPv4}
20984 address, or a numeric @acronym{IPv6} address (with or without the
20985 square brackets to separate the address from the port); @var{port}
20986 must be a decimal number. The @var{host} could be the target machine
20987 itself, if it is directly connected to the net, or it might be a
20988 terminal server which in turn has a serial line to the target.
20990 For example, to connect to port 2828 on a terminal server named
20994 target remote manyfarms:2828
20997 To connect to port 2828 on a terminal server whose address is
20998 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
20999 square bracket syntax:
21002 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
21006 or explicitly specify the @acronym{IPv6} protocol:
21009 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
21012 This last example may be confusing to the reader, because there is no
21013 visible separation between the hostname and the port number.
21014 Therefore, we recommend the user to provide @acronym{IPv6} addresses
21015 using square brackets for clarity. However, it is important to
21016 mention that for @value{GDBN} there is no ambiguity: the number after
21017 the last colon is considered to be the port number.
21019 If your remote target is actually running on the same machine as your
21020 debugger session (e.g.@: a simulator for your target running on the
21021 same host), you can omit the hostname. For example, to connect to
21022 port 1234 on your local machine:
21025 target remote :1234
21029 Note that the colon is still required here.
21031 @item target remote @code{udp:@var{host}:@var{port}}
21032 @itemx target remote @code{udp:@var{[host]}:@var{port}}
21033 @itemx target remote @code{udp4:@var{host}:@var{port}}
21034 @itemx target remote @code{udp6:@var{[host]}:@var{port}}
21035 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21036 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21037 @itemx target extended-remote @code{udp:@var{[host]}:@var{port}}
21038 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
21039 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
21040 @itemx target extended-remote @code{udp6:@var{[host]}:@var{port}}
21041 @cindex @acronym{UDP} port, @code{target remote}
21042 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
21043 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
21046 target remote udp:manyfarms:2828
21049 When using a @acronym{UDP} connection for remote debugging, you should
21050 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
21051 can silently drop packets on busy or unreliable networks, which will
21052 cause havoc with your debugging session.
21054 @item target remote | @var{command}
21055 @itemx target extended-remote | @var{command}
21056 @cindex pipe, @code{target remote} to
21057 Run @var{command} in the background and communicate with it using a
21058 pipe. The @var{command} is a shell command, to be parsed and expanded
21059 by the system's command shell, @code{/bin/sh}; it should expect remote
21060 protocol packets on its standard input, and send replies on its
21061 standard output. You could use this to run a stand-alone simulator
21062 that speaks the remote debugging protocol, to make net connections
21063 using programs like @code{ssh}, or for other similar tricks.
21065 If @var{command} closes its standard output (perhaps by exiting),
21066 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
21067 program has already exited, this will have no effect.)
21071 @cindex interrupting remote programs
21072 @cindex remote programs, interrupting
21073 Whenever @value{GDBN} is waiting for the remote program, if you type the
21074 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
21075 program. This may or may not succeed, depending in part on the hardware
21076 and the serial drivers the remote system uses. If you type the
21077 interrupt character once again, @value{GDBN} displays this prompt:
21080 Interrupted while waiting for the program.
21081 Give up (and stop debugging it)? (y or n)
21084 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
21085 the remote debugging session. (If you decide you want to try again later,
21086 you can use @kbd{target remote} again to connect once more.) If you type
21087 @kbd{n}, @value{GDBN} goes back to waiting.
21089 In @code{target extended-remote} mode, typing @kbd{n} will leave
21090 @value{GDBN} connected to the target.
21093 @kindex detach (remote)
21095 When you have finished debugging the remote program, you can use the
21096 @code{detach} command to release it from @value{GDBN} control.
21097 Detaching from the target normally resumes its execution, but the results
21098 will depend on your particular remote stub. After the @code{detach}
21099 command in @code{target remote} mode, @value{GDBN} is free to connect to
21100 another target. In @code{target extended-remote} mode, @value{GDBN} is
21101 still connected to the target.
21105 The @code{disconnect} command closes the connection to the target, and
21106 the target is generally not resumed. It will wait for @value{GDBN}
21107 (this instance or another one) to connect and continue debugging. After
21108 the @code{disconnect} command, @value{GDBN} is again free to connect to
21111 @cindex send command to remote monitor
21112 @cindex extend @value{GDBN} for remote targets
21113 @cindex add new commands for external monitor
21115 @item monitor @var{cmd}
21116 This command allows you to send arbitrary commands directly to the
21117 remote monitor. Since @value{GDBN} doesn't care about the commands it
21118 sends like this, this command is the way to extend @value{GDBN}---you
21119 can add new commands that only the external monitor will understand
21123 @node File Transfer
21124 @section Sending files to a remote system
21125 @cindex remote target, file transfer
21126 @cindex file transfer
21127 @cindex sending files to remote systems
21129 Some remote targets offer the ability to transfer files over the same
21130 connection used to communicate with @value{GDBN}. This is convenient
21131 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
21132 running @code{gdbserver} over a network interface. For other targets,
21133 e.g.@: embedded devices with only a single serial port, this may be
21134 the only way to upload or download files.
21136 Not all remote targets support these commands.
21140 @item remote put @var{hostfile} @var{targetfile}
21141 Copy file @var{hostfile} from the host system (the machine running
21142 @value{GDBN}) to @var{targetfile} on the target system.
21145 @item remote get @var{targetfile} @var{hostfile}
21146 Copy file @var{targetfile} from the target system to @var{hostfile}
21147 on the host system.
21149 @kindex remote delete
21150 @item remote delete @var{targetfile}
21151 Delete @var{targetfile} from the target system.
21156 @section Using the @code{gdbserver} Program
21159 @cindex remote connection without stubs
21160 @code{gdbserver} is a control program for Unix-like systems, which
21161 allows you to connect your program with a remote @value{GDBN} via
21162 @code{target remote} or @code{target extended-remote}---but without
21163 linking in the usual debugging stub.
21165 @code{gdbserver} is not a complete replacement for the debugging stubs,
21166 because it requires essentially the same operating-system facilities
21167 that @value{GDBN} itself does. In fact, a system that can run
21168 @code{gdbserver} to connect to a remote @value{GDBN} could also run
21169 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
21170 because it is a much smaller program than @value{GDBN} itself. It is
21171 also easier to port than all of @value{GDBN}, so you may be able to get
21172 started more quickly on a new system by using @code{gdbserver}.
21173 Finally, if you develop code for real-time systems, you may find that
21174 the tradeoffs involved in real-time operation make it more convenient to
21175 do as much development work as possible on another system, for example
21176 by cross-compiling. You can use @code{gdbserver} to make a similar
21177 choice for debugging.
21179 @value{GDBN} and @code{gdbserver} communicate via either a serial line
21180 or a TCP connection, using the standard @value{GDBN} remote serial
21184 @emph{Warning:} @code{gdbserver} does not have any built-in security.
21185 Do not run @code{gdbserver} connected to any public network; a
21186 @value{GDBN} connection to @code{gdbserver} provides access to the
21187 target system with the same privileges as the user running
21191 @anchor{Running gdbserver}
21192 @subsection Running @code{gdbserver}
21193 @cindex arguments, to @code{gdbserver}
21194 @cindex @code{gdbserver}, command-line arguments
21196 Run @code{gdbserver} on the target system. You need a copy of the
21197 program you want to debug, including any libraries it requires.
21198 @code{gdbserver} does not need your program's symbol table, so you can
21199 strip the program if necessary to save space. @value{GDBN} on the host
21200 system does all the symbol handling.
21202 To use the server, you must tell it how to communicate with @value{GDBN};
21203 the name of your program; and the arguments for your program. The usual
21207 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
21210 @var{comm} is either a device name (to use a serial line), or a TCP
21211 hostname and portnumber, or @code{-} or @code{stdio} to use
21212 stdin/stdout of @code{gdbserver}.
21213 For example, to debug Emacs with the argument
21214 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
21218 target> gdbserver /dev/com1 emacs foo.txt
21221 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
21224 To use a TCP connection instead of a serial line:
21227 target> gdbserver host:2345 emacs foo.txt
21230 The only difference from the previous example is the first argument,
21231 specifying that you are communicating with the host @value{GDBN} via
21232 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
21233 expect a TCP connection from machine @samp{host} to local TCP port 2345.
21234 (Currently, the @samp{host} part is ignored.) You can choose any number
21235 you want for the port number as long as it does not conflict with any
21236 TCP ports already in use on the target system (for example, @code{23} is
21237 reserved for @code{telnet}).@footnote{If you choose a port number that
21238 conflicts with another service, @code{gdbserver} prints an error message
21239 and exits.} You must use the same port number with the host @value{GDBN}
21240 @code{target remote} command.
21242 The @code{stdio} connection is useful when starting @code{gdbserver}
21246 (gdb) target remote | ssh -T hostname gdbserver - hello
21249 The @samp{-T} option to ssh is provided because we don't need a remote pty,
21250 and we don't want escape-character handling. Ssh does this by default when
21251 a command is provided, the flag is provided to make it explicit.
21252 You could elide it if you want to.
21254 Programs started with stdio-connected gdbserver have @file{/dev/null} for
21255 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
21256 display through a pipe connected to gdbserver.
21257 Both @code{stdout} and @code{stderr} use the same pipe.
21259 @anchor{Attaching to a program}
21260 @subsubsection Attaching to a Running Program
21261 @cindex attach to a program, @code{gdbserver}
21262 @cindex @option{--attach}, @code{gdbserver} option
21264 On some targets, @code{gdbserver} can also attach to running programs.
21265 This is accomplished via the @code{--attach} argument. The syntax is:
21268 target> gdbserver --attach @var{comm} @var{pid}
21271 @var{pid} is the process ID of a currently running process. It isn't
21272 necessary to point @code{gdbserver} at a binary for the running process.
21274 In @code{target extended-remote} mode, you can also attach using the
21275 @value{GDBN} attach command
21276 (@pxref{Attaching in Types of Remote Connections}).
21279 You can debug processes by name instead of process ID if your target has the
21280 @code{pidof} utility:
21283 target> gdbserver --attach @var{comm} `pidof @var{program}`
21286 In case more than one copy of @var{program} is running, or @var{program}
21287 has multiple threads, most versions of @code{pidof} support the
21288 @code{-s} option to only return the first process ID.
21290 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
21292 This section applies only when @code{gdbserver} is run to listen on a TCP
21295 @code{gdbserver} normally terminates after all of its debugged processes have
21296 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
21297 extended-remote}, @code{gdbserver} stays running even with no processes left.
21298 @value{GDBN} normally terminates the spawned debugged process on its exit,
21299 which normally also terminates @code{gdbserver} in the @kbd{target remote}
21300 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
21301 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
21302 stays running even in the @kbd{target remote} mode.
21304 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
21305 Such reconnecting is useful for features like @ref{disconnected tracing}. For
21306 completeness, at most one @value{GDBN} can be connected at a time.
21308 @cindex @option{--once}, @code{gdbserver} option
21309 By default, @code{gdbserver} keeps the listening TCP port open, so that
21310 subsequent connections are possible. However, if you start @code{gdbserver}
21311 with the @option{--once} option, it will stop listening for any further
21312 connection attempts after connecting to the first @value{GDBN} session. This
21313 means no further connections to @code{gdbserver} will be possible after the
21314 first one. It also means @code{gdbserver} will terminate after the first
21315 connection with remote @value{GDBN} has closed, even for unexpectedly closed
21316 connections and even in the @kbd{target extended-remote} mode. The
21317 @option{--once} option allows reusing the same port number for connecting to
21318 multiple instances of @code{gdbserver} running on the same host, since each
21319 instance closes its port after the first connection.
21321 @anchor{Other Command-Line Arguments for gdbserver}
21322 @subsubsection Other Command-Line Arguments for @code{gdbserver}
21324 You can use the @option{--multi} option to start @code{gdbserver} without
21325 specifying a program to debug or a process to attach to. Then you can
21326 attach in @code{target extended-remote} mode and run or attach to a
21327 program. For more information,
21328 @pxref{--multi Option in Types of Remote Connnections}.
21330 @cindex @option{--debug}, @code{gdbserver} option
21331 The @option{--debug} option tells @code{gdbserver} to display extra
21332 status information about the debugging process.
21333 @cindex @option{--remote-debug}, @code{gdbserver} option
21334 The @option{--remote-debug} option tells @code{gdbserver} to display
21335 remote protocol debug output. These options are intended for
21336 @code{gdbserver} development and for bug reports to the developers.
21338 @cindex @option{--debug-format}, @code{gdbserver} option
21339 The @option{--debug-format=option1[,option2,...]} option tells
21340 @code{gdbserver} to include additional information in each output.
21341 Possible options are:
21345 Turn off all extra information in debugging output.
21347 Turn on all extra information in debugging output.
21349 Include a timestamp in each line of debugging output.
21352 Options are processed in order. Thus, for example, if @option{none}
21353 appears last then no additional information is added to debugging output.
21355 @cindex @option{--wrapper}, @code{gdbserver} option
21356 The @option{--wrapper} option specifies a wrapper to launch programs
21357 for debugging. The option should be followed by the name of the
21358 wrapper, then any command-line arguments to pass to the wrapper, then
21359 @kbd{--} indicating the end of the wrapper arguments.
21361 @code{gdbserver} runs the specified wrapper program with a combined
21362 command line including the wrapper arguments, then the name of the
21363 program to debug, then any arguments to the program. The wrapper
21364 runs until it executes your program, and then @value{GDBN} gains control.
21366 You can use any program that eventually calls @code{execve} with
21367 its arguments as a wrapper. Several standard Unix utilities do
21368 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
21369 with @code{exec "$@@"} will also work.
21371 For example, you can use @code{env} to pass an environment variable to
21372 the debugged program, without setting the variable in @code{gdbserver}'s
21376 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
21379 @cindex @option{--selftest}
21380 The @option{--selftest} option runs the self tests in @code{gdbserver}:
21383 $ gdbserver --selftest
21384 Ran 2 unit tests, 0 failed
21387 These tests are disabled in release.
21388 @subsection Connecting to @code{gdbserver}
21390 The basic procedure for connecting to the remote target is:
21394 Run @value{GDBN} on the host system.
21397 Make sure you have the necessary symbol files
21398 (@pxref{Host and target files}).
21399 Load symbols for your application using the @code{file} command before you
21400 connect. Use @code{set sysroot} to locate target libraries (unless your
21401 @value{GDBN} was compiled with the correct sysroot using
21402 @code{--with-sysroot}).
21405 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
21406 For TCP connections, you must start up @code{gdbserver} prior to using
21407 the @code{target} command. Otherwise you may get an error whose
21408 text depends on the host system, but which usually looks something like
21409 @samp{Connection refused}. Don't use the @code{load}
21410 command in @value{GDBN} when using @code{target remote} mode, since the
21411 program is already on the target.
21415 @anchor{Monitor Commands for gdbserver}
21416 @subsection Monitor Commands for @code{gdbserver}
21417 @cindex monitor commands, for @code{gdbserver}
21419 During a @value{GDBN} session using @code{gdbserver}, you can use the
21420 @code{monitor} command to send special requests to @code{gdbserver}.
21421 Here are the available commands.
21425 List the available monitor commands.
21427 @item monitor set debug 0
21428 @itemx monitor set debug 1
21429 Disable or enable general debugging messages.
21431 @item monitor set remote-debug 0
21432 @itemx monitor set remote-debug 1
21433 Disable or enable specific debugging messages associated with the remote
21434 protocol (@pxref{Remote Protocol}).
21436 @item monitor set debug-format option1@r{[},option2,...@r{]}
21437 Specify additional text to add to debugging messages.
21438 Possible options are:
21442 Turn off all extra information in debugging output.
21444 Turn on all extra information in debugging output.
21446 Include a timestamp in each line of debugging output.
21449 Options are processed in order. Thus, for example, if @option{none}
21450 appears last then no additional information is added to debugging output.
21452 @item monitor set libthread-db-search-path [PATH]
21453 @cindex gdbserver, search path for @code{libthread_db}
21454 When this command is issued, @var{path} is a colon-separated list of
21455 directories to search for @code{libthread_db} (@pxref{Threads,,set
21456 libthread-db-search-path}). If you omit @var{path},
21457 @samp{libthread-db-search-path} will be reset to its default value.
21459 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
21460 not supported in @code{gdbserver}.
21463 Tell gdbserver to exit immediately. This command should be followed by
21464 @code{disconnect} to close the debugging session. @code{gdbserver} will
21465 detach from any attached processes and kill any processes it created.
21466 Use @code{monitor exit} to terminate @code{gdbserver} at the end
21467 of a multi-process mode debug session.
21471 @subsection Tracepoints support in @code{gdbserver}
21472 @cindex tracepoints support in @code{gdbserver}
21474 On some targets, @code{gdbserver} supports tracepoints, fast
21475 tracepoints and static tracepoints.
21477 For fast or static tracepoints to work, a special library called the
21478 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
21479 This library is built and distributed as an integral part of
21480 @code{gdbserver}. In addition, support for static tracepoints
21481 requires building the in-process agent library with static tracepoints
21482 support. At present, the UST (LTTng Userspace Tracer,
21483 @url{http://lttng.org/ust}) tracing engine is supported. This support
21484 is automatically available if UST development headers are found in the
21485 standard include path when @code{gdbserver} is built, or if
21486 @code{gdbserver} was explicitly configured using @option{--with-ust}
21487 to point at such headers. You can explicitly disable the support
21488 using @option{--with-ust=no}.
21490 There are several ways to load the in-process agent in your program:
21493 @item Specifying it as dependency at link time
21495 You can link your program dynamically with the in-process agent
21496 library. On most systems, this is accomplished by adding
21497 @code{-linproctrace} to the link command.
21499 @item Using the system's preloading mechanisms
21501 You can force loading the in-process agent at startup time by using
21502 your system's support for preloading shared libraries. Many Unixes
21503 support the concept of preloading user defined libraries. In most
21504 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
21505 in the environment. See also the description of @code{gdbserver}'s
21506 @option{--wrapper} command line option.
21508 @item Using @value{GDBN} to force loading the agent at run time
21510 On some systems, you can force the inferior to load a shared library,
21511 by calling a dynamic loader function in the inferior that takes care
21512 of dynamically looking up and loading a shared library. On most Unix
21513 systems, the function is @code{dlopen}. You'll use the @code{call}
21514 command for that. For example:
21517 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
21520 Note that on most Unix systems, for the @code{dlopen} function to be
21521 available, the program needs to be linked with @code{-ldl}.
21524 On systems that have a userspace dynamic loader, like most Unix
21525 systems, when you connect to @code{gdbserver} using @code{target
21526 remote}, you'll find that the program is stopped at the dynamic
21527 loader's entry point, and no shared library has been loaded in the
21528 program's address space yet, including the in-process agent. In that
21529 case, before being able to use any of the fast or static tracepoints
21530 features, you need to let the loader run and load the shared
21531 libraries. The simplest way to do that is to run the program to the
21532 main procedure. E.g., if debugging a C or C@t{++} program, start
21533 @code{gdbserver} like so:
21536 $ gdbserver :9999 myprogram
21539 Start GDB and connect to @code{gdbserver} like so, and run to main:
21543 (@value{GDBP}) target remote myhost:9999
21544 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
21545 (@value{GDBP}) b main
21546 (@value{GDBP}) continue
21549 The in-process tracing agent library should now be loaded into the
21550 process; you can confirm it with the @code{info sharedlibrary}
21551 command, which will list @file{libinproctrace.so} as loaded in the
21552 process. You are now ready to install fast tracepoints, list static
21553 tracepoint markers, probe static tracepoints markers, and start
21556 @node Remote Configuration
21557 @section Remote Configuration
21560 @kindex show remote
21561 This section documents the configuration options available when
21562 debugging remote programs. For the options related to the File I/O
21563 extensions of the remote protocol, see @ref{system,
21564 system-call-allowed}.
21567 @item set remoteaddresssize @var{bits}
21568 @cindex address size for remote targets
21569 @cindex bits in remote address
21570 Set the maximum size of address in a memory packet to the specified
21571 number of bits. @value{GDBN} will mask off the address bits above
21572 that number, when it passes addresses to the remote target. The
21573 default value is the number of bits in the target's address.
21575 @item show remoteaddresssize
21576 Show the current value of remote address size in bits.
21578 @item set serial baud @var{n}
21579 @cindex baud rate for remote targets
21580 Set the baud rate for the remote serial I/O to @var{n} baud. The
21581 value is used to set the speed of the serial port used for debugging
21584 @item show serial baud
21585 Show the current speed of the remote connection.
21587 @item set serial parity @var{parity}
21588 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
21589 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
21591 @item show serial parity
21592 Show the current parity of the serial port.
21594 @item set remotebreak
21595 @cindex interrupt remote programs
21596 @cindex BREAK signal instead of Ctrl-C
21597 @anchor{set remotebreak}
21598 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
21599 when you type @kbd{Ctrl-c} to interrupt the program running
21600 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
21601 character instead. The default is off, since most remote systems
21602 expect to see @samp{Ctrl-C} as the interrupt signal.
21604 @item show remotebreak
21605 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
21606 interrupt the remote program.
21608 @item set remoteflow on
21609 @itemx set remoteflow off
21610 @kindex set remoteflow
21611 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
21612 on the serial port used to communicate to the remote target.
21614 @item show remoteflow
21615 @kindex show remoteflow
21616 Show the current setting of hardware flow control.
21618 @item set remotelogbase @var{base}
21619 Set the base (a.k.a.@: radix) of logging serial protocol
21620 communications to @var{base}. Supported values of @var{base} are:
21621 @code{ascii}, @code{octal}, and @code{hex}. The default is
21624 @item show remotelogbase
21625 Show the current setting of the radix for logging remote serial
21628 @item set remotelogfile @var{file}
21629 @cindex record serial communications on file
21630 Record remote serial communications on the named @var{file}. The
21631 default is not to record at all.
21633 @item show remotelogfile
21634 Show the current setting of the file name on which to record the
21635 serial communications.
21637 @item set remotetimeout @var{num}
21638 @cindex timeout for serial communications
21639 @cindex remote timeout
21640 Set the timeout limit to wait for the remote target to respond to
21641 @var{num} seconds. The default is 2 seconds.
21643 @item show remotetimeout
21644 Show the current number of seconds to wait for the remote target
21647 @cindex limit hardware breakpoints and watchpoints
21648 @cindex remote target, limit break- and watchpoints
21649 @anchor{set remote hardware-watchpoint-limit}
21650 @anchor{set remote hardware-breakpoint-limit}
21651 @item set remote hardware-watchpoint-limit @var{limit}
21652 @itemx set remote hardware-breakpoint-limit @var{limit}
21653 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
21654 or breakpoints. The @var{limit} can be set to 0 to disable hardware
21655 watchpoints or breakpoints, and @code{unlimited} for unlimited
21656 watchpoints or breakpoints.
21658 @item show remote hardware-watchpoint-limit
21659 @itemx show remote hardware-breakpoint-limit
21660 Show the current limit for the number of hardware watchpoints or
21661 breakpoints that @value{GDBN} can use.
21663 @cindex limit hardware watchpoints length
21664 @cindex remote target, limit watchpoints length
21665 @anchor{set remote hardware-watchpoint-length-limit}
21666 @item set remote hardware-watchpoint-length-limit @var{limit}
21667 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
21668 length of a remote hardware watchpoint. A @var{limit} of 0 disables
21669 hardware watchpoints and @code{unlimited} allows watchpoints of any
21672 @item show remote hardware-watchpoint-length-limit
21673 Show the current limit (in bytes) of the maximum length of
21674 a remote hardware watchpoint.
21676 @item set remote exec-file @var{filename}
21677 @itemx show remote exec-file
21678 @anchor{set remote exec-file}
21679 @cindex executable file, for remote target
21680 Select the file used for @code{run} with @code{target
21681 extended-remote}. This should be set to a filename valid on the
21682 target system. If it is not set, the target will use a default
21683 filename (e.g.@: the last program run).
21685 @item set remote interrupt-sequence
21686 @cindex interrupt remote programs
21687 @cindex select Ctrl-C, BREAK or BREAK-g
21688 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
21689 @samp{BREAK-g} as the
21690 sequence to the remote target in order to interrupt the execution.
21691 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
21692 is high level of serial line for some certain time.
21693 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
21694 It is @code{BREAK} signal followed by character @code{g}.
21696 @item show interrupt-sequence
21697 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
21698 is sent by @value{GDBN} to interrupt the remote program.
21699 @code{BREAK-g} is BREAK signal followed by @code{g} and
21700 also known as Magic SysRq g.
21702 @item set remote interrupt-on-connect
21703 @cindex send interrupt-sequence on start
21704 Specify whether interrupt-sequence is sent to remote target when
21705 @value{GDBN} connects to it. This is mostly needed when you debug
21706 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
21707 which is known as Magic SysRq g in order to connect @value{GDBN}.
21709 @item show interrupt-on-connect
21710 Show whether interrupt-sequence is sent
21711 to remote target when @value{GDBN} connects to it.
21715 @item set tcp auto-retry on
21716 @cindex auto-retry, for remote TCP target
21717 Enable auto-retry for remote TCP connections. This is useful if the remote
21718 debugging agent is launched in parallel with @value{GDBN}; there is a race
21719 condition because the agent may not become ready to accept the connection
21720 before @value{GDBN} attempts to connect. When auto-retry is
21721 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
21722 to establish the connection using the timeout specified by
21723 @code{set tcp connect-timeout}.
21725 @item set tcp auto-retry off
21726 Do not auto-retry failed TCP connections.
21728 @item show tcp auto-retry
21729 Show the current auto-retry setting.
21731 @item set tcp connect-timeout @var{seconds}
21732 @itemx set tcp connect-timeout unlimited
21733 @cindex connection timeout, for remote TCP target
21734 @cindex timeout, for remote target connection
21735 Set the timeout for establishing a TCP connection to the remote target to
21736 @var{seconds}. The timeout affects both polling to retry failed connections
21737 (enabled by @code{set tcp auto-retry on}) and waiting for connections
21738 that are merely slow to complete, and represents an approximate cumulative
21739 value. If @var{seconds} is @code{unlimited}, there is no timeout and
21740 @value{GDBN} will keep attempting to establish a connection forever,
21741 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
21743 @item show tcp connect-timeout
21744 Show the current connection timeout setting.
21747 @cindex remote packets, enabling and disabling
21748 The @value{GDBN} remote protocol autodetects the packets supported by
21749 your debugging stub. If you need to override the autodetection, you
21750 can use these commands to enable or disable individual packets. Each
21751 packet can be set to @samp{on} (the remote target supports this
21752 packet), @samp{off} (the remote target does not support this packet),
21753 or @samp{auto} (detect remote target support for this packet). They
21754 all default to @samp{auto}. For more information about each packet,
21755 see @ref{Remote Protocol}.
21757 During normal use, you should not have to use any of these commands.
21758 If you do, that may be a bug in your remote debugging stub, or a bug
21759 in @value{GDBN}. You may want to report the problem to the
21760 @value{GDBN} developers.
21762 For each packet @var{name}, the command to enable or disable the
21763 packet is @code{set remote @var{name}-packet}. The available settings
21766 @multitable @columnfractions 0.28 0.32 0.25
21769 @tab Related Features
21771 @item @code{fetch-register}
21773 @tab @code{info registers}
21775 @item @code{set-register}
21779 @item @code{binary-download}
21781 @tab @code{load}, @code{set}
21783 @item @code{read-aux-vector}
21784 @tab @code{qXfer:auxv:read}
21785 @tab @code{info auxv}
21787 @item @code{symbol-lookup}
21788 @tab @code{qSymbol}
21789 @tab Detecting multiple threads
21791 @item @code{attach}
21792 @tab @code{vAttach}
21795 @item @code{verbose-resume}
21797 @tab Stepping or resuming multiple threads
21803 @item @code{software-breakpoint}
21807 @item @code{hardware-breakpoint}
21811 @item @code{write-watchpoint}
21815 @item @code{read-watchpoint}
21819 @item @code{access-watchpoint}
21823 @item @code{pid-to-exec-file}
21824 @tab @code{qXfer:exec-file:read}
21825 @tab @code{attach}, @code{run}
21827 @item @code{target-features}
21828 @tab @code{qXfer:features:read}
21829 @tab @code{set architecture}
21831 @item @code{library-info}
21832 @tab @code{qXfer:libraries:read}
21833 @tab @code{info sharedlibrary}
21835 @item @code{memory-map}
21836 @tab @code{qXfer:memory-map:read}
21837 @tab @code{info mem}
21839 @item @code{read-sdata-object}
21840 @tab @code{qXfer:sdata:read}
21841 @tab @code{print $_sdata}
21843 @item @code{read-spu-object}
21844 @tab @code{qXfer:spu:read}
21845 @tab @code{info spu}
21847 @item @code{write-spu-object}
21848 @tab @code{qXfer:spu:write}
21849 @tab @code{info spu}
21851 @item @code{read-siginfo-object}
21852 @tab @code{qXfer:siginfo:read}
21853 @tab @code{print $_siginfo}
21855 @item @code{write-siginfo-object}
21856 @tab @code{qXfer:siginfo:write}
21857 @tab @code{set $_siginfo}
21859 @item @code{threads}
21860 @tab @code{qXfer:threads:read}
21861 @tab @code{info threads}
21863 @item @code{get-thread-local-@*storage-address}
21864 @tab @code{qGetTLSAddr}
21865 @tab Displaying @code{__thread} variables
21867 @item @code{get-thread-information-block-address}
21868 @tab @code{qGetTIBAddr}
21869 @tab Display MS-Windows Thread Information Block.
21871 @item @code{search-memory}
21872 @tab @code{qSearch:memory}
21875 @item @code{supported-packets}
21876 @tab @code{qSupported}
21877 @tab Remote communications parameters
21879 @item @code{catch-syscalls}
21880 @tab @code{QCatchSyscalls}
21881 @tab @code{catch syscall}
21883 @item @code{pass-signals}
21884 @tab @code{QPassSignals}
21885 @tab @code{handle @var{signal}}
21887 @item @code{program-signals}
21888 @tab @code{QProgramSignals}
21889 @tab @code{handle @var{signal}}
21891 @item @code{hostio-close-packet}
21892 @tab @code{vFile:close}
21893 @tab @code{remote get}, @code{remote put}
21895 @item @code{hostio-open-packet}
21896 @tab @code{vFile:open}
21897 @tab @code{remote get}, @code{remote put}
21899 @item @code{hostio-pread-packet}
21900 @tab @code{vFile:pread}
21901 @tab @code{remote get}, @code{remote put}
21903 @item @code{hostio-pwrite-packet}
21904 @tab @code{vFile:pwrite}
21905 @tab @code{remote get}, @code{remote put}
21907 @item @code{hostio-unlink-packet}
21908 @tab @code{vFile:unlink}
21909 @tab @code{remote delete}
21911 @item @code{hostio-readlink-packet}
21912 @tab @code{vFile:readlink}
21915 @item @code{hostio-fstat-packet}
21916 @tab @code{vFile:fstat}
21919 @item @code{hostio-setfs-packet}
21920 @tab @code{vFile:setfs}
21923 @item @code{noack-packet}
21924 @tab @code{QStartNoAckMode}
21925 @tab Packet acknowledgment
21927 @item @code{osdata}
21928 @tab @code{qXfer:osdata:read}
21929 @tab @code{info os}
21931 @item @code{query-attached}
21932 @tab @code{qAttached}
21933 @tab Querying remote process attach state.
21935 @item @code{trace-buffer-size}
21936 @tab @code{QTBuffer:size}
21937 @tab @code{set trace-buffer-size}
21939 @item @code{trace-status}
21940 @tab @code{qTStatus}
21941 @tab @code{tstatus}
21943 @item @code{traceframe-info}
21944 @tab @code{qXfer:traceframe-info:read}
21945 @tab Traceframe info
21947 @item @code{install-in-trace}
21948 @tab @code{InstallInTrace}
21949 @tab Install tracepoint in tracing
21951 @item @code{disable-randomization}
21952 @tab @code{QDisableRandomization}
21953 @tab @code{set disable-randomization}
21955 @item @code{startup-with-shell}
21956 @tab @code{QStartupWithShell}
21957 @tab @code{set startup-with-shell}
21959 @item @code{environment-hex-encoded}
21960 @tab @code{QEnvironmentHexEncoded}
21961 @tab @code{set environment}
21963 @item @code{environment-unset}
21964 @tab @code{QEnvironmentUnset}
21965 @tab @code{unset environment}
21967 @item @code{environment-reset}
21968 @tab @code{QEnvironmentReset}
21969 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
21971 @item @code{set-working-dir}
21972 @tab @code{QSetWorkingDir}
21973 @tab @code{set cwd}
21975 @item @code{conditional-breakpoints-packet}
21976 @tab @code{Z0 and Z1}
21977 @tab @code{Support for target-side breakpoint condition evaluation}
21979 @item @code{multiprocess-extensions}
21980 @tab @code{multiprocess extensions}
21981 @tab Debug multiple processes and remote process PID awareness
21983 @item @code{swbreak-feature}
21984 @tab @code{swbreak stop reason}
21987 @item @code{hwbreak-feature}
21988 @tab @code{hwbreak stop reason}
21991 @item @code{fork-event-feature}
21992 @tab @code{fork stop reason}
21995 @item @code{vfork-event-feature}
21996 @tab @code{vfork stop reason}
21999 @item @code{exec-event-feature}
22000 @tab @code{exec stop reason}
22003 @item @code{thread-events}
22004 @tab @code{QThreadEvents}
22005 @tab Tracking thread lifetime.
22007 @item @code{no-resumed-stop-reply}
22008 @tab @code{no resumed thread left stop reply}
22009 @tab Tracking thread lifetime.
22014 @section Implementing a Remote Stub
22016 @cindex debugging stub, example
22017 @cindex remote stub, example
22018 @cindex stub example, remote debugging
22019 The stub files provided with @value{GDBN} implement the target side of the
22020 communication protocol, and the @value{GDBN} side is implemented in the
22021 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
22022 these subroutines to communicate, and ignore the details. (If you're
22023 implementing your own stub file, you can still ignore the details: start
22024 with one of the existing stub files. @file{sparc-stub.c} is the best
22025 organized, and therefore the easiest to read.)
22027 @cindex remote serial debugging, overview
22028 To debug a program running on another machine (the debugging
22029 @dfn{target} machine), you must first arrange for all the usual
22030 prerequisites for the program to run by itself. For example, for a C
22035 A startup routine to set up the C runtime environment; these usually
22036 have a name like @file{crt0}. The startup routine may be supplied by
22037 your hardware supplier, or you may have to write your own.
22040 A C subroutine library to support your program's
22041 subroutine calls, notably managing input and output.
22044 A way of getting your program to the other machine---for example, a
22045 download program. These are often supplied by the hardware
22046 manufacturer, but you may have to write your own from hardware
22050 The next step is to arrange for your program to use a serial port to
22051 communicate with the machine where @value{GDBN} is running (the @dfn{host}
22052 machine). In general terms, the scheme looks like this:
22056 @value{GDBN} already understands how to use this protocol; when everything
22057 else is set up, you can simply use the @samp{target remote} command
22058 (@pxref{Targets,,Specifying a Debugging Target}).
22060 @item On the target,
22061 you must link with your program a few special-purpose subroutines that
22062 implement the @value{GDBN} remote serial protocol. The file containing these
22063 subroutines is called a @dfn{debugging stub}.
22065 On certain remote targets, you can use an auxiliary program
22066 @code{gdbserver} instead of linking a stub into your program.
22067 @xref{Server,,Using the @code{gdbserver} Program}, for details.
22070 The debugging stub is specific to the architecture of the remote
22071 machine; for example, use @file{sparc-stub.c} to debug programs on
22074 @cindex remote serial stub list
22075 These working remote stubs are distributed with @value{GDBN}:
22080 @cindex @file{i386-stub.c}
22083 For Intel 386 and compatible architectures.
22086 @cindex @file{m68k-stub.c}
22087 @cindex Motorola 680x0
22089 For Motorola 680x0 architectures.
22092 @cindex @file{sh-stub.c}
22095 For Renesas SH architectures.
22098 @cindex @file{sparc-stub.c}
22100 For @sc{sparc} architectures.
22102 @item sparcl-stub.c
22103 @cindex @file{sparcl-stub.c}
22106 For Fujitsu @sc{sparclite} architectures.
22110 The @file{README} file in the @value{GDBN} distribution may list other
22111 recently added stubs.
22114 * Stub Contents:: What the stub can do for you
22115 * Bootstrapping:: What you must do for the stub
22116 * Debug Session:: Putting it all together
22119 @node Stub Contents
22120 @subsection What the Stub Can Do for You
22122 @cindex remote serial stub
22123 The debugging stub for your architecture supplies these three
22127 @item set_debug_traps
22128 @findex set_debug_traps
22129 @cindex remote serial stub, initialization
22130 This routine arranges for @code{handle_exception} to run when your
22131 program stops. You must call this subroutine explicitly in your
22132 program's startup code.
22134 @item handle_exception
22135 @findex handle_exception
22136 @cindex remote serial stub, main routine
22137 This is the central workhorse, but your program never calls it
22138 explicitly---the setup code arranges for @code{handle_exception} to
22139 run when a trap is triggered.
22141 @code{handle_exception} takes control when your program stops during
22142 execution (for example, on a breakpoint), and mediates communications
22143 with @value{GDBN} on the host machine. This is where the communications
22144 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
22145 representative on the target machine. It begins by sending summary
22146 information on the state of your program, then continues to execute,
22147 retrieving and transmitting any information @value{GDBN} needs, until you
22148 execute a @value{GDBN} command that makes your program resume; at that point,
22149 @code{handle_exception} returns control to your own code on the target
22153 @cindex @code{breakpoint} subroutine, remote
22154 Use this auxiliary subroutine to make your program contain a
22155 breakpoint. Depending on the particular situation, this may be the only
22156 way for @value{GDBN} to get control. For instance, if your target
22157 machine has some sort of interrupt button, you won't need to call this;
22158 pressing the interrupt button transfers control to
22159 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
22160 simply receiving characters on the serial port may also trigger a trap;
22161 again, in that situation, you don't need to call @code{breakpoint} from
22162 your own program---simply running @samp{target remote} from the host
22163 @value{GDBN} session gets control.
22165 Call @code{breakpoint} if none of these is true, or if you simply want
22166 to make certain your program stops at a predetermined point for the
22167 start of your debugging session.
22170 @node Bootstrapping
22171 @subsection What You Must Do for the Stub
22173 @cindex remote stub, support routines
22174 The debugging stubs that come with @value{GDBN} are set up for a particular
22175 chip architecture, but they have no information about the rest of your
22176 debugging target machine.
22178 First of all you need to tell the stub how to communicate with the
22182 @item int getDebugChar()
22183 @findex getDebugChar
22184 Write this subroutine to read a single character from the serial port.
22185 It may be identical to @code{getchar} for your target system; a
22186 different name is used to allow you to distinguish the two if you wish.
22188 @item void putDebugChar(int)
22189 @findex putDebugChar
22190 Write this subroutine to write a single character to the serial port.
22191 It may be identical to @code{putchar} for your target system; a
22192 different name is used to allow you to distinguish the two if you wish.
22195 @cindex control C, and remote debugging
22196 @cindex interrupting remote targets
22197 If you want @value{GDBN} to be able to stop your program while it is
22198 running, you need to use an interrupt-driven serial driver, and arrange
22199 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
22200 character). That is the character which @value{GDBN} uses to tell the
22201 remote system to stop.
22203 Getting the debugging target to return the proper status to @value{GDBN}
22204 probably requires changes to the standard stub; one quick and dirty way
22205 is to just execute a breakpoint instruction (the ``dirty'' part is that
22206 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
22208 Other routines you need to supply are:
22211 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
22212 @findex exceptionHandler
22213 Write this function to install @var{exception_address} in the exception
22214 handling tables. You need to do this because the stub does not have any
22215 way of knowing what the exception handling tables on your target system
22216 are like (for example, the processor's table might be in @sc{rom},
22217 containing entries which point to a table in @sc{ram}).
22218 The @var{exception_number} specifies the exception which should be changed;
22219 its meaning is architecture-dependent (for example, different numbers
22220 might represent divide by zero, misaligned access, etc). When this
22221 exception occurs, control should be transferred directly to
22222 @var{exception_address}, and the processor state (stack, registers,
22223 and so on) should be just as it is when a processor exception occurs. So if
22224 you want to use a jump instruction to reach @var{exception_address}, it
22225 should be a simple jump, not a jump to subroutine.
22227 For the 386, @var{exception_address} should be installed as an interrupt
22228 gate so that interrupts are masked while the handler runs. The gate
22229 should be at privilege level 0 (the most privileged level). The
22230 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
22231 help from @code{exceptionHandler}.
22233 @item void flush_i_cache()
22234 @findex flush_i_cache
22235 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
22236 instruction cache, if any, on your target machine. If there is no
22237 instruction cache, this subroutine may be a no-op.
22239 On target machines that have instruction caches, @value{GDBN} requires this
22240 function to make certain that the state of your program is stable.
22244 You must also make sure this library routine is available:
22247 @item void *memset(void *, int, int)
22249 This is the standard library function @code{memset} that sets an area of
22250 memory to a known value. If you have one of the free versions of
22251 @code{libc.a}, @code{memset} can be found there; otherwise, you must
22252 either obtain it from your hardware manufacturer, or write your own.
22255 If you do not use the GNU C compiler, you may need other standard
22256 library subroutines as well; this varies from one stub to another,
22257 but in general the stubs are likely to use any of the common library
22258 subroutines which @code{@value{NGCC}} generates as inline code.
22261 @node Debug Session
22262 @subsection Putting it All Together
22264 @cindex remote serial debugging summary
22265 In summary, when your program is ready to debug, you must follow these
22270 Make sure you have defined the supporting low-level routines
22271 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
22273 @code{getDebugChar}, @code{putDebugChar},
22274 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
22278 Insert these lines in your program's startup code, before the main
22279 procedure is called:
22286 On some machines, when a breakpoint trap is raised, the hardware
22287 automatically makes the PC point to the instruction after the
22288 breakpoint. If your machine doesn't do that, you may need to adjust
22289 @code{handle_exception} to arrange for it to return to the instruction
22290 after the breakpoint on this first invocation, so that your program
22291 doesn't keep hitting the initial breakpoint instead of making
22295 For the 680x0 stub only, you need to provide a variable called
22296 @code{exceptionHook}. Normally you just use:
22299 void (*exceptionHook)() = 0;
22303 but if before calling @code{set_debug_traps}, you set it to point to a
22304 function in your program, that function is called when
22305 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
22306 error). The function indicated by @code{exceptionHook} is called with
22307 one parameter: an @code{int} which is the exception number.
22310 Compile and link together: your program, the @value{GDBN} debugging stub for
22311 your target architecture, and the supporting subroutines.
22314 Make sure you have a serial connection between your target machine and
22315 the @value{GDBN} host, and identify the serial port on the host.
22318 @c The "remote" target now provides a `load' command, so we should
22319 @c document that. FIXME.
22320 Download your program to your target machine (or get it there by
22321 whatever means the manufacturer provides), and start it.
22324 Start @value{GDBN} on the host, and connect to the target
22325 (@pxref{Connecting,,Connecting to a Remote Target}).
22329 @node Configurations
22330 @chapter Configuration-Specific Information
22332 While nearly all @value{GDBN} commands are available for all native and
22333 cross versions of the debugger, there are some exceptions. This chapter
22334 describes things that are only available in certain configurations.
22336 There are three major categories of configurations: native
22337 configurations, where the host and target are the same, embedded
22338 operating system configurations, which are usually the same for several
22339 different processor architectures, and bare embedded processors, which
22340 are quite different from each other.
22345 * Embedded Processors::
22352 This section describes details specific to particular native
22356 * BSD libkvm Interface:: Debugging BSD kernel memory images
22357 * Process Information:: Process information
22358 * DJGPP Native:: Features specific to the DJGPP port
22359 * Cygwin Native:: Features specific to the Cygwin port
22360 * Hurd Native:: Features specific to @sc{gnu} Hurd
22361 * Darwin:: Features specific to Darwin
22362 * FreeBSD:: Features specific to FreeBSD
22365 @node BSD libkvm Interface
22366 @subsection BSD libkvm Interface
22369 @cindex kernel memory image
22370 @cindex kernel crash dump
22372 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
22373 interface that provides a uniform interface for accessing kernel virtual
22374 memory images, including live systems and crash dumps. @value{GDBN}
22375 uses this interface to allow you to debug live kernels and kernel crash
22376 dumps on many native BSD configurations. This is implemented as a
22377 special @code{kvm} debugging target. For debugging a live system, load
22378 the currently running kernel into @value{GDBN} and connect to the
22382 (@value{GDBP}) @b{target kvm}
22385 For debugging crash dumps, provide the file name of the crash dump as an
22389 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
22392 Once connected to the @code{kvm} target, the following commands are
22398 Set current context from the @dfn{Process Control Block} (PCB) address.
22401 Set current context from proc address. This command isn't available on
22402 modern FreeBSD systems.
22405 @node Process Information
22406 @subsection Process Information
22408 @cindex examine process image
22409 @cindex process info via @file{/proc}
22411 Some operating systems provide interfaces to fetch additional
22412 information about running processes beyond memory and per-thread
22413 register state. If @value{GDBN} is configured for an operating system
22414 with a supported interface, the command @code{info proc} is available
22415 to report information about the process running your program, or about
22416 any process running on your system.
22418 One supported interface is a facility called @samp{/proc} that can be
22419 used to examine the image of a running process using file-system
22420 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
22423 On FreeBSD systems, system control nodes are used to query process
22426 In addition, some systems may provide additional process information
22427 in core files. Note that a core file may include a subset of the
22428 information available from a live process. Process information is
22429 currently avaiable from cores created on @sc{gnu}/Linux and FreeBSD
22436 @itemx info proc @var{process-id}
22437 Summarize available information about a process. If a
22438 process ID is specified by @var{process-id}, display information about
22439 that process; otherwise display information about the program being
22440 debugged. The summary includes the debugged process ID, the command
22441 line used to invoke it, its current working directory, and its
22442 executable file's absolute file name.
22444 On some systems, @var{process-id} can be of the form
22445 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
22446 within a process. If the optional @var{pid} part is missing, it means
22447 a thread from the process being debugged (the leading @samp{/} still
22448 needs to be present, or else @value{GDBN} will interpret the number as
22449 a process ID rather than a thread ID).
22451 @item info proc cmdline
22452 @cindex info proc cmdline
22453 Show the original command line of the process. This command is
22454 supported on @sc{gnu}/Linux and FreeBSD.
22456 @item info proc cwd
22457 @cindex info proc cwd
22458 Show the current working directory of the process. This command is
22459 supported on @sc{gnu}/Linux and FreeBSD.
22461 @item info proc exe
22462 @cindex info proc exe
22463 Show the name of executable of the process. This command is supported
22464 on @sc{gnu}/Linux and FreeBSD.
22466 @item info proc files
22467 @cindex info proc files
22468 Show the file descriptors open by the process. For each open file
22469 descriptor, @value{GDBN} shows its number, type (file, directory,
22470 character device, socket), file pointer offset, and the name of the
22471 resource open on the descriptor. The resource name can be a file name
22472 (for files, directories, and devices) or a protocol followed by socket
22473 address (for network connections). This command is supported on
22476 This example shows the open file descriptors for a process using a
22477 tty for standard input and output as well as two network sockets:
22480 (gdb) info proc files 22136
22484 FD Type Offset Flags Name
22485 text file - r-------- /usr/bin/ssh
22486 ctty chr - rw------- /dev/pts/20
22487 cwd dir - r-------- /usr/home/john
22488 root dir - r-------- /
22489 0 chr 0x32933a4 rw------- /dev/pts/20
22490 1 chr 0x32933a4 rw------- /dev/pts/20
22491 2 chr 0x32933a4 rw------- /dev/pts/20
22492 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
22493 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
22496 @item info proc mappings
22497 @cindex memory address space mappings
22498 Report the memory address space ranges accessible in a process. On
22499 Solaris and FreeBSD systems, each memory range includes information on
22500 whether the process has read, write, or execute access rights to each
22501 range. On @sc{gnu}/Linux and FreeBSD systems, each memory range
22502 includes the object file which is mapped to that range.
22504 @item info proc stat
22505 @itemx info proc status
22506 @cindex process detailed status information
22507 Show additional process-related information, including the user ID and
22508 group ID; virtual memory usage; the signals that are pending, blocked,
22509 and ignored; its TTY; its consumption of system and user time; its
22510 stack size; its @samp{nice} value; etc. These commands are supported
22511 on @sc{gnu}/Linux and FreeBSD.
22513 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
22514 information (type @kbd{man 5 proc} from your shell prompt).
22516 For FreeBSD systems, @code{info proc stat} is an alias for @code{info
22519 @item info proc all
22520 Show all the information about the process described under all of the
22521 above @code{info proc} subcommands.
22524 @comment These sub-options of 'info proc' were not included when
22525 @comment procfs.c was re-written. Keep their descriptions around
22526 @comment against the day when someone finds the time to put them back in.
22527 @kindex info proc times
22528 @item info proc times
22529 Starting time, user CPU time, and system CPU time for your program and
22532 @kindex info proc id
22534 Report on the process IDs related to your program: its own process ID,
22535 the ID of its parent, the process group ID, and the session ID.
22538 @item set procfs-trace
22539 @kindex set procfs-trace
22540 @cindex @code{procfs} API calls
22541 This command enables and disables tracing of @code{procfs} API calls.
22543 @item show procfs-trace
22544 @kindex show procfs-trace
22545 Show the current state of @code{procfs} API call tracing.
22547 @item set procfs-file @var{file}
22548 @kindex set procfs-file
22549 Tell @value{GDBN} to write @code{procfs} API trace to the named
22550 @var{file}. @value{GDBN} appends the trace info to the previous
22551 contents of the file. The default is to display the trace on the
22554 @item show procfs-file
22555 @kindex show procfs-file
22556 Show the file to which @code{procfs} API trace is written.
22558 @item proc-trace-entry
22559 @itemx proc-trace-exit
22560 @itemx proc-untrace-entry
22561 @itemx proc-untrace-exit
22562 @kindex proc-trace-entry
22563 @kindex proc-trace-exit
22564 @kindex proc-untrace-entry
22565 @kindex proc-untrace-exit
22566 These commands enable and disable tracing of entries into and exits
22567 from the @code{syscall} interface.
22570 @kindex info pidlist
22571 @cindex process list, QNX Neutrino
22572 For QNX Neutrino only, this command displays the list of all the
22573 processes and all the threads within each process.
22576 @kindex info meminfo
22577 @cindex mapinfo list, QNX Neutrino
22578 For QNX Neutrino only, this command displays the list of all mapinfos.
22582 @subsection Features for Debugging @sc{djgpp} Programs
22583 @cindex @sc{djgpp} debugging
22584 @cindex native @sc{djgpp} debugging
22585 @cindex MS-DOS-specific commands
22588 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
22589 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
22590 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
22591 top of real-mode DOS systems and their emulations.
22593 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
22594 defines a few commands specific to the @sc{djgpp} port. This
22595 subsection describes those commands.
22600 This is a prefix of @sc{djgpp}-specific commands which print
22601 information about the target system and important OS structures.
22604 @cindex MS-DOS system info
22605 @cindex free memory information (MS-DOS)
22606 @item info dos sysinfo
22607 This command displays assorted information about the underlying
22608 platform: the CPU type and features, the OS version and flavor, the
22609 DPMI version, and the available conventional and DPMI memory.
22614 @cindex segment descriptor tables
22615 @cindex descriptor tables display
22617 @itemx info dos ldt
22618 @itemx info dos idt
22619 These 3 commands display entries from, respectively, Global, Local,
22620 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
22621 tables are data structures which store a descriptor for each segment
22622 that is currently in use. The segment's selector is an index into a
22623 descriptor table; the table entry for that index holds the
22624 descriptor's base address and limit, and its attributes and access
22627 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
22628 segment (used for both data and the stack), and a DOS segment (which
22629 allows access to DOS/BIOS data structures and absolute addresses in
22630 conventional memory). However, the DPMI host will usually define
22631 additional segments in order to support the DPMI environment.
22633 @cindex garbled pointers
22634 These commands allow to display entries from the descriptor tables.
22635 Without an argument, all entries from the specified table are
22636 displayed. An argument, which should be an integer expression, means
22637 display a single entry whose index is given by the argument. For
22638 example, here's a convenient way to display information about the
22639 debugged program's data segment:
22642 @exdent @code{(@value{GDBP}) info dos ldt $ds}
22643 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
22647 This comes in handy when you want to see whether a pointer is outside
22648 the data segment's limit (i.e.@: @dfn{garbled}).
22650 @cindex page tables display (MS-DOS)
22652 @itemx info dos pte
22653 These two commands display entries from, respectively, the Page
22654 Directory and the Page Tables. Page Directories and Page Tables are
22655 data structures which control how virtual memory addresses are mapped
22656 into physical addresses. A Page Table includes an entry for every
22657 page of memory that is mapped into the program's address space; there
22658 may be several Page Tables, each one holding up to 4096 entries. A
22659 Page Directory has up to 4096 entries, one each for every Page Table
22660 that is currently in use.
22662 Without an argument, @kbd{info dos pde} displays the entire Page
22663 Directory, and @kbd{info dos pte} displays all the entries in all of
22664 the Page Tables. An argument, an integer expression, given to the
22665 @kbd{info dos pde} command means display only that entry from the Page
22666 Directory table. An argument given to the @kbd{info dos pte} command
22667 means display entries from a single Page Table, the one pointed to by
22668 the specified entry in the Page Directory.
22670 @cindex direct memory access (DMA) on MS-DOS
22671 These commands are useful when your program uses @dfn{DMA} (Direct
22672 Memory Access), which needs physical addresses to program the DMA
22675 These commands are supported only with some DPMI servers.
22677 @cindex physical address from linear address
22678 @item info dos address-pte @var{addr}
22679 This command displays the Page Table entry for a specified linear
22680 address. The argument @var{addr} is a linear address which should
22681 already have the appropriate segment's base address added to it,
22682 because this command accepts addresses which may belong to @emph{any}
22683 segment. For example, here's how to display the Page Table entry for
22684 the page where a variable @code{i} is stored:
22687 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
22688 @exdent @code{Page Table entry for address 0x11a00d30:}
22689 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
22693 This says that @code{i} is stored at offset @code{0xd30} from the page
22694 whose physical base address is @code{0x02698000}, and shows all the
22695 attributes of that page.
22697 Note that you must cast the addresses of variables to a @code{char *},
22698 since otherwise the value of @code{__djgpp_base_address}, the base
22699 address of all variables and functions in a @sc{djgpp} program, will
22700 be added using the rules of C pointer arithmetics: if @code{i} is
22701 declared an @code{int}, @value{GDBN} will add 4 times the value of
22702 @code{__djgpp_base_address} to the address of @code{i}.
22704 Here's another example, it displays the Page Table entry for the
22708 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
22709 @exdent @code{Page Table entry for address 0x29110:}
22710 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
22714 (The @code{+ 3} offset is because the transfer buffer's address is the
22715 3rd member of the @code{_go32_info_block} structure.) The output
22716 clearly shows that this DPMI server maps the addresses in conventional
22717 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
22718 linear (@code{0x29110}) addresses are identical.
22720 This command is supported only with some DPMI servers.
22723 @cindex DOS serial data link, remote debugging
22724 In addition to native debugging, the DJGPP port supports remote
22725 debugging via a serial data link. The following commands are specific
22726 to remote serial debugging in the DJGPP port of @value{GDBN}.
22729 @kindex set com1base
22730 @kindex set com1irq
22731 @kindex set com2base
22732 @kindex set com2irq
22733 @kindex set com3base
22734 @kindex set com3irq
22735 @kindex set com4base
22736 @kindex set com4irq
22737 @item set com1base @var{addr}
22738 This command sets the base I/O port address of the @file{COM1} serial
22741 @item set com1irq @var{irq}
22742 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
22743 for the @file{COM1} serial port.
22745 There are similar commands @samp{set com2base}, @samp{set com3irq},
22746 etc.@: for setting the port address and the @code{IRQ} lines for the
22749 @kindex show com1base
22750 @kindex show com1irq
22751 @kindex show com2base
22752 @kindex show com2irq
22753 @kindex show com3base
22754 @kindex show com3irq
22755 @kindex show com4base
22756 @kindex show com4irq
22757 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
22758 display the current settings of the base address and the @code{IRQ}
22759 lines used by the COM ports.
22762 @kindex info serial
22763 @cindex DOS serial port status
22764 This command prints the status of the 4 DOS serial ports. For each
22765 port, it prints whether it's active or not, its I/O base address and
22766 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
22767 counts of various errors encountered so far.
22771 @node Cygwin Native
22772 @subsection Features for Debugging MS Windows PE Executables
22773 @cindex MS Windows debugging
22774 @cindex native Cygwin debugging
22775 @cindex Cygwin-specific commands
22777 @value{GDBN} supports native debugging of MS Windows programs, including
22778 DLLs with and without symbolic debugging information.
22780 @cindex Ctrl-BREAK, MS-Windows
22781 @cindex interrupt debuggee on MS-Windows
22782 MS-Windows programs that call @code{SetConsoleMode} to switch off the
22783 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
22784 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
22785 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
22786 sequence, which can be used to interrupt the debuggee even if it
22789 There are various additional Cygwin-specific commands, described in
22790 this section. Working with DLLs that have no debugging symbols is
22791 described in @ref{Non-debug DLL Symbols}.
22796 This is a prefix of MS Windows-specific commands which print
22797 information about the target system and important OS structures.
22799 @item info w32 selector
22800 This command displays information returned by
22801 the Win32 API @code{GetThreadSelectorEntry} function.
22802 It takes an optional argument that is evaluated to
22803 a long value to give the information about this given selector.
22804 Without argument, this command displays information
22805 about the six segment registers.
22807 @item info w32 thread-information-block
22808 This command displays thread specific information stored in the
22809 Thread Information Block (readable on the X86 CPU family using @code{$fs}
22810 selector for 32-bit programs and @code{$gs} for 64-bit programs).
22812 @kindex signal-event
22813 @item signal-event @var{id}
22814 This command signals an event with user-provided @var{id}. Used to resume
22815 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
22817 To use it, create or edit the following keys in
22818 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
22819 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
22820 (for x86_64 versions):
22824 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
22825 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
22826 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
22828 The first @code{%ld} will be replaced by the process ID of the
22829 crashing process, the second @code{%ld} will be replaced by the ID of
22830 the event that blocks the crashing process, waiting for @value{GDBN}
22834 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
22835 make the system run debugger specified by the Debugger key
22836 automatically, @code{0} will cause a dialog box with ``OK'' and
22837 ``Cancel'' buttons to appear, which allows the user to either
22838 terminate the crashing process (OK) or debug it (Cancel).
22841 @kindex set cygwin-exceptions
22842 @cindex debugging the Cygwin DLL
22843 @cindex Cygwin DLL, debugging
22844 @item set cygwin-exceptions @var{mode}
22845 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
22846 happen inside the Cygwin DLL. If @var{mode} is @code{off},
22847 @value{GDBN} will delay recognition of exceptions, and may ignore some
22848 exceptions which seem to be caused by internal Cygwin DLL
22849 ``bookkeeping''. This option is meant primarily for debugging the
22850 Cygwin DLL itself; the default value is @code{off} to avoid annoying
22851 @value{GDBN} users with false @code{SIGSEGV} signals.
22853 @kindex show cygwin-exceptions
22854 @item show cygwin-exceptions
22855 Displays whether @value{GDBN} will break on exceptions that happen
22856 inside the Cygwin DLL itself.
22858 @kindex set new-console
22859 @item set new-console @var{mode}
22860 If @var{mode} is @code{on} the debuggee will
22861 be started in a new console on next start.
22862 If @var{mode} is @code{off}, the debuggee will
22863 be started in the same console as the debugger.
22865 @kindex show new-console
22866 @item show new-console
22867 Displays whether a new console is used
22868 when the debuggee is started.
22870 @kindex set new-group
22871 @item set new-group @var{mode}
22872 This boolean value controls whether the debuggee should
22873 start a new group or stay in the same group as the debugger.
22874 This affects the way the Windows OS handles
22877 @kindex show new-group
22878 @item show new-group
22879 Displays current value of new-group boolean.
22881 @kindex set debugevents
22882 @item set debugevents
22883 This boolean value adds debug output concerning kernel events related
22884 to the debuggee seen by the debugger. This includes events that
22885 signal thread and process creation and exit, DLL loading and
22886 unloading, console interrupts, and debugging messages produced by the
22887 Windows @code{OutputDebugString} API call.
22889 @kindex set debugexec
22890 @item set debugexec
22891 This boolean value adds debug output concerning execute events
22892 (such as resume thread) seen by the debugger.
22894 @kindex set debugexceptions
22895 @item set debugexceptions
22896 This boolean value adds debug output concerning exceptions in the
22897 debuggee seen by the debugger.
22899 @kindex set debugmemory
22900 @item set debugmemory
22901 This boolean value adds debug output concerning debuggee memory reads
22902 and writes by the debugger.
22906 This boolean values specifies whether the debuggee is called
22907 via a shell or directly (default value is on).
22911 Displays if the debuggee will be started with a shell.
22916 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
22919 @node Non-debug DLL Symbols
22920 @subsubsection Support for DLLs without Debugging Symbols
22921 @cindex DLLs with no debugging symbols
22922 @cindex Minimal symbols and DLLs
22924 Very often on windows, some of the DLLs that your program relies on do
22925 not include symbolic debugging information (for example,
22926 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
22927 symbols in a DLL, it relies on the minimal amount of symbolic
22928 information contained in the DLL's export table. This section
22929 describes working with such symbols, known internally to @value{GDBN} as
22930 ``minimal symbols''.
22932 Note that before the debugged program has started execution, no DLLs
22933 will have been loaded. The easiest way around this problem is simply to
22934 start the program --- either by setting a breakpoint or letting the
22935 program run once to completion.
22937 @subsubsection DLL Name Prefixes
22939 In keeping with the naming conventions used by the Microsoft debugging
22940 tools, DLL export symbols are made available with a prefix based on the
22941 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
22942 also entered into the symbol table, so @code{CreateFileA} is often
22943 sufficient. In some cases there will be name clashes within a program
22944 (particularly if the executable itself includes full debugging symbols)
22945 necessitating the use of the fully qualified name when referring to the
22946 contents of the DLL. Use single-quotes around the name to avoid the
22947 exclamation mark (``!'') being interpreted as a language operator.
22949 Note that the internal name of the DLL may be all upper-case, even
22950 though the file name of the DLL is lower-case, or vice-versa. Since
22951 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
22952 some confusion. If in doubt, try the @code{info functions} and
22953 @code{info variables} commands or even @code{maint print msymbols}
22954 (@pxref{Symbols}). Here's an example:
22957 (@value{GDBP}) info function CreateFileA
22958 All functions matching regular expression "CreateFileA":
22960 Non-debugging symbols:
22961 0x77e885f4 CreateFileA
22962 0x77e885f4 KERNEL32!CreateFileA
22966 (@value{GDBP}) info function !
22967 All functions matching regular expression "!":
22969 Non-debugging symbols:
22970 0x6100114c cygwin1!__assert
22971 0x61004034 cygwin1!_dll_crt0@@0
22972 0x61004240 cygwin1!dll_crt0(per_process *)
22976 @subsubsection Working with Minimal Symbols
22978 Symbols extracted from a DLL's export table do not contain very much
22979 type information. All that @value{GDBN} can do is guess whether a symbol
22980 refers to a function or variable depending on the linker section that
22981 contains the symbol. Also note that the actual contents of the memory
22982 contained in a DLL are not available unless the program is running. This
22983 means that you cannot examine the contents of a variable or disassemble
22984 a function within a DLL without a running program.
22986 Variables are generally treated as pointers and dereferenced
22987 automatically. For this reason, it is often necessary to prefix a
22988 variable name with the address-of operator (``&'') and provide explicit
22989 type information in the command. Here's an example of the type of
22993 (@value{GDBP}) print 'cygwin1!__argv'
22994 'cygwin1!__argv' has unknown type; cast it to its declared type
22998 (@value{GDBP}) x 'cygwin1!__argv'
22999 'cygwin1!__argv' has unknown type; cast it to its declared type
23002 And two possible solutions:
23005 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
23006 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
23010 (@value{GDBP}) x/2x &'cygwin1!__argv'
23011 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
23012 (@value{GDBP}) x/x 0x10021608
23013 0x10021608: 0x0022fd98
23014 (@value{GDBP}) x/s 0x0022fd98
23015 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
23018 Setting a break point within a DLL is possible even before the program
23019 starts execution. However, under these circumstances, @value{GDBN} can't
23020 examine the initial instructions of the function in order to skip the
23021 function's frame set-up code. You can work around this by using ``*&''
23022 to set the breakpoint at a raw memory address:
23025 (@value{GDBP}) break *&'python22!PyOS_Readline'
23026 Breakpoint 1 at 0x1e04eff0
23029 The author of these extensions is not entirely convinced that setting a
23030 break point within a shared DLL like @file{kernel32.dll} is completely
23034 @subsection Commands Specific to @sc{gnu} Hurd Systems
23035 @cindex @sc{gnu} Hurd debugging
23037 This subsection describes @value{GDBN} commands specific to the
23038 @sc{gnu} Hurd native debugging.
23043 @kindex set signals@r{, Hurd command}
23044 @kindex set sigs@r{, Hurd command}
23045 This command toggles the state of inferior signal interception by
23046 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
23047 affected by this command. @code{sigs} is a shorthand alias for
23052 @kindex show signals@r{, Hurd command}
23053 @kindex show sigs@r{, Hurd command}
23054 Show the current state of intercepting inferior's signals.
23056 @item set signal-thread
23057 @itemx set sigthread
23058 @kindex set signal-thread
23059 @kindex set sigthread
23060 This command tells @value{GDBN} which thread is the @code{libc} signal
23061 thread. That thread is run when a signal is delivered to a running
23062 process. @code{set sigthread} is the shorthand alias of @code{set
23065 @item show signal-thread
23066 @itemx show sigthread
23067 @kindex show signal-thread
23068 @kindex show sigthread
23069 These two commands show which thread will run when the inferior is
23070 delivered a signal.
23073 @kindex set stopped@r{, Hurd command}
23074 This commands tells @value{GDBN} that the inferior process is stopped,
23075 as with the @code{SIGSTOP} signal. The stopped process can be
23076 continued by delivering a signal to it.
23079 @kindex show stopped@r{, Hurd command}
23080 This command shows whether @value{GDBN} thinks the debuggee is
23083 @item set exceptions
23084 @kindex set exceptions@r{, Hurd command}
23085 Use this command to turn off trapping of exceptions in the inferior.
23086 When exception trapping is off, neither breakpoints nor
23087 single-stepping will work. To restore the default, set exception
23090 @item show exceptions
23091 @kindex show exceptions@r{, Hurd command}
23092 Show the current state of trapping exceptions in the inferior.
23094 @item set task pause
23095 @kindex set task@r{, Hurd commands}
23096 @cindex task attributes (@sc{gnu} Hurd)
23097 @cindex pause current task (@sc{gnu} Hurd)
23098 This command toggles task suspension when @value{GDBN} has control.
23099 Setting it to on takes effect immediately, and the task is suspended
23100 whenever @value{GDBN} gets control. Setting it to off will take
23101 effect the next time the inferior is continued. If this option is set
23102 to off, you can use @code{set thread default pause on} or @code{set
23103 thread pause on} (see below) to pause individual threads.
23105 @item show task pause
23106 @kindex show task@r{, Hurd commands}
23107 Show the current state of task suspension.
23109 @item set task detach-suspend-count
23110 @cindex task suspend count
23111 @cindex detach from task, @sc{gnu} Hurd
23112 This command sets the suspend count the task will be left with when
23113 @value{GDBN} detaches from it.
23115 @item show task detach-suspend-count
23116 Show the suspend count the task will be left with when detaching.
23118 @item set task exception-port
23119 @itemx set task excp
23120 @cindex task exception port, @sc{gnu} Hurd
23121 This command sets the task exception port to which @value{GDBN} will
23122 forward exceptions. The argument should be the value of the @dfn{send
23123 rights} of the task. @code{set task excp} is a shorthand alias.
23125 @item set noninvasive
23126 @cindex noninvasive task options
23127 This command switches @value{GDBN} to a mode that is the least
23128 invasive as far as interfering with the inferior is concerned. This
23129 is the same as using @code{set task pause}, @code{set exceptions}, and
23130 @code{set signals} to values opposite to the defaults.
23132 @item info send-rights
23133 @itemx info receive-rights
23134 @itemx info port-rights
23135 @itemx info port-sets
23136 @itemx info dead-names
23139 @cindex send rights, @sc{gnu} Hurd
23140 @cindex receive rights, @sc{gnu} Hurd
23141 @cindex port rights, @sc{gnu} Hurd
23142 @cindex port sets, @sc{gnu} Hurd
23143 @cindex dead names, @sc{gnu} Hurd
23144 These commands display information about, respectively, send rights,
23145 receive rights, port rights, port sets, and dead names of a task.
23146 There are also shorthand aliases: @code{info ports} for @code{info
23147 port-rights} and @code{info psets} for @code{info port-sets}.
23149 @item set thread pause
23150 @kindex set thread@r{, Hurd command}
23151 @cindex thread properties, @sc{gnu} Hurd
23152 @cindex pause current thread (@sc{gnu} Hurd)
23153 This command toggles current thread suspension when @value{GDBN} has
23154 control. Setting it to on takes effect immediately, and the current
23155 thread is suspended whenever @value{GDBN} gets control. Setting it to
23156 off will take effect the next time the inferior is continued.
23157 Normally, this command has no effect, since when @value{GDBN} has
23158 control, the whole task is suspended. However, if you used @code{set
23159 task pause off} (see above), this command comes in handy to suspend
23160 only the current thread.
23162 @item show thread pause
23163 @kindex show thread@r{, Hurd command}
23164 This command shows the state of current thread suspension.
23166 @item set thread run
23167 This command sets whether the current thread is allowed to run.
23169 @item show thread run
23170 Show whether the current thread is allowed to run.
23172 @item set thread detach-suspend-count
23173 @cindex thread suspend count, @sc{gnu} Hurd
23174 @cindex detach from thread, @sc{gnu} Hurd
23175 This command sets the suspend count @value{GDBN} will leave on a
23176 thread when detaching. This number is relative to the suspend count
23177 found by @value{GDBN} when it notices the thread; use @code{set thread
23178 takeover-suspend-count} to force it to an absolute value.
23180 @item show thread detach-suspend-count
23181 Show the suspend count @value{GDBN} will leave on the thread when
23184 @item set thread exception-port
23185 @itemx set thread excp
23186 Set the thread exception port to which to forward exceptions. This
23187 overrides the port set by @code{set task exception-port} (see above).
23188 @code{set thread excp} is the shorthand alias.
23190 @item set thread takeover-suspend-count
23191 Normally, @value{GDBN}'s thread suspend counts are relative to the
23192 value @value{GDBN} finds when it notices each thread. This command
23193 changes the suspend counts to be absolute instead.
23195 @item set thread default
23196 @itemx show thread default
23197 @cindex thread default settings, @sc{gnu} Hurd
23198 Each of the above @code{set thread} commands has a @code{set thread
23199 default} counterpart (e.g., @code{set thread default pause}, @code{set
23200 thread default exception-port}, etc.). The @code{thread default}
23201 variety of commands sets the default thread properties for all
23202 threads; you can then change the properties of individual threads with
23203 the non-default commands.
23210 @value{GDBN} provides the following commands specific to the Darwin target:
23213 @item set debug darwin @var{num}
23214 @kindex set debug darwin
23215 When set to a non zero value, enables debugging messages specific to
23216 the Darwin support. Higher values produce more verbose output.
23218 @item show debug darwin
23219 @kindex show debug darwin
23220 Show the current state of Darwin messages.
23222 @item set debug mach-o @var{num}
23223 @kindex set debug mach-o
23224 When set to a non zero value, enables debugging messages while
23225 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
23226 file format used on Darwin for object and executable files.) Higher
23227 values produce more verbose output. This is a command to diagnose
23228 problems internal to @value{GDBN} and should not be needed in normal
23231 @item show debug mach-o
23232 @kindex show debug mach-o
23233 Show the current state of Mach-O file messages.
23235 @item set mach-exceptions on
23236 @itemx set mach-exceptions off
23237 @kindex set mach-exceptions
23238 On Darwin, faults are first reported as a Mach exception and are then
23239 mapped to a Posix signal. Use this command to turn on trapping of
23240 Mach exceptions in the inferior. This might be sometimes useful to
23241 better understand the cause of a fault. The default is off.
23243 @item show mach-exceptions
23244 @kindex show mach-exceptions
23245 Show the current state of exceptions trapping.
23249 @subsection FreeBSD
23252 When the ABI of a system call is changed in the FreeBSD kernel, this
23253 is implemented by leaving a compatibility system call using the old
23254 ABI at the existing number and allocating a new system call number for
23255 the version using the new ABI. As a convenience, when a system call
23256 is caught by name (@pxref{catch syscall}), compatibility system calls
23259 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
23260 system call and catching the @code{kevent} system call by name catches
23264 (@value{GDBP}) catch syscall kevent
23265 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
23271 @section Embedded Operating Systems
23273 This section describes configurations involving the debugging of
23274 embedded operating systems that are available for several different
23277 @value{GDBN} includes the ability to debug programs running on
23278 various real-time operating systems.
23280 @node Embedded Processors
23281 @section Embedded Processors
23283 This section goes into details specific to particular embedded
23286 @cindex send command to simulator
23287 Whenever a specific embedded processor has a simulator, @value{GDBN}
23288 allows to send an arbitrary command to the simulator.
23291 @item sim @var{command}
23292 @kindex sim@r{, a command}
23293 Send an arbitrary @var{command} string to the simulator. Consult the
23294 documentation for the specific simulator in use for information about
23295 acceptable commands.
23300 * ARC:: Synopsys ARC
23302 * M68K:: Motorola M68K
23303 * MicroBlaze:: Xilinx MicroBlaze
23304 * MIPS Embedded:: MIPS Embedded
23305 * OpenRISC 1000:: OpenRISC 1000 (or1k)
23306 * PowerPC Embedded:: PowerPC Embedded
23309 * Super-H:: Renesas Super-H
23313 @subsection Synopsys ARC
23314 @cindex Synopsys ARC
23315 @cindex ARC specific commands
23321 @value{GDBN} provides the following ARC-specific commands:
23324 @item set debug arc
23325 @kindex set debug arc
23326 Control the level of ARC specific debug messages. Use 0 for no messages (the
23327 default), 1 for debug messages, and 2 for even more debug messages.
23329 @item show debug arc
23330 @kindex show debug arc
23331 Show the level of ARC specific debugging in operation.
23333 @item maint print arc arc-instruction @var{address}
23334 @kindex maint print arc arc-instruction
23335 Print internal disassembler information about instruction at a given address.
23342 @value{GDBN} provides the following ARM-specific commands:
23345 @item set arm disassembler
23347 This commands selects from a list of disassembly styles. The
23348 @code{"std"} style is the standard style.
23350 @item show arm disassembler
23352 Show the current disassembly style.
23354 @item set arm apcs32
23355 @cindex ARM 32-bit mode
23356 This command toggles ARM operation mode between 32-bit and 26-bit.
23358 @item show arm apcs32
23359 Display the current usage of the ARM 32-bit mode.
23361 @item set arm fpu @var{fputype}
23362 This command sets the ARM floating-point unit (FPU) type. The
23363 argument @var{fputype} can be one of these:
23367 Determine the FPU type by querying the OS ABI.
23369 Software FPU, with mixed-endian doubles on little-endian ARM
23372 GCC-compiled FPA co-processor.
23374 Software FPU with pure-endian doubles.
23380 Show the current type of the FPU.
23383 This command forces @value{GDBN} to use the specified ABI.
23386 Show the currently used ABI.
23388 @item set arm fallback-mode (arm|thumb|auto)
23389 @value{GDBN} uses the symbol table, when available, to determine
23390 whether instructions are ARM or Thumb. This command controls
23391 @value{GDBN}'s default behavior when the symbol table is not
23392 available. The default is @samp{auto}, which causes @value{GDBN} to
23393 use the current execution mode (from the @code{T} bit in the @code{CPSR}
23396 @item show arm fallback-mode
23397 Show the current fallback instruction mode.
23399 @item set arm force-mode (arm|thumb|auto)
23400 This command overrides use of the symbol table to determine whether
23401 instructions are ARM or Thumb. The default is @samp{auto}, which
23402 causes @value{GDBN} to use the symbol table and then the setting
23403 of @samp{set arm fallback-mode}.
23405 @item show arm force-mode
23406 Show the current forced instruction mode.
23408 @item set debug arm
23409 Toggle whether to display ARM-specific debugging messages from the ARM
23410 target support subsystem.
23412 @item show debug arm
23413 Show whether ARM-specific debugging messages are enabled.
23417 @item target sim @r{[}@var{simargs}@r{]} @dots{}
23418 The @value{GDBN} ARM simulator accepts the following optional arguments.
23421 @item --swi-support=@var{type}
23422 Tell the simulator which SWI interfaces to support. The argument
23423 @var{type} may be a comma separated list of the following values.
23424 The default value is @code{all}.
23439 The Motorola m68k configuration includes ColdFire support.
23442 @subsection MicroBlaze
23443 @cindex Xilinx MicroBlaze
23444 @cindex XMD, Xilinx Microprocessor Debugger
23446 The MicroBlaze is a soft-core processor supported on various Xilinx
23447 FPGAs, such as Spartan or Virtex series. Boards with these processors
23448 usually have JTAG ports which connect to a host system running the Xilinx
23449 Embedded Development Kit (EDK) or Software Development Kit (SDK).
23450 This host system is used to download the configuration bitstream to
23451 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
23452 communicates with the target board using the JTAG interface and
23453 presents a @code{gdbserver} interface to the board. By default
23454 @code{xmd} uses port @code{1234}. (While it is possible to change
23455 this default port, it requires the use of undocumented @code{xmd}
23456 commands. Contact Xilinx support if you need to do this.)
23458 Use these GDB commands to connect to the MicroBlaze target processor.
23461 @item target remote :1234
23462 Use this command to connect to the target if you are running @value{GDBN}
23463 on the same system as @code{xmd}.
23465 @item target remote @var{xmd-host}:1234
23466 Use this command to connect to the target if it is connected to @code{xmd}
23467 running on a different system named @var{xmd-host}.
23470 Use this command to download a program to the MicroBlaze target.
23472 @item set debug microblaze @var{n}
23473 Enable MicroBlaze-specific debugging messages if non-zero.
23475 @item show debug microblaze @var{n}
23476 Show MicroBlaze-specific debugging level.
23479 @node MIPS Embedded
23480 @subsection @acronym{MIPS} Embedded
23483 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
23486 @item set mipsfpu double
23487 @itemx set mipsfpu single
23488 @itemx set mipsfpu none
23489 @itemx set mipsfpu auto
23490 @itemx show mipsfpu
23491 @kindex set mipsfpu
23492 @kindex show mipsfpu
23493 @cindex @acronym{MIPS} remote floating point
23494 @cindex floating point, @acronym{MIPS} remote
23495 If your target board does not support the @acronym{MIPS} floating point
23496 coprocessor, you should use the command @samp{set mipsfpu none} (if you
23497 need this, you may wish to put the command in your @value{GDBN} init
23498 file). This tells @value{GDBN} how to find the return value of
23499 functions which return floating point values. It also allows
23500 @value{GDBN} to avoid saving the floating point registers when calling
23501 functions on the board. If you are using a floating point coprocessor
23502 with only single precision floating point support, as on the @sc{r4650}
23503 processor, use the command @samp{set mipsfpu single}. The default
23504 double precision floating point coprocessor may be selected using
23505 @samp{set mipsfpu double}.
23507 In previous versions the only choices were double precision or no
23508 floating point, so @samp{set mipsfpu on} will select double precision
23509 and @samp{set mipsfpu off} will select no floating point.
23511 As usual, you can inquire about the @code{mipsfpu} variable with
23512 @samp{show mipsfpu}.
23515 @node OpenRISC 1000
23516 @subsection OpenRISC 1000
23517 @cindex OpenRISC 1000
23520 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
23521 mainly provided as a soft-core which can run on Xilinx, Altera and other
23524 @value{GDBN} for OpenRISC supports the below commands when connecting to
23532 Runs the builtin CPU simulator which can run very basic
23533 programs but does not support most hardware functions like MMU.
23534 For more complex use cases the user is advised to run an external
23535 target, and connect using @samp{target remote}.
23537 Example: @code{target sim}
23539 @item set debug or1k
23540 Toggle whether to display OpenRISC-specific debugging messages from the
23541 OpenRISC target support subsystem.
23543 @item show debug or1k
23544 Show whether OpenRISC-specific debugging messages are enabled.
23547 @node PowerPC Embedded
23548 @subsection PowerPC Embedded
23550 @cindex DVC register
23551 @value{GDBN} supports using the DVC (Data Value Compare) register to
23552 implement in hardware simple hardware watchpoint conditions of the form:
23555 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
23556 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
23559 The DVC register will be automatically used when @value{GDBN} detects
23560 such pattern in a condition expression, and the created watchpoint uses one
23561 debug register (either the @code{exact-watchpoints} option is on and the
23562 variable is scalar, or the variable has a length of one byte). This feature
23563 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
23566 When running on PowerPC embedded processors, @value{GDBN} automatically uses
23567 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
23568 in which case watchpoints using only one debug register are created when
23569 watching variables of scalar types.
23571 You can create an artificial array to watch an arbitrary memory
23572 region using one of the following commands (@pxref{Expressions}):
23575 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
23576 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
23579 PowerPC embedded processors support masked watchpoints. See the discussion
23580 about the @code{mask} argument in @ref{Set Watchpoints}.
23582 @cindex ranged breakpoint
23583 PowerPC embedded processors support hardware accelerated
23584 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
23585 the inferior whenever it executes an instruction at any address within
23586 the range it specifies. To set a ranged breakpoint in @value{GDBN},
23587 use the @code{break-range} command.
23589 @value{GDBN} provides the following PowerPC-specific commands:
23592 @kindex break-range
23593 @item break-range @var{start-location}, @var{end-location}
23594 Set a breakpoint for an address range given by
23595 @var{start-location} and @var{end-location}, which can specify a function name,
23596 a line number, an offset of lines from the current line or from the start
23597 location, or an address of an instruction (see @ref{Specify Location},
23598 for a list of all the possible ways to specify a @var{location}.)
23599 The breakpoint will stop execution of the inferior whenever it
23600 executes an instruction at any address within the specified range,
23601 (including @var{start-location} and @var{end-location}.)
23603 @kindex set powerpc
23604 @item set powerpc soft-float
23605 @itemx show powerpc soft-float
23606 Force @value{GDBN} to use (or not use) a software floating point calling
23607 convention. By default, @value{GDBN} selects the calling convention based
23608 on the selected architecture and the provided executable file.
23610 @item set powerpc vector-abi
23611 @itemx show powerpc vector-abi
23612 Force @value{GDBN} to use the specified calling convention for vector
23613 arguments and return values. The valid options are @samp{auto};
23614 @samp{generic}, to avoid vector registers even if they are present;
23615 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
23616 registers. By default, @value{GDBN} selects the calling convention
23617 based on the selected architecture and the provided executable file.
23619 @item set powerpc exact-watchpoints
23620 @itemx show powerpc exact-watchpoints
23621 Allow @value{GDBN} to use only one debug register when watching a variable
23622 of scalar type, thus assuming that the variable is accessed through the
23623 address of its first byte.
23628 @subsection Atmel AVR
23631 When configured for debugging the Atmel AVR, @value{GDBN} supports the
23632 following AVR-specific commands:
23635 @item info io_registers
23636 @kindex info io_registers@r{, AVR}
23637 @cindex I/O registers (Atmel AVR)
23638 This command displays information about the AVR I/O registers. For
23639 each register, @value{GDBN} prints its number and value.
23646 When configured for debugging CRIS, @value{GDBN} provides the
23647 following CRIS-specific commands:
23650 @item set cris-version @var{ver}
23651 @cindex CRIS version
23652 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
23653 The CRIS version affects register names and sizes. This command is useful in
23654 case autodetection of the CRIS version fails.
23656 @item show cris-version
23657 Show the current CRIS version.
23659 @item set cris-dwarf2-cfi
23660 @cindex DWARF-2 CFI and CRIS
23661 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
23662 Change to @samp{off} when using @code{gcc-cris} whose version is below
23665 @item show cris-dwarf2-cfi
23666 Show the current state of using DWARF-2 CFI.
23668 @item set cris-mode @var{mode}
23670 Set the current CRIS mode to @var{mode}. It should only be changed when
23671 debugging in guru mode, in which case it should be set to
23672 @samp{guru} (the default is @samp{normal}).
23674 @item show cris-mode
23675 Show the current CRIS mode.
23679 @subsection Renesas Super-H
23682 For the Renesas Super-H processor, @value{GDBN} provides these
23686 @item set sh calling-convention @var{convention}
23687 @kindex set sh calling-convention
23688 Set the calling-convention used when calling functions from @value{GDBN}.
23689 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
23690 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
23691 convention. If the DWARF-2 information of the called function specifies
23692 that the function follows the Renesas calling convention, the function
23693 is called using the Renesas calling convention. If the calling convention
23694 is set to @samp{renesas}, the Renesas calling convention is always used,
23695 regardless of the DWARF-2 information. This can be used to override the
23696 default of @samp{gcc} if debug information is missing, or the compiler
23697 does not emit the DWARF-2 calling convention entry for a function.
23699 @item show sh calling-convention
23700 @kindex show sh calling-convention
23701 Show the current calling convention setting.
23706 @node Architectures
23707 @section Architectures
23709 This section describes characteristics of architectures that affect
23710 all uses of @value{GDBN} with the architecture, both native and cross.
23717 * HPPA:: HP PA architecture
23718 * SPU:: Cell Broadband Engine SPU architecture
23726 @subsection AArch64
23727 @cindex AArch64 support
23729 When @value{GDBN} is debugging the AArch64 architecture, it provides the
23730 following special commands:
23733 @item set debug aarch64
23734 @kindex set debug aarch64
23735 This command determines whether AArch64 architecture-specific debugging
23736 messages are to be displayed.
23738 @item show debug aarch64
23739 Show whether AArch64 debugging messages are displayed.
23743 @subsubsection AArch64 SVE.
23744 @cindex AArch64 SVE.
23746 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
23747 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
23748 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
23749 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
23750 @code{$vg} will be provided. This is the vector granule for the current thread
23751 and represents the number of 64-bit chunks in an SVE @code{z} register.
23753 If the vector length changes, then the @code{$vg} register will be updated,
23754 but the lengths of the @code{z} and @code{p} registers will not change. This
23755 is a known limitation of @value{GDBN} and does not affect the execution of the
23760 @subsection x86 Architecture-specific Issues
23763 @item set struct-convention @var{mode}
23764 @kindex set struct-convention
23765 @cindex struct return convention
23766 @cindex struct/union returned in registers
23767 Set the convention used by the inferior to return @code{struct}s and
23768 @code{union}s from functions to @var{mode}. Possible values of
23769 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
23770 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
23771 are returned on the stack, while @code{"reg"} means that a
23772 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
23773 be returned in a register.
23775 @item show struct-convention
23776 @kindex show struct-convention
23777 Show the current setting of the convention to return @code{struct}s
23782 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
23783 @cindex Intel Memory Protection Extensions (MPX).
23785 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
23786 @footnote{The register named with capital letters represent the architecture
23787 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
23788 which are the lower bound and upper bound. Bounds are effective addresses or
23789 memory locations. The upper bounds are architecturally represented in 1's
23790 complement form. A bound having lower bound = 0, and upper bound = 0
23791 (1's complement of all bits set) will allow access to the entire address space.
23793 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
23794 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
23795 display the upper bound performing the complement of one operation on the
23796 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
23797 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
23798 can also be noted that the upper bounds are inclusive.
23800 As an example, assume that the register BND0 holds bounds for a pointer having
23801 access allowed for the range between 0x32 and 0x71. The values present on
23802 bnd0raw and bnd registers are presented as follows:
23805 bnd0raw = @{0x32, 0xffffffff8e@}
23806 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
23809 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
23810 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
23811 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
23812 Python, the display includes the memory size, in bits, accessible to
23815 Bounds can also be stored in bounds tables, which are stored in
23816 application memory. These tables store bounds for pointers by specifying
23817 the bounds pointer's value along with its bounds. Evaluating and changing
23818 bounds located in bound tables is therefore interesting while investigating
23819 bugs on MPX context. @value{GDBN} provides commands for this purpose:
23822 @item show mpx bound @var{pointer}
23823 @kindex show mpx bound
23824 Display bounds of the given @var{pointer}.
23826 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
23827 @kindex set mpx bound
23828 Set the bounds of a pointer in the bound table.
23829 This command takes three parameters: @var{pointer} is the pointers
23830 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
23831 for lower and upper bounds respectively.
23834 When you call an inferior function on an Intel MPX enabled program,
23835 GDB sets the inferior's bound registers to the init (disabled) state
23836 before calling the function. As a consequence, bounds checks for the
23837 pointer arguments passed to the function will always pass.
23839 This is necessary because when you call an inferior function, the
23840 program is usually in the middle of the execution of other function.
23841 Since at that point bound registers are in an arbitrary state, not
23842 clearing them would lead to random bound violations in the called
23845 You can still examine the influence of the bound registers on the
23846 execution of the called function by stopping the execution of the
23847 called function at its prologue, setting bound registers, and
23848 continuing the execution. For example:
23852 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
23853 $ print upper (a, b, c, d, 1)
23854 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
23856 @{lbound = 0x0, ubound = ffffffff@} : size -1
23859 At this last step the value of bnd0 can be changed for investigation of bound
23860 violations caused along the execution of the call. In order to know how to
23861 set the bound registers or bound table for the call consult the ABI.
23866 See the following section.
23869 @subsection @acronym{MIPS}
23871 @cindex stack on Alpha
23872 @cindex stack on @acronym{MIPS}
23873 @cindex Alpha stack
23874 @cindex @acronym{MIPS} stack
23875 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
23876 sometimes requires @value{GDBN} to search backward in the object code to
23877 find the beginning of a function.
23879 @cindex response time, @acronym{MIPS} debugging
23880 To improve response time (especially for embedded applications, where
23881 @value{GDBN} may be restricted to a slow serial line for this search)
23882 you may want to limit the size of this search, using one of these
23886 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
23887 @item set heuristic-fence-post @var{limit}
23888 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
23889 search for the beginning of a function. A value of @var{0} (the
23890 default) means there is no limit. However, except for @var{0}, the
23891 larger the limit the more bytes @code{heuristic-fence-post} must search
23892 and therefore the longer it takes to run. You should only need to use
23893 this command when debugging a stripped executable.
23895 @item show heuristic-fence-post
23896 Display the current limit.
23900 These commands are available @emph{only} when @value{GDBN} is configured
23901 for debugging programs on Alpha or @acronym{MIPS} processors.
23903 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
23907 @item set mips abi @var{arg}
23908 @kindex set mips abi
23909 @cindex set ABI for @acronym{MIPS}
23910 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
23911 values of @var{arg} are:
23915 The default ABI associated with the current binary (this is the
23925 @item show mips abi
23926 @kindex show mips abi
23927 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
23929 @item set mips compression @var{arg}
23930 @kindex set mips compression
23931 @cindex code compression, @acronym{MIPS}
23932 Tell @value{GDBN} which @acronym{MIPS} compressed
23933 @acronym{ISA, Instruction Set Architecture} encoding is used by the
23934 inferior. @value{GDBN} uses this for code disassembly and other
23935 internal interpretation purposes. This setting is only referred to
23936 when no executable has been associated with the debugging session or
23937 the executable does not provide information about the encoding it uses.
23938 Otherwise this setting is automatically updated from information
23939 provided by the executable.
23941 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
23942 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
23943 executables containing @acronym{MIPS16} code frequently are not
23944 identified as such.
23946 This setting is ``sticky''; that is, it retains its value across
23947 debugging sessions until reset either explicitly with this command or
23948 implicitly from an executable.
23950 The compiler and/or assembler typically add symbol table annotations to
23951 identify functions compiled for the @acronym{MIPS16} or
23952 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
23953 are present, @value{GDBN} uses them in preference to the global
23954 compressed @acronym{ISA} encoding setting.
23956 @item show mips compression
23957 @kindex show mips compression
23958 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
23959 @value{GDBN} to debug the inferior.
23962 @itemx show mipsfpu
23963 @xref{MIPS Embedded, set mipsfpu}.
23965 @item set mips mask-address @var{arg}
23966 @kindex set mips mask-address
23967 @cindex @acronym{MIPS} addresses, masking
23968 This command determines whether the most-significant 32 bits of 64-bit
23969 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
23970 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
23971 setting, which lets @value{GDBN} determine the correct value.
23973 @item show mips mask-address
23974 @kindex show mips mask-address
23975 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
23978 @item set remote-mips64-transfers-32bit-regs
23979 @kindex set remote-mips64-transfers-32bit-regs
23980 This command controls compatibility with 64-bit @acronym{MIPS} targets that
23981 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
23982 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
23983 and 64 bits for other registers, set this option to @samp{on}.
23985 @item show remote-mips64-transfers-32bit-regs
23986 @kindex show remote-mips64-transfers-32bit-regs
23987 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
23989 @item set debug mips
23990 @kindex set debug mips
23991 This command turns on and off debugging messages for the @acronym{MIPS}-specific
23992 target code in @value{GDBN}.
23994 @item show debug mips
23995 @kindex show debug mips
23996 Show the current setting of @acronym{MIPS} debugging messages.
24002 @cindex HPPA support
24004 When @value{GDBN} is debugging the HP PA architecture, it provides the
24005 following special commands:
24008 @item set debug hppa
24009 @kindex set debug hppa
24010 This command determines whether HPPA architecture-specific debugging
24011 messages are to be displayed.
24013 @item show debug hppa
24014 Show whether HPPA debugging messages are displayed.
24016 @item maint print unwind @var{address}
24017 @kindex maint print unwind@r{, HPPA}
24018 This command displays the contents of the unwind table entry at the
24019 given @var{address}.
24025 @subsection Cell Broadband Engine SPU architecture
24026 @cindex Cell Broadband Engine
24029 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
24030 it provides the following special commands:
24033 @item info spu event
24035 Display SPU event facility status. Shows current event mask
24036 and pending event status.
24038 @item info spu signal
24039 Display SPU signal notification facility status. Shows pending
24040 signal-control word and signal notification mode of both signal
24041 notification channels.
24043 @item info spu mailbox
24044 Display SPU mailbox facility status. Shows all pending entries,
24045 in order of processing, in each of the SPU Write Outbound,
24046 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
24049 Display MFC DMA status. Shows all pending commands in the MFC
24050 DMA queue. For each entry, opcode, tag, class IDs, effective
24051 and local store addresses and transfer size are shown.
24053 @item info spu proxydma
24054 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
24055 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
24056 and local store addresses and transfer size are shown.
24060 When @value{GDBN} is debugging a combined PowerPC/SPU application
24061 on the Cell Broadband Engine, it provides in addition the following
24065 @item set spu stop-on-load @var{arg}
24067 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
24068 will give control to the user when a new SPE thread enters its @code{main}
24069 function. The default is @code{off}.
24071 @item show spu stop-on-load
24073 Show whether to stop for new SPE threads.
24075 @item set spu auto-flush-cache @var{arg}
24076 Set whether to automatically flush the software-managed cache. When set to
24077 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
24078 cache to be flushed whenever SPE execution stops. This provides a consistent
24079 view of PowerPC memory that is accessed via the cache. If an application
24080 does not use the software-managed cache, this option has no effect.
24082 @item show spu auto-flush-cache
24083 Show whether to automatically flush the software-managed cache.
24088 @subsection PowerPC
24089 @cindex PowerPC architecture
24091 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
24092 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
24093 numbers stored in the floating point registers. These values must be stored
24094 in two consecutive registers, always starting at an even register like
24095 @code{f0} or @code{f2}.
24097 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
24098 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
24099 @code{f2} and @code{f3} for @code{$dl1} and so on.
24101 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
24102 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
24105 @subsection Nios II
24106 @cindex Nios II architecture
24108 When @value{GDBN} is debugging the Nios II architecture,
24109 it provides the following special commands:
24113 @item set debug nios2
24114 @kindex set debug nios2
24115 This command turns on and off debugging messages for the Nios II
24116 target code in @value{GDBN}.
24118 @item show debug nios2
24119 @kindex show debug nios2
24120 Show the current setting of Nios II debugging messages.
24124 @subsection Sparc64
24125 @cindex Sparc64 support
24126 @cindex Application Data Integrity
24127 @subsubsection ADI Support
24129 The M7 processor supports an Application Data Integrity (ADI) feature that
24130 detects invalid data accesses. When software allocates memory and enables
24131 ADI on the allocated memory, it chooses a 4-bit version number, sets the
24132 version in the upper 4 bits of the 64-bit pointer to that data, and stores
24133 the 4-bit version in every cacheline of that data. Hardware saves the latter
24134 in spare bits in the cache and memory hierarchy. On each load and store,
24135 the processor compares the upper 4 VA (virtual address) bits to the
24136 cacheline's version. If there is a mismatch, the processor generates a
24137 version mismatch trap which can be either precise or disrupting. The trap
24138 is an error condition which the kernel delivers to the process as a SIGSEGV
24141 Note that only 64-bit applications can use ADI and need to be built with
24144 Values of the ADI version tags, which are in granularity of a
24145 cacheline (64 bytes), can be viewed or modified.
24149 @kindex adi examine
24150 @item adi (examine | x) [ / @var{n} ] @var{addr}
24152 The @code{adi examine} command displays the value of one ADI version tag per
24155 @var{n} is a decimal integer specifying the number in bytes; the default
24156 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
24157 block size, to display.
24159 @var{addr} is the address in user address space where you want @value{GDBN}
24160 to begin displaying the ADI version tags.
24162 Below is an example of displaying ADI versions of variable "shmaddr".
24165 (@value{GDBP}) adi x/100 shmaddr
24166 0xfff800010002c000: 0 0
24170 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
24172 The @code{adi assign} command is used to assign new ADI version tag
24175 @var{n} is a decimal integer specifying the number in bytes;
24176 the default is 1. It specifies how much ADI version information, at the
24177 ratio of 1:ADI block size, to modify.
24179 @var{addr} is the address in user address space where you want @value{GDBN}
24180 to begin modifying the ADI version tags.
24182 @var{tag} is the new ADI version tag.
24184 For example, do the following to modify then verify ADI versions of
24185 variable "shmaddr":
24188 (@value{GDBP}) adi a/100 shmaddr = 7
24189 (@value{GDBP}) adi x/100 shmaddr
24190 0xfff800010002c000: 7 7
24197 @cindex S12Z support
24199 When @value{GDBN} is debugging the S12Z architecture,
24200 it provides the following special command:
24203 @item maint info bdccsr
24204 @kindex maint info bdccsr@r{, S12Z}
24205 This command displays the current value of the microprocessor's
24210 @node Controlling GDB
24211 @chapter Controlling @value{GDBN}
24213 You can alter the way @value{GDBN} interacts with you by using the
24214 @code{set} command. For commands controlling how @value{GDBN} displays
24215 data, see @ref{Print Settings, ,Print Settings}. Other settings are
24220 * Editing:: Command editing
24221 * Command History:: Command history
24222 * Screen Size:: Screen size
24223 * Output Styling:: Output styling
24224 * Numbers:: Numbers
24225 * ABI:: Configuring the current ABI
24226 * Auto-loading:: Automatically loading associated files
24227 * Messages/Warnings:: Optional warnings and messages
24228 * Debugging Output:: Optional messages about internal happenings
24229 * Other Misc Settings:: Other Miscellaneous Settings
24237 @value{GDBN} indicates its readiness to read a command by printing a string
24238 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
24239 can change the prompt string with the @code{set prompt} command. For
24240 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
24241 the prompt in one of the @value{GDBN} sessions so that you can always tell
24242 which one you are talking to.
24244 @emph{Note:} @code{set prompt} does not add a space for you after the
24245 prompt you set. This allows you to set a prompt which ends in a space
24246 or a prompt that does not.
24250 @item set prompt @var{newprompt}
24251 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
24253 @kindex show prompt
24255 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
24258 Versions of @value{GDBN} that ship with Python scripting enabled have
24259 prompt extensions. The commands for interacting with these extensions
24263 @kindex set extended-prompt
24264 @item set extended-prompt @var{prompt}
24265 Set an extended prompt that allows for substitutions.
24266 @xref{gdb.prompt}, for a list of escape sequences that can be used for
24267 substitution. Any escape sequences specified as part of the prompt
24268 string are replaced with the corresponding strings each time the prompt
24274 set extended-prompt Current working directory: \w (gdb)
24277 Note that when an extended-prompt is set, it takes control of the
24278 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
24280 @kindex show extended-prompt
24281 @item show extended-prompt
24282 Prints the extended prompt. Any escape sequences specified as part of
24283 the prompt string with @code{set extended-prompt}, are replaced with the
24284 corresponding strings each time the prompt is displayed.
24288 @section Command Editing
24290 @cindex command line editing
24292 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
24293 @sc{gnu} library provides consistent behavior for programs which provide a
24294 command line interface to the user. Advantages are @sc{gnu} Emacs-style
24295 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
24296 substitution, and a storage and recall of command history across
24297 debugging sessions.
24299 You may control the behavior of command line editing in @value{GDBN} with the
24300 command @code{set}.
24303 @kindex set editing
24306 @itemx set editing on
24307 Enable command line editing (enabled by default).
24309 @item set editing off
24310 Disable command line editing.
24312 @kindex show editing
24314 Show whether command line editing is enabled.
24317 @ifset SYSTEM_READLINE
24318 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
24320 @ifclear SYSTEM_READLINE
24321 @xref{Command Line Editing},
24323 for more details about the Readline
24324 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
24325 encouraged to read that chapter.
24327 @node Command History
24328 @section Command History
24329 @cindex command history
24331 @value{GDBN} can keep track of the commands you type during your
24332 debugging sessions, so that you can be certain of precisely what
24333 happened. Use these commands to manage the @value{GDBN} command
24336 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
24337 package, to provide the history facility.
24338 @ifset SYSTEM_READLINE
24339 @xref{Using History Interactively, , , history, GNU History Library},
24341 @ifclear SYSTEM_READLINE
24342 @xref{Using History Interactively},
24344 for the detailed description of the History library.
24346 To issue a command to @value{GDBN} without affecting certain aspects of
24347 the state which is seen by users, prefix it with @samp{server }
24348 (@pxref{Server Prefix}). This
24349 means that this command will not affect the command history, nor will it
24350 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
24351 pressed on a line by itself.
24353 @cindex @code{server}, command prefix
24354 The server prefix does not affect the recording of values into the value
24355 history; to print a value without recording it into the value history,
24356 use the @code{output} command instead of the @code{print} command.
24358 Here is the description of @value{GDBN} commands related to command
24362 @cindex history substitution
24363 @cindex history file
24364 @kindex set history filename
24365 @cindex @env{GDBHISTFILE}, environment variable
24366 @item set history filename @var{fname}
24367 Set the name of the @value{GDBN} command history file to @var{fname}.
24368 This is the file where @value{GDBN} reads an initial command history
24369 list, and where it writes the command history from this session when it
24370 exits. You can access this list through history expansion or through
24371 the history command editing characters listed below. This file defaults
24372 to the value of the environment variable @code{GDBHISTFILE}, or to
24373 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
24376 @cindex save command history
24377 @kindex set history save
24378 @item set history save
24379 @itemx set history save on
24380 Record command history in a file, whose name may be specified with the
24381 @code{set history filename} command. By default, this option is disabled.
24383 @item set history save off
24384 Stop recording command history in a file.
24386 @cindex history size
24387 @kindex set history size
24388 @cindex @env{GDBHISTSIZE}, environment variable
24389 @item set history size @var{size}
24390 @itemx set history size unlimited
24391 Set the number of commands which @value{GDBN} keeps in its history list.
24392 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
24393 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
24394 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
24395 either a negative number or the empty string, then the number of commands
24396 @value{GDBN} keeps in the history list is unlimited.
24398 @cindex remove duplicate history
24399 @kindex set history remove-duplicates
24400 @item set history remove-duplicates @var{count}
24401 @itemx set history remove-duplicates unlimited
24402 Control the removal of duplicate history entries in the command history list.
24403 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
24404 history entries and remove the first entry that is a duplicate of the current
24405 entry being added to the command history list. If @var{count} is
24406 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
24407 removal of duplicate history entries is disabled.
24409 Only history entries added during the current session are considered for
24410 removal. This option is set to 0 by default.
24414 History expansion assigns special meaning to the character @kbd{!}.
24415 @ifset SYSTEM_READLINE
24416 @xref{Event Designators, , , history, GNU History Library},
24418 @ifclear SYSTEM_READLINE
24419 @xref{Event Designators},
24423 @cindex history expansion, turn on/off
24424 Since @kbd{!} is also the logical not operator in C, history expansion
24425 is off by default. If you decide to enable history expansion with the
24426 @code{set history expansion on} command, you may sometimes need to
24427 follow @kbd{!} (when it is used as logical not, in an expression) with
24428 a space or a tab to prevent it from being expanded. The readline
24429 history facilities do not attempt substitution on the strings
24430 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
24432 The commands to control history expansion are:
24435 @item set history expansion on
24436 @itemx set history expansion
24437 @kindex set history expansion
24438 Enable history expansion. History expansion is off by default.
24440 @item set history expansion off
24441 Disable history expansion.
24444 @kindex show history
24446 @itemx show history filename
24447 @itemx show history save
24448 @itemx show history size
24449 @itemx show history expansion
24450 These commands display the state of the @value{GDBN} history parameters.
24451 @code{show history} by itself displays all four states.
24456 @kindex show commands
24457 @cindex show last commands
24458 @cindex display command history
24459 @item show commands
24460 Display the last ten commands in the command history.
24462 @item show commands @var{n}
24463 Print ten commands centered on command number @var{n}.
24465 @item show commands +
24466 Print ten commands just after the commands last printed.
24470 @section Screen Size
24471 @cindex size of screen
24472 @cindex screen size
24475 @cindex pauses in output
24477 Certain commands to @value{GDBN} may produce large amounts of
24478 information output to the screen. To help you read all of it,
24479 @value{GDBN} pauses and asks you for input at the end of each page of
24480 output. Type @key{RET} when you want to see one more page of output,
24481 @kbd{q} to discard the remaining output, or @kbd{c} to continue
24482 without paging for the rest of the current command. Also, the screen
24483 width setting determines when to wrap lines of output. Depending on
24484 what is being printed, @value{GDBN} tries to break the line at a
24485 readable place, rather than simply letting it overflow onto the
24488 Normally @value{GDBN} knows the size of the screen from the terminal
24489 driver software. For example, on Unix @value{GDBN} uses the termcap data base
24490 together with the value of the @code{TERM} environment variable and the
24491 @code{stty rows} and @code{stty cols} settings. If this is not correct,
24492 you can override it with the @code{set height} and @code{set
24499 @kindex show height
24500 @item set height @var{lpp}
24501 @itemx set height unlimited
24503 @itemx set width @var{cpl}
24504 @itemx set width unlimited
24506 These @code{set} commands specify a screen height of @var{lpp} lines and
24507 a screen width of @var{cpl} characters. The associated @code{show}
24508 commands display the current settings.
24510 If you specify a height of either @code{unlimited} or zero lines,
24511 @value{GDBN} does not pause during output no matter how long the
24512 output is. This is useful if output is to a file or to an editor
24515 Likewise, you can specify @samp{set width unlimited} or @samp{set
24516 width 0} to prevent @value{GDBN} from wrapping its output.
24518 @item set pagination on
24519 @itemx set pagination off
24520 @kindex set pagination
24521 Turn the output pagination on or off; the default is on. Turning
24522 pagination off is the alternative to @code{set height unlimited}. Note that
24523 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
24524 Options, -batch}) also automatically disables pagination.
24526 @item show pagination
24527 @kindex show pagination
24528 Show the current pagination mode.
24531 @node Output Styling
24532 @section Output Styling
24538 @value{GDBN} can style its output on a capable terminal. This is
24539 enabled by default on most systems, but disabled by default when in
24540 batch mode (@pxref{Mode Options}). Various style settings are available;
24541 and styles can also be disabled entirely.
24544 @item set style enabled @samp{on|off}
24545 Enable or disable all styling. The default is host-dependent, with
24546 most hosts defaulting to @samp{on}.
24548 @item show style enabled
24549 Show the current state of styling.
24551 @item set style sources @samp{on|off}
24552 Enable or disable source code styling. This affects whether source
24553 code, such as the output of the @code{list} command, is styled. Note
24554 that source styling only works if styling in general is enabled, and
24555 if @value{GDBN} was linked with the GNU Source Highlight library. The
24556 default is @samp{on}.
24558 @item show style sources
24559 Show the current state of source code styling.
24562 Subcommands of @code{set style} control specific forms of styling.
24563 These subcommands all follow the same pattern: each style-able object
24564 can be styled with a foreground color, a background color, and an
24567 For example, the style of file names can be controlled using the
24568 @code{set style filename} group of commands:
24571 @item set style filename background @var{color}
24572 Set the background to @var{color}. Valid colors are @samp{none}
24573 (meaning the terminal's default color), @samp{black}, @samp{red},
24574 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
24577 @item set style filename foreground @var{color}
24578 Set the foreground to @var{color}. Valid colors are @samp{none}
24579 (meaning the terminal's default color), @samp{black}, @samp{red},
24580 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
24583 @item set style filename intensity @var{value}
24584 Set the intensity to @var{value}. Valid intensities are @samp{normal}
24585 (the default), @samp{bold}, and @samp{dim}.
24588 The style-able objects are:
24591 Control the styling of file names. By default, this style's
24592 foreground color is green.
24595 Control the styling of function names. These are managed with the
24596 @code{set style function} family of commands. By default, this
24597 style's foreground color is yellow.
24600 Control the styling of variable names. These are managed with the
24601 @code{set style variable} family of commands. By default, this style's
24602 foreground color is cyan.
24605 Control the styling of addresses. These are managed with the
24606 @code{set style address} family of commands. By default, this style's
24607 foreground color is blue.
24612 @cindex number representation
24613 @cindex entering numbers
24615 You can always enter numbers in octal, decimal, or hexadecimal in
24616 @value{GDBN} by the usual conventions: octal numbers begin with
24617 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
24618 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
24619 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
24620 10; likewise, the default display for numbers---when no particular
24621 format is specified---is base 10. You can change the default base for
24622 both input and output with the commands described below.
24625 @kindex set input-radix
24626 @item set input-radix @var{base}
24627 Set the default base for numeric input. Supported choices
24628 for @var{base} are decimal 8, 10, or 16. The base must itself be
24629 specified either unambiguously or using the current input radix; for
24633 set input-radix 012
24634 set input-radix 10.
24635 set input-radix 0xa
24639 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
24640 leaves the input radix unchanged, no matter what it was, since
24641 @samp{10}, being without any leading or trailing signs of its base, is
24642 interpreted in the current radix. Thus, if the current radix is 16,
24643 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
24646 @kindex set output-radix
24647 @item set output-radix @var{base}
24648 Set the default base for numeric display. Supported choices
24649 for @var{base} are decimal 8, 10, or 16. The base must itself be
24650 specified either unambiguously or using the current input radix.
24652 @kindex show input-radix
24653 @item show input-radix
24654 Display the current default base for numeric input.
24656 @kindex show output-radix
24657 @item show output-radix
24658 Display the current default base for numeric display.
24660 @item set radix @r{[}@var{base}@r{]}
24664 These commands set and show the default base for both input and output
24665 of numbers. @code{set radix} sets the radix of input and output to
24666 the same base; without an argument, it resets the radix back to its
24667 default value of 10.
24672 @section Configuring the Current ABI
24674 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
24675 application automatically. However, sometimes you need to override its
24676 conclusions. Use these commands to manage @value{GDBN}'s view of the
24682 @cindex Newlib OS ABI and its influence on the longjmp handling
24684 One @value{GDBN} configuration can debug binaries for multiple operating
24685 system targets, either via remote debugging or native emulation.
24686 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
24687 but you can override its conclusion using the @code{set osabi} command.
24688 One example where this is useful is in debugging of binaries which use
24689 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
24690 not have the same identifying marks that the standard C library for your
24693 When @value{GDBN} is debugging the AArch64 architecture, it provides a
24694 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
24695 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
24696 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
24700 Show the OS ABI currently in use.
24703 With no argument, show the list of registered available OS ABI's.
24705 @item set osabi @var{abi}
24706 Set the current OS ABI to @var{abi}.
24709 @cindex float promotion
24711 Generally, the way that an argument of type @code{float} is passed to a
24712 function depends on whether the function is prototyped. For a prototyped
24713 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
24714 according to the architecture's convention for @code{float}. For unprototyped
24715 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
24716 @code{double} and then passed.
24718 Unfortunately, some forms of debug information do not reliably indicate whether
24719 a function is prototyped. If @value{GDBN} calls a function that is not marked
24720 as prototyped, it consults @kbd{set coerce-float-to-double}.
24723 @kindex set coerce-float-to-double
24724 @item set coerce-float-to-double
24725 @itemx set coerce-float-to-double on
24726 Arguments of type @code{float} will be promoted to @code{double} when passed
24727 to an unprototyped function. This is the default setting.
24729 @item set coerce-float-to-double off
24730 Arguments of type @code{float} will be passed directly to unprototyped
24733 @kindex show coerce-float-to-double
24734 @item show coerce-float-to-double
24735 Show the current setting of promoting @code{float} to @code{double}.
24739 @kindex show cp-abi
24740 @value{GDBN} needs to know the ABI used for your program's C@t{++}
24741 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
24742 used to build your application. @value{GDBN} only fully supports
24743 programs with a single C@t{++} ABI; if your program contains code using
24744 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
24745 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
24746 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
24747 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
24748 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
24749 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
24754 Show the C@t{++} ABI currently in use.
24757 With no argument, show the list of supported C@t{++} ABI's.
24759 @item set cp-abi @var{abi}
24760 @itemx set cp-abi auto
24761 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
24765 @section Automatically loading associated files
24766 @cindex auto-loading
24768 @value{GDBN} sometimes reads files with commands and settings automatically,
24769 without being explicitly told so by the user. We call this feature
24770 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
24771 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
24772 results or introduce security risks (e.g., if the file comes from untrusted
24776 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
24777 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
24779 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
24780 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
24783 There are various kinds of files @value{GDBN} can automatically load.
24784 In addition to these files, @value{GDBN} supports auto-loading code written
24785 in various extension languages. @xref{Auto-loading extensions}.
24787 Note that loading of these associated files (including the local @file{.gdbinit}
24788 file) requires accordingly configured @code{auto-load safe-path}
24789 (@pxref{Auto-loading safe path}).
24791 For these reasons, @value{GDBN} includes commands and options to let you
24792 control when to auto-load files and which files should be auto-loaded.
24795 @anchor{set auto-load off}
24796 @kindex set auto-load off
24797 @item set auto-load off
24798 Globally disable loading of all auto-loaded files.
24799 You may want to use this command with the @samp{-iex} option
24800 (@pxref{Option -init-eval-command}) such as:
24802 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
24805 Be aware that system init file (@pxref{System-wide configuration})
24806 and init files from your home directory (@pxref{Home Directory Init File})
24807 still get read (as they come from generally trusted directories).
24808 To prevent @value{GDBN} from auto-loading even those init files, use the
24809 @option{-nx} option (@pxref{Mode Options}), in addition to
24810 @code{set auto-load no}.
24812 @anchor{show auto-load}
24813 @kindex show auto-load
24814 @item show auto-load
24815 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
24819 (gdb) show auto-load
24820 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
24821 libthread-db: Auto-loading of inferior specific libthread_db is on.
24822 local-gdbinit: Auto-loading of .gdbinit script from current directory
24824 python-scripts: Auto-loading of Python scripts is on.
24825 safe-path: List of directories from which it is safe to auto-load files
24826 is $debugdir:$datadir/auto-load.
24827 scripts-directory: List of directories from which to load auto-loaded scripts
24828 is $debugdir:$datadir/auto-load.
24831 @anchor{info auto-load}
24832 @kindex info auto-load
24833 @item info auto-load
24834 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
24838 (gdb) info auto-load
24841 Yes /home/user/gdb/gdb-gdb.gdb
24842 libthread-db: No auto-loaded libthread-db.
24843 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
24847 Yes /home/user/gdb/gdb-gdb.py
24851 These are @value{GDBN} control commands for the auto-loading:
24853 @multitable @columnfractions .5 .5
24854 @item @xref{set auto-load off}.
24855 @tab Disable auto-loading globally.
24856 @item @xref{show auto-load}.
24857 @tab Show setting of all kinds of files.
24858 @item @xref{info auto-load}.
24859 @tab Show state of all kinds of files.
24860 @item @xref{set auto-load gdb-scripts}.
24861 @tab Control for @value{GDBN} command scripts.
24862 @item @xref{show auto-load gdb-scripts}.
24863 @tab Show setting of @value{GDBN} command scripts.
24864 @item @xref{info auto-load gdb-scripts}.
24865 @tab Show state of @value{GDBN} command scripts.
24866 @item @xref{set auto-load python-scripts}.
24867 @tab Control for @value{GDBN} Python scripts.
24868 @item @xref{show auto-load python-scripts}.
24869 @tab Show setting of @value{GDBN} Python scripts.
24870 @item @xref{info auto-load python-scripts}.
24871 @tab Show state of @value{GDBN} Python scripts.
24872 @item @xref{set auto-load guile-scripts}.
24873 @tab Control for @value{GDBN} Guile scripts.
24874 @item @xref{show auto-load guile-scripts}.
24875 @tab Show setting of @value{GDBN} Guile scripts.
24876 @item @xref{info auto-load guile-scripts}.
24877 @tab Show state of @value{GDBN} Guile scripts.
24878 @item @xref{set auto-load scripts-directory}.
24879 @tab Control for @value{GDBN} auto-loaded scripts location.
24880 @item @xref{show auto-load scripts-directory}.
24881 @tab Show @value{GDBN} auto-loaded scripts location.
24882 @item @xref{add-auto-load-scripts-directory}.
24883 @tab Add directory for auto-loaded scripts location list.
24884 @item @xref{set auto-load local-gdbinit}.
24885 @tab Control for init file in the current directory.
24886 @item @xref{show auto-load local-gdbinit}.
24887 @tab Show setting of init file in the current directory.
24888 @item @xref{info auto-load local-gdbinit}.
24889 @tab Show state of init file in the current directory.
24890 @item @xref{set auto-load libthread-db}.
24891 @tab Control for thread debugging library.
24892 @item @xref{show auto-load libthread-db}.
24893 @tab Show setting of thread debugging library.
24894 @item @xref{info auto-load libthread-db}.
24895 @tab Show state of thread debugging library.
24896 @item @xref{set auto-load safe-path}.
24897 @tab Control directories trusted for automatic loading.
24898 @item @xref{show auto-load safe-path}.
24899 @tab Show directories trusted for automatic loading.
24900 @item @xref{add-auto-load-safe-path}.
24901 @tab Add directory trusted for automatic loading.
24904 @node Init File in the Current Directory
24905 @subsection Automatically loading init file in the current directory
24906 @cindex auto-loading init file in the current directory
24908 By default, @value{GDBN} reads and executes the canned sequences of commands
24909 from init file (if any) in the current working directory,
24910 see @ref{Init File in the Current Directory during Startup}.
24912 Note that loading of this local @file{.gdbinit} file also requires accordingly
24913 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24916 @anchor{set auto-load local-gdbinit}
24917 @kindex set auto-load local-gdbinit
24918 @item set auto-load local-gdbinit [on|off]
24919 Enable or disable the auto-loading of canned sequences of commands
24920 (@pxref{Sequences}) found in init file in the current directory.
24922 @anchor{show auto-load local-gdbinit}
24923 @kindex show auto-load local-gdbinit
24924 @item show auto-load local-gdbinit
24925 Show whether auto-loading of canned sequences of commands from init file in the
24926 current directory is enabled or disabled.
24928 @anchor{info auto-load local-gdbinit}
24929 @kindex info auto-load local-gdbinit
24930 @item info auto-load local-gdbinit
24931 Print whether canned sequences of commands from init file in the
24932 current directory have been auto-loaded.
24935 @node libthread_db.so.1 file
24936 @subsection Automatically loading thread debugging library
24937 @cindex auto-loading libthread_db.so.1
24939 This feature is currently present only on @sc{gnu}/Linux native hosts.
24941 @value{GDBN} reads in some cases thread debugging library from places specific
24942 to the inferior (@pxref{set libthread-db-search-path}).
24944 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
24945 without checking this @samp{set auto-load libthread-db} switch as system
24946 libraries have to be trusted in general. In all other cases of
24947 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
24948 auto-load libthread-db} is enabled before trying to open such thread debugging
24951 Note that loading of this debugging library also requires accordingly configured
24952 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24955 @anchor{set auto-load libthread-db}
24956 @kindex set auto-load libthread-db
24957 @item set auto-load libthread-db [on|off]
24958 Enable or disable the auto-loading of inferior specific thread debugging library.
24960 @anchor{show auto-load libthread-db}
24961 @kindex show auto-load libthread-db
24962 @item show auto-load libthread-db
24963 Show whether auto-loading of inferior specific thread debugging library is
24964 enabled or disabled.
24966 @anchor{info auto-load libthread-db}
24967 @kindex info auto-load libthread-db
24968 @item info auto-load libthread-db
24969 Print the list of all loaded inferior specific thread debugging libraries and
24970 for each such library print list of inferior @var{pid}s using it.
24973 @node Auto-loading safe path
24974 @subsection Security restriction for auto-loading
24975 @cindex auto-loading safe-path
24977 As the files of inferior can come from untrusted source (such as submitted by
24978 an application user) @value{GDBN} does not always load any files automatically.
24979 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
24980 directories trusted for loading files not explicitly requested by user.
24981 Each directory can also be a shell wildcard pattern.
24983 If the path is not set properly you will see a warning and the file will not
24988 Reading symbols from /home/user/gdb/gdb...done.
24989 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
24990 declined by your `auto-load safe-path' set
24991 to "$debugdir:$datadir/auto-load".
24992 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
24993 declined by your `auto-load safe-path' set
24994 to "$debugdir:$datadir/auto-load".
24998 To instruct @value{GDBN} to go ahead and use the init files anyway,
24999 invoke @value{GDBN} like this:
25002 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
25005 The list of trusted directories is controlled by the following commands:
25008 @anchor{set auto-load safe-path}
25009 @kindex set auto-load safe-path
25010 @item set auto-load safe-path @r{[}@var{directories}@r{]}
25011 Set the list of directories (and their subdirectories) trusted for automatic
25012 loading and execution of scripts. You can also enter a specific trusted file.
25013 Each directory can also be a shell wildcard pattern; wildcards do not match
25014 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
25015 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
25016 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
25017 its default value as specified during @value{GDBN} compilation.
25019 The list of directories uses path separator (@samp{:} on GNU and Unix
25020 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25021 to the @env{PATH} environment variable.
25023 @anchor{show auto-load safe-path}
25024 @kindex show auto-load safe-path
25025 @item show auto-load safe-path
25026 Show the list of directories trusted for automatic loading and execution of
25029 @anchor{add-auto-load-safe-path}
25030 @kindex add-auto-load-safe-path
25031 @item add-auto-load-safe-path
25032 Add an entry (or list of entries) to the list of directories trusted for
25033 automatic loading and execution of scripts. Multiple entries may be delimited
25034 by the host platform path separator in use.
25037 This variable defaults to what @code{--with-auto-load-dir} has been configured
25038 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
25039 substitution applies the same as for @ref{set auto-load scripts-directory}.
25040 The default @code{set auto-load safe-path} value can be also overriden by
25041 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
25043 Setting this variable to @file{/} disables this security protection,
25044 corresponding @value{GDBN} configuration option is
25045 @option{--without-auto-load-safe-path}.
25046 This variable is supposed to be set to the system directories writable by the
25047 system superuser only. Users can add their source directories in init files in
25048 their home directories (@pxref{Home Directory Init File}). See also deprecated
25049 init file in the current directory
25050 (@pxref{Init File in the Current Directory during Startup}).
25052 To force @value{GDBN} to load the files it declined to load in the previous
25053 example, you could use one of the following ways:
25056 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
25057 Specify this trusted directory (or a file) as additional component of the list.
25058 You have to specify also any existing directories displayed by
25059 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
25061 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
25062 Specify this directory as in the previous case but just for a single
25063 @value{GDBN} session.
25065 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
25066 Disable auto-loading safety for a single @value{GDBN} session.
25067 This assumes all the files you debug during this @value{GDBN} session will come
25068 from trusted sources.
25070 @item @kbd{./configure --without-auto-load-safe-path}
25071 During compilation of @value{GDBN} you may disable any auto-loading safety.
25072 This assumes all the files you will ever debug with this @value{GDBN} come from
25076 On the other hand you can also explicitly forbid automatic files loading which
25077 also suppresses any such warning messages:
25080 @item @kbd{gdb -iex "set auto-load no" @dots{}}
25081 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
25083 @item @file{~/.gdbinit}: @samp{set auto-load no}
25084 Disable auto-loading globally for the user
25085 (@pxref{Home Directory Init File}). While it is improbable, you could also
25086 use system init file instead (@pxref{System-wide configuration}).
25089 This setting applies to the file names as entered by user. If no entry matches
25090 @value{GDBN} tries as a last resort to also resolve all the file names into
25091 their canonical form (typically resolving symbolic links) and compare the
25092 entries again. @value{GDBN} already canonicalizes most of the filenames on its
25093 own before starting the comparison so a canonical form of directories is
25094 recommended to be entered.
25096 @node Auto-loading verbose mode
25097 @subsection Displaying files tried for auto-load
25098 @cindex auto-loading verbose mode
25100 For better visibility of all the file locations where you can place scripts to
25101 be auto-loaded with inferior --- or to protect yourself against accidental
25102 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
25103 all the files attempted to be loaded. Both existing and non-existing files may
25106 For example the list of directories from which it is safe to auto-load files
25107 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
25108 may not be too obvious while setting it up.
25111 (gdb) set debug auto-load on
25112 (gdb) file ~/src/t/true
25113 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
25114 for objfile "/tmp/true".
25115 auto-load: Updating directories of "/usr:/opt".
25116 auto-load: Using directory "/usr".
25117 auto-load: Using directory "/opt".
25118 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
25119 by your `auto-load safe-path' set to "/usr:/opt".
25123 @anchor{set debug auto-load}
25124 @kindex set debug auto-load
25125 @item set debug auto-load [on|off]
25126 Set whether to print the filenames attempted to be auto-loaded.
25128 @anchor{show debug auto-load}
25129 @kindex show debug auto-load
25130 @item show debug auto-load
25131 Show whether printing of the filenames attempted to be auto-loaded is turned
25135 @node Messages/Warnings
25136 @section Optional Warnings and Messages
25138 @cindex verbose operation
25139 @cindex optional warnings
25140 By default, @value{GDBN} is silent about its inner workings. If you are
25141 running on a slow machine, you may want to use the @code{set verbose}
25142 command. This makes @value{GDBN} tell you when it does a lengthy
25143 internal operation, so you will not think it has crashed.
25145 Currently, the messages controlled by @code{set verbose} are those
25146 which announce that the symbol table for a source file is being read;
25147 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
25150 @kindex set verbose
25151 @item set verbose on
25152 Enables @value{GDBN} output of certain informational messages.
25154 @item set verbose off
25155 Disables @value{GDBN} output of certain informational messages.
25157 @kindex show verbose
25159 Displays whether @code{set verbose} is on or off.
25162 By default, if @value{GDBN} encounters bugs in the symbol table of an
25163 object file, it is silent; but if you are debugging a compiler, you may
25164 find this information useful (@pxref{Symbol Errors, ,Errors Reading
25169 @kindex set complaints
25170 @item set complaints @var{limit}
25171 Permits @value{GDBN} to output @var{limit} complaints about each type of
25172 unusual symbols before becoming silent about the problem. Set
25173 @var{limit} to zero to suppress all complaints; set it to a large number
25174 to prevent complaints from being suppressed.
25176 @kindex show complaints
25177 @item show complaints
25178 Displays how many symbol complaints @value{GDBN} is permitted to produce.
25182 @anchor{confirmation requests}
25183 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
25184 lot of stupid questions to confirm certain commands. For example, if
25185 you try to run a program which is already running:
25189 The program being debugged has been started already.
25190 Start it from the beginning? (y or n)
25193 If you are willing to unflinchingly face the consequences of your own
25194 commands, you can disable this ``feature'':
25198 @kindex set confirm
25200 @cindex confirmation
25201 @cindex stupid questions
25202 @item set confirm off
25203 Disables confirmation requests. Note that running @value{GDBN} with
25204 the @option{--batch} option (@pxref{Mode Options, -batch}) also
25205 automatically disables confirmation requests.
25207 @item set confirm on
25208 Enables confirmation requests (the default).
25210 @kindex show confirm
25212 Displays state of confirmation requests.
25216 @cindex command tracing
25217 If you need to debug user-defined commands or sourced files you may find it
25218 useful to enable @dfn{command tracing}. In this mode each command will be
25219 printed as it is executed, prefixed with one or more @samp{+} symbols, the
25220 quantity denoting the call depth of each command.
25223 @kindex set trace-commands
25224 @cindex command scripts, debugging
25225 @item set trace-commands on
25226 Enable command tracing.
25227 @item set trace-commands off
25228 Disable command tracing.
25229 @item show trace-commands
25230 Display the current state of command tracing.
25233 @node Debugging Output
25234 @section Optional Messages about Internal Happenings
25235 @cindex optional debugging messages
25237 @value{GDBN} has commands that enable optional debugging messages from
25238 various @value{GDBN} subsystems; normally these commands are of
25239 interest to @value{GDBN} maintainers, or when reporting a bug. This
25240 section documents those commands.
25243 @kindex set exec-done-display
25244 @item set exec-done-display
25245 Turns on or off the notification of asynchronous commands'
25246 completion. When on, @value{GDBN} will print a message when an
25247 asynchronous command finishes its execution. The default is off.
25248 @kindex show exec-done-display
25249 @item show exec-done-display
25250 Displays the current setting of asynchronous command completion
25253 @cindex ARM AArch64
25254 @item set debug aarch64
25255 Turns on or off display of debugging messages related to ARM AArch64.
25256 The default is off.
25258 @item show debug aarch64
25259 Displays the current state of displaying debugging messages related to
25261 @cindex gdbarch debugging info
25262 @cindex architecture debugging info
25263 @item set debug arch
25264 Turns on or off display of gdbarch debugging info. The default is off
25265 @item show debug arch
25266 Displays the current state of displaying gdbarch debugging info.
25267 @item set debug aix-solib
25268 @cindex AIX shared library debugging
25269 Control display of debugging messages from the AIX shared library
25270 support module. The default is off.
25271 @item show debug aix-thread
25272 Show the current state of displaying AIX shared library debugging messages.
25273 @item set debug aix-thread
25274 @cindex AIX threads
25275 Display debugging messages about inner workings of the AIX thread
25277 @item show debug aix-thread
25278 Show the current state of AIX thread debugging info display.
25279 @item set debug check-physname
25281 Check the results of the ``physname'' computation. When reading DWARF
25282 debugging information for C@t{++}, @value{GDBN} attempts to compute
25283 each entity's name. @value{GDBN} can do this computation in two
25284 different ways, depending on exactly what information is present.
25285 When enabled, this setting causes @value{GDBN} to compute the names
25286 both ways and display any discrepancies.
25287 @item show debug check-physname
25288 Show the current state of ``physname'' checking.
25289 @item set debug coff-pe-read
25290 @cindex COFF/PE exported symbols
25291 Control display of debugging messages related to reading of COFF/PE
25292 exported symbols. The default is off.
25293 @item show debug coff-pe-read
25294 Displays the current state of displaying debugging messages related to
25295 reading of COFF/PE exported symbols.
25296 @item set debug dwarf-die
25298 Dump DWARF DIEs after they are read in.
25299 The value is the number of nesting levels to print.
25300 A value of zero turns off the display.
25301 @item show debug dwarf-die
25302 Show the current state of DWARF DIE debugging.
25303 @item set debug dwarf-line
25304 @cindex DWARF Line Tables
25305 Turns on or off display of debugging messages related to reading
25306 DWARF line tables. The default is 0 (off).
25307 A value of 1 provides basic information.
25308 A value greater than 1 provides more verbose information.
25309 @item show debug dwarf-line
25310 Show the current state of DWARF line table debugging.
25311 @item set debug dwarf-read
25312 @cindex DWARF Reading
25313 Turns on or off display of debugging messages related to reading
25314 DWARF debug info. The default is 0 (off).
25315 A value of 1 provides basic information.
25316 A value greater than 1 provides more verbose information.
25317 @item show debug dwarf-read
25318 Show the current state of DWARF reader debugging.
25319 @item set debug displaced
25320 @cindex displaced stepping debugging info
25321 Turns on or off display of @value{GDBN} debugging info for the
25322 displaced stepping support. The default is off.
25323 @item show debug displaced
25324 Displays the current state of displaying @value{GDBN} debugging info
25325 related to displaced stepping.
25326 @item set debug event
25327 @cindex event debugging info
25328 Turns on or off display of @value{GDBN} event debugging info. The
25330 @item show debug event
25331 Displays the current state of displaying @value{GDBN} event debugging
25333 @item set debug expression
25334 @cindex expression debugging info
25335 Turns on or off display of debugging info about @value{GDBN}
25336 expression parsing. The default is off.
25337 @item show debug expression
25338 Displays the current state of displaying debugging info about
25339 @value{GDBN} expression parsing.
25340 @item set debug fbsd-lwp
25341 @cindex FreeBSD LWP debug messages
25342 Turns on or off debugging messages from the FreeBSD LWP debug support.
25343 @item show debug fbsd-lwp
25344 Show the current state of FreeBSD LWP debugging messages.
25345 @item set debug fbsd-nat
25346 @cindex FreeBSD native target debug messages
25347 Turns on or off debugging messages from the FreeBSD native target.
25348 @item show debug fbsd-nat
25349 Show the current state of FreeBSD native target debugging messages.
25350 @item set debug frame
25351 @cindex frame debugging info
25352 Turns on or off display of @value{GDBN} frame debugging info. The
25354 @item show debug frame
25355 Displays the current state of displaying @value{GDBN} frame debugging
25357 @item set debug gnu-nat
25358 @cindex @sc{gnu}/Hurd debug messages
25359 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
25360 @item show debug gnu-nat
25361 Show the current state of @sc{gnu}/Hurd debugging messages.
25362 @item set debug infrun
25363 @cindex inferior debugging info
25364 Turns on or off display of @value{GDBN} debugging info for running the inferior.
25365 The default is off. @file{infrun.c} contains GDB's runtime state machine used
25366 for implementing operations such as single-stepping the inferior.
25367 @item show debug infrun
25368 Displays the current state of @value{GDBN} inferior debugging.
25369 @item set debug jit
25370 @cindex just-in-time compilation, debugging messages
25371 Turn on or off debugging messages from JIT debug support.
25372 @item show debug jit
25373 Displays the current state of @value{GDBN} JIT debugging.
25374 @item set debug lin-lwp
25375 @cindex @sc{gnu}/Linux LWP debug messages
25376 @cindex Linux lightweight processes
25377 Turn on or off debugging messages from the Linux LWP debug support.
25378 @item show debug lin-lwp
25379 Show the current state of Linux LWP debugging messages.
25380 @item set debug linux-namespaces
25381 @cindex @sc{gnu}/Linux namespaces debug messages
25382 Turn on or off debugging messages from the Linux namespaces debug support.
25383 @item show debug linux-namespaces
25384 Show the current state of Linux namespaces debugging messages.
25385 @item set debug mach-o
25386 @cindex Mach-O symbols processing
25387 Control display of debugging messages related to Mach-O symbols
25388 processing. The default is off.
25389 @item show debug mach-o
25390 Displays the current state of displaying debugging messages related to
25391 reading of COFF/PE exported symbols.
25392 @item set debug notification
25393 @cindex remote async notification debugging info
25394 Turn on or off debugging messages about remote async notification.
25395 The default is off.
25396 @item show debug notification
25397 Displays the current state of remote async notification debugging messages.
25398 @item set debug observer
25399 @cindex observer debugging info
25400 Turns on or off display of @value{GDBN} observer debugging. This
25401 includes info such as the notification of observable events.
25402 @item show debug observer
25403 Displays the current state of observer debugging.
25404 @item set debug overload
25405 @cindex C@t{++} overload debugging info
25406 Turns on or off display of @value{GDBN} C@t{++} overload debugging
25407 info. This includes info such as ranking of functions, etc. The default
25409 @item show debug overload
25410 Displays the current state of displaying @value{GDBN} C@t{++} overload
25412 @cindex expression parser, debugging info
25413 @cindex debug expression parser
25414 @item set debug parser
25415 Turns on or off the display of expression parser debugging output.
25416 Internally, this sets the @code{yydebug} variable in the expression
25417 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
25418 details. The default is off.
25419 @item show debug parser
25420 Show the current state of expression parser debugging.
25421 @cindex packets, reporting on stdout
25422 @cindex serial connections, debugging
25423 @cindex debug remote protocol
25424 @cindex remote protocol debugging
25425 @cindex display remote packets
25426 @item set debug remote
25427 Turns on or off display of reports on all packets sent back and forth across
25428 the serial line to the remote machine. The info is printed on the
25429 @value{GDBN} standard output stream. The default is off.
25430 @item show debug remote
25431 Displays the state of display of remote packets.
25433 @item set debug separate-debug-file
25434 Turns on or off display of debug output about separate debug file search.
25435 @item show debug separate-debug-file
25436 Displays the state of separate debug file search debug output.
25438 @item set debug serial
25439 Turns on or off display of @value{GDBN} serial debugging info. The
25441 @item show debug serial
25442 Displays the current state of displaying @value{GDBN} serial debugging
25444 @item set debug solib-frv
25445 @cindex FR-V shared-library debugging
25446 Turn on or off debugging messages for FR-V shared-library code.
25447 @item show debug solib-frv
25448 Display the current state of FR-V shared-library code debugging
25450 @item set debug symbol-lookup
25451 @cindex symbol lookup
25452 Turns on or off display of debugging messages related to symbol lookup.
25453 The default is 0 (off).
25454 A value of 1 provides basic information.
25455 A value greater than 1 provides more verbose information.
25456 @item show debug symbol-lookup
25457 Show the current state of symbol lookup debugging messages.
25458 @item set debug symfile
25459 @cindex symbol file functions
25460 Turns on or off display of debugging messages related to symbol file functions.
25461 The default is off. @xref{Files}.
25462 @item show debug symfile
25463 Show the current state of symbol file debugging messages.
25464 @item set debug symtab-create
25465 @cindex symbol table creation
25466 Turns on or off display of debugging messages related to symbol table creation.
25467 The default is 0 (off).
25468 A value of 1 provides basic information.
25469 A value greater than 1 provides more verbose information.
25470 @item show debug symtab-create
25471 Show the current state of symbol table creation debugging.
25472 @item set debug target
25473 @cindex target debugging info
25474 Turns on or off display of @value{GDBN} target debugging info. This info
25475 includes what is going on at the target level of GDB, as it happens. The
25476 default is 0. Set it to 1 to track events, and to 2 to also track the
25477 value of large memory transfers.
25478 @item show debug target
25479 Displays the current state of displaying @value{GDBN} target debugging
25481 @item set debug timestamp
25482 @cindex timestampping debugging info
25483 Turns on or off display of timestamps with @value{GDBN} debugging info.
25484 When enabled, seconds and microseconds are displayed before each debugging
25486 @item show debug timestamp
25487 Displays the current state of displaying timestamps with @value{GDBN}
25489 @item set debug varobj
25490 @cindex variable object debugging info
25491 Turns on or off display of @value{GDBN} variable object debugging
25492 info. The default is off.
25493 @item show debug varobj
25494 Displays the current state of displaying @value{GDBN} variable object
25496 @item set debug xml
25497 @cindex XML parser debugging
25498 Turn on or off debugging messages for built-in XML parsers.
25499 @item show debug xml
25500 Displays the current state of XML debugging messages.
25503 @node Other Misc Settings
25504 @section Other Miscellaneous Settings
25505 @cindex miscellaneous settings
25508 @kindex set interactive-mode
25509 @item set interactive-mode
25510 If @code{on}, forces @value{GDBN} to assume that GDB was started
25511 in a terminal. In practice, this means that @value{GDBN} should wait
25512 for the user to answer queries generated by commands entered at
25513 the command prompt. If @code{off}, forces @value{GDBN} to operate
25514 in the opposite mode, and it uses the default answers to all queries.
25515 If @code{auto} (the default), @value{GDBN} tries to determine whether
25516 its standard input is a terminal, and works in interactive-mode if it
25517 is, non-interactively otherwise.
25519 In the vast majority of cases, the debugger should be able to guess
25520 correctly which mode should be used. But this setting can be useful
25521 in certain specific cases, such as running a MinGW @value{GDBN}
25522 inside a cygwin window.
25524 @kindex show interactive-mode
25525 @item show interactive-mode
25526 Displays whether the debugger is operating in interactive mode or not.
25529 @node Extending GDB
25530 @chapter Extending @value{GDBN}
25531 @cindex extending GDB
25533 @value{GDBN} provides several mechanisms for extension.
25534 @value{GDBN} also provides the ability to automatically load
25535 extensions when it reads a file for debugging. This allows the
25536 user to automatically customize @value{GDBN} for the program
25540 * Sequences:: Canned Sequences of @value{GDBN} Commands
25541 * Python:: Extending @value{GDBN} using Python
25542 * Guile:: Extending @value{GDBN} using Guile
25543 * Auto-loading extensions:: Automatically loading extensions
25544 * Multiple Extension Languages:: Working with multiple extension languages
25545 * Aliases:: Creating new spellings of existing commands
25548 To facilitate the use of extension languages, @value{GDBN} is capable
25549 of evaluating the contents of a file. When doing so, @value{GDBN}
25550 can recognize which extension language is being used by looking at
25551 the filename extension. Files with an unrecognized filename extension
25552 are always treated as a @value{GDBN} Command Files.
25553 @xref{Command Files,, Command files}.
25555 You can control how @value{GDBN} evaluates these files with the following
25559 @kindex set script-extension
25560 @kindex show script-extension
25561 @item set script-extension off
25562 All scripts are always evaluated as @value{GDBN} Command Files.
25564 @item set script-extension soft
25565 The debugger determines the scripting language based on filename
25566 extension. If this scripting language is supported, @value{GDBN}
25567 evaluates the script using that language. Otherwise, it evaluates
25568 the file as a @value{GDBN} Command File.
25570 @item set script-extension strict
25571 The debugger determines the scripting language based on filename
25572 extension, and evaluates the script using that language. If the
25573 language is not supported, then the evaluation fails.
25575 @item show script-extension
25576 Display the current value of the @code{script-extension} option.
25581 @section Canned Sequences of Commands
25583 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
25584 Command Lists}), @value{GDBN} provides two ways to store sequences of
25585 commands for execution as a unit: user-defined commands and command
25589 * Define:: How to define your own commands
25590 * Hooks:: Hooks for user-defined commands
25591 * Command Files:: How to write scripts of commands to be stored in a file
25592 * Output:: Commands for controlled output
25593 * Auto-loading sequences:: Controlling auto-loaded command files
25597 @subsection User-defined Commands
25599 @cindex user-defined command
25600 @cindex arguments, to user-defined commands
25601 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
25602 which you assign a new name as a command. This is done with the
25603 @code{define} command. User commands may accept an unlimited number of arguments
25604 separated by whitespace. Arguments are accessed within the user command
25605 via @code{$arg0@dots{}$argN}. A trivial example:
25609 print $arg0 + $arg1 + $arg2
25614 To execute the command use:
25621 This defines the command @code{adder}, which prints the sum of
25622 its three arguments. Note the arguments are text substitutions, so they may
25623 reference variables, use complex expressions, or even perform inferior
25626 @cindex argument count in user-defined commands
25627 @cindex how many arguments (user-defined commands)
25628 In addition, @code{$argc} may be used to find out how many arguments have
25634 print $arg0 + $arg1
25637 print $arg0 + $arg1 + $arg2
25642 Combining with the @code{eval} command (@pxref{eval}) makes it easier
25643 to process a variable number of arguments:
25650 eval "set $sum = $sum + $arg%d", $i
25660 @item define @var{commandname}
25661 Define a command named @var{commandname}. If there is already a command
25662 by that name, you are asked to confirm that you want to redefine it.
25663 The argument @var{commandname} may be a bare command name consisting of letters,
25664 numbers, dashes, and underscores. It may also start with any predefined
25665 prefix command. For example, @samp{define target my-target} creates
25666 a user-defined @samp{target my-target} command.
25668 The definition of the command is made up of other @value{GDBN} command lines,
25669 which are given following the @code{define} command. The end of these
25670 commands is marked by a line containing @code{end}.
25673 @kindex end@r{ (user-defined commands)}
25674 @item document @var{commandname}
25675 Document the user-defined command @var{commandname}, so that it can be
25676 accessed by @code{help}. The command @var{commandname} must already be
25677 defined. This command reads lines of documentation just as @code{define}
25678 reads the lines of the command definition, ending with @code{end}.
25679 After the @code{document} command is finished, @code{help} on command
25680 @var{commandname} displays the documentation you have written.
25682 You may use the @code{document} command again to change the
25683 documentation of a command. Redefining the command with @code{define}
25684 does not change the documentation.
25686 @kindex dont-repeat
25687 @cindex don't repeat command
25689 Used inside a user-defined command, this tells @value{GDBN} that this
25690 command should not be repeated when the user hits @key{RET}
25691 (@pxref{Command Syntax, repeat last command}).
25693 @kindex help user-defined
25694 @item help user-defined
25695 List all user-defined commands and all python commands defined in class
25696 COMAND_USER. The first line of the documentation or docstring is
25701 @itemx show user @var{commandname}
25702 Display the @value{GDBN} commands used to define @var{commandname} (but
25703 not its documentation). If no @var{commandname} is given, display the
25704 definitions for all user-defined commands.
25705 This does not work for user-defined python commands.
25707 @cindex infinite recursion in user-defined commands
25708 @kindex show max-user-call-depth
25709 @kindex set max-user-call-depth
25710 @item show max-user-call-depth
25711 @itemx set max-user-call-depth
25712 The value of @code{max-user-call-depth} controls how many recursion
25713 levels are allowed in user-defined commands before @value{GDBN} suspects an
25714 infinite recursion and aborts the command.
25715 This does not apply to user-defined python commands.
25718 In addition to the above commands, user-defined commands frequently
25719 use control flow commands, described in @ref{Command Files}.
25721 When user-defined commands are executed, the
25722 commands of the definition are not printed. An error in any command
25723 stops execution of the user-defined command.
25725 If used interactively, commands that would ask for confirmation proceed
25726 without asking when used inside a user-defined command. Many @value{GDBN}
25727 commands that normally print messages to say what they are doing omit the
25728 messages when used in a user-defined command.
25731 @subsection User-defined Command Hooks
25732 @cindex command hooks
25733 @cindex hooks, for commands
25734 @cindex hooks, pre-command
25737 You may define @dfn{hooks}, which are a special kind of user-defined
25738 command. Whenever you run the command @samp{foo}, if the user-defined
25739 command @samp{hook-foo} exists, it is executed (with no arguments)
25740 before that command.
25742 @cindex hooks, post-command
25744 A hook may also be defined which is run after the command you executed.
25745 Whenever you run the command @samp{foo}, if the user-defined command
25746 @samp{hookpost-foo} exists, it is executed (with no arguments) after
25747 that command. Post-execution hooks may exist simultaneously with
25748 pre-execution hooks, for the same command.
25750 It is valid for a hook to call the command which it hooks. If this
25751 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
25753 @c It would be nice if hookpost could be passed a parameter indicating
25754 @c if the command it hooks executed properly or not. FIXME!
25756 @kindex stop@r{, a pseudo-command}
25757 In addition, a pseudo-command, @samp{stop} exists. Defining
25758 (@samp{hook-stop}) makes the associated commands execute every time
25759 execution stops in your program: before breakpoint commands are run,
25760 displays are printed, or the stack frame is printed.
25762 For example, to ignore @code{SIGALRM} signals while
25763 single-stepping, but treat them normally during normal execution,
25768 handle SIGALRM nopass
25772 handle SIGALRM pass
25775 define hook-continue
25776 handle SIGALRM pass
25780 As a further example, to hook at the beginning and end of the @code{echo}
25781 command, and to add extra text to the beginning and end of the message,
25789 define hookpost-echo
25793 (@value{GDBP}) echo Hello World
25794 <<<---Hello World--->>>
25799 You can define a hook for any single-word command in @value{GDBN}, but
25800 not for command aliases; you should define a hook for the basic command
25801 name, e.g.@: @code{backtrace} rather than @code{bt}.
25802 @c FIXME! So how does Joe User discover whether a command is an alias
25804 You can hook a multi-word command by adding @code{hook-} or
25805 @code{hookpost-} to the last word of the command, e.g.@:
25806 @samp{define target hook-remote} to add a hook to @samp{target remote}.
25808 If an error occurs during the execution of your hook, execution of
25809 @value{GDBN} commands stops and @value{GDBN} issues a prompt
25810 (before the command that you actually typed had a chance to run).
25812 If you try to define a hook which does not match any known command, you
25813 get a warning from the @code{define} command.
25815 @node Command Files
25816 @subsection Command Files
25818 @cindex command files
25819 @cindex scripting commands
25820 A command file for @value{GDBN} is a text file made of lines that are
25821 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
25822 also be included. An empty line in a command file does nothing; it
25823 does not mean to repeat the last command, as it would from the
25826 You can request the execution of a command file with the @code{source}
25827 command. Note that the @code{source} command is also used to evaluate
25828 scripts that are not Command Files. The exact behavior can be configured
25829 using the @code{script-extension} setting.
25830 @xref{Extending GDB,, Extending GDB}.
25834 @cindex execute commands from a file
25835 @item source [-s] [-v] @var{filename}
25836 Execute the command file @var{filename}.
25839 The lines in a command file are generally executed sequentially,
25840 unless the order of execution is changed by one of the
25841 @emph{flow-control commands} described below. The commands are not
25842 printed as they are executed. An error in any command terminates
25843 execution of the command file and control is returned to the console.
25845 @value{GDBN} first searches for @var{filename} in the current directory.
25846 If the file is not found there, and @var{filename} does not specify a
25847 directory, then @value{GDBN} also looks for the file on the source search path
25848 (specified with the @samp{directory} command);
25849 except that @file{$cdir} is not searched because the compilation directory
25850 is not relevant to scripts.
25852 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
25853 on the search path even if @var{filename} specifies a directory.
25854 The search is done by appending @var{filename} to each element of the
25855 search path. So, for example, if @var{filename} is @file{mylib/myscript}
25856 and the search path contains @file{/home/user} then @value{GDBN} will
25857 look for the script @file{/home/user/mylib/myscript}.
25858 The search is also done if @var{filename} is an absolute path.
25859 For example, if @var{filename} is @file{/tmp/myscript} and
25860 the search path contains @file{/home/user} then @value{GDBN} will
25861 look for the script @file{/home/user/tmp/myscript}.
25862 For DOS-like systems, if @var{filename} contains a drive specification,
25863 it is stripped before concatenation. For example, if @var{filename} is
25864 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
25865 will look for the script @file{c:/tmp/myscript}.
25867 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
25868 each command as it is executed. The option must be given before
25869 @var{filename}, and is interpreted as part of the filename anywhere else.
25871 Commands that would ask for confirmation if used interactively proceed
25872 without asking when used in a command file. Many @value{GDBN} commands that
25873 normally print messages to say what they are doing omit the messages
25874 when called from command files.
25876 @value{GDBN} also accepts command input from standard input. In this
25877 mode, normal output goes to standard output and error output goes to
25878 standard error. Errors in a command file supplied on standard input do
25879 not terminate execution of the command file---execution continues with
25883 gdb < cmds > log 2>&1
25886 (The syntax above will vary depending on the shell used.) This example
25887 will execute commands from the file @file{cmds}. All output and errors
25888 would be directed to @file{log}.
25890 Since commands stored on command files tend to be more general than
25891 commands typed interactively, they frequently need to deal with
25892 complicated situations, such as different or unexpected values of
25893 variables and symbols, changes in how the program being debugged is
25894 built, etc. @value{GDBN} provides a set of flow-control commands to
25895 deal with these complexities. Using these commands, you can write
25896 complex scripts that loop over data structures, execute commands
25897 conditionally, etc.
25904 This command allows to include in your script conditionally executed
25905 commands. The @code{if} command takes a single argument, which is an
25906 expression to evaluate. It is followed by a series of commands that
25907 are executed only if the expression is true (its value is nonzero).
25908 There can then optionally be an @code{else} line, followed by a series
25909 of commands that are only executed if the expression was false. The
25910 end of the list is marked by a line containing @code{end}.
25914 This command allows to write loops. Its syntax is similar to
25915 @code{if}: the command takes a single argument, which is an expression
25916 to evaluate, and must be followed by the commands to execute, one per
25917 line, terminated by an @code{end}. These commands are called the
25918 @dfn{body} of the loop. The commands in the body of @code{while} are
25919 executed repeatedly as long as the expression evaluates to true.
25923 This command exits the @code{while} loop in whose body it is included.
25924 Execution of the script continues after that @code{while}s @code{end}
25927 @kindex loop_continue
25928 @item loop_continue
25929 This command skips the execution of the rest of the body of commands
25930 in the @code{while} loop in whose body it is included. Execution
25931 branches to the beginning of the @code{while} loop, where it evaluates
25932 the controlling expression.
25934 @kindex end@r{ (if/else/while commands)}
25936 Terminate the block of commands that are the body of @code{if},
25937 @code{else}, or @code{while} flow-control commands.
25942 @subsection Commands for Controlled Output
25944 During the execution of a command file or a user-defined command, normal
25945 @value{GDBN} output is suppressed; the only output that appears is what is
25946 explicitly printed by the commands in the definition. This section
25947 describes three commands useful for generating exactly the output you
25952 @item echo @var{text}
25953 @c I do not consider backslash-space a standard C escape sequence
25954 @c because it is not in ANSI.
25955 Print @var{text}. Nonprinting characters can be included in
25956 @var{text} using C escape sequences, such as @samp{\n} to print a
25957 newline. @strong{No newline is printed unless you specify one.}
25958 In addition to the standard C escape sequences, a backslash followed
25959 by a space stands for a space. This is useful for displaying a
25960 string with spaces at the beginning or the end, since leading and
25961 trailing spaces are otherwise trimmed from all arguments.
25962 To print @samp{@w{ }and foo =@w{ }}, use the command
25963 @samp{echo \@w{ }and foo = \@w{ }}.
25965 A backslash at the end of @var{text} can be used, as in C, to continue
25966 the command onto subsequent lines. For example,
25969 echo This is some text\n\
25970 which is continued\n\
25971 onto several lines.\n
25974 produces the same output as
25977 echo This is some text\n
25978 echo which is continued\n
25979 echo onto several lines.\n
25983 @item output @var{expression}
25984 Print the value of @var{expression} and nothing but that value: no
25985 newlines, no @samp{$@var{nn} = }. The value is not entered in the
25986 value history either. @xref{Expressions, ,Expressions}, for more information
25989 @item output/@var{fmt} @var{expression}
25990 Print the value of @var{expression} in format @var{fmt}. You can use
25991 the same formats as for @code{print}. @xref{Output Formats,,Output
25992 Formats}, for more information.
25995 @item printf @var{template}, @var{expressions}@dots{}
25996 Print the values of one or more @var{expressions} under the control of
25997 the string @var{template}. To print several values, make
25998 @var{expressions} be a comma-separated list of individual expressions,
25999 which may be either numbers or pointers. Their values are printed as
26000 specified by @var{template}, exactly as a C program would do by
26001 executing the code below:
26004 printf (@var{template}, @var{expressions}@dots{});
26007 As in @code{C} @code{printf}, ordinary characters in @var{template}
26008 are printed verbatim, while @dfn{conversion specification} introduced
26009 by the @samp{%} character cause subsequent @var{expressions} to be
26010 evaluated, their values converted and formatted according to type and
26011 style information encoded in the conversion specifications, and then
26014 For example, you can print two values in hex like this:
26017 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
26020 @code{printf} supports all the standard @code{C} conversion
26021 specifications, including the flags and modifiers between the @samp{%}
26022 character and the conversion letter, with the following exceptions:
26026 The argument-ordering modifiers, such as @samp{2$}, are not supported.
26029 The modifier @samp{*} is not supported for specifying precision or
26033 The @samp{'} flag (for separation of digits into groups according to
26034 @code{LC_NUMERIC'}) is not supported.
26037 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
26041 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
26044 The conversion letters @samp{a} and @samp{A} are not supported.
26048 Note that the @samp{ll} type modifier is supported only if the
26049 underlying @code{C} implementation used to build @value{GDBN} supports
26050 the @code{long long int} type, and the @samp{L} type modifier is
26051 supported only if @code{long double} type is available.
26053 As in @code{C}, @code{printf} supports simple backslash-escape
26054 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
26055 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
26056 single character. Octal and hexadecimal escape sequences are not
26059 Additionally, @code{printf} supports conversion specifications for DFP
26060 (@dfn{Decimal Floating Point}) types using the following length modifiers
26061 together with a floating point specifier.
26066 @samp{H} for printing @code{Decimal32} types.
26069 @samp{D} for printing @code{Decimal64} types.
26072 @samp{DD} for printing @code{Decimal128} types.
26075 If the underlying @code{C} implementation used to build @value{GDBN} has
26076 support for the three length modifiers for DFP types, other modifiers
26077 such as width and precision will also be available for @value{GDBN} to use.
26079 In case there is no such @code{C} support, no additional modifiers will be
26080 available and the value will be printed in the standard way.
26082 Here's an example of printing DFP types using the above conversion letters:
26084 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
26089 @item eval @var{template}, @var{expressions}@dots{}
26090 Convert the values of one or more @var{expressions} under the control of
26091 the string @var{template} to a command line, and call it.
26095 @node Auto-loading sequences
26096 @subsection Controlling auto-loading native @value{GDBN} scripts
26097 @cindex native script auto-loading
26099 When a new object file is read (for example, due to the @code{file}
26100 command, or because the inferior has loaded a shared library),
26101 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
26102 @xref{Auto-loading extensions}.
26104 Auto-loading can be enabled or disabled,
26105 and the list of auto-loaded scripts can be printed.
26108 @anchor{set auto-load gdb-scripts}
26109 @kindex set auto-load gdb-scripts
26110 @item set auto-load gdb-scripts [on|off]
26111 Enable or disable the auto-loading of canned sequences of commands scripts.
26113 @anchor{show auto-load gdb-scripts}
26114 @kindex show auto-load gdb-scripts
26115 @item show auto-load gdb-scripts
26116 Show whether auto-loading of canned sequences of commands scripts is enabled or
26119 @anchor{info auto-load gdb-scripts}
26120 @kindex info auto-load gdb-scripts
26121 @cindex print list of auto-loaded canned sequences of commands scripts
26122 @item info auto-load gdb-scripts [@var{regexp}]
26123 Print the list of all canned sequences of commands scripts that @value{GDBN}
26127 If @var{regexp} is supplied only canned sequences of commands scripts with
26128 matching names are printed.
26130 @c Python docs live in a separate file.
26131 @include python.texi
26133 @c Guile docs live in a separate file.
26134 @include guile.texi
26136 @node Auto-loading extensions
26137 @section Auto-loading extensions
26138 @cindex auto-loading extensions
26140 @value{GDBN} provides two mechanisms for automatically loading extensions
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 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
26144 section of modern file formats like ELF.
26147 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
26148 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
26149 * Which flavor to choose?::
26152 The auto-loading feature is useful for supplying application-specific
26153 debugging commands and features.
26155 Auto-loading can be enabled or disabled,
26156 and the list of auto-loaded scripts can be printed.
26157 See the @samp{auto-loading} section of each extension language
26158 for more information.
26159 For @value{GDBN} command files see @ref{Auto-loading sequences}.
26160 For Python files see @ref{Python Auto-loading}.
26162 Note that loading of this script file also requires accordingly configured
26163 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26165 @node objfile-gdbdotext file
26166 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
26167 @cindex @file{@var{objfile}-gdb.gdb}
26168 @cindex @file{@var{objfile}-gdb.py}
26169 @cindex @file{@var{objfile}-gdb.scm}
26171 When a new object file is read, @value{GDBN} looks for a file named
26172 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
26173 where @var{objfile} is the object file's name and
26174 where @var{ext} is the file extension for the extension language:
26177 @item @file{@var{objfile}-gdb.gdb}
26178 GDB's own command language
26179 @item @file{@var{objfile}-gdb.py}
26181 @item @file{@var{objfile}-gdb.scm}
26185 @var{script-name} is formed by ensuring that the file name of @var{objfile}
26186 is absolute, following all symlinks, and resolving @code{.} and @code{..}
26187 components, and appending the @file{-gdb.@var{ext}} suffix.
26188 If this file exists and is readable, @value{GDBN} will evaluate it as a
26189 script in the specified extension language.
26191 If this file does not exist, then @value{GDBN} will look for
26192 @var{script-name} file in all of the directories as specified below.
26194 Note that loading of these files requires an accordingly configured
26195 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26197 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26198 scripts normally according to its @file{.exe} filename. But if no scripts are
26199 found @value{GDBN} also tries script filenames matching the object file without
26200 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26201 is attempted on any platform. This makes the script filenames compatible
26202 between Unix and MS-Windows hosts.
26205 @anchor{set auto-load scripts-directory}
26206 @kindex set auto-load scripts-directory
26207 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26208 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26209 may be delimited by the host platform path separator in use
26210 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26212 Each entry here needs to be covered also by the security setting
26213 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26215 @anchor{with-auto-load-dir}
26216 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26217 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26218 configuration option @option{--with-auto-load-dir}.
26220 Any reference to @file{$debugdir} will get replaced by
26221 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26222 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26223 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26224 @file{$datadir} must be placed as a directory component --- either alone or
26225 delimited by @file{/} or @file{\} directory separators, depending on the host
26228 The list of directories uses path separator (@samp{:} on GNU and Unix
26229 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26230 to the @env{PATH} environment variable.
26232 @anchor{show auto-load scripts-directory}
26233 @kindex show auto-load scripts-directory
26234 @item show auto-load scripts-directory
26235 Show @value{GDBN} auto-loaded scripts location.
26237 @anchor{add-auto-load-scripts-directory}
26238 @kindex add-auto-load-scripts-directory
26239 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
26240 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
26241 Multiple entries may be delimited by the host platform path separator in use.
26244 @value{GDBN} does not track which files it has already auto-loaded this way.
26245 @value{GDBN} will load the associated script every time the corresponding
26246 @var{objfile} is opened.
26247 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
26248 is evaluated more than once.
26250 @node dotdebug_gdb_scripts section
26251 @subsection The @code{.debug_gdb_scripts} section
26252 @cindex @code{.debug_gdb_scripts} section
26254 For systems using file formats like ELF and COFF,
26255 when @value{GDBN} loads a new object file
26256 it will look for a special section named @code{.debug_gdb_scripts}.
26257 If this section exists, its contents is a list of null-terminated entries
26258 specifying scripts to load. Each entry begins with a non-null prefix byte that
26259 specifies the kind of entry, typically the extension language and whether the
26260 script is in a file or inlined in @code{.debug_gdb_scripts}.
26262 The following entries are supported:
26265 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
26266 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
26267 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
26268 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
26271 @subsubsection Script File Entries
26273 If the entry specifies a file, @value{GDBN} will look for the file first
26274 in the current directory and then along the source search path
26275 (@pxref{Source Path, ,Specifying Source Directories}),
26276 except that @file{$cdir} is not searched, since the compilation
26277 directory is not relevant to scripts.
26279 File entries can be placed in section @code{.debug_gdb_scripts} with,
26280 for example, this GCC macro for Python scripts.
26283 /* Note: The "MS" section flags are to remove duplicates. */
26284 #define DEFINE_GDB_PY_SCRIPT(script_name) \
26286 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26287 .byte 1 /* Python */\n\
26288 .asciz \"" script_name "\"\n\
26294 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
26295 Then one can reference the macro in a header or source file like this:
26298 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
26301 The script name may include directories if desired.
26303 Note that loading of this script file also requires accordingly configured
26304 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26306 If the macro invocation is put in a header, any application or library
26307 using this header will get a reference to the specified script,
26308 and with the use of @code{"MS"} attributes on the section, the linker
26309 will remove duplicates.
26311 @subsubsection Script Text Entries
26313 Script text entries allow to put the executable script in the entry
26314 itself instead of loading it from a file.
26315 The first line of the entry, everything after the prefix byte and up to
26316 the first newline (@code{0xa}) character, is the script name, and must not
26317 contain any kind of space character, e.g., spaces or tabs.
26318 The rest of the entry, up to the trailing null byte, is the script to
26319 execute in the specified language. The name needs to be unique among
26320 all script names, as @value{GDBN} executes each script only once based
26323 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
26327 #include "symcat.h"
26328 #include "gdb/section-scripts.h"
26330 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
26331 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
26332 ".ascii \"gdb.inlined-script\\n\"\n"
26333 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
26334 ".ascii \" def __init__ (self):\\n\"\n"
26335 ".ascii \" super (test_cmd, self).__init__ ("
26336 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
26337 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
26338 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
26339 ".ascii \"test_cmd ()\\n\"\n"
26345 Loading of inlined scripts requires a properly configured
26346 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26347 The path to specify in @code{auto-load safe-path} is the path of the file
26348 containing the @code{.debug_gdb_scripts} section.
26350 @node Which flavor to choose?
26351 @subsection Which flavor to choose?
26353 Given the multiple ways of auto-loading extensions, it might not always
26354 be clear which one to choose. This section provides some guidance.
26357 Benefits of the @file{-gdb.@var{ext}} way:
26361 Can be used with file formats that don't support multiple sections.
26364 Ease of finding scripts for public libraries.
26366 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26367 in the source search path.
26368 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26369 isn't a source directory in which to find the script.
26372 Doesn't require source code additions.
26376 Benefits of the @code{.debug_gdb_scripts} way:
26380 Works with static linking.
26382 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
26383 trigger their loading. When an application is statically linked the only
26384 objfile available is the executable, and it is cumbersome to attach all the
26385 scripts from all the input libraries to the executable's
26386 @file{-gdb.@var{ext}} script.
26389 Works with classes that are entirely inlined.
26391 Some classes can be entirely inlined, and thus there may not be an associated
26392 shared library to attach a @file{-gdb.@var{ext}} script to.
26395 Scripts needn't be copied out of the source tree.
26397 In some circumstances, apps can be built out of large collections of internal
26398 libraries, and the build infrastructure necessary to install the
26399 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
26400 cumbersome. It may be easier to specify the scripts in the
26401 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26402 top of the source tree to the source search path.
26405 @node Multiple Extension Languages
26406 @section Multiple Extension Languages
26408 The Guile and Python extension languages do not share any state,
26409 and generally do not interfere with each other.
26410 There are some things to be aware of, however.
26412 @subsection Python comes first
26414 Python was @value{GDBN}'s first extension language, and to avoid breaking
26415 existing behaviour Python comes first. This is generally solved by the
26416 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
26417 extension languages, and when it makes a call to an extension language,
26418 (say to pretty-print a value), it tries each in turn until an extension
26419 language indicates it has performed the request (e.g., has returned the
26420 pretty-printed form of a value).
26421 This extends to errors while performing such requests: If an error happens
26422 while, for example, trying to pretty-print an object then the error is
26423 reported and any following extension languages are not tried.
26426 @section Creating new spellings of existing commands
26427 @cindex aliases for commands
26429 It is often useful to define alternate spellings of existing commands.
26430 For example, if a new @value{GDBN} command defined in Python has
26431 a long name to type, it is handy to have an abbreviated version of it
26432 that involves less typing.
26434 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26435 of the @samp{step} command even though it is otherwise an ambiguous
26436 abbreviation of other commands like @samp{set} and @samp{show}.
26438 Aliases are also used to provide shortened or more common versions
26439 of multi-word commands. For example, @value{GDBN} provides the
26440 @samp{tty} alias of the @samp{set inferior-tty} command.
26442 You can define a new alias with the @samp{alias} command.
26447 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26451 @var{ALIAS} specifies the name of the new alias.
26452 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26455 @var{COMMAND} specifies the name of an existing command
26456 that is being aliased.
26458 The @samp{-a} option specifies that the new alias is an abbreviation
26459 of the command. Abbreviations are not shown in command
26460 lists displayed by the @samp{help} command.
26462 The @samp{--} option specifies the end of options,
26463 and is useful when @var{ALIAS} begins with a dash.
26465 Here is a simple example showing how to make an abbreviation
26466 of a command so that there is less to type.
26467 Suppose you were tired of typing @samp{disas}, the current
26468 shortest unambiguous abbreviation of the @samp{disassemble} command
26469 and you wanted an even shorter version named @samp{di}.
26470 The following will accomplish this.
26473 (gdb) alias -a di = disas
26476 Note that aliases are different from user-defined commands.
26477 With a user-defined command, you also need to write documentation
26478 for it with the @samp{document} command.
26479 An alias automatically picks up the documentation of the existing command.
26481 Here is an example where we make @samp{elms} an abbreviation of
26482 @samp{elements} in the @samp{set print elements} command.
26483 This is to show that you can make an abbreviation of any part
26487 (gdb) alias -a set print elms = set print elements
26488 (gdb) alias -a show print elms = show print elements
26489 (gdb) set p elms 20
26491 Limit on string chars or array elements to print is 200.
26494 Note that if you are defining an alias of a @samp{set} command,
26495 and you want to have an alias for the corresponding @samp{show}
26496 command, then you need to define the latter separately.
26498 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26499 @var{ALIAS}, just as they are normally.
26502 (gdb) alias -a set pr elms = set p ele
26505 Finally, here is an example showing the creation of a one word
26506 alias for a more complex command.
26507 This creates alias @samp{spe} of the command @samp{set print elements}.
26510 (gdb) alias spe = set print elements
26515 @chapter Command Interpreters
26516 @cindex command interpreters
26518 @value{GDBN} supports multiple command interpreters, and some command
26519 infrastructure to allow users or user interface writers to switch
26520 between interpreters or run commands in other interpreters.
26522 @value{GDBN} currently supports two command interpreters, the console
26523 interpreter (sometimes called the command-line interpreter or @sc{cli})
26524 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26525 describes both of these interfaces in great detail.
26527 By default, @value{GDBN} will start with the console interpreter.
26528 However, the user may choose to start @value{GDBN} with another
26529 interpreter by specifying the @option{-i} or @option{--interpreter}
26530 startup options. Defined interpreters include:
26534 @cindex console interpreter
26535 The traditional console or command-line interpreter. This is the most often
26536 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26537 @value{GDBN} will use this interpreter.
26540 @cindex mi interpreter
26541 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
26542 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26543 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26547 @cindex mi3 interpreter
26548 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
26551 @cindex mi2 interpreter
26552 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
26555 @cindex mi1 interpreter
26556 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
26560 @cindex invoke another interpreter
26562 @kindex interpreter-exec
26563 You may execute commands in any interpreter from the current
26564 interpreter using the appropriate command. If you are running the
26565 console interpreter, simply use the @code{interpreter-exec} command:
26568 interpreter-exec mi "-data-list-register-names"
26571 @sc{gdb/mi} has a similar command, although it is only available in versions of
26572 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26574 Note that @code{interpreter-exec} only changes the interpreter for the
26575 duration of the specified command. It does not change the interpreter
26578 @cindex start a new independent interpreter
26580 Although you may only choose a single interpreter at startup, it is
26581 possible to run an independent interpreter on a specified input/output
26582 device (usually a tty).
26584 For example, consider a debugger GUI or IDE that wants to provide a
26585 @value{GDBN} console view. It may do so by embedding a terminal
26586 emulator widget in its GUI, starting @value{GDBN} in the traditional
26587 command-line mode with stdin/stdout/stderr redirected to that
26588 terminal, and then creating an MI interpreter running on a specified
26589 input/output device. The console interpreter created by @value{GDBN}
26590 at startup handles commands the user types in the terminal widget,
26591 while the GUI controls and synchronizes state with @value{GDBN} using
26592 the separate MI interpreter.
26594 To start a new secondary @dfn{user interface} running MI, use the
26595 @code{new-ui} command:
26598 @cindex new user interface
26600 new-ui @var{interpreter} @var{tty}
26603 The @var{interpreter} parameter specifies the interpreter to run.
26604 This accepts the same values as the @code{interpreter-exec} command.
26605 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
26606 @var{tty} parameter specifies the name of the bidirectional file the
26607 interpreter uses for input/output, usually the name of a
26608 pseudoterminal slave on Unix systems. For example:
26611 (@value{GDBP}) new-ui mi /dev/pts/9
26615 runs an MI interpreter on @file{/dev/pts/9}.
26618 @chapter @value{GDBN} Text User Interface
26620 @cindex Text User Interface
26623 * TUI Overview:: TUI overview
26624 * TUI Keys:: TUI key bindings
26625 * TUI Single Key Mode:: TUI single key mode
26626 * TUI Commands:: TUI-specific commands
26627 * TUI Configuration:: TUI configuration variables
26630 The @value{GDBN} Text User Interface (TUI) is a terminal
26631 interface which uses the @code{curses} library to show the source
26632 file, the assembly output, the program registers and @value{GDBN}
26633 commands in separate text windows. The TUI mode is supported only
26634 on platforms where a suitable version of the @code{curses} library
26637 The TUI mode is enabled by default when you invoke @value{GDBN} as
26638 @samp{@value{GDBP} -tui}.
26639 You can also switch in and out of TUI mode while @value{GDBN} runs by
26640 using various TUI commands and key bindings, such as @command{tui
26641 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
26642 @ref{TUI Keys, ,TUI Key Bindings}.
26645 @section TUI Overview
26647 In TUI mode, @value{GDBN} can display several text windows:
26651 This window is the @value{GDBN} command window with the @value{GDBN}
26652 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26653 managed using readline.
26656 The source window shows the source file of the program. The current
26657 line and active breakpoints are displayed in this window.
26660 The assembly window shows the disassembly output of the program.
26663 This window shows the processor registers. Registers are highlighted
26664 when their values change.
26667 The source and assembly windows show the current program position
26668 by highlighting the current line and marking it with a @samp{>} marker.
26669 Breakpoints are indicated with two markers. The first marker
26670 indicates the breakpoint type:
26674 Breakpoint which was hit at least once.
26677 Breakpoint which was never hit.
26680 Hardware breakpoint which was hit at least once.
26683 Hardware breakpoint which was never hit.
26686 The second marker indicates whether the breakpoint is enabled or not:
26690 Breakpoint is enabled.
26693 Breakpoint is disabled.
26696 The source, assembly and register windows are updated when the current
26697 thread changes, when the frame changes, or when the program counter
26700 These windows are not all visible at the same time. The command
26701 window is always visible. The others can be arranged in several
26712 source and assembly,
26715 source and registers, or
26718 assembly and registers.
26721 A status line above the command window shows the following information:
26725 Indicates the current @value{GDBN} target.
26726 (@pxref{Targets, ,Specifying a Debugging Target}).
26729 Gives the current process or thread number.
26730 When no process is being debugged, this field is set to @code{No process}.
26733 Gives the current function name for the selected frame.
26734 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26735 When there is no symbol corresponding to the current program counter,
26736 the string @code{??} is displayed.
26739 Indicates the current line number for the selected frame.
26740 When the current line number is not known, the string @code{??} is displayed.
26743 Indicates the current program counter address.
26747 @section TUI Key Bindings
26748 @cindex TUI key bindings
26750 The TUI installs several key bindings in the readline keymaps
26751 @ifset SYSTEM_READLINE
26752 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26754 @ifclear SYSTEM_READLINE
26755 (@pxref{Command Line Editing}).
26757 The following key bindings are installed for both TUI mode and the
26758 @value{GDBN} standard mode.
26767 Enter or leave the TUI mode. When leaving the TUI mode,
26768 the curses window management stops and @value{GDBN} operates using
26769 its standard mode, writing on the terminal directly. When reentering
26770 the TUI mode, control is given back to the curses windows.
26771 The screen is then refreshed.
26775 Use a TUI layout with only one window. The layout will
26776 either be @samp{source} or @samp{assembly}. When the TUI mode
26777 is not active, it will switch to the TUI mode.
26779 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26783 Use a TUI layout with at least two windows. When the current
26784 layout already has two windows, the next layout with two windows is used.
26785 When a new layout is chosen, one window will always be common to the
26786 previous layout and the new one.
26788 Think of it as the Emacs @kbd{C-x 2} binding.
26792 Change the active window. The TUI associates several key bindings
26793 (like scrolling and arrow keys) with the active window. This command
26794 gives the focus to the next TUI window.
26796 Think of it as the Emacs @kbd{C-x o} binding.
26800 Switch in and out of the TUI SingleKey mode that binds single
26801 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26804 The following key bindings only work in the TUI mode:
26809 Scroll the active window one page up.
26813 Scroll the active window one page down.
26817 Scroll the active window one line up.
26821 Scroll the active window one line down.
26825 Scroll the active window one column left.
26829 Scroll the active window one column right.
26833 Refresh the screen.
26836 Because the arrow keys scroll the active window in the TUI mode, they
26837 are not available for their normal use by readline unless the command
26838 window has the focus. When another window is active, you must use
26839 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26840 and @kbd{C-f} to control the command window.
26842 @node TUI Single Key Mode
26843 @section TUI Single Key Mode
26844 @cindex TUI single key mode
26846 The TUI also provides a @dfn{SingleKey} mode, which binds several
26847 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26848 switch into this mode, where the following key bindings are used:
26851 @kindex c @r{(SingleKey TUI key)}
26855 @kindex d @r{(SingleKey TUI key)}
26859 @kindex f @r{(SingleKey TUI key)}
26863 @kindex n @r{(SingleKey TUI key)}
26867 @kindex o @r{(SingleKey TUI key)}
26869 nexti. The shortcut letter @samp{o} stands for ``step Over''.
26871 @kindex q @r{(SingleKey TUI key)}
26873 exit the SingleKey mode.
26875 @kindex r @r{(SingleKey TUI key)}
26879 @kindex s @r{(SingleKey TUI key)}
26883 @kindex i @r{(SingleKey TUI key)}
26885 stepi. The shortcut letter @samp{i} stands for ``step Into''.
26887 @kindex u @r{(SingleKey TUI key)}
26891 @kindex v @r{(SingleKey TUI key)}
26895 @kindex w @r{(SingleKey TUI key)}
26900 Other keys temporarily switch to the @value{GDBN} command prompt.
26901 The key that was pressed is inserted in the editing buffer so that
26902 it is possible to type most @value{GDBN} commands without interaction
26903 with the TUI SingleKey mode. Once the command is entered the TUI
26904 SingleKey mode is restored. The only way to permanently leave
26905 this mode is by typing @kbd{q} or @kbd{C-x s}.
26909 @section TUI-specific Commands
26910 @cindex TUI commands
26912 The TUI has specific commands to control the text windows.
26913 These commands are always available, even when @value{GDBN} is not in
26914 the TUI mode. When @value{GDBN} is in the standard mode, most
26915 of these commands will automatically switch to the TUI mode.
26917 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26918 terminal, or @value{GDBN} has been started with the machine interface
26919 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26920 these commands will fail with an error, because it would not be
26921 possible or desirable to enable curses window management.
26926 Activate TUI mode. The last active TUI window layout will be used if
26927 TUI mode has prevsiouly been used in the current debugging session,
26928 otherwise a default layout is used.
26931 @kindex tui disable
26932 Disable TUI mode, returning to the console interpreter.
26936 List and give the size of all displayed windows.
26938 @item layout @var{name}
26940 Changes which TUI windows are displayed. In each layout the command
26941 window is always displayed, the @var{name} parameter controls which
26942 additional windows are displayed, and can be any of the following:
26946 Display the next layout.
26949 Display the previous layout.
26952 Display the source and command windows.
26955 Display the assembly and command windows.
26958 Display the source, assembly, and command windows.
26961 When in @code{src} layout display the register, source, and command
26962 windows. When in @code{asm} or @code{split} layout display the
26963 register, assembler, and command windows.
26966 @item focus @var{name}
26968 Changes which TUI window is currently active for scrolling. The
26969 @var{name} parameter can be any of the following:
26973 Make the next window active for scrolling.
26976 Make the previous window active for scrolling.
26979 Make the source window active for scrolling.
26982 Make the assembly window active for scrolling.
26985 Make the register window active for scrolling.
26988 Make the command window active for scrolling.
26993 Refresh the screen. This is similar to typing @kbd{C-L}.
26995 @item tui reg @var{group}
26997 Changes the register group displayed in the tui register window to
26998 @var{group}. If the register window is not currently displayed this
26999 command will cause the register window to be displayed. The list of
27000 register groups, as well as their order is target specific. The
27001 following groups are available on most targets:
27004 Repeatedly selecting this group will cause the display to cycle
27005 through all of the available register groups.
27008 Repeatedly selecting this group will cause the display to cycle
27009 through all of the available register groups in the reverse order to
27013 Display the general registers.
27015 Display the floating point registers.
27017 Display the system registers.
27019 Display the vector registers.
27021 Display all registers.
27026 Update the source window and the current execution point.
27028 @item winheight @var{name} +@var{count}
27029 @itemx winheight @var{name} -@var{count}
27031 Change the height of the window @var{name} by @var{count}
27032 lines. Positive counts increase the height, while negative counts
27033 decrease it. The @var{name} parameter can be one of @code{src} (the
27034 source window), @code{cmd} (the command window), @code{asm} (the
27035 disassembly window), or @code{regs} (the register display window).
27038 @node TUI Configuration
27039 @section TUI Configuration Variables
27040 @cindex TUI configuration variables
27042 Several configuration variables control the appearance of TUI windows.
27045 @item set tui border-kind @var{kind}
27046 @kindex set tui border-kind
27047 Select the border appearance for the source, assembly and register windows.
27048 The possible values are the following:
27051 Use a space character to draw the border.
27054 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
27057 Use the Alternate Character Set to draw the border. The border is
27058 drawn using character line graphics if the terminal supports them.
27061 @item set tui border-mode @var{mode}
27062 @kindex set tui border-mode
27063 @itemx set tui active-border-mode @var{mode}
27064 @kindex set tui active-border-mode
27065 Select the display attributes for the borders of the inactive windows
27066 or the active window. The @var{mode} can be one of the following:
27069 Use normal attributes to display the border.
27075 Use reverse video mode.
27078 Use half bright mode.
27080 @item half-standout
27081 Use half bright and standout mode.
27084 Use extra bright or bold mode.
27086 @item bold-standout
27087 Use extra bright or bold and standout mode.
27090 @item set tui tab-width @var{nchars}
27091 @kindex set tui tab-width
27093 Set the width of tab stops to be @var{nchars} characters. This
27094 setting affects the display of TAB characters in the source and
27099 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27102 @cindex @sc{gnu} Emacs
27103 A special interface allows you to use @sc{gnu} Emacs to view (and
27104 edit) the source files for the program you are debugging with
27107 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27108 executable file you want to debug as an argument. This command starts
27109 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27110 created Emacs buffer.
27111 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27113 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27118 All ``terminal'' input and output goes through an Emacs buffer, called
27121 This applies both to @value{GDBN} commands and their output, and to the input
27122 and output done by the program you are debugging.
27124 This is useful because it means that you can copy the text of previous
27125 commands and input them again; you can even use parts of the output
27128 All the facilities of Emacs' Shell mode are available for interacting
27129 with your program. In particular, you can send signals the usual
27130 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27134 @value{GDBN} displays source code through Emacs.
27136 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27137 source file for that frame and puts an arrow (@samp{=>}) at the
27138 left margin of the current line. Emacs uses a separate buffer for
27139 source display, and splits the screen to show both your @value{GDBN} session
27142 Explicit @value{GDBN} @code{list} or search commands still produce output as
27143 usual, but you probably have no reason to use them from Emacs.
27146 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27147 a graphical mode, enabled by default, which provides further buffers
27148 that can control the execution and describe the state of your program.
27149 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27151 If you specify an absolute file name when prompted for the @kbd{M-x
27152 gdb} argument, then Emacs sets your current working directory to where
27153 your program resides. If you only specify the file name, then Emacs
27154 sets your current working directory to the directory associated
27155 with the previous buffer. In this case, @value{GDBN} may find your
27156 program by searching your environment's @code{PATH} variable, but on
27157 some operating systems it might not find the source. So, although the
27158 @value{GDBN} input and output session proceeds normally, the auxiliary
27159 buffer does not display the current source and line of execution.
27161 The initial working directory of @value{GDBN} is printed on the top
27162 line of the GUD buffer and this serves as a default for the commands
27163 that specify files for @value{GDBN} to operate on. @xref{Files,
27164 ,Commands to Specify Files}.
27166 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27167 need to call @value{GDBN} by a different name (for example, if you
27168 keep several configurations around, with different names) you can
27169 customize the Emacs variable @code{gud-gdb-command-name} to run the
27172 In the GUD buffer, you can use these special Emacs commands in
27173 addition to the standard Shell mode commands:
27177 Describe the features of Emacs' GUD Mode.
27180 Execute to another source line, like the @value{GDBN} @code{step} command; also
27181 update the display window to show the current file and location.
27184 Execute to next source line in this function, skipping all function
27185 calls, like the @value{GDBN} @code{next} command. Then update the display window
27186 to show the current file and location.
27189 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27190 display window accordingly.
27193 Execute until exit from the selected stack frame, like the @value{GDBN}
27194 @code{finish} command.
27197 Continue execution of your program, like the @value{GDBN} @code{continue}
27201 Go up the number of frames indicated by the numeric argument
27202 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27203 like the @value{GDBN} @code{up} command.
27206 Go down the number of frames indicated by the numeric argument, like the
27207 @value{GDBN} @code{down} command.
27210 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27211 tells @value{GDBN} to set a breakpoint on the source line point is on.
27213 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27214 separate frame which shows a backtrace when the GUD buffer is current.
27215 Move point to any frame in the stack and type @key{RET} to make it
27216 become the current frame and display the associated source in the
27217 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27218 selected frame become the current one. In graphical mode, the
27219 speedbar displays watch expressions.
27221 If you accidentally delete the source-display buffer, an easy way to get
27222 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27223 request a frame display; when you run under Emacs, this recreates
27224 the source buffer if necessary to show you the context of the current
27227 The source files displayed in Emacs are in ordinary Emacs buffers
27228 which are visiting the source files in the usual way. You can edit
27229 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27230 communicates with Emacs in terms of line numbers. If you add or
27231 delete lines from the text, the line numbers that @value{GDBN} knows cease
27232 to correspond properly with the code.
27234 A more detailed description of Emacs' interaction with @value{GDBN} is
27235 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27239 @chapter The @sc{gdb/mi} Interface
27241 @unnumberedsec Function and Purpose
27243 @cindex @sc{gdb/mi}, its purpose
27244 @sc{gdb/mi} is a line based machine oriented text interface to
27245 @value{GDBN} and is activated by specifying using the
27246 @option{--interpreter} command line option (@pxref{Mode Options}). It
27247 is specifically intended to support the development of systems which
27248 use the debugger as just one small component of a larger system.
27250 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27251 in the form of a reference manual.
27253 Note that @sc{gdb/mi} is still under construction, so some of the
27254 features described below are incomplete and subject to change
27255 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27257 @unnumberedsec Notation and Terminology
27259 @cindex notational conventions, for @sc{gdb/mi}
27260 This chapter uses the following notation:
27264 @code{|} separates two alternatives.
27267 @code{[ @var{something} ]} indicates that @var{something} is optional:
27268 it may or may not be given.
27271 @code{( @var{group} )*} means that @var{group} inside the parentheses
27272 may repeat zero or more times.
27275 @code{( @var{group} )+} means that @var{group} inside the parentheses
27276 may repeat one or more times.
27279 @code{"@var{string}"} means a literal @var{string}.
27283 @heading Dependencies
27287 * GDB/MI General Design::
27288 * GDB/MI Command Syntax::
27289 * GDB/MI Compatibility with CLI::
27290 * GDB/MI Development and Front Ends::
27291 * GDB/MI Output Records::
27292 * GDB/MI Simple Examples::
27293 * GDB/MI Command Description Format::
27294 * GDB/MI Breakpoint Commands::
27295 * GDB/MI Catchpoint Commands::
27296 * GDB/MI Program Context::
27297 * GDB/MI Thread Commands::
27298 * GDB/MI Ada Tasking Commands::
27299 * GDB/MI Program Execution::
27300 * GDB/MI Stack Manipulation::
27301 * GDB/MI Variable Objects::
27302 * GDB/MI Data Manipulation::
27303 * GDB/MI Tracepoint Commands::
27304 * GDB/MI Symbol Query::
27305 * GDB/MI File Commands::
27307 * GDB/MI Kod Commands::
27308 * GDB/MI Memory Overlay Commands::
27309 * GDB/MI Signal Handling Commands::
27311 * GDB/MI Target Manipulation::
27312 * GDB/MI File Transfer Commands::
27313 * GDB/MI Ada Exceptions Commands::
27314 * GDB/MI Support Commands::
27315 * GDB/MI Miscellaneous Commands::
27318 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27319 @node GDB/MI General Design
27320 @section @sc{gdb/mi} General Design
27321 @cindex GDB/MI General Design
27323 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27324 parts---commands sent to @value{GDBN}, responses to those commands
27325 and notifications. Each command results in exactly one response,
27326 indicating either successful completion of the command, or an error.
27327 For the commands that do not resume the target, the response contains the
27328 requested information. For the commands that resume the target, the
27329 response only indicates whether the target was successfully resumed.
27330 Notifications is the mechanism for reporting changes in the state of the
27331 target, or in @value{GDBN} state, that cannot conveniently be associated with
27332 a command and reported as part of that command response.
27334 The important examples of notifications are:
27338 Exec notifications. These are used to report changes in
27339 target state---when a target is resumed, or stopped. It would not
27340 be feasible to include this information in response of resuming
27341 commands, because one resume commands can result in multiple events in
27342 different threads. Also, quite some time may pass before any event
27343 happens in the target, while a frontend needs to know whether the resuming
27344 command itself was successfully executed.
27347 Console output, and status notifications. Console output
27348 notifications are used to report output of CLI commands, as well as
27349 diagnostics for other commands. Status notifications are used to
27350 report the progress of a long-running operation. Naturally, including
27351 this information in command response would mean no output is produced
27352 until the command is finished, which is undesirable.
27355 General notifications. Commands may have various side effects on
27356 the @value{GDBN} or target state beyond their official purpose. For example,
27357 a command may change the selected thread. Although such changes can
27358 be included in command response, using notification allows for more
27359 orthogonal frontend design.
27363 There's no guarantee that whenever an MI command reports an error,
27364 @value{GDBN} or the target are in any specific state, and especially,
27365 the state is not reverted to the state before the MI command was
27366 processed. Therefore, whenever an MI command results in an error,
27367 we recommend that the frontend refreshes all the information shown in
27368 the user interface.
27372 * Context management::
27373 * Asynchronous and non-stop modes::
27377 @node Context management
27378 @subsection Context management
27380 @subsubsection Threads and Frames
27382 In most cases when @value{GDBN} accesses the target, this access is
27383 done in context of a specific thread and frame (@pxref{Frames}).
27384 Often, even when accessing global data, the target requires that a thread
27385 be specified. The CLI interface maintains the selected thread and frame,
27386 and supplies them to target on each command. This is convenient,
27387 because a command line user would not want to specify that information
27388 explicitly on each command, and because user interacts with
27389 @value{GDBN} via a single terminal, so no confusion is possible as
27390 to what thread and frame are the current ones.
27392 In the case of MI, the concept of selected thread and frame is less
27393 useful. First, a frontend can easily remember this information
27394 itself. Second, a graphical frontend can have more than one window,
27395 each one used for debugging a different thread, and the frontend might
27396 want to access additional threads for internal purposes. This
27397 increases the risk that by relying on implicitly selected thread, the
27398 frontend may be operating on a wrong one. Therefore, each MI command
27399 should explicitly specify which thread and frame to operate on. To
27400 make it possible, each MI command accepts the @samp{--thread} and
27401 @samp{--frame} options, the value to each is @value{GDBN} global
27402 identifier for thread and frame to operate on.
27404 Usually, each top-level window in a frontend allows the user to select
27405 a thread and a frame, and remembers the user selection for further
27406 operations. However, in some cases @value{GDBN} may suggest that the
27407 current thread or frame be changed. For example, when stopping on a
27408 breakpoint it is reasonable to switch to the thread where breakpoint is
27409 hit. For another example, if the user issues the CLI @samp{thread} or
27410 @samp{frame} commands via the frontend, it is desirable to change the
27411 frontend's selection to the one specified by user. @value{GDBN}
27412 communicates the suggestion to change current thread and frame using the
27413 @samp{=thread-selected} notification.
27415 Note that historically, MI shares the selected thread with CLI, so
27416 frontends used the @code{-thread-select} to execute commands in the
27417 right context. However, getting this to work right is cumbersome. The
27418 simplest way is for frontend to emit @code{-thread-select} command
27419 before every command. This doubles the number of commands that need
27420 to be sent. The alternative approach is to suppress @code{-thread-select}
27421 if the selected thread in @value{GDBN} is supposed to be identical to the
27422 thread the frontend wants to operate on. However, getting this
27423 optimization right can be tricky. In particular, if the frontend
27424 sends several commands to @value{GDBN}, and one of the commands changes the
27425 selected thread, then the behaviour of subsequent commands will
27426 change. So, a frontend should either wait for response from such
27427 problematic commands, or explicitly add @code{-thread-select} for
27428 all subsequent commands. No frontend is known to do this exactly
27429 right, so it is suggested to just always pass the @samp{--thread} and
27430 @samp{--frame} options.
27432 @subsubsection Language
27434 The execution of several commands depends on which language is selected.
27435 By default, the current language (@pxref{show language}) is used.
27436 But for commands known to be language-sensitive, it is recommended
27437 to use the @samp{--language} option. This option takes one argument,
27438 which is the name of the language to use while executing the command.
27442 -data-evaluate-expression --language c "sizeof (void*)"
27447 The valid language names are the same names accepted by the
27448 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
27449 @samp{local} or @samp{unknown}.
27451 @node Asynchronous and non-stop modes
27452 @subsection Asynchronous command execution and non-stop mode
27454 On some targets, @value{GDBN} is capable of processing MI commands
27455 even while the target is running. This is called @dfn{asynchronous
27456 command execution} (@pxref{Background Execution}). The frontend may
27457 specify a preferrence for asynchronous execution using the
27458 @code{-gdb-set mi-async 1} command, which should be emitted before
27459 either running the executable or attaching to the target. After the
27460 frontend has started the executable or attached to the target, it can
27461 find if asynchronous execution is enabled using the
27462 @code{-list-target-features} command.
27465 @item -gdb-set mi-async on
27466 @item -gdb-set mi-async off
27467 Set whether MI is in asynchronous mode.
27469 When @code{off}, which is the default, MI execution commands (e.g.,
27470 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
27471 for the program to stop before processing further commands.
27473 When @code{on}, MI execution commands are background execution
27474 commands (e.g., @code{-exec-continue} becomes the equivalent of the
27475 @code{c&} CLI command), and so @value{GDBN} is capable of processing
27476 MI commands even while the target is running.
27478 @item -gdb-show mi-async
27479 Show whether MI asynchronous mode is enabled.
27482 Note: In @value{GDBN} version 7.7 and earlier, this option was called
27483 @code{target-async} instead of @code{mi-async}, and it had the effect
27484 of both putting MI in asynchronous mode and making CLI background
27485 commands possible. CLI background commands are now always possible
27486 ``out of the box'' if the target supports them. The old spelling is
27487 kept as a deprecated alias for backwards compatibility.
27489 Even if @value{GDBN} can accept a command while target is running,
27490 many commands that access the target do not work when the target is
27491 running. Therefore, asynchronous command execution is most useful
27492 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27493 it is possible to examine the state of one thread, while other threads
27496 When a given thread is running, MI commands that try to access the
27497 target in the context of that thread may not work, or may work only on
27498 some targets. In particular, commands that try to operate on thread's
27499 stack will not work, on any target. Commands that read memory, or
27500 modify breakpoints, may work or not work, depending on the target. Note
27501 that even commands that operate on global state, such as @code{print},
27502 @code{set}, and breakpoint commands, still access the target in the
27503 context of a specific thread, so frontend should try to find a
27504 stopped thread and perform the operation on that thread (using the
27505 @samp{--thread} option).
27507 Which commands will work in the context of a running thread is
27508 highly target dependent. However, the two commands
27509 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27510 to find the state of a thread, will always work.
27512 @node Thread groups
27513 @subsection Thread groups
27514 @value{GDBN} may be used to debug several processes at the same time.
27515 On some platfroms, @value{GDBN} may support debugging of several
27516 hardware systems, each one having several cores with several different
27517 processes running on each core. This section describes the MI
27518 mechanism to support such debugging scenarios.
27520 The key observation is that regardless of the structure of the
27521 target, MI can have a global list of threads, because most commands that
27522 accept the @samp{--thread} option do not need to know what process that
27523 thread belongs to. Therefore, it is not necessary to introduce
27524 neither additional @samp{--process} option, nor an notion of the
27525 current process in the MI interface. The only strictly new feature
27526 that is required is the ability to find how the threads are grouped
27529 To allow the user to discover such grouping, and to support arbitrary
27530 hierarchy of machines/cores/processes, MI introduces the concept of a
27531 @dfn{thread group}. Thread group is a collection of threads and other
27532 thread groups. A thread group always has a string identifier, a type,
27533 and may have additional attributes specific to the type. A new
27534 command, @code{-list-thread-groups}, returns the list of top-level
27535 thread groups, which correspond to processes that @value{GDBN} is
27536 debugging at the moment. By passing an identifier of a thread group
27537 to the @code{-list-thread-groups} command, it is possible to obtain
27538 the members of specific thread group.
27540 To allow the user to easily discover processes, and other objects, he
27541 wishes to debug, a concept of @dfn{available thread group} is
27542 introduced. Available thread group is an thread group that
27543 @value{GDBN} is not debugging, but that can be attached to, using the
27544 @code{-target-attach} command. The list of available top-level thread
27545 groups can be obtained using @samp{-list-thread-groups --available}.
27546 In general, the content of a thread group may be only retrieved only
27547 after attaching to that thread group.
27549 Thread groups are related to inferiors (@pxref{Inferiors and
27550 Programs}). Each inferior corresponds to a thread group of a special
27551 type @samp{process}, and some additional operations are permitted on
27552 such thread groups.
27554 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27555 @node GDB/MI Command Syntax
27556 @section @sc{gdb/mi} Command Syntax
27559 * GDB/MI Input Syntax::
27560 * GDB/MI Output Syntax::
27563 @node GDB/MI Input Syntax
27564 @subsection @sc{gdb/mi} Input Syntax
27566 @cindex input syntax for @sc{gdb/mi}
27567 @cindex @sc{gdb/mi}, input syntax
27569 @item @var{command} @expansion{}
27570 @code{@var{cli-command} | @var{mi-command}}
27572 @item @var{cli-command} @expansion{}
27573 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27574 @var{cli-command} is any existing @value{GDBN} CLI command.
27576 @item @var{mi-command} @expansion{}
27577 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27578 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27580 @item @var{token} @expansion{}
27581 "any sequence of digits"
27583 @item @var{option} @expansion{}
27584 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27586 @item @var{parameter} @expansion{}
27587 @code{@var{non-blank-sequence} | @var{c-string}}
27589 @item @var{operation} @expansion{}
27590 @emph{any of the operations described in this chapter}
27592 @item @var{non-blank-sequence} @expansion{}
27593 @emph{anything, provided it doesn't contain special characters such as
27594 "-", @var{nl}, """ and of course " "}
27596 @item @var{c-string} @expansion{}
27597 @code{""" @var{seven-bit-iso-c-string-content} """}
27599 @item @var{nl} @expansion{}
27608 The CLI commands are still handled by the @sc{mi} interpreter; their
27609 output is described below.
27612 The @code{@var{token}}, when present, is passed back when the command
27616 Some @sc{mi} commands accept optional arguments as part of the parameter
27617 list. Each option is identified by a leading @samp{-} (dash) and may be
27618 followed by an optional argument parameter. Options occur first in the
27619 parameter list and can be delimited from normal parameters using
27620 @samp{--} (this is useful when some parameters begin with a dash).
27627 We want easy access to the existing CLI syntax (for debugging).
27630 We want it to be easy to spot a @sc{mi} operation.
27633 @node GDB/MI Output Syntax
27634 @subsection @sc{gdb/mi} Output Syntax
27636 @cindex output syntax of @sc{gdb/mi}
27637 @cindex @sc{gdb/mi}, output syntax
27638 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27639 followed, optionally, by a single result record. This result record
27640 is for the most recent command. The sequence of output records is
27641 terminated by @samp{(gdb)}.
27643 If an input command was prefixed with a @code{@var{token}} then the
27644 corresponding output for that command will also be prefixed by that same
27648 @item @var{output} @expansion{}
27649 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27651 @item @var{result-record} @expansion{}
27652 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27654 @item @var{out-of-band-record} @expansion{}
27655 @code{@var{async-record} | @var{stream-record}}
27657 @item @var{async-record} @expansion{}
27658 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27660 @item @var{exec-async-output} @expansion{}
27661 @code{[ @var{token} ] "*" @var{async-output nl}}
27663 @item @var{status-async-output} @expansion{}
27664 @code{[ @var{token} ] "+" @var{async-output nl}}
27666 @item @var{notify-async-output} @expansion{}
27667 @code{[ @var{token} ] "=" @var{async-output nl}}
27669 @item @var{async-output} @expansion{}
27670 @code{@var{async-class} ( "," @var{result} )*}
27672 @item @var{result-class} @expansion{}
27673 @code{"done" | "running" | "connected" | "error" | "exit"}
27675 @item @var{async-class} @expansion{}
27676 @code{"stopped" | @var{others}} (where @var{others} will be added
27677 depending on the needs---this is still in development).
27679 @item @var{result} @expansion{}
27680 @code{ @var{variable} "=" @var{value}}
27682 @item @var{variable} @expansion{}
27683 @code{ @var{string} }
27685 @item @var{value} @expansion{}
27686 @code{ @var{const} | @var{tuple} | @var{list} }
27688 @item @var{const} @expansion{}
27689 @code{@var{c-string}}
27691 @item @var{tuple} @expansion{}
27692 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27694 @item @var{list} @expansion{}
27695 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27696 @var{result} ( "," @var{result} )* "]" }
27698 @item @var{stream-record} @expansion{}
27699 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27701 @item @var{console-stream-output} @expansion{}
27702 @code{"~" @var{c-string nl}}
27704 @item @var{target-stream-output} @expansion{}
27705 @code{"@@" @var{c-string nl}}
27707 @item @var{log-stream-output} @expansion{}
27708 @code{"&" @var{c-string nl}}
27710 @item @var{nl} @expansion{}
27713 @item @var{token} @expansion{}
27714 @emph{any sequence of digits}.
27722 All output sequences end in a single line containing a period.
27725 The @code{@var{token}} is from the corresponding request. Note that
27726 for all async output, while the token is allowed by the grammar and
27727 may be output by future versions of @value{GDBN} for select async
27728 output messages, it is generally omitted. Frontends should treat
27729 all async output as reporting general changes in the state of the
27730 target and there should be no need to associate async output to any
27734 @cindex status output in @sc{gdb/mi}
27735 @var{status-async-output} contains on-going status information about the
27736 progress of a slow operation. It can be discarded. All status output is
27737 prefixed by @samp{+}.
27740 @cindex async output in @sc{gdb/mi}
27741 @var{exec-async-output} contains asynchronous state change on the target
27742 (stopped, started, disappeared). All async output is prefixed by
27746 @cindex notify output in @sc{gdb/mi}
27747 @var{notify-async-output} contains supplementary information that the
27748 client should handle (e.g., a new breakpoint information). All notify
27749 output is prefixed by @samp{=}.
27752 @cindex console output in @sc{gdb/mi}
27753 @var{console-stream-output} is output that should be displayed as is in the
27754 console. It is the textual response to a CLI command. All the console
27755 output is prefixed by @samp{~}.
27758 @cindex target output in @sc{gdb/mi}
27759 @var{target-stream-output} is the output produced by the target program.
27760 All the target output is prefixed by @samp{@@}.
27763 @cindex log output in @sc{gdb/mi}
27764 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27765 instance messages that should be displayed as part of an error log. All
27766 the log output is prefixed by @samp{&}.
27769 @cindex list output in @sc{gdb/mi}
27770 New @sc{gdb/mi} commands should only output @var{lists} containing
27776 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27777 details about the various output records.
27779 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27780 @node GDB/MI Compatibility with CLI
27781 @section @sc{gdb/mi} Compatibility with CLI
27783 @cindex compatibility, @sc{gdb/mi} and CLI
27784 @cindex @sc{gdb/mi}, compatibility with CLI
27786 For the developers convenience CLI commands can be entered directly,
27787 but there may be some unexpected behaviour. For example, commands
27788 that query the user will behave as if the user replied yes, breakpoint
27789 command lists are not executed and some CLI commands, such as
27790 @code{if}, @code{when} and @code{define}, prompt for further input with
27791 @samp{>}, which is not valid MI output.
27793 This feature may be removed at some stage in the future and it is
27794 recommended that front ends use the @code{-interpreter-exec} command
27795 (@pxref{-interpreter-exec}).
27797 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27798 @node GDB/MI Development and Front Ends
27799 @section @sc{gdb/mi} Development and Front Ends
27800 @cindex @sc{gdb/mi} development
27802 The application which takes the MI output and presents the state of the
27803 program being debugged to the user is called a @dfn{front end}.
27805 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
27806 to the MI interface may break existing usage. This section describes how the
27807 protocol changes and how to request previous version of the protocol when it
27810 Some changes in MI need not break a carefully designed front end, and
27811 for these the MI version will remain unchanged. The following is a
27812 list of changes that may occur within one level, so front ends should
27813 parse MI output in a way that can handle them:
27817 New MI commands may be added.
27820 New fields may be added to the output of any MI command.
27823 The range of values for fields with specified values, e.g.,
27824 @code{in_scope} (@pxref{-var-update}) may be extended.
27826 @c The format of field's content e.g type prefix, may change so parse it
27827 @c at your own risk. Yes, in general?
27829 @c The order of fields may change? Shouldn't really matter but it might
27830 @c resolve inconsistencies.
27833 If the changes are likely to break front ends, the MI version level
27834 will be increased by one. The new versions of the MI protocol are not compatible
27835 with the old versions. Old versions of MI remain available, allowing front ends
27836 to keep using them until they are modified to use the latest MI version.
27838 Since @code{--interpreter=mi} always points to the latest MI version, it is
27839 recommended that front ends request a specific version of MI when launching
27840 @value{GDBN} (e.g. @code{--interpreter=mi2}) to make sure they get an
27841 interpreter with the MI version they expect.
27843 The following table gives a summary of the the released versions of the MI
27844 interface: the version number, the version of GDB in which it first appeared
27845 and the breaking changes compared to the previous version.
27847 @multitable @columnfractions .05 .05 .9
27848 @headitem MI version @tab GDB version @tab Breaking changes
27865 The @code{-environment-pwd}, @code{-environment-directory} and
27866 @code{-environment-path} commands now returns values using the MI output
27867 syntax, rather than CLI output syntax.
27870 @code{-var-list-children}'s @code{children} result field is now a list, rather
27874 @code{-var-update}'s @code{changelist} result field is now a list, rather than
27886 The output of information about multi-location breakpoints has changed in the
27887 responses to the @code{-break-insert} and @code{-break-info} commands, as well
27888 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
27889 The multiple locations are now placed in a @code{locations} field, whose value
27895 If your front end cannot yet migrate to a more recent version of the
27896 MI protocol, you can nevertheless selectively enable specific features
27897 available in those recent MI versions, using the following commands:
27901 @item -fix-multi-location-breakpoint-output
27902 Use the output for multi-location breakpoints which was introduced by
27903 MI 3, even when using MI versions 2 or 1. This command has no
27904 effect when using MI version 3 or later.
27908 The best way to avoid unexpected changes in MI that might break your front
27909 end is to make your project known to @value{GDBN} developers and
27910 follow development on @email{gdb@@sourceware.org} and
27911 @email{gdb-patches@@sourceware.org}.
27912 @cindex mailing lists
27914 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27915 @node GDB/MI Output Records
27916 @section @sc{gdb/mi} Output Records
27919 * GDB/MI Result Records::
27920 * GDB/MI Stream Records::
27921 * GDB/MI Async Records::
27922 * GDB/MI Breakpoint Information::
27923 * GDB/MI Frame Information::
27924 * GDB/MI Thread Information::
27925 * GDB/MI Ada Exception Information::
27928 @node GDB/MI Result Records
27929 @subsection @sc{gdb/mi} Result Records
27931 @cindex result records in @sc{gdb/mi}
27932 @cindex @sc{gdb/mi}, result records
27933 In addition to a number of out-of-band notifications, the response to a
27934 @sc{gdb/mi} command includes one of the following result indications:
27938 @item "^done" [ "," @var{results} ]
27939 The synchronous operation was successful, @code{@var{results}} are the return
27944 This result record is equivalent to @samp{^done}. Historically, it
27945 was output instead of @samp{^done} if the command has resumed the
27946 target. This behaviour is maintained for backward compatibility, but
27947 all frontends should treat @samp{^done} and @samp{^running}
27948 identically and rely on the @samp{*running} output record to determine
27949 which threads are resumed.
27953 @value{GDBN} has connected to a remote target.
27955 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
27957 The operation failed. The @code{msg=@var{c-string}} variable contains
27958 the corresponding error message.
27960 If present, the @code{code=@var{c-string}} variable provides an error
27961 code on which consumers can rely on to detect the corresponding
27962 error condition. At present, only one error code is defined:
27965 @item "undefined-command"
27966 Indicates that the command causing the error does not exist.
27971 @value{GDBN} has terminated.
27975 @node GDB/MI Stream Records
27976 @subsection @sc{gdb/mi} Stream Records
27978 @cindex @sc{gdb/mi}, stream records
27979 @cindex stream records in @sc{gdb/mi}
27980 @value{GDBN} internally maintains a number of output streams: the console, the
27981 target, and the log. The output intended for each of these streams is
27982 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27984 Each stream record begins with a unique @dfn{prefix character} which
27985 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27986 Syntax}). In addition to the prefix, each stream record contains a
27987 @code{@var{string-output}}. This is either raw text (with an implicit new
27988 line) or a quoted C string (which does not contain an implicit newline).
27991 @item "~" @var{string-output}
27992 The console output stream contains text that should be displayed in the
27993 CLI console window. It contains the textual responses to CLI commands.
27995 @item "@@" @var{string-output}
27996 The target output stream contains any textual output from the running
27997 target. This is only present when GDB's event loop is truly
27998 asynchronous, which is currently only the case for remote targets.
28000 @item "&" @var{string-output}
28001 The log stream contains debugging messages being produced by @value{GDBN}'s
28005 @node GDB/MI Async Records
28006 @subsection @sc{gdb/mi} Async Records
28008 @cindex async records in @sc{gdb/mi}
28009 @cindex @sc{gdb/mi}, async records
28010 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
28011 additional changes that have occurred. Those changes can either be a
28012 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
28013 target activity (e.g., target stopped).
28015 The following is the list of possible async records:
28019 @item *running,thread-id="@var{thread}"
28020 The target is now running. The @var{thread} field can be the global
28021 thread ID of the the thread that is now running, and it can be
28022 @samp{all} if all threads are running. The frontend should assume
28023 that no interaction with a running thread is possible after this
28024 notification is produced. The frontend should not assume that this
28025 notification is output only once for any command. @value{GDBN} may
28026 emit this notification several times, either for different threads,
28027 because it cannot resume all threads together, or even for a single
28028 thread, if the thread must be stepped though some code before letting
28031 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
28032 The target has stopped. The @var{reason} field can have one of the
28036 @item breakpoint-hit
28037 A breakpoint was reached.
28038 @item watchpoint-trigger
28039 A watchpoint was triggered.
28040 @item read-watchpoint-trigger
28041 A read watchpoint was triggered.
28042 @item access-watchpoint-trigger
28043 An access watchpoint was triggered.
28044 @item function-finished
28045 An -exec-finish or similar CLI command was accomplished.
28046 @item location-reached
28047 An -exec-until or similar CLI command was accomplished.
28048 @item watchpoint-scope
28049 A watchpoint has gone out of scope.
28050 @item end-stepping-range
28051 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
28052 similar CLI command was accomplished.
28053 @item exited-signalled
28054 The inferior exited because of a signal.
28056 The inferior exited.
28057 @item exited-normally
28058 The inferior exited normally.
28059 @item signal-received
28060 A signal was received by the inferior.
28062 The inferior has stopped due to a library being loaded or unloaded.
28063 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
28064 set or when a @code{catch load} or @code{catch unload} catchpoint is
28065 in use (@pxref{Set Catchpoints}).
28067 The inferior has forked. This is reported when @code{catch fork}
28068 (@pxref{Set Catchpoints}) has been used.
28070 The inferior has vforked. This is reported in when @code{catch vfork}
28071 (@pxref{Set Catchpoints}) has been used.
28072 @item syscall-entry
28073 The inferior entered a system call. This is reported when @code{catch
28074 syscall} (@pxref{Set Catchpoints}) has been used.
28075 @item syscall-return
28076 The inferior returned from a system call. This is reported when
28077 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
28079 The inferior called @code{exec}. This is reported when @code{catch exec}
28080 (@pxref{Set Catchpoints}) has been used.
28083 The @var{id} field identifies the global thread ID of the thread
28084 that directly caused the stop -- for example by hitting a breakpoint.
28085 Depending on whether all-stop
28086 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
28087 stop all threads, or only the thread that directly triggered the stop.
28088 If all threads are stopped, the @var{stopped} field will have the
28089 value of @code{"all"}. Otherwise, the value of the @var{stopped}
28090 field will be a list of thread identifiers. Presently, this list will
28091 always include a single thread, but frontend should be prepared to see
28092 several threads in the list. The @var{core} field reports the
28093 processor core on which the stop event has happened. This field may be absent
28094 if such information is not available.
28096 @item =thread-group-added,id="@var{id}"
28097 @itemx =thread-group-removed,id="@var{id}"
28098 A thread group was either added or removed. The @var{id} field
28099 contains the @value{GDBN} identifier of the thread group. When a thread
28100 group is added, it generally might not be associated with a running
28101 process. When a thread group is removed, its id becomes invalid and
28102 cannot be used in any way.
28104 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
28105 A thread group became associated with a running program,
28106 either because the program was just started or the thread group
28107 was attached to a program. The @var{id} field contains the
28108 @value{GDBN} identifier of the thread group. The @var{pid} field
28109 contains process identifier, specific to the operating system.
28111 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
28112 A thread group is no longer associated with a running program,
28113 either because the program has exited, or because it was detached
28114 from. The @var{id} field contains the @value{GDBN} identifier of the
28115 thread group. The @var{code} field is the exit code of the inferior; it exists
28116 only when the inferior exited with some code.
28118 @item =thread-created,id="@var{id}",group-id="@var{gid}"
28119 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
28120 A thread either was created, or has exited. The @var{id} field
28121 contains the global @value{GDBN} identifier of the thread. The @var{gid}
28122 field identifies the thread group this thread belongs to.
28124 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
28125 Informs that the selected thread or frame were changed. This notification
28126 is not emitted as result of the @code{-thread-select} or
28127 @code{-stack-select-frame} commands, but is emitted whenever an MI command
28128 that is not documented to change the selected thread and frame actually
28129 changes them. In particular, invoking, directly or indirectly
28130 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
28131 will generate this notification. Changing the thread or frame from another
28132 user interface (see @ref{Interpreters}) will also generate this notification.
28134 The @var{frame} field is only present if the newly selected thread is
28135 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
28137 We suggest that in response to this notification, front ends
28138 highlight the selected thread and cause subsequent commands to apply to
28141 @item =library-loaded,...
28142 Reports that a new library file was loaded by the program. This
28143 notification has 5 fields---@var{id}, @var{target-name},
28144 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
28145 opaque identifier of the library. For remote debugging case,
28146 @var{target-name} and @var{host-name} fields give the name of the
28147 library file on the target, and on the host respectively. For native
28148 debugging, both those fields have the same value. The
28149 @var{symbols-loaded} field is emitted only for backward compatibility
28150 and should not be relied on to convey any useful information. The
28151 @var{thread-group} field, if present, specifies the id of the thread
28152 group in whose context the library was loaded. If the field is
28153 absent, it means the library was loaded in the context of all present
28154 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
28157 @item =library-unloaded,...
28158 Reports that a library was unloaded by the program. This notification
28159 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
28160 the same meaning as for the @code{=library-loaded} notification.
28161 The @var{thread-group} field, if present, specifies the id of the
28162 thread group in whose context the library was unloaded. If the field is
28163 absent, it means the library was unloaded in the context of all present
28166 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
28167 @itemx =traceframe-changed,end
28168 Reports that the trace frame was changed and its new number is
28169 @var{tfnum}. The number of the tracepoint associated with this trace
28170 frame is @var{tpnum}.
28172 @item =tsv-created,name=@var{name},initial=@var{initial}
28173 Reports that the new trace state variable @var{name} is created with
28174 initial value @var{initial}.
28176 @item =tsv-deleted,name=@var{name}
28177 @itemx =tsv-deleted
28178 Reports that the trace state variable @var{name} is deleted or all
28179 trace state variables are deleted.
28181 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28182 Reports that the trace state variable @var{name} is modified with
28183 the initial value @var{initial}. The current value @var{current} of
28184 trace state variable is optional and is reported if the current
28185 value of trace state variable is known.
28187 @item =breakpoint-created,bkpt=@{...@}
28188 @itemx =breakpoint-modified,bkpt=@{...@}
28189 @itemx =breakpoint-deleted,id=@var{number}
28190 Reports that a breakpoint was created, modified, or deleted,
28191 respectively. Only user-visible breakpoints are reported to the MI
28194 The @var{bkpt} argument is of the same form as returned by the various
28195 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28196 @var{number} is the ordinal number of the breakpoint.
28198 Note that if a breakpoint is emitted in the result record of a
28199 command, then it will not also be emitted in an async record.
28201 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
28202 @itemx =record-stopped,thread-group="@var{id}"
28203 Execution log recording was either started or stopped on an
28204 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28205 group corresponding to the affected inferior.
28207 The @var{method} field indicates the method used to record execution. If the
28208 method in use supports multiple recording formats, @var{format} will be present
28209 and contain the currently used format. @xref{Process Record and Replay},
28210 for existing method and format values.
28212 @item =cmd-param-changed,param=@var{param},value=@var{value}
28213 Reports that a parameter of the command @code{set @var{param}} is
28214 changed to @var{value}. In the multi-word @code{set} command,
28215 the @var{param} is the whole parameter list to @code{set} command.
28216 For example, In command @code{set check type on}, @var{param}
28217 is @code{check type} and @var{value} is @code{on}.
28219 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28220 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28221 written in an inferior. The @var{id} is the identifier of the
28222 thread group corresponding to the affected inferior. The optional
28223 @code{type="code"} part is reported if the memory written to holds
28227 @node GDB/MI Breakpoint Information
28228 @subsection @sc{gdb/mi} Breakpoint Information
28230 When @value{GDBN} reports information about a breakpoint, a
28231 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28236 The breakpoint number.
28239 The type of the breakpoint. For ordinary breakpoints this will be
28240 @samp{breakpoint}, but many values are possible.
28243 If the type of the breakpoint is @samp{catchpoint}, then this
28244 indicates the exact type of catchpoint.
28247 This is the breakpoint disposition---either @samp{del}, meaning that
28248 the breakpoint will be deleted at the next stop, or @samp{keep},
28249 meaning that the breakpoint will not be deleted.
28252 This indicates whether the breakpoint is enabled, in which case the
28253 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28254 Note that this is not the same as the field @code{enable}.
28257 The address of the breakpoint. This may be a hexidecimal number,
28258 giving the address; or the string @samp{<PENDING>}, for a pending
28259 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28260 multiple locations. This field will not be present if no address can
28261 be determined. For example, a watchpoint does not have an address.
28264 If known, the function in which the breakpoint appears.
28265 If not known, this field is not present.
28268 The name of the source file which contains this function, if known.
28269 If not known, this field is not present.
28272 The full file name of the source file which contains this function, if
28273 known. If not known, this field is not present.
28276 The line number at which this breakpoint appears, if known.
28277 If not known, this field is not present.
28280 If the source file is not known, this field may be provided. If
28281 provided, this holds the address of the breakpoint, possibly followed
28285 If this breakpoint is pending, this field is present and holds the
28286 text used to set the breakpoint, as entered by the user.
28289 Where this breakpoint's condition is evaluated, either @samp{host} or
28293 If this is a thread-specific breakpoint, then this identifies the
28294 thread in which the breakpoint can trigger.
28297 If this breakpoint is restricted to a particular Ada task, then this
28298 field will hold the task identifier.
28301 If the breakpoint is conditional, this is the condition expression.
28304 The ignore count of the breakpoint.
28307 The enable count of the breakpoint.
28309 @item traceframe-usage
28312 @item static-tracepoint-marker-string-id
28313 For a static tracepoint, the name of the static tracepoint marker.
28316 For a masked watchpoint, this is the mask.
28319 A tracepoint's pass count.
28321 @item original-location
28322 The location of the breakpoint as originally specified by the user.
28323 This field is optional.
28326 The number of times the breakpoint has been hit.
28329 This field is only given for tracepoints. This is either @samp{y},
28330 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28334 Some extra data, the exact contents of which are type-dependent.
28337 This field is present if the breakpoint has multiple locations. It is also
28338 exceptionally present if the breakpoint is enabled and has a single, disabled
28341 The value is a list of locations. The format of a location is decribed below.
28345 A location in a multi-location breakpoint is represented as a tuple with the
28351 The location number as a dotted pair, like @samp{1.2}. The first digit is the
28352 number of the parent breakpoint. The second digit is the number of the
28353 location within that breakpoint.
28356 This indicates whether the location is enabled, in which case the
28357 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28358 Note that this is not the same as the field @code{enable}.
28361 The address of this location as an hexidecimal number.
28364 If known, the function in which the location appears.
28365 If not known, this field is not present.
28368 The name of the source file which contains this location, if known.
28369 If not known, this field is not present.
28372 The full file name of the source file which contains this location, if
28373 known. If not known, this field is not present.
28376 The line number at which this location appears, if known.
28377 If not known, this field is not present.
28379 @item thread-groups
28380 The thread groups this location is in.
28384 For example, here is what the output of @code{-break-insert}
28385 (@pxref{GDB/MI Breakpoint Commands}) might be:
28388 -> -break-insert main
28389 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28390 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28391 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28396 @node GDB/MI Frame Information
28397 @subsection @sc{gdb/mi} Frame Information
28399 Response from many MI commands includes an information about stack
28400 frame. This information is a tuple that may have the following
28405 The level of the stack frame. The innermost frame has the level of
28406 zero. This field is always present.
28409 The name of the function corresponding to the frame. This field may
28410 be absent if @value{GDBN} is unable to determine the function name.
28413 The code address for the frame. This field is always present.
28416 The name of the source files that correspond to the frame's code
28417 address. This field may be absent.
28420 The source line corresponding to the frames' code address. This field
28424 The name of the binary file (either executable or shared library) the
28425 corresponds to the frame's code address. This field may be absent.
28429 @node GDB/MI Thread Information
28430 @subsection @sc{gdb/mi} Thread Information
28432 Whenever @value{GDBN} has to report an information about a thread, it
28433 uses a tuple with the following fields. The fields are always present unless
28438 The global numeric id assigned to the thread by @value{GDBN}.
28441 The target-specific string identifying the thread.
28444 Additional information about the thread provided by the target.
28445 It is supposed to be human-readable and not interpreted by the
28446 frontend. This field is optional.
28449 The name of the thread. If the user specified a name using the
28450 @code{thread name} command, then this name is given. Otherwise, if
28451 @value{GDBN} can extract the thread name from the target, then that
28452 name is given. If @value{GDBN} cannot find the thread name, then this
28456 The execution state of the thread, either @samp{stopped} or @samp{running},
28457 depending on whether the thread is presently running.
28460 The stack frame currently executing in the thread. This field is only present
28461 if the thread is stopped. Its format is documented in
28462 @ref{GDB/MI Frame Information}.
28465 The value of this field is an integer number of the processor core the
28466 thread was last seen on. This field is optional.
28469 @node GDB/MI Ada Exception Information
28470 @subsection @sc{gdb/mi} Ada Exception Information
28472 Whenever a @code{*stopped} record is emitted because the program
28473 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28474 @value{GDBN} provides the name of the exception that was raised via
28475 the @code{exception-name} field. Also, for exceptions that were raised
28476 with an exception message, @value{GDBN} provides that message via
28477 the @code{exception-message} field.
28479 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28480 @node GDB/MI Simple Examples
28481 @section Simple Examples of @sc{gdb/mi} Interaction
28482 @cindex @sc{gdb/mi}, simple examples
28484 This subsection presents several simple examples of interaction using
28485 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28486 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28487 the output received from @sc{gdb/mi}.
28489 Note the line breaks shown in the examples are here only for
28490 readability, they don't appear in the real output.
28492 @subheading Setting a Breakpoint
28494 Setting a breakpoint generates synchronous output which contains detailed
28495 information of the breakpoint.
28498 -> -break-insert main
28499 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28500 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28501 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28506 @subheading Program Execution
28508 Program execution generates asynchronous records and MI gives the
28509 reason that execution stopped.
28515 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28516 frame=@{addr="0x08048564",func="main",
28517 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28518 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
28519 arch="i386:x86_64"@}
28524 <- *stopped,reason="exited-normally"
28528 @subheading Quitting @value{GDBN}
28530 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28538 Please note that @samp{^exit} is printed immediately, but it might
28539 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28540 performs necessary cleanups, including killing programs being debugged
28541 or disconnecting from debug hardware, so the frontend should wait till
28542 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28543 fails to exit in reasonable time.
28545 @subheading A Bad Command
28547 Here's what happens if you pass a non-existent command:
28551 <- ^error,msg="Undefined MI command: rubbish"
28556 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28557 @node GDB/MI Command Description Format
28558 @section @sc{gdb/mi} Command Description Format
28560 The remaining sections describe blocks of commands. Each block of
28561 commands is laid out in a fashion similar to this section.
28563 @subheading Motivation
28565 The motivation for this collection of commands.
28567 @subheading Introduction
28569 A brief introduction to this collection of commands as a whole.
28571 @subheading Commands
28573 For each command in the block, the following is described:
28575 @subsubheading Synopsis
28578 -command @var{args}@dots{}
28581 @subsubheading Result
28583 @subsubheading @value{GDBN} Command
28585 The corresponding @value{GDBN} CLI command(s), if any.
28587 @subsubheading Example
28589 Example(s) formatted for readability. Some of the described commands have
28590 not been implemented yet and these are labeled N.A.@: (not available).
28593 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28594 @node GDB/MI Breakpoint Commands
28595 @section @sc{gdb/mi} Breakpoint Commands
28597 @cindex breakpoint commands for @sc{gdb/mi}
28598 @cindex @sc{gdb/mi}, breakpoint commands
28599 This section documents @sc{gdb/mi} commands for manipulating
28602 @subheading The @code{-break-after} Command
28603 @findex -break-after
28605 @subsubheading Synopsis
28608 -break-after @var{number} @var{count}
28611 The breakpoint number @var{number} is not in effect until it has been
28612 hit @var{count} times. To see how this is reflected in the output of
28613 the @samp{-break-list} command, see the description of the
28614 @samp{-break-list} command below.
28616 @subsubheading @value{GDBN} Command
28618 The corresponding @value{GDBN} command is @samp{ignore}.
28620 @subsubheading Example
28625 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28626 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28627 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28635 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28636 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28637 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28638 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28639 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28640 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28641 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28642 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28643 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28644 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28649 @subheading The @code{-break-catch} Command
28650 @findex -break-catch
28653 @subheading The @code{-break-commands} Command
28654 @findex -break-commands
28656 @subsubheading Synopsis
28659 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28662 Specifies the CLI commands that should be executed when breakpoint
28663 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28664 are the commands. If no command is specified, any previously-set
28665 commands are cleared. @xref{Break Commands}. Typical use of this
28666 functionality is tracing a program, that is, printing of values of
28667 some variables whenever breakpoint is hit and then continuing.
28669 @subsubheading @value{GDBN} Command
28671 The corresponding @value{GDBN} command is @samp{commands}.
28673 @subsubheading Example
28678 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28679 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28680 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28683 -break-commands 1 "print v" "continue"
28688 @subheading The @code{-break-condition} Command
28689 @findex -break-condition
28691 @subsubheading Synopsis
28694 -break-condition @var{number} @var{expr}
28697 Breakpoint @var{number} will stop the program only if the condition in
28698 @var{expr} is true. The condition becomes part of the
28699 @samp{-break-list} output (see the description of the @samp{-break-list}
28702 @subsubheading @value{GDBN} Command
28704 The corresponding @value{GDBN} command is @samp{condition}.
28706 @subsubheading Example
28710 -break-condition 1 1
28714 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28715 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28716 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28717 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28718 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28719 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28720 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28721 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28722 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28723 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28727 @subheading The @code{-break-delete} Command
28728 @findex -break-delete
28730 @subsubheading Synopsis
28733 -break-delete ( @var{breakpoint} )+
28736 Delete the breakpoint(s) whose number(s) are specified in the argument
28737 list. This is obviously reflected in the breakpoint list.
28739 @subsubheading @value{GDBN} Command
28741 The corresponding @value{GDBN} command is @samp{delete}.
28743 @subsubheading Example
28751 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28752 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28753 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28754 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28755 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28756 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28757 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28762 @subheading The @code{-break-disable} Command
28763 @findex -break-disable
28765 @subsubheading Synopsis
28768 -break-disable ( @var{breakpoint} )+
28771 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28772 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28774 @subsubheading @value{GDBN} Command
28776 The corresponding @value{GDBN} command is @samp{disable}.
28778 @subsubheading Example
28786 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28787 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28788 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28789 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28790 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28791 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28792 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28793 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28794 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28795 line="5",thread-groups=["i1"],times="0"@}]@}
28799 @subheading The @code{-break-enable} Command
28800 @findex -break-enable
28802 @subsubheading Synopsis
28805 -break-enable ( @var{breakpoint} )+
28808 Enable (previously disabled) @var{breakpoint}(s).
28810 @subsubheading @value{GDBN} Command
28812 The corresponding @value{GDBN} command is @samp{enable}.
28814 @subsubheading Example
28822 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28823 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28824 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28825 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28826 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28827 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28828 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28829 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28830 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28831 line="5",thread-groups=["i1"],times="0"@}]@}
28835 @subheading The @code{-break-info} Command
28836 @findex -break-info
28838 @subsubheading Synopsis
28841 -break-info @var{breakpoint}
28845 Get information about a single breakpoint.
28847 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28848 Information}, for details on the format of each breakpoint in the
28851 @subsubheading @value{GDBN} Command
28853 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28855 @subsubheading Example
28858 @subheading The @code{-break-insert} Command
28859 @findex -break-insert
28860 @anchor{-break-insert}
28862 @subsubheading Synopsis
28865 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28866 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28867 [ -p @var{thread-id} ] [ @var{location} ]
28871 If specified, @var{location}, can be one of:
28874 @item linespec location
28875 A linespec location. @xref{Linespec Locations}.
28877 @item explicit location
28878 An explicit location. @sc{gdb/mi} explicit locations are
28879 analogous to the CLI's explicit locations using the option names
28880 listed below. @xref{Explicit Locations}.
28883 @item --source @var{filename}
28884 The source file name of the location. This option requires the use
28885 of either @samp{--function} or @samp{--line}.
28887 @item --function @var{function}
28888 The name of a function or method.
28890 @item --label @var{label}
28891 The name of a label.
28893 @item --line @var{lineoffset}
28894 An absolute or relative line offset from the start of the location.
28897 @item address location
28898 An address location, *@var{address}. @xref{Address Locations}.
28902 The possible optional parameters of this command are:
28906 Insert a temporary breakpoint.
28908 Insert a hardware breakpoint.
28910 If @var{location} cannot be parsed (for example if it
28911 refers to unknown files or functions), create a pending
28912 breakpoint. Without this flag, @value{GDBN} will report
28913 an error, and won't create a breakpoint, if @var{location}
28916 Create a disabled breakpoint.
28918 Create a tracepoint. @xref{Tracepoints}. When this parameter
28919 is used together with @samp{-h}, a fast tracepoint is created.
28920 @item -c @var{condition}
28921 Make the breakpoint conditional on @var{condition}.
28922 @item -i @var{ignore-count}
28923 Initialize the @var{ignore-count}.
28924 @item -p @var{thread-id}
28925 Restrict the breakpoint to the thread with the specified global
28929 @subsubheading Result
28931 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28932 resulting breakpoint.
28934 Note: this format is open to change.
28935 @c An out-of-band breakpoint instead of part of the result?
28937 @subsubheading @value{GDBN} Command
28939 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28940 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28942 @subsubheading Example
28947 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28948 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28951 -break-insert -t foo
28952 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28953 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28957 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28958 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28959 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28960 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28961 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28962 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28963 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28964 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28965 addr="0x0001072c", func="main",file="recursive2.c",
28966 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28968 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28969 addr="0x00010774",func="foo",file="recursive2.c",
28970 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28973 @c -break-insert -r foo.*
28974 @c ~int foo(int, int);
28975 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28976 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28981 @subheading The @code{-dprintf-insert} Command
28982 @findex -dprintf-insert
28984 @subsubheading Synopsis
28987 -dprintf-insert [ -t ] [ -f ] [ -d ]
28988 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28989 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
28994 If supplied, @var{location} may be specified the same way as for
28995 the @code{-break-insert} command. @xref{-break-insert}.
28997 The possible optional parameters of this command are:
29001 Insert a temporary breakpoint.
29003 If @var{location} cannot be parsed (for example, if it
29004 refers to unknown files or functions), create a pending
29005 breakpoint. Without this flag, @value{GDBN} will report
29006 an error, and won't create a breakpoint, if @var{location}
29009 Create a disabled breakpoint.
29010 @item -c @var{condition}
29011 Make the breakpoint conditional on @var{condition}.
29012 @item -i @var{ignore-count}
29013 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
29014 to @var{ignore-count}.
29015 @item -p @var{thread-id}
29016 Restrict the breakpoint to the thread with the specified global
29020 @subsubheading Result
29022 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29023 resulting breakpoint.
29025 @c An out-of-band breakpoint instead of part of the result?
29027 @subsubheading @value{GDBN} Command
29029 The corresponding @value{GDBN} command is @samp{dprintf}.
29031 @subsubheading Example
29035 4-dprintf-insert foo "At foo entry\n"
29036 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
29037 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
29038 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
29039 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
29040 original-location="foo"@}
29042 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
29043 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
29044 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
29045 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
29046 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
29047 original-location="mi-dprintf.c:26"@}
29051 @subheading The @code{-break-list} Command
29052 @findex -break-list
29054 @subsubheading Synopsis
29060 Displays the list of inserted breakpoints, showing the following fields:
29064 number of the breakpoint
29066 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
29068 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
29071 is the breakpoint enabled or no: @samp{y} or @samp{n}
29073 memory location at which the breakpoint is set
29075 logical location of the breakpoint, expressed by function name, file
29077 @item Thread-groups
29078 list of thread groups to which this breakpoint applies
29080 number of times the breakpoint has been hit
29083 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
29084 @code{body} field is an empty list.
29086 @subsubheading @value{GDBN} Command
29088 The corresponding @value{GDBN} command is @samp{info break}.
29090 @subsubheading Example
29095 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29096 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29097 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29098 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29099 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29100 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29101 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29102 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29103 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
29105 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
29106 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
29107 line="13",thread-groups=["i1"],times="0"@}]@}
29111 Here's an example of the result when there are no breakpoints:
29116 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
29117 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29118 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29119 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29120 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29121 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29122 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29127 @subheading The @code{-break-passcount} Command
29128 @findex -break-passcount
29130 @subsubheading Synopsis
29133 -break-passcount @var{tracepoint-number} @var{passcount}
29136 Set the passcount for tracepoint @var{tracepoint-number} to
29137 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
29138 is not a tracepoint, error is emitted. This corresponds to CLI
29139 command @samp{passcount}.
29141 @subheading The @code{-break-watch} Command
29142 @findex -break-watch
29144 @subsubheading Synopsis
29147 -break-watch [ -a | -r ]
29150 Create a watchpoint. With the @samp{-a} option it will create an
29151 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
29152 read from or on a write to the memory location. With the @samp{-r}
29153 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
29154 trigger only when the memory location is accessed for reading. Without
29155 either of the options, the watchpoint created is a regular watchpoint,
29156 i.e., it will trigger when the memory location is accessed for writing.
29157 @xref{Set Watchpoints, , Setting Watchpoints}.
29159 Note that @samp{-break-list} will report a single list of watchpoints and
29160 breakpoints inserted.
29162 @subsubheading @value{GDBN} Command
29164 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
29167 @subsubheading Example
29169 Setting a watchpoint on a variable in the @code{main} function:
29174 ^done,wpt=@{number="2",exp="x"@}
29179 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
29180 value=@{old="-268439212",new="55"@},
29181 frame=@{func="main",args=[],file="recursive2.c",
29182 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
29186 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
29187 the program execution twice: first for the variable changing value, then
29188 for the watchpoint going out of scope.
29193 ^done,wpt=@{number="5",exp="C"@}
29198 *stopped,reason="watchpoint-trigger",
29199 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
29200 frame=@{func="callee4",args=[],
29201 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29202 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29203 arch="i386:x86_64"@}
29208 *stopped,reason="watchpoint-scope",wpnum="5",
29209 frame=@{func="callee3",args=[@{name="strarg",
29210 value="0x11940 \"A string argument.\""@}],
29211 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29212 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29213 arch="i386:x86_64"@}
29217 Listing breakpoints and watchpoints, at different points in the program
29218 execution. Note that once the watchpoint goes out of scope, it is
29224 ^done,wpt=@{number="2",exp="C"@}
29227 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29228 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29229 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29230 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29231 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29232 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29233 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29234 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29235 addr="0x00010734",func="callee4",
29236 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29237 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29239 bkpt=@{number="2",type="watchpoint",disp="keep",
29240 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29245 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29246 value=@{old="-276895068",new="3"@},
29247 frame=@{func="callee4",args=[],
29248 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29249 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29250 arch="i386:x86_64"@}
29253 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29254 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29255 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29256 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29257 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29258 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29259 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29260 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29261 addr="0x00010734",func="callee4",
29262 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29263 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29265 bkpt=@{number="2",type="watchpoint",disp="keep",
29266 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29270 ^done,reason="watchpoint-scope",wpnum="2",
29271 frame=@{func="callee3",args=[@{name="strarg",
29272 value="0x11940 \"A string argument.\""@}],
29273 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29274 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29275 arch="i386:x86_64"@}
29278 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29279 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29280 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29281 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29282 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29283 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29284 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29285 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29286 addr="0x00010734",func="callee4",
29287 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29288 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29289 thread-groups=["i1"],times="1"@}]@}
29294 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29295 @node GDB/MI Catchpoint Commands
29296 @section @sc{gdb/mi} Catchpoint Commands
29298 This section documents @sc{gdb/mi} commands for manipulating
29302 * Shared Library GDB/MI Catchpoint Commands::
29303 * Ada Exception GDB/MI Catchpoint Commands::
29306 @node Shared Library GDB/MI Catchpoint Commands
29307 @subsection Shared Library @sc{gdb/mi} Catchpoints
29309 @subheading The @code{-catch-load} Command
29310 @findex -catch-load
29312 @subsubheading Synopsis
29315 -catch-load [ -t ] [ -d ] @var{regexp}
29318 Add a catchpoint for library load events. If the @samp{-t} option is used,
29319 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29320 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29321 in a disabled state. The @samp{regexp} argument is a regular
29322 expression used to match the name of the loaded library.
29325 @subsubheading @value{GDBN} Command
29327 The corresponding @value{GDBN} command is @samp{catch load}.
29329 @subsubheading Example
29332 -catch-load -t foo.so
29333 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29334 what="load of library matching foo.so",catch-type="load",times="0"@}
29339 @subheading The @code{-catch-unload} Command
29340 @findex -catch-unload
29342 @subsubheading Synopsis
29345 -catch-unload [ -t ] [ -d ] @var{regexp}
29348 Add a catchpoint for library unload events. If the @samp{-t} option is
29349 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29350 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29351 created in a disabled state. The @samp{regexp} argument is a regular
29352 expression used to match the name of the unloaded library.
29354 @subsubheading @value{GDBN} Command
29356 The corresponding @value{GDBN} command is @samp{catch unload}.
29358 @subsubheading Example
29361 -catch-unload -d bar.so
29362 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29363 what="load of library matching bar.so",catch-type="unload",times="0"@}
29367 @node Ada Exception GDB/MI Catchpoint Commands
29368 @subsection Ada Exception @sc{gdb/mi} Catchpoints
29370 The following @sc{gdb/mi} commands can be used to create catchpoints
29371 that stop the execution when Ada exceptions are being raised.
29373 @subheading The @code{-catch-assert} Command
29374 @findex -catch-assert
29376 @subsubheading Synopsis
29379 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
29382 Add a catchpoint for failed Ada assertions.
29384 The possible optional parameters for this command are:
29387 @item -c @var{condition}
29388 Make the catchpoint conditional on @var{condition}.
29390 Create a disabled catchpoint.
29392 Create a temporary catchpoint.
29395 @subsubheading @value{GDBN} Command
29397 The corresponding @value{GDBN} command is @samp{catch assert}.
29399 @subsubheading Example
29403 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
29404 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
29405 thread-groups=["i1"],times="0",
29406 original-location="__gnat_debug_raise_assert_failure"@}
29410 @subheading The @code{-catch-exception} Command
29411 @findex -catch-exception
29413 @subsubheading Synopsis
29416 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
29420 Add a catchpoint stopping when Ada exceptions are raised.
29421 By default, the command stops the program when any Ada exception
29422 gets raised. But it is also possible, by using some of the
29423 optional parameters described below, to create more selective
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.
29433 @item -e @var{exception-name}
29434 Only stop when @var{exception-name} is raised. This option cannot
29435 be used combined with @samp{-u}.
29437 Create a temporary catchpoint.
29439 Stop only when an unhandled exception gets raised. This option
29440 cannot be used combined with @samp{-e}.
29443 @subsubheading @value{GDBN} Command
29445 The corresponding @value{GDBN} commands are @samp{catch exception}
29446 and @samp{catch exception unhandled}.
29448 @subsubheading Example
29451 -catch-exception -e Program_Error
29452 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
29453 enabled="y",addr="0x0000000000404874",
29454 what="`Program_Error' Ada exception", thread-groups=["i1"],
29455 times="0",original-location="__gnat_debug_raise_exception"@}
29459 @subheading The @code{-catch-handlers} Command
29460 @findex -catch-handlers
29462 @subsubheading Synopsis
29465 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
29469 Add a catchpoint stopping when Ada exceptions are handled.
29470 By default, the command stops the program when any Ada exception
29471 gets handled. But it is also possible, by using some of the
29472 optional parameters described below, to create more selective
29475 The possible optional parameters for this command are:
29478 @item -c @var{condition}
29479 Make the catchpoint conditional on @var{condition}.
29481 Create a disabled catchpoint.
29482 @item -e @var{exception-name}
29483 Only stop when @var{exception-name} is handled.
29485 Create a temporary catchpoint.
29488 @subsubheading @value{GDBN} Command
29490 The corresponding @value{GDBN} command is @samp{catch handlers}.
29492 @subsubheading Example
29495 -catch-handlers -e Constraint_Error
29496 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
29497 enabled="y",addr="0x0000000000402f68",
29498 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
29499 times="0",original-location="__gnat_begin_handler"@}
29503 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29504 @node GDB/MI Program Context
29505 @section @sc{gdb/mi} Program Context
29507 @subheading The @code{-exec-arguments} Command
29508 @findex -exec-arguments
29511 @subsubheading Synopsis
29514 -exec-arguments @var{args}
29517 Set the inferior program arguments, to be used in the next
29520 @subsubheading @value{GDBN} Command
29522 The corresponding @value{GDBN} command is @samp{set args}.
29524 @subsubheading Example
29528 -exec-arguments -v word
29535 @subheading The @code{-exec-show-arguments} Command
29536 @findex -exec-show-arguments
29538 @subsubheading Synopsis
29541 -exec-show-arguments
29544 Print the arguments of the program.
29546 @subsubheading @value{GDBN} Command
29548 The corresponding @value{GDBN} command is @samp{show args}.
29550 @subsubheading Example
29555 @subheading The @code{-environment-cd} Command
29556 @findex -environment-cd
29558 @subsubheading Synopsis
29561 -environment-cd @var{pathdir}
29564 Set @value{GDBN}'s working directory.
29566 @subsubheading @value{GDBN} Command
29568 The corresponding @value{GDBN} command is @samp{cd}.
29570 @subsubheading Example
29574 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29580 @subheading The @code{-environment-directory} Command
29581 @findex -environment-directory
29583 @subsubheading Synopsis
29586 -environment-directory [ -r ] [ @var{pathdir} ]+
29589 Add directories @var{pathdir} to beginning of search path for source files.
29590 If the @samp{-r} option is used, the search path is reset to the default
29591 search path. If directories @var{pathdir} are supplied in addition to the
29592 @samp{-r} option, the search path is first reset and then addition
29594 Multiple directories may be specified, separated by blanks. Specifying
29595 multiple directories in a single command
29596 results in the directories added to the beginning of the
29597 search path in the same order they were presented in the command.
29598 If blanks are needed as
29599 part of a directory name, double-quotes should be used around
29600 the name. In the command output, the path will show up separated
29601 by the system directory-separator character. The directory-separator
29602 character must not be used
29603 in any directory name.
29604 If no directories are specified, the current search path is displayed.
29606 @subsubheading @value{GDBN} Command
29608 The corresponding @value{GDBN} command is @samp{dir}.
29610 @subsubheading Example
29614 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29615 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29617 -environment-directory ""
29618 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29620 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29621 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29623 -environment-directory -r
29624 ^done,source-path="$cdir:$cwd"
29629 @subheading The @code{-environment-path} Command
29630 @findex -environment-path
29632 @subsubheading Synopsis
29635 -environment-path [ -r ] [ @var{pathdir} ]+
29638 Add directories @var{pathdir} to beginning of search path for object files.
29639 If the @samp{-r} option is used, the search path is reset to the original
29640 search path that existed at gdb start-up. If directories @var{pathdir} are
29641 supplied in addition to the
29642 @samp{-r} option, the search path is first reset and then addition
29644 Multiple directories may be specified, separated by blanks. Specifying
29645 multiple directories in a single command
29646 results in the directories added to the beginning of the
29647 search path in the same order they were presented in the command.
29648 If blanks are needed as
29649 part of a directory name, double-quotes should be used around
29650 the name. In the command output, the path will show up separated
29651 by the system directory-separator character. The directory-separator
29652 character must not be used
29653 in any directory name.
29654 If no directories are specified, the current path is displayed.
29657 @subsubheading @value{GDBN} Command
29659 The corresponding @value{GDBN} command is @samp{path}.
29661 @subsubheading Example
29666 ^done,path="/usr/bin"
29668 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29669 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29671 -environment-path -r /usr/local/bin
29672 ^done,path="/usr/local/bin:/usr/bin"
29677 @subheading The @code{-environment-pwd} Command
29678 @findex -environment-pwd
29680 @subsubheading Synopsis
29686 Show the current working directory.
29688 @subsubheading @value{GDBN} Command
29690 The corresponding @value{GDBN} command is @samp{pwd}.
29692 @subsubheading Example
29697 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29701 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29702 @node GDB/MI Thread Commands
29703 @section @sc{gdb/mi} Thread Commands
29706 @subheading The @code{-thread-info} Command
29707 @findex -thread-info
29709 @subsubheading Synopsis
29712 -thread-info [ @var{thread-id} ]
29715 Reports information about either a specific thread, if the
29716 @var{thread-id} parameter is present, or about all threads.
29717 @var{thread-id} is the thread's global thread ID. When printing
29718 information about all threads, also reports the global ID of the
29721 @subsubheading @value{GDBN} Command
29723 The @samp{info thread} command prints the same information
29726 @subsubheading Result
29728 The result contains the following attributes:
29732 A list of threads. The format of the elements of the list is described in
29733 @ref{GDB/MI Thread Information}.
29735 @item current-thread-id
29736 The global id of the currently selected thread. This field is omitted if there
29737 is no selected thread (for example, when the selected inferior is not running,
29738 and therefore has no threads) or if a @var{thread-id} argument was passed to
29743 @subsubheading Example
29748 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29749 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29750 args=[]@},state="running"@},
29751 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29752 frame=@{level="0",addr="0x0804891f",func="foo",
29753 args=[@{name="i",value="10"@}],
29754 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
29755 state="running"@}],
29756 current-thread-id="1"
29760 @subheading The @code{-thread-list-ids} Command
29761 @findex -thread-list-ids
29763 @subsubheading Synopsis
29769 Produces a list of the currently known global @value{GDBN} thread ids.
29770 At the end of the list it also prints the total number of such
29773 This command is retained for historical reasons, the
29774 @code{-thread-info} command should be used instead.
29776 @subsubheading @value{GDBN} Command
29778 Part of @samp{info threads} supplies the same information.
29780 @subsubheading Example
29785 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29786 current-thread-id="1",number-of-threads="3"
29791 @subheading The @code{-thread-select} Command
29792 @findex -thread-select
29794 @subsubheading Synopsis
29797 -thread-select @var{thread-id}
29800 Make thread with global thread number @var{thread-id} the current
29801 thread. It prints the number of the new current thread, and the
29802 topmost frame for that thread.
29804 This command is deprecated in favor of explicitly using the
29805 @samp{--thread} option to each command.
29807 @subsubheading @value{GDBN} Command
29809 The corresponding @value{GDBN} command is @samp{thread}.
29811 @subsubheading Example
29818 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29819 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29823 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29824 number-of-threads="3"
29827 ^done,new-thread-id="3",
29828 frame=@{level="0",func="vprintf",
29829 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29830 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
29834 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29835 @node GDB/MI Ada Tasking Commands
29836 @section @sc{gdb/mi} Ada Tasking Commands
29838 @subheading The @code{-ada-task-info} Command
29839 @findex -ada-task-info
29841 @subsubheading Synopsis
29844 -ada-task-info [ @var{task-id} ]
29847 Reports information about either a specific Ada task, if the
29848 @var{task-id} parameter is present, or about all Ada tasks.
29850 @subsubheading @value{GDBN} Command
29852 The @samp{info tasks} command prints the same information
29853 about all Ada tasks (@pxref{Ada Tasks}).
29855 @subsubheading Result
29857 The result is a table of Ada tasks. The following columns are
29858 defined for each Ada task:
29862 This field exists only for the current thread. It has the value @samp{*}.
29865 The identifier that @value{GDBN} uses to refer to the Ada task.
29868 The identifier that the target uses to refer to the Ada task.
29871 The global thread identifier of the thread corresponding to the Ada
29874 This field should always exist, as Ada tasks are always implemented
29875 on top of a thread. But if @value{GDBN} cannot find this corresponding
29876 thread for any reason, the field is omitted.
29879 This field exists only when the task was created by another task.
29880 In this case, it provides the ID of the parent task.
29883 The base priority of the task.
29886 The current state of the task. For a detailed description of the
29887 possible states, see @ref{Ada Tasks}.
29890 The name of the task.
29894 @subsubheading Example
29898 ^done,tasks=@{nr_rows="3",nr_cols="8",
29899 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29900 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29901 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29902 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29903 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29904 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29905 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29906 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29907 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29908 state="Child Termination Wait",name="main_task"@}]@}
29912 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29913 @node GDB/MI Program Execution
29914 @section @sc{gdb/mi} Program Execution
29916 These are the asynchronous commands which generate the out-of-band
29917 record @samp{*stopped}. Currently @value{GDBN} only really executes
29918 asynchronously with remote targets and this interaction is mimicked in
29921 @subheading The @code{-exec-continue} Command
29922 @findex -exec-continue
29924 @subsubheading Synopsis
29927 -exec-continue [--reverse] [--all|--thread-group N]
29930 Resumes the execution of the inferior program, which will continue
29931 to execute until it reaches a debugger stop event. If the
29932 @samp{--reverse} option is specified, execution resumes in reverse until
29933 it reaches a stop event. Stop events may include
29936 breakpoints or watchpoints
29938 signals or exceptions
29940 the end of the process (or its beginning under @samp{--reverse})
29942 the end or beginning of a replay log if one is being used.
29944 In all-stop mode (@pxref{All-Stop
29945 Mode}), may resume only one thread, or all threads, depending on the
29946 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29947 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29948 ignored in all-stop mode. If the @samp{--thread-group} options is
29949 specified, then all threads in that thread group are resumed.
29951 @subsubheading @value{GDBN} Command
29953 The corresponding @value{GDBN} corresponding is @samp{continue}.
29955 @subsubheading Example
29962 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29963 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29964 line="13",arch="i386:x86_64"@}
29969 @subheading The @code{-exec-finish} Command
29970 @findex -exec-finish
29972 @subsubheading Synopsis
29975 -exec-finish [--reverse]
29978 Resumes the execution of the inferior program until the current
29979 function is exited. Displays the results returned by the function.
29980 If the @samp{--reverse} option is specified, resumes the reverse
29981 execution of the inferior program until the point where current
29982 function was called.
29984 @subsubheading @value{GDBN} Command
29986 The corresponding @value{GDBN} command is @samp{finish}.
29988 @subsubheading Example
29990 Function returning @code{void}.
29997 *stopped,reason="function-finished",frame=@{func="main",args=[],
29998 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
30002 Function returning other than @code{void}. The name of the internal
30003 @value{GDBN} variable storing the result is printed, together with the
30010 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
30011 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
30012 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30013 arch="i386:x86_64"@},
30014 gdb-result-var="$1",return-value="0"
30019 @subheading The @code{-exec-interrupt} Command
30020 @findex -exec-interrupt
30022 @subsubheading Synopsis
30025 -exec-interrupt [--all|--thread-group N]
30028 Interrupts the background execution of the target. Note how the token
30029 associated with the stop message is the one for the execution command
30030 that has been interrupted. The token for the interrupt itself only
30031 appears in the @samp{^done} output. If the user is trying to
30032 interrupt a non-running program, an error message will be printed.
30034 Note that when asynchronous execution is enabled, this command is
30035 asynchronous just like other execution commands. That is, first the
30036 @samp{^done} response will be printed, and the target stop will be
30037 reported after that using the @samp{*stopped} notification.
30039 In non-stop mode, only the context thread is interrupted by default.
30040 All threads (in all inferiors) will be interrupted if the
30041 @samp{--all} option is specified. If the @samp{--thread-group}
30042 option is specified, all threads in that group will be interrupted.
30044 @subsubheading @value{GDBN} Command
30046 The corresponding @value{GDBN} command is @samp{interrupt}.
30048 @subsubheading Example
30059 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
30060 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
30061 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
30066 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
30070 @subheading The @code{-exec-jump} Command
30073 @subsubheading Synopsis
30076 -exec-jump @var{location}
30079 Resumes execution of the inferior program at the location specified by
30080 parameter. @xref{Specify Location}, for a description of the
30081 different forms of @var{location}.
30083 @subsubheading @value{GDBN} Command
30085 The corresponding @value{GDBN} command is @samp{jump}.
30087 @subsubheading Example
30090 -exec-jump foo.c:10
30091 *running,thread-id="all"
30096 @subheading The @code{-exec-next} Command
30099 @subsubheading Synopsis
30102 -exec-next [--reverse]
30105 Resumes execution of the inferior program, stopping when the beginning
30106 of the next source line is reached.
30108 If the @samp{--reverse} option is specified, resumes reverse execution
30109 of the inferior program, stopping at the beginning of the previous
30110 source line. If you issue this command on the first line of a
30111 function, it will take you back to the caller of that function, to the
30112 source line where the function was called.
30115 @subsubheading @value{GDBN} Command
30117 The corresponding @value{GDBN} command is @samp{next}.
30119 @subsubheading Example
30125 *stopped,reason="end-stepping-range",line="8",file="hello.c"
30130 @subheading The @code{-exec-next-instruction} Command
30131 @findex -exec-next-instruction
30133 @subsubheading Synopsis
30136 -exec-next-instruction [--reverse]
30139 Executes one machine instruction. If the instruction is a function
30140 call, continues until the function returns. If the program stops at an
30141 instruction in the middle of a source line, the address will be
30144 If the @samp{--reverse} option is specified, resumes reverse execution
30145 of the inferior program, stopping at the previous instruction. If the
30146 previously executed instruction was a return from another function,
30147 it will continue to execute in reverse until the call to that function
30148 (from the current stack frame) is reached.
30150 @subsubheading @value{GDBN} Command
30152 The corresponding @value{GDBN} command is @samp{nexti}.
30154 @subsubheading Example
30158 -exec-next-instruction
30162 *stopped,reason="end-stepping-range",
30163 addr="0x000100d4",line="5",file="hello.c"
30168 @subheading The @code{-exec-return} Command
30169 @findex -exec-return
30171 @subsubheading Synopsis
30177 Makes current function return immediately. Doesn't execute the inferior.
30178 Displays the new current frame.
30180 @subsubheading @value{GDBN} Command
30182 The corresponding @value{GDBN} command is @samp{return}.
30184 @subsubheading Example
30188 200-break-insert callee4
30189 200^done,bkpt=@{number="1",addr="0x00010734",
30190 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
30195 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30196 frame=@{func="callee4",args=[],
30197 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30198 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30199 arch="i386:x86_64"@}
30205 111^done,frame=@{level="0",func="callee3",
30206 args=[@{name="strarg",
30207 value="0x11940 \"A string argument.\""@}],
30208 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30209 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
30210 arch="i386:x86_64"@}
30215 @subheading The @code{-exec-run} Command
30218 @subsubheading Synopsis
30221 -exec-run [ --all | --thread-group N ] [ --start ]
30224 Starts execution of the inferior from the beginning. The inferior
30225 executes until either a breakpoint is encountered or the program
30226 exits. In the latter case the output will include an exit code, if
30227 the program has exited exceptionally.
30229 When neither the @samp{--all} nor the @samp{--thread-group} option
30230 is specified, the current inferior is started. If the
30231 @samp{--thread-group} option is specified, it should refer to a thread
30232 group of type @samp{process}, and that thread group will be started.
30233 If the @samp{--all} option is specified, then all inferiors will be started.
30235 Using the @samp{--start} option instructs the debugger to stop
30236 the execution at the start of the inferior's main subprogram,
30237 following the same behavior as the @code{start} command
30238 (@pxref{Starting}).
30240 @subsubheading @value{GDBN} Command
30242 The corresponding @value{GDBN} command is @samp{run}.
30244 @subsubheading Examples
30249 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
30254 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30255 frame=@{func="main",args=[],file="recursive2.c",
30256 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
30261 Program exited normally:
30269 *stopped,reason="exited-normally"
30274 Program exited exceptionally:
30282 *stopped,reason="exited",exit-code="01"
30286 Another way the program can terminate is if it receives a signal such as
30287 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
30291 *stopped,reason="exited-signalled",signal-name="SIGINT",
30292 signal-meaning="Interrupt"
30296 @c @subheading -exec-signal
30299 @subheading The @code{-exec-step} Command
30302 @subsubheading Synopsis
30305 -exec-step [--reverse]
30308 Resumes execution of the inferior program, stopping when the beginning
30309 of the next source line is reached, if the next source line is not a
30310 function call. If it is, stop at the first instruction of the called
30311 function. If the @samp{--reverse} option is specified, resumes reverse
30312 execution of the inferior program, stopping at the beginning of the
30313 previously executed source line.
30315 @subsubheading @value{GDBN} Command
30317 The corresponding @value{GDBN} command is @samp{step}.
30319 @subsubheading Example
30321 Stepping into a function:
30327 *stopped,reason="end-stepping-range",
30328 frame=@{func="foo",args=[@{name="a",value="10"@},
30329 @{name="b",value="0"@}],file="recursive2.c",
30330 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
30340 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
30345 @subheading The @code{-exec-step-instruction} Command
30346 @findex -exec-step-instruction
30348 @subsubheading Synopsis
30351 -exec-step-instruction [--reverse]
30354 Resumes the inferior which executes one machine instruction. If the
30355 @samp{--reverse} option is specified, resumes reverse execution of the
30356 inferior program, stopping at the previously executed instruction.
30357 The output, once @value{GDBN} has stopped, will vary depending on
30358 whether we have stopped in the middle of a source line or not. In the
30359 former case, the address at which the program stopped will be printed
30362 @subsubheading @value{GDBN} Command
30364 The corresponding @value{GDBN} command is @samp{stepi}.
30366 @subsubheading Example
30370 -exec-step-instruction
30374 *stopped,reason="end-stepping-range",
30375 frame=@{func="foo",args=[],file="try.c",
30376 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
30378 -exec-step-instruction
30382 *stopped,reason="end-stepping-range",
30383 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
30384 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
30389 @subheading The @code{-exec-until} Command
30390 @findex -exec-until
30392 @subsubheading Synopsis
30395 -exec-until [ @var{location} ]
30398 Executes the inferior until the @var{location} specified in the
30399 argument is reached. If there is no argument, the inferior executes
30400 until a source line greater than the current one is reached. The
30401 reason for stopping in this case will be @samp{location-reached}.
30403 @subsubheading @value{GDBN} Command
30405 The corresponding @value{GDBN} command is @samp{until}.
30407 @subsubheading Example
30411 -exec-until recursive2.c:6
30415 *stopped,reason="location-reached",frame=@{func="main",args=[],
30416 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
30417 arch="i386:x86_64"@}
30422 @subheading -file-clear
30423 Is this going away????
30426 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30427 @node GDB/MI Stack Manipulation
30428 @section @sc{gdb/mi} Stack Manipulation Commands
30430 @subheading The @code{-enable-frame-filters} Command
30431 @findex -enable-frame-filters
30434 -enable-frame-filters
30437 @value{GDBN} allows Python-based frame filters to affect the output of
30438 the MI commands relating to stack traces. As there is no way to
30439 implement this in a fully backward-compatible way, a front end must
30440 request that this functionality be enabled.
30442 Once enabled, this feature cannot be disabled.
30444 Note that if Python support has not been compiled into @value{GDBN},
30445 this command will still succeed (and do nothing).
30447 @subheading The @code{-stack-info-frame} Command
30448 @findex -stack-info-frame
30450 @subsubheading Synopsis
30456 Get info on the selected frame.
30458 @subsubheading @value{GDBN} Command
30460 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
30461 (without arguments).
30463 @subsubheading Example
30468 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
30469 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30470 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
30471 arch="i386:x86_64"@}
30475 @subheading The @code{-stack-info-depth} Command
30476 @findex -stack-info-depth
30478 @subsubheading Synopsis
30481 -stack-info-depth [ @var{max-depth} ]
30484 Return the depth of the stack. If the integer argument @var{max-depth}
30485 is specified, do not count beyond @var{max-depth} frames.
30487 @subsubheading @value{GDBN} Command
30489 There's no equivalent @value{GDBN} command.
30491 @subsubheading Example
30493 For a stack with frame levels 0 through 11:
30500 -stack-info-depth 4
30503 -stack-info-depth 12
30506 -stack-info-depth 11
30509 -stack-info-depth 13
30514 @anchor{-stack-list-arguments}
30515 @subheading The @code{-stack-list-arguments} Command
30516 @findex -stack-list-arguments
30518 @subsubheading Synopsis
30521 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30522 [ @var{low-frame} @var{high-frame} ]
30525 Display a list of the arguments for the frames between @var{low-frame}
30526 and @var{high-frame} (inclusive). If @var{low-frame} and
30527 @var{high-frame} are not provided, list the arguments for the whole
30528 call stack. If the two arguments are equal, show the single frame
30529 at the corresponding level. It is an error if @var{low-frame} is
30530 larger than the actual number of frames. On the other hand,
30531 @var{high-frame} may be larger than the actual number of frames, in
30532 which case only existing frames will be returned.
30534 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30535 the variables; if it is 1 or @code{--all-values}, print also their
30536 values; and if it is 2 or @code{--simple-values}, print the name,
30537 type and value for simple data types, and the name and type for arrays,
30538 structures and unions. If the option @code{--no-frame-filters} is
30539 supplied, then Python frame filters will not be executed.
30541 If the @code{--skip-unavailable} option is specified, arguments that
30542 are not available are not listed. Partially available arguments
30543 are still displayed, however.
30545 Use of this command to obtain arguments in a single frame is
30546 deprecated in favor of the @samp{-stack-list-variables} command.
30548 @subsubheading @value{GDBN} Command
30550 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30551 @samp{gdb_get_args} command which partially overlaps with the
30552 functionality of @samp{-stack-list-arguments}.
30554 @subsubheading Example
30561 frame=@{level="0",addr="0x00010734",func="callee4",
30562 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30563 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30564 arch="i386:x86_64"@},
30565 frame=@{level="1",addr="0x0001076c",func="callee3",
30566 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30567 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
30568 arch="i386:x86_64"@},
30569 frame=@{level="2",addr="0x0001078c",func="callee2",
30570 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30571 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
30572 arch="i386:x86_64"@},
30573 frame=@{level="3",addr="0x000107b4",func="callee1",
30574 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30575 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
30576 arch="i386:x86_64"@},
30577 frame=@{level="4",addr="0x000107e0",func="main",
30578 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30579 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
30580 arch="i386:x86_64"@}]
30582 -stack-list-arguments 0
30585 frame=@{level="0",args=[]@},
30586 frame=@{level="1",args=[name="strarg"]@},
30587 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30588 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30589 frame=@{level="4",args=[]@}]
30591 -stack-list-arguments 1
30594 frame=@{level="0",args=[]@},
30596 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30597 frame=@{level="2",args=[
30598 @{name="intarg",value="2"@},
30599 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30600 @{frame=@{level="3",args=[
30601 @{name="intarg",value="2"@},
30602 @{name="strarg",value="0x11940 \"A string argument.\""@},
30603 @{name="fltarg",value="3.5"@}]@},
30604 frame=@{level="4",args=[]@}]
30606 -stack-list-arguments 0 2 2
30607 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30609 -stack-list-arguments 1 2 2
30610 ^done,stack-args=[frame=@{level="2",
30611 args=[@{name="intarg",value="2"@},
30612 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30616 @c @subheading -stack-list-exception-handlers
30619 @anchor{-stack-list-frames}
30620 @subheading The @code{-stack-list-frames} Command
30621 @findex -stack-list-frames
30623 @subsubheading Synopsis
30626 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
30629 List the frames currently on the stack. For each frame it displays the
30634 The frame number, 0 being the topmost frame, i.e., the innermost function.
30636 The @code{$pc} value for that frame.
30640 File name of the source file where the function lives.
30641 @item @var{fullname}
30642 The full file name of the source file where the function lives.
30644 Line number corresponding to the @code{$pc}.
30646 The shared library where this function is defined. This is only given
30647 if the frame's function is not known.
30649 Frame's architecture.
30652 If invoked without arguments, this command prints a backtrace for the
30653 whole stack. If given two integer arguments, it shows the frames whose
30654 levels are between the two arguments (inclusive). If the two arguments
30655 are equal, it shows the single frame at the corresponding level. It is
30656 an error if @var{low-frame} is larger than the actual number of
30657 frames. On the other hand, @var{high-frame} may be larger than the
30658 actual number of frames, in which case only existing frames will be
30659 returned. If the option @code{--no-frame-filters} is supplied, then
30660 Python frame filters will not be executed.
30662 @subsubheading @value{GDBN} Command
30664 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30666 @subsubheading Example
30668 Full stack backtrace:
30674 [frame=@{level="0",addr="0x0001076c",func="foo",
30675 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
30676 arch="i386:x86_64"@},
30677 frame=@{level="1",addr="0x000107a4",func="foo",
30678 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30679 arch="i386:x86_64"@},
30680 frame=@{level="2",addr="0x000107a4",func="foo",
30681 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30682 arch="i386:x86_64"@},
30683 frame=@{level="3",addr="0x000107a4",func="foo",
30684 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30685 arch="i386:x86_64"@},
30686 frame=@{level="4",addr="0x000107a4",func="foo",
30687 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30688 arch="i386:x86_64"@},
30689 frame=@{level="5",addr="0x000107a4",func="foo",
30690 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30691 arch="i386:x86_64"@},
30692 frame=@{level="6",addr="0x000107a4",func="foo",
30693 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30694 arch="i386:x86_64"@},
30695 frame=@{level="7",addr="0x000107a4",func="foo",
30696 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30697 arch="i386:x86_64"@},
30698 frame=@{level="8",addr="0x000107a4",func="foo",
30699 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30700 arch="i386:x86_64"@},
30701 frame=@{level="9",addr="0x000107a4",func="foo",
30702 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30703 arch="i386:x86_64"@},
30704 frame=@{level="10",addr="0x000107a4",func="foo",
30705 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30706 arch="i386:x86_64"@},
30707 frame=@{level="11",addr="0x00010738",func="main",
30708 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
30709 arch="i386:x86_64"@}]
30713 Show frames between @var{low_frame} and @var{high_frame}:
30717 -stack-list-frames 3 5
30719 [frame=@{level="3",addr="0x000107a4",func="foo",
30720 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30721 arch="i386:x86_64"@},
30722 frame=@{level="4",addr="0x000107a4",func="foo",
30723 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30724 arch="i386:x86_64"@},
30725 frame=@{level="5",addr="0x000107a4",func="foo",
30726 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30727 arch="i386:x86_64"@}]
30731 Show a single frame:
30735 -stack-list-frames 3 3
30737 [frame=@{level="3",addr="0x000107a4",func="foo",
30738 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30739 arch="i386:x86_64"@}]
30744 @subheading The @code{-stack-list-locals} Command
30745 @findex -stack-list-locals
30746 @anchor{-stack-list-locals}
30748 @subsubheading Synopsis
30751 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30754 Display the local variable names for the selected frame. If
30755 @var{print-values} is 0 or @code{--no-values}, print only the names of
30756 the variables; if it is 1 or @code{--all-values}, print also their
30757 values; and if it is 2 or @code{--simple-values}, print the name,
30758 type and value for simple data types, and the name and type for arrays,
30759 structures and unions. In this last case, a frontend can immediately
30760 display the value of simple data types and create variable objects for
30761 other data types when the user wishes to explore their values in
30762 more detail. If the option @code{--no-frame-filters} is supplied, then
30763 Python frame filters will not be executed.
30765 If the @code{--skip-unavailable} option is specified, local variables
30766 that are not available are not listed. Partially available local
30767 variables are still displayed, however.
30769 This command is deprecated in favor of the
30770 @samp{-stack-list-variables} command.
30772 @subsubheading @value{GDBN} Command
30774 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30776 @subsubheading Example
30780 -stack-list-locals 0
30781 ^done,locals=[name="A",name="B",name="C"]
30783 -stack-list-locals --all-values
30784 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30785 @{name="C",value="@{1, 2, 3@}"@}]
30786 -stack-list-locals --simple-values
30787 ^done,locals=[@{name="A",type="int",value="1"@},
30788 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30792 @anchor{-stack-list-variables}
30793 @subheading The @code{-stack-list-variables} Command
30794 @findex -stack-list-variables
30796 @subsubheading Synopsis
30799 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30802 Display the names of local variables and function arguments for the selected frame. If
30803 @var{print-values} is 0 or @code{--no-values}, print only the names of
30804 the variables; if it is 1 or @code{--all-values}, print also their
30805 values; and if it is 2 or @code{--simple-values}, print the name,
30806 type and value for simple data types, and the name and type for arrays,
30807 structures and unions. If the option @code{--no-frame-filters} is
30808 supplied, then Python frame filters will not be executed.
30810 If the @code{--skip-unavailable} option is specified, local variables
30811 and arguments that are not available are not listed. Partially
30812 available arguments and local variables are still displayed, however.
30814 @subsubheading Example
30818 -stack-list-variables --thread 1 --frame 0 --all-values
30819 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30824 @subheading The @code{-stack-select-frame} Command
30825 @findex -stack-select-frame
30827 @subsubheading Synopsis
30830 -stack-select-frame @var{framenum}
30833 Change the selected frame. Select a different frame @var{framenum} on
30836 This command in deprecated in favor of passing the @samp{--frame}
30837 option to every command.
30839 @subsubheading @value{GDBN} Command
30841 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30842 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30844 @subsubheading Example
30848 -stack-select-frame 2
30853 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30854 @node GDB/MI Variable Objects
30855 @section @sc{gdb/mi} Variable Objects
30859 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30861 For the implementation of a variable debugger window (locals, watched
30862 expressions, etc.), we are proposing the adaptation of the existing code
30863 used by @code{Insight}.
30865 The two main reasons for that are:
30869 It has been proven in practice (it is already on its second generation).
30872 It will shorten development time (needless to say how important it is
30876 The original interface was designed to be used by Tcl code, so it was
30877 slightly changed so it could be used through @sc{gdb/mi}. This section
30878 describes the @sc{gdb/mi} operations that will be available and gives some
30879 hints about their use.
30881 @emph{Note}: In addition to the set of operations described here, we
30882 expect the @sc{gui} implementation of a variable window to require, at
30883 least, the following operations:
30886 @item @code{-gdb-show} @code{output-radix}
30887 @item @code{-stack-list-arguments}
30888 @item @code{-stack-list-locals}
30889 @item @code{-stack-select-frame}
30894 @subheading Introduction to Variable Objects
30896 @cindex variable objects in @sc{gdb/mi}
30898 Variable objects are "object-oriented" MI interface for examining and
30899 changing values of expressions. Unlike some other MI interfaces that
30900 work with expressions, variable objects are specifically designed for
30901 simple and efficient presentation in the frontend. A variable object
30902 is identified by string name. When a variable object is created, the
30903 frontend specifies the expression for that variable object. The
30904 expression can be a simple variable, or it can be an arbitrary complex
30905 expression, and can even involve CPU registers. After creating a
30906 variable object, the frontend can invoke other variable object
30907 operations---for example to obtain or change the value of a variable
30908 object, or to change display format.
30910 Variable objects have hierarchical tree structure. Any variable object
30911 that corresponds to a composite type, such as structure in C, has
30912 a number of child variable objects, for example corresponding to each
30913 element of a structure. A child variable object can itself have
30914 children, recursively. Recursion ends when we reach
30915 leaf variable objects, which always have built-in types. Child variable
30916 objects are created only by explicit request, so if a frontend
30917 is not interested in the children of a particular variable object, no
30918 child will be created.
30920 For a leaf variable object it is possible to obtain its value as a
30921 string, or set the value from a string. String value can be also
30922 obtained for a non-leaf variable object, but it's generally a string
30923 that only indicates the type of the object, and does not list its
30924 contents. Assignment to a non-leaf variable object is not allowed.
30926 A frontend does not need to read the values of all variable objects each time
30927 the program stops. Instead, MI provides an update command that lists all
30928 variable objects whose values has changed since the last update
30929 operation. This considerably reduces the amount of data that must
30930 be transferred to the frontend. As noted above, children variable
30931 objects are created on demand, and only leaf variable objects have a
30932 real value. As result, gdb will read target memory only for leaf
30933 variables that frontend has created.
30935 The automatic update is not always desirable. For example, a frontend
30936 might want to keep a value of some expression for future reference,
30937 and never update it. For another example, fetching memory is
30938 relatively slow for embedded targets, so a frontend might want
30939 to disable automatic update for the variables that are either not
30940 visible on the screen, or ``closed''. This is possible using so
30941 called ``frozen variable objects''. Such variable objects are never
30942 implicitly updated.
30944 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30945 fixed variable object, the expression is parsed when the variable
30946 object is created, including associating identifiers to specific
30947 variables. The meaning of expression never changes. For a floating
30948 variable object the values of variables whose names appear in the
30949 expressions are re-evaluated every time in the context of the current
30950 frame. Consider this example:
30955 struct work_state state;
30962 If a fixed variable object for the @code{state} variable is created in
30963 this function, and we enter the recursive call, the variable
30964 object will report the value of @code{state} in the top-level
30965 @code{do_work} invocation. On the other hand, a floating variable
30966 object will report the value of @code{state} in the current frame.
30968 If an expression specified when creating a fixed variable object
30969 refers to a local variable, the variable object becomes bound to the
30970 thread and frame in which the variable object is created. When such
30971 variable object is updated, @value{GDBN} makes sure that the
30972 thread/frame combination the variable object is bound to still exists,
30973 and re-evaluates the variable object in context of that thread/frame.
30975 The following is the complete set of @sc{gdb/mi} operations defined to
30976 access this functionality:
30978 @multitable @columnfractions .4 .6
30979 @item @strong{Operation}
30980 @tab @strong{Description}
30982 @item @code{-enable-pretty-printing}
30983 @tab enable Python-based pretty-printing
30984 @item @code{-var-create}
30985 @tab create a variable object
30986 @item @code{-var-delete}
30987 @tab delete the variable object and/or its children
30988 @item @code{-var-set-format}
30989 @tab set the display format of this variable
30990 @item @code{-var-show-format}
30991 @tab show the display format of this variable
30992 @item @code{-var-info-num-children}
30993 @tab tells how many children this object has
30994 @item @code{-var-list-children}
30995 @tab return a list of the object's children
30996 @item @code{-var-info-type}
30997 @tab show the type of this variable object
30998 @item @code{-var-info-expression}
30999 @tab print parent-relative expression that this variable object represents
31000 @item @code{-var-info-path-expression}
31001 @tab print full expression that this variable object represents
31002 @item @code{-var-show-attributes}
31003 @tab is this variable editable? does it exist here?
31004 @item @code{-var-evaluate-expression}
31005 @tab get the value of this variable
31006 @item @code{-var-assign}
31007 @tab set the value of this variable
31008 @item @code{-var-update}
31009 @tab update the variable and its children
31010 @item @code{-var-set-frozen}
31011 @tab set frozeness attribute
31012 @item @code{-var-set-update-range}
31013 @tab set range of children to display on update
31016 In the next subsection we describe each operation in detail and suggest
31017 how it can be used.
31019 @subheading Description And Use of Operations on Variable Objects
31021 @subheading The @code{-enable-pretty-printing} Command
31022 @findex -enable-pretty-printing
31025 -enable-pretty-printing
31028 @value{GDBN} allows Python-based visualizers to affect the output of the
31029 MI variable object commands. However, because there was no way to
31030 implement this in a fully backward-compatible way, a front end must
31031 request that this functionality be enabled.
31033 Once enabled, this feature cannot be disabled.
31035 Note that if Python support has not been compiled into @value{GDBN},
31036 this command will still succeed (and do nothing).
31038 This feature is currently (as of @value{GDBN} 7.0) experimental, and
31039 may work differently in future versions of @value{GDBN}.
31041 @subheading The @code{-var-create} Command
31042 @findex -var-create
31044 @subsubheading Synopsis
31047 -var-create @{@var{name} | "-"@}
31048 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
31051 This operation creates a variable object, which allows the monitoring of
31052 a variable, the result of an expression, a memory cell or a CPU
31055 The @var{name} parameter is the string by which the object can be
31056 referenced. It must be unique. If @samp{-} is specified, the varobj
31057 system will generate a string ``varNNNNNN'' automatically. It will be
31058 unique provided that one does not specify @var{name} of that format.
31059 The command fails if a duplicate name is found.
31061 The frame under which the expression should be evaluated can be
31062 specified by @var{frame-addr}. A @samp{*} indicates that the current
31063 frame should be used. A @samp{@@} indicates that a floating variable
31064 object must be created.
31066 @var{expression} is any expression valid on the current language set (must not
31067 begin with a @samp{*}), or one of the following:
31071 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
31074 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
31077 @samp{$@var{regname}} --- a CPU register name
31080 @cindex dynamic varobj
31081 A varobj's contents may be provided by a Python-based pretty-printer. In this
31082 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
31083 have slightly different semantics in some cases. If the
31084 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
31085 will never create a dynamic varobj. This ensures backward
31086 compatibility for existing clients.
31088 @subsubheading Result
31090 This operation returns attributes of the newly-created varobj. These
31095 The name of the varobj.
31098 The number of children of the varobj. This number is not necessarily
31099 reliable for a dynamic varobj. Instead, you must examine the
31100 @samp{has_more} attribute.
31103 The varobj's scalar value. For a varobj whose type is some sort of
31104 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
31105 will not be interesting.
31108 The varobj's type. This is a string representation of the type, as
31109 would be printed by the @value{GDBN} CLI. If @samp{print object}
31110 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31111 @emph{actual} (derived) type of the object is shown rather than the
31112 @emph{declared} one.
31115 If a variable object is bound to a specific thread, then this is the
31116 thread's global identifier.
31119 For a dynamic varobj, this indicates whether there appear to be any
31120 children available. For a non-dynamic varobj, this will be 0.
31123 This attribute will be present and have the value @samp{1} if the
31124 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31125 then this attribute will not be present.
31128 A dynamic varobj can supply a display hint to the front end. The
31129 value comes directly from the Python pretty-printer object's
31130 @code{display_hint} method. @xref{Pretty Printing API}.
31133 Typical output will look like this:
31136 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
31137 has_more="@var{has_more}"
31141 @subheading The @code{-var-delete} Command
31142 @findex -var-delete
31144 @subsubheading Synopsis
31147 -var-delete [ -c ] @var{name}
31150 Deletes a previously created variable object and all of its children.
31151 With the @samp{-c} option, just deletes the children.
31153 Returns an error if the object @var{name} is not found.
31156 @subheading The @code{-var-set-format} Command
31157 @findex -var-set-format
31159 @subsubheading Synopsis
31162 -var-set-format @var{name} @var{format-spec}
31165 Sets the output format for the value of the object @var{name} to be
31168 @anchor{-var-set-format}
31169 The syntax for the @var{format-spec} is as follows:
31172 @var{format-spec} @expansion{}
31173 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
31176 The natural format is the default format choosen automatically
31177 based on the variable type (like decimal for an @code{int}, hex
31178 for pointers, etc.).
31180 The zero-hexadecimal format has a representation similar to hexadecimal
31181 but with padding zeroes to the left of the value. For example, a 32-bit
31182 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
31183 zero-hexadecimal format.
31185 For a variable with children, the format is set only on the
31186 variable itself, and the children are not affected.
31188 @subheading The @code{-var-show-format} Command
31189 @findex -var-show-format
31191 @subsubheading Synopsis
31194 -var-show-format @var{name}
31197 Returns the format used to display the value of the object @var{name}.
31200 @var{format} @expansion{}
31205 @subheading The @code{-var-info-num-children} Command
31206 @findex -var-info-num-children
31208 @subsubheading Synopsis
31211 -var-info-num-children @var{name}
31214 Returns the number of children of a variable object @var{name}:
31220 Note that this number is not completely reliable for a dynamic varobj.
31221 It will return the current number of children, but more children may
31225 @subheading The @code{-var-list-children} Command
31226 @findex -var-list-children
31228 @subsubheading Synopsis
31231 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
31233 @anchor{-var-list-children}
31235 Return a list of the children of the specified variable object and
31236 create variable objects for them, if they do not already exist. With
31237 a single argument or if @var{print-values} has a value of 0 or
31238 @code{--no-values}, print only the names of the variables; if
31239 @var{print-values} is 1 or @code{--all-values}, also print their
31240 values; and if it is 2 or @code{--simple-values} print the name and
31241 value for simple data types and just the name for arrays, structures
31244 @var{from} and @var{to}, if specified, indicate the range of children
31245 to report. If @var{from} or @var{to} is less than zero, the range is
31246 reset and all children will be reported. Otherwise, children starting
31247 at @var{from} (zero-based) and up to and excluding @var{to} will be
31250 If a child range is requested, it will only affect the current call to
31251 @code{-var-list-children}, but not future calls to @code{-var-update}.
31252 For this, you must instead use @code{-var-set-update-range}. The
31253 intent of this approach is to enable a front end to implement any
31254 update approach it likes; for example, scrolling a view may cause the
31255 front end to request more children with @code{-var-list-children}, and
31256 then the front end could call @code{-var-set-update-range} with a
31257 different range to ensure that future updates are restricted to just
31260 For each child the following results are returned:
31265 Name of the variable object created for this child.
31268 The expression to be shown to the user by the front end to designate this child.
31269 For example this may be the name of a structure member.
31271 For a dynamic varobj, this value cannot be used to form an
31272 expression. There is no way to do this at all with a dynamic varobj.
31274 For C/C@t{++} structures there are several pseudo children returned to
31275 designate access qualifiers. For these pseudo children @var{exp} is
31276 @samp{public}, @samp{private}, or @samp{protected}. In this case the
31277 type and value are not present.
31279 A dynamic varobj will not report the access qualifying
31280 pseudo-children, regardless of the language. This information is not
31281 available at all with a dynamic varobj.
31284 Number of children this child has. For a dynamic varobj, this will be
31288 The type of the child. If @samp{print object}
31289 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31290 @emph{actual} (derived) type of the object is shown rather than the
31291 @emph{declared} one.
31294 If values were requested, this is the value.
31297 If this variable object is associated with a thread, this is the
31298 thread's global thread id. Otherwise this result is not present.
31301 If the variable object is frozen, this variable will be present with a value of 1.
31304 A dynamic varobj can supply a display hint to the front end. The
31305 value comes directly from the Python pretty-printer object's
31306 @code{display_hint} method. @xref{Pretty Printing API}.
31309 This attribute will be present and have the value @samp{1} if the
31310 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31311 then this attribute will not be present.
31315 The result may have its own attributes:
31319 A dynamic varobj can supply a display hint to the front end. The
31320 value comes directly from the Python pretty-printer object's
31321 @code{display_hint} method. @xref{Pretty Printing API}.
31324 This is an integer attribute which is nonzero if there are children
31325 remaining after the end of the selected range.
31328 @subsubheading Example
31332 -var-list-children n
31333 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
31334 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
31336 -var-list-children --all-values n
31337 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
31338 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
31342 @subheading The @code{-var-info-type} Command
31343 @findex -var-info-type
31345 @subsubheading Synopsis
31348 -var-info-type @var{name}
31351 Returns the type of the specified variable @var{name}. The type is
31352 returned as a string in the same format as it is output by the
31356 type=@var{typename}
31360 @subheading The @code{-var-info-expression} Command
31361 @findex -var-info-expression
31363 @subsubheading Synopsis
31366 -var-info-expression @var{name}
31369 Returns a string that is suitable for presenting this
31370 variable object in user interface. The string is generally
31371 not valid expression in the current language, and cannot be evaluated.
31373 For example, if @code{a} is an array, and variable object
31374 @code{A} was created for @code{a}, then we'll get this output:
31377 (gdb) -var-info-expression A.1
31378 ^done,lang="C",exp="1"
31382 Here, the value of @code{lang} is the language name, which can be
31383 found in @ref{Supported Languages}.
31385 Note that the output of the @code{-var-list-children} command also
31386 includes those expressions, so the @code{-var-info-expression} command
31389 @subheading The @code{-var-info-path-expression} Command
31390 @findex -var-info-path-expression
31392 @subsubheading Synopsis
31395 -var-info-path-expression @var{name}
31398 Returns an expression that can be evaluated in the current
31399 context and will yield the same value that a variable object has.
31400 Compare this with the @code{-var-info-expression} command, which
31401 result can be used only for UI presentation. Typical use of
31402 the @code{-var-info-path-expression} command is creating a
31403 watchpoint from a variable object.
31405 This command is currently not valid for children of a dynamic varobj,
31406 and will give an error when invoked on one.
31408 For example, suppose @code{C} is a C@t{++} class, derived from class
31409 @code{Base}, and that the @code{Base} class has a member called
31410 @code{m_size}. Assume a variable @code{c} is has the type of
31411 @code{C} and a variable object @code{C} was created for variable
31412 @code{c}. Then, we'll get this output:
31414 (gdb) -var-info-path-expression C.Base.public.m_size
31415 ^done,path_expr=((Base)c).m_size)
31418 @subheading The @code{-var-show-attributes} Command
31419 @findex -var-show-attributes
31421 @subsubheading Synopsis
31424 -var-show-attributes @var{name}
31427 List attributes of the specified variable object @var{name}:
31430 status=@var{attr} [ ( ,@var{attr} )* ]
31434 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
31436 @subheading The @code{-var-evaluate-expression} Command
31437 @findex -var-evaluate-expression
31439 @subsubheading Synopsis
31442 -var-evaluate-expression [-f @var{format-spec}] @var{name}
31445 Evaluates the expression that is represented by the specified variable
31446 object and returns its value as a string. The format of the string
31447 can be specified with the @samp{-f} option. The possible values of
31448 this option are the same as for @code{-var-set-format}
31449 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
31450 the current display format will be used. The current display format
31451 can be changed using the @code{-var-set-format} command.
31457 Note that one must invoke @code{-var-list-children} for a variable
31458 before the value of a child variable can be evaluated.
31460 @subheading The @code{-var-assign} Command
31461 @findex -var-assign
31463 @subsubheading Synopsis
31466 -var-assign @var{name} @var{expression}
31469 Assigns the value of @var{expression} to the variable object specified
31470 by @var{name}. The object must be @samp{editable}. If the variable's
31471 value is altered by the assign, the variable will show up in any
31472 subsequent @code{-var-update} list.
31474 @subsubheading Example
31482 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
31486 @subheading The @code{-var-update} Command
31487 @findex -var-update
31489 @subsubheading Synopsis
31492 -var-update [@var{print-values}] @{@var{name} | "*"@}
31495 Reevaluate the expressions corresponding to the variable object
31496 @var{name} and all its direct and indirect children, and return the
31497 list of variable objects whose values have changed; @var{name} must
31498 be a root variable object. Here, ``changed'' means that the result of
31499 @code{-var-evaluate-expression} before and after the
31500 @code{-var-update} is different. If @samp{*} is used as the variable
31501 object names, all existing variable objects are updated, except
31502 for frozen ones (@pxref{-var-set-frozen}). The option
31503 @var{print-values} determines whether both names and values, or just
31504 names are printed. The possible values of this option are the same
31505 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
31506 recommended to use the @samp{--all-values} option, to reduce the
31507 number of MI commands needed on each program stop.
31509 With the @samp{*} parameter, if a variable object is bound to a
31510 currently running thread, it will not be updated, without any
31513 If @code{-var-set-update-range} was previously used on a varobj, then
31514 only the selected range of children will be reported.
31516 @code{-var-update} reports all the changed varobjs in a tuple named
31519 Each item in the change list is itself a tuple holding:
31523 The name of the varobj.
31526 If values were requested for this update, then this field will be
31527 present and will hold the value of the varobj.
31530 @anchor{-var-update}
31531 This field is a string which may take one of three values:
31535 The variable object's current value is valid.
31538 The variable object does not currently hold a valid value but it may
31539 hold one in the future if its associated expression comes back into
31543 The variable object no longer holds a valid value.
31544 This can occur when the executable file being debugged has changed,
31545 either through recompilation or by using the @value{GDBN} @code{file}
31546 command. The front end should normally choose to delete these variable
31550 In the future new values may be added to this list so the front should
31551 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31554 This is only present if the varobj is still valid. If the type
31555 changed, then this will be the string @samp{true}; otherwise it will
31558 When a varobj's type changes, its children are also likely to have
31559 become incorrect. Therefore, the varobj's children are automatically
31560 deleted when this attribute is @samp{true}. Also, the varobj's update
31561 range, when set using the @code{-var-set-update-range} command, is
31565 If the varobj's type changed, then this field will be present and will
31568 @item new_num_children
31569 For a dynamic varobj, if the number of children changed, or if the
31570 type changed, this will be the new number of children.
31572 The @samp{numchild} field in other varobj responses is generally not
31573 valid for a dynamic varobj -- it will show the number of children that
31574 @value{GDBN} knows about, but because dynamic varobjs lazily
31575 instantiate their children, this will not reflect the number of
31576 children which may be available.
31578 The @samp{new_num_children} attribute only reports changes to the
31579 number of children known by @value{GDBN}. This is the only way to
31580 detect whether an update has removed children (which necessarily can
31581 only happen at the end of the update range).
31584 The display hint, if any.
31587 This is an integer value, which will be 1 if there are more children
31588 available outside the varobj's update range.
31591 This attribute will be present and have the value @samp{1} if the
31592 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31593 then this attribute will not be present.
31596 If new children were added to a dynamic varobj within the selected
31597 update range (as set by @code{-var-set-update-range}), then they will
31598 be listed in this attribute.
31601 @subsubheading Example
31608 -var-update --all-values var1
31609 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31610 type_changed="false"@}]
31614 @subheading The @code{-var-set-frozen} Command
31615 @findex -var-set-frozen
31616 @anchor{-var-set-frozen}
31618 @subsubheading Synopsis
31621 -var-set-frozen @var{name} @var{flag}
31624 Set the frozenness flag on the variable object @var{name}. The
31625 @var{flag} parameter should be either @samp{1} to make the variable
31626 frozen or @samp{0} to make it unfrozen. If a variable object is
31627 frozen, then neither itself, nor any of its children, are
31628 implicitly updated by @code{-var-update} of
31629 a parent variable or by @code{-var-update *}. Only
31630 @code{-var-update} of the variable itself will update its value and
31631 values of its children. After a variable object is unfrozen, it is
31632 implicitly updated by all subsequent @code{-var-update} operations.
31633 Unfreezing a variable does not update it, only subsequent
31634 @code{-var-update} does.
31636 @subsubheading Example
31640 -var-set-frozen V 1
31645 @subheading The @code{-var-set-update-range} command
31646 @findex -var-set-update-range
31647 @anchor{-var-set-update-range}
31649 @subsubheading Synopsis
31652 -var-set-update-range @var{name} @var{from} @var{to}
31655 Set the range of children to be returned by future invocations of
31656 @code{-var-update}.
31658 @var{from} and @var{to} indicate the range of children to report. If
31659 @var{from} or @var{to} is less than zero, the range is reset and all
31660 children will be reported. Otherwise, children starting at @var{from}
31661 (zero-based) and up to and excluding @var{to} will be reported.
31663 @subsubheading Example
31667 -var-set-update-range V 1 2
31671 @subheading The @code{-var-set-visualizer} command
31672 @findex -var-set-visualizer
31673 @anchor{-var-set-visualizer}
31675 @subsubheading Synopsis
31678 -var-set-visualizer @var{name} @var{visualizer}
31681 Set a visualizer for the variable object @var{name}.
31683 @var{visualizer} is the visualizer to use. The special value
31684 @samp{None} means to disable any visualizer in use.
31686 If not @samp{None}, @var{visualizer} must be a Python expression.
31687 This expression must evaluate to a callable object which accepts a
31688 single argument. @value{GDBN} will call this object with the value of
31689 the varobj @var{name} as an argument (this is done so that the same
31690 Python pretty-printing code can be used for both the CLI and MI).
31691 When called, this object must return an object which conforms to the
31692 pretty-printing interface (@pxref{Pretty Printing API}).
31694 The pre-defined function @code{gdb.default_visualizer} may be used to
31695 select a visualizer by following the built-in process
31696 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31697 a varobj is created, and so ordinarily is not needed.
31699 This feature is only available if Python support is enabled. The MI
31700 command @code{-list-features} (@pxref{GDB/MI Support Commands})
31701 can be used to check this.
31703 @subsubheading Example
31705 Resetting the visualizer:
31709 -var-set-visualizer V None
31713 Reselecting the default (type-based) visualizer:
31717 -var-set-visualizer V gdb.default_visualizer
31721 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31722 can be used to instantiate this class for a varobj:
31726 -var-set-visualizer V "lambda val: SomeClass()"
31730 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31731 @node GDB/MI Data Manipulation
31732 @section @sc{gdb/mi} Data Manipulation
31734 @cindex data manipulation, in @sc{gdb/mi}
31735 @cindex @sc{gdb/mi}, data manipulation
31736 This section describes the @sc{gdb/mi} commands that manipulate data:
31737 examine memory and registers, evaluate expressions, etc.
31739 For details about what an addressable memory unit is,
31740 @pxref{addressable memory unit}.
31742 @c REMOVED FROM THE INTERFACE.
31743 @c @subheading -data-assign
31744 @c Change the value of a program variable. Plenty of side effects.
31745 @c @subsubheading GDB Command
31747 @c @subsubheading Example
31750 @subheading The @code{-data-disassemble} Command
31751 @findex -data-disassemble
31753 @subsubheading Synopsis
31757 [ -s @var{start-addr} -e @var{end-addr} ]
31758 | [ -a @var{addr} ]
31759 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31767 @item @var{start-addr}
31768 is the beginning address (or @code{$pc})
31769 @item @var{end-addr}
31772 is an address anywhere within (or the name of) the function to
31773 disassemble. If an address is specified, the whole function
31774 surrounding that address will be disassembled. If a name is
31775 specified, the whole function with that name will be disassembled.
31776 @item @var{filename}
31777 is the name of the file to disassemble
31778 @item @var{linenum}
31779 is the line number to disassemble around
31781 is the number of disassembly lines to be produced. If it is -1,
31782 the whole function will be disassembled, in case no @var{end-addr} is
31783 specified. If @var{end-addr} is specified as a non-zero value, and
31784 @var{lines} is lower than the number of disassembly lines between
31785 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31786 displayed; if @var{lines} is higher than the number of lines between
31787 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31792 @item 0 disassembly only
31793 @item 1 mixed source and disassembly (deprecated)
31794 @item 2 disassembly with raw opcodes
31795 @item 3 mixed source and disassembly with raw opcodes (deprecated)
31796 @item 4 mixed source and disassembly
31797 @item 5 mixed source and disassembly with raw opcodes
31800 Modes 1 and 3 are deprecated. The output is ``source centric''
31801 which hasn't proved useful in practice.
31802 @xref{Machine Code}, for a discussion of the difference between
31803 @code{/m} and @code{/s} output of the @code{disassemble} command.
31806 @subsubheading Result
31808 The result of the @code{-data-disassemble} command will be a list named
31809 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31810 used with the @code{-data-disassemble} command.
31812 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31817 The address at which this instruction was disassembled.
31820 The name of the function this instruction is within.
31823 The decimal offset in bytes from the start of @samp{func-name}.
31826 The text disassembly for this @samp{address}.
31829 This field is only present for modes 2, 3 and 5. This contains the raw opcode
31830 bytes for the @samp{inst} field.
31834 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
31835 @samp{src_and_asm_line}, each of which has the following fields:
31839 The line number within @samp{file}.
31842 The file name from the compilation unit. This might be an absolute
31843 file name or a relative file name depending on the compile command
31847 Absolute file name of @samp{file}. It is converted to a canonical form
31848 using the source file search path
31849 (@pxref{Source Path, ,Specifying Source Directories})
31850 and after resolving all the symbolic links.
31852 If the source file is not found this field will contain the path as
31853 present in the debug information.
31855 @item line_asm_insn
31856 This is a list of tuples containing the disassembly for @samp{line} in
31857 @samp{file}. The fields of each tuple are the same as for
31858 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31859 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31864 Note that whatever included in the @samp{inst} field, is not
31865 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31868 @subsubheading @value{GDBN} Command
31870 The corresponding @value{GDBN} command is @samp{disassemble}.
31872 @subsubheading Example
31874 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31878 -data-disassemble -s $pc -e "$pc + 20" -- 0
31881 @{address="0x000107c0",func-name="main",offset="4",
31882 inst="mov 2, %o0"@},
31883 @{address="0x000107c4",func-name="main",offset="8",
31884 inst="sethi %hi(0x11800), %o2"@},
31885 @{address="0x000107c8",func-name="main",offset="12",
31886 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31887 @{address="0x000107cc",func-name="main",offset="16",
31888 inst="sethi %hi(0x11800), %o2"@},
31889 @{address="0x000107d0",func-name="main",offset="20",
31890 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31894 Disassemble the whole @code{main} function. Line 32 is part of
31898 -data-disassemble -f basics.c -l 32 -- 0
31900 @{address="0x000107bc",func-name="main",offset="0",
31901 inst="save %sp, -112, %sp"@},
31902 @{address="0x000107c0",func-name="main",offset="4",
31903 inst="mov 2, %o0"@},
31904 @{address="0x000107c4",func-name="main",offset="8",
31905 inst="sethi %hi(0x11800), %o2"@},
31907 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31908 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31912 Disassemble 3 instructions from the start of @code{main}:
31916 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31918 @{address="0x000107bc",func-name="main",offset="0",
31919 inst="save %sp, -112, %sp"@},
31920 @{address="0x000107c0",func-name="main",offset="4",
31921 inst="mov 2, %o0"@},
31922 @{address="0x000107c4",func-name="main",offset="8",
31923 inst="sethi %hi(0x11800), %o2"@}]
31927 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31931 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31933 src_and_asm_line=@{line="31",
31934 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31935 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31936 line_asm_insn=[@{address="0x000107bc",
31937 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31938 src_and_asm_line=@{line="32",
31939 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31940 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31941 line_asm_insn=[@{address="0x000107c0",
31942 func-name="main",offset="4",inst="mov 2, %o0"@},
31943 @{address="0x000107c4",func-name="main",offset="8",
31944 inst="sethi %hi(0x11800), %o2"@}]@}]
31949 @subheading The @code{-data-evaluate-expression} Command
31950 @findex -data-evaluate-expression
31952 @subsubheading Synopsis
31955 -data-evaluate-expression @var{expr}
31958 Evaluate @var{expr} as an expression. The expression could contain an
31959 inferior function call. The function call will execute synchronously.
31960 If the expression contains spaces, it must be enclosed in double quotes.
31962 @subsubheading @value{GDBN} Command
31964 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31965 @samp{call}. In @code{gdbtk} only, there's a corresponding
31966 @samp{gdb_eval} command.
31968 @subsubheading Example
31970 In the following example, the numbers that precede the commands are the
31971 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31972 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31976 211-data-evaluate-expression A
31979 311-data-evaluate-expression &A
31980 311^done,value="0xefffeb7c"
31982 411-data-evaluate-expression A+3
31985 511-data-evaluate-expression "A + 3"
31991 @subheading The @code{-data-list-changed-registers} Command
31992 @findex -data-list-changed-registers
31994 @subsubheading Synopsis
31997 -data-list-changed-registers
32000 Display a list of the registers that have changed.
32002 @subsubheading @value{GDBN} Command
32004 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
32005 has the corresponding command @samp{gdb_changed_register_list}.
32007 @subsubheading Example
32009 On a PPC MBX board:
32017 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
32018 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
32019 line="5",arch="powerpc"@}
32021 -data-list-changed-registers
32022 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
32023 "10","11","13","14","15","16","17","18","19","20","21","22","23",
32024 "24","25","26","27","28","30","31","64","65","66","67","69"]
32029 @subheading The @code{-data-list-register-names} Command
32030 @findex -data-list-register-names
32032 @subsubheading Synopsis
32035 -data-list-register-names [ ( @var{regno} )+ ]
32038 Show a list of register names for the current target. If no arguments
32039 are given, it shows a list of the names of all the registers. If
32040 integer numbers are given as arguments, it will print a list of the
32041 names of the registers corresponding to the arguments. To ensure
32042 consistency between a register name and its number, the output list may
32043 include empty register names.
32045 @subsubheading @value{GDBN} Command
32047 @value{GDBN} does not have a command which corresponds to
32048 @samp{-data-list-register-names}. In @code{gdbtk} there is a
32049 corresponding command @samp{gdb_regnames}.
32051 @subsubheading Example
32053 For the PPC MBX board:
32056 -data-list-register-names
32057 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
32058 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
32059 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
32060 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
32061 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
32062 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
32063 "", "pc","ps","cr","lr","ctr","xer"]
32065 -data-list-register-names 1 2 3
32066 ^done,register-names=["r1","r2","r3"]
32070 @subheading The @code{-data-list-register-values} Command
32071 @findex -data-list-register-values
32073 @subsubheading Synopsis
32076 -data-list-register-values
32077 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
32080 Display the registers' contents. The format according to which the
32081 registers' contents are to be returned is given by @var{fmt}, followed
32082 by an optional list of numbers specifying the registers to display. A
32083 missing list of numbers indicates that the contents of all the
32084 registers must be returned. The @code{--skip-unavailable} option
32085 indicates that only the available registers are to be returned.
32087 Allowed formats for @var{fmt} are:
32104 @subsubheading @value{GDBN} Command
32106 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
32107 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
32109 @subsubheading Example
32111 For a PPC MBX board (note: line breaks are for readability only, they
32112 don't appear in the actual output):
32116 -data-list-register-values r 64 65
32117 ^done,register-values=[@{number="64",value="0xfe00a300"@},
32118 @{number="65",value="0x00029002"@}]
32120 -data-list-register-values x
32121 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
32122 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
32123 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
32124 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
32125 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
32126 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
32127 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
32128 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
32129 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
32130 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
32131 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
32132 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
32133 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
32134 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
32135 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
32136 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
32137 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
32138 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
32139 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
32140 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
32141 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
32142 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
32143 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
32144 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
32145 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
32146 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
32147 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
32148 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
32149 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
32150 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
32151 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
32152 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
32153 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
32154 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
32155 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
32156 @{number="69",value="0x20002b03"@}]
32161 @subheading The @code{-data-read-memory} Command
32162 @findex -data-read-memory
32164 This command is deprecated, use @code{-data-read-memory-bytes} instead.
32166 @subsubheading Synopsis
32169 -data-read-memory [ -o @var{byte-offset} ]
32170 @var{address} @var{word-format} @var{word-size}
32171 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
32178 @item @var{address}
32179 An expression specifying the address of the first memory word to be
32180 read. Complex expressions containing embedded white space should be
32181 quoted using the C convention.
32183 @item @var{word-format}
32184 The format to be used to print the memory words. The notation is the
32185 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
32188 @item @var{word-size}
32189 The size of each memory word in bytes.
32191 @item @var{nr-rows}
32192 The number of rows in the output table.
32194 @item @var{nr-cols}
32195 The number of columns in the output table.
32198 If present, indicates that each row should include an @sc{ascii} dump. The
32199 value of @var{aschar} is used as a padding character when a byte is not a
32200 member of the printable @sc{ascii} character set (printable @sc{ascii}
32201 characters are those whose code is between 32 and 126, inclusively).
32203 @item @var{byte-offset}
32204 An offset to add to the @var{address} before fetching memory.
32207 This command displays memory contents as a table of @var{nr-rows} by
32208 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
32209 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
32210 (returned as @samp{total-bytes}). Should less than the requested number
32211 of bytes be returned by the target, the missing words are identified
32212 using @samp{N/A}. The number of bytes read from the target is returned
32213 in @samp{nr-bytes} and the starting address used to read memory in
32216 The address of the next/previous row or page is available in
32217 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
32220 @subsubheading @value{GDBN} Command
32222 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
32223 @samp{gdb_get_mem} memory read command.
32225 @subsubheading Example
32227 Read six bytes of memory starting at @code{bytes+6} but then offset by
32228 @code{-6} bytes. Format as three rows of two columns. One byte per
32229 word. Display each word in hex.
32233 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
32234 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
32235 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
32236 prev-page="0x0000138a",memory=[
32237 @{addr="0x00001390",data=["0x00","0x01"]@},
32238 @{addr="0x00001392",data=["0x02","0x03"]@},
32239 @{addr="0x00001394",data=["0x04","0x05"]@}]
32243 Read two bytes of memory starting at address @code{shorts + 64} and
32244 display as a single word formatted in decimal.
32248 5-data-read-memory shorts+64 d 2 1 1
32249 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
32250 next-row="0x00001512",prev-row="0x0000150e",
32251 next-page="0x00001512",prev-page="0x0000150e",memory=[
32252 @{addr="0x00001510",data=["128"]@}]
32256 Read thirty two bytes of memory starting at @code{bytes+16} and format
32257 as eight rows of four columns. Include a string encoding with @samp{x}
32258 used as the non-printable character.
32262 4-data-read-memory bytes+16 x 1 8 4 x
32263 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
32264 next-row="0x000013c0",prev-row="0x0000139c",
32265 next-page="0x000013c0",prev-page="0x00001380",memory=[
32266 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
32267 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
32268 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
32269 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
32270 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
32271 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
32272 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
32273 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
32277 @subheading The @code{-data-read-memory-bytes} Command
32278 @findex -data-read-memory-bytes
32280 @subsubheading Synopsis
32283 -data-read-memory-bytes [ -o @var{offset} ]
32284 @var{address} @var{count}
32291 @item @var{address}
32292 An expression specifying the address of the first addressable memory unit
32293 to be read. Complex expressions containing embedded white space should be
32294 quoted using the C convention.
32297 The number of addressable memory units to read. This should be an integer
32301 The offset relative to @var{address} at which to start reading. This
32302 should be an integer literal. This option is provided so that a frontend
32303 is not required to first evaluate address and then perform address
32304 arithmetics itself.
32308 This command attempts to read all accessible memory regions in the
32309 specified range. First, all regions marked as unreadable in the memory
32310 map (if one is defined) will be skipped. @xref{Memory Region
32311 Attributes}. Second, @value{GDBN} will attempt to read the remaining
32312 regions. For each one, if reading full region results in an errors,
32313 @value{GDBN} will try to read a subset of the region.
32315 In general, every single memory unit in the region may be readable or not,
32316 and the only way to read every readable unit is to try a read at
32317 every address, which is not practical. Therefore, @value{GDBN} will
32318 attempt to read all accessible memory units at either beginning or the end
32319 of the region, using a binary division scheme. This heuristic works
32320 well for reading accross a memory map boundary. Note that if a region
32321 has a readable range that is neither at the beginning or the end,
32322 @value{GDBN} will not read it.
32324 The result record (@pxref{GDB/MI Result Records}) that is output of
32325 the command includes a field named @samp{memory} whose content is a
32326 list of tuples. Each tuple represent a successfully read memory block
32327 and has the following fields:
32331 The start address of the memory block, as hexadecimal literal.
32334 The end address of the memory block, as hexadecimal literal.
32337 The offset of the memory block, as hexadecimal literal, relative to
32338 the start address passed to @code{-data-read-memory-bytes}.
32341 The contents of the memory block, in hex.
32347 @subsubheading @value{GDBN} Command
32349 The corresponding @value{GDBN} command is @samp{x}.
32351 @subsubheading Example
32355 -data-read-memory-bytes &a 10
32356 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
32358 contents="01000000020000000300"@}]
32363 @subheading The @code{-data-write-memory-bytes} Command
32364 @findex -data-write-memory-bytes
32366 @subsubheading Synopsis
32369 -data-write-memory-bytes @var{address} @var{contents}
32370 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
32377 @item @var{address}
32378 An expression specifying the address of the first addressable memory unit
32379 to be written. Complex expressions containing embedded white space should
32380 be quoted using the C convention.
32382 @item @var{contents}
32383 The hex-encoded data to write. It is an error if @var{contents} does
32384 not represent an integral number of addressable memory units.
32387 Optional argument indicating the number of addressable memory units to be
32388 written. If @var{count} is greater than @var{contents}' length,
32389 @value{GDBN} will repeatedly write @var{contents} until it fills
32390 @var{count} memory units.
32394 @subsubheading @value{GDBN} Command
32396 There's no corresponding @value{GDBN} command.
32398 @subsubheading Example
32402 -data-write-memory-bytes &a "aabbccdd"
32409 -data-write-memory-bytes &a "aabbccdd" 16e
32414 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32415 @node GDB/MI Tracepoint Commands
32416 @section @sc{gdb/mi} Tracepoint Commands
32418 The commands defined in this section implement MI support for
32419 tracepoints. For detailed introduction, see @ref{Tracepoints}.
32421 @subheading The @code{-trace-find} Command
32422 @findex -trace-find
32424 @subsubheading Synopsis
32427 -trace-find @var{mode} [@var{parameters}@dots{}]
32430 Find a trace frame using criteria defined by @var{mode} and
32431 @var{parameters}. The following table lists permissible
32432 modes and their parameters. For details of operation, see @ref{tfind}.
32437 No parameters are required. Stops examining trace frames.
32440 An integer is required as parameter. Selects tracepoint frame with
32443 @item tracepoint-number
32444 An integer is required as parameter. Finds next
32445 trace frame that corresponds to tracepoint with the specified number.
32448 An address is required as parameter. Finds
32449 next trace frame that corresponds to any tracepoint at the specified
32452 @item pc-inside-range
32453 Two addresses are required as parameters. Finds next trace
32454 frame that corresponds to a tracepoint at an address inside the
32455 specified range. Both bounds are considered to be inside the range.
32457 @item pc-outside-range
32458 Two addresses are required as parameters. Finds
32459 next trace frame that corresponds to a tracepoint at an address outside
32460 the specified range. Both bounds are considered to be inside the range.
32463 Line specification is required as parameter. @xref{Specify Location}.
32464 Finds next trace frame that corresponds to a tracepoint at
32465 the specified location.
32469 If @samp{none} was passed as @var{mode}, the response does not
32470 have fields. Otherwise, the response may have the following fields:
32474 This field has either @samp{0} or @samp{1} as the value, depending
32475 on whether a matching tracepoint was found.
32478 The index of the found traceframe. This field is present iff
32479 the @samp{found} field has value of @samp{1}.
32482 The index of the found tracepoint. This field is present iff
32483 the @samp{found} field has value of @samp{1}.
32486 The information about the frame corresponding to the found trace
32487 frame. This field is present only if a trace frame was found.
32488 @xref{GDB/MI Frame Information}, for description of this field.
32492 @subsubheading @value{GDBN} Command
32494 The corresponding @value{GDBN} command is @samp{tfind}.
32496 @subheading -trace-define-variable
32497 @findex -trace-define-variable
32499 @subsubheading Synopsis
32502 -trace-define-variable @var{name} [ @var{value} ]
32505 Create trace variable @var{name} if it does not exist. If
32506 @var{value} is specified, sets the initial value of the specified
32507 trace variable to that value. Note that the @var{name} should start
32508 with the @samp{$} character.
32510 @subsubheading @value{GDBN} Command
32512 The corresponding @value{GDBN} command is @samp{tvariable}.
32514 @subheading The @code{-trace-frame-collected} Command
32515 @findex -trace-frame-collected
32517 @subsubheading Synopsis
32520 -trace-frame-collected
32521 [--var-print-values @var{var_pval}]
32522 [--comp-print-values @var{comp_pval}]
32523 [--registers-format @var{regformat}]
32524 [--memory-contents]
32527 This command returns the set of collected objects, register names,
32528 trace state variable names, memory ranges and computed expressions
32529 that have been collected at a particular trace frame. The optional
32530 parameters to the command affect the output format in different ways.
32531 See the output description table below for more details.
32533 The reported names can be used in the normal manner to create
32534 varobjs and inspect the objects themselves. The items returned by
32535 this command are categorized so that it is clear which is a variable,
32536 which is a register, which is a trace state variable, which is a
32537 memory range and which is a computed expression.
32539 For instance, if the actions were
32541 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
32542 collect *(int*)0xaf02bef0@@40
32546 the object collected in its entirety would be @code{myVar}. The
32547 object @code{myArray} would be partially collected, because only the
32548 element at index @code{myIndex} would be collected. The remaining
32549 objects would be computed expressions.
32551 An example output would be:
32555 -trace-frame-collected
32557 explicit-variables=[@{name="myVar",value="1"@}],
32558 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
32559 @{name="myObj.field",value="0"@},
32560 @{name="myPtr->field",value="1"@},
32561 @{name="myCount + 2",value="3"@},
32562 @{name="$tvar1 + 1",value="43970027"@}],
32563 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
32564 @{number="1",value="0x0"@},
32565 @{number="2",value="0x4"@},
32567 @{number="125",value="0x0"@}],
32568 tvars=[@{name="$tvar1",current="43970026"@}],
32569 memory=[@{address="0x0000000000602264",length="4"@},
32570 @{address="0x0000000000615bc0",length="4"@}]
32577 @item explicit-variables
32578 The set of objects that have been collected in their entirety (as
32579 opposed to collecting just a few elements of an array or a few struct
32580 members). For each object, its name and value are printed.
32581 The @code{--var-print-values} option affects how or whether the value
32582 field is output. If @var{var_pval} is 0, then print only the names;
32583 if it is 1, print also their values; and if it is 2, print the name,
32584 type and value for simple data types, and the name and type for
32585 arrays, structures and unions.
32587 @item computed-expressions
32588 The set of computed expressions that have been collected at the
32589 current trace frame. The @code{--comp-print-values} option affects
32590 this set like the @code{--var-print-values} option affects the
32591 @code{explicit-variables} set. See above.
32594 The registers that have been collected at the current trace frame.
32595 For each register collected, the name and current value are returned.
32596 The value is formatted according to the @code{--registers-format}
32597 option. See the @command{-data-list-register-values} command for a
32598 list of the allowed formats. The default is @samp{x}.
32601 The trace state variables that have been collected at the current
32602 trace frame. For each trace state variable collected, the name and
32603 current value are returned.
32606 The set of memory ranges that have been collected at the current trace
32607 frame. Its content is a list of tuples. Each tuple represents a
32608 collected memory range and has the following fields:
32612 The start address of the memory range, as hexadecimal literal.
32615 The length of the memory range, as decimal literal.
32618 The contents of the memory block, in hex. This field is only present
32619 if the @code{--memory-contents} option is specified.
32625 @subsubheading @value{GDBN} Command
32627 There is no corresponding @value{GDBN} command.
32629 @subsubheading Example
32631 @subheading -trace-list-variables
32632 @findex -trace-list-variables
32634 @subsubheading Synopsis
32637 -trace-list-variables
32640 Return a table of all defined trace variables. Each element of the
32641 table has the following fields:
32645 The name of the trace variable. This field is always present.
32648 The initial value. This is a 64-bit signed integer. This
32649 field is always present.
32652 The value the trace variable has at the moment. This is a 64-bit
32653 signed integer. This field is absent iff current value is
32654 not defined, for example if the trace was never run, or is
32659 @subsubheading @value{GDBN} Command
32661 The corresponding @value{GDBN} command is @samp{tvariables}.
32663 @subsubheading Example
32667 -trace-list-variables
32668 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32669 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32670 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32671 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32672 body=[variable=@{name="$trace_timestamp",initial="0"@}
32673 variable=@{name="$foo",initial="10",current="15"@}]@}
32677 @subheading -trace-save
32678 @findex -trace-save
32680 @subsubheading Synopsis
32683 -trace-save [ -r ] [ -ctf ] @var{filename}
32686 Saves the collected trace data to @var{filename}. Without the
32687 @samp{-r} option, the data is downloaded from the target and saved
32688 in a local file. With the @samp{-r} option the target is asked
32689 to perform the save.
32691 By default, this command will save the trace in the tfile format. You can
32692 supply the optional @samp{-ctf} argument to save it the CTF format. See
32693 @ref{Trace Files} for more information about CTF.
32695 @subsubheading @value{GDBN} Command
32697 The corresponding @value{GDBN} command is @samp{tsave}.
32700 @subheading -trace-start
32701 @findex -trace-start
32703 @subsubheading Synopsis
32709 Starts a tracing experiment. The result of this command does not
32712 @subsubheading @value{GDBN} Command
32714 The corresponding @value{GDBN} command is @samp{tstart}.
32716 @subheading -trace-status
32717 @findex -trace-status
32719 @subsubheading Synopsis
32725 Obtains the status of a tracing experiment. The result may include
32726 the following fields:
32731 May have a value of either @samp{0}, when no tracing operations are
32732 supported, @samp{1}, when all tracing operations are supported, or
32733 @samp{file} when examining trace file. In the latter case, examining
32734 of trace frame is possible but new tracing experiement cannot be
32735 started. This field is always present.
32738 May have a value of either @samp{0} or @samp{1} depending on whether
32739 tracing experiement is in progress on target. This field is present
32740 if @samp{supported} field is not @samp{0}.
32743 Report the reason why the tracing was stopped last time. This field
32744 may be absent iff tracing was never stopped on target yet. The
32745 value of @samp{request} means the tracing was stopped as result of
32746 the @code{-trace-stop} command. The value of @samp{overflow} means
32747 the tracing buffer is full. The value of @samp{disconnection} means
32748 tracing was automatically stopped when @value{GDBN} has disconnected.
32749 The value of @samp{passcount} means tracing was stopped when a
32750 tracepoint was passed a maximal number of times for that tracepoint.
32751 This field is present if @samp{supported} field is not @samp{0}.
32753 @item stopping-tracepoint
32754 The number of tracepoint whose passcount as exceeded. This field is
32755 present iff the @samp{stop-reason} field has the value of
32759 @itemx frames-created
32760 The @samp{frames} field is a count of the total number of trace frames
32761 in the trace buffer, while @samp{frames-created} is the total created
32762 during the run, including ones that were discarded, such as when a
32763 circular trace buffer filled up. Both fields are optional.
32767 These fields tell the current size of the tracing buffer and the
32768 remaining space. These fields are optional.
32771 The value of the circular trace buffer flag. @code{1} means that the
32772 trace buffer is circular and old trace frames will be discarded if
32773 necessary to make room, @code{0} means that the trace buffer is linear
32777 The value of the disconnected tracing flag. @code{1} means that
32778 tracing will continue after @value{GDBN} disconnects, @code{0} means
32779 that the trace run will stop.
32782 The filename of the trace file being examined. This field is
32783 optional, and only present when examining a trace file.
32787 @subsubheading @value{GDBN} Command
32789 The corresponding @value{GDBN} command is @samp{tstatus}.
32791 @subheading -trace-stop
32792 @findex -trace-stop
32794 @subsubheading Synopsis
32800 Stops a tracing experiment. The result of this command has the same
32801 fields as @code{-trace-status}, except that the @samp{supported} and
32802 @samp{running} fields are not output.
32804 @subsubheading @value{GDBN} Command
32806 The corresponding @value{GDBN} command is @samp{tstop}.
32809 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32810 @node GDB/MI Symbol Query
32811 @section @sc{gdb/mi} Symbol Query Commands
32815 @subheading The @code{-symbol-info-address} Command
32816 @findex -symbol-info-address
32818 @subsubheading Synopsis
32821 -symbol-info-address @var{symbol}
32824 Describe where @var{symbol} is stored.
32826 @subsubheading @value{GDBN} Command
32828 The corresponding @value{GDBN} command is @samp{info address}.
32830 @subsubheading Example
32834 @subheading The @code{-symbol-info-file} Command
32835 @findex -symbol-info-file
32837 @subsubheading Synopsis
32843 Show the file for the symbol.
32845 @subsubheading @value{GDBN} Command
32847 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32848 @samp{gdb_find_file}.
32850 @subsubheading Example
32854 @subheading The @code{-symbol-info-function} Command
32855 @findex -symbol-info-function
32857 @subsubheading Synopsis
32860 -symbol-info-function
32863 Show which function the symbol lives in.
32865 @subsubheading @value{GDBN} Command
32867 @samp{gdb_get_function} in @code{gdbtk}.
32869 @subsubheading Example
32873 @subheading The @code{-symbol-info-line} Command
32874 @findex -symbol-info-line
32876 @subsubheading Synopsis
32882 Show the core addresses of the code for a source line.
32884 @subsubheading @value{GDBN} Command
32886 The corresponding @value{GDBN} command is @samp{info line}.
32887 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32889 @subsubheading Example
32893 @subheading The @code{-symbol-info-symbol} Command
32894 @findex -symbol-info-symbol
32896 @subsubheading Synopsis
32899 -symbol-info-symbol @var{addr}
32902 Describe what symbol is at location @var{addr}.
32904 @subsubheading @value{GDBN} Command
32906 The corresponding @value{GDBN} command is @samp{info symbol}.
32908 @subsubheading Example
32912 @subheading The @code{-symbol-list-functions} Command
32913 @findex -symbol-list-functions
32915 @subsubheading Synopsis
32918 -symbol-list-functions
32921 List the functions in the executable.
32923 @subsubheading @value{GDBN} Command
32925 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32926 @samp{gdb_search} in @code{gdbtk}.
32928 @subsubheading Example
32933 @subheading The @code{-symbol-list-lines} Command
32934 @findex -symbol-list-lines
32936 @subsubheading Synopsis
32939 -symbol-list-lines @var{filename}
32942 Print the list of lines that contain code and their associated program
32943 addresses for the given source filename. The entries are sorted in
32944 ascending PC order.
32946 @subsubheading @value{GDBN} Command
32948 There is no corresponding @value{GDBN} command.
32950 @subsubheading Example
32953 -symbol-list-lines basics.c
32954 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32960 @subheading The @code{-symbol-list-types} Command
32961 @findex -symbol-list-types
32963 @subsubheading Synopsis
32969 List all the type names.
32971 @subsubheading @value{GDBN} Command
32973 The corresponding commands are @samp{info types} in @value{GDBN},
32974 @samp{gdb_search} in @code{gdbtk}.
32976 @subsubheading Example
32980 @subheading The @code{-symbol-list-variables} Command
32981 @findex -symbol-list-variables
32983 @subsubheading Synopsis
32986 -symbol-list-variables
32989 List all the global and static variable names.
32991 @subsubheading @value{GDBN} Command
32993 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32995 @subsubheading Example
32999 @subheading The @code{-symbol-locate} Command
33000 @findex -symbol-locate
33002 @subsubheading Synopsis
33008 @subsubheading @value{GDBN} Command
33010 @samp{gdb_loc} in @code{gdbtk}.
33012 @subsubheading Example
33016 @subheading The @code{-symbol-type} Command
33017 @findex -symbol-type
33019 @subsubheading Synopsis
33022 -symbol-type @var{variable}
33025 Show type of @var{variable}.
33027 @subsubheading @value{GDBN} Command
33029 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
33030 @samp{gdb_obj_variable}.
33032 @subsubheading Example
33037 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33038 @node GDB/MI File Commands
33039 @section @sc{gdb/mi} File Commands
33041 This section describes the GDB/MI commands to specify executable file names
33042 and to read in and obtain symbol table information.
33044 @subheading The @code{-file-exec-and-symbols} Command
33045 @findex -file-exec-and-symbols
33047 @subsubheading Synopsis
33050 -file-exec-and-symbols @var{file}
33053 Specify the executable file to be debugged. This file is the one from
33054 which the symbol table is also read. If no file is specified, the
33055 command clears the executable and symbol information. If breakpoints
33056 are set when using this command with no arguments, @value{GDBN} will produce
33057 error messages. Otherwise, no output is produced, except a completion
33060 @subsubheading @value{GDBN} Command
33062 The corresponding @value{GDBN} command is @samp{file}.
33064 @subsubheading Example
33068 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33074 @subheading The @code{-file-exec-file} Command
33075 @findex -file-exec-file
33077 @subsubheading Synopsis
33080 -file-exec-file @var{file}
33083 Specify the executable file to be debugged. Unlike
33084 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
33085 from this file. If used without argument, @value{GDBN} clears the information
33086 about the executable file. No output is produced, except a completion
33089 @subsubheading @value{GDBN} Command
33091 The corresponding @value{GDBN} command is @samp{exec-file}.
33093 @subsubheading Example
33097 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33104 @subheading The @code{-file-list-exec-sections} Command
33105 @findex -file-list-exec-sections
33107 @subsubheading Synopsis
33110 -file-list-exec-sections
33113 List the sections of the current executable file.
33115 @subsubheading @value{GDBN} Command
33117 The @value{GDBN} command @samp{info file} shows, among the rest, the same
33118 information as this command. @code{gdbtk} has a corresponding command
33119 @samp{gdb_load_info}.
33121 @subsubheading Example
33126 @subheading The @code{-file-list-exec-source-file} Command
33127 @findex -file-list-exec-source-file
33129 @subsubheading Synopsis
33132 -file-list-exec-source-file
33135 List the line number, the current source file, and the absolute path
33136 to the current source file for the current executable. The macro
33137 information field has a value of @samp{1} or @samp{0} depending on
33138 whether or not the file includes preprocessor macro information.
33140 @subsubheading @value{GDBN} Command
33142 The @value{GDBN} equivalent is @samp{info source}
33144 @subsubheading Example
33148 123-file-list-exec-source-file
33149 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
33154 @subheading The @code{-file-list-exec-source-files} Command
33155 @findex -file-list-exec-source-files
33157 @subsubheading Synopsis
33160 -file-list-exec-source-files
33163 List the source files for the current executable.
33165 It will always output both the filename and fullname (absolute file
33166 name) of a source file.
33168 @subsubheading @value{GDBN} Command
33170 The @value{GDBN} equivalent is @samp{info sources}.
33171 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
33173 @subsubheading Example
33176 -file-list-exec-source-files
33178 @{file=foo.c,fullname=/home/foo.c@},
33179 @{file=/home/bar.c,fullname=/home/bar.c@},
33180 @{file=gdb_could_not_find_fullpath.c@}]
33184 @subheading The @code{-file-list-shared-libraries} Command
33185 @findex -file-list-shared-libraries
33187 @subsubheading Synopsis
33190 -file-list-shared-libraries [ @var{regexp} ]
33193 List the shared libraries in the program.
33194 With a regular expression @var{regexp}, only those libraries whose
33195 names match @var{regexp} are listed.
33197 @subsubheading @value{GDBN} Command
33199 The corresponding @value{GDBN} command is @samp{info shared}. The fields
33200 have a similar meaning to the @code{=library-loaded} notification.
33201 The @code{ranges} field specifies the multiple segments belonging to this
33202 library. Each range has the following fields:
33206 The address defining the inclusive lower bound of the segment.
33208 The address defining the exclusive upper bound of the segment.
33211 @subsubheading Example
33214 -file-list-exec-source-files
33215 ^done,shared-libraries=[
33216 @{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"@}]@},
33217 @{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"@}]@}]
33223 @subheading The @code{-file-list-symbol-files} Command
33224 @findex -file-list-symbol-files
33226 @subsubheading Synopsis
33229 -file-list-symbol-files
33234 @subsubheading @value{GDBN} Command
33236 The corresponding @value{GDBN} command is @samp{info file} (part of it).
33238 @subsubheading Example
33243 @subheading The @code{-file-symbol-file} Command
33244 @findex -file-symbol-file
33246 @subsubheading Synopsis
33249 -file-symbol-file @var{file}
33252 Read symbol table info from the specified @var{file} argument. When
33253 used without arguments, clears @value{GDBN}'s symbol table info. No output is
33254 produced, except for a completion notification.
33256 @subsubheading @value{GDBN} Command
33258 The corresponding @value{GDBN} command is @samp{symbol-file}.
33260 @subsubheading Example
33264 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33270 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33271 @node GDB/MI Memory Overlay Commands
33272 @section @sc{gdb/mi} Memory Overlay Commands
33274 The memory overlay commands are not implemented.
33276 @c @subheading -overlay-auto
33278 @c @subheading -overlay-list-mapping-state
33280 @c @subheading -overlay-list-overlays
33282 @c @subheading -overlay-map
33284 @c @subheading -overlay-off
33286 @c @subheading -overlay-on
33288 @c @subheading -overlay-unmap
33290 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33291 @node GDB/MI Signal Handling Commands
33292 @section @sc{gdb/mi} Signal Handling Commands
33294 Signal handling commands are not implemented.
33296 @c @subheading -signal-handle
33298 @c @subheading -signal-list-handle-actions
33300 @c @subheading -signal-list-signal-types
33304 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33305 @node GDB/MI Target Manipulation
33306 @section @sc{gdb/mi} Target Manipulation Commands
33309 @subheading The @code{-target-attach} Command
33310 @findex -target-attach
33312 @subsubheading Synopsis
33315 -target-attach @var{pid} | @var{gid} | @var{file}
33318 Attach to a process @var{pid} or a file @var{file} outside of
33319 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
33320 group, the id previously returned by
33321 @samp{-list-thread-groups --available} must be used.
33323 @subsubheading @value{GDBN} Command
33325 The corresponding @value{GDBN} command is @samp{attach}.
33327 @subsubheading Example
33331 =thread-created,id="1"
33332 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
33338 @subheading The @code{-target-compare-sections} Command
33339 @findex -target-compare-sections
33341 @subsubheading Synopsis
33344 -target-compare-sections [ @var{section} ]
33347 Compare data of section @var{section} on target to the exec file.
33348 Without the argument, all sections are compared.
33350 @subsubheading @value{GDBN} Command
33352 The @value{GDBN} equivalent is @samp{compare-sections}.
33354 @subsubheading Example
33359 @subheading The @code{-target-detach} Command
33360 @findex -target-detach
33362 @subsubheading Synopsis
33365 -target-detach [ @var{pid} | @var{gid} ]
33368 Detach from the remote target which normally resumes its execution.
33369 If either @var{pid} or @var{gid} is specified, detaches from either
33370 the specified process, or specified thread group. There's no output.
33372 @subsubheading @value{GDBN} Command
33374 The corresponding @value{GDBN} command is @samp{detach}.
33376 @subsubheading Example
33386 @subheading The @code{-target-disconnect} Command
33387 @findex -target-disconnect
33389 @subsubheading Synopsis
33395 Disconnect from the remote target. There's no output and the target is
33396 generally not resumed.
33398 @subsubheading @value{GDBN} Command
33400 The corresponding @value{GDBN} command is @samp{disconnect}.
33402 @subsubheading Example
33412 @subheading The @code{-target-download} Command
33413 @findex -target-download
33415 @subsubheading Synopsis
33421 Loads the executable onto the remote target.
33422 It prints out an update message every half second, which includes the fields:
33426 The name of the section.
33428 The size of what has been sent so far for that section.
33430 The size of the section.
33432 The total size of what was sent so far (the current and the previous sections).
33434 The size of the overall executable to download.
33438 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
33439 @sc{gdb/mi} Output Syntax}).
33441 In addition, it prints the name and size of the sections, as they are
33442 downloaded. These messages include the following fields:
33446 The name of the section.
33448 The size of the section.
33450 The size of the overall executable to download.
33454 At the end, a summary is printed.
33456 @subsubheading @value{GDBN} Command
33458 The corresponding @value{GDBN} command is @samp{load}.
33460 @subsubheading Example
33462 Note: each status message appears on a single line. Here the messages
33463 have been broken down so that they can fit onto a page.
33468 +download,@{section=".text",section-size="6668",total-size="9880"@}
33469 +download,@{section=".text",section-sent="512",section-size="6668",
33470 total-sent="512",total-size="9880"@}
33471 +download,@{section=".text",section-sent="1024",section-size="6668",
33472 total-sent="1024",total-size="9880"@}
33473 +download,@{section=".text",section-sent="1536",section-size="6668",
33474 total-sent="1536",total-size="9880"@}
33475 +download,@{section=".text",section-sent="2048",section-size="6668",
33476 total-sent="2048",total-size="9880"@}
33477 +download,@{section=".text",section-sent="2560",section-size="6668",
33478 total-sent="2560",total-size="9880"@}
33479 +download,@{section=".text",section-sent="3072",section-size="6668",
33480 total-sent="3072",total-size="9880"@}
33481 +download,@{section=".text",section-sent="3584",section-size="6668",
33482 total-sent="3584",total-size="9880"@}
33483 +download,@{section=".text",section-sent="4096",section-size="6668",
33484 total-sent="4096",total-size="9880"@}
33485 +download,@{section=".text",section-sent="4608",section-size="6668",
33486 total-sent="4608",total-size="9880"@}
33487 +download,@{section=".text",section-sent="5120",section-size="6668",
33488 total-sent="5120",total-size="9880"@}
33489 +download,@{section=".text",section-sent="5632",section-size="6668",
33490 total-sent="5632",total-size="9880"@}
33491 +download,@{section=".text",section-sent="6144",section-size="6668",
33492 total-sent="6144",total-size="9880"@}
33493 +download,@{section=".text",section-sent="6656",section-size="6668",
33494 total-sent="6656",total-size="9880"@}
33495 +download,@{section=".init",section-size="28",total-size="9880"@}
33496 +download,@{section=".fini",section-size="28",total-size="9880"@}
33497 +download,@{section=".data",section-size="3156",total-size="9880"@}
33498 +download,@{section=".data",section-sent="512",section-size="3156",
33499 total-sent="7236",total-size="9880"@}
33500 +download,@{section=".data",section-sent="1024",section-size="3156",
33501 total-sent="7748",total-size="9880"@}
33502 +download,@{section=".data",section-sent="1536",section-size="3156",
33503 total-sent="8260",total-size="9880"@}
33504 +download,@{section=".data",section-sent="2048",section-size="3156",
33505 total-sent="8772",total-size="9880"@}
33506 +download,@{section=".data",section-sent="2560",section-size="3156",
33507 total-sent="9284",total-size="9880"@}
33508 +download,@{section=".data",section-sent="3072",section-size="3156",
33509 total-sent="9796",total-size="9880"@}
33510 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
33517 @subheading The @code{-target-exec-status} Command
33518 @findex -target-exec-status
33520 @subsubheading Synopsis
33523 -target-exec-status
33526 Provide information on the state of the target (whether it is running or
33527 not, for instance).
33529 @subsubheading @value{GDBN} Command
33531 There's no equivalent @value{GDBN} command.
33533 @subsubheading Example
33537 @subheading The @code{-target-list-available-targets} Command
33538 @findex -target-list-available-targets
33540 @subsubheading Synopsis
33543 -target-list-available-targets
33546 List the possible targets to connect to.
33548 @subsubheading @value{GDBN} Command
33550 The corresponding @value{GDBN} command is @samp{help target}.
33552 @subsubheading Example
33556 @subheading The @code{-target-list-current-targets} Command
33557 @findex -target-list-current-targets
33559 @subsubheading Synopsis
33562 -target-list-current-targets
33565 Describe the current target.
33567 @subsubheading @value{GDBN} Command
33569 The corresponding information is printed by @samp{info file} (among
33572 @subsubheading Example
33576 @subheading The @code{-target-list-parameters} Command
33577 @findex -target-list-parameters
33579 @subsubheading Synopsis
33582 -target-list-parameters
33588 @subsubheading @value{GDBN} Command
33592 @subsubheading Example
33595 @subheading The @code{-target-flash-erase} Command
33596 @findex -target-flash-erase
33598 @subsubheading Synopsis
33601 -target-flash-erase
33604 Erases all known flash memory regions on the target.
33606 The corresponding @value{GDBN} command is @samp{flash-erase}.
33608 The output is a list of flash regions that have been erased, with starting
33609 addresses and memory region sizes.
33613 -target-flash-erase
33614 ^done,erased-regions=@{address="0x0",size="0x40000"@}
33618 @subheading The @code{-target-select} Command
33619 @findex -target-select
33621 @subsubheading Synopsis
33624 -target-select @var{type} @var{parameters @dots{}}
33627 Connect @value{GDBN} to the remote target. This command takes two args:
33631 The type of target, for instance @samp{remote}, etc.
33632 @item @var{parameters}
33633 Device names, host names and the like. @xref{Target Commands, ,
33634 Commands for Managing Targets}, for more details.
33637 The output is a connection notification, followed by the address at
33638 which the target program is, in the following form:
33641 ^connected,addr="@var{address}",func="@var{function name}",
33642 args=[@var{arg list}]
33645 @subsubheading @value{GDBN} Command
33647 The corresponding @value{GDBN} command is @samp{target}.
33649 @subsubheading Example
33653 -target-select remote /dev/ttya
33654 ^connected,addr="0xfe00a300",func="??",args=[]
33658 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33659 @node GDB/MI File Transfer Commands
33660 @section @sc{gdb/mi} File Transfer Commands
33663 @subheading The @code{-target-file-put} Command
33664 @findex -target-file-put
33666 @subsubheading Synopsis
33669 -target-file-put @var{hostfile} @var{targetfile}
33672 Copy file @var{hostfile} from the host system (the machine running
33673 @value{GDBN}) to @var{targetfile} on the target system.
33675 @subsubheading @value{GDBN} Command
33677 The corresponding @value{GDBN} command is @samp{remote put}.
33679 @subsubheading Example
33683 -target-file-put localfile remotefile
33689 @subheading The @code{-target-file-get} Command
33690 @findex -target-file-get
33692 @subsubheading Synopsis
33695 -target-file-get @var{targetfile} @var{hostfile}
33698 Copy file @var{targetfile} from the target system to @var{hostfile}
33699 on the host system.
33701 @subsubheading @value{GDBN} Command
33703 The corresponding @value{GDBN} command is @samp{remote get}.
33705 @subsubheading Example
33709 -target-file-get remotefile localfile
33715 @subheading The @code{-target-file-delete} Command
33716 @findex -target-file-delete
33718 @subsubheading Synopsis
33721 -target-file-delete @var{targetfile}
33724 Delete @var{targetfile} from the target system.
33726 @subsubheading @value{GDBN} Command
33728 The corresponding @value{GDBN} command is @samp{remote delete}.
33730 @subsubheading Example
33734 -target-file-delete remotefile
33740 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33741 @node GDB/MI Ada Exceptions Commands
33742 @section Ada Exceptions @sc{gdb/mi} Commands
33744 @subheading The @code{-info-ada-exceptions} Command
33745 @findex -info-ada-exceptions
33747 @subsubheading Synopsis
33750 -info-ada-exceptions [ @var{regexp}]
33753 List all Ada exceptions defined within the program being debugged.
33754 With a regular expression @var{regexp}, only those exceptions whose
33755 names match @var{regexp} are listed.
33757 @subsubheading @value{GDBN} Command
33759 The corresponding @value{GDBN} command is @samp{info exceptions}.
33761 @subsubheading Result
33763 The result is a table of Ada exceptions. The following columns are
33764 defined for each exception:
33768 The name of the exception.
33771 The address of the exception.
33775 @subsubheading Example
33778 -info-ada-exceptions aint
33779 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
33780 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
33781 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
33782 body=[@{name="constraint_error",address="0x0000000000613da0"@},
33783 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
33786 @subheading Catching Ada Exceptions
33788 The commands describing how to ask @value{GDBN} to stop when a program
33789 raises an exception are described at @ref{Ada Exception GDB/MI
33790 Catchpoint Commands}.
33793 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33794 @node GDB/MI Support Commands
33795 @section @sc{gdb/mi} Support Commands
33797 Since new commands and features get regularly added to @sc{gdb/mi},
33798 some commands are available to help front-ends query the debugger
33799 about support for these capabilities. Similarly, it is also possible
33800 to query @value{GDBN} about target support of certain features.
33802 @subheading The @code{-info-gdb-mi-command} Command
33803 @cindex @code{-info-gdb-mi-command}
33804 @findex -info-gdb-mi-command
33806 @subsubheading Synopsis
33809 -info-gdb-mi-command @var{cmd_name}
33812 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
33814 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
33815 is technically not part of the command name (@pxref{GDB/MI Input
33816 Syntax}), and thus should be omitted in @var{cmd_name}. However,
33817 for ease of use, this command also accepts the form with the leading
33820 @subsubheading @value{GDBN} Command
33822 There is no corresponding @value{GDBN} command.
33824 @subsubheading Result
33826 The result is a tuple. There is currently only one field:
33830 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
33831 @code{"false"} otherwise.
33835 @subsubheading Example
33837 Here is an example where the @sc{gdb/mi} command does not exist:
33840 -info-gdb-mi-command unsupported-command
33841 ^done,command=@{exists="false"@}
33845 And here is an example where the @sc{gdb/mi} command is known
33849 -info-gdb-mi-command symbol-list-lines
33850 ^done,command=@{exists="true"@}
33853 @subheading The @code{-list-features} Command
33854 @findex -list-features
33855 @cindex supported @sc{gdb/mi} features, list
33857 Returns a list of particular features of the MI protocol that
33858 this version of gdb implements. A feature can be a command,
33859 or a new field in an output of some command, or even an
33860 important bugfix. While a frontend can sometimes detect presence
33861 of a feature at runtime, it is easier to perform detection at debugger
33864 The command returns a list of strings, with each string naming an
33865 available feature. Each returned string is just a name, it does not
33866 have any internal structure. The list of possible feature names
33872 (gdb) -list-features
33873 ^done,result=["feature1","feature2"]
33876 The current list of features is:
33879 @item frozen-varobjs
33880 Indicates support for the @code{-var-set-frozen} command, as well
33881 as possible presense of the @code{frozen} field in the output
33882 of @code{-varobj-create}.
33883 @item pending-breakpoints
33884 Indicates support for the @option{-f} option to the @code{-break-insert}
33887 Indicates Python scripting support, Python-based
33888 pretty-printing commands, and possible presence of the
33889 @samp{display_hint} field in the output of @code{-var-list-children}
33891 Indicates support for the @code{-thread-info} command.
33892 @item data-read-memory-bytes
33893 Indicates support for the @code{-data-read-memory-bytes} and the
33894 @code{-data-write-memory-bytes} commands.
33895 @item breakpoint-notifications
33896 Indicates that changes to breakpoints and breakpoints created via the
33897 CLI will be announced via async records.
33898 @item ada-task-info
33899 Indicates support for the @code{-ada-task-info} command.
33900 @item language-option
33901 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
33902 option (@pxref{Context management}).
33903 @item info-gdb-mi-command
33904 Indicates support for the @code{-info-gdb-mi-command} command.
33905 @item undefined-command-error-code
33906 Indicates support for the "undefined-command" error code in error result
33907 records, produced when trying to execute an undefined @sc{gdb/mi} command
33908 (@pxref{GDB/MI Result Records}).
33909 @item exec-run-start-option
33910 Indicates that the @code{-exec-run} command supports the @option{--start}
33911 option (@pxref{GDB/MI Program Execution}).
33912 @item data-disassemble-a-option
33913 Indicates that the @code{-data-disassemble} command supports the @option{-a}
33914 option (@pxref{GDB/MI Data Manipulation}).
33917 @subheading The @code{-list-target-features} Command
33918 @findex -list-target-features
33920 Returns a list of particular features that are supported by the
33921 target. Those features affect the permitted MI commands, but
33922 unlike the features reported by the @code{-list-features} command, the
33923 features depend on which target GDB is using at the moment. Whenever
33924 a target can change, due to commands such as @code{-target-select},
33925 @code{-target-attach} or @code{-exec-run}, the list of target features
33926 may change, and the frontend should obtain it again.
33930 (gdb) -list-target-features
33931 ^done,result=["async"]
33934 The current list of features is:
33938 Indicates that the target is capable of asynchronous command
33939 execution, which means that @value{GDBN} will accept further commands
33940 while the target is running.
33943 Indicates that the target is capable of reverse execution.
33944 @xref{Reverse Execution}, for more information.
33948 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33949 @node GDB/MI Miscellaneous Commands
33950 @section Miscellaneous @sc{gdb/mi} Commands
33952 @c @subheading -gdb-complete
33954 @subheading The @code{-gdb-exit} Command
33957 @subsubheading Synopsis
33963 Exit @value{GDBN} immediately.
33965 @subsubheading @value{GDBN} Command
33967 Approximately corresponds to @samp{quit}.
33969 @subsubheading Example
33979 @subheading The @code{-exec-abort} Command
33980 @findex -exec-abort
33982 @subsubheading Synopsis
33988 Kill the inferior running program.
33990 @subsubheading @value{GDBN} Command
33992 The corresponding @value{GDBN} command is @samp{kill}.
33994 @subsubheading Example
33999 @subheading The @code{-gdb-set} Command
34002 @subsubheading Synopsis
34008 Set an internal @value{GDBN} variable.
34009 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
34011 @subsubheading @value{GDBN} Command
34013 The corresponding @value{GDBN} command is @samp{set}.
34015 @subsubheading Example
34025 @subheading The @code{-gdb-show} Command
34028 @subsubheading Synopsis
34034 Show the current value of a @value{GDBN} variable.
34036 @subsubheading @value{GDBN} Command
34038 The corresponding @value{GDBN} command is @samp{show}.
34040 @subsubheading Example
34049 @c @subheading -gdb-source
34052 @subheading The @code{-gdb-version} Command
34053 @findex -gdb-version
34055 @subsubheading Synopsis
34061 Show version information for @value{GDBN}. Used mostly in testing.
34063 @subsubheading @value{GDBN} Command
34065 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
34066 default shows this information when you start an interactive session.
34068 @subsubheading Example
34070 @c This example modifies the actual output from GDB to avoid overfull
34076 ~Copyright 2000 Free Software Foundation, Inc.
34077 ~GDB is free software, covered by the GNU General Public License, and
34078 ~you are welcome to change it and/or distribute copies of it under
34079 ~ certain conditions.
34080 ~Type "show copying" to see the conditions.
34081 ~There is absolutely no warranty for GDB. Type "show warranty" for
34083 ~This GDB was configured as
34084 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
34089 @subheading The @code{-list-thread-groups} Command
34090 @findex -list-thread-groups
34092 @subheading Synopsis
34095 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
34098 Lists thread groups (@pxref{Thread groups}). When a single thread
34099 group is passed as the argument, lists the children of that group.
34100 When several thread group are passed, lists information about those
34101 thread groups. Without any parameters, lists information about all
34102 top-level thread groups.
34104 Normally, thread groups that are being debugged are reported.
34105 With the @samp{--available} option, @value{GDBN} reports thread groups
34106 available on the target.
34108 The output of this command may have either a @samp{threads} result or
34109 a @samp{groups} result. The @samp{thread} result has a list of tuples
34110 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
34111 Information}). The @samp{groups} result has a list of tuples as value,
34112 each tuple describing a thread group. If top-level groups are
34113 requested (that is, no parameter is passed), or when several groups
34114 are passed, the output always has a @samp{groups} result. The format
34115 of the @samp{group} result is described below.
34117 To reduce the number of roundtrips it's possible to list thread groups
34118 together with their children, by passing the @samp{--recurse} option
34119 and the recursion depth. Presently, only recursion depth of 1 is
34120 permitted. If this option is present, then every reported thread group
34121 will also include its children, either as @samp{group} or
34122 @samp{threads} field.
34124 In general, any combination of option and parameters is permitted, with
34125 the following caveats:
34129 When a single thread group is passed, the output will typically
34130 be the @samp{threads} result. Because threads may not contain
34131 anything, the @samp{recurse} option will be ignored.
34134 When the @samp{--available} option is passed, limited information may
34135 be available. In particular, the list of threads of a process might
34136 be inaccessible. Further, specifying specific thread groups might
34137 not give any performance advantage over listing all thread groups.
34138 The frontend should assume that @samp{-list-thread-groups --available}
34139 is always an expensive operation and cache the results.
34143 The @samp{groups} result is a list of tuples, where each tuple may
34144 have the following fields:
34148 Identifier of the thread group. This field is always present.
34149 The identifier is an opaque string; frontends should not try to
34150 convert it to an integer, even though it might look like one.
34153 The type of the thread group. At present, only @samp{process} is a
34157 The target-specific process identifier. This field is only present
34158 for thread groups of type @samp{process} and only if the process exists.
34161 The exit code of this group's last exited thread, formatted in octal.
34162 This field is only present for thread groups of type @samp{process} and
34163 only if the process is not running.
34166 The number of children this thread group has. This field may be
34167 absent for an available thread group.
34170 This field has a list of tuples as value, each tuple describing a
34171 thread. It may be present if the @samp{--recurse} option is
34172 specified, and it's actually possible to obtain the threads.
34175 This field is a list of integers, each identifying a core that one
34176 thread of the group is running on. This field may be absent if
34177 such information is not available.
34180 The name of the executable file that corresponds to this thread group.
34181 The field is only present for thread groups of type @samp{process},
34182 and only if there is a corresponding executable file.
34186 @subheading Example
34190 -list-thread-groups
34191 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
34192 -list-thread-groups 17
34193 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
34194 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
34195 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
34196 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
34197 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
34198 -list-thread-groups --available
34199 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
34200 -list-thread-groups --available --recurse 1
34201 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34202 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34203 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
34204 -list-thread-groups --available --recurse 1 17 18
34205 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34206 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34207 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
34210 @subheading The @code{-info-os} Command
34213 @subsubheading Synopsis
34216 -info-os [ @var{type} ]
34219 If no argument is supplied, the command returns a table of available
34220 operating-system-specific information types. If one of these types is
34221 supplied as an argument @var{type}, then the command returns a table
34222 of data of that type.
34224 The types of information available depend on the target operating
34227 @subsubheading @value{GDBN} Command
34229 The corresponding @value{GDBN} command is @samp{info os}.
34231 @subsubheading Example
34233 When run on a @sc{gnu}/Linux system, the output will look something
34239 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
34240 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
34241 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
34242 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
34243 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
34245 item=@{col0="files",col1="Listing of all file descriptors",
34246 col2="File descriptors"@},
34247 item=@{col0="modules",col1="Listing of all loaded kernel modules",
34248 col2="Kernel modules"@},
34249 item=@{col0="msg",col1="Listing of all message queues",
34250 col2="Message queues"@},
34251 item=@{col0="processes",col1="Listing of all processes",
34252 col2="Processes"@},
34253 item=@{col0="procgroups",col1="Listing of all process groups",
34254 col2="Process groups"@},
34255 item=@{col0="semaphores",col1="Listing of all semaphores",
34256 col2="Semaphores"@},
34257 item=@{col0="shm",col1="Listing of all shared-memory regions",
34258 col2="Shared-memory regions"@},
34259 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
34261 item=@{col0="threads",col1="Listing of all threads",
34265 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
34266 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
34267 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
34268 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
34269 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
34270 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
34271 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
34272 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
34274 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
34275 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
34279 (Note that the MI output here includes a @code{"Title"} column that
34280 does not appear in command-line @code{info os}; this column is useful
34281 for MI clients that want to enumerate the types of data, such as in a
34282 popup menu, but is needless clutter on the command line, and
34283 @code{info os} omits it.)
34285 @subheading The @code{-add-inferior} Command
34286 @findex -add-inferior
34288 @subheading Synopsis
34294 Creates a new inferior (@pxref{Inferiors and Programs}). The created
34295 inferior is not associated with any executable. Such association may
34296 be established with the @samp{-file-exec-and-symbols} command
34297 (@pxref{GDB/MI File Commands}). The command response has a single
34298 field, @samp{inferior}, whose value is the identifier of the
34299 thread group corresponding to the new inferior.
34301 @subheading Example
34306 ^done,inferior="i3"
34309 @subheading The @code{-interpreter-exec} Command
34310 @findex -interpreter-exec
34312 @subheading Synopsis
34315 -interpreter-exec @var{interpreter} @var{command}
34317 @anchor{-interpreter-exec}
34319 Execute the specified @var{command} in the given @var{interpreter}.
34321 @subheading @value{GDBN} Command
34323 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
34325 @subheading Example
34329 -interpreter-exec console "break main"
34330 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
34331 &"During symbol reading, bad structure-type format.\n"
34332 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
34337 @subheading The @code{-inferior-tty-set} Command
34338 @findex -inferior-tty-set
34340 @subheading Synopsis
34343 -inferior-tty-set /dev/pts/1
34346 Set terminal for future runs of the program being debugged.
34348 @subheading @value{GDBN} Command
34350 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
34352 @subheading Example
34356 -inferior-tty-set /dev/pts/1
34361 @subheading The @code{-inferior-tty-show} Command
34362 @findex -inferior-tty-show
34364 @subheading Synopsis
34370 Show terminal for future runs of program being debugged.
34372 @subheading @value{GDBN} Command
34374 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
34376 @subheading Example
34380 -inferior-tty-set /dev/pts/1
34384 ^done,inferior_tty_terminal="/dev/pts/1"
34388 @subheading The @code{-enable-timings} Command
34389 @findex -enable-timings
34391 @subheading Synopsis
34394 -enable-timings [yes | no]
34397 Toggle the printing of the wallclock, user and system times for an MI
34398 command as a field in its output. This command is to help frontend
34399 developers optimize the performance of their code. No argument is
34400 equivalent to @samp{yes}.
34402 @subheading @value{GDBN} Command
34406 @subheading Example
34414 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
34415 addr="0x080484ed",func="main",file="myprog.c",
34416 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
34418 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
34426 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
34427 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
34428 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
34429 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
34434 @chapter @value{GDBN} Annotations
34436 This chapter describes annotations in @value{GDBN}. Annotations were
34437 designed to interface @value{GDBN} to graphical user interfaces or other
34438 similar programs which want to interact with @value{GDBN} at a
34439 relatively high level.
34441 The annotation mechanism has largely been superseded by @sc{gdb/mi}
34445 This is Edition @value{EDITION}, @value{DATE}.
34449 * Annotations Overview:: What annotations are; the general syntax.
34450 * Server Prefix:: Issuing a command without affecting user state.
34451 * Prompting:: Annotations marking @value{GDBN}'s need for input.
34452 * Errors:: Annotations for error messages.
34453 * Invalidation:: Some annotations describe things now invalid.
34454 * Annotations for Running::
34455 Whether the program is running, how it stopped, etc.
34456 * Source Annotations:: Annotations describing source code.
34459 @node Annotations Overview
34460 @section What is an Annotation?
34461 @cindex annotations
34463 Annotations start with a newline character, two @samp{control-z}
34464 characters, and the name of the annotation. If there is no additional
34465 information associated with this annotation, the name of the annotation
34466 is followed immediately by a newline. If there is additional
34467 information, the name of the annotation is followed by a space, the
34468 additional information, and a newline. The additional information
34469 cannot contain newline characters.
34471 Any output not beginning with a newline and two @samp{control-z}
34472 characters denotes literal output from @value{GDBN}. Currently there is
34473 no need for @value{GDBN} to output a newline followed by two
34474 @samp{control-z} characters, but if there was such a need, the
34475 annotations could be extended with an @samp{escape} annotation which
34476 means those three characters as output.
34478 The annotation @var{level}, which is specified using the
34479 @option{--annotate} command line option (@pxref{Mode Options}), controls
34480 how much information @value{GDBN} prints together with its prompt,
34481 values of expressions, source lines, and other types of output. Level 0
34482 is for no annotations, level 1 is for use when @value{GDBN} is run as a
34483 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
34484 for programs that control @value{GDBN}, and level 2 annotations have
34485 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
34486 Interface, annotate, GDB's Obsolete Annotations}).
34489 @kindex set annotate
34490 @item set annotate @var{level}
34491 The @value{GDBN} command @code{set annotate} sets the level of
34492 annotations to the specified @var{level}.
34494 @item show annotate
34495 @kindex show annotate
34496 Show the current annotation level.
34499 This chapter describes level 3 annotations.
34501 A simple example of starting up @value{GDBN} with annotations is:
34504 $ @kbd{gdb --annotate=3}
34506 Copyright 2003 Free Software Foundation, Inc.
34507 GDB is free software, covered by the GNU General Public License,
34508 and you are welcome to change it and/or distribute copies of it
34509 under certain conditions.
34510 Type "show copying" to see the conditions.
34511 There is absolutely no warranty for GDB. Type "show warranty"
34513 This GDB was configured as "i386-pc-linux-gnu"
34524 Here @samp{quit} is input to @value{GDBN}; the rest is output from
34525 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
34526 denotes a @samp{control-z} character) are annotations; the rest is
34527 output from @value{GDBN}.
34529 @node Server Prefix
34530 @section The Server Prefix
34531 @cindex server prefix
34533 If you prefix a command with @samp{server } then it will not affect
34534 the command history, nor will it affect @value{GDBN}'s notion of which
34535 command to repeat if @key{RET} is pressed on a line by itself. This
34536 means that commands can be run behind a user's back by a front-end in
34537 a transparent manner.
34539 The @code{server } prefix does not affect the recording of values into
34540 the value history; to print a value without recording it into the
34541 value history, use the @code{output} command instead of the
34542 @code{print} command.
34544 Using this prefix also disables confirmation requests
34545 (@pxref{confirmation requests}).
34548 @section Annotation for @value{GDBN} Input
34550 @cindex annotations for prompts
34551 When @value{GDBN} prompts for input, it annotates this fact so it is possible
34552 to know when to send output, when the output from a given command is
34555 Different kinds of input each have a different @dfn{input type}. Each
34556 input type has three annotations: a @code{pre-} annotation, which
34557 denotes the beginning of any prompt which is being output, a plain
34558 annotation, which denotes the end of the prompt, and then a @code{post-}
34559 annotation which denotes the end of any echo which may (or may not) be
34560 associated with the input. For example, the @code{prompt} input type
34561 features the following annotations:
34569 The input types are
34572 @findex pre-prompt annotation
34573 @findex prompt annotation
34574 @findex post-prompt annotation
34576 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
34578 @findex pre-commands annotation
34579 @findex commands annotation
34580 @findex post-commands annotation
34582 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
34583 command. The annotations are repeated for each command which is input.
34585 @findex pre-overload-choice annotation
34586 @findex overload-choice annotation
34587 @findex post-overload-choice annotation
34588 @item overload-choice
34589 When @value{GDBN} wants the user to select between various overloaded functions.
34591 @findex pre-query annotation
34592 @findex query annotation
34593 @findex post-query annotation
34595 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
34597 @findex pre-prompt-for-continue annotation
34598 @findex prompt-for-continue annotation
34599 @findex post-prompt-for-continue annotation
34600 @item prompt-for-continue
34601 When @value{GDBN} is asking the user to press return to continue. Note: Don't
34602 expect this to work well; instead use @code{set height 0} to disable
34603 prompting. This is because the counting of lines is buggy in the
34604 presence of annotations.
34609 @cindex annotations for errors, warnings and interrupts
34611 @findex quit annotation
34616 This annotation occurs right before @value{GDBN} responds to an interrupt.
34618 @findex error annotation
34623 This annotation occurs right before @value{GDBN} responds to an error.
34625 Quit and error annotations indicate that any annotations which @value{GDBN} was
34626 in the middle of may end abruptly. For example, if a
34627 @code{value-history-begin} annotation is followed by a @code{error}, one
34628 cannot expect to receive the matching @code{value-history-end}. One
34629 cannot expect not to receive it either, however; an error annotation
34630 does not necessarily mean that @value{GDBN} is immediately returning all the way
34633 @findex error-begin annotation
34634 A quit or error annotation may be preceded by
34640 Any output between that and the quit or error annotation is the error
34643 Warning messages are not yet annotated.
34644 @c If we want to change that, need to fix warning(), type_error(),
34645 @c range_error(), and possibly other places.
34648 @section Invalidation Notices
34650 @cindex annotations for invalidation messages
34651 The following annotations say that certain pieces of state may have
34655 @findex frames-invalid annotation
34656 @item ^Z^Zframes-invalid
34658 The frames (for example, output from the @code{backtrace} command) may
34661 @findex breakpoints-invalid annotation
34662 @item ^Z^Zbreakpoints-invalid
34664 The breakpoints may have changed. For example, the user just added or
34665 deleted a breakpoint.
34668 @node Annotations for Running
34669 @section Running the Program
34670 @cindex annotations for running programs
34672 @findex starting annotation
34673 @findex stopping annotation
34674 When the program starts executing due to a @value{GDBN} command such as
34675 @code{step} or @code{continue},
34681 is output. When the program stops,
34687 is output. Before the @code{stopped} annotation, a variety of
34688 annotations describe how the program stopped.
34691 @findex exited annotation
34692 @item ^Z^Zexited @var{exit-status}
34693 The program exited, and @var{exit-status} is the exit status (zero for
34694 successful exit, otherwise nonzero).
34696 @findex signalled annotation
34697 @findex signal-name annotation
34698 @findex signal-name-end annotation
34699 @findex signal-string annotation
34700 @findex signal-string-end annotation
34701 @item ^Z^Zsignalled
34702 The program exited with a signal. After the @code{^Z^Zsignalled}, the
34703 annotation continues:
34709 ^Z^Zsignal-name-end
34713 ^Z^Zsignal-string-end
34718 where @var{name} is the name of the signal, such as @code{SIGILL} or
34719 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
34720 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
34721 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
34722 user's benefit and have no particular format.
34724 @findex signal annotation
34726 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
34727 just saying that the program received the signal, not that it was
34728 terminated with it.
34730 @findex breakpoint annotation
34731 @item ^Z^Zbreakpoint @var{number}
34732 The program hit breakpoint number @var{number}.
34734 @findex watchpoint annotation
34735 @item ^Z^Zwatchpoint @var{number}
34736 The program hit watchpoint number @var{number}.
34739 @node Source Annotations
34740 @section Displaying Source
34741 @cindex annotations for source display
34743 @findex source annotation
34744 The following annotation is used instead of displaying source code:
34747 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
34750 where @var{filename} is an absolute file name indicating which source
34751 file, @var{line} is the line number within that file (where 1 is the
34752 first line in the file), @var{character} is the character position
34753 within the file (where 0 is the first character in the file) (for most
34754 debug formats this will necessarily point to the beginning of a line),
34755 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
34756 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
34757 @var{addr} is the address in the target program associated with the
34758 source which is being displayed. The @var{addr} is in the form @samp{0x}
34759 followed by one or more lowercase hex digits (note that this does not
34760 depend on the language).
34762 @node JIT Interface
34763 @chapter JIT Compilation Interface
34764 @cindex just-in-time compilation
34765 @cindex JIT compilation interface
34767 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
34768 interface. A JIT compiler is a program or library that generates native
34769 executable code at runtime and executes it, usually in order to achieve good
34770 performance while maintaining platform independence.
34772 Programs that use JIT compilation are normally difficult to debug because
34773 portions of their code are generated at runtime, instead of being loaded from
34774 object files, which is where @value{GDBN} normally finds the program's symbols
34775 and debug information. In order to debug programs that use JIT compilation,
34776 @value{GDBN} has an interface that allows the program to register in-memory
34777 symbol files with @value{GDBN} at runtime.
34779 If you are using @value{GDBN} to debug a program that uses this interface, then
34780 it should work transparently so long as you have not stripped the binary. If
34781 you are developing a JIT compiler, then the interface is documented in the rest
34782 of this chapter. At this time, the only known client of this interface is the
34785 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
34786 JIT compiler communicates with @value{GDBN} by writing data into a global
34787 variable and calling a fuction at a well-known symbol. When @value{GDBN}
34788 attaches, it reads a linked list of symbol files from the global variable to
34789 find existing code, and puts a breakpoint in the function so that it can find
34790 out about additional code.
34793 * Declarations:: Relevant C struct declarations
34794 * Registering Code:: Steps to register code
34795 * Unregistering Code:: Steps to unregister code
34796 * Custom Debug Info:: Emit debug information in a custom format
34800 @section JIT Declarations
34802 These are the relevant struct declarations that a C program should include to
34803 implement the interface:
34813 struct jit_code_entry
34815 struct jit_code_entry *next_entry;
34816 struct jit_code_entry *prev_entry;
34817 const char *symfile_addr;
34818 uint64_t symfile_size;
34821 struct jit_descriptor
34824 /* This type should be jit_actions_t, but we use uint32_t
34825 to be explicit about the bitwidth. */
34826 uint32_t action_flag;
34827 struct jit_code_entry *relevant_entry;
34828 struct jit_code_entry *first_entry;
34831 /* GDB puts a breakpoint in this function. */
34832 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34834 /* Make sure to specify the version statically, because the
34835 debugger may check the version before we can set it. */
34836 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34839 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34840 modifications to this global data properly, which can easily be done by putting
34841 a global mutex around modifications to these structures.
34843 @node Registering Code
34844 @section Registering Code
34846 To register code with @value{GDBN}, the JIT should follow this protocol:
34850 Generate an object file in memory with symbols and other desired debug
34851 information. The file must include the virtual addresses of the sections.
34854 Create a code entry for the file, which gives the start and size of the symbol
34858 Add it to the linked list in the JIT descriptor.
34861 Point the relevant_entry field of the descriptor at the entry.
34864 Set @code{action_flag} to @code{JIT_REGISTER} and call
34865 @code{__jit_debug_register_code}.
34868 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34869 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34870 new code. However, the linked list must still be maintained in order to allow
34871 @value{GDBN} to attach to a running process and still find the symbol files.
34873 @node Unregistering Code
34874 @section Unregistering Code
34876 If code is freed, then the JIT should use the following protocol:
34880 Remove the code entry corresponding to the code from the linked list.
34883 Point the @code{relevant_entry} field of the descriptor at the code entry.
34886 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34887 @code{__jit_debug_register_code}.
34890 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34891 and the JIT will leak the memory used for the associated symbol files.
34893 @node Custom Debug Info
34894 @section Custom Debug Info
34895 @cindex custom JIT debug info
34896 @cindex JIT debug info reader
34898 Generating debug information in platform-native file formats (like ELF
34899 or COFF) may be an overkill for JIT compilers; especially if all the
34900 debug info is used for is displaying a meaningful backtrace. The
34901 issue can be resolved by having the JIT writers decide on a debug info
34902 format and also provide a reader that parses the debug info generated
34903 by the JIT compiler. This section gives a brief overview on writing
34904 such a parser. More specific details can be found in the source file
34905 @file{gdb/jit-reader.in}, which is also installed as a header at
34906 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34908 The reader is implemented as a shared object (so this functionality is
34909 not available on platforms which don't allow loading shared objects at
34910 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34911 @code{jit-reader-unload} are provided, to be used to load and unload
34912 the readers from a preconfigured directory. Once loaded, the shared
34913 object is used the parse the debug information emitted by the JIT
34917 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34918 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34921 @node Using JIT Debug Info Readers
34922 @subsection Using JIT Debug Info Readers
34923 @kindex jit-reader-load
34924 @kindex jit-reader-unload
34926 Readers can be loaded and unloaded using the @code{jit-reader-load}
34927 and @code{jit-reader-unload} commands.
34930 @item jit-reader-load @var{reader}
34931 Load the JIT reader named @var{reader}, which is a shared
34932 object specified as either an absolute or a relative file name. In
34933 the latter case, @value{GDBN} will try to load the reader from a
34934 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34935 system (here @var{libdir} is the system library directory, often
34936 @file{/usr/local/lib}).
34938 Only one reader can be active at a time; trying to load a second
34939 reader when one is already loaded will result in @value{GDBN}
34940 reporting an error. A new JIT reader can be loaded by first unloading
34941 the current one using @code{jit-reader-unload} and then invoking
34942 @code{jit-reader-load}.
34944 @item jit-reader-unload
34945 Unload the currently loaded JIT reader.
34949 @node Writing JIT Debug Info Readers
34950 @subsection Writing JIT Debug Info Readers
34951 @cindex writing JIT debug info readers
34953 As mentioned, a reader is essentially a shared object conforming to a
34954 certain ABI. This ABI is described in @file{jit-reader.h}.
34956 @file{jit-reader.h} defines the structures, macros and functions
34957 required to write a reader. It is installed (along with
34958 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34959 the system include directory.
34961 Readers need to be released under a GPL compatible license. A reader
34962 can be declared as released under such a license by placing the macro
34963 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34965 The entry point for readers is the symbol @code{gdb_init_reader},
34966 which is expected to be a function with the prototype
34968 @findex gdb_init_reader
34970 extern struct gdb_reader_funcs *gdb_init_reader (void);
34973 @cindex @code{struct gdb_reader_funcs}
34975 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34976 functions. These functions are executed to read the debug info
34977 generated by the JIT compiler (@code{read}), to unwind stack frames
34978 (@code{unwind}) and to create canonical frame IDs
34979 (@code{get_Frame_id}). It also has a callback that is called when the
34980 reader is being unloaded (@code{destroy}). The struct looks like this
34983 struct gdb_reader_funcs
34985 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34986 int reader_version;
34988 /* For use by the reader. */
34991 gdb_read_debug_info *read;
34992 gdb_unwind_frame *unwind;
34993 gdb_get_frame_id *get_frame_id;
34994 gdb_destroy_reader *destroy;
34998 @cindex @code{struct gdb_symbol_callbacks}
34999 @cindex @code{struct gdb_unwind_callbacks}
35001 The callbacks are provided with another set of callbacks by
35002 @value{GDBN} to do their job. For @code{read}, these callbacks are
35003 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
35004 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
35005 @code{struct gdb_symbol_callbacks} has callbacks to create new object
35006 files and new symbol tables inside those object files. @code{struct
35007 gdb_unwind_callbacks} has callbacks to read registers off the current
35008 frame and to write out the values of the registers in the previous
35009 frame. Both have a callback (@code{target_read}) to read bytes off the
35010 target's address space.
35012 @node In-Process Agent
35013 @chapter In-Process Agent
35014 @cindex debugging agent
35015 The traditional debugging model is conceptually low-speed, but works fine,
35016 because most bugs can be reproduced in debugging-mode execution. However,
35017 as multi-core or many-core processors are becoming mainstream, and
35018 multi-threaded programs become more and more popular, there should be more
35019 and more bugs that only manifest themselves at normal-mode execution, for
35020 example, thread races, because debugger's interference with the program's
35021 timing may conceal the bugs. On the other hand, in some applications,
35022 it is not feasible for the debugger to interrupt the program's execution
35023 long enough for the developer to learn anything helpful about its behavior.
35024 If the program's correctness depends on its real-time behavior, delays
35025 introduced by a debugger might cause the program to fail, even when the
35026 code itself is correct. It is useful to be able to observe the program's
35027 behavior without interrupting it.
35029 Therefore, traditional debugging model is too intrusive to reproduce
35030 some bugs. In order to reduce the interference with the program, we can
35031 reduce the number of operations performed by debugger. The
35032 @dfn{In-Process Agent}, a shared library, is running within the same
35033 process with inferior, and is able to perform some debugging operations
35034 itself. As a result, debugger is only involved when necessary, and
35035 performance of debugging can be improved accordingly. Note that
35036 interference with program can be reduced but can't be removed completely,
35037 because the in-process agent will still stop or slow down the program.
35039 The in-process agent can interpret and execute Agent Expressions
35040 (@pxref{Agent Expressions}) during performing debugging operations. The
35041 agent expressions can be used for different purposes, such as collecting
35042 data in tracepoints, and condition evaluation in breakpoints.
35044 @anchor{Control Agent}
35045 You can control whether the in-process agent is used as an aid for
35046 debugging with the following commands:
35049 @kindex set agent on
35051 Causes the in-process agent to perform some operations on behalf of the
35052 debugger. Just which operations requested by the user will be done
35053 by the in-process agent depends on the its capabilities. For example,
35054 if you request to evaluate breakpoint conditions in the in-process agent,
35055 and the in-process agent has such capability as well, then breakpoint
35056 conditions will be evaluated in the in-process agent.
35058 @kindex set agent off
35059 @item set agent off
35060 Disables execution of debugging operations by the in-process agent. All
35061 of the operations will be performed by @value{GDBN}.
35065 Display the current setting of execution of debugging operations by
35066 the in-process agent.
35070 * In-Process Agent Protocol::
35073 @node In-Process Agent Protocol
35074 @section In-Process Agent Protocol
35075 @cindex in-process agent protocol
35077 The in-process agent is able to communicate with both @value{GDBN} and
35078 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
35079 used for communications between @value{GDBN} or GDBserver and the IPA.
35080 In general, @value{GDBN} or GDBserver sends commands
35081 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
35082 in-process agent replies back with the return result of the command, or
35083 some other information. The data sent to in-process agent is composed
35084 of primitive data types, such as 4-byte or 8-byte type, and composite
35085 types, which are called objects (@pxref{IPA Protocol Objects}).
35088 * IPA Protocol Objects::
35089 * IPA Protocol Commands::
35092 @node IPA Protocol Objects
35093 @subsection IPA Protocol Objects
35094 @cindex ipa protocol objects
35096 The commands sent to and results received from agent may contain some
35097 complex data types called @dfn{objects}.
35099 The in-process agent is running on the same machine with @value{GDBN}
35100 or GDBserver, so it doesn't have to handle as much differences between
35101 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
35102 However, there are still some differences of two ends in two processes:
35106 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
35107 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
35109 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
35110 GDBserver is compiled with one, and in-process agent is compiled with
35114 Here are the IPA Protocol Objects:
35118 agent expression object. It represents an agent expression
35119 (@pxref{Agent Expressions}).
35120 @anchor{agent expression object}
35122 tracepoint action object. It represents a tracepoint action
35123 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
35124 memory, static trace data and to evaluate expression.
35125 @anchor{tracepoint action object}
35127 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
35128 @anchor{tracepoint object}
35132 The following table describes important attributes of each IPA protocol
35135 @multitable @columnfractions .30 .20 .50
35136 @headitem Name @tab Size @tab Description
35137 @item @emph{agent expression object} @tab @tab
35138 @item length @tab 4 @tab length of bytes code
35139 @item byte code @tab @var{length} @tab contents of byte code
35140 @item @emph{tracepoint action for collecting memory} @tab @tab
35141 @item 'M' @tab 1 @tab type of tracepoint action
35142 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
35143 address of the lowest byte to collect, otherwise @var{addr} is the offset
35144 of @var{basereg} for memory collecting.
35145 @item len @tab 8 @tab length of memory for collecting
35146 @item basereg @tab 4 @tab the register number containing the starting
35147 memory address for collecting.
35148 @item @emph{tracepoint action for collecting registers} @tab @tab
35149 @item 'R' @tab 1 @tab type of tracepoint action
35150 @item @emph{tracepoint action for collecting static trace data} @tab @tab
35151 @item 'L' @tab 1 @tab type of tracepoint action
35152 @item @emph{tracepoint action for expression evaluation} @tab @tab
35153 @item 'X' @tab 1 @tab type of tracepoint action
35154 @item agent expression @tab length of @tab @ref{agent expression object}
35155 @item @emph{tracepoint object} @tab @tab
35156 @item number @tab 4 @tab number of tracepoint
35157 @item address @tab 8 @tab address of tracepoint inserted on
35158 @item type @tab 4 @tab type of tracepoint
35159 @item enabled @tab 1 @tab enable or disable of tracepoint
35160 @item step_count @tab 8 @tab step
35161 @item pass_count @tab 8 @tab pass
35162 @item numactions @tab 4 @tab number of tracepoint actions
35163 @item hit count @tab 8 @tab hit count
35164 @item trace frame usage @tab 8 @tab trace frame usage
35165 @item compiled_cond @tab 8 @tab compiled condition
35166 @item orig_size @tab 8 @tab orig size
35167 @item condition @tab 4 if condition is NULL otherwise length of
35168 @ref{agent expression object}
35169 @tab zero if condition is NULL, otherwise is
35170 @ref{agent expression object}
35171 @item actions @tab variable
35172 @tab numactions number of @ref{tracepoint action object}
35175 @node IPA Protocol Commands
35176 @subsection IPA Protocol Commands
35177 @cindex ipa protocol commands
35179 The spaces in each command are delimiters to ease reading this commands
35180 specification. They don't exist in real commands.
35184 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
35185 Installs a new fast tracepoint described by @var{tracepoint_object}
35186 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
35187 head of @dfn{jumppad}, which is used to jump to data collection routine
35192 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
35193 @var{target_address} is address of tracepoint in the inferior.
35194 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
35195 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
35196 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
35197 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
35204 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
35205 is about to kill inferiors.
35213 @item probe_marker_at:@var{address}
35214 Asks in-process agent to probe the marker at @var{address}.
35221 @item unprobe_marker_at:@var{address}
35222 Asks in-process agent to unprobe the marker at @var{address}.
35226 @chapter Reporting Bugs in @value{GDBN}
35227 @cindex bugs in @value{GDBN}
35228 @cindex reporting bugs in @value{GDBN}
35230 Your bug reports play an essential role in making @value{GDBN} reliable.
35232 Reporting a bug may help you by bringing a solution to your problem, or it
35233 may not. But in any case the principal function of a bug report is to help
35234 the entire community by making the next version of @value{GDBN} work better. Bug
35235 reports are your contribution to the maintenance of @value{GDBN}.
35237 In order for a bug report to serve its purpose, you must include the
35238 information that enables us to fix the bug.
35241 * Bug Criteria:: Have you found a bug?
35242 * Bug Reporting:: How to report bugs
35246 @section Have You Found a Bug?
35247 @cindex bug criteria
35249 If you are not sure whether you have found a bug, here are some guidelines:
35252 @cindex fatal signal
35253 @cindex debugger crash
35254 @cindex crash of debugger
35256 If the debugger gets a fatal signal, for any input whatever, that is a
35257 @value{GDBN} bug. Reliable debuggers never crash.
35259 @cindex error on valid input
35261 If @value{GDBN} produces an error message for valid input, that is a
35262 bug. (Note that if you're cross debugging, the problem may also be
35263 somewhere in the connection to the target.)
35265 @cindex invalid input
35267 If @value{GDBN} does not produce an error message for invalid input,
35268 that is a bug. However, you should note that your idea of
35269 ``invalid input'' might be our idea of ``an extension'' or ``support
35270 for traditional practice''.
35273 If you are an experienced user of debugging tools, your suggestions
35274 for improvement of @value{GDBN} are welcome in any case.
35277 @node Bug Reporting
35278 @section How to Report Bugs
35279 @cindex bug reports
35280 @cindex @value{GDBN} bugs, reporting
35282 A number of companies and individuals offer support for @sc{gnu} products.
35283 If you obtained @value{GDBN} from a support organization, we recommend you
35284 contact that organization first.
35286 You can find contact information for many support companies and
35287 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
35289 @c should add a web page ref...
35292 @ifset BUGURL_DEFAULT
35293 In any event, we also recommend that you submit bug reports for
35294 @value{GDBN}. The preferred method is to submit them directly using
35295 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
35296 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
35299 @strong{Do not send bug reports to @samp{info-gdb}, or to
35300 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
35301 not want to receive bug reports. Those that do have arranged to receive
35304 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
35305 serves as a repeater. The mailing list and the newsgroup carry exactly
35306 the same messages. Often people think of posting bug reports to the
35307 newsgroup instead of mailing them. This appears to work, but it has one
35308 problem which can be crucial: a newsgroup posting often lacks a mail
35309 path back to the sender. Thus, if we need to ask for more information,
35310 we may be unable to reach you. For this reason, it is better to send
35311 bug reports to the mailing list.
35313 @ifclear BUGURL_DEFAULT
35314 In any event, we also recommend that you submit bug reports for
35315 @value{GDBN} to @value{BUGURL}.
35319 The fundamental principle of reporting bugs usefully is this:
35320 @strong{report all the facts}. If you are not sure whether to state a
35321 fact or leave it out, state it!
35323 Often people omit facts because they think they know what causes the
35324 problem and assume that some details do not matter. Thus, you might
35325 assume that the name of the variable you use in an example does not matter.
35326 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
35327 stray memory reference which happens to fetch from the location where that
35328 name is stored in memory; perhaps, if the name were different, the contents
35329 of that location would fool the debugger into doing the right thing despite
35330 the bug. Play it safe and give a specific, complete example. That is the
35331 easiest thing for you to do, and the most helpful.
35333 Keep in mind that the purpose of a bug report is to enable us to fix the
35334 bug. It may be that the bug has been reported previously, but neither
35335 you nor we can know that unless your bug report is complete and
35338 Sometimes people give a few sketchy facts and ask, ``Does this ring a
35339 bell?'' Those bug reports are useless, and we urge everyone to
35340 @emph{refuse to respond to them} except to chide the sender to report
35343 To enable us to fix the bug, you should include all these things:
35347 The version of @value{GDBN}. @value{GDBN} announces it if you start
35348 with no arguments; you can also print it at any time using @code{show
35351 Without this, we will not know whether there is any point in looking for
35352 the bug in the current version of @value{GDBN}.
35355 The type of machine you are using, and the operating system name and
35359 The details of the @value{GDBN} build-time configuration.
35360 @value{GDBN} shows these details if you invoke it with the
35361 @option{--configuration} command-line option, or if you type
35362 @code{show configuration} at @value{GDBN}'s prompt.
35365 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
35366 ``@value{GCC}--2.8.1''.
35369 What compiler (and its version) was used to compile the program you are
35370 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
35371 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
35372 to get this information; for other compilers, see the documentation for
35376 The command arguments you gave the compiler to compile your example and
35377 observe the bug. For example, did you use @samp{-O}? To guarantee
35378 you will not omit something important, list them all. A copy of the
35379 Makefile (or the output from make) is sufficient.
35381 If we were to try to guess the arguments, we would probably guess wrong
35382 and then we might not encounter the bug.
35385 A complete input script, and all necessary source files, that will
35389 A description of what behavior you observe that you believe is
35390 incorrect. For example, ``It gets a fatal signal.''
35392 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
35393 will certainly notice it. But if the bug is incorrect output, we might
35394 not notice unless it is glaringly wrong. You might as well not give us
35395 a chance to make a mistake.
35397 Even if the problem you experience is a fatal signal, you should still
35398 say so explicitly. Suppose something strange is going on, such as, your
35399 copy of @value{GDBN} is out of synch, or you have encountered a bug in
35400 the C library on your system. (This has happened!) Your copy might
35401 crash and ours would not. If you told us to expect a crash, then when
35402 ours fails to crash, we would know that the bug was not happening for
35403 us. If you had not told us to expect a crash, then we would not be able
35404 to draw any conclusion from our observations.
35407 @cindex recording a session script
35408 To collect all this information, you can use a session recording program
35409 such as @command{script}, which is available on many Unix systems.
35410 Just run your @value{GDBN} session inside @command{script} and then
35411 include the @file{typescript} file with your bug report.
35413 Another way to record a @value{GDBN} session is to run @value{GDBN}
35414 inside Emacs and then save the entire buffer to a file.
35417 If you wish to suggest changes to the @value{GDBN} source, send us context
35418 diffs. If you even discuss something in the @value{GDBN} source, refer to
35419 it by context, not by line number.
35421 The line numbers in our development sources will not match those in your
35422 sources. Your line numbers would convey no useful information to us.
35426 Here are some things that are not necessary:
35430 A description of the envelope of the bug.
35432 Often people who encounter a bug spend a lot of time investigating
35433 which changes to the input file will make the bug go away and which
35434 changes will not affect it.
35436 This is often time consuming and not very useful, because the way we
35437 will find the bug is by running a single example under the debugger
35438 with breakpoints, not by pure deduction from a series of examples.
35439 We recommend that you save your time for something else.
35441 Of course, if you can find a simpler example to report @emph{instead}
35442 of the original one, that is a convenience for us. Errors in the
35443 output will be easier to spot, running under the debugger will take
35444 less time, and so on.
35446 However, simplification is not vital; if you do not want to do this,
35447 report the bug anyway and send us the entire test case you used.
35450 A patch for the bug.
35452 A patch for the bug does help us if it is a good one. But do not omit
35453 the necessary information, such as the test case, on the assumption that
35454 a patch is all we need. We might see problems with your patch and decide
35455 to fix the problem another way, or we might not understand it at all.
35457 Sometimes with a program as complicated as @value{GDBN} it is very hard to
35458 construct an example that will make the program follow a certain path
35459 through the code. If you do not send us the example, we will not be able
35460 to construct one, so we will not be able to verify that the bug is fixed.
35462 And if we cannot understand what bug you are trying to fix, or why your
35463 patch should be an improvement, we will not install it. A test case will
35464 help us to understand.
35467 A guess about what the bug is or what it depends on.
35469 Such guesses are usually wrong. Even we cannot guess right about such
35470 things without first using the debugger to find the facts.
35473 @c The readline documentation is distributed with the readline code
35474 @c and consists of the two following files:
35477 @c Use -I with makeinfo to point to the appropriate directory,
35478 @c environment var TEXINPUTS with TeX.
35479 @ifclear SYSTEM_READLINE
35480 @include rluser.texi
35481 @include hsuser.texi
35485 @appendix In Memoriam
35487 The @value{GDBN} project mourns the loss of the following long-time
35492 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
35493 to Free Software in general. Outside of @value{GDBN}, he was known in
35494 the Amiga world for his series of Fish Disks, and the GeekGadget project.
35496 @item Michael Snyder
35497 Michael was one of the Global Maintainers of the @value{GDBN} project,
35498 with contributions recorded as early as 1996, until 2011. In addition
35499 to his day to day participation, he was a large driving force behind
35500 adding Reverse Debugging to @value{GDBN}.
35503 Beyond their technical contributions to the project, they were also
35504 enjoyable members of the Free Software Community. We will miss them.
35506 @node Formatting Documentation
35507 @appendix Formatting Documentation
35509 @cindex @value{GDBN} reference card
35510 @cindex reference card
35511 The @value{GDBN} 4 release includes an already-formatted reference card, ready
35512 for printing with PostScript or Ghostscript, in the @file{gdb}
35513 subdirectory of the main source directory@footnote{In
35514 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
35515 release.}. If you can use PostScript or Ghostscript with your printer,
35516 you can print the reference card immediately with @file{refcard.ps}.
35518 The release also includes the source for the reference card. You
35519 can format it, using @TeX{}, by typing:
35525 The @value{GDBN} reference card is designed to print in @dfn{landscape}
35526 mode on US ``letter'' size paper;
35527 that is, on a sheet 11 inches wide by 8.5 inches
35528 high. You will need to specify this form of printing as an option to
35529 your @sc{dvi} output program.
35531 @cindex documentation
35533 All the documentation for @value{GDBN} comes as part of the machine-readable
35534 distribution. The documentation is written in Texinfo format, which is
35535 a documentation system that uses a single source file to produce both
35536 on-line information and a printed manual. You can use one of the Info
35537 formatting commands to create the on-line version of the documentation
35538 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
35540 @value{GDBN} includes an already formatted copy of the on-line Info
35541 version of this manual in the @file{gdb} subdirectory. The main Info
35542 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
35543 subordinate files matching @samp{gdb.info*} in the same directory. If
35544 necessary, you can print out these files, or read them with any editor;
35545 but they are easier to read using the @code{info} subsystem in @sc{gnu}
35546 Emacs or the standalone @code{info} program, available as part of the
35547 @sc{gnu} Texinfo distribution.
35549 If you want to format these Info files yourself, you need one of the
35550 Info formatting programs, such as @code{texinfo-format-buffer} or
35553 If you have @code{makeinfo} installed, and are in the top level
35554 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
35555 version @value{GDBVN}), you can make the Info file by typing:
35562 If you want to typeset and print copies of this manual, you need @TeX{},
35563 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
35564 Texinfo definitions file.
35566 @TeX{} is a typesetting program; it does not print files directly, but
35567 produces output files called @sc{dvi} files. To print a typeset
35568 document, you need a program to print @sc{dvi} files. If your system
35569 has @TeX{} installed, chances are it has such a program. The precise
35570 command to use depends on your system; @kbd{lpr -d} is common; another
35571 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
35572 require a file name without any extension or a @samp{.dvi} extension.
35574 @TeX{} also requires a macro definitions file called
35575 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
35576 written in Texinfo format. On its own, @TeX{} cannot either read or
35577 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
35578 and is located in the @file{gdb-@var{version-number}/texinfo}
35581 If you have @TeX{} and a @sc{dvi} printer program installed, you can
35582 typeset and print this manual. First switch to the @file{gdb}
35583 subdirectory of the main source directory (for example, to
35584 @file{gdb-@value{GDBVN}/gdb}) and type:
35590 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
35592 @node Installing GDB
35593 @appendix Installing @value{GDBN}
35594 @cindex installation
35597 * Requirements:: Requirements for building @value{GDBN}
35598 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
35599 * Separate Objdir:: Compiling @value{GDBN} in another directory
35600 * Config Names:: Specifying names for hosts and targets
35601 * Configure Options:: Summary of options for configure
35602 * System-wide configuration:: Having a system-wide init file
35606 @section Requirements for Building @value{GDBN}
35607 @cindex building @value{GDBN}, requirements for
35609 Building @value{GDBN} requires various tools and packages to be available.
35610 Other packages will be used only if they are found.
35612 @heading Tools/Packages Necessary for Building @value{GDBN}
35614 @item C@t{++}11 compiler
35615 @value{GDBN} is written in C@t{++}11. It should be buildable with any
35616 recent C@t{++}11 compiler, e.g.@: GCC.
35619 @value{GDBN}'s build system relies on features only found in the GNU
35620 make program. Other variants of @code{make} will not work.
35623 @heading Tools/Packages Optional for Building @value{GDBN}
35627 @value{GDBN} can use the Expat XML parsing library. This library may be
35628 included with your operating system distribution; if it is not, you
35629 can get the latest version from @url{http://expat.sourceforge.net}.
35630 The @file{configure} script will search for this library in several
35631 standard locations; if it is installed in an unusual path, you can
35632 use the @option{--with-libexpat-prefix} option to specify its location.
35638 Remote protocol memory maps (@pxref{Memory Map Format})
35640 Target descriptions (@pxref{Target Descriptions})
35642 Remote shared library lists (@xref{Library List Format},
35643 or alternatively @pxref{Library List Format for SVR4 Targets})
35645 MS-Windows shared libraries (@pxref{Shared Libraries})
35647 Traceframe info (@pxref{Traceframe Info Format})
35649 Branch trace (@pxref{Branch Trace Format},
35650 @pxref{Branch Trace Configuration Format})
35654 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
35655 default, @value{GDBN} will be compiled if the Guile libraries are
35656 installed and are found by @file{configure}. You can use the
35657 @code{--with-guile} option to request Guile, and pass either the Guile
35658 version number or the file name of the relevant @code{pkg-config}
35659 program to choose a particular version of Guile.
35662 @value{GDBN}'s features related to character sets (@pxref{Character
35663 Sets}) require a functioning @code{iconv} implementation. If you are
35664 on a GNU system, then this is provided by the GNU C Library. Some
35665 other systems also provide a working @code{iconv}.
35667 If @value{GDBN} is using the @code{iconv} program which is installed
35668 in a non-standard place, you will need to tell @value{GDBN} where to
35669 find it. This is done with @option{--with-iconv-bin} which specifies
35670 the directory that contains the @code{iconv} program. This program is
35671 run in order to make a list of the available character sets.
35673 On systems without @code{iconv}, you can install GNU Libiconv. If
35674 Libiconv is installed in a standard place, @value{GDBN} will
35675 automatically use it if it is needed. If you have previously
35676 installed Libiconv in a non-standard place, you can use the
35677 @option{--with-libiconv-prefix} option to @file{configure}.
35679 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
35680 arrange to build Libiconv if a directory named @file{libiconv} appears
35681 in the top-most source directory. If Libiconv is built this way, and
35682 if the operating system does not provide a suitable @code{iconv}
35683 implementation, then the just-built library will automatically be used
35684 by @value{GDBN}. One easy way to set this up is to download GNU
35685 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
35686 source tree, and then rename the directory holding the Libiconv source
35687 code to @samp{libiconv}.
35690 @value{GDBN} can support debugging sections that are compressed with
35691 the LZMA library. @xref{MiniDebugInfo}. If this library is not
35692 included with your operating system, you can find it in the xz package
35693 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
35694 the usual place, then the @file{configure} script will use it
35695 automatically. If it is installed in an unusual path, you can use the
35696 @option{--with-lzma-prefix} option to specify its location.
35700 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
35701 library. This library may be included with your operating system
35702 distribution; if it is not, you can get the latest version from
35703 @url{http://www.mpfr.org}. The @file{configure} script will search
35704 for this library in several standard locations; if it is installed
35705 in an unusual path, you can use the @option{--with-libmpfr-prefix}
35706 option to specify its location.
35708 GNU MPFR is used to emulate target floating-point arithmetic during
35709 expression evaluation when the target uses different floating-point
35710 formats than the host. If GNU MPFR it is not available, @value{GDBN}
35711 will fall back to using host floating-point arithmetic.
35714 @value{GDBN} can be scripted using Python language. @xref{Python}.
35715 By default, @value{GDBN} will be compiled if the Python libraries are
35716 installed and are found by @file{configure}. You can use the
35717 @code{--with-python} option to request Python, and pass either the
35718 file name of the relevant @code{python} executable, or the name of the
35719 directory in which Python is installed, to choose a particular
35720 installation of Python.
35723 @cindex compressed debug sections
35724 @value{GDBN} will use the @samp{zlib} library, if available, to read
35725 compressed debug sections. Some linkers, such as GNU gold, are capable
35726 of producing binaries with compressed debug sections. If @value{GDBN}
35727 is compiled with @samp{zlib}, it will be able to read the debug
35728 information in such binaries.
35730 The @samp{zlib} library is likely included with your operating system
35731 distribution; if it is not, you can get the latest version from
35732 @url{http://zlib.net}.
35735 @node Running Configure
35736 @section Invoking the @value{GDBN} @file{configure} Script
35737 @cindex configuring @value{GDBN}
35738 @value{GDBN} comes with a @file{configure} script that automates the process
35739 of preparing @value{GDBN} for installation; you can then use @code{make} to
35740 build the @code{gdb} program.
35742 @c irrelevant in info file; it's as current as the code it lives with.
35743 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
35744 look at the @file{README} file in the sources; we may have improved the
35745 installation procedures since publishing this manual.}
35748 The @value{GDBN} distribution includes all the source code you need for
35749 @value{GDBN} in a single directory, whose name is usually composed by
35750 appending the version number to @samp{gdb}.
35752 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
35753 @file{gdb-@value{GDBVN}} directory. That directory contains:
35756 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
35757 script for configuring @value{GDBN} and all its supporting libraries
35759 @item gdb-@value{GDBVN}/gdb
35760 the source specific to @value{GDBN} itself
35762 @item gdb-@value{GDBVN}/bfd
35763 source for the Binary File Descriptor library
35765 @item gdb-@value{GDBVN}/include
35766 @sc{gnu} include files
35768 @item gdb-@value{GDBVN}/libiberty
35769 source for the @samp{-liberty} free software library
35771 @item gdb-@value{GDBVN}/opcodes
35772 source for the library of opcode tables and disassemblers
35774 @item gdb-@value{GDBVN}/readline
35775 source for the @sc{gnu} command-line interface
35778 There may be other subdirectories as well.
35780 The simplest way to configure and build @value{GDBN} is to run @file{configure}
35781 from the @file{gdb-@var{version-number}} source directory, which in
35782 this example is the @file{gdb-@value{GDBVN}} directory.
35784 First switch to the @file{gdb-@var{version-number}} source directory
35785 if you are not already in it; then run @file{configure}. Pass the
35786 identifier for the platform on which @value{GDBN} will run as an
35792 cd gdb-@value{GDBVN}
35797 Running @samp{configure} and then running @code{make} builds the
35798 included supporting libraries, then @code{gdb} itself. The configured
35799 source files, and the binaries, are left in the corresponding source
35803 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
35804 system does not recognize this automatically when you run a different
35805 shell, you may need to run @code{sh} on it explicitly:
35811 You should run the @file{configure} script from the top directory in the
35812 source tree, the @file{gdb-@var{version-number}} directory. If you run
35813 @file{configure} from one of the subdirectories, you will configure only
35814 that subdirectory. That is usually not what you want. In particular,
35815 if you run the first @file{configure} from the @file{gdb} subdirectory
35816 of the @file{gdb-@var{version-number}} directory, you will omit the
35817 configuration of @file{bfd}, @file{readline}, and other sibling
35818 directories of the @file{gdb} subdirectory. This leads to build errors
35819 about missing include files such as @file{bfd/bfd.h}.
35821 You can install @code{@value{GDBN}} anywhere. The best way to do this
35822 is to pass the @code{--prefix} option to @code{configure}, and then
35823 install it with @code{make install}.
35825 @node Separate Objdir
35826 @section Compiling @value{GDBN} in Another Directory
35828 If you want to run @value{GDBN} versions for several host or target machines,
35829 you need a different @code{gdb} compiled for each combination of
35830 host and target. @file{configure} is designed to make this easy by
35831 allowing you to generate each configuration in a separate subdirectory,
35832 rather than in the source directory. If your @code{make} program
35833 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
35834 @code{make} in each of these directories builds the @code{gdb}
35835 program specified there.
35837 To build @code{gdb} in a separate directory, run @file{configure}
35838 with the @samp{--srcdir} option to specify where to find the source.
35839 (You also need to specify a path to find @file{configure}
35840 itself from your working directory. If the path to @file{configure}
35841 would be the same as the argument to @samp{--srcdir}, you can leave out
35842 the @samp{--srcdir} option; it is assumed.)
35844 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
35845 separate directory for a Sun 4 like this:
35849 cd gdb-@value{GDBVN}
35852 ../gdb-@value{GDBVN}/configure
35857 When @file{configure} builds a configuration using a remote source
35858 directory, it creates a tree for the binaries with the same structure
35859 (and using the same names) as the tree under the source directory. In
35860 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35861 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35862 @file{gdb-sun4/gdb}.
35864 Make sure that your path to the @file{configure} script has just one
35865 instance of @file{gdb} in it. If your path to @file{configure} looks
35866 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35867 one subdirectory of @value{GDBN}, not the whole package. This leads to
35868 build errors about missing include files such as @file{bfd/bfd.h}.
35870 One popular reason to build several @value{GDBN} configurations in separate
35871 directories is to configure @value{GDBN} for cross-compiling (where
35872 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35873 programs that run on another machine---the @dfn{target}).
35874 You specify a cross-debugging target by
35875 giving the @samp{--target=@var{target}} option to @file{configure}.
35877 When you run @code{make} to build a program or library, you must run
35878 it in a configured directory---whatever directory you were in when you
35879 called @file{configure} (or one of its subdirectories).
35881 The @code{Makefile} that @file{configure} generates in each source
35882 directory also runs recursively. If you type @code{make} in a source
35883 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35884 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35885 will build all the required libraries, and then build GDB.
35887 When you have multiple hosts or targets configured in separate
35888 directories, you can run @code{make} on them in parallel (for example,
35889 if they are NFS-mounted on each of the hosts); they will not interfere
35893 @section Specifying Names for Hosts and Targets
35895 The specifications used for hosts and targets in the @file{configure}
35896 script are based on a three-part naming scheme, but some short predefined
35897 aliases are also supported. The full naming scheme encodes three pieces
35898 of information in the following pattern:
35901 @var{architecture}-@var{vendor}-@var{os}
35904 For example, you can use the alias @code{sun4} as a @var{host} argument,
35905 or as the value for @var{target} in a @code{--target=@var{target}}
35906 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35908 The @file{configure} script accompanying @value{GDBN} does not provide
35909 any query facility to list all supported host and target names or
35910 aliases. @file{configure} calls the Bourne shell script
35911 @code{config.sub} to map abbreviations to full names; you can read the
35912 script, if you wish, or you can use it to test your guesses on
35913 abbreviations---for example:
35916 % sh config.sub i386-linux
35918 % sh config.sub alpha-linux
35919 alpha-unknown-linux-gnu
35920 % sh config.sub hp9k700
35922 % sh config.sub sun4
35923 sparc-sun-sunos4.1.1
35924 % sh config.sub sun3
35925 m68k-sun-sunos4.1.1
35926 % sh config.sub i986v
35927 Invalid configuration `i986v': machine `i986v' not recognized
35931 @code{config.sub} is also distributed in the @value{GDBN} source
35932 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35934 @node Configure Options
35935 @section @file{configure} Options
35937 Here is a summary of the @file{configure} options and arguments that
35938 are most often useful for building @value{GDBN}. @file{configure}
35939 also has several other options not listed here. @inforef{Running
35940 configure scripts,,autoconf.info}, for a full
35941 explanation of @file{configure}.
35944 configure @r{[}--help@r{]}
35945 @r{[}--prefix=@var{dir}@r{]}
35946 @r{[}--exec-prefix=@var{dir}@r{]}
35947 @r{[}--srcdir=@var{dirname}@r{]}
35948 @r{[}--target=@var{target}@r{]}
35952 You may introduce options with a single @samp{-} rather than
35953 @samp{--} if you prefer; but you may abbreviate option names if you use
35958 Display a quick summary of how to invoke @file{configure}.
35960 @item --prefix=@var{dir}
35961 Configure the source to install programs and files under directory
35964 @item --exec-prefix=@var{dir}
35965 Configure the source to install programs under directory
35968 @c avoid splitting the warning from the explanation:
35970 @item --srcdir=@var{dirname}
35971 Use this option to make configurations in directories separate from the
35972 @value{GDBN} source directories. Among other things, you can use this to
35973 build (or maintain) several configurations simultaneously, in separate
35974 directories. @file{configure} writes configuration-specific files in
35975 the current directory, but arranges for them to use the source in the
35976 directory @var{dirname}. @file{configure} creates directories under
35977 the working directory in parallel to the source directories below
35980 @item --target=@var{target}
35981 Configure @value{GDBN} for cross-debugging programs running on the specified
35982 @var{target}. Without this option, @value{GDBN} is configured to debug
35983 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35985 There is no convenient way to generate a list of all available
35986 targets. Also see the @code{--enable-targets} option, below.
35989 There are many other options that are specific to @value{GDBN}. This
35990 lists just the most common ones; there are some very specialized
35991 options not described here.
35994 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
35995 @itemx --enable-targets=all
35996 Configure @value{GDBN} for cross-debugging programs running on the
35997 specified list of targets. The special value @samp{all} configures
35998 @value{GDBN} for debugging programs running on any target it supports.
36000 @item --with-gdb-datadir=@var{path}
36001 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
36002 here for certain supporting files or scripts. This defaults to the
36003 @file{gdb} subdirectory of @samp{datadi} (which can be set using
36006 @item --with-relocated-sources=@var{dir}
36007 Sets up the default source path substitution rule so that directory
36008 names recorded in debug information will be automatically adjusted for
36009 any directory under @var{dir}. @var{dir} should be a subdirectory of
36010 @value{GDBN}'s configured prefix, the one mentioned in the
36011 @code{--prefix} or @code{--exec-prefix} options to configure. This
36012 option is useful if GDB is supposed to be moved to a different place
36015 @item --enable-64-bit-bfd
36016 Enable 64-bit support in BFD on 32-bit hosts.
36018 @item --disable-gdbmi
36019 Build @value{GDBN} without the GDB/MI machine interface
36023 Build @value{GDBN} with the text-mode full-screen user interface
36024 (TUI). Requires a curses library (ncurses and cursesX are also
36027 @item --with-curses
36028 Use the curses library instead of the termcap library, for text-mode
36029 terminal operations.
36031 @item --with-libunwind-ia64
36032 Use the libunwind library for unwinding function call stack on ia64
36033 target platforms. See http://www.nongnu.org/libunwind/index.html for
36036 @item --with-system-readline
36037 Use the readline library installed on the host, rather than the
36038 library supplied as part of @value{GDBN}.
36040 @item --with-system-zlib
36041 Use the zlib library installed on the host, rather than the library
36042 supplied as part of @value{GDBN}.
36045 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
36046 default if libexpat is installed and found at configure time.) This
36047 library is used to read XML files supplied with @value{GDBN}. If it
36048 is unavailable, some features, such as remote protocol memory maps,
36049 target descriptions, and shared library lists, that are based on XML
36050 files, will not be available in @value{GDBN}. If your host does not
36051 have libexpat installed, you can get the latest version from
36052 `http://expat.sourceforge.net'.
36054 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
36056 Build @value{GDBN} with GNU libiconv, a character set encoding
36057 conversion library. This is not done by default, as on GNU systems
36058 the @code{iconv} that is built in to the C library is sufficient. If
36059 your host does not have a working @code{iconv}, you can get the latest
36060 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
36062 @value{GDBN}'s build system also supports building GNU libiconv as
36063 part of the overall build. @xref{Requirements}.
36066 Build @value{GDBN} with LZMA, a compression library. (Done by default
36067 if liblzma is installed and found at configure time.) LZMA is used by
36068 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
36069 platforms using the ELF object file format. If your host does not
36070 have liblzma installed, you can get the latest version from
36071 `https://tukaani.org/xz/'.
36074 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
36075 floating-point computation with correct rounding. (Done by default if
36076 GNU MPFR is installed and found at configure time.) This library is
36077 used to emulate target floating-point arithmetic during expression
36078 evaluation when the target uses different floating-point formats than
36079 the host. If GNU MPFR is not available, @value{GDBN} will fall back
36080 to using host floating-point arithmetic. If your host does not have
36081 GNU MPFR installed, you can get the latest version from
36082 `http://www.mpfr.org'.
36084 @item --with-python@r{[}=@var{python}@r{]}
36085 Build @value{GDBN} with Python scripting support. (Done by default if
36086 libpython is present and found at configure time.) Python makes
36087 @value{GDBN} scripting much more powerful than the restricted CLI
36088 scripting language. If your host does not have Python installed, you
36089 can find it on `http://www.python.org/download/'. The oldest version
36090 of Python supported by GDB is 2.6. The optional argument @var{python}
36091 is used to find the Python headers and libraries. It can be either
36092 the name of a Python executable, or the name of the directory in which
36093 Python is installed.
36095 @item --with-guile[=GUILE]'
36096 Build @value{GDBN} with GNU Guile scripting support. (Done by default
36097 if libguile is present and found at configure time.) If your host
36098 does not have Guile installed, you can find it at
36099 `https://www.gnu.org/software/guile/'. The optional argument GUILE
36100 can be a version number, which will cause @code{configure} to try to
36101 use that version of Guile; or the file name of a @code{pkg-config}
36102 executable, which will be queried to find the information needed to
36103 compile and link against Guile.
36105 @item --without-included-regex
36106 Don't use the regex library included with @value{GDBN} (as part of the
36107 libiberty library). This is the default on hosts with version 2 of
36110 @item --with-sysroot=@var{dir}
36111 Use @var{dir} as the default system root directory for libraries whose
36112 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
36113 @var{dir} can be modified at run time by using the @command{set
36114 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
36115 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
36116 default system root will be automatically adjusted if and when
36117 @value{GDBN} is moved to a different location.
36119 @item --with-system-gdbinit=@var{file}
36120 Configure @value{GDBN} to automatically load a system-wide init file.
36121 @var{file} should be an absolute file name. If @var{file} is in a
36122 directory under the configured prefix, and @value{GDBN} is moved to
36123 another location after being built, the location of the system-wide
36124 init file will be adjusted accordingly.
36126 @item --enable-build-warnings
36127 When building the @value{GDBN} sources, ask the compiler to warn about
36128 any code which looks even vaguely suspicious. It passes many
36129 different warning flags, depending on the exact version of the
36130 compiler you are using.
36132 @item --enable-werror
36133 Treat compiler warnings as werrors. It adds the @code{-Werror} flag
36134 to the compiler, which will fail the compilation if the compiler
36135 outputs any warning messages.
36137 @item --enable-ubsan
36138 Enable the GCC undefined behavior sanitizer. This is disabled by
36139 default, but passing @code{--enable-ubsan=yes} or
36140 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
36141 undefined behavior sanitizer checks for C@t{++} undefined behavior.
36142 It has a performance cost, so if you are looking at @value{GDBN}'s
36143 performance, you should disable it. The undefined behavior sanitizer
36144 was first introduced in GCC 4.9.
36147 @node System-wide configuration
36148 @section System-wide configuration and settings
36149 @cindex system-wide init file
36151 @value{GDBN} can be configured to have a system-wide init file;
36152 this file will be read and executed at startup (@pxref{Startup, , What
36153 @value{GDBN} does during startup}).
36155 Here is the corresponding configure option:
36158 @item --with-system-gdbinit=@var{file}
36159 Specify that the default location of the system-wide init file is
36163 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
36164 it may be subject to relocation. Two possible cases:
36168 If the default location of this init file contains @file{$prefix},
36169 it will be subject to relocation. Suppose that the configure options
36170 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
36171 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
36172 init file is looked for as @file{$install/etc/gdbinit} instead of
36173 @file{$prefix/etc/gdbinit}.
36176 By contrast, if the default location does not contain the prefix,
36177 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
36178 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
36179 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
36180 wherever @value{GDBN} is installed.
36183 If the configured location of the system-wide init file (as given by the
36184 @option{--with-system-gdbinit} option at configure time) is in the
36185 data-directory (as specified by @option{--with-gdb-datadir} at configure
36186 time) or in one of its subdirectories, then @value{GDBN} will look for the
36187 system-wide init file in the directory specified by the
36188 @option{--data-directory} command-line option.
36189 Note that the system-wide init file is only read once, during @value{GDBN}
36190 initialization. If the data-directory is changed after @value{GDBN} has
36191 started with the @code{set data-directory} command, the file will not be
36195 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
36198 @node System-wide Configuration Scripts
36199 @subsection Installed System-wide Configuration Scripts
36200 @cindex system-wide configuration scripts
36202 The @file{system-gdbinit} directory, located inside the data-directory
36203 (as specified by @option{--with-gdb-datadir} at configure time) contains
36204 a number of scripts which can be used as system-wide init files. To
36205 automatically source those scripts at startup, @value{GDBN} should be
36206 configured with @option{--with-system-gdbinit}. Otherwise, any user
36207 should be able to source them by hand as needed.
36209 The following scripts are currently available:
36212 @item @file{elinos.py}
36214 @cindex ELinOS system-wide configuration script
36215 This script is useful when debugging a program on an ELinOS target.
36216 It takes advantage of the environment variables defined in a standard
36217 ELinOS environment in order to determine the location of the system
36218 shared libraries, and then sets the @samp{solib-absolute-prefix}
36219 and @samp{solib-search-path} variables appropriately.
36221 @item @file{wrs-linux.py}
36222 @pindex wrs-linux.py
36223 @cindex Wind River Linux system-wide configuration script
36224 This script is useful when debugging a program on a target running
36225 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
36226 the host-side sysroot used by the target system.
36230 @node Maintenance Commands
36231 @appendix Maintenance Commands
36232 @cindex maintenance commands
36233 @cindex internal commands
36235 In addition to commands intended for @value{GDBN} users, @value{GDBN}
36236 includes a number of commands intended for @value{GDBN} developers,
36237 that are not documented elsewhere in this manual. These commands are
36238 provided here for reference. (For commands that turn on debugging
36239 messages, see @ref{Debugging Output}.)
36242 @kindex maint agent
36243 @kindex maint agent-eval
36244 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36245 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36246 Translate the given @var{expression} into remote agent bytecodes.
36247 This command is useful for debugging the Agent Expression mechanism
36248 (@pxref{Agent Expressions}). The @samp{agent} version produces an
36249 expression useful for data collection, such as by tracepoints, while
36250 @samp{maint agent-eval} produces an expression that evaluates directly
36251 to a result. For instance, a collection expression for @code{globa +
36252 globb} will include bytecodes to record four bytes of memory at each
36253 of the addresses of @code{globa} and @code{globb}, while discarding
36254 the result of the addition, while an evaluation expression will do the
36255 addition and return the sum.
36256 If @code{-at} is given, generate remote agent bytecode for @var{location}.
36257 If not, generate remote agent bytecode for current frame PC address.
36259 @kindex maint agent-printf
36260 @item maint agent-printf @var{format},@var{expr},...
36261 Translate the given format string and list of argument expressions
36262 into remote agent bytecodes and display them as a disassembled list.
36263 This command is useful for debugging the agent version of dynamic
36264 printf (@pxref{Dynamic Printf}).
36266 @kindex maint info breakpoints
36267 @item @anchor{maint info breakpoints}maint info breakpoints
36268 Using the same format as @samp{info breakpoints}, display both the
36269 breakpoints you've set explicitly, and those @value{GDBN} is using for
36270 internal purposes. Internal breakpoints are shown with negative
36271 breakpoint numbers. The type column identifies what kind of breakpoint
36276 Normal, explicitly set breakpoint.
36279 Normal, explicitly set watchpoint.
36282 Internal breakpoint, used to handle correctly stepping through
36283 @code{longjmp} calls.
36285 @item longjmp resume
36286 Internal breakpoint at the target of a @code{longjmp}.
36289 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
36292 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
36295 Shared library events.
36299 @kindex maint info btrace
36300 @item maint info btrace
36301 Pint information about raw branch tracing data.
36303 @kindex maint btrace packet-history
36304 @item maint btrace packet-history
36305 Print the raw branch trace packets that are used to compute the
36306 execution history for the @samp{record btrace} command. Both the
36307 information and the format in which it is printed depend on the btrace
36312 For the BTS recording format, print a list of blocks of sequential
36313 code. For each block, the following information is printed:
36317 Newer blocks have higher numbers. The oldest block has number zero.
36318 @item Lowest @samp{PC}
36319 @item Highest @samp{PC}
36323 For the Intel Processor Trace recording format, print a list of
36324 Intel Processor Trace packets. For each packet, the following
36325 information is printed:
36328 @item Packet number
36329 Newer packets have higher numbers. The oldest packet has number zero.
36331 The packet's offset in the trace stream.
36332 @item Packet opcode and payload
36336 @kindex maint btrace clear-packet-history
36337 @item maint btrace clear-packet-history
36338 Discards the cached packet history printed by the @samp{maint btrace
36339 packet-history} command. The history will be computed again when
36342 @kindex maint btrace clear
36343 @item maint btrace clear
36344 Discard the branch trace data. The data will be fetched anew and the
36345 branch trace will be recomputed when needed.
36347 This implicitly truncates the branch trace to a single branch trace
36348 buffer. When updating branch trace incrementally, the branch trace
36349 available to @value{GDBN} may be bigger than a single branch trace
36352 @kindex maint set btrace pt skip-pad
36353 @item maint set btrace pt skip-pad
36354 @kindex maint show btrace pt skip-pad
36355 @item maint show btrace pt skip-pad
36356 Control whether @value{GDBN} will skip PAD packets when computing the
36359 @kindex set displaced-stepping
36360 @kindex show displaced-stepping
36361 @cindex displaced stepping support
36362 @cindex out-of-line single-stepping
36363 @item set displaced-stepping
36364 @itemx show displaced-stepping
36365 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
36366 if the target supports it. Displaced stepping is a way to single-step
36367 over breakpoints without removing them from the inferior, by executing
36368 an out-of-line copy of the instruction that was originally at the
36369 breakpoint location. It is also known as out-of-line single-stepping.
36372 @item set displaced-stepping on
36373 If the target architecture supports it, @value{GDBN} will use
36374 displaced stepping to step over breakpoints.
36376 @item set displaced-stepping off
36377 @value{GDBN} will not use displaced stepping to step over breakpoints,
36378 even if such is supported by the target architecture.
36380 @cindex non-stop mode, and @samp{set displaced-stepping}
36381 @item set displaced-stepping auto
36382 This is the default mode. @value{GDBN} will use displaced stepping
36383 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
36384 architecture supports displaced stepping.
36387 @kindex maint check-psymtabs
36388 @item maint check-psymtabs
36389 Check the consistency of currently expanded psymtabs versus symtabs.
36390 Use this to check, for example, whether a symbol is in one but not the other.
36392 @kindex maint check-symtabs
36393 @item maint check-symtabs
36394 Check the consistency of currently expanded symtabs.
36396 @kindex maint expand-symtabs
36397 @item maint expand-symtabs [@var{regexp}]
36398 Expand symbol tables.
36399 If @var{regexp} is specified, only expand symbol tables for file
36400 names matching @var{regexp}.
36402 @kindex maint set catch-demangler-crashes
36403 @kindex maint show catch-demangler-crashes
36404 @cindex demangler crashes
36405 @item maint set catch-demangler-crashes [on|off]
36406 @itemx maint show catch-demangler-crashes
36407 Control whether @value{GDBN} should attempt to catch crashes in the
36408 symbol name demangler. The default is to attempt to catch crashes.
36409 If enabled, the first time a crash is caught, a core file is created,
36410 the offending symbol is displayed and the user is presented with the
36411 option to terminate the current session.
36413 @kindex maint cplus first_component
36414 @item maint cplus first_component @var{name}
36415 Print the first C@t{++} class/namespace component of @var{name}.
36417 @kindex maint cplus namespace
36418 @item maint cplus namespace
36419 Print the list of possible C@t{++} namespaces.
36421 @kindex maint deprecate
36422 @kindex maint undeprecate
36423 @cindex deprecated commands
36424 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
36425 @itemx maint undeprecate @var{command}
36426 Deprecate or undeprecate the named @var{command}. Deprecated commands
36427 cause @value{GDBN} to issue a warning when you use them. The optional
36428 argument @var{replacement} says which newer command should be used in
36429 favor of the deprecated one; if it is given, @value{GDBN} will mention
36430 the replacement as part of the warning.
36432 @kindex maint dump-me
36433 @item maint dump-me
36434 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
36435 Cause a fatal signal in the debugger and force it to dump its core.
36436 This is supported only on systems which support aborting a program
36437 with the @code{SIGQUIT} signal.
36439 @kindex maint internal-error
36440 @kindex maint internal-warning
36441 @kindex maint demangler-warning
36442 @cindex demangler crashes
36443 @item maint internal-error @r{[}@var{message-text}@r{]}
36444 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
36445 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
36447 Cause @value{GDBN} to call the internal function @code{internal_error},
36448 @code{internal_warning} or @code{demangler_warning} and hence behave
36449 as though an internal problem has been detected. In addition to
36450 reporting the internal problem, these functions give the user the
36451 opportunity to either quit @value{GDBN} or (for @code{internal_error}
36452 and @code{internal_warning}) create a core file of the current
36453 @value{GDBN} session.
36455 These commands take an optional parameter @var{message-text} that is
36456 used as the text of the error or warning message.
36458 Here's an example of using @code{internal-error}:
36461 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
36462 @dots{}/maint.c:121: internal-error: testing, 1, 2
36463 A problem internal to GDB has been detected. Further
36464 debugging may prove unreliable.
36465 Quit this debugging session? (y or n) @kbd{n}
36466 Create a core file? (y or n) @kbd{n}
36470 @cindex @value{GDBN} internal error
36471 @cindex internal errors, control of @value{GDBN} behavior
36472 @cindex demangler crashes
36474 @kindex maint set internal-error
36475 @kindex maint show internal-error
36476 @kindex maint set internal-warning
36477 @kindex maint show internal-warning
36478 @kindex maint set demangler-warning
36479 @kindex maint show demangler-warning
36480 @item maint set internal-error @var{action} [ask|yes|no]
36481 @itemx maint show internal-error @var{action}
36482 @itemx maint set internal-warning @var{action} [ask|yes|no]
36483 @itemx maint show internal-warning @var{action}
36484 @itemx maint set demangler-warning @var{action} [ask|yes|no]
36485 @itemx maint show demangler-warning @var{action}
36486 When @value{GDBN} reports an internal problem (error or warning) it
36487 gives the user the opportunity to both quit @value{GDBN} and create a
36488 core file of the current @value{GDBN} session. These commands let you
36489 override the default behaviour for each particular @var{action},
36490 described in the table below.
36494 You can specify that @value{GDBN} should always (yes) or never (no)
36495 quit. The default is to ask the user what to do.
36498 You can specify that @value{GDBN} should always (yes) or never (no)
36499 create a core file. The default is to ask the user what to do. Note
36500 that there is no @code{corefile} option for @code{demangler-warning}:
36501 demangler warnings always create a core file and this cannot be
36505 @kindex maint packet
36506 @item maint packet @var{text}
36507 If @value{GDBN} is talking to an inferior via the serial protocol,
36508 then this command sends the string @var{text} to the inferior, and
36509 displays the response packet. @value{GDBN} supplies the initial
36510 @samp{$} character, the terminating @samp{#} character, and the
36513 @kindex maint print architecture
36514 @item maint print architecture @r{[}@var{file}@r{]}
36515 Print the entire architecture configuration. The optional argument
36516 @var{file} names the file where the output goes.
36518 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
36519 @item maint print c-tdesc
36520 Print the target description (@pxref{Target Descriptions}) as
36521 a C source file. By default, the target description is for the current
36522 target, but if the optional argument @var{file} is provided, that file
36523 is used to produce the description. The @var{file} should be an XML
36524 document, of the form described in @ref{Target Description Format}.
36525 The created source file is built into @value{GDBN} when @value{GDBN} is
36526 built again. This command is used by developers after they add or
36527 modify XML target descriptions.
36529 @kindex maint check xml-descriptions
36530 @item maint check xml-descriptions @var{dir}
36531 Check that the target descriptions dynamically created by @value{GDBN}
36532 equal the descriptions created from XML files found in @var{dir}.
36534 @anchor{maint check libthread-db}
36535 @kindex maint check libthread-db
36536 @item maint check libthread-db
36537 Run integrity checks on the current inferior's thread debugging
36538 library. This exercises all @code{libthread_db} functionality used by
36539 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
36540 @code{proc_service} functions provided by @value{GDBN} that
36541 @code{libthread_db} uses. Note that parts of the test may be skipped
36542 on some platforms when debugging core files.
36544 @kindex maint print dummy-frames
36545 @item maint print dummy-frames
36546 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
36549 (@value{GDBP}) @kbd{b add}
36551 (@value{GDBP}) @kbd{print add(2,3)}
36552 Breakpoint 2, add (a=2, b=3) at @dots{}
36554 The program being debugged stopped while in a function called from GDB.
36556 (@value{GDBP}) @kbd{maint print dummy-frames}
36557 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
36561 Takes an optional file parameter.
36563 @kindex maint print registers
36564 @kindex maint print raw-registers
36565 @kindex maint print cooked-registers
36566 @kindex maint print register-groups
36567 @kindex maint print remote-registers
36568 @item maint print registers @r{[}@var{file}@r{]}
36569 @itemx maint print raw-registers @r{[}@var{file}@r{]}
36570 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
36571 @itemx maint print register-groups @r{[}@var{file}@r{]}
36572 @itemx maint print remote-registers @r{[}@var{file}@r{]}
36573 Print @value{GDBN}'s internal register data structures.
36575 The command @code{maint print raw-registers} includes the contents of
36576 the raw register cache; the command @code{maint print
36577 cooked-registers} includes the (cooked) value of all registers,
36578 including registers which aren't available on the target nor visible
36579 to user; the command @code{maint print register-groups} includes the
36580 groups that each register is a member of; and the command @code{maint
36581 print remote-registers} includes the remote target's register numbers
36582 and offsets in the `G' packets.
36584 These commands take an optional parameter, a file name to which to
36585 write the information.
36587 @kindex maint print reggroups
36588 @item maint print reggroups @r{[}@var{file}@r{]}
36589 Print @value{GDBN}'s internal register group data structures. The
36590 optional argument @var{file} tells to what file to write the
36593 The register groups info looks like this:
36596 (@value{GDBP}) @kbd{maint print reggroups}
36609 This command forces @value{GDBN} to flush its internal register cache.
36611 @kindex maint print objfiles
36612 @cindex info for known object files
36613 @item maint print objfiles @r{[}@var{regexp}@r{]}
36614 Print a dump of all known object files.
36615 If @var{regexp} is specified, only print object files whose names
36616 match @var{regexp}. For each object file, this command prints its name,
36617 address in memory, and all of its psymtabs and symtabs.
36619 @kindex maint print user-registers
36620 @cindex user registers
36621 @item maint print user-registers
36622 List all currently available @dfn{user registers}. User registers
36623 typically provide alternate names for actual hardware registers. They
36624 include the four ``standard'' registers @code{$fp}, @code{$pc},
36625 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
36626 registers can be used in expressions in the same way as the canonical
36627 register names, but only the latter are listed by the @code{info
36628 registers} and @code{maint print registers} commands.
36630 @kindex maint print section-scripts
36631 @cindex info for known .debug_gdb_scripts-loaded scripts
36632 @item maint print section-scripts [@var{regexp}]
36633 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
36634 If @var{regexp} is specified, only print scripts loaded by object files
36635 matching @var{regexp}.
36636 For each script, this command prints its name as specified in the objfile,
36637 and the full path if known.
36638 @xref{dotdebug_gdb_scripts section}.
36640 @kindex maint print statistics
36641 @cindex bcache statistics
36642 @item maint print statistics
36643 This command prints, for each object file in the program, various data
36644 about that object file followed by the byte cache (@dfn{bcache})
36645 statistics for the object file. The objfile data includes the number
36646 of minimal, partial, full, and stabs symbols, the number of types
36647 defined by the objfile, the number of as yet unexpanded psym tables,
36648 the number of line tables and string tables, and the amount of memory
36649 used by the various tables. The bcache statistics include the counts,
36650 sizes, and counts of duplicates of all and unique objects, max,
36651 average, and median entry size, total memory used and its overhead and
36652 savings, and various measures of the hash table size and chain
36655 @kindex maint print target-stack
36656 @cindex target stack description
36657 @item maint print target-stack
36658 A @dfn{target} is an interface between the debugger and a particular
36659 kind of file or process. Targets can be stacked in @dfn{strata},
36660 so that more than one target can potentially respond to a request.
36661 In particular, memory accesses will walk down the stack of targets
36662 until they find a target that is interested in handling that particular
36665 This command prints a short description of each layer that was pushed on
36666 the @dfn{target stack}, starting from the top layer down to the bottom one.
36668 @kindex maint print type
36669 @cindex type chain of a data type
36670 @item maint print type @var{expr}
36671 Print the type chain for a type specified by @var{expr}. The argument
36672 can be either a type name or a symbol. If it is a symbol, the type of
36673 that symbol is described. The type chain produced by this command is
36674 a recursive definition of the data type as stored in @value{GDBN}'s
36675 data structures, including its flags and contained types.
36677 @kindex maint selftest
36679 @item maint selftest @r{[}@var{filter}@r{]}
36680 Run any self tests that were compiled in to @value{GDBN}. This will
36681 print a message showing how many tests were run, and how many failed.
36682 If a @var{filter} is passed, only the tests with @var{filter} in their
36685 @kindex "maint info selftests"
36687 @item maint info selftests
36688 List the selftests compiled in to @value{GDBN}.
36690 @kindex maint set dwarf always-disassemble
36691 @kindex maint show dwarf always-disassemble
36692 @item maint set dwarf always-disassemble
36693 @item maint show dwarf always-disassemble
36694 Control the behavior of @code{info address} when using DWARF debugging
36697 The default is @code{off}, which means that @value{GDBN} should try to
36698 describe a variable's location in an easily readable format. When
36699 @code{on}, @value{GDBN} will instead display the DWARF location
36700 expression in an assembly-like format. Note that some locations are
36701 too complex for @value{GDBN} to describe simply; in this case you will
36702 always see the disassembly form.
36704 Here is an example of the resulting disassembly:
36707 (gdb) info addr argc
36708 Symbol "argc" is a complex DWARF expression:
36712 For more information on these expressions, see
36713 @uref{http://www.dwarfstd.org/, the DWARF standard}.
36715 @kindex maint set dwarf max-cache-age
36716 @kindex maint show dwarf max-cache-age
36717 @item maint set dwarf max-cache-age
36718 @itemx maint show dwarf max-cache-age
36719 Control the DWARF compilation unit cache.
36721 @cindex DWARF compilation units cache
36722 In object files with inter-compilation-unit references, such as those
36723 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
36724 reader needs to frequently refer to previously read compilation units.
36725 This setting controls how long a compilation unit will remain in the
36726 cache if it is not referenced. A higher limit means that cached
36727 compilation units will be stored in memory longer, and more total
36728 memory will be used. Setting it to zero disables caching, which will
36729 slow down @value{GDBN} startup, but reduce memory consumption.
36731 @kindex maint set dwarf unwinders
36732 @kindex maint show dwarf unwinders
36733 @item maint set dwarf unwinders
36734 @itemx maint show dwarf unwinders
36735 Control use of the DWARF frame unwinders.
36737 @cindex DWARF frame unwinders
36738 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
36739 frame unwinders to build the backtrace. Many of these targets will
36740 also have a second mechanism for building the backtrace for use in
36741 cases where DWARF information is not available, this second mechanism
36742 is often an analysis of a function's prologue.
36744 In order to extend testing coverage of the second level stack
36745 unwinding mechanisms it is helpful to be able to disable the DWARF
36746 stack unwinders, this can be done with this switch.
36748 In normal use of @value{GDBN} disabling the DWARF unwinders is not
36749 advisable, there are cases that are better handled through DWARF than
36750 prologue analysis, and the debug experience is likely to be better
36751 with the DWARF frame unwinders enabled.
36753 If DWARF frame unwinders are not supported for a particular target
36754 architecture, then enabling this flag does not cause them to be used.
36755 @kindex maint set profile
36756 @kindex maint show profile
36757 @cindex profiling GDB
36758 @item maint set profile
36759 @itemx maint show profile
36760 Control profiling of @value{GDBN}.
36762 Profiling will be disabled until you use the @samp{maint set profile}
36763 command to enable it. When you enable profiling, the system will begin
36764 collecting timing and execution count data; when you disable profiling or
36765 exit @value{GDBN}, the results will be written to a log file. Remember that
36766 if you use profiling, @value{GDBN} will overwrite the profiling log file
36767 (often called @file{gmon.out}). If you have a record of important profiling
36768 data in a @file{gmon.out} file, be sure to move it to a safe location.
36770 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
36771 compiled with the @samp{-pg} compiler option.
36773 @kindex maint set show-debug-regs
36774 @kindex maint show show-debug-regs
36775 @cindex hardware debug registers
36776 @item maint set show-debug-regs
36777 @itemx maint show show-debug-regs
36778 Control whether to show variables that mirror the hardware debug
36779 registers. Use @code{on} to enable, @code{off} to disable. If
36780 enabled, the debug registers values are shown when @value{GDBN} inserts or
36781 removes a hardware breakpoint or watchpoint, and when the inferior
36782 triggers a hardware-assisted breakpoint or watchpoint.
36784 @kindex maint set show-all-tib
36785 @kindex maint show show-all-tib
36786 @item maint set show-all-tib
36787 @itemx maint show show-all-tib
36788 Control whether to show all non zero areas within a 1k block starting
36789 at thread local base, when using the @samp{info w32 thread-information-block}
36792 @kindex maint set target-async
36793 @kindex maint show target-async
36794 @item maint set target-async
36795 @itemx maint show target-async
36796 This controls whether @value{GDBN} targets operate in synchronous or
36797 asynchronous mode (@pxref{Background Execution}). Normally the
36798 default is asynchronous, if it is available; but this can be changed
36799 to more easily debug problems occurring only in synchronous mode.
36801 @kindex maint set target-non-stop @var{mode} [on|off|auto]
36802 @kindex maint show target-non-stop
36803 @item maint set target-non-stop
36804 @itemx maint show target-non-stop
36806 This controls whether @value{GDBN} targets always operate in non-stop
36807 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
36808 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
36809 if supported by the target.
36812 @item maint set target-non-stop auto
36813 This is the default mode. @value{GDBN} controls the target in
36814 non-stop mode if the target supports it.
36816 @item maint set target-non-stop on
36817 @value{GDBN} controls the target in non-stop mode even if the target
36818 does not indicate support.
36820 @item maint set target-non-stop off
36821 @value{GDBN} does not control the target in non-stop mode even if the
36822 target supports it.
36825 @kindex maint set per-command
36826 @kindex maint show per-command
36827 @item maint set per-command
36828 @itemx maint show per-command
36829 @cindex resources used by commands
36831 @value{GDBN} can display the resources used by each command.
36832 This is useful in debugging performance problems.
36835 @item maint set per-command space [on|off]
36836 @itemx maint show per-command space
36837 Enable or disable the printing of the memory used by GDB for each command.
36838 If enabled, @value{GDBN} will display how much memory each command
36839 took, following the command's own output.
36840 This can also be requested by invoking @value{GDBN} with the
36841 @option{--statistics} command-line switch (@pxref{Mode Options}).
36843 @item maint set per-command time [on|off]
36844 @itemx maint show per-command time
36845 Enable or disable the printing of the execution time of @value{GDBN}
36847 If enabled, @value{GDBN} will display how much time it
36848 took to execute each command, following the command's own output.
36849 Both CPU time and wallclock time are printed.
36850 Printing both is useful when trying to determine whether the cost is
36851 CPU or, e.g., disk/network latency.
36852 Note that the CPU time printed is for @value{GDBN} only, it does not include
36853 the execution time of the inferior because there's no mechanism currently
36854 to compute how much time was spent by @value{GDBN} and how much time was
36855 spent by the program been debugged.
36856 This can also be requested by invoking @value{GDBN} with the
36857 @option{--statistics} command-line switch (@pxref{Mode Options}).
36859 @item maint set per-command symtab [on|off]
36860 @itemx maint show per-command symtab
36861 Enable or disable the printing of basic symbol table statistics
36863 If enabled, @value{GDBN} will display the following information:
36867 number of symbol tables
36869 number of primary symbol tables
36871 number of blocks in the blockvector
36875 @kindex maint set check-libthread-db
36876 @kindex maint show check-libthread-db
36877 @item maint set check-libthread-db [on|off]
36878 @itemx maint show check-libthread-db
36879 Control whether @value{GDBN} should run integrity checks on inferior
36880 specific thread debugging libraries as they are loaded. The default
36881 is not to perform such checks. If any check fails @value{GDBN} will
36882 unload the library and continue searching for a suitable candidate as
36883 described in @ref{set libthread-db-search-path}. For more information
36884 about the tests, see @ref{maint check libthread-db}.
36886 @kindex maint space
36887 @cindex memory used by commands
36888 @item maint space @var{value}
36889 An alias for @code{maint set per-command space}.
36890 A non-zero value enables it, zero disables it.
36893 @cindex time of command execution
36894 @item maint time @var{value}
36895 An alias for @code{maint set per-command time}.
36896 A non-zero value enables it, zero disables it.
36898 @kindex maint translate-address
36899 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
36900 Find the symbol stored at the location specified by the address
36901 @var{addr} and an optional section name @var{section}. If found,
36902 @value{GDBN} prints the name of the closest symbol and an offset from
36903 the symbol's location to the specified address. This is similar to
36904 the @code{info address} command (@pxref{Symbols}), except that this
36905 command also allows to find symbols in other sections.
36907 If section was not specified, the section in which the symbol was found
36908 is also printed. For dynamically linked executables, the name of
36909 executable or shared library containing the symbol is printed as well.
36913 The following command is useful for non-interactive invocations of
36914 @value{GDBN}, such as in the test suite.
36917 @item set watchdog @var{nsec}
36918 @kindex set watchdog
36919 @cindex watchdog timer
36920 @cindex timeout for commands
36921 Set the maximum number of seconds @value{GDBN} will wait for the
36922 target operation to finish. If this time expires, @value{GDBN}
36923 reports and error and the command is aborted.
36925 @item show watchdog
36926 Show the current setting of the target wait timeout.
36929 @node Remote Protocol
36930 @appendix @value{GDBN} Remote Serial Protocol
36935 * Stop Reply Packets::
36936 * General Query Packets::
36937 * Architecture-Specific Protocol Details::
36938 * Tracepoint Packets::
36939 * Host I/O Packets::
36941 * Notification Packets::
36942 * Remote Non-Stop::
36943 * Packet Acknowledgment::
36945 * File-I/O Remote Protocol Extension::
36946 * Library List Format::
36947 * Library List Format for SVR4 Targets::
36948 * Memory Map Format::
36949 * Thread List Format::
36950 * Traceframe Info Format::
36951 * Branch Trace Format::
36952 * Branch Trace Configuration Format::
36958 There may be occasions when you need to know something about the
36959 protocol---for example, if there is only one serial port to your target
36960 machine, you might want your program to do something special if it
36961 recognizes a packet meant for @value{GDBN}.
36963 In the examples below, @samp{->} and @samp{<-} are used to indicate
36964 transmitted and received data, respectively.
36966 @cindex protocol, @value{GDBN} remote serial
36967 @cindex serial protocol, @value{GDBN} remote
36968 @cindex remote serial protocol
36969 All @value{GDBN} commands and responses (other than acknowledgments
36970 and notifications, see @ref{Notification Packets}) are sent as a
36971 @var{packet}. A @var{packet} is introduced with the character
36972 @samp{$}, the actual @var{packet-data}, and the terminating character
36973 @samp{#} followed by a two-digit @var{checksum}:
36976 @code{$}@var{packet-data}@code{#}@var{checksum}
36980 @cindex checksum, for @value{GDBN} remote
36982 The two-digit @var{checksum} is computed as the modulo 256 sum of all
36983 characters between the leading @samp{$} and the trailing @samp{#} (an
36984 eight bit unsigned checksum).
36986 Implementors should note that prior to @value{GDBN} 5.0 the protocol
36987 specification also included an optional two-digit @var{sequence-id}:
36990 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
36993 @cindex sequence-id, for @value{GDBN} remote
36995 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
36996 has never output @var{sequence-id}s. Stubs that handle packets added
36997 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
36999 When either the host or the target machine receives a packet, the first
37000 response expected is an acknowledgment: either @samp{+} (to indicate
37001 the package was received correctly) or @samp{-} (to request
37005 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37010 The @samp{+}/@samp{-} acknowledgments can be disabled
37011 once a connection is established.
37012 @xref{Packet Acknowledgment}, for details.
37014 The host (@value{GDBN}) sends @var{command}s, and the target (the
37015 debugging stub incorporated in your program) sends a @var{response}. In
37016 the case of step and continue @var{command}s, the response is only sent
37017 when the operation has completed, and the target has again stopped all
37018 threads in all attached processes. This is the default all-stop mode
37019 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37020 execution mode; see @ref{Remote Non-Stop}, for details.
37022 @var{packet-data} consists of a sequence of characters with the
37023 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37026 @cindex remote protocol, field separator
37027 Fields within the packet should be separated using @samp{,} @samp{;} or
37028 @samp{:}. Except where otherwise noted all numbers are represented in
37029 @sc{hex} with leading zeros suppressed.
37031 Implementors should note that prior to @value{GDBN} 5.0, the character
37032 @samp{:} could not appear as the third character in a packet (as it
37033 would potentially conflict with the @var{sequence-id}).
37035 @cindex remote protocol, binary data
37036 @anchor{Binary Data}
37037 Binary data in most packets is encoded either as two hexadecimal
37038 digits per byte of binary data. This allowed the traditional remote
37039 protocol to work over connections which were only seven-bit clean.
37040 Some packets designed more recently assume an eight-bit clean
37041 connection, and use a more efficient encoding to send and receive
37044 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37045 as an escape character. Any escaped byte is transmitted as the escape
37046 character followed by the original character XORed with @code{0x20}.
37047 For example, the byte @code{0x7d} would be transmitted as the two
37048 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37049 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37050 @samp{@}}) must always be escaped. Responses sent by the stub
37051 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37052 is not interpreted as the start of a run-length encoded sequence
37055 Response @var{data} can be run-length encoded to save space.
37056 Run-length encoding replaces runs of identical characters with one
37057 instance of the repeated character, followed by a @samp{*} and a
37058 repeat count. The repeat count is itself sent encoded, to avoid
37059 binary characters in @var{data}: a value of @var{n} is sent as
37060 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37061 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37062 code 32) for a repeat count of 3. (This is because run-length
37063 encoding starts to win for counts 3 or more.) Thus, for example,
37064 @samp{0* } is a run-length encoding of ``0000'': the space character
37065 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37068 The printable characters @samp{#} and @samp{$} or with a numeric value
37069 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37070 seven repeats (@samp{$}) can be expanded using a repeat count of only
37071 five (@samp{"}). For example, @samp{00000000} can be encoded as
37074 The error response returned for some packets includes a two character
37075 error number. That number is not well defined.
37077 @cindex empty response, for unsupported packets
37078 For any @var{command} not supported by the stub, an empty response
37079 (@samp{$#00}) should be returned. That way it is possible to extend the
37080 protocol. A newer @value{GDBN} can tell if a packet is supported based
37083 At a minimum, a stub is required to support the @samp{g} and @samp{G}
37084 commands for register access, and the @samp{m} and @samp{M} commands
37085 for memory access. Stubs that only control single-threaded targets
37086 can implement run control with the @samp{c} (continue), and @samp{s}
37087 (step) commands. Stubs that support multi-threading targets should
37088 support the @samp{vCont} command. All other commands are optional.
37093 The following table provides a complete list of all currently defined
37094 @var{command}s and their corresponding response @var{data}.
37095 @xref{File-I/O Remote Protocol Extension}, for details about the File
37096 I/O extension of the remote protocol.
37098 Each packet's description has a template showing the packet's overall
37099 syntax, followed by an explanation of the packet's meaning. We
37100 include spaces in some of the templates for clarity; these are not
37101 part of the packet's syntax. No @value{GDBN} packet uses spaces to
37102 separate its components. For example, a template like @samp{foo
37103 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
37104 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
37105 @var{baz}. @value{GDBN} does not transmit a space character between the
37106 @samp{foo} and the @var{bar}, or between the @var{bar} and the
37109 @cindex @var{thread-id}, in remote protocol
37110 @anchor{thread-id syntax}
37111 Several packets and replies include a @var{thread-id} field to identify
37112 a thread. Normally these are positive numbers with a target-specific
37113 interpretation, formatted as big-endian hex strings. A @var{thread-id}
37114 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
37117 In addition, the remote protocol supports a multiprocess feature in
37118 which the @var{thread-id} syntax is extended to optionally include both
37119 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
37120 The @var{pid} (process) and @var{tid} (thread) components each have the
37121 format described above: a positive number with target-specific
37122 interpretation formatted as a big-endian hex string, literal @samp{-1}
37123 to indicate all processes or threads (respectively), or @samp{0} to
37124 indicate an arbitrary process or thread. Specifying just a process, as
37125 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
37126 error to specify all processes but a specific thread, such as
37127 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
37128 for those packets and replies explicitly documented to include a process
37129 ID, rather than a @var{thread-id}.
37131 The multiprocess @var{thread-id} syntax extensions are only used if both
37132 @value{GDBN} and the stub report support for the @samp{multiprocess}
37133 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
37136 Note that all packet forms beginning with an upper- or lower-case
37137 letter, other than those described here, are reserved for future use.
37139 Here are the packet descriptions.
37144 @cindex @samp{!} packet
37145 @anchor{extended mode}
37146 Enable extended mode. In extended mode, the remote server is made
37147 persistent. The @samp{R} packet is used to restart the program being
37153 The remote target both supports and has enabled extended mode.
37157 @cindex @samp{?} packet
37159 Indicate the reason the target halted. The reply is the same as for
37160 step and continue. This packet has a special interpretation when the
37161 target is in non-stop mode; see @ref{Remote Non-Stop}.
37164 @xref{Stop Reply Packets}, for the reply specifications.
37166 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
37167 @cindex @samp{A} packet
37168 Initialized @code{argv[]} array passed into program. @var{arglen}
37169 specifies the number of bytes in the hex encoded byte stream
37170 @var{arg}. See @code{gdbserver} for more details.
37175 The arguments were set.
37181 @cindex @samp{b} packet
37182 (Don't use this packet; its behavior is not well-defined.)
37183 Change the serial line speed to @var{baud}.
37185 JTC: @emph{When does the transport layer state change? When it's
37186 received, or after the ACK is transmitted. In either case, there are
37187 problems if the command or the acknowledgment packet is dropped.}
37189 Stan: @emph{If people really wanted to add something like this, and get
37190 it working for the first time, they ought to modify ser-unix.c to send
37191 some kind of out-of-band message to a specially-setup stub and have the
37192 switch happen "in between" packets, so that from remote protocol's point
37193 of view, nothing actually happened.}
37195 @item B @var{addr},@var{mode}
37196 @cindex @samp{B} packet
37197 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
37198 breakpoint at @var{addr}.
37200 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
37201 (@pxref{insert breakpoint or watchpoint packet}).
37203 @cindex @samp{bc} packet
37206 Backward continue. Execute the target system in reverse. No parameter.
37207 @xref{Reverse Execution}, for more information.
37210 @xref{Stop Reply Packets}, for the reply specifications.
37212 @cindex @samp{bs} packet
37215 Backward single step. Execute one instruction in reverse. No parameter.
37216 @xref{Reverse Execution}, for more information.
37219 @xref{Stop Reply Packets}, for the reply specifications.
37221 @item c @r{[}@var{addr}@r{]}
37222 @cindex @samp{c} packet
37223 Continue at @var{addr}, which is the address to resume. If @var{addr}
37224 is omitted, resume at current address.
37226 This packet is deprecated for multi-threading support. @xref{vCont
37230 @xref{Stop Reply Packets}, for the reply specifications.
37232 @item C @var{sig}@r{[};@var{addr}@r{]}
37233 @cindex @samp{C} packet
37234 Continue with signal @var{sig} (hex signal number). If
37235 @samp{;@var{addr}} is omitted, resume at same address.
37237 This packet is deprecated for multi-threading support. @xref{vCont
37241 @xref{Stop Reply Packets}, for the reply specifications.
37244 @cindex @samp{d} packet
37247 Don't use this packet; instead, define a general set packet
37248 (@pxref{General Query Packets}).
37252 @cindex @samp{D} packet
37253 The first form of the packet is used to detach @value{GDBN} from the
37254 remote system. It is sent to the remote target
37255 before @value{GDBN} disconnects via the @code{detach} command.
37257 The second form, including a process ID, is used when multiprocess
37258 protocol extensions are enabled (@pxref{multiprocess extensions}), to
37259 detach only a specific process. The @var{pid} is specified as a
37260 big-endian hex string.
37270 @item F @var{RC},@var{EE},@var{CF};@var{XX}
37271 @cindex @samp{F} packet
37272 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
37273 This is part of the File-I/O protocol extension. @xref{File-I/O
37274 Remote Protocol Extension}, for the specification.
37277 @anchor{read registers packet}
37278 @cindex @samp{g} packet
37279 Read general registers.
37283 @item @var{XX@dots{}}
37284 Each byte of register data is described by two hex digits. The bytes
37285 with the register are transmitted in target byte order. The size of
37286 each register and their position within the @samp{g} packet are
37287 determined by the @value{GDBN} internal gdbarch functions
37288 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
37290 When reading registers from a trace frame (@pxref{Analyze Collected
37291 Data,,Using the Collected Data}), the stub may also return a string of
37292 literal @samp{x}'s in place of the register data digits, to indicate
37293 that the corresponding register has not been collected, thus its value
37294 is unavailable. For example, for an architecture with 4 registers of
37295 4 bytes each, the following reply indicates to @value{GDBN} that
37296 registers 0 and 2 have not been collected, while registers 1 and 3
37297 have been collected, and both have zero value:
37301 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
37308 @item G @var{XX@dots{}}
37309 @cindex @samp{G} packet
37310 Write general registers. @xref{read registers packet}, for a
37311 description of the @var{XX@dots{}} data.
37321 @item H @var{op} @var{thread-id}
37322 @cindex @samp{H} packet
37323 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
37324 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
37325 should be @samp{c} for step and continue operations (note that this
37326 is deprecated, supporting the @samp{vCont} command is a better
37327 option), and @samp{g} for other operations. The thread designator
37328 @var{thread-id} has the format and interpretation described in
37329 @ref{thread-id syntax}.
37340 @c 'H': How restrictive (or permissive) is the thread model. If a
37341 @c thread is selected and stopped, are other threads allowed
37342 @c to continue to execute? As I mentioned above, I think the
37343 @c semantics of each command when a thread is selected must be
37344 @c described. For example:
37346 @c 'g': If the stub supports threads and a specific thread is
37347 @c selected, returns the register block from that thread;
37348 @c otherwise returns current registers.
37350 @c 'G' If the stub supports threads and a specific thread is
37351 @c selected, sets the registers of the register block of
37352 @c that thread; otherwise sets current registers.
37354 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
37355 @anchor{cycle step packet}
37356 @cindex @samp{i} packet
37357 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
37358 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
37359 step starting at that address.
37362 @cindex @samp{I} packet
37363 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
37367 @cindex @samp{k} packet
37370 The exact effect of this packet is not specified.
37372 For a bare-metal target, it may power cycle or reset the target
37373 system. For that reason, the @samp{k} packet has no reply.
37375 For a single-process target, it may kill that process if possible.
37377 A multiple-process target may choose to kill just one process, or all
37378 that are under @value{GDBN}'s control. For more precise control, use
37379 the vKill packet (@pxref{vKill packet}).
37381 If the target system immediately closes the connection in response to
37382 @samp{k}, @value{GDBN} does not consider the lack of packet
37383 acknowledgment to be an error, and assumes the kill was successful.
37385 If connected using @kbd{target extended-remote}, and the target does
37386 not close the connection in response to a kill request, @value{GDBN}
37387 probes the target state as if a new connection was opened
37388 (@pxref{? packet}).
37390 @item m @var{addr},@var{length}
37391 @cindex @samp{m} packet
37392 Read @var{length} addressable memory units starting at address @var{addr}
37393 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
37394 any particular boundary.
37396 The stub need not use any particular size or alignment when gathering
37397 data from memory for the response; even if @var{addr} is word-aligned
37398 and @var{length} is a multiple of the word size, the stub is free to
37399 use byte accesses, or not. For this reason, this packet may not be
37400 suitable for accessing memory-mapped I/O devices.
37401 @cindex alignment of remote memory accesses
37402 @cindex size of remote memory accesses
37403 @cindex memory, alignment and size of remote accesses
37407 @item @var{XX@dots{}}
37408 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
37409 The reply may contain fewer addressable memory units than requested if the
37410 server was able to read only part of the region of memory.
37415 @item M @var{addr},@var{length}:@var{XX@dots{}}
37416 @cindex @samp{M} packet
37417 Write @var{length} addressable memory units starting at address @var{addr}
37418 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
37419 byte is transmitted as a two-digit hexadecimal number.
37426 for an error (this includes the case where only part of the data was
37431 @cindex @samp{p} packet
37432 Read the value of register @var{n}; @var{n} is in hex.
37433 @xref{read registers packet}, for a description of how the returned
37434 register value is encoded.
37438 @item @var{XX@dots{}}
37439 the register's value
37443 Indicating an unrecognized @var{query}.
37446 @item P @var{n@dots{}}=@var{r@dots{}}
37447 @anchor{write register packet}
37448 @cindex @samp{P} packet
37449 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
37450 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
37451 digits for each byte in the register (target byte order).
37461 @item q @var{name} @var{params}@dots{}
37462 @itemx Q @var{name} @var{params}@dots{}
37463 @cindex @samp{q} packet
37464 @cindex @samp{Q} packet
37465 General query (@samp{q}) and set (@samp{Q}). These packets are
37466 described fully in @ref{General Query Packets}.
37469 @cindex @samp{r} packet
37470 Reset the entire system.
37472 Don't use this packet; use the @samp{R} packet instead.
37475 @cindex @samp{R} packet
37476 Restart the program being debugged. The @var{XX}, while needed, is ignored.
37477 This packet is only available in extended mode (@pxref{extended mode}).
37479 The @samp{R} packet has no reply.
37481 @item s @r{[}@var{addr}@r{]}
37482 @cindex @samp{s} packet
37483 Single step, resuming at @var{addr}. If
37484 @var{addr} is omitted, resume at same address.
37486 This packet is deprecated for multi-threading support. @xref{vCont
37490 @xref{Stop Reply Packets}, for the reply specifications.
37492 @item S @var{sig}@r{[};@var{addr}@r{]}
37493 @anchor{step with signal packet}
37494 @cindex @samp{S} packet
37495 Step with signal. This is analogous to the @samp{C} packet, but
37496 requests a single-step, rather than a normal resumption of execution.
37498 This packet is deprecated for multi-threading support. @xref{vCont
37502 @xref{Stop Reply Packets}, for the reply specifications.
37504 @item t @var{addr}:@var{PP},@var{MM}
37505 @cindex @samp{t} packet
37506 Search backwards starting at address @var{addr} for a match with pattern
37507 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
37508 There must be at least 3 digits in @var{addr}.
37510 @item T @var{thread-id}
37511 @cindex @samp{T} packet
37512 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
37517 thread is still alive
37523 Packets starting with @samp{v} are identified by a multi-letter name,
37524 up to the first @samp{;} or @samp{?} (or the end of the packet).
37526 @item vAttach;@var{pid}
37527 @cindex @samp{vAttach} packet
37528 Attach to a new process with the specified process ID @var{pid}.
37529 The process ID is a
37530 hexadecimal integer identifying the process. In all-stop mode, all
37531 threads in the attached process are stopped; in non-stop mode, it may be
37532 attached without being stopped if that is supported by the target.
37534 @c In non-stop mode, on a successful vAttach, the stub should set the
37535 @c current thread to a thread of the newly-attached process. After
37536 @c attaching, GDB queries for the attached process's thread ID with qC.
37537 @c Also note that, from a user perspective, whether or not the
37538 @c target is stopped on attach in non-stop mode depends on whether you
37539 @c use the foreground or background version of the attach command, not
37540 @c on what vAttach does; GDB does the right thing with respect to either
37541 @c stopping or restarting threads.
37543 This packet is only available in extended mode (@pxref{extended mode}).
37549 @item @r{Any stop packet}
37550 for success in all-stop mode (@pxref{Stop Reply Packets})
37552 for success in non-stop mode (@pxref{Remote Non-Stop})
37555 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
37556 @cindex @samp{vCont} packet
37557 @anchor{vCont packet}
37558 Resume the inferior, specifying different actions for each thread.
37560 For each inferior thread, the leftmost action with a matching
37561 @var{thread-id} is applied. Threads that don't match any action
37562 remain in their current state. Thread IDs are specified using the
37563 syntax described in @ref{thread-id syntax}. If multiprocess
37564 extensions (@pxref{multiprocess extensions}) are supported, actions
37565 can be specified to match all threads in a process by using the
37566 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
37567 @var{thread-id} matches all threads. Specifying no actions is an
37570 Currently supported actions are:
37576 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
37580 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
37583 @item r @var{start},@var{end}
37584 Step once, and then keep stepping as long as the thread stops at
37585 addresses between @var{start} (inclusive) and @var{end} (exclusive).
37586 The remote stub reports a stop reply when either the thread goes out
37587 of the range or is stopped due to an unrelated reason, such as hitting
37588 a breakpoint. @xref{range stepping}.
37590 If the range is empty (@var{start} == @var{end}), then the action
37591 becomes equivalent to the @samp{s} action. In other words,
37592 single-step once, and report the stop (even if the stepped instruction
37593 jumps to @var{start}).
37595 (A stop reply may be sent at any point even if the PC is still within
37596 the stepping range; for example, it is valid to implement this packet
37597 in a degenerate way as a single instruction step operation.)
37601 The optional argument @var{addr} normally associated with the
37602 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
37603 not supported in @samp{vCont}.
37605 The @samp{t} action is only relevant in non-stop mode
37606 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
37607 A stop reply should be generated for any affected thread not already stopped.
37608 When a thread is stopped by means of a @samp{t} action,
37609 the corresponding stop reply should indicate that the thread has stopped with
37610 signal @samp{0}, regardless of whether the target uses some other signal
37611 as an implementation detail.
37613 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
37614 @samp{r} actions for threads that are already running. Conversely,
37615 the server must ignore @samp{t} actions for threads that are already
37618 @emph{Note:} In non-stop mode, a thread is considered running until
37619 @value{GDBN} acknowleges an asynchronous stop notification for it with
37620 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
37622 The stub must support @samp{vCont} if it reports support for
37623 multiprocess extensions (@pxref{multiprocess extensions}).
37626 @xref{Stop Reply Packets}, for the reply specifications.
37629 @cindex @samp{vCont?} packet
37630 Request a list of actions supported by the @samp{vCont} packet.
37634 @item vCont@r{[};@var{action}@dots{}@r{]}
37635 The @samp{vCont} packet is supported. Each @var{action} is a supported
37636 command in the @samp{vCont} packet.
37638 The @samp{vCont} packet is not supported.
37641 @anchor{vCtrlC packet}
37643 @cindex @samp{vCtrlC} packet
37644 Interrupt remote target as if a control-C was pressed on the remote
37645 terminal. This is the equivalent to reacting to the @code{^C}
37646 (@samp{\003}, the control-C character) character in all-stop mode
37647 while the target is running, except this works in non-stop mode.
37648 @xref{interrupting remote targets}, for more info on the all-stop
37659 @item vFile:@var{operation}:@var{parameter}@dots{}
37660 @cindex @samp{vFile} packet
37661 Perform a file operation on the target system. For details,
37662 see @ref{Host I/O Packets}.
37664 @item vFlashErase:@var{addr},@var{length}
37665 @cindex @samp{vFlashErase} packet
37666 Direct the stub to erase @var{length} bytes of flash starting at
37667 @var{addr}. The region may enclose any number of flash blocks, but
37668 its start and end must fall on block boundaries, as indicated by the
37669 flash block size appearing in the memory map (@pxref{Memory Map
37670 Format}). @value{GDBN} groups flash memory programming operations
37671 together, and sends a @samp{vFlashDone} request after each group; the
37672 stub is allowed to delay erase operation until the @samp{vFlashDone}
37673 packet is received.
37683 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
37684 @cindex @samp{vFlashWrite} packet
37685 Direct the stub to write data to flash address @var{addr}. The data
37686 is passed in binary form using the same encoding as for the @samp{X}
37687 packet (@pxref{Binary Data}). The memory ranges specified by
37688 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
37689 not overlap, and must appear in order of increasing addresses
37690 (although @samp{vFlashErase} packets for higher addresses may already
37691 have been received; the ordering is guaranteed only between
37692 @samp{vFlashWrite} packets). If a packet writes to an address that was
37693 neither erased by a preceding @samp{vFlashErase} packet nor by some other
37694 target-specific method, the results are unpredictable.
37702 for vFlashWrite addressing non-flash memory
37708 @cindex @samp{vFlashDone} packet
37709 Indicate to the stub that flash programming operation is finished.
37710 The stub is permitted to delay or batch the effects of a group of
37711 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
37712 @samp{vFlashDone} packet is received. The contents of the affected
37713 regions of flash memory are unpredictable until the @samp{vFlashDone}
37714 request is completed.
37716 @item vKill;@var{pid}
37717 @cindex @samp{vKill} packet
37718 @anchor{vKill packet}
37719 Kill the process with the specified process ID @var{pid}, which is a
37720 hexadecimal integer identifying the process. This packet is used in
37721 preference to @samp{k} when multiprocess protocol extensions are
37722 supported; see @ref{multiprocess extensions}.
37732 @item vMustReplyEmpty
37733 @cindex @samp{vMustReplyEmpty} packet
37734 The correct reply to an unknown @samp{v} packet is to return the empty
37735 string, however, some older versions of @command{gdbserver} would
37736 incorrectly return @samp{OK} for unknown @samp{v} packets.
37738 The @samp{vMustReplyEmpty} is used as a feature test to check how
37739 @command{gdbserver} handles unknown packets, it is important that this
37740 packet be handled in the same way as other unknown @samp{v} packets.
37741 If this packet is handled differently to other unknown @samp{v}
37742 packets then it is possile that @value{GDBN} may run into problems in
37743 other areas, specifically around use of @samp{vFile:setfs:}.
37745 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
37746 @cindex @samp{vRun} packet
37747 Run the program @var{filename}, passing it each @var{argument} on its
37748 command line. The file and arguments are hex-encoded strings. If
37749 @var{filename} is an empty string, the stub may use a default program
37750 (e.g.@: the last program run). The program is created in the stopped
37753 @c FIXME: What about non-stop mode?
37755 This packet is only available in extended mode (@pxref{extended mode}).
37761 @item @r{Any stop packet}
37762 for success (@pxref{Stop Reply Packets})
37766 @cindex @samp{vStopped} packet
37767 @xref{Notification Packets}.
37769 @item X @var{addr},@var{length}:@var{XX@dots{}}
37771 @cindex @samp{X} packet
37772 Write data to memory, where the data is transmitted in binary.
37773 Memory is specified by its address @var{addr} and number of addressable memory
37774 units @var{length} (@pxref{addressable memory unit});
37775 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
37785 @item z @var{type},@var{addr},@var{kind}
37786 @itemx Z @var{type},@var{addr},@var{kind}
37787 @anchor{insert breakpoint or watchpoint packet}
37788 @cindex @samp{z} packet
37789 @cindex @samp{Z} packets
37790 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
37791 watchpoint starting at address @var{address} of kind @var{kind}.
37793 Each breakpoint and watchpoint packet @var{type} is documented
37796 @emph{Implementation notes: A remote target shall return an empty string
37797 for an unrecognized breakpoint or watchpoint packet @var{type}. A
37798 remote target shall support either both or neither of a given
37799 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
37800 avoid potential problems with duplicate packets, the operations should
37801 be implemented in an idempotent way.}
37803 @item z0,@var{addr},@var{kind}
37804 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37805 @cindex @samp{z0} packet
37806 @cindex @samp{Z0} packet
37807 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
37808 @var{addr} of type @var{kind}.
37810 A software breakpoint is implemented by replacing the instruction at
37811 @var{addr} with a software breakpoint or trap instruction. The
37812 @var{kind} is target-specific and typically indicates the size of the
37813 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
37814 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
37815 architectures have additional meanings for @var{kind}
37816 (@pxref{Architecture-Specific Protocol Details}); if no
37817 architecture-specific value is being used, it should be @samp{0}.
37818 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
37819 conditional expressions in bytecode form that should be evaluated on
37820 the target's side. These are the conditions that should be taken into
37821 consideration when deciding if the breakpoint trigger should be
37822 reported back to @value{GDBN}.
37824 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
37825 for how to best report a software breakpoint event to @value{GDBN}.
37827 The @var{cond_list} parameter is comprised of a series of expressions,
37828 concatenated without separators. Each expression has the following form:
37832 @item X @var{len},@var{expr}
37833 @var{len} is the length of the bytecode expression and @var{expr} is the
37834 actual conditional expression in bytecode form.
37838 The optional @var{cmd_list} parameter introduces commands that may be
37839 run on the target, rather than being reported back to @value{GDBN}.
37840 The parameter starts with a numeric flag @var{persist}; if the flag is
37841 nonzero, then the breakpoint may remain active and the commands
37842 continue to be run even when @value{GDBN} disconnects from the target.
37843 Following this flag is a series of expressions concatenated with no
37844 separators. Each expression has the following form:
37848 @item X @var{len},@var{expr}
37849 @var{len} is the length of the bytecode expression and @var{expr} is the
37850 actual commands expression in bytecode form.
37854 @emph{Implementation note: It is possible for a target to copy or move
37855 code that contains software breakpoints (e.g., when implementing
37856 overlays). The behavior of this packet, in the presence of such a
37857 target, is not defined.}
37869 @item z1,@var{addr},@var{kind}
37870 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37871 @cindex @samp{z1} packet
37872 @cindex @samp{Z1} packet
37873 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
37874 address @var{addr}.
37876 A hardware breakpoint is implemented using a mechanism that is not
37877 dependent on being able to modify the target's memory. The
37878 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
37879 same meaning as in @samp{Z0} packets.
37881 @emph{Implementation note: A hardware breakpoint is not affected by code
37894 @item z2,@var{addr},@var{kind}
37895 @itemx Z2,@var{addr},@var{kind}
37896 @cindex @samp{z2} packet
37897 @cindex @samp{Z2} packet
37898 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
37899 The number of bytes to watch is specified by @var{kind}.
37911 @item z3,@var{addr},@var{kind}
37912 @itemx Z3,@var{addr},@var{kind}
37913 @cindex @samp{z3} packet
37914 @cindex @samp{Z3} packet
37915 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
37916 The number of bytes to watch is specified by @var{kind}.
37928 @item z4,@var{addr},@var{kind}
37929 @itemx Z4,@var{addr},@var{kind}
37930 @cindex @samp{z4} packet
37931 @cindex @samp{Z4} packet
37932 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
37933 The number of bytes to watch is specified by @var{kind}.
37947 @node Stop Reply Packets
37948 @section Stop Reply Packets
37949 @cindex stop reply packets
37951 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
37952 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
37953 receive any of the below as a reply. Except for @samp{?}
37954 and @samp{vStopped}, that reply is only returned
37955 when the target halts. In the below the exact meaning of @dfn{signal
37956 number} is defined by the header @file{include/gdb/signals.h} in the
37957 @value{GDBN} source code.
37959 In non-stop mode, the server will simply reply @samp{OK} to commands
37960 such as @samp{vCont}; any stop will be the subject of a future
37961 notification. @xref{Remote Non-Stop}.
37963 As in the description of request packets, we include spaces in the
37964 reply templates for clarity; these are not part of the reply packet's
37965 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
37971 The program received signal number @var{AA} (a two-digit hexadecimal
37972 number). This is equivalent to a @samp{T} response with no
37973 @var{n}:@var{r} pairs.
37975 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
37976 @cindex @samp{T} packet reply
37977 The program received signal number @var{AA} (a two-digit hexadecimal
37978 number). This is equivalent to an @samp{S} response, except that the
37979 @samp{@var{n}:@var{r}} pairs can carry values of important registers
37980 and other information directly in the stop reply packet, reducing
37981 round-trip latency. Single-step and breakpoint traps are reported
37982 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
37986 If @var{n} is a hexadecimal number, it is a register number, and the
37987 corresponding @var{r} gives that register's value. The data @var{r} is a
37988 series of bytes in target byte order, with each byte given by a
37989 two-digit hex number.
37992 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
37993 the stopped thread, as specified in @ref{thread-id syntax}.
37996 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
37997 the core on which the stop event was detected.
38000 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38001 specific event that stopped the target. The currently defined stop
38002 reasons are listed below. The @var{aa} should be @samp{05}, the trap
38003 signal. At most one stop reason should be present.
38006 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38007 and go on to the next; this allows us to extend the protocol in the
38011 The currently defined stop reasons are:
38017 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38020 @item syscall_entry
38021 @itemx syscall_return
38022 The packet indicates a syscall entry or return, and @var{r} is the
38023 syscall number, in hex.
38025 @cindex shared library events, remote reply
38027 The packet indicates that the loaded libraries have changed.
38028 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38029 list of loaded libraries. The @var{r} part is ignored.
38031 @cindex replay log events, remote reply
38033 The packet indicates that the target cannot continue replaying
38034 logged execution events, because it has reached the end (or the
38035 beginning when executing backward) of the log. The value of @var{r}
38036 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38037 for more information.
38040 @anchor{swbreak stop reason}
38041 The packet indicates a software breakpoint instruction was executed,
38042 irrespective of whether it was @value{GDBN} that planted the
38043 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
38044 part must be left empty.
38046 On some architectures, such as x86, at the architecture level, when a
38047 breakpoint instruction executes the program counter points at the
38048 breakpoint address plus an offset. On such targets, the stub is
38049 responsible for adjusting the PC to point back at the breakpoint
38052 This packet should not be sent by default; older @value{GDBN} versions
38053 did not support it. @value{GDBN} requests it, by supplying an
38054 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38055 remote stub must also supply the appropriate @samp{qSupported} feature
38056 indicating support.
38058 This packet is required for correct non-stop mode operation.
38061 The packet indicates the target stopped for a hardware breakpoint.
38062 The @var{r} part must be left empty.
38064 The same remarks about @samp{qSupported} and non-stop mode above
38067 @cindex fork events, remote reply
38069 The packet indicates that @code{fork} was called, and @var{r}
38070 is the thread ID of the new child process. Refer to
38071 @ref{thread-id syntax} for the format of the @var{thread-id}
38072 field. This packet is only applicable to targets that support
38075 This packet should not be sent by default; older @value{GDBN} versions
38076 did not support it. @value{GDBN} requests it, by supplying an
38077 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38078 remote stub must also supply the appropriate @samp{qSupported} feature
38079 indicating support.
38081 @cindex vfork events, remote reply
38083 The packet indicates that @code{vfork} was called, and @var{r}
38084 is the thread ID of the new child process. Refer to
38085 @ref{thread-id syntax} for the format of the @var{thread-id}
38086 field. This packet is only applicable to targets that support
38089 This packet should not be sent by default; older @value{GDBN} versions
38090 did not support it. @value{GDBN} requests it, by supplying an
38091 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38092 remote stub must also supply the appropriate @samp{qSupported} feature
38093 indicating support.
38095 @cindex vforkdone events, remote reply
38097 The packet indicates that a child process created by a vfork
38098 has either called @code{exec} or terminated, so that the
38099 address spaces of the parent and child process are no longer
38100 shared. The @var{r} part is ignored. This packet is only
38101 applicable to targets that support vforkdone events.
38103 This packet should not be sent by default; older @value{GDBN} versions
38104 did not support it. @value{GDBN} requests it, by supplying an
38105 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38106 remote stub must also supply the appropriate @samp{qSupported} feature
38107 indicating support.
38109 @cindex exec events, remote reply
38111 The packet indicates that @code{execve} was called, and @var{r}
38112 is the absolute pathname of the file that was executed, in hex.
38113 This packet is only applicable to targets that support exec events.
38115 This packet should not be sent by default; older @value{GDBN} versions
38116 did not support it. @value{GDBN} requests it, by supplying an
38117 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38118 remote stub must also supply the appropriate @samp{qSupported} feature
38119 indicating support.
38121 @cindex thread create event, remote reply
38122 @anchor{thread create event}
38124 The packet indicates that the thread was just created. The new thread
38125 is stopped until @value{GDBN} sets it running with a resumption packet
38126 (@pxref{vCont packet}). This packet should not be sent by default;
38127 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
38128 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
38129 @var{r} part is ignored.
38134 @itemx W @var{AA} ; process:@var{pid}
38135 The process exited, and @var{AA} is the exit status. This is only
38136 applicable to certain targets.
38138 The second form of the response, including the process ID of the
38139 exited process, can be used only when @value{GDBN} has reported
38140 support for multiprocess protocol extensions; see @ref{multiprocess
38141 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
38145 @itemx X @var{AA} ; process:@var{pid}
38146 The process terminated with signal @var{AA}.
38148 The second form of the response, including the process ID of the
38149 terminated process, can be used only when @value{GDBN} has reported
38150 support for multiprocess protocol extensions; see @ref{multiprocess
38151 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
38154 @anchor{thread exit event}
38155 @cindex thread exit event, remote reply
38156 @item w @var{AA} ; @var{tid}
38158 The thread exited, and @var{AA} is the exit status. This response
38159 should not be sent by default; @value{GDBN} requests it with the
38160 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
38161 @var{AA} is formatted as a big-endian hex string.
38164 There are no resumed threads left in the target. In other words, even
38165 though the process is alive, the last resumed thread has exited. For
38166 example, say the target process has two threads: thread 1 and thread
38167 2. The client leaves thread 1 stopped, and resumes thread 2, which
38168 subsequently exits. At this point, even though the process is still
38169 alive, and thus no @samp{W} stop reply is sent, no thread is actually
38170 executing either. The @samp{N} stop reply thus informs the client
38171 that it can stop waiting for stop replies. This packet should not be
38172 sent by default; older @value{GDBN} versions did not support it.
38173 @value{GDBN} requests it, by supplying an appropriate
38174 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
38175 also supply the appropriate @samp{qSupported} feature indicating
38178 @item O @var{XX}@dots{}
38179 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38180 written as the program's console output. This can happen at any time
38181 while the program is running and the debugger should continue to wait
38182 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38184 @item F @var{call-id},@var{parameter}@dots{}
38185 @var{call-id} is the identifier which says which host system call should
38186 be called. This is just the name of the function. Translation into the
38187 correct system call is only applicable as it's defined in @value{GDBN}.
38188 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38191 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38192 this very system call.
38194 The target replies with this packet when it expects @value{GDBN} to
38195 call a host system call on behalf of the target. @value{GDBN} replies
38196 with an appropriate @samp{F} packet and keeps up waiting for the next
38197 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38198 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38199 Protocol Extension}, for more details.
38203 @node General Query Packets
38204 @section General Query Packets
38205 @cindex remote query requests
38207 Packets starting with @samp{q} are @dfn{general query packets};
38208 packets starting with @samp{Q} are @dfn{general set packets}. General
38209 query and set packets are a semi-unified form for retrieving and
38210 sending information to and from the stub.
38212 The initial letter of a query or set packet is followed by a name
38213 indicating what sort of thing the packet applies to. For example,
38214 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38215 definitions with the stub. These packet names follow some
38220 The name must not contain commas, colons or semicolons.
38222 Most @value{GDBN} query and set packets have a leading upper case
38225 The names of custom vendor packets should use a company prefix, in
38226 lower case, followed by a period. For example, packets designed at
38227 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38228 foos) or @samp{Qacme.bar} (for setting bars).
38231 The name of a query or set packet should be separated from any
38232 parameters by a @samp{:}; the parameters themselves should be
38233 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38234 full packet name, and check for a separator or the end of the packet,
38235 in case two packet names share a common prefix. New packets should not begin
38236 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38237 packets predate these conventions, and have arguments without any terminator
38238 for the packet name; we suspect they are in widespread use in places that
38239 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38240 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38243 Like the descriptions of the other packets, each description here
38244 has a template showing the packet's overall syntax, followed by an
38245 explanation of the packet's meaning. We include spaces in some of the
38246 templates for clarity; these are not part of the packet's syntax. No
38247 @value{GDBN} packet uses spaces to separate its components.
38249 Here are the currently defined query and set packets:
38255 Turn on or off the agent as a helper to perform some debugging operations
38256 delegated from @value{GDBN} (@pxref{Control Agent}).
38258 @item QAllow:@var{op}:@var{val}@dots{}
38259 @cindex @samp{QAllow} packet
38260 Specify which operations @value{GDBN} expects to request of the
38261 target, as a semicolon-separated list of operation name and value
38262 pairs. Possible values for @var{op} include @samp{WriteReg},
38263 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38264 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38265 indicating that @value{GDBN} will not request the operation, or 1,
38266 indicating that it may. (The target can then use this to set up its
38267 own internals optimally, for instance if the debugger never expects to
38268 insert breakpoints, it may not need to install its own trap handler.)
38271 @cindex current thread, remote request
38272 @cindex @samp{qC} packet
38273 Return the current thread ID.
38277 @item QC @var{thread-id}
38278 Where @var{thread-id} is a thread ID as documented in
38279 @ref{thread-id syntax}.
38280 @item @r{(anything else)}
38281 Any other reply implies the old thread ID.
38284 @item qCRC:@var{addr},@var{length}
38285 @cindex CRC of memory block, remote request
38286 @cindex @samp{qCRC} packet
38287 @anchor{qCRC packet}
38288 Compute the CRC checksum of a block of memory using CRC-32 defined in
38289 IEEE 802.3. The CRC is computed byte at a time, taking the most
38290 significant bit of each byte first. The initial pattern code
38291 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
38293 @emph{Note:} This is the same CRC used in validating separate debug
38294 files (@pxref{Separate Debug Files, , Debugging Information in Separate
38295 Files}). However the algorithm is slightly different. When validating
38296 separate debug files, the CRC is computed taking the @emph{least}
38297 significant bit of each byte first, and the final result is inverted to
38298 detect trailing zeros.
38303 An error (such as memory fault)
38304 @item C @var{crc32}
38305 The specified memory region's checksum is @var{crc32}.
38308 @item QDisableRandomization:@var{value}
38309 @cindex disable address space randomization, remote request
38310 @cindex @samp{QDisableRandomization} packet
38311 Some target operating systems will randomize the virtual address space
38312 of the inferior process as a security feature, but provide a feature
38313 to disable such randomization, e.g.@: to allow for a more deterministic
38314 debugging experience. On such systems, this packet with a @var{value}
38315 of 1 directs the target to disable address space randomization for
38316 processes subsequently started via @samp{vRun} packets, while a packet
38317 with a @var{value} of 0 tells the target to enable address space
38320 This packet is only available in extended mode (@pxref{extended mode}).
38325 The request succeeded.
38328 An error occurred. The error number @var{nn} is given as hex digits.
38331 An empty reply indicates that @samp{QDisableRandomization} is not supported
38335 This packet is not probed by default; the remote stub must request it,
38336 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38337 This should only be done on targets that actually support disabling
38338 address space randomization.
38340 @item QStartupWithShell:@var{value}
38341 @cindex startup with shell, remote request
38342 @cindex @samp{QStartupWithShell} packet
38343 On UNIX-like targets, it is possible to start the inferior using a
38344 shell program. This is the default behavior on both @value{GDBN} and
38345 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
38346 used to inform @command{gdbserver} whether it should start the
38347 inferior using a shell or not.
38349 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
38350 to start the inferior. If @var{value} is @samp{1},
38351 @command{gdbserver} will use a shell to start the inferior. All other
38352 values are considered an error.
38354 This packet is only available in extended mode (@pxref{extended
38360 The request succeeded.
38363 An error occurred. The error number @var{nn} is given as hex digits.
38366 This packet is not probed by default; the remote stub must request it,
38367 by supplying an appropriate @samp{qSupported} response
38368 (@pxref{qSupported}). This should only be done on targets that
38369 actually support starting the inferior using a shell.
38371 Use of this packet is controlled by the @code{set startup-with-shell}
38372 command; @pxref{set startup-with-shell}.
38374 @item QEnvironmentHexEncoded:@var{hex-value}
38375 @anchor{QEnvironmentHexEncoded}
38376 @cindex set environment variable, remote request
38377 @cindex @samp{QEnvironmentHexEncoded} packet
38378 On UNIX-like targets, it is possible to set environment variables that
38379 will be passed to the inferior during the startup process. This
38380 packet is used to inform @command{gdbserver} of an environment
38381 variable that has been defined by the user on @value{GDBN} (@pxref{set
38384 The packet is composed by @var{hex-value}, an hex encoded
38385 representation of the @var{name=value} format representing an
38386 environment variable. The name of the environment variable is
38387 represented by @var{name}, and the value to be assigned to the
38388 environment variable is represented by @var{value}. If the variable
38389 has no value (i.e., the value is @code{null}), then @var{value} will
38392 This packet is only available in extended mode (@pxref{extended
38398 The request succeeded.
38401 This packet is not probed by default; the remote stub must request it,
38402 by supplying an appropriate @samp{qSupported} response
38403 (@pxref{qSupported}). This should only be done on targets that
38404 actually support passing environment variables to the starting
38407 This packet is related to the @code{set environment} command;
38408 @pxref{set environment}.
38410 @item QEnvironmentUnset:@var{hex-value}
38411 @anchor{QEnvironmentUnset}
38412 @cindex unset environment variable, remote request
38413 @cindex @samp{QEnvironmentUnset} packet
38414 On UNIX-like targets, it is possible to unset environment variables
38415 before starting the inferior in the remote target. This packet is
38416 used to inform @command{gdbserver} of an environment variable that has
38417 been unset by the user on @value{GDBN} (@pxref{unset environment}).
38419 The packet is composed by @var{hex-value}, an hex encoded
38420 representation of the name of the environment variable to be unset.
38422 This packet is only available in extended mode (@pxref{extended
38428 The request succeeded.
38431 This packet is not probed by default; the remote stub must request it,
38432 by supplying an appropriate @samp{qSupported} response
38433 (@pxref{qSupported}). This should only be done on targets that
38434 actually support passing environment variables to the starting
38437 This packet is related to the @code{unset environment} command;
38438 @pxref{unset environment}.
38440 @item QEnvironmentReset
38441 @anchor{QEnvironmentReset}
38442 @cindex reset environment, remote request
38443 @cindex @samp{QEnvironmentReset} packet
38444 On UNIX-like targets, this packet is used to reset the state of
38445 environment variables in the remote target before starting the
38446 inferior. In this context, reset means unsetting all environment
38447 variables that were previously set by the user (i.e., were not
38448 initially present in the environment). It is sent to
38449 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
38450 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
38451 (@pxref{QEnvironmentUnset}) packets.
38453 This packet is only available in extended mode (@pxref{extended
38459 The request succeeded.
38462 This packet is not probed by default; the remote stub must request it,
38463 by supplying an appropriate @samp{qSupported} response
38464 (@pxref{qSupported}). This should only be done on targets that
38465 actually support passing environment variables to the starting
38468 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
38469 @anchor{QSetWorkingDir packet}
38470 @cindex set working directory, remote request
38471 @cindex @samp{QSetWorkingDir} packet
38472 This packet is used to inform the remote server of the intended
38473 current working directory for programs that are going to be executed.
38475 The packet is composed by @var{directory}, an hex encoded
38476 representation of the directory that the remote inferior will use as
38477 its current working directory. If @var{directory} is an empty string,
38478 the remote server should reset the inferior's current working
38479 directory to its original, empty value.
38481 This packet is only available in extended mode (@pxref{extended
38487 The request succeeded.
38491 @itemx qsThreadInfo
38492 @cindex list active threads, remote request
38493 @cindex @samp{qfThreadInfo} packet
38494 @cindex @samp{qsThreadInfo} packet
38495 Obtain a list of all active thread IDs from the target (OS). Since there
38496 may be too many active threads to fit into one reply packet, this query
38497 works iteratively: it may require more than one query/reply sequence to
38498 obtain the entire list of threads. The first query of the sequence will
38499 be the @samp{qfThreadInfo} query; subsequent queries in the
38500 sequence will be the @samp{qsThreadInfo} query.
38502 NOTE: This packet replaces the @samp{qL} query (see below).
38506 @item m @var{thread-id}
38508 @item m @var{thread-id},@var{thread-id}@dots{}
38509 a comma-separated list of thread IDs
38511 (lower case letter @samp{L}) denotes end of list.
38514 In response to each query, the target will reply with a list of one or
38515 more thread IDs, separated by commas.
38516 @value{GDBN} will respond to each reply with a request for more thread
38517 ids (using the @samp{qs} form of the query), until the target responds
38518 with @samp{l} (lower-case ell, for @dfn{last}).
38519 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
38522 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
38523 initial connection with the remote target, and the very first thread ID
38524 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
38525 message. Therefore, the stub should ensure that the first thread ID in
38526 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
38528 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
38529 @cindex get thread-local storage address, remote request
38530 @cindex @samp{qGetTLSAddr} packet
38531 Fetch the address associated with thread local storage specified
38532 by @var{thread-id}, @var{offset}, and @var{lm}.
38534 @var{thread-id} is the thread ID associated with the
38535 thread for which to fetch the TLS address. @xref{thread-id syntax}.
38537 @var{offset} is the (big endian, hex encoded) offset associated with the
38538 thread local variable. (This offset is obtained from the debug
38539 information associated with the variable.)
38541 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
38542 load module associated with the thread local storage. For example,
38543 a @sc{gnu}/Linux system will pass the link map address of the shared
38544 object associated with the thread local storage under consideration.
38545 Other operating environments may choose to represent the load module
38546 differently, so the precise meaning of this parameter will vary.
38550 @item @var{XX}@dots{}
38551 Hex encoded (big endian) bytes representing the address of the thread
38552 local storage requested.
38555 An error occurred. The error number @var{nn} is given as hex digits.
38558 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
38561 @item qGetTIBAddr:@var{thread-id}
38562 @cindex get thread information block address
38563 @cindex @samp{qGetTIBAddr} packet
38564 Fetch address of the Windows OS specific Thread Information Block.
38566 @var{thread-id} is the thread ID associated with the thread.
38570 @item @var{XX}@dots{}
38571 Hex encoded (big endian) bytes representing the linear address of the
38572 thread information block.
38575 An error occured. This means that either the thread was not found, or the
38576 address could not be retrieved.
38579 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
38582 @item qL @var{startflag} @var{threadcount} @var{nextthread}
38583 Obtain thread information from RTOS. Where: @var{startflag} (one hex
38584 digit) is one to indicate the first query and zero to indicate a
38585 subsequent query; @var{threadcount} (two hex digits) is the maximum
38586 number of threads the response packet can contain; and @var{nextthread}
38587 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
38588 returned in the response as @var{argthread}.
38590 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
38594 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
38595 Where: @var{count} (two hex digits) is the number of threads being
38596 returned; @var{done} (one hex digit) is zero to indicate more threads
38597 and one indicates no further threads; @var{argthreadid} (eight hex
38598 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
38599 is a sequence of thread IDs, @var{threadid} (eight hex
38600 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
38604 @cindex section offsets, remote request
38605 @cindex @samp{qOffsets} packet
38606 Get section offsets that the target used when relocating the downloaded
38611 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
38612 Relocate the @code{Text} section by @var{xxx} from its original address.
38613 Relocate the @code{Data} section by @var{yyy} from its original address.
38614 If the object file format provides segment information (e.g.@: @sc{elf}
38615 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
38616 segments by the supplied offsets.
38618 @emph{Note: while a @code{Bss} offset may be included in the response,
38619 @value{GDBN} ignores this and instead applies the @code{Data} offset
38620 to the @code{Bss} section.}
38622 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
38623 Relocate the first segment of the object file, which conventionally
38624 contains program code, to a starting address of @var{xxx}. If
38625 @samp{DataSeg} is specified, relocate the second segment, which
38626 conventionally contains modifiable data, to a starting address of
38627 @var{yyy}. @value{GDBN} will report an error if the object file
38628 does not contain segment information, or does not contain at least
38629 as many segments as mentioned in the reply. Extra segments are
38630 kept at fixed offsets relative to the last relocated segment.
38633 @item qP @var{mode} @var{thread-id}
38634 @cindex thread information, remote request
38635 @cindex @samp{qP} packet
38636 Returns information on @var{thread-id}. Where: @var{mode} is a hex
38637 encoded 32 bit mode; @var{thread-id} is a thread ID
38638 (@pxref{thread-id syntax}).
38640 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
38643 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
38647 @cindex non-stop mode, remote request
38648 @cindex @samp{QNonStop} packet
38650 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
38651 @xref{Remote Non-Stop}, for more information.
38656 The request succeeded.
38659 An error occurred. The error number @var{nn} is given as hex digits.
38662 An empty reply indicates that @samp{QNonStop} is not supported by
38666 This packet is not probed by default; the remote stub must request it,
38667 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38668 Use of this packet is controlled by the @code{set non-stop} command;
38669 @pxref{Non-Stop Mode}.
38671 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
38672 @itemx QCatchSyscalls:0
38673 @cindex catch syscalls from inferior, remote request
38674 @cindex @samp{QCatchSyscalls} packet
38675 @anchor{QCatchSyscalls}
38676 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
38677 catching syscalls from the inferior process.
38679 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
38680 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
38681 is listed, every system call should be reported.
38683 Note that if a syscall not in the list is reported, @value{GDBN} will
38684 still filter the event according to its own list from all corresponding
38685 @code{catch syscall} commands. However, it is more efficient to only
38686 report the requested syscalls.
38688 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
38689 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
38691 If the inferior process execs, the state of @samp{QCatchSyscalls} is
38692 kept for the new process too. On targets where exec may affect syscall
38693 numbers, for example with exec between 32 and 64-bit processes, the
38694 client should send a new packet with the new syscall list.
38699 The request succeeded.
38702 An error occurred. @var{nn} are hex digits.
38705 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
38709 Use of this packet is controlled by the @code{set remote catch-syscalls}
38710 command (@pxref{Remote Configuration, set remote catch-syscalls}).
38711 This packet is not probed by default; the remote stub must request it,
38712 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38714 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38715 @cindex pass signals to inferior, remote request
38716 @cindex @samp{QPassSignals} packet
38717 @anchor{QPassSignals}
38718 Each listed @var{signal} should be passed directly to the inferior process.
38719 Signals are numbered identically to continue packets and stop replies
38720 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38721 strictly greater than the previous item. These signals do not need to stop
38722 the inferior, or be reported to @value{GDBN}. All other signals should be
38723 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
38724 combine; any earlier @samp{QPassSignals} list is completely replaced by the
38725 new list. This packet improves performance when using @samp{handle
38726 @var{signal} nostop noprint pass}.
38731 The request succeeded.
38734 An error occurred. The error number @var{nn} is given as hex digits.
38737 An empty reply indicates that @samp{QPassSignals} is not supported by
38741 Use of this packet is controlled by the @code{set remote pass-signals}
38742 command (@pxref{Remote Configuration, set remote pass-signals}).
38743 This packet is not probed by default; the remote stub must request it,
38744 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38746 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38747 @cindex signals the inferior may see, remote request
38748 @cindex @samp{QProgramSignals} packet
38749 @anchor{QProgramSignals}
38750 Each listed @var{signal} may be delivered to the inferior process.
38751 Others should be silently discarded.
38753 In some cases, the remote stub may need to decide whether to deliver a
38754 signal to the program or not without @value{GDBN} involvement. One
38755 example of that is while detaching --- the program's threads may have
38756 stopped for signals that haven't yet had a chance of being reported to
38757 @value{GDBN}, and so the remote stub can use the signal list specified
38758 by this packet to know whether to deliver or ignore those pending
38761 This does not influence whether to deliver a signal as requested by a
38762 resumption packet (@pxref{vCont packet}).
38764 Signals are numbered identically to continue packets and stop replies
38765 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38766 strictly greater than the previous item. Multiple
38767 @samp{QProgramSignals} packets do not combine; any earlier
38768 @samp{QProgramSignals} list is completely replaced by the new list.
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{QProgramSignals} is not supported
38783 Use of this packet is controlled by the @code{set remote program-signals}
38784 command (@pxref{Remote Configuration, set remote program-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 @anchor{QThreadEvents}
38789 @item QThreadEvents:1
38790 @itemx QThreadEvents:0
38791 @cindex thread create/exit events, remote request
38792 @cindex @samp{QThreadEvents} packet
38794 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
38795 reporting of thread create and exit events. @xref{thread create
38796 event}, for the reply specifications. For example, this is used in
38797 non-stop mode when @value{GDBN} stops a set of threads and
38798 synchronously waits for the their corresponding stop replies. Without
38799 exit events, if one of the threads exits, @value{GDBN} would hang
38800 forever not knowing that it should no longer expect a stop for that
38801 same thread. @value{GDBN} does not enable this feature unless the
38802 stub reports that it supports it by including @samp{QThreadEvents+} in
38803 its @samp{qSupported} reply.
38808 The request succeeded.
38811 An error occurred. The error number @var{nn} is given as hex digits.
38814 An empty reply indicates that @samp{QThreadEvents} is not supported by
38818 Use of this packet is controlled by the @code{set remote thread-events}
38819 command (@pxref{Remote Configuration, set remote thread-events}).
38821 @item qRcmd,@var{command}
38822 @cindex execute remote command, remote request
38823 @cindex @samp{qRcmd} packet
38824 @var{command} (hex encoded) is passed to the local interpreter for
38825 execution. Invalid commands should be reported using the output
38826 string. Before the final result packet, the target may also respond
38827 with a number of intermediate @samp{O@var{output}} console output
38828 packets. @emph{Implementors should note that providing access to a
38829 stubs's interpreter may have security implications}.
38834 A command response with no output.
38836 A command response with the hex encoded output string @var{OUTPUT}.
38838 Indicate a badly formed request.
38840 An empty reply indicates that @samp{qRcmd} is not recognized.
38843 (Note that the @code{qRcmd} packet's name is separated from the
38844 command by a @samp{,}, not a @samp{:}, contrary to the naming
38845 conventions above. Please don't use this packet as a model for new
38848 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
38849 @cindex searching memory, in remote debugging
38851 @cindex @samp{qSearch:memory} packet
38853 @cindex @samp{qSearch memory} packet
38854 @anchor{qSearch memory}
38855 Search @var{length} bytes at @var{address} for @var{search-pattern}.
38856 Both @var{address} and @var{length} are encoded in hex;
38857 @var{search-pattern} is a sequence of bytes, also hex encoded.
38862 The pattern was not found.
38864 The pattern was found at @var{address}.
38866 A badly formed request or an error was encountered while searching memory.
38868 An empty reply indicates that @samp{qSearch:memory} is not recognized.
38871 @item QStartNoAckMode
38872 @cindex @samp{QStartNoAckMode} packet
38873 @anchor{QStartNoAckMode}
38874 Request that the remote stub disable the normal @samp{+}/@samp{-}
38875 protocol acknowledgments (@pxref{Packet Acknowledgment}).
38880 The stub has switched to no-acknowledgment mode.
38881 @value{GDBN} acknowledges this reponse,
38882 but neither the stub nor @value{GDBN} shall send or expect further
38883 @samp{+}/@samp{-} acknowledgments in the current connection.
38885 An empty reply indicates that the stub does not support no-acknowledgment mode.
38888 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
38889 @cindex supported packets, remote query
38890 @cindex features of the remote protocol
38891 @cindex @samp{qSupported} packet
38892 @anchor{qSupported}
38893 Tell the remote stub about features supported by @value{GDBN}, and
38894 query the stub for features it supports. This packet allows
38895 @value{GDBN} and the remote stub to take advantage of each others'
38896 features. @samp{qSupported} also consolidates multiple feature probes
38897 at startup, to improve @value{GDBN} performance---a single larger
38898 packet performs better than multiple smaller probe packets on
38899 high-latency links. Some features may enable behavior which must not
38900 be on by default, e.g.@: because it would confuse older clients or
38901 stubs. Other features may describe packets which could be
38902 automatically probed for, but are not. These features must be
38903 reported before @value{GDBN} will use them. This ``default
38904 unsupported'' behavior is not appropriate for all packets, but it
38905 helps to keep the initial connection time under control with new
38906 versions of @value{GDBN} which support increasing numbers of packets.
38910 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
38911 The stub supports or does not support each returned @var{stubfeature},
38912 depending on the form of each @var{stubfeature} (see below for the
38915 An empty reply indicates that @samp{qSupported} is not recognized,
38916 or that no features needed to be reported to @value{GDBN}.
38919 The allowed forms for each feature (either a @var{gdbfeature} in the
38920 @samp{qSupported} packet, or a @var{stubfeature} in the response)
38924 @item @var{name}=@var{value}
38925 The remote protocol feature @var{name} is supported, and associated
38926 with the specified @var{value}. The format of @var{value} depends
38927 on the feature, but it must not include a semicolon.
38929 The remote protocol feature @var{name} is supported, and does not
38930 need an associated value.
38932 The remote protocol feature @var{name} is not supported.
38934 The remote protocol feature @var{name} may be supported, and
38935 @value{GDBN} should auto-detect support in some other way when it is
38936 needed. This form will not be used for @var{gdbfeature} notifications,
38937 but may be used for @var{stubfeature} responses.
38940 Whenever the stub receives a @samp{qSupported} request, the
38941 supplied set of @value{GDBN} features should override any previous
38942 request. This allows @value{GDBN} to put the stub in a known
38943 state, even if the stub had previously been communicating with
38944 a different version of @value{GDBN}.
38946 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
38951 This feature indicates whether @value{GDBN} supports multiprocess
38952 extensions to the remote protocol. @value{GDBN} does not use such
38953 extensions unless the stub also reports that it supports them by
38954 including @samp{multiprocess+} in its @samp{qSupported} reply.
38955 @xref{multiprocess extensions}, for details.
38958 This feature indicates that @value{GDBN} supports the XML target
38959 description. If the stub sees @samp{xmlRegisters=} with target
38960 specific strings separated by a comma, it will report register
38964 This feature indicates whether @value{GDBN} supports the
38965 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
38966 instruction reply packet}).
38969 This feature indicates whether @value{GDBN} supports the swbreak stop
38970 reason in stop replies. @xref{swbreak stop reason}, for details.
38973 This feature indicates whether @value{GDBN} supports the hwbreak stop
38974 reason in stop replies. @xref{swbreak stop reason}, for details.
38977 This feature indicates whether @value{GDBN} supports fork event
38978 extensions to the remote protocol. @value{GDBN} does not use such
38979 extensions unless the stub also reports that it supports them by
38980 including @samp{fork-events+} in its @samp{qSupported} reply.
38983 This feature indicates whether @value{GDBN} supports vfork event
38984 extensions to the remote protocol. @value{GDBN} does not use such
38985 extensions unless the stub also reports that it supports them by
38986 including @samp{vfork-events+} in its @samp{qSupported} reply.
38989 This feature indicates whether @value{GDBN} supports exec event
38990 extensions to the remote protocol. @value{GDBN} does not use such
38991 extensions unless the stub also reports that it supports them by
38992 including @samp{exec-events+} in its @samp{qSupported} reply.
38994 @item vContSupported
38995 This feature indicates whether @value{GDBN} wants to know the
38996 supported actions in the reply to @samp{vCont?} packet.
38999 Stubs should ignore any unknown values for
39000 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
39001 packet supports receiving packets of unlimited length (earlier
39002 versions of @value{GDBN} may reject overly long responses). Additional values
39003 for @var{gdbfeature} may be defined in the future to let the stub take
39004 advantage of new features in @value{GDBN}, e.g.@: incompatible
39005 improvements in the remote protocol---the @samp{multiprocess} feature is
39006 an example of such a feature. The stub's reply should be independent
39007 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
39008 describes all the features it supports, and then the stub replies with
39009 all the features it supports.
39011 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
39012 responses, as long as each response uses one of the standard forms.
39014 Some features are flags. A stub which supports a flag feature
39015 should respond with a @samp{+} form response. Other features
39016 require values, and the stub should respond with an @samp{=}
39019 Each feature has a default value, which @value{GDBN} will use if
39020 @samp{qSupported} is not available or if the feature is not mentioned
39021 in the @samp{qSupported} response. The default values are fixed; a
39022 stub is free to omit any feature responses that match the defaults.
39024 Not all features can be probed, but for those which can, the probing
39025 mechanism is useful: in some cases, a stub's internal
39026 architecture may not allow the protocol layer to know some information
39027 about the underlying target in advance. This is especially common in
39028 stubs which may be configured for multiple targets.
39030 These are the currently defined stub features and their properties:
39032 @multitable @columnfractions 0.35 0.2 0.12 0.2
39033 @c NOTE: The first row should be @headitem, but we do not yet require
39034 @c a new enough version of Texinfo (4.7) to use @headitem.
39036 @tab Value Required
39040 @item @samp{PacketSize}
39045 @item @samp{qXfer:auxv:read}
39050 @item @samp{qXfer:btrace:read}
39055 @item @samp{qXfer:btrace-conf:read}
39060 @item @samp{qXfer:exec-file:read}
39065 @item @samp{qXfer:features:read}
39070 @item @samp{qXfer:libraries:read}
39075 @item @samp{qXfer:libraries-svr4:read}
39080 @item @samp{augmented-libraries-svr4-read}
39085 @item @samp{qXfer:memory-map:read}
39090 @item @samp{qXfer:sdata:read}
39095 @item @samp{qXfer:spu:read}
39100 @item @samp{qXfer:spu:write}
39105 @item @samp{qXfer:siginfo:read}
39110 @item @samp{qXfer:siginfo:write}
39115 @item @samp{qXfer:threads:read}
39120 @item @samp{qXfer:traceframe-info:read}
39125 @item @samp{qXfer:uib:read}
39130 @item @samp{qXfer:fdpic:read}
39135 @item @samp{Qbtrace:off}
39140 @item @samp{Qbtrace:bts}
39145 @item @samp{Qbtrace:pt}
39150 @item @samp{Qbtrace-conf:bts:size}
39155 @item @samp{Qbtrace-conf:pt:size}
39160 @item @samp{QNonStop}
39165 @item @samp{QCatchSyscalls}
39170 @item @samp{QPassSignals}
39175 @item @samp{QStartNoAckMode}
39180 @item @samp{multiprocess}
39185 @item @samp{ConditionalBreakpoints}
39190 @item @samp{ConditionalTracepoints}
39195 @item @samp{ReverseContinue}
39200 @item @samp{ReverseStep}
39205 @item @samp{TracepointSource}
39210 @item @samp{QAgent}
39215 @item @samp{QAllow}
39220 @item @samp{QDisableRandomization}
39225 @item @samp{EnableDisableTracepoints}
39230 @item @samp{QTBuffer:size}
39235 @item @samp{tracenz}
39240 @item @samp{BreakpointCommands}
39245 @item @samp{swbreak}
39250 @item @samp{hwbreak}
39255 @item @samp{fork-events}
39260 @item @samp{vfork-events}
39265 @item @samp{exec-events}
39270 @item @samp{QThreadEvents}
39275 @item @samp{no-resumed}
39282 These are the currently defined stub features, in more detail:
39285 @cindex packet size, remote protocol
39286 @item PacketSize=@var{bytes}
39287 The remote stub can accept packets up to at least @var{bytes} in
39288 length. @value{GDBN} will send packets up to this size for bulk
39289 transfers, and will never send larger packets. This is a limit on the
39290 data characters in the packet, including the frame and checksum.
39291 There is no trailing NUL byte in a remote protocol packet; if the stub
39292 stores packets in a NUL-terminated format, it should allow an extra
39293 byte in its buffer for the NUL. If this stub feature is not supported,
39294 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39296 @item qXfer:auxv:read
39297 The remote stub understands the @samp{qXfer:auxv:read} packet
39298 (@pxref{qXfer auxiliary vector read}).
39300 @item qXfer:btrace:read
39301 The remote stub understands the @samp{qXfer:btrace:read}
39302 packet (@pxref{qXfer btrace read}).
39304 @item qXfer:btrace-conf:read
39305 The remote stub understands the @samp{qXfer:btrace-conf:read}
39306 packet (@pxref{qXfer btrace-conf read}).
39308 @item qXfer:exec-file:read
39309 The remote stub understands the @samp{qXfer:exec-file:read} packet
39310 (@pxref{qXfer executable filename read}).
39312 @item qXfer:features:read
39313 The remote stub understands the @samp{qXfer:features:read} packet
39314 (@pxref{qXfer target description read}).
39316 @item qXfer:libraries:read
39317 The remote stub understands the @samp{qXfer:libraries:read} packet
39318 (@pxref{qXfer library list read}).
39320 @item qXfer:libraries-svr4:read
39321 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39322 (@pxref{qXfer svr4 library list read}).
39324 @item augmented-libraries-svr4-read
39325 The remote stub understands the augmented form of the
39326 @samp{qXfer:libraries-svr4:read} packet
39327 (@pxref{qXfer svr4 library list read}).
39329 @item qXfer:memory-map:read
39330 The remote stub understands the @samp{qXfer:memory-map:read} packet
39331 (@pxref{qXfer memory map read}).
39333 @item qXfer:sdata:read
39334 The remote stub understands the @samp{qXfer:sdata:read} packet
39335 (@pxref{qXfer sdata read}).
39337 @item qXfer:spu:read
39338 The remote stub understands the @samp{qXfer:spu:read} packet
39339 (@pxref{qXfer spu read}).
39341 @item qXfer:spu:write
39342 The remote stub understands the @samp{qXfer:spu:write} packet
39343 (@pxref{qXfer spu write}).
39345 @item qXfer:siginfo:read
39346 The remote stub understands the @samp{qXfer:siginfo:read} packet
39347 (@pxref{qXfer siginfo read}).
39349 @item qXfer:siginfo:write
39350 The remote stub understands the @samp{qXfer:siginfo:write} packet
39351 (@pxref{qXfer siginfo write}).
39353 @item qXfer:threads:read
39354 The remote stub understands the @samp{qXfer:threads:read} packet
39355 (@pxref{qXfer threads read}).
39357 @item qXfer:traceframe-info:read
39358 The remote stub understands the @samp{qXfer:traceframe-info:read}
39359 packet (@pxref{qXfer traceframe info read}).
39361 @item qXfer:uib:read
39362 The remote stub understands the @samp{qXfer:uib:read}
39363 packet (@pxref{qXfer unwind info block}).
39365 @item qXfer:fdpic:read
39366 The remote stub understands the @samp{qXfer:fdpic:read}
39367 packet (@pxref{qXfer fdpic loadmap read}).
39370 The remote stub understands the @samp{QNonStop} packet
39371 (@pxref{QNonStop}).
39373 @item QCatchSyscalls
39374 The remote stub understands the @samp{QCatchSyscalls} packet
39375 (@pxref{QCatchSyscalls}).
39378 The remote stub understands the @samp{QPassSignals} packet
39379 (@pxref{QPassSignals}).
39381 @item QStartNoAckMode
39382 The remote stub understands the @samp{QStartNoAckMode} packet and
39383 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39386 @anchor{multiprocess extensions}
39387 @cindex multiprocess extensions, in remote protocol
39388 The remote stub understands the multiprocess extensions to the remote
39389 protocol syntax. The multiprocess extensions affect the syntax of
39390 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39391 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39392 replies. Note that reporting this feature indicates support for the
39393 syntactic extensions only, not that the stub necessarily supports
39394 debugging of more than one process at a time. The stub must not use
39395 multiprocess extensions in packet replies unless @value{GDBN} has also
39396 indicated it supports them in its @samp{qSupported} request.
39398 @item qXfer:osdata:read
39399 The remote stub understands the @samp{qXfer:osdata:read} packet
39400 ((@pxref{qXfer osdata read}).
39402 @item ConditionalBreakpoints
39403 The target accepts and implements evaluation of conditional expressions
39404 defined for breakpoints. The target will only report breakpoint triggers
39405 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39407 @item ConditionalTracepoints
39408 The remote stub accepts and implements conditional expressions defined
39409 for tracepoints (@pxref{Tracepoint Conditions}).
39411 @item ReverseContinue
39412 The remote stub accepts and implements the reverse continue packet
39416 The remote stub accepts and implements the reverse step packet
39419 @item TracepointSource
39420 The remote stub understands the @samp{QTDPsrc} packet that supplies
39421 the source form of tracepoint definitions.
39424 The remote stub understands the @samp{QAgent} packet.
39427 The remote stub understands the @samp{QAllow} packet.
39429 @item QDisableRandomization
39430 The remote stub understands the @samp{QDisableRandomization} packet.
39432 @item StaticTracepoint
39433 @cindex static tracepoints, in remote protocol
39434 The remote stub supports static tracepoints.
39436 @item InstallInTrace
39437 @anchor{install tracepoint in tracing}
39438 The remote stub supports installing tracepoint in tracing.
39440 @item EnableDisableTracepoints
39441 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39442 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39443 to be enabled and disabled while a trace experiment is running.
39445 @item QTBuffer:size
39446 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39447 packet that allows to change the size of the trace buffer.
39450 @cindex string tracing, in remote protocol
39451 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39452 See @ref{Bytecode Descriptions} for details about the bytecode.
39454 @item BreakpointCommands
39455 @cindex breakpoint commands, in remote protocol
39456 The remote stub supports running a breakpoint's command list itself,
39457 rather than reporting the hit to @value{GDBN}.
39460 The remote stub understands the @samp{Qbtrace:off} packet.
39463 The remote stub understands the @samp{Qbtrace:bts} packet.
39466 The remote stub understands the @samp{Qbtrace:pt} packet.
39468 @item Qbtrace-conf:bts:size
39469 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
39471 @item Qbtrace-conf:pt:size
39472 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
39475 The remote stub reports the @samp{swbreak} stop reason for memory
39479 The remote stub reports the @samp{hwbreak} stop reason for hardware
39483 The remote stub reports the @samp{fork} stop reason for fork events.
39486 The remote stub reports the @samp{vfork} stop reason for vfork events
39487 and vforkdone events.
39490 The remote stub reports the @samp{exec} stop reason for exec events.
39492 @item vContSupported
39493 The remote stub reports the supported actions in the reply to
39494 @samp{vCont?} packet.
39496 @item QThreadEvents
39497 The remote stub understands the @samp{QThreadEvents} packet.
39500 The remote stub reports the @samp{N} stop reply.
39505 @cindex symbol lookup, remote request
39506 @cindex @samp{qSymbol} packet
39507 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39508 requests. Accept requests from the target for the values of symbols.
39513 The target does not need to look up any (more) symbols.
39514 @item qSymbol:@var{sym_name}
39515 The target requests the value of symbol @var{sym_name} (hex encoded).
39516 @value{GDBN} may provide the value by using the
39517 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39521 @item qSymbol:@var{sym_value}:@var{sym_name}
39522 Set the value of @var{sym_name} to @var{sym_value}.
39524 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39525 target has previously requested.
39527 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39528 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39534 The target does not need to look up any (more) symbols.
39535 @item qSymbol:@var{sym_name}
39536 The target requests the value of a new symbol @var{sym_name} (hex
39537 encoded). @value{GDBN} will continue to supply the values of symbols
39538 (if available), until the target ceases to request them.
39543 @itemx QTDisconnected
39550 @itemx qTMinFTPILen
39552 @xref{Tracepoint Packets}.
39554 @item qThreadExtraInfo,@var{thread-id}
39555 @cindex thread attributes info, remote request
39556 @cindex @samp{qThreadExtraInfo} packet
39557 Obtain from the target OS a printable string description of thread
39558 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
39559 for the forms of @var{thread-id}. This
39560 string may contain anything that the target OS thinks is interesting
39561 for @value{GDBN} to tell the user about the thread. The string is
39562 displayed in @value{GDBN}'s @code{info threads} display. Some
39563 examples of possible thread extra info strings are @samp{Runnable}, or
39564 @samp{Blocked on Mutex}.
39568 @item @var{XX}@dots{}
39569 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39570 comprising the printable string containing the extra information about
39571 the thread's attributes.
39574 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39575 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39576 conventions above. Please don't use this packet as a model for new
39595 @xref{Tracepoint Packets}.
39597 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39598 @cindex read special object, remote request
39599 @cindex @samp{qXfer} packet
39600 @anchor{qXfer read}
39601 Read uninterpreted bytes from the target's special data area
39602 identified by the keyword @var{object}. Request @var{length} bytes
39603 starting at @var{offset} bytes into the data. The content and
39604 encoding of @var{annex} is specific to @var{object}; it can supply
39605 additional details about what data to access.
39610 Data @var{data} (@pxref{Binary Data}) has been read from the
39611 target. There may be more data at a higher address (although
39612 it is permitted to return @samp{m} even for the last valid
39613 block of data, as long as at least one byte of data was read).
39614 It is possible for @var{data} to have fewer bytes than the @var{length} in the
39618 Data @var{data} (@pxref{Binary Data}) has been read from the target.
39619 There is no more data to be read. It is possible for @var{data} to
39620 have fewer bytes than the @var{length} in the request.
39623 The @var{offset} in the request is at the end of the data.
39624 There is no more data to be read.
39627 The request was malformed, or @var{annex} was invalid.
39630 The offset was invalid, or there was an error encountered reading the data.
39631 The @var{nn} part is a hex-encoded @code{errno} value.
39634 An empty reply indicates the @var{object} string was not recognized by
39635 the stub, or that the object does not support reading.
39638 Here are the specific requests of this form defined so far. All the
39639 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39640 formats, listed above.
39643 @item qXfer:auxv:read::@var{offset},@var{length}
39644 @anchor{qXfer auxiliary vector read}
39645 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39646 auxiliary vector}. Note @var{annex} must be empty.
39648 This packet is not probed by default; the remote stub must request it,
39649 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39651 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39652 @anchor{qXfer btrace read}
39654 Return a description of the current branch trace.
39655 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39656 packet may have one of the following values:
39660 Returns all available branch trace.
39663 Returns all available branch trace if the branch trace changed since
39664 the last read request.
39667 Returns the new branch trace since the last read request. Adds a new
39668 block to the end of the trace that begins at zero and ends at the source
39669 location of the first branch in the trace buffer. This extra block is
39670 used to stitch traces together.
39672 If the trace buffer overflowed, returns an error indicating the overflow.
39675 This packet is not probed by default; the remote stub must request it
39676 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39678 @item qXfer:btrace-conf:read::@var{offset},@var{length}
39679 @anchor{qXfer btrace-conf read}
39681 Return a description of the current branch trace configuration.
39682 @xref{Branch Trace Configuration Format}.
39684 This packet is not probed by default; the remote stub must request it
39685 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39687 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
39688 @anchor{qXfer executable filename read}
39689 Return the full absolute name of the file that was executed to create
39690 a process running on the remote system. The annex specifies the
39691 numeric process ID of the process to query, encoded as a hexadecimal
39692 number. If the annex part is empty the remote stub should return the
39693 filename corresponding to the currently executing process.
39695 This packet is not probed by default; the remote stub must request it,
39696 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39698 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39699 @anchor{qXfer target description read}
39700 Access the @dfn{target description}. @xref{Target Descriptions}. The
39701 annex specifies which XML document to access. The main description is
39702 always loaded from the @samp{target.xml} annex.
39704 This packet is not probed by default; the remote stub must request it,
39705 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39707 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39708 @anchor{qXfer library list read}
39709 Access the target's list of loaded libraries. @xref{Library List Format}.
39710 The annex part of the generic @samp{qXfer} packet must be empty
39711 (@pxref{qXfer read}).
39713 Targets which maintain a list of libraries in the program's memory do
39714 not need to implement this packet; it is designed for platforms where
39715 the operating system manages the list of loaded libraries.
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:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39721 @anchor{qXfer svr4 library list read}
39722 Access the target's list of loaded libraries when the target is an SVR4
39723 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39724 of the generic @samp{qXfer} packet must be empty unless the remote
39725 stub indicated it supports the augmented form of this packet
39726 by supplying an appropriate @samp{qSupported} response
39727 (@pxref{qXfer read}, @ref{qSupported}).
39729 This packet is optional for better performance on SVR4 targets.
39730 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39732 This packet is not probed by default; the remote stub must request it,
39733 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39735 If the remote stub indicates it supports the augmented form of this
39736 packet then the annex part of the generic @samp{qXfer} packet may
39737 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39738 arguments. The currently supported arguments are:
39741 @item start=@var{address}
39742 A hexadecimal number specifying the address of the @samp{struct
39743 link_map} to start reading the library list from. If unset or zero
39744 then the first @samp{struct link_map} in the library list will be
39745 chosen as the starting point.
39747 @item prev=@var{address}
39748 A hexadecimal number specifying the address of the @samp{struct
39749 link_map} immediately preceding the @samp{struct link_map}
39750 specified by the @samp{start} argument. If unset or zero then
39751 the remote stub will expect that no @samp{struct link_map}
39752 exists prior to the starting point.
39756 Arguments that are not understood by the remote stub will be silently
39759 @item qXfer:memory-map:read::@var{offset},@var{length}
39760 @anchor{qXfer memory map read}
39761 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39762 annex part of the generic @samp{qXfer} packet must be empty
39763 (@pxref{qXfer read}).
39765 This packet is not probed by default; the remote stub must request it,
39766 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39768 @item qXfer:sdata:read::@var{offset},@var{length}
39769 @anchor{qXfer sdata read}
39771 Read contents of the extra collected static tracepoint marker
39772 information. The annex part of the generic @samp{qXfer} packet must
39773 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39776 This packet is not probed by default; the remote stub must request it,
39777 by supplying an appropriate @samp{qSupported} response
39778 (@pxref{qSupported}).
39780 @item qXfer:siginfo:read::@var{offset},@var{length}
39781 @anchor{qXfer siginfo read}
39782 Read contents of the extra signal information on the target
39783 system. The annex part of the generic @samp{qXfer} packet must be
39784 empty (@pxref{qXfer read}).
39786 This packet is not probed by default; the remote stub must request it,
39787 by supplying an appropriate @samp{qSupported} response
39788 (@pxref{qSupported}).
39790 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39791 @anchor{qXfer spu read}
39792 Read contents of an @code{spufs} file on the target system. The
39793 annex specifies which file to read; it must be of the form
39794 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39795 in the target process, and @var{name} identifes the @code{spufs} file
39796 in that context to be accessed.
39798 This packet is not probed by default; the remote stub must request it,
39799 by supplying an appropriate @samp{qSupported} response
39800 (@pxref{qSupported}).
39802 @item qXfer:threads:read::@var{offset},@var{length}
39803 @anchor{qXfer threads read}
39804 Access the list of threads on target. @xref{Thread List Format}. The
39805 annex part of the generic @samp{qXfer} packet must be empty
39806 (@pxref{qXfer read}).
39808 This packet is not probed by default; the remote stub must request it,
39809 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39811 @item qXfer:traceframe-info:read::@var{offset},@var{length}
39812 @anchor{qXfer traceframe info read}
39814 Return a description of the current traceframe's contents.
39815 @xref{Traceframe Info Format}. The annex part of the generic
39816 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
39818 This packet is not probed by default; the remote stub must request it,
39819 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39821 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
39822 @anchor{qXfer unwind info block}
39824 Return the unwind information block for @var{pc}. This packet is used
39825 on OpenVMS/ia64 to ask the kernel unwind information.
39827 This packet is not probed by default.
39829 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
39830 @anchor{qXfer fdpic loadmap read}
39831 Read contents of @code{loadmap}s on the target system. The
39832 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
39833 executable @code{loadmap} or interpreter @code{loadmap} to read.
39835 This packet is not probed by default; the remote stub must request it,
39836 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39838 @item qXfer:osdata:read::@var{offset},@var{length}
39839 @anchor{qXfer osdata read}
39840 Access the target's @dfn{operating system information}.
39841 @xref{Operating System Information}.
39845 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
39846 @cindex write data into object, remote request
39847 @anchor{qXfer write}
39848 Write uninterpreted bytes into the target's special data area
39849 identified by the keyword @var{object}, starting at @var{offset} bytes
39850 into the data. The binary-encoded data (@pxref{Binary Data}) to be
39851 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
39852 is specific to @var{object}; it can supply additional details about what data
39858 @var{nn} (hex encoded) is the number of bytes written.
39859 This may be fewer bytes than supplied in the request.
39862 The request was malformed, or @var{annex} was invalid.
39865 The offset was invalid, or there was an error encountered writing the data.
39866 The @var{nn} part is a hex-encoded @code{errno} value.
39869 An empty reply indicates the @var{object} string was not
39870 recognized by the stub, or that the object does not support writing.
39873 Here are the specific requests of this form defined so far. All the
39874 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
39875 formats, listed above.
39878 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
39879 @anchor{qXfer siginfo write}
39880 Write @var{data} to the extra signal information on the target system.
39881 The annex part of the generic @samp{qXfer} packet must be
39882 empty (@pxref{qXfer write}).
39884 This packet is not probed by default; the remote stub must request it,
39885 by supplying an appropriate @samp{qSupported} response
39886 (@pxref{qSupported}).
39888 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
39889 @anchor{qXfer spu write}
39890 Write @var{data} to an @code{spufs} file on the target system. The
39891 annex specifies which file to write; it must be of the form
39892 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39893 in the target process, and @var{name} identifes the @code{spufs} file
39894 in that context to be accessed.
39896 This packet is not probed by default; the remote stub must request it,
39897 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39900 @item qXfer:@var{object}:@var{operation}:@dots{}
39901 Requests of this form may be added in the future. When a stub does
39902 not recognize the @var{object} keyword, or its support for
39903 @var{object} does not recognize the @var{operation} keyword, the stub
39904 must respond with an empty packet.
39906 @item qAttached:@var{pid}
39907 @cindex query attached, remote request
39908 @cindex @samp{qAttached} packet
39909 Return an indication of whether the remote server attached to an
39910 existing process or created a new process. When the multiprocess
39911 protocol extensions are supported (@pxref{multiprocess extensions}),
39912 @var{pid} is an integer in hexadecimal format identifying the target
39913 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
39914 the query packet will be simplified as @samp{qAttached}.
39916 This query is used, for example, to know whether the remote process
39917 should be detached or killed when a @value{GDBN} session is ended with
39918 the @code{quit} command.
39923 The remote server attached to an existing process.
39925 The remote server created a new process.
39927 A badly formed request or an error was encountered.
39931 Enable branch tracing for the current thread using Branch Trace Store.
39936 Branch tracing has been enabled.
39938 A badly formed request or an error was encountered.
39942 Enable branch tracing for the current thread using Intel Processor Trace.
39947 Branch tracing has been enabled.
39949 A badly formed request or an error was encountered.
39953 Disable branch tracing for the current thread.
39958 Branch tracing has been disabled.
39960 A badly formed request or an error was encountered.
39963 @item Qbtrace-conf:bts:size=@var{value}
39964 Set the requested ring buffer size for new threads that use the
39965 btrace recording method in bts format.
39970 The ring buffer size has been set.
39972 A badly formed request or an error was encountered.
39975 @item Qbtrace-conf:pt:size=@var{value}
39976 Set the requested ring buffer size for new threads that use the
39977 btrace recording method in pt format.
39982 The ring buffer size has been set.
39984 A badly formed request or an error was encountered.
39989 @node Architecture-Specific Protocol Details
39990 @section Architecture-Specific Protocol Details
39992 This section describes how the remote protocol is applied to specific
39993 target architectures. Also see @ref{Standard Target Features}, for
39994 details of XML target descriptions for each architecture.
39997 * ARM-Specific Protocol Details::
39998 * MIPS-Specific Protocol Details::
40001 @node ARM-Specific Protocol Details
40002 @subsection @acronym{ARM}-specific Protocol Details
40005 * ARM Breakpoint Kinds::
40008 @node ARM Breakpoint Kinds
40009 @subsubsection @acronym{ARM} Breakpoint Kinds
40010 @cindex breakpoint kinds, @acronym{ARM}
40012 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40017 16-bit Thumb mode breakpoint.
40020 32-bit Thumb mode (Thumb-2) breakpoint.
40023 32-bit @acronym{ARM} mode breakpoint.
40027 @node MIPS-Specific Protocol Details
40028 @subsection @acronym{MIPS}-specific Protocol Details
40031 * MIPS Register packet Format::
40032 * MIPS Breakpoint Kinds::
40035 @node MIPS Register packet Format
40036 @subsubsection @acronym{MIPS} Register Packet Format
40037 @cindex register packet format, @acronym{MIPS}
40039 The following @code{g}/@code{G} packets have previously been defined.
40040 In the below, some thirty-two bit registers are transferred as
40041 sixty-four bits. Those registers should be zero/sign extended (which?)
40042 to fill the space allocated. Register bytes are transferred in target
40043 byte order. The two nibbles within a register byte are transferred
40044 most-significant -- least-significant.
40049 All registers are transferred as thirty-two bit quantities in the order:
40050 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
40051 registers; fsr; fir; fp.
40054 All registers are transferred as sixty-four bit quantities (including
40055 thirty-two bit registers such as @code{sr}). The ordering is the same
40060 @node MIPS Breakpoint Kinds
40061 @subsubsection @acronym{MIPS} Breakpoint Kinds
40062 @cindex breakpoint kinds, @acronym{MIPS}
40064 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40069 16-bit @acronym{MIPS16} mode breakpoint.
40072 16-bit @acronym{microMIPS} mode breakpoint.
40075 32-bit standard @acronym{MIPS} mode breakpoint.
40078 32-bit @acronym{microMIPS} mode breakpoint.
40082 @node Tracepoint Packets
40083 @section Tracepoint Packets
40084 @cindex tracepoint packets
40085 @cindex packets, tracepoint
40087 Here we describe the packets @value{GDBN} uses to implement
40088 tracepoints (@pxref{Tracepoints}).
40092 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
40093 @cindex @samp{QTDP} packet
40094 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
40095 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
40096 the tracepoint is disabled. The @var{step} gives the tracepoint's step
40097 count, and @var{pass} gives its pass count. If an @samp{F} is present,
40098 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
40099 the number of bytes that the target should copy elsewhere to make room
40100 for the tracepoint. If an @samp{X} is present, it introduces a
40101 tracepoint condition, which consists of a hexadecimal length, followed
40102 by a comma and hex-encoded bytes, in a manner similar to action
40103 encodings as described below. If the trailing @samp{-} is present,
40104 further @samp{QTDP} packets will follow to specify this tracepoint's
40110 The packet was understood and carried out.
40112 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40114 The packet was not recognized.
40117 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
40118 Define actions to be taken when a tracepoint is hit. The @var{n} and
40119 @var{addr} must be the same as in the initial @samp{QTDP} packet for
40120 this tracepoint. This packet may only be sent immediately after
40121 another @samp{QTDP} packet that ended with a @samp{-}. If the
40122 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
40123 specifying more actions for this tracepoint.
40125 In the series of action packets for a given tracepoint, at most one
40126 can have an @samp{S} before its first @var{action}. If such a packet
40127 is sent, it and the following packets define ``while-stepping''
40128 actions. Any prior packets define ordinary actions --- that is, those
40129 taken when the tracepoint is first hit. If no action packet has an
40130 @samp{S}, then all the packets in the series specify ordinary
40131 tracepoint actions.
40133 The @samp{@var{action}@dots{}} portion of the packet is a series of
40134 actions, concatenated without separators. Each action has one of the
40140 Collect the registers whose bits are set in @var{mask},
40141 a hexadecimal number whose @var{i}'th bit is set if register number
40142 @var{i} should be collected. (The least significant bit is numbered
40143 zero.) Note that @var{mask} may be any number of digits long; it may
40144 not fit in a 32-bit word.
40146 @item M @var{basereg},@var{offset},@var{len}
40147 Collect @var{len} bytes of memory starting at the address in register
40148 number @var{basereg}, plus @var{offset}. If @var{basereg} is
40149 @samp{-1}, then the range has a fixed address: @var{offset} is the
40150 address of the lowest byte to collect. The @var{basereg},
40151 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
40152 values (the @samp{-1} value for @var{basereg} is a special case).
40154 @item X @var{len},@var{expr}
40155 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
40156 it directs. The agent expression @var{expr} is as described in
40157 @ref{Agent Expressions}. Each byte of the expression is encoded as a
40158 two-digit hex number in the packet; @var{len} is the number of bytes
40159 in the expression (and thus one-half the number of hex digits in the
40164 Any number of actions may be packed together in a single @samp{QTDP}
40165 packet, as long as the packet does not exceed the maximum packet
40166 length (400 bytes, for many stubs). There may be only one @samp{R}
40167 action per tracepoint, and it must precede any @samp{M} or @samp{X}
40168 actions. Any registers referred to by @samp{M} and @samp{X} actions
40169 must be collected by a preceding @samp{R} action. (The
40170 ``while-stepping'' actions are treated as if they were attached to a
40171 separate tracepoint, as far as these restrictions are concerned.)
40176 The packet was understood and carried out.
40178 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40180 The packet was not recognized.
40183 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
40184 @cindex @samp{QTDPsrc} packet
40185 Specify a source string of tracepoint @var{n} at address @var{addr}.
40186 This is useful to get accurate reproduction of the tracepoints
40187 originally downloaded at the beginning of the trace run. The @var{type}
40188 is the name of the tracepoint part, such as @samp{cond} for the
40189 tracepoint's conditional expression (see below for a list of types), while
40190 @var{bytes} is the string, encoded in hexadecimal.
40192 @var{start} is the offset of the @var{bytes} within the overall source
40193 string, while @var{slen} is the total length of the source string.
40194 This is intended for handling source strings that are longer than will
40195 fit in a single packet.
40196 @c Add detailed example when this info is moved into a dedicated
40197 @c tracepoint descriptions section.
40199 The available string types are @samp{at} for the location,
40200 @samp{cond} for the conditional, and @samp{cmd} for an action command.
40201 @value{GDBN} sends a separate packet for each command in the action
40202 list, in the same order in which the commands are stored in the list.
40204 The target does not need to do anything with source strings except
40205 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
40208 Although this packet is optional, and @value{GDBN} will only send it
40209 if the target replies with @samp{TracepointSource} @xref{General
40210 Query Packets}, it makes both disconnected tracing and trace files
40211 much easier to use. Otherwise the user must be careful that the
40212 tracepoints in effect while looking at trace frames are identical to
40213 the ones in effect during the trace run; even a small discrepancy
40214 could cause @samp{tdump} not to work, or a particular trace frame not
40217 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
40218 @cindex define trace state variable, remote request
40219 @cindex @samp{QTDV} packet
40220 Create a new trace state variable, number @var{n}, with an initial
40221 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
40222 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
40223 the option of not using this packet for initial values of zero; the
40224 target should simply create the trace state variables as they are
40225 mentioned in expressions. The value @var{builtin} should be 1 (one)
40226 if the trace state variable is builtin and 0 (zero) if it is not builtin.
40227 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
40228 @samp{qTsV} packet had it set. The contents of @var{name} is the
40229 hex-encoded name (without the leading @samp{$}) of the trace state
40232 @item QTFrame:@var{n}
40233 @cindex @samp{QTFrame} packet
40234 Select the @var{n}'th tracepoint frame from the buffer, and use the
40235 register and memory contents recorded there to answer subsequent
40236 request packets from @value{GDBN}.
40238 A successful reply from the stub indicates that the stub has found the
40239 requested frame. The response is a series of parts, concatenated
40240 without separators, describing the frame we selected. Each part has
40241 one of the following forms:
40245 The selected frame is number @var{n} in the trace frame buffer;
40246 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40247 was no frame matching the criteria in the request packet.
40250 The selected trace frame records a hit of tracepoint number @var{t};
40251 @var{t} is a hexadecimal number.
40255 @item QTFrame:pc:@var{addr}
40256 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40257 currently selected frame whose PC is @var{addr};
40258 @var{addr} is a hexadecimal number.
40260 @item QTFrame:tdp:@var{t}
40261 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40262 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40263 is a hexadecimal number.
40265 @item QTFrame:range:@var{start}:@var{end}
40266 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40267 currently selected frame whose PC is between @var{start} (inclusive)
40268 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40271 @item QTFrame:outside:@var{start}:@var{end}
40272 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40273 frame @emph{outside} the given range of addresses (exclusive).
40276 @cindex @samp{qTMinFTPILen} packet
40277 This packet requests the minimum length of instruction at which a fast
40278 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40279 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40280 it depends on the target system being able to create trampolines in
40281 the first 64K of memory, which might or might not be possible for that
40282 system. So the reply to this packet will be 4 if it is able to
40289 The minimum instruction length is currently unknown.
40291 The minimum instruction length is @var{length}, where @var{length}
40292 is a hexadecimal number greater or equal to 1. A reply
40293 of 1 means that a fast tracepoint may be placed on any instruction
40294 regardless of size.
40296 An error has occurred.
40298 An empty reply indicates that the request is not supported by the stub.
40302 @cindex @samp{QTStart} packet
40303 Begin the tracepoint experiment. Begin collecting data from
40304 tracepoint hits in the trace frame buffer. This packet supports the
40305 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40306 instruction reply packet}).
40309 @cindex @samp{QTStop} packet
40310 End the tracepoint experiment. Stop collecting trace frames.
40312 @item QTEnable:@var{n}:@var{addr}
40314 @cindex @samp{QTEnable} packet
40315 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40316 experiment. If the tracepoint was previously disabled, then collection
40317 of data from it will resume.
40319 @item QTDisable:@var{n}:@var{addr}
40321 @cindex @samp{QTDisable} packet
40322 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40323 experiment. No more data will be collected from the tracepoint unless
40324 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40327 @cindex @samp{QTinit} packet
40328 Clear the table of tracepoints, and empty the trace frame buffer.
40330 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40331 @cindex @samp{QTro} packet
40332 Establish the given ranges of memory as ``transparent''. The stub
40333 will answer requests for these ranges from memory's current contents,
40334 if they were not collected as part of the tracepoint hit.
40336 @value{GDBN} uses this to mark read-only regions of memory, like those
40337 containing program code. Since these areas never change, they should
40338 still have the same contents they did when the tracepoint was hit, so
40339 there's no reason for the stub to refuse to provide their contents.
40341 @item QTDisconnected:@var{value}
40342 @cindex @samp{QTDisconnected} packet
40343 Set the choice to what to do with the tracing run when @value{GDBN}
40344 disconnects from the target. A @var{value} of 1 directs the target to
40345 continue the tracing run, while 0 tells the target to stop tracing if
40346 @value{GDBN} is no longer in the picture.
40349 @cindex @samp{qTStatus} packet
40350 Ask the stub if there is a trace experiment running right now.
40352 The reply has the form:
40356 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40357 @var{running} is a single digit @code{1} if the trace is presently
40358 running, or @code{0} if not. It is followed by semicolon-separated
40359 optional fields that an agent may use to report additional status.
40363 If the trace is not running, the agent may report any of several
40364 explanations as one of the optional fields:
40369 No trace has been run yet.
40371 @item tstop[:@var{text}]:0
40372 The trace was stopped by a user-originated stop command. The optional
40373 @var{text} field is a user-supplied string supplied as part of the
40374 stop command (for instance, an explanation of why the trace was
40375 stopped manually). It is hex-encoded.
40378 The trace stopped because the trace buffer filled up.
40380 @item tdisconnected:0
40381 The trace stopped because @value{GDBN} disconnected from the target.
40383 @item tpasscount:@var{tpnum}
40384 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40386 @item terror:@var{text}:@var{tpnum}
40387 The trace stopped because tracepoint @var{tpnum} had an error. The
40388 string @var{text} is available to describe the nature of the error
40389 (for instance, a divide by zero in the condition expression); it
40393 The trace stopped for some other reason.
40397 Additional optional fields supply statistical and other information.
40398 Although not required, they are extremely useful for users monitoring
40399 the progress of a trace run. If a trace has stopped, and these
40400 numbers are reported, they must reflect the state of the just-stopped
40405 @item tframes:@var{n}
40406 The number of trace frames in the buffer.
40408 @item tcreated:@var{n}
40409 The total number of trace frames created during the run. This may
40410 be larger than the trace frame count, if the buffer is circular.
40412 @item tsize:@var{n}
40413 The total size of the trace buffer, in bytes.
40415 @item tfree:@var{n}
40416 The number of bytes still unused in the buffer.
40418 @item circular:@var{n}
40419 The value of the circular trace buffer flag. @code{1} means that the
40420 trace buffer is circular and old trace frames will be discarded if
40421 necessary to make room, @code{0} means that the trace buffer is linear
40424 @item disconn:@var{n}
40425 The value of the disconnected tracing flag. @code{1} means that
40426 tracing will continue after @value{GDBN} disconnects, @code{0} means
40427 that the trace run will stop.
40431 @item qTP:@var{tp}:@var{addr}
40432 @cindex tracepoint status, remote request
40433 @cindex @samp{qTP} packet
40434 Ask the stub for the current state of tracepoint number @var{tp} at
40435 address @var{addr}.
40439 @item V@var{hits}:@var{usage}
40440 The tracepoint has been hit @var{hits} times so far during the trace
40441 run, and accounts for @var{usage} in the trace buffer. Note that
40442 @code{while-stepping} steps are not counted as separate hits, but the
40443 steps' space consumption is added into the usage number.
40447 @item qTV:@var{var}
40448 @cindex trace state variable value, remote request
40449 @cindex @samp{qTV} packet
40450 Ask the stub for the value of the trace state variable number @var{var}.
40455 The value of the variable is @var{value}. This will be the current
40456 value of the variable if the user is examining a running target, or a
40457 saved value if the variable was collected in the trace frame that the
40458 user is looking at. Note that multiple requests may result in
40459 different reply values, such as when requesting values while the
40460 program is running.
40463 The value of the variable is unknown. This would occur, for example,
40464 if the user is examining a trace frame in which the requested variable
40469 @cindex @samp{qTfP} packet
40471 @cindex @samp{qTsP} packet
40472 These packets request data about tracepoints that are being used by
40473 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40474 of data, and multiple @code{qTsP} to get additional pieces. Replies
40475 to these packets generally take the form of the @code{QTDP} packets
40476 that define tracepoints. (FIXME add detailed syntax)
40479 @cindex @samp{qTfV} packet
40481 @cindex @samp{qTsV} packet
40482 These packets request data about trace state variables that are on the
40483 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40484 and multiple @code{qTsV} to get additional variables. Replies to
40485 these packets follow the syntax of the @code{QTDV} packets that define
40486 trace state variables.
40492 @cindex @samp{qTfSTM} packet
40493 @cindex @samp{qTsSTM} packet
40494 These packets request data about static tracepoint markers that exist
40495 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40496 first piece of data, and multiple @code{qTsSTM} to get additional
40497 pieces. Replies to these packets take the following form:
40501 @item m @var{address}:@var{id}:@var{extra}
40503 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40504 a comma-separated list of markers
40506 (lower case letter @samp{L}) denotes end of list.
40508 An error occurred. The error number @var{nn} is given as hex digits.
40510 An empty reply indicates that the request is not supported by the
40514 The @var{address} is encoded in hex;
40515 @var{id} and @var{extra} are strings encoded in hex.
40517 In response to each query, the target will reply with a list of one or
40518 more markers, separated by commas. @value{GDBN} will respond to each
40519 reply with a request for more markers (using the @samp{qs} form of the
40520 query), until the target responds with @samp{l} (lower-case ell, for
40523 @item qTSTMat:@var{address}
40525 @cindex @samp{qTSTMat} packet
40526 This packets requests data about static tracepoint markers in the
40527 target program at @var{address}. Replies to this packet follow the
40528 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40529 tracepoint markers.
40531 @item QTSave:@var{filename}
40532 @cindex @samp{QTSave} packet
40533 This packet directs the target to save trace data to the file name
40534 @var{filename} in the target's filesystem. The @var{filename} is encoded
40535 as a hex string; the interpretation of the file name (relative vs
40536 absolute, wild cards, etc) is up to the target.
40538 @item qTBuffer:@var{offset},@var{len}
40539 @cindex @samp{qTBuffer} packet
40540 Return up to @var{len} bytes of the current contents of trace buffer,
40541 starting at @var{offset}. The trace buffer is treated as if it were
40542 a contiguous collection of traceframes, as per the trace file format.
40543 The reply consists as many hex-encoded bytes as the target can deliver
40544 in a packet; it is not an error to return fewer than were asked for.
40545 A reply consisting of just @code{l} indicates that no bytes are
40548 @item QTBuffer:circular:@var{value}
40549 This packet directs the target to use a circular trace buffer if
40550 @var{value} is 1, or a linear buffer if the value is 0.
40552 @item QTBuffer:size:@var{size}
40553 @anchor{QTBuffer-size}
40554 @cindex @samp{QTBuffer size} packet
40555 This packet directs the target to make the trace buffer be of size
40556 @var{size} if possible. A value of @code{-1} tells the target to
40557 use whatever size it prefers.
40559 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40560 @cindex @samp{QTNotes} packet
40561 This packet adds optional textual notes to the trace run. Allowable
40562 types include @code{user}, @code{notes}, and @code{tstop}, the
40563 @var{text} fields are arbitrary strings, hex-encoded.
40567 @subsection Relocate instruction reply packet
40568 When installing fast tracepoints in memory, the target may need to
40569 relocate the instruction currently at the tracepoint address to a
40570 different address in memory. For most instructions, a simple copy is
40571 enough, but, for example, call instructions that implicitly push the
40572 return address on the stack, and relative branches or other
40573 PC-relative instructions require offset adjustment, so that the effect
40574 of executing the instruction at a different address is the same as if
40575 it had executed in the original location.
40577 In response to several of the tracepoint packets, the target may also
40578 respond with a number of intermediate @samp{qRelocInsn} request
40579 packets before the final result packet, to have @value{GDBN} handle
40580 this relocation operation. If a packet supports this mechanism, its
40581 documentation will explicitly say so. See for example the above
40582 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40583 format of the request is:
40586 @item qRelocInsn:@var{from};@var{to}
40588 This requests @value{GDBN} to copy instruction at address @var{from}
40589 to address @var{to}, possibly adjusted so that executing the
40590 instruction at @var{to} has the same effect as executing it at
40591 @var{from}. @value{GDBN} writes the adjusted instruction to target
40592 memory starting at @var{to}.
40597 @item qRelocInsn:@var{adjusted_size}
40598 Informs the stub the relocation is complete. The @var{adjusted_size} is
40599 the length in bytes of resulting relocated instruction sequence.
40601 A badly formed request was detected, or an error was encountered while
40602 relocating the instruction.
40605 @node Host I/O Packets
40606 @section Host I/O Packets
40607 @cindex Host I/O, remote protocol
40608 @cindex file transfer, remote protocol
40610 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40611 operations on the far side of a remote link. For example, Host I/O is
40612 used to upload and download files to a remote target with its own
40613 filesystem. Host I/O uses the same constant values and data structure
40614 layout as the target-initiated File-I/O protocol. However, the
40615 Host I/O packets are structured differently. The target-initiated
40616 protocol relies on target memory to store parameters and buffers.
40617 Host I/O requests are initiated by @value{GDBN}, and the
40618 target's memory is not involved. @xref{File-I/O Remote Protocol
40619 Extension}, for more details on the target-initiated protocol.
40621 The Host I/O request packets all encode a single operation along with
40622 its arguments. They have this format:
40626 @item vFile:@var{operation}: @var{parameter}@dots{}
40627 @var{operation} is the name of the particular request; the target
40628 should compare the entire packet name up to the second colon when checking
40629 for a supported operation. The format of @var{parameter} depends on
40630 the operation. Numbers are always passed in hexadecimal. Negative
40631 numbers have an explicit minus sign (i.e.@: two's complement is not
40632 used). Strings (e.g.@: filenames) are encoded as a series of
40633 hexadecimal bytes. The last argument to a system call may be a
40634 buffer of escaped binary data (@pxref{Binary Data}).
40638 The valid responses to Host I/O packets are:
40642 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40643 @var{result} is the integer value returned by this operation, usually
40644 non-negative for success and -1 for errors. If an error has occured,
40645 @var{errno} will be included in the result specifying a
40646 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40647 operations which return data, @var{attachment} supplies the data as a
40648 binary buffer. Binary buffers in response packets are escaped in the
40649 normal way (@pxref{Binary Data}). See the individual packet
40650 documentation for the interpretation of @var{result} and
40654 An empty response indicates that this operation is not recognized.
40658 These are the supported Host I/O operations:
40661 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
40662 Open a file at @var{filename} and return a file descriptor for it, or
40663 return -1 if an error occurs. The @var{filename} is a string,
40664 @var{flags} is an integer indicating a mask of open flags
40665 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40666 of mode bits to use if the file is created (@pxref{mode_t Values}).
40667 @xref{open}, for details of the open flags and mode values.
40669 @item vFile:close: @var{fd}
40670 Close the open file corresponding to @var{fd} and return 0, or
40671 -1 if an error occurs.
40673 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40674 Read data from the open file corresponding to @var{fd}. Up to
40675 @var{count} bytes will be read from the file, starting at @var{offset}
40676 relative to the start of the file. The target may read fewer bytes;
40677 common reasons include packet size limits and an end-of-file
40678 condition. The number of bytes read is returned. Zero should only be
40679 returned for a successful read at the end of the file, or if
40680 @var{count} was zero.
40682 The data read should be returned as a binary attachment on success.
40683 If zero bytes were read, the response should include an empty binary
40684 attachment (i.e.@: a trailing semicolon). The return value is the
40685 number of target bytes read; the binary attachment may be longer if
40686 some characters were escaped.
40688 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40689 Write @var{data} (a binary buffer) to the open file corresponding
40690 to @var{fd}. Start the write at @var{offset} from the start of the
40691 file. Unlike many @code{write} system calls, there is no
40692 separate @var{count} argument; the length of @var{data} in the
40693 packet is used. @samp{vFile:write} returns the number of bytes written,
40694 which may be shorter than the length of @var{data}, or -1 if an
40697 @item vFile:fstat: @var{fd}
40698 Get information about the open file corresponding to @var{fd}.
40699 On success the information is returned as a binary attachment
40700 and the return value is the size of this attachment in bytes.
40701 If an error occurs the return value is -1. The format of the
40702 returned binary attachment is as described in @ref{struct stat}.
40704 @item vFile:unlink: @var{filename}
40705 Delete the file at @var{filename} on the target. Return 0,
40706 or -1 if an error occurs. The @var{filename} is a string.
40708 @item vFile:readlink: @var{filename}
40709 Read value of symbolic link @var{filename} on the target. Return
40710 the number of bytes read, or -1 if an error occurs.
40712 The data read should be returned as a binary attachment on success.
40713 If zero bytes were read, the response should include an empty binary
40714 attachment (i.e.@: a trailing semicolon). The return value is the
40715 number of target bytes read; the binary attachment may be longer if
40716 some characters were escaped.
40718 @item vFile:setfs: @var{pid}
40719 Select the filesystem on which @code{vFile} operations with
40720 @var{filename} arguments will operate. This is required for
40721 @value{GDBN} to be able to access files on remote targets where
40722 the remote stub does not share a common filesystem with the
40725 If @var{pid} is nonzero, select the filesystem as seen by process
40726 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
40727 the remote stub. Return 0 on success, or -1 if an error occurs.
40728 If @code{vFile:setfs:} indicates success, the selected filesystem
40729 remains selected until the next successful @code{vFile:setfs:}
40735 @section Interrupts
40736 @cindex interrupts (remote protocol)
40737 @anchor{interrupting remote targets}
40739 In all-stop mode, when a program on the remote target is running,
40740 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
40741 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
40742 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40744 The precise meaning of @code{BREAK} is defined by the transport
40745 mechanism and may, in fact, be undefined. @value{GDBN} does not
40746 currently define a @code{BREAK} mechanism for any of the network
40747 interfaces except for TCP, in which case @value{GDBN} sends the
40748 @code{telnet} BREAK sequence.
40750 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40751 transport mechanisms. It is represented by sending the single byte
40752 @code{0x03} without any of the usual packet overhead described in
40753 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40754 transmitted as part of a packet, it is considered to be packet data
40755 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40756 (@pxref{X packet}), used for binary downloads, may include an unescaped
40757 @code{0x03} as part of its packet.
40759 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40760 When Linux kernel receives this sequence from serial port,
40761 it stops execution and connects to gdb.
40763 In non-stop mode, because packet resumptions are asynchronous
40764 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
40765 command to the remote stub, even when the target is running. For that
40766 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
40767 packet}) with the usual packet framing instead of the single byte
40770 Stubs are not required to recognize these interrupt mechanisms and the
40771 precise meaning associated with receipt of the interrupt is
40772 implementation defined. If the target supports debugging of multiple
40773 threads and/or processes, it should attempt to interrupt all
40774 currently-executing threads and processes.
40775 If the stub is successful at interrupting the
40776 running program, it should send one of the stop
40777 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40778 of successfully stopping the program in all-stop mode, and a stop reply
40779 for each stopped thread in non-stop mode.
40780 Interrupts received while the
40781 program is stopped are queued and the program will be interrupted when
40782 it is resumed next time.
40784 @node Notification Packets
40785 @section Notification Packets
40786 @cindex notification packets
40787 @cindex packets, notification
40789 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40790 packets that require no acknowledgment. Both the GDB and the stub
40791 may send notifications (although the only notifications defined at
40792 present are sent by the stub). Notifications carry information
40793 without incurring the round-trip latency of an acknowledgment, and so
40794 are useful for low-impact communications where occasional packet loss
40797 A notification packet has the form @samp{% @var{data} #
40798 @var{checksum}}, where @var{data} is the content of the notification,
40799 and @var{checksum} is a checksum of @var{data}, computed and formatted
40800 as for ordinary @value{GDBN} packets. A notification's @var{data}
40801 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40802 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40803 to acknowledge the notification's receipt or to report its corruption.
40805 Every notification's @var{data} begins with a name, which contains no
40806 colon characters, followed by a colon character.
40808 Recipients should silently ignore corrupted notifications and
40809 notifications they do not understand. Recipients should restart
40810 timeout periods on receipt of a well-formed notification, whether or
40811 not they understand it.
40813 Senders should only send the notifications described here when this
40814 protocol description specifies that they are permitted. In the
40815 future, we may extend the protocol to permit existing notifications in
40816 new contexts; this rule helps older senders avoid confusing newer
40819 (Older versions of @value{GDBN} ignore bytes received until they see
40820 the @samp{$} byte that begins an ordinary packet, so new stubs may
40821 transmit notifications without fear of confusing older clients. There
40822 are no notifications defined for @value{GDBN} to send at the moment, but we
40823 assume that most older stubs would ignore them, as well.)
40825 Each notification is comprised of three parts:
40827 @item @var{name}:@var{event}
40828 The notification packet is sent by the side that initiates the
40829 exchange (currently, only the stub does that), with @var{event}
40830 carrying the specific information about the notification, and
40831 @var{name} specifying the name of the notification.
40833 The acknowledge sent by the other side, usually @value{GDBN}, to
40834 acknowledge the exchange and request the event.
40837 The purpose of an asynchronous notification mechanism is to report to
40838 @value{GDBN} that something interesting happened in the remote stub.
40840 The remote stub may send notification @var{name}:@var{event}
40841 at any time, but @value{GDBN} acknowledges the notification when
40842 appropriate. The notification event is pending before @value{GDBN}
40843 acknowledges. Only one notification at a time may be pending; if
40844 additional events occur before @value{GDBN} has acknowledged the
40845 previous notification, they must be queued by the stub for later
40846 synchronous transmission in response to @var{ack} packets from
40847 @value{GDBN}. Because the notification mechanism is unreliable,
40848 the stub is permitted to resend a notification if it believes
40849 @value{GDBN} may not have received it.
40851 Specifically, notifications may appear when @value{GDBN} is not
40852 otherwise reading input from the stub, or when @value{GDBN} is
40853 expecting to read a normal synchronous response or a
40854 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
40855 Notification packets are distinct from any other communication from
40856 the stub so there is no ambiguity.
40858 After receiving a notification, @value{GDBN} shall acknowledge it by
40859 sending a @var{ack} packet as a regular, synchronous request to the
40860 stub. Such acknowledgment is not required to happen immediately, as
40861 @value{GDBN} is permitted to send other, unrelated packets to the
40862 stub first, which the stub should process normally.
40864 Upon receiving a @var{ack} packet, if the stub has other queued
40865 events to report to @value{GDBN}, it shall respond by sending a
40866 normal @var{event}. @value{GDBN} shall then send another @var{ack}
40867 packet to solicit further responses; again, it is permitted to send
40868 other, unrelated packets as well which the stub should process
40871 If the stub receives a @var{ack} packet and there are no additional
40872 @var{event} to report, the stub shall return an @samp{OK} response.
40873 At this point, @value{GDBN} has finished processing a notification
40874 and the stub has completed sending any queued events. @value{GDBN}
40875 won't accept any new notifications until the final @samp{OK} is
40876 received . If further notification events occur, the stub shall send
40877 a new notification, @value{GDBN} shall accept the notification, and
40878 the process shall be repeated.
40880 The process of asynchronous notification can be illustrated by the
40883 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
40886 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
40888 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
40893 The following notifications are defined:
40894 @multitable @columnfractions 0.12 0.12 0.38 0.38
40903 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
40904 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
40905 for information on how these notifications are acknowledged by
40907 @tab Report an asynchronous stop event in non-stop mode.
40911 @node Remote Non-Stop
40912 @section Remote Protocol Support for Non-Stop Mode
40914 @value{GDBN}'s remote protocol supports non-stop debugging of
40915 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
40916 supports non-stop mode, it should report that to @value{GDBN} by including
40917 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
40919 @value{GDBN} typically sends a @samp{QNonStop} packet only when
40920 establishing a new connection with the stub. Entering non-stop mode
40921 does not alter the state of any currently-running threads, but targets
40922 must stop all threads in any already-attached processes when entering
40923 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
40924 probe the target state after a mode change.
40926 In non-stop mode, when an attached process encounters an event that
40927 would otherwise be reported with a stop reply, it uses the
40928 asynchronous notification mechanism (@pxref{Notification Packets}) to
40929 inform @value{GDBN}. In contrast to all-stop mode, where all threads
40930 in all processes are stopped when a stop reply is sent, in non-stop
40931 mode only the thread reporting the stop event is stopped. That is,
40932 when reporting a @samp{S} or @samp{T} response to indicate completion
40933 of a step operation, hitting a breakpoint, or a fault, only the
40934 affected thread is stopped; any other still-running threads continue
40935 to run. When reporting a @samp{W} or @samp{X} response, all running
40936 threads belonging to other attached processes continue to run.
40938 In non-stop mode, the target shall respond to the @samp{?} packet as
40939 follows. First, any incomplete stop reply notification/@samp{vStopped}
40940 sequence in progress is abandoned. The target must begin a new
40941 sequence reporting stop events for all stopped threads, whether or not
40942 it has previously reported those events to @value{GDBN}. The first
40943 stop reply is sent as a synchronous reply to the @samp{?} packet, and
40944 subsequent stop replies are sent as responses to @samp{vStopped} packets
40945 using the mechanism described above. The target must not send
40946 asynchronous stop reply notifications until the sequence is complete.
40947 If all threads are running when the target receives the @samp{?} packet,
40948 or if the target is not attached to any process, it shall respond
40951 If the stub supports non-stop mode, it should also support the
40952 @samp{swbreak} stop reason if software breakpoints are supported, and
40953 the @samp{hwbreak} stop reason if hardware breakpoints are supported
40954 (@pxref{swbreak stop reason}). This is because given the asynchronous
40955 nature of non-stop mode, between the time a thread hits a breakpoint
40956 and the time the event is finally processed by @value{GDBN}, the
40957 breakpoint may have already been removed from the target. Due to
40958 this, @value{GDBN} needs to be able to tell whether a trap stop was
40959 caused by a delayed breakpoint event, which should be ignored, as
40960 opposed to a random trap signal, which should be reported to the user.
40961 Note the @samp{swbreak} feature implies that the target is responsible
40962 for adjusting the PC when a software breakpoint triggers, if
40963 necessary, such as on the x86 architecture.
40965 @node Packet Acknowledgment
40966 @section Packet Acknowledgment
40968 @cindex acknowledgment, for @value{GDBN} remote
40969 @cindex packet acknowledgment, for @value{GDBN} remote
40970 By default, when either the host or the target machine receives a packet,
40971 the first response expected is an acknowledgment: either @samp{+} (to indicate
40972 the package was received correctly) or @samp{-} (to request retransmission).
40973 This mechanism allows the @value{GDBN} remote protocol to operate over
40974 unreliable transport mechanisms, such as a serial line.
40976 In cases where the transport mechanism is itself reliable (such as a pipe or
40977 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
40978 It may be desirable to disable them in that case to reduce communication
40979 overhead, or for other reasons. This can be accomplished by means of the
40980 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
40982 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
40983 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
40984 and response format still includes the normal checksum, as described in
40985 @ref{Overview}, but the checksum may be ignored by the receiver.
40987 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
40988 no-acknowledgment mode, it should report that to @value{GDBN}
40989 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
40990 @pxref{qSupported}.
40991 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
40992 disabled via the @code{set remote noack-packet off} command
40993 (@pxref{Remote Configuration}),
40994 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
40995 Only then may the stub actually turn off packet acknowledgments.
40996 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
40997 response, which can be safely ignored by the stub.
40999 Note that @code{set remote noack-packet} command only affects negotiation
41000 between @value{GDBN} and the stub when subsequent connections are made;
41001 it does not affect the protocol acknowledgment state for any current
41003 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
41004 new connection is established,
41005 there is also no protocol request to re-enable the acknowledgments
41006 for the current connection, once disabled.
41011 Example sequence of a target being re-started. Notice how the restart
41012 does not get any direct output:
41017 @emph{target restarts}
41020 <- @code{T001:1234123412341234}
41024 Example sequence of a target being stepped by a single instruction:
41027 -> @code{G1445@dots{}}
41032 <- @code{T001:1234123412341234}
41036 <- @code{1455@dots{}}
41040 @node File-I/O Remote Protocol Extension
41041 @section File-I/O Remote Protocol Extension
41042 @cindex File-I/O remote protocol extension
41045 * File-I/O Overview::
41046 * Protocol Basics::
41047 * The F Request Packet::
41048 * The F Reply Packet::
41049 * The Ctrl-C Message::
41051 * List of Supported Calls::
41052 * Protocol-specific Representation of Datatypes::
41054 * File-I/O Examples::
41057 @node File-I/O Overview
41058 @subsection File-I/O Overview
41059 @cindex file-i/o overview
41061 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
41062 target to use the host's file system and console I/O to perform various
41063 system calls. System calls on the target system are translated into a
41064 remote protocol packet to the host system, which then performs the needed
41065 actions and returns a response packet to the target system.
41066 This simulates file system operations even on targets that lack file systems.
41068 The protocol is defined to be independent of both the host and target systems.
41069 It uses its own internal representation of datatypes and values. Both
41070 @value{GDBN} and the target's @value{GDBN} stub are responsible for
41071 translating the system-dependent value representations into the internal
41072 protocol representations when data is transmitted.
41074 The communication is synchronous. A system call is possible only when
41075 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
41076 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
41077 the target is stopped to allow deterministic access to the target's
41078 memory. Therefore File-I/O is not interruptible by target signals. On
41079 the other hand, it is possible to interrupt File-I/O by a user interrupt
41080 (@samp{Ctrl-C}) within @value{GDBN}.
41082 The target's request to perform a host system call does not finish
41083 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
41084 after finishing the system call, the target returns to continuing the
41085 previous activity (continue, step). No additional continue or step
41086 request from @value{GDBN} is required.
41089 (@value{GDBP}) continue
41090 <- target requests 'system call X'
41091 target is stopped, @value{GDBN} executes system call
41092 -> @value{GDBN} returns result
41093 ... target continues, @value{GDBN} returns to wait for the target
41094 <- target hits breakpoint and sends a Txx packet
41097 The protocol only supports I/O on the console and to regular files on
41098 the host file system. Character or block special devices, pipes,
41099 named pipes, sockets or any other communication method on the host
41100 system are not supported by this protocol.
41102 File I/O is not supported in non-stop mode.
41104 @node Protocol Basics
41105 @subsection Protocol Basics
41106 @cindex protocol basics, file-i/o
41108 The File-I/O protocol uses the @code{F} packet as the request as well
41109 as reply packet. Since a File-I/O system call can only occur when
41110 @value{GDBN} is waiting for a response from the continuing or stepping target,
41111 the File-I/O request is a reply that @value{GDBN} has to expect as a result
41112 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
41113 This @code{F} packet contains all information needed to allow @value{GDBN}
41114 to call the appropriate host system call:
41118 A unique identifier for the requested system call.
41121 All parameters to the system call. Pointers are given as addresses
41122 in the target memory address space. Pointers to strings are given as
41123 pointer/length pair. Numerical values are given as they are.
41124 Numerical control flags are given in a protocol-specific representation.
41128 At this point, @value{GDBN} has to perform the following actions.
41132 If the parameters include pointer values to data needed as input to a
41133 system call, @value{GDBN} requests this data from the target with a
41134 standard @code{m} packet request. This additional communication has to be
41135 expected by the target implementation and is handled as any other @code{m}
41139 @value{GDBN} translates all value from protocol representation to host
41140 representation as needed. Datatypes are coerced into the host types.
41143 @value{GDBN} calls the system call.
41146 It then coerces datatypes back to protocol representation.
41149 If the system call is expected to return data in buffer space specified
41150 by pointer parameters to the call, the data is transmitted to the
41151 target using a @code{M} or @code{X} packet. This packet has to be expected
41152 by the target implementation and is handled as any other @code{M} or @code{X}
41157 Eventually @value{GDBN} replies with another @code{F} packet which contains all
41158 necessary information for the target to continue. This at least contains
41165 @code{errno}, if has been changed by the system call.
41172 After having done the needed type and value coercion, the target continues
41173 the latest continue or step action.
41175 @node The F Request Packet
41176 @subsection The @code{F} Request Packet
41177 @cindex file-i/o request packet
41178 @cindex @code{F} request packet
41180 The @code{F} request packet has the following format:
41183 @item F@var{call-id},@var{parameter@dots{}}
41185 @var{call-id} is the identifier to indicate the host system call to be called.
41186 This is just the name of the function.
41188 @var{parameter@dots{}} are the parameters to the system call.
41189 Parameters are hexadecimal integer values, either the actual values in case
41190 of scalar datatypes, pointers to target buffer space in case of compound
41191 datatypes and unspecified memory areas, or pointer/length pairs in case
41192 of string parameters. These are appended to the @var{call-id} as a
41193 comma-delimited list. All values are transmitted in ASCII
41194 string representation, pointer/length pairs separated by a slash.
41200 @node The F Reply Packet
41201 @subsection The @code{F} Reply Packet
41202 @cindex file-i/o reply packet
41203 @cindex @code{F} reply packet
41205 The @code{F} reply packet has the following format:
41209 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
41211 @var{retcode} is the return code of the system call as hexadecimal value.
41213 @var{errno} is the @code{errno} set by the call, in protocol-specific
41215 This parameter can be omitted if the call was successful.
41217 @var{Ctrl-C flag} is only sent if the user requested a break. In this
41218 case, @var{errno} must be sent as well, even if the call was successful.
41219 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
41226 or, if the call was interrupted before the host call has been performed:
41233 assuming 4 is the protocol-specific representation of @code{EINTR}.
41238 @node The Ctrl-C Message
41239 @subsection The @samp{Ctrl-C} Message
41240 @cindex ctrl-c message, in file-i/o protocol
41242 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
41243 reply packet (@pxref{The F Reply Packet}),
41244 the target should behave as if it had
41245 gotten a break message. The meaning for the target is ``system call
41246 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
41247 (as with a break message) and return to @value{GDBN} with a @code{T02}
41250 It's important for the target to know in which
41251 state the system call was interrupted. There are two possible cases:
41255 The system call hasn't been performed on the host yet.
41258 The system call on the host has been finished.
41262 These two states can be distinguished by the target by the value of the
41263 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
41264 call hasn't been performed. This is equivalent to the @code{EINTR} handling
41265 on POSIX systems. In any other case, the target may presume that the
41266 system call has been finished --- successfully or not --- and should behave
41267 as if the break message arrived right after the system call.
41269 @value{GDBN} must behave reliably. If the system call has not been called
41270 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
41271 @code{errno} in the packet. If the system call on the host has been finished
41272 before the user requests a break, the full action must be finished by
41273 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
41274 The @code{F} packet may only be sent when either nothing has happened
41275 or the full action has been completed.
41278 @subsection Console I/O
41279 @cindex console i/o as part of file-i/o
41281 By default and if not explicitly closed by the target system, the file
41282 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41283 on the @value{GDBN} console is handled as any other file output operation
41284 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41285 by @value{GDBN} so that after the target read request from file descriptor
41286 0 all following typing is buffered until either one of the following
41291 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41293 system call is treated as finished.
41296 The user presses @key{RET}. This is treated as end of input with a trailing
41300 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41301 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41305 If the user has typed more characters than fit in the buffer given to
41306 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41307 either another @code{read(0, @dots{})} is requested by the target, or debugging
41308 is stopped at the user's request.
41311 @node List of Supported Calls
41312 @subsection List of Supported Calls
41313 @cindex list of supported file-i/o calls
41330 @unnumberedsubsubsec open
41331 @cindex open, file-i/o system call
41336 int open(const char *pathname, int flags);
41337 int open(const char *pathname, int flags, mode_t mode);
41341 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41344 @var{flags} is the bitwise @code{OR} of the following values:
41348 If the file does not exist it will be created. The host
41349 rules apply as far as file ownership and time stamps
41353 When used with @code{O_CREAT}, if the file already exists it is
41354 an error and open() fails.
41357 If the file already exists and the open mode allows
41358 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41359 truncated to zero length.
41362 The file is opened in append mode.
41365 The file is opened for reading only.
41368 The file is opened for writing only.
41371 The file is opened for reading and writing.
41375 Other bits are silently ignored.
41379 @var{mode} is the bitwise @code{OR} of the following values:
41383 User has read permission.
41386 User has write permission.
41389 Group has read permission.
41392 Group has write permission.
41395 Others have read permission.
41398 Others have write permission.
41402 Other bits are silently ignored.
41405 @item Return value:
41406 @code{open} returns the new file descriptor or -1 if an error
41413 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41416 @var{pathname} refers to a directory.
41419 The requested access is not allowed.
41422 @var{pathname} was too long.
41425 A directory component in @var{pathname} does not exist.
41428 @var{pathname} refers to a device, pipe, named pipe or socket.
41431 @var{pathname} refers to a file on a read-only filesystem and
41432 write access was requested.
41435 @var{pathname} is an invalid pointer value.
41438 No space on device to create the file.
41441 The process already has the maximum number of files open.
41444 The limit on the total number of files open on the system
41448 The call was interrupted by the user.
41454 @unnumberedsubsubsec close
41455 @cindex close, file-i/o system call
41464 @samp{Fclose,@var{fd}}
41466 @item Return value:
41467 @code{close} returns zero on success, or -1 if an error occurred.
41473 @var{fd} isn't a valid open file descriptor.
41476 The call was interrupted by the user.
41482 @unnumberedsubsubsec read
41483 @cindex read, file-i/o system call
41488 int read(int fd, void *buf, unsigned int count);
41492 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41494 @item Return value:
41495 On success, the number of bytes read is returned.
41496 Zero indicates end of file. If count is zero, read
41497 returns zero as well. On error, -1 is returned.
41503 @var{fd} is not a valid file descriptor or is not open for
41507 @var{bufptr} is an invalid pointer value.
41510 The call was interrupted by the user.
41516 @unnumberedsubsubsec write
41517 @cindex write, file-i/o system call
41522 int write(int fd, const void *buf, unsigned int count);
41526 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41528 @item Return value:
41529 On success, the number of bytes written are returned.
41530 Zero indicates nothing was written. On error, -1
41537 @var{fd} is not a valid file descriptor or is not open for
41541 @var{bufptr} is an invalid pointer value.
41544 An attempt was made to write a file that exceeds the
41545 host-specific maximum file size allowed.
41548 No space on device to write the data.
41551 The call was interrupted by the user.
41557 @unnumberedsubsubsec lseek
41558 @cindex lseek, file-i/o system call
41563 long lseek (int fd, long offset, int flag);
41567 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41569 @var{flag} is one of:
41573 The offset is set to @var{offset} bytes.
41576 The offset is set to its current location plus @var{offset}
41580 The offset is set to the size of the file plus @var{offset}
41584 @item Return value:
41585 On success, the resulting unsigned offset in bytes from
41586 the beginning of the file is returned. Otherwise, a
41587 value of -1 is returned.
41593 @var{fd} is not a valid open file descriptor.
41596 @var{fd} is associated with the @value{GDBN} console.
41599 @var{flag} is not a proper value.
41602 The call was interrupted by the user.
41608 @unnumberedsubsubsec rename
41609 @cindex rename, file-i/o system call
41614 int rename(const char *oldpath, const char *newpath);
41618 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41620 @item Return value:
41621 On success, zero is returned. On error, -1 is returned.
41627 @var{newpath} is an existing directory, but @var{oldpath} is not a
41631 @var{newpath} is a non-empty directory.
41634 @var{oldpath} or @var{newpath} is a directory that is in use by some
41638 An attempt was made to make a directory a subdirectory
41642 A component used as a directory in @var{oldpath} or new
41643 path is not a directory. Or @var{oldpath} is a directory
41644 and @var{newpath} exists but is not a directory.
41647 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41650 No access to the file or the path of the file.
41654 @var{oldpath} or @var{newpath} was too long.
41657 A directory component in @var{oldpath} or @var{newpath} does not exist.
41660 The file is on a read-only filesystem.
41663 The device containing the file has no room for the new
41667 The call was interrupted by the user.
41673 @unnumberedsubsubsec unlink
41674 @cindex unlink, file-i/o system call
41679 int unlink(const char *pathname);
41683 @samp{Funlink,@var{pathnameptr}/@var{len}}
41685 @item Return value:
41686 On success, zero is returned. On error, -1 is returned.
41692 No access to the file or the path of the file.
41695 The system does not allow unlinking of directories.
41698 The file @var{pathname} cannot be unlinked because it's
41699 being used by another process.
41702 @var{pathnameptr} is an invalid pointer value.
41705 @var{pathname} was too long.
41708 A directory component in @var{pathname} does not exist.
41711 A component of the path is not a directory.
41714 The file is on a read-only filesystem.
41717 The call was interrupted by the user.
41723 @unnumberedsubsubsec stat/fstat
41724 @cindex fstat, file-i/o system call
41725 @cindex stat, file-i/o system call
41730 int stat(const char *pathname, struct stat *buf);
41731 int fstat(int fd, struct stat *buf);
41735 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41736 @samp{Ffstat,@var{fd},@var{bufptr}}
41738 @item Return value:
41739 On success, zero is returned. On error, -1 is returned.
41745 @var{fd} is not a valid open file.
41748 A directory component in @var{pathname} does not exist or the
41749 path is an empty string.
41752 A component of the path is not a directory.
41755 @var{pathnameptr} is an invalid pointer value.
41758 No access to the file or the path of the file.
41761 @var{pathname} was too long.
41764 The call was interrupted by the user.
41770 @unnumberedsubsubsec gettimeofday
41771 @cindex gettimeofday, file-i/o system call
41776 int gettimeofday(struct timeval *tv, void *tz);
41780 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41782 @item Return value:
41783 On success, 0 is returned, -1 otherwise.
41789 @var{tz} is a non-NULL pointer.
41792 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41798 @unnumberedsubsubsec isatty
41799 @cindex isatty, file-i/o system call
41804 int isatty(int fd);
41808 @samp{Fisatty,@var{fd}}
41810 @item Return value:
41811 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
41817 The call was interrupted by the user.
41822 Note that the @code{isatty} call is treated as a special case: it returns
41823 1 to the target if the file descriptor is attached
41824 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
41825 would require implementing @code{ioctl} and would be more complex than
41830 @unnumberedsubsubsec system
41831 @cindex system, file-i/o system call
41836 int system(const char *command);
41840 @samp{Fsystem,@var{commandptr}/@var{len}}
41842 @item Return value:
41843 If @var{len} is zero, the return value indicates whether a shell is
41844 available. A zero return value indicates a shell is not available.
41845 For non-zero @var{len}, the value returned is -1 on error and the
41846 return status of the command otherwise. Only the exit status of the
41847 command is returned, which is extracted from the host's @code{system}
41848 return value by calling @code{WEXITSTATUS(retval)}. In case
41849 @file{/bin/sh} could not be executed, 127 is returned.
41855 The call was interrupted by the user.
41860 @value{GDBN} takes over the full task of calling the necessary host calls
41861 to perform the @code{system} call. The return value of @code{system} on
41862 the host is simplified before it's returned
41863 to the target. Any termination signal information from the child process
41864 is discarded, and the return value consists
41865 entirely of the exit status of the called command.
41867 Due to security concerns, the @code{system} call is by default refused
41868 by @value{GDBN}. The user has to allow this call explicitly with the
41869 @code{set remote system-call-allowed 1} command.
41872 @item set remote system-call-allowed
41873 @kindex set remote system-call-allowed
41874 Control whether to allow the @code{system} calls in the File I/O
41875 protocol for the remote target. The default is zero (disabled).
41877 @item show remote system-call-allowed
41878 @kindex show remote system-call-allowed
41879 Show whether the @code{system} calls are allowed in the File I/O
41883 @node Protocol-specific Representation of Datatypes
41884 @subsection Protocol-specific Representation of Datatypes
41885 @cindex protocol-specific representation of datatypes, in file-i/o protocol
41888 * Integral Datatypes::
41890 * Memory Transfer::
41895 @node Integral Datatypes
41896 @unnumberedsubsubsec Integral Datatypes
41897 @cindex integral datatypes, in file-i/o protocol
41899 The integral datatypes used in the system calls are @code{int},
41900 @code{unsigned int}, @code{long}, @code{unsigned long},
41901 @code{mode_t}, and @code{time_t}.
41903 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
41904 implemented as 32 bit values in this protocol.
41906 @code{long} and @code{unsigned long} are implemented as 64 bit types.
41908 @xref{Limits}, for corresponding MIN and MAX values (similar to those
41909 in @file{limits.h}) to allow range checking on host and target.
41911 @code{time_t} datatypes are defined as seconds since the Epoch.
41913 All integral datatypes transferred as part of a memory read or write of a
41914 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
41917 @node Pointer Values
41918 @unnumberedsubsubsec Pointer Values
41919 @cindex pointer values, in file-i/o protocol
41921 Pointers to target data are transmitted as they are. An exception
41922 is made for pointers to buffers for which the length isn't
41923 transmitted as part of the function call, namely strings. Strings
41924 are transmitted as a pointer/length pair, both as hex values, e.g.@:
41931 which is a pointer to data of length 18 bytes at position 0x1aaf.
41932 The length is defined as the full string length in bytes, including
41933 the trailing null byte. For example, the string @code{"hello world"}
41934 at address 0x123456 is transmitted as
41940 @node Memory Transfer
41941 @unnumberedsubsubsec Memory Transfer
41942 @cindex memory transfer, in file-i/o protocol
41944 Structured data which is transferred using a memory read or write (for
41945 example, a @code{struct stat}) is expected to be in a protocol-specific format
41946 with all scalar multibyte datatypes being big endian. Translation to
41947 this representation needs to be done both by the target before the @code{F}
41948 packet is sent, and by @value{GDBN} before
41949 it transfers memory to the target. Transferred pointers to structured
41950 data should point to the already-coerced data at any time.
41954 @unnumberedsubsubsec struct stat
41955 @cindex struct stat, in file-i/o protocol
41957 The buffer of type @code{struct stat} used by the target and @value{GDBN}
41958 is defined as follows:
41962 unsigned int st_dev; /* device */
41963 unsigned int st_ino; /* inode */
41964 mode_t st_mode; /* protection */
41965 unsigned int st_nlink; /* number of hard links */
41966 unsigned int st_uid; /* user ID of owner */
41967 unsigned int st_gid; /* group ID of owner */
41968 unsigned int st_rdev; /* device type (if inode device) */
41969 unsigned long st_size; /* total size, in bytes */
41970 unsigned long st_blksize; /* blocksize for filesystem I/O */
41971 unsigned long st_blocks; /* number of blocks allocated */
41972 time_t st_atime; /* time of last access */
41973 time_t st_mtime; /* time of last modification */
41974 time_t st_ctime; /* time of last change */
41978 The integral datatypes conform to the definitions given in the
41979 appropriate section (see @ref{Integral Datatypes}, for details) so this
41980 structure is of size 64 bytes.
41982 The values of several fields have a restricted meaning and/or
41988 A value of 0 represents a file, 1 the console.
41991 No valid meaning for the target. Transmitted unchanged.
41994 Valid mode bits are described in @ref{Constants}. Any other
41995 bits have currently no meaning for the target.
42000 No valid meaning for the target. Transmitted unchanged.
42005 These values have a host and file system dependent
42006 accuracy. Especially on Windows hosts, the file system may not
42007 support exact timing values.
42010 The target gets a @code{struct stat} of the above representation and is
42011 responsible for coercing it to the target representation before
42014 Note that due to size differences between the host, target, and protocol
42015 representations of @code{struct stat} members, these members could eventually
42016 get truncated on the target.
42018 @node struct timeval
42019 @unnumberedsubsubsec struct timeval
42020 @cindex struct timeval, in file-i/o protocol
42022 The buffer of type @code{struct timeval} used by the File-I/O protocol
42023 is defined as follows:
42027 time_t tv_sec; /* second */
42028 long tv_usec; /* microsecond */
42032 The integral datatypes conform to the definitions given in the
42033 appropriate section (see @ref{Integral Datatypes}, for details) so this
42034 structure is of size 8 bytes.
42037 @subsection Constants
42038 @cindex constants, in file-i/o protocol
42040 The following values are used for the constants inside of the
42041 protocol. @value{GDBN} and target are responsible for translating these
42042 values before and after the call as needed.
42053 @unnumberedsubsubsec Open Flags
42054 @cindex open flags, in file-i/o protocol
42056 All values are given in hexadecimal representation.
42068 @node mode_t Values
42069 @unnumberedsubsubsec mode_t Values
42070 @cindex mode_t values, in file-i/o protocol
42072 All values are given in octal representation.
42089 @unnumberedsubsubsec Errno Values
42090 @cindex errno values, in file-i/o protocol
42092 All values are given in decimal representation.
42117 @code{EUNKNOWN} is used as a fallback error value if a host system returns
42118 any error value not in the list of supported error numbers.
42121 @unnumberedsubsubsec Lseek Flags
42122 @cindex lseek flags, in file-i/o protocol
42131 @unnumberedsubsubsec Limits
42132 @cindex limits, in file-i/o protocol
42134 All values are given in decimal representation.
42137 INT_MIN -2147483648
42139 UINT_MAX 4294967295
42140 LONG_MIN -9223372036854775808
42141 LONG_MAX 9223372036854775807
42142 ULONG_MAX 18446744073709551615
42145 @node File-I/O Examples
42146 @subsection File-I/O Examples
42147 @cindex file-i/o examples
42149 Example sequence of a write call, file descriptor 3, buffer is at target
42150 address 0x1234, 6 bytes should be written:
42153 <- @code{Fwrite,3,1234,6}
42154 @emph{request memory read from target}
42157 @emph{return "6 bytes written"}
42161 Example sequence of a read call, file descriptor 3, buffer is at target
42162 address 0x1234, 6 bytes should be read:
42165 <- @code{Fread,3,1234,6}
42166 @emph{request memory write to target}
42167 -> @code{X1234,6:XXXXXX}
42168 @emph{return "6 bytes read"}
42172 Example sequence of a read call, call fails on the host due to invalid
42173 file descriptor (@code{EBADF}):
42176 <- @code{Fread,3,1234,6}
42180 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
42184 <- @code{Fread,3,1234,6}
42189 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
42193 <- @code{Fread,3,1234,6}
42194 -> @code{X1234,6:XXXXXX}
42198 @node Library List Format
42199 @section Library List Format
42200 @cindex library list format, remote protocol
42202 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
42203 same process as your application to manage libraries. In this case,
42204 @value{GDBN} can use the loader's symbol table and normal memory
42205 operations to maintain a list of shared libraries. On other
42206 platforms, the operating system manages loaded libraries.
42207 @value{GDBN} can not retrieve the list of currently loaded libraries
42208 through memory operations, so it uses the @samp{qXfer:libraries:read}
42209 packet (@pxref{qXfer library list read}) instead. The remote stub
42210 queries the target's operating system and reports which libraries
42213 The @samp{qXfer:libraries:read} packet returns an XML document which
42214 lists loaded libraries and their offsets. Each library has an
42215 associated name and one or more segment or section base addresses,
42216 which report where the library was loaded in memory.
42218 For the common case of libraries that are fully linked binaries, the
42219 library should have a list of segments. If the target supports
42220 dynamic linking of a relocatable object file, its library XML element
42221 should instead include a list of allocated sections. The segment or
42222 section bases are start addresses, not relocation offsets; they do not
42223 depend on the library's link-time base addresses.
42225 @value{GDBN} must be linked with the Expat library to support XML
42226 library lists. @xref{Expat}.
42228 A simple memory map, with one loaded library relocated by a single
42229 offset, looks like this:
42233 <library name="/lib/libc.so.6">
42234 <segment address="0x10000000"/>
42239 Another simple memory map, with one loaded library with three
42240 allocated sections (.text, .data, .bss), looks like this:
42244 <library name="sharedlib.o">
42245 <section address="0x10000000"/>
42246 <section address="0x20000000"/>
42247 <section address="0x30000000"/>
42252 The format of a library list is described by this DTD:
42255 <!-- library-list: Root element with versioning -->
42256 <!ELEMENT library-list (library)*>
42257 <!ATTLIST library-list version CDATA #FIXED "1.0">
42258 <!ELEMENT library (segment*, section*)>
42259 <!ATTLIST library name CDATA #REQUIRED>
42260 <!ELEMENT segment EMPTY>
42261 <!ATTLIST segment address CDATA #REQUIRED>
42262 <!ELEMENT section EMPTY>
42263 <!ATTLIST section address CDATA #REQUIRED>
42266 In addition, segments and section descriptors cannot be mixed within a
42267 single library element, and you must supply at least one segment or
42268 section for each library.
42270 @node Library List Format for SVR4 Targets
42271 @section Library List Format for SVR4 Targets
42272 @cindex library list format, remote protocol
42274 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
42275 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42276 shared libraries. Still a special library list provided by this packet is
42277 more efficient for the @value{GDBN} remote protocol.
42279 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42280 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42281 target, the following parameters are reported:
42285 @code{name}, the absolute file name from the @code{l_name} field of
42286 @code{struct link_map}.
42288 @code{lm} with address of @code{struct link_map} used for TLS
42289 (Thread Local Storage) access.
42291 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42292 @code{struct link_map}. For prelinked libraries this is not an absolute
42293 memory address. It is a displacement of absolute memory address against
42294 address the file was prelinked to during the library load.
42296 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42299 Additionally the single @code{main-lm} attribute specifies address of
42300 @code{struct link_map} used for the main executable. This parameter is used
42301 for TLS access and its presence is optional.
42303 @value{GDBN} must be linked with the Expat library to support XML
42304 SVR4 library lists. @xref{Expat}.
42306 A simple memory map, with two loaded libraries (which do not use prelink),
42310 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42311 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42313 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42315 </library-list-svr>
42318 The format of an SVR4 library list is described by this DTD:
42321 <!-- library-list-svr4: Root element with versioning -->
42322 <!ELEMENT library-list-svr4 (library)*>
42323 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42324 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42325 <!ELEMENT library EMPTY>
42326 <!ATTLIST library name CDATA #REQUIRED>
42327 <!ATTLIST library lm CDATA #REQUIRED>
42328 <!ATTLIST library l_addr CDATA #REQUIRED>
42329 <!ATTLIST library l_ld CDATA #REQUIRED>
42332 @node Memory Map Format
42333 @section Memory Map Format
42334 @cindex memory map format
42336 To be able to write into flash memory, @value{GDBN} needs to obtain a
42337 memory map from the target. This section describes the format of the
42340 The memory map is obtained using the @samp{qXfer:memory-map:read}
42341 (@pxref{qXfer memory map read}) packet and is an XML document that
42342 lists memory regions.
42344 @value{GDBN} must be linked with the Expat library to support XML
42345 memory maps. @xref{Expat}.
42347 The top-level structure of the document is shown below:
42350 <?xml version="1.0"?>
42351 <!DOCTYPE memory-map
42352 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42353 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42359 Each region can be either:
42364 A region of RAM starting at @var{addr} and extending for @var{length}
42368 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42373 A region of read-only memory:
42376 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42381 A region of flash memory, with erasure blocks @var{blocksize}
42385 <memory type="flash" start="@var{addr}" length="@var{length}">
42386 <property name="blocksize">@var{blocksize}</property>
42392 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42393 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42394 packets to write to addresses in such ranges.
42396 The formal DTD for memory map format is given below:
42399 <!-- ................................................... -->
42400 <!-- Memory Map XML DTD ................................ -->
42401 <!-- File: memory-map.dtd .............................. -->
42402 <!-- .................................... .............. -->
42403 <!-- memory-map.dtd -->
42404 <!-- memory-map: Root element with versioning -->
42405 <!ELEMENT memory-map (memory)*>
42406 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42407 <!ELEMENT memory (property)*>
42408 <!-- memory: Specifies a memory region,
42409 and its type, or device. -->
42410 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
42411 start CDATA #REQUIRED
42412 length CDATA #REQUIRED>
42413 <!-- property: Generic attribute tag -->
42414 <!ELEMENT property (#PCDATA | property)*>
42415 <!ATTLIST property name (blocksize) #REQUIRED>
42418 @node Thread List Format
42419 @section Thread List Format
42420 @cindex thread list format
42422 To efficiently update the list of threads and their attributes,
42423 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42424 (@pxref{qXfer threads read}) and obtains the XML document with
42425 the following structure:
42428 <?xml version="1.0"?>
42430 <thread id="id" core="0" name="name">
42431 ... description ...
42436 Each @samp{thread} element must have the @samp{id} attribute that
42437 identifies the thread (@pxref{thread-id syntax}). The
42438 @samp{core} attribute, if present, specifies which processor core
42439 the thread was last executing on. The @samp{name} attribute, if
42440 present, specifies the human-readable name of the thread. The content
42441 of the of @samp{thread} element is interpreted as human-readable
42442 auxiliary information. The @samp{handle} attribute, if present,
42443 is a hex encoded representation of the thread handle.
42446 @node Traceframe Info Format
42447 @section Traceframe Info Format
42448 @cindex traceframe info format
42450 To be able to know which objects in the inferior can be examined when
42451 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42452 memory ranges, registers and trace state variables that have been
42453 collected in a traceframe.
42455 This list is obtained using the @samp{qXfer:traceframe-info:read}
42456 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42458 @value{GDBN} must be linked with the Expat library to support XML
42459 traceframe info discovery. @xref{Expat}.
42461 The top-level structure of the document is shown below:
42464 <?xml version="1.0"?>
42465 <!DOCTYPE traceframe-info
42466 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42467 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42473 Each traceframe block can be either:
42478 A region of collected memory starting at @var{addr} and extending for
42479 @var{length} bytes from there:
42482 <memory start="@var{addr}" length="@var{length}"/>
42486 A block indicating trace state variable numbered @var{number} has been
42490 <tvar id="@var{number}"/>
42495 The formal DTD for the traceframe info format is given below:
42498 <!ELEMENT traceframe-info (memory | tvar)* >
42499 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42501 <!ELEMENT memory EMPTY>
42502 <!ATTLIST memory start CDATA #REQUIRED
42503 length CDATA #REQUIRED>
42505 <!ATTLIST tvar id CDATA #REQUIRED>
42508 @node Branch Trace Format
42509 @section Branch Trace Format
42510 @cindex branch trace format
42512 In order to display the branch trace of an inferior thread,
42513 @value{GDBN} needs to obtain the list of branches. This list is
42514 represented as list of sequential code blocks that are connected via
42515 branches. The code in each block has been executed sequentially.
42517 This list is obtained using the @samp{qXfer:btrace:read}
42518 (@pxref{qXfer btrace read}) packet and is an XML document.
42520 @value{GDBN} must be linked with the Expat library to support XML
42521 traceframe info discovery. @xref{Expat}.
42523 The top-level structure of the document is shown below:
42526 <?xml version="1.0"?>
42528 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42529 "http://sourceware.org/gdb/gdb-btrace.dtd">
42538 A block of sequentially executed instructions starting at @var{begin}
42539 and ending at @var{end}:
42542 <block begin="@var{begin}" end="@var{end}"/>
42547 The formal DTD for the branch trace format is given below:
42550 <!ELEMENT btrace (block* | pt) >
42551 <!ATTLIST btrace version CDATA #FIXED "1.0">
42553 <!ELEMENT block EMPTY>
42554 <!ATTLIST block begin CDATA #REQUIRED
42555 end CDATA #REQUIRED>
42557 <!ELEMENT pt (pt-config?, raw?)>
42559 <!ELEMENT pt-config (cpu?)>
42561 <!ELEMENT cpu EMPTY>
42562 <!ATTLIST cpu vendor CDATA #REQUIRED
42563 family CDATA #REQUIRED
42564 model CDATA #REQUIRED
42565 stepping CDATA #REQUIRED>
42567 <!ELEMENT raw (#PCDATA)>
42570 @node Branch Trace Configuration Format
42571 @section Branch Trace Configuration Format
42572 @cindex branch trace configuration format
42574 For each inferior thread, @value{GDBN} can obtain the branch trace
42575 configuration using the @samp{qXfer:btrace-conf:read}
42576 (@pxref{qXfer btrace-conf read}) packet.
42578 The configuration describes the branch trace format and configuration
42579 settings for that format. The following information is described:
42583 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
42586 The size of the @acronym{BTS} ring buffer in bytes.
42589 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
42593 The size of the @acronym{Intel PT} ring buffer in bytes.
42597 @value{GDBN} must be linked with the Expat library to support XML
42598 branch trace configuration discovery. @xref{Expat}.
42600 The formal DTD for the branch trace configuration format is given below:
42603 <!ELEMENT btrace-conf (bts?, pt?)>
42604 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
42606 <!ELEMENT bts EMPTY>
42607 <!ATTLIST bts size CDATA #IMPLIED>
42609 <!ELEMENT pt EMPTY>
42610 <!ATTLIST pt size CDATA #IMPLIED>
42613 @include agentexpr.texi
42615 @node Target Descriptions
42616 @appendix Target Descriptions
42617 @cindex target descriptions
42619 One of the challenges of using @value{GDBN} to debug embedded systems
42620 is that there are so many minor variants of each processor
42621 architecture in use. It is common practice for vendors to start with
42622 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42623 and then make changes to adapt it to a particular market niche. Some
42624 architectures have hundreds of variants, available from dozens of
42625 vendors. This leads to a number of problems:
42629 With so many different customized processors, it is difficult for
42630 the @value{GDBN} maintainers to keep up with the changes.
42632 Since individual variants may have short lifetimes or limited
42633 audiences, it may not be worthwhile to carry information about every
42634 variant in the @value{GDBN} source tree.
42636 When @value{GDBN} does support the architecture of the embedded system
42637 at hand, the task of finding the correct architecture name to give the
42638 @command{set architecture} command can be error-prone.
42641 To address these problems, the @value{GDBN} remote protocol allows a
42642 target system to not only identify itself to @value{GDBN}, but to
42643 actually describe its own features. This lets @value{GDBN} support
42644 processor variants it has never seen before --- to the extent that the
42645 descriptions are accurate, and that @value{GDBN} understands them.
42647 @value{GDBN} must be linked with the Expat library to support XML
42648 target descriptions. @xref{Expat}.
42651 * Retrieving Descriptions:: How descriptions are fetched from a target.
42652 * Target Description Format:: The contents of a target description.
42653 * Predefined Target Types:: Standard types available for target
42655 * Enum Target Types:: How to define enum target types.
42656 * Standard Target Features:: Features @value{GDBN} knows about.
42659 @node Retrieving Descriptions
42660 @section Retrieving Descriptions
42662 Target descriptions can be read from the target automatically, or
42663 specified by the user manually. The default behavior is to read the
42664 description from the target. @value{GDBN} retrieves it via the remote
42665 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42666 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42667 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42668 XML document, of the form described in @ref{Target Description
42671 Alternatively, you can specify a file to read for the target description.
42672 If a file is set, the target will not be queried. The commands to
42673 specify a file are:
42676 @cindex set tdesc filename
42677 @item set tdesc filename @var{path}
42678 Read the target description from @var{path}.
42680 @cindex unset tdesc filename
42681 @item unset tdesc filename
42682 Do not read the XML target description from a file. @value{GDBN}
42683 will use the description supplied by the current target.
42685 @cindex show tdesc filename
42686 @item show tdesc filename
42687 Show the filename to read for a target description, if any.
42691 @node Target Description Format
42692 @section Target Description Format
42693 @cindex target descriptions, XML format
42695 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42696 document which complies with the Document Type Definition provided in
42697 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42698 means you can use generally available tools like @command{xmllint} to
42699 check that your feature descriptions are well-formed and valid.
42700 However, to help people unfamiliar with XML write descriptions for
42701 their targets, we also describe the grammar here.
42703 Target descriptions can identify the architecture of the remote target
42704 and (for some architectures) provide information about custom register
42705 sets. They can also identify the OS ABI of the remote target.
42706 @value{GDBN} can use this information to autoconfigure for your
42707 target, or to warn you if you connect to an unsupported target.
42709 Here is a simple target description:
42712 <target version="1.0">
42713 <architecture>i386:x86-64</architecture>
42718 This minimal description only says that the target uses
42719 the x86-64 architecture.
42721 A target description has the following overall form, with [ ] marking
42722 optional elements and @dots{} marking repeatable elements. The elements
42723 are explained further below.
42726 <?xml version="1.0"?>
42727 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42728 <target version="1.0">
42729 @r{[}@var{architecture}@r{]}
42730 @r{[}@var{osabi}@r{]}
42731 @r{[}@var{compatible}@r{]}
42732 @r{[}@var{feature}@dots{}@r{]}
42737 The description is generally insensitive to whitespace and line
42738 breaks, under the usual common-sense rules. The XML version
42739 declaration and document type declaration can generally be omitted
42740 (@value{GDBN} does not require them), but specifying them may be
42741 useful for XML validation tools. The @samp{version} attribute for
42742 @samp{<target>} may also be omitted, but we recommend
42743 including it; if future versions of @value{GDBN} use an incompatible
42744 revision of @file{gdb-target.dtd}, they will detect and report
42745 the version mismatch.
42747 @subsection Inclusion
42748 @cindex target descriptions, inclusion
42751 @cindex <xi:include>
42754 It can sometimes be valuable to split a target description up into
42755 several different annexes, either for organizational purposes, or to
42756 share files between different possible target descriptions. You can
42757 divide a description into multiple files by replacing any element of
42758 the target description with an inclusion directive of the form:
42761 <xi:include href="@var{document}"/>
42765 When @value{GDBN} encounters an element of this form, it will retrieve
42766 the named XML @var{document}, and replace the inclusion directive with
42767 the contents of that document. If the current description was read
42768 using @samp{qXfer}, then so will be the included document;
42769 @var{document} will be interpreted as the name of an annex. If the
42770 current description was read from a file, @value{GDBN} will look for
42771 @var{document} as a file in the same directory where it found the
42772 original description.
42774 @subsection Architecture
42775 @cindex <architecture>
42777 An @samp{<architecture>} element has this form:
42780 <architecture>@var{arch}</architecture>
42783 @var{arch} is one of the architectures from the set accepted by
42784 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42787 @cindex @code{<osabi>}
42789 This optional field was introduced in @value{GDBN} version 7.0.
42790 Previous versions of @value{GDBN} ignore it.
42792 An @samp{<osabi>} element has this form:
42795 <osabi>@var{abi-name}</osabi>
42798 @var{abi-name} is an OS ABI name from the same selection accepted by
42799 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42801 @subsection Compatible Architecture
42802 @cindex @code{<compatible>}
42804 This optional field was introduced in @value{GDBN} version 7.0.
42805 Previous versions of @value{GDBN} ignore it.
42807 A @samp{<compatible>} element has this form:
42810 <compatible>@var{arch}</compatible>
42813 @var{arch} is one of the architectures from the set accepted by
42814 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42816 A @samp{<compatible>} element is used to specify that the target
42817 is able to run binaries in some other than the main target architecture
42818 given by the @samp{<architecture>} element. For example, on the
42819 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42820 or @code{powerpc:common64}, but the system is able to run binaries
42821 in the @code{spu} architecture as well. The way to describe this
42822 capability with @samp{<compatible>} is as follows:
42825 <architecture>powerpc:common</architecture>
42826 <compatible>spu</compatible>
42829 @subsection Features
42832 Each @samp{<feature>} describes some logical portion of the target
42833 system. Features are currently used to describe available CPU
42834 registers and the types of their contents. A @samp{<feature>} element
42838 <feature name="@var{name}">
42839 @r{[}@var{type}@dots{}@r{]}
42845 Each feature's name should be unique within the description. The name
42846 of a feature does not matter unless @value{GDBN} has some special
42847 knowledge of the contents of that feature; if it does, the feature
42848 should have its standard name. @xref{Standard Target Features}.
42852 Any register's value is a collection of bits which @value{GDBN} must
42853 interpret. The default interpretation is a two's complement integer,
42854 but other types can be requested by name in the register description.
42855 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
42856 Target Types}), and the description can define additional composite
42859 Each type element must have an @samp{id} attribute, which gives
42860 a unique (within the containing @samp{<feature>}) name to the type.
42861 Types must be defined before they are used.
42864 Some targets offer vector registers, which can be treated as arrays
42865 of scalar elements. These types are written as @samp{<vector>} elements,
42866 specifying the array element type, @var{type}, and the number of elements,
42870 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
42874 If a register's value is usefully viewed in multiple ways, define it
42875 with a union type containing the useful representations. The
42876 @samp{<union>} element contains one or more @samp{<field>} elements,
42877 each of which has a @var{name} and a @var{type}:
42880 <union id="@var{id}">
42881 <field name="@var{name}" type="@var{type}"/>
42888 If a register's value is composed from several separate values, define
42889 it with either a structure type or a flags type.
42890 A flags type may only contain bitfields.
42891 A structure type may either contain only bitfields or contain no bitfields.
42892 If the value contains only bitfields, its total size in bytes must be
42895 Non-bitfield values have a @var{name} and @var{type}.
42898 <struct id="@var{id}">
42899 <field name="@var{name}" type="@var{type}"/>
42904 Both @var{name} and @var{type} values are required.
42905 No implicit padding is added.
42907 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
42910 <struct id="@var{id}" size="@var{size}">
42911 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
42917 <flags id="@var{id}" size="@var{size}">
42918 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
42923 The @var{name} value is required.
42924 Bitfield values may be named with the empty string, @samp{""},
42925 in which case the field is ``filler'' and its value is not printed.
42926 Not all bits need to be specified, so ``filler'' fields are optional.
42928 The @var{start} and @var{end} values are required, and @var{type}
42930 The field's @var{start} must be less than or equal to its @var{end},
42931 and zero represents the least significant bit.
42933 The default value of @var{type} is @code{bool} for single bit fields,
42934 and an unsigned integer otherwise.
42936 Which to choose? Structures or flags?
42938 Registers defined with @samp{flags} have these advantages over
42939 defining them with @samp{struct}:
42943 Arithmetic may be performed on them as if they were integers.
42945 They are printed in a more readable fashion.
42948 Registers defined with @samp{struct} have one advantage over
42949 defining them with @samp{flags}:
42953 One can fetch individual fields like in @samp{C}.
42956 (gdb) print $my_struct_reg.field3
42962 @subsection Registers
42965 Each register is represented as an element with this form:
42968 <reg name="@var{name}"
42969 bitsize="@var{size}"
42970 @r{[}regnum="@var{num}"@r{]}
42971 @r{[}save-restore="@var{save-restore}"@r{]}
42972 @r{[}type="@var{type}"@r{]}
42973 @r{[}group="@var{group}"@r{]}/>
42977 The components are as follows:
42982 The register's name; it must be unique within the target description.
42985 The register's size, in bits.
42988 The register's number. If omitted, a register's number is one greater
42989 than that of the previous register (either in the current feature or in
42990 a preceding feature); the first register in the target description
42991 defaults to zero. This register number is used to read or write
42992 the register; e.g.@: it is used in the remote @code{p} and @code{P}
42993 packets, and registers appear in the @code{g} and @code{G} packets
42994 in order of increasing register number.
42997 Whether the register should be preserved across inferior function
42998 calls; this must be either @code{yes} or @code{no}. The default is
42999 @code{yes}, which is appropriate for most registers except for
43000 some system control registers; this is not related to the target's
43004 The type of the register. It may be a predefined type, a type
43005 defined in the current feature, or one of the special types @code{int}
43006 and @code{float}. @code{int} is an integer type of the correct size
43007 for @var{bitsize}, and @code{float} is a floating point type (in the
43008 architecture's normal floating point format) of the correct size for
43009 @var{bitsize}. The default is @code{int}.
43012 The register group to which this register belongs. It can be one of the
43013 standard register groups @code{general}, @code{float}, @code{vector} or an
43014 arbitrary string. Group names should be limited to alphanumeric characters.
43015 If a group name is made up of multiple words the words may be separated by
43016 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
43017 @var{group} is specified, @value{GDBN} will not display the register in
43018 @code{info registers}.
43022 @node Predefined Target Types
43023 @section Predefined Target Types
43024 @cindex target descriptions, predefined types
43026 Type definitions in the self-description can build up composite types
43027 from basic building blocks, but can not define fundamental types. Instead,
43028 standard identifiers are provided by @value{GDBN} for the fundamental
43029 types. The currently supported types are:
43034 Boolean type, occupying a single bit.
43042 Signed integer types holding the specified number of bits.
43050 Unsigned integer types holding the specified number of bits.
43054 Pointers to unspecified code and data. The program counter and
43055 any dedicated return address register may be marked as code
43056 pointers; printing a code pointer converts it into a symbolic
43057 address. The stack pointer and any dedicated address registers
43058 may be marked as data pointers.
43061 Single precision IEEE floating point.
43064 Double precision IEEE floating point.
43067 The 12-byte extended precision format used by ARM FPA registers.
43070 The 10-byte extended precision format used by x87 registers.
43073 32bit @sc{eflags} register used by x86.
43076 32bit @sc{mxcsr} register used by x86.
43080 @node Enum Target Types
43081 @section Enum Target Types
43082 @cindex target descriptions, enum types
43084 Enum target types are useful in @samp{struct} and @samp{flags}
43085 register descriptions. @xref{Target Description Format}.
43087 Enum types have a name, size and a list of name/value pairs.
43090 <enum id="@var{id}" size="@var{size}">
43091 <evalue name="@var{name}" value="@var{value}"/>
43096 Enums must be defined before they are used.
43099 <enum id="levels_type" size="4">
43100 <evalue name="low" value="0"/>
43101 <evalue name="high" value="1"/>
43103 <flags id="flags_type" size="4">
43104 <field name="X" start="0"/>
43105 <field name="LEVEL" start="1" end="1" type="levels_type"/>
43107 <reg name="flags" bitsize="32" type="flags_type"/>
43110 Given that description, a value of 3 for the @samp{flags} register
43111 would be printed as:
43114 (gdb) info register flags
43115 flags 0x3 [ X LEVEL=high ]
43118 @node Standard Target Features
43119 @section Standard Target Features
43120 @cindex target descriptions, standard features
43122 A target description must contain either no registers or all the
43123 target's registers. If the description contains no registers, then
43124 @value{GDBN} will assume a default register layout, selected based on
43125 the architecture. If the description contains any registers, the
43126 default layout will not be used; the standard registers must be
43127 described in the target description, in such a way that @value{GDBN}
43128 can recognize them.
43130 This is accomplished by giving specific names to feature elements
43131 which contain standard registers. @value{GDBN} will look for features
43132 with those names and verify that they contain the expected registers;
43133 if any known feature is missing required registers, or if any required
43134 feature is missing, @value{GDBN} will reject the target
43135 description. You can add additional registers to any of the
43136 standard features --- @value{GDBN} will display them just as if
43137 they were added to an unrecognized feature.
43139 This section lists the known features and their expected contents.
43140 Sample XML documents for these features are included in the
43141 @value{GDBN} source tree, in the directory @file{gdb/features}.
43143 Names recognized by @value{GDBN} should include the name of the
43144 company or organization which selected the name, and the overall
43145 architecture to which the feature applies; so e.g.@: the feature
43146 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
43148 The names of registers are not case sensitive for the purpose
43149 of recognizing standard features, but @value{GDBN} will only display
43150 registers using the capitalization used in the description.
43153 * AArch64 Features::
43157 * MicroBlaze Features::
43161 * Nios II Features::
43162 * OpenRISC 1000 Features::
43163 * PowerPC Features::
43164 * RISC-V Features::
43165 * S/390 and System z Features::
43171 @node AArch64 Features
43172 @subsection AArch64 Features
43173 @cindex target descriptions, AArch64 features
43175 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
43176 targets. It should contain registers @samp{x0} through @samp{x30},
43177 @samp{sp}, @samp{pc}, and @samp{cpsr}.
43179 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
43180 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
43183 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
43184 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
43185 through @samp{p15}, @samp{ffr} and @samp{vg}.
43187 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
43188 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
43191 @subsection ARC Features
43192 @cindex target descriptions, ARC Features
43194 ARC processors are highly configurable, so even core registers and their number
43195 are not completely predetermined. In addition flags and PC registers which are
43196 important to @value{GDBN} are not ``core'' registers in ARC. It is required
43197 that one of the core registers features is present.
43198 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
43200 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
43201 targets with a normal register file. It should contain registers @samp{r0}
43202 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
43203 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
43204 and any of extension core registers @samp{r32} through @samp{r59/acch}.
43205 @samp{ilink} and extension core registers are not available to read/write, when
43206 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
43208 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
43209 ARC HS targets with a reduced register file. It should contain registers
43210 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
43211 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
43212 This feature may contain register @samp{ilink} and any of extension core
43213 registers @samp{r32} through @samp{r59/acch}.
43215 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
43216 targets with a normal register file. It should contain registers @samp{r0}
43217 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
43218 @samp{lp_count} and @samp{pcl}. This feature may contain registers
43219 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
43220 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
43221 registers are not available when debugging GNU/Linux applications. The only
43222 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
43223 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
43224 ARC v2, but @samp{ilink2} is optional on ARCompact.
43226 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
43227 targets. It should contain registers @samp{pc} and @samp{status32}.
43230 @subsection ARM Features
43231 @cindex target descriptions, ARM features
43233 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
43235 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
43236 @samp{lr}, @samp{pc}, and @samp{cpsr}.
43238 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
43239 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
43240 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
43243 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
43244 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
43246 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
43247 it should contain at least registers @samp{wR0} through @samp{wR15} and
43248 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
43249 @samp{wCSSF}, and @samp{wCASF} registers are optional.
43251 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
43252 should contain at least registers @samp{d0} through @samp{d15}. If
43253 they are present, @samp{d16} through @samp{d31} should also be included.
43254 @value{GDBN} will synthesize the single-precision registers from
43255 halves of the double-precision registers.
43257 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
43258 need to contain registers; it instructs @value{GDBN} to display the
43259 VFP double-precision registers as vectors and to synthesize the
43260 quad-precision registers from pairs of double-precision registers.
43261 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
43262 be present and include 32 double-precision registers.
43264 @node i386 Features
43265 @subsection i386 Features
43266 @cindex target descriptions, i386 features
43268 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
43269 targets. It should describe the following registers:
43273 @samp{eax} through @samp{edi} plus @samp{eip} for i386
43275 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
43277 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
43278 @samp{fs}, @samp{gs}
43280 @samp{st0} through @samp{st7}
43282 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
43283 @samp{foseg}, @samp{fooff} and @samp{fop}
43286 The register sets may be different, depending on the target.
43288 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
43289 describe registers:
43293 @samp{xmm0} through @samp{xmm7} for i386
43295 @samp{xmm0} through @samp{xmm15} for amd64
43300 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
43301 @samp{org.gnu.gdb.i386.sse} feature. It should
43302 describe the upper 128 bits of @sc{ymm} registers:
43306 @samp{ymm0h} through @samp{ymm7h} for i386
43308 @samp{ymm0h} through @samp{ymm15h} for amd64
43311 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
43312 Memory Protection Extension (MPX). It should describe the following registers:
43316 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
43318 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
43321 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
43322 describe a single register, @samp{orig_eax}.
43324 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
43325 describe two system registers: @samp{fs_base} and @samp{gs_base}.
43327 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
43328 @samp{org.gnu.gdb.i386.avx} feature. It should
43329 describe additional @sc{xmm} registers:
43333 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
43336 It should describe the upper 128 bits of additional @sc{ymm} registers:
43340 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
43344 describe the upper 256 bits of @sc{zmm} registers:
43348 @samp{zmm0h} through @samp{zmm7h} for i386.
43350 @samp{zmm0h} through @samp{zmm15h} for amd64.
43354 describe the additional @sc{zmm} registers:
43358 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
43361 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
43362 describe a single register, @samp{pkru}. It is a 32-bit register
43363 valid for i386 and amd64.
43365 @node MicroBlaze Features
43366 @subsection MicroBlaze Features
43367 @cindex target descriptions, MicroBlaze features
43369 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
43370 targets. It should contain registers @samp{r0} through @samp{r31},
43371 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
43372 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
43373 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
43375 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
43376 If present, it should contain registers @samp{rshr} and @samp{rslr}
43378 @node MIPS Features
43379 @subsection @acronym{MIPS} Features
43380 @cindex target descriptions, @acronym{MIPS} features
43382 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
43383 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
43384 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
43387 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
43388 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
43389 registers. They may be 32-bit or 64-bit depending on the target.
43391 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
43392 it may be optional in a future version of @value{GDBN}. It should
43393 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
43394 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
43396 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
43397 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
43398 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
43399 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
43401 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
43402 contain a single register, @samp{restart}, which is used by the
43403 Linux kernel to control restartable syscalls.
43405 @node M68K Features
43406 @subsection M68K Features
43407 @cindex target descriptions, M68K features
43410 @item @samp{org.gnu.gdb.m68k.core}
43411 @itemx @samp{org.gnu.gdb.coldfire.core}
43412 @itemx @samp{org.gnu.gdb.fido.core}
43413 One of those features must be always present.
43414 The feature that is present determines which flavor of m68k is
43415 used. The feature that is present should contain registers
43416 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
43417 @samp{sp}, @samp{ps} and @samp{pc}.
43419 @item @samp{org.gnu.gdb.coldfire.fp}
43420 This feature is optional. If present, it should contain registers
43421 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
43425 @node NDS32 Features
43426 @subsection NDS32 Features
43427 @cindex target descriptions, NDS32 features
43429 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
43430 targets. It should contain at least registers @samp{r0} through
43431 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
43434 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
43435 it should contain 64-bit double-precision floating-point registers
43436 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
43437 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
43439 @emph{Note:} The first sixteen 64-bit double-precision floating-point
43440 registers are overlapped with the thirty-two 32-bit single-precision
43441 floating-point registers. The 32-bit single-precision registers, if
43442 not being listed explicitly, will be synthesized from halves of the
43443 overlapping 64-bit double-precision registers. Listing 32-bit
43444 single-precision registers explicitly is deprecated, and the
43445 support to it could be totally removed some day.
43447 @node Nios II Features
43448 @subsection Nios II Features
43449 @cindex target descriptions, Nios II features
43451 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
43452 targets. It should contain the 32 core registers (@samp{zero},
43453 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
43454 @samp{pc}, and the 16 control registers (@samp{status} through
43457 @node OpenRISC 1000 Features
43458 @subsection Openrisc 1000 Features
43459 @cindex target descriptions, OpenRISC 1000 features
43461 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
43462 targets. It should contain the 32 general purpose registers (@samp{r0}
43463 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
43465 @node PowerPC Features
43466 @subsection PowerPC Features
43467 @cindex target descriptions, PowerPC features
43469 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
43470 targets. It should contain registers @samp{r0} through @samp{r31},
43471 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
43472 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
43474 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
43475 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
43477 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
43478 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
43479 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
43480 through @samp{v31} as aliases for the corresponding @samp{vrX}
43483 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
43484 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
43485 combine these registers with the floating point registers (@samp{f0}
43486 through @samp{f31}) and the altivec registers (@samp{vr0} through
43487 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
43488 @samp{vs63}, the set of vector-scalar registers for POWER7.
43489 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
43490 @samp{org.gnu.gdb.power.altivec}.
43492 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
43493 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
43494 @samp{spefscr}. SPE targets should provide 32-bit registers in
43495 @samp{org.gnu.gdb.power.core} and provide the upper halves in
43496 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
43497 these to present registers @samp{ev0} through @samp{ev31} to the
43500 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
43501 contain the 64-bit register @samp{ppr}.
43503 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
43504 contain the 64-bit register @samp{dscr}.
43506 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
43507 contain the 64-bit register @samp{tar}.
43509 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
43510 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
43513 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
43514 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
43515 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
43516 server PMU registers provided by @sc{gnu}/Linux.
43518 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
43519 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
43522 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
43523 contain the checkpointed general-purpose registers @samp{cr0} through
43524 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
43525 @samp{cctr}. These registers may all be either 32-bit or 64-bit
43526 depending on the target. It should also contain the checkpointed
43527 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
43530 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
43531 contain the checkpointed 64-bit floating-point registers @samp{cf0}
43532 through @samp{cf31}, as well as the checkpointed 64-bit register
43535 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
43536 should contain the checkpointed altivec registers @samp{cvr0} through
43537 @samp{cvr31}, all 128-bit wide. It should also contain the
43538 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
43541 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
43542 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
43543 will combine these registers with the checkpointed floating point
43544 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
43545 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
43546 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
43547 @samp{cvs63}. Therefore, this feature requires both
43548 @samp{org.gnu.gdb.power.htm.altivec} and
43549 @samp{org.gnu.gdb.power.htm.fpu}.
43551 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
43552 contain the 64-bit checkpointed register @samp{cppr}.
43554 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
43555 contain the 64-bit checkpointed register @samp{cdscr}.
43557 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
43558 contain the 64-bit checkpointed register @samp{ctar}.
43561 @node RISC-V Features
43562 @subsection RISC-V Features
43563 @cindex target descriptions, RISC-V Features
43565 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
43566 targets. It should contain the registers @samp{x0} through
43567 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
43568 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
43571 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
43572 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
43573 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
43574 architectural register names, or the ABI names can be used.
43576 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
43577 it should contain registers that are not backed by real registers on
43578 the target, but are instead virtual, where the register value is
43579 derived from other target state. In many ways these are like
43580 @value{GDBN}s pseudo-registers, except implemented by the target.
43581 Currently the only register expected in this set is the one byte
43582 @samp{priv} register that contains the target's privilege level in the
43583 least significant two bits.
43585 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
43586 should contain all of the target's standard CSRs. Standard CSRs are
43587 those defined in the RISC-V specification documents. There is some
43588 overlap between this feature and the fpu feature; the @samp{fflags},
43589 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
43590 expectation is that these registers will be in the fpu feature if the
43591 target has floating point hardware, but can be moved into the csr
43592 feature if the target has the floating point control registers, but no
43593 other floating point hardware.
43595 @node S/390 and System z Features
43596 @subsection S/390 and System z Features
43597 @cindex target descriptions, S/390 features
43598 @cindex target descriptions, System z features
43600 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
43601 System z targets. It should contain the PSW and the 16 general
43602 registers. In particular, System z targets should provide the 64-bit
43603 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
43604 S/390 targets should provide the 32-bit versions of these registers.
43605 A System z target that runs in 31-bit addressing mode should provide
43606 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
43607 register's upper halves @samp{r0h} through @samp{r15h}, and their
43608 lower halves @samp{r0l} through @samp{r15l}.
43610 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
43611 contain the 64-bit registers @samp{f0} through @samp{f15}, and
43614 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
43615 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
43617 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
43618 contain the register @samp{orig_r2}, which is 64-bit wide on System z
43619 targets and 32-bit otherwise. In addition, the feature may contain
43620 the @samp{last_break} register, whose width depends on the addressing
43621 mode, as well as the @samp{system_call} register, which is always
43624 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
43625 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
43626 @samp{atia}, and @samp{tr0} through @samp{tr15}.
43628 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
43629 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
43630 combined by @value{GDBN} with the floating point registers @samp{f0}
43631 through @samp{f15} to present the 128-bit wide vector registers
43632 @samp{v0} through @samp{v15}. In addition, this feature should
43633 contain the 128-bit wide vector registers @samp{v16} through
43636 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
43637 the 64-bit wide guarded-storage-control registers @samp{gsd},
43638 @samp{gssm}, and @samp{gsepla}.
43640 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
43641 the 64-bit wide guarded-storage broadcast control registers
43642 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
43644 @node Sparc Features
43645 @subsection Sparc Features
43646 @cindex target descriptions, sparc32 features
43647 @cindex target descriptions, sparc64 features
43648 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
43649 targets. It should describe the following registers:
43653 @samp{g0} through @samp{g7}
43655 @samp{o0} through @samp{o7}
43657 @samp{l0} through @samp{l7}
43659 @samp{i0} through @samp{i7}
43662 They may be 32-bit or 64-bit depending on the target.
43664 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
43665 targets. It should describe the following registers:
43669 @samp{f0} through @samp{f31}
43671 @samp{f32} through @samp{f62} for sparc64
43674 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
43675 targets. It should describe the following registers:
43679 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
43680 @samp{fsr}, and @samp{csr} for sparc32
43682 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
43686 @node TIC6x Features
43687 @subsection TMS320C6x Features
43688 @cindex target descriptions, TIC6x features
43689 @cindex target descriptions, TMS320C6x features
43690 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
43691 targets. It should contain registers @samp{A0} through @samp{A15},
43692 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
43694 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
43695 contain registers @samp{A16} through @samp{A31} and @samp{B16}
43696 through @samp{B31}.
43698 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
43699 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
43701 @node Operating System Information
43702 @appendix Operating System Information
43703 @cindex operating system information
43709 Users of @value{GDBN} often wish to obtain information about the state of
43710 the operating system running on the target---for example the list of
43711 processes, or the list of open files. This section describes the
43712 mechanism that makes it possible. This mechanism is similar to the
43713 target features mechanism (@pxref{Target Descriptions}), but focuses
43714 on a different aspect of target.
43716 Operating system information is retrived from the target via the
43717 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
43718 read}). The object name in the request should be @samp{osdata}, and
43719 the @var{annex} identifies the data to be fetched.
43722 @appendixsection Process list
43723 @cindex operating system information, process list
43725 When requesting the process list, the @var{annex} field in the
43726 @samp{qXfer} request should be @samp{processes}. The returned data is
43727 an XML document. The formal syntax of this document is defined in
43728 @file{gdb/features/osdata.dtd}.
43730 An example document is:
43733 <?xml version="1.0"?>
43734 <!DOCTYPE target SYSTEM "osdata.dtd">
43735 <osdata type="processes">
43737 <column name="pid">1</column>
43738 <column name="user">root</column>
43739 <column name="command">/sbin/init</column>
43740 <column name="cores">1,2,3</column>
43745 Each item should include a column whose name is @samp{pid}. The value
43746 of that column should identify the process on the target. The
43747 @samp{user} and @samp{command} columns are optional, and will be
43748 displayed by @value{GDBN}. The @samp{cores} column, if present,
43749 should contain a comma-separated list of cores that this process
43750 is running on. Target may provide additional columns,
43751 which @value{GDBN} currently ignores.
43753 @node Trace File Format
43754 @appendix Trace File Format
43755 @cindex trace file format
43757 The trace file comes in three parts: a header, a textual description
43758 section, and a trace frame section with binary data.
43760 The header has the form @code{\x7fTRACE0\n}. The first byte is
43761 @code{0x7f} so as to indicate that the file contains binary data,
43762 while the @code{0} is a version number that may have different values
43765 The description section consists of multiple lines of @sc{ascii} text
43766 separated by newline characters (@code{0xa}). The lines may include a
43767 variety of optional descriptive or context-setting information, such
43768 as tracepoint definitions or register set size. @value{GDBN} will
43769 ignore any line that it does not recognize. An empty line marks the end
43774 Specifies the size of a register block in bytes. This is equal to the
43775 size of a @code{g} packet payload in the remote protocol. @var{size}
43776 is an ascii decimal number. There should be only one such line in
43777 a single trace file.
43779 @item status @var{status}
43780 Trace status. @var{status} has the same format as a @code{qTStatus}
43781 remote packet reply. There should be only one such line in a single trace
43784 @item tp @var{payload}
43785 Tracepoint definition. The @var{payload} has the same format as
43786 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
43787 may take multiple lines of definition, corresponding to the multiple
43790 @item tsv @var{payload}
43791 Trace state variable definition. The @var{payload} has the same format as
43792 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
43793 may take multiple lines of definition, corresponding to the multiple
43796 @item tdesc @var{payload}
43797 Target description in XML format. The @var{payload} is a single line of
43798 the XML file. All such lines should be concatenated together to get
43799 the original XML file. This file is in the same format as @code{qXfer}
43800 @code{features} payload, and corresponds to the main @code{target.xml}
43801 file. Includes are not allowed.
43805 The trace frame section consists of a number of consecutive frames.
43806 Each frame begins with a two-byte tracepoint number, followed by a
43807 four-byte size giving the amount of data in the frame. The data in
43808 the frame consists of a number of blocks, each introduced by a
43809 character indicating its type (at least register, memory, and trace
43810 state variable). The data in this section is raw binary, not a
43811 hexadecimal or other encoding; its endianness matches the target's
43814 @c FIXME bi-arch may require endianness/arch info in description section
43817 @item R @var{bytes}
43818 Register block. The number and ordering of bytes matches that of a
43819 @code{g} packet in the remote protocol. Note that these are the
43820 actual bytes, in target order, not a hexadecimal encoding.
43822 @item M @var{address} @var{length} @var{bytes}...
43823 Memory block. This is a contiguous block of memory, at the 8-byte
43824 address @var{address}, with a 2-byte length @var{length}, followed by
43825 @var{length} bytes.
43827 @item V @var{number} @var{value}
43828 Trace state variable block. This records the 8-byte signed value
43829 @var{value} of trace state variable numbered @var{number}.
43833 Future enhancements of the trace file format may include additional types
43836 @node Index Section Format
43837 @appendix @code{.gdb_index} section format
43838 @cindex .gdb_index section format
43839 @cindex index section format
43841 This section documents the index section that is created by @code{save
43842 gdb-index} (@pxref{Index Files}). The index section is
43843 DWARF-specific; some knowledge of DWARF is assumed in this
43846 The mapped index file format is designed to be directly
43847 @code{mmap}able on any architecture. In most cases, a datum is
43848 represented using a little-endian 32-bit integer value, called an
43849 @code{offset_type}. Big endian machines must byte-swap the values
43850 before using them. Exceptions to this rule are noted. The data is
43851 laid out such that alignment is always respected.
43853 A mapped index consists of several areas, laid out in order.
43857 The file header. This is a sequence of values, of @code{offset_type}
43858 unless otherwise noted:
43862 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43863 Version 4 uses a different hashing function from versions 5 and 6.
43864 Version 6 includes symbols for inlined functions, whereas versions 4
43865 and 5 do not. Version 7 adds attributes to the CU indices in the
43866 symbol table. Version 8 specifies that symbols from DWARF type units
43867 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43868 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43870 @value{GDBN} will only read version 4, 5, or 6 indices
43871 by specifying @code{set use-deprecated-index-sections on}.
43872 GDB has a workaround for potentially broken version 7 indices so it is
43873 currently not flagged as deprecated.
43876 The offset, from the start of the file, of the CU list.
43879 The offset, from the start of the file, of the types CU list. Note
43880 that this area can be empty, in which case this offset will be equal
43881 to the next offset.
43884 The offset, from the start of the file, of the address area.
43887 The offset, from the start of the file, of the symbol table.
43890 The offset, from the start of the file, of the constant pool.
43894 The CU list. This is a sequence of pairs of 64-bit little-endian
43895 values, sorted by the CU offset. The first element in each pair is
43896 the offset of a CU in the @code{.debug_info} section. The second
43897 element in each pair is the length of that CU. References to a CU
43898 elsewhere in the map are done using a CU index, which is just the
43899 0-based index into this table. Note that if there are type CUs, then
43900 conceptually CUs and type CUs form a single list for the purposes of
43904 The types CU list. This is a sequence of triplets of 64-bit
43905 little-endian values. In a triplet, the first value is the CU offset,
43906 the second value is the type offset in the CU, and the third value is
43907 the type signature. The types CU list is not sorted.
43910 The address area. The address area consists of a sequence of address
43911 entries. Each address entry has three elements:
43915 The low address. This is a 64-bit little-endian value.
43918 The high address. This is a 64-bit little-endian value. Like
43919 @code{DW_AT_high_pc}, the value is one byte beyond the end.
43922 The CU index. This is an @code{offset_type} value.
43926 The symbol table. This is an open-addressed hash table. The size of
43927 the hash table is always a power of 2.
43929 Each slot in the hash table consists of a pair of @code{offset_type}
43930 values. The first value is the offset of the symbol's name in the
43931 constant pool. The second value is the offset of the CU vector in the
43934 If both values are 0, then this slot in the hash table is empty. This
43935 is ok because while 0 is a valid constant pool index, it cannot be a
43936 valid index for both a string and a CU vector.
43938 The hash value for a table entry is computed by applying an
43939 iterative hash function to the symbol's name. Starting with an
43940 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
43941 the string is incorporated into the hash using the formula depending on the
43946 The formula is @code{r = r * 67 + c - 113}.
43948 @item Versions 5 to 7
43949 The formula is @code{r = r * 67 + tolower (c) - 113}.
43952 The terminating @samp{\0} is not incorporated into the hash.
43954 The step size used in the hash table is computed via
43955 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43956 value, and @samp{size} is the size of the hash table. The step size
43957 is used to find the next candidate slot when handling a hash
43960 The names of C@t{++} symbols in the hash table are canonicalized. We
43961 don't currently have a simple description of the canonicalization
43962 algorithm; if you intend to create new index sections, you must read
43966 The constant pool. This is simply a bunch of bytes. It is organized
43967 so that alignment is correct: CU vectors are stored first, followed by
43970 A CU vector in the constant pool is a sequence of @code{offset_type}
43971 values. The first value is the number of CU indices in the vector.
43972 Each subsequent value is the index and symbol attributes of a CU in
43973 the CU list. This element in the hash table is used to indicate which
43974 CUs define the symbol and how the symbol is used.
43975 See below for the format of each CU index+attributes entry.
43977 A string in the constant pool is zero-terminated.
43980 Attributes were added to CU index values in @code{.gdb_index} version 7.
43981 If a symbol has multiple uses within a CU then there is one
43982 CU index+attributes value for each use.
43984 The format of each CU index+attributes entry is as follows
43990 This is the index of the CU in the CU list.
43992 These bits are reserved for future purposes and must be zero.
43994 The kind of the symbol in the CU.
43998 This value is reserved and should not be used.
43999 By reserving zero the full @code{offset_type} value is backwards compatible
44000 with previous versions of the index.
44002 The symbol is a type.
44004 The symbol is a variable or an enum value.
44006 The symbol is a function.
44008 Any other kind of symbol.
44010 These values are reserved.
44014 This bit is zero if the value is global and one if it is static.
44016 The determination of whether a symbol is global or static is complicated.
44017 The authorative reference is the file @file{dwarf2read.c} in
44018 @value{GDBN} sources.
44022 This pseudo-code describes the computation of a symbol's kind and
44023 global/static attributes in the index.
44026 is_external = get_attribute (die, DW_AT_external);
44027 language = get_attribute (cu_die, DW_AT_language);
44030 case DW_TAG_typedef:
44031 case DW_TAG_base_type:
44032 case DW_TAG_subrange_type:
44036 case DW_TAG_enumerator:
44038 is_static = language != CPLUS;
44040 case DW_TAG_subprogram:
44042 is_static = ! (is_external || language == ADA);
44044 case DW_TAG_constant:
44046 is_static = ! is_external;
44048 case DW_TAG_variable:
44050 is_static = ! is_external;
44052 case DW_TAG_namespace:
44056 case DW_TAG_class_type:
44057 case DW_TAG_interface_type:
44058 case DW_TAG_structure_type:
44059 case DW_TAG_union_type:
44060 case DW_TAG_enumeration_type:
44062 is_static = language != CPLUS;
44070 @appendix Manual pages
44074 * gdb man:: The GNU Debugger man page
44075 * gdbserver man:: Remote Server for the GNU Debugger man page
44076 * gcore man:: Generate a core file of a running program
44077 * gdbinit man:: gdbinit scripts
44078 * gdb-add-index man:: Add index files to speed up GDB
44084 @c man title gdb The GNU Debugger
44086 @c man begin SYNOPSIS gdb
44087 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
44088 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
44089 [@option{-b}@w{ }@var{bps}]
44090 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
44091 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
44092 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
44093 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
44094 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
44097 @c man begin DESCRIPTION gdb
44098 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
44099 going on ``inside'' another program while it executes -- or what another
44100 program was doing at the moment it crashed.
44102 @value{GDBN} can do four main kinds of things (plus other things in support of
44103 these) to help you catch bugs in the act:
44107 Start your program, specifying anything that might affect its behavior.
44110 Make your program stop on specified conditions.
44113 Examine what has happened, when your program has stopped.
44116 Change things in your program, so you can experiment with correcting the
44117 effects of one bug and go on to learn about another.
44120 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
44123 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
44124 commands from the terminal until you tell it to exit with the @value{GDBN}
44125 command @code{quit}. You can get online help from @value{GDBN} itself
44126 by using the command @code{help}.
44128 You can run @code{gdb} with no arguments or options; but the most
44129 usual way to start @value{GDBN} is with one argument or two, specifying an
44130 executable program as the argument:
44136 You can also start with both an executable program and a core file specified:
44142 You can, instead, specify a process ID as a second argument, if you want
44143 to debug a running process:
44151 would attach @value{GDBN} to process @code{1234} (unless you also have a file
44152 named @file{1234}; @value{GDBN} does check for a core file first).
44153 With option @option{-p} you can omit the @var{program} filename.
44155 Here are some of the most frequently needed @value{GDBN} commands:
44157 @c pod2man highlights the right hand side of the @item lines.
44159 @item break [@var{file}:]@var{function}
44160 Set a breakpoint at @var{function} (in @var{file}).
44162 @item run [@var{arglist}]
44163 Start your program (with @var{arglist}, if specified).
44166 Backtrace: display the program stack.
44168 @item print @var{expr}
44169 Display the value of an expression.
44172 Continue running your program (after stopping, e.g. at a breakpoint).
44175 Execute next program line (after stopping); step @emph{over} any
44176 function calls in the line.
44178 @item edit [@var{file}:]@var{function}
44179 look at the program line where it is presently stopped.
44181 @item list [@var{file}:]@var{function}
44182 type the text of the program in the vicinity of where it is presently stopped.
44185 Execute next program line (after stopping); step @emph{into} any
44186 function calls in the line.
44188 @item help [@var{name}]
44189 Show information about @value{GDBN} command @var{name}, or general information
44190 about using @value{GDBN}.
44193 Exit from @value{GDBN}.
44197 For full details on @value{GDBN},
44198 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44199 by Richard M. Stallman and Roland H. Pesch. The same text is available online
44200 as the @code{gdb} entry in the @code{info} program.
44204 @c man begin OPTIONS gdb
44205 Any arguments other than options specify an executable
44206 file and core file (or process ID); that is, the first argument
44207 encountered with no
44208 associated option flag is equivalent to a @option{-se} option, and the second,
44209 if any, is equivalent to a @option{-c} option if it's the name of a file.
44211 both long and short forms; both are shown here. The long forms are also
44212 recognized if you truncate them, so long as enough of the option is
44213 present to be unambiguous. (If you prefer, you can flag option
44214 arguments with @option{+} rather than @option{-}, though we illustrate the
44215 more usual convention.)
44217 All the options and command line arguments you give are processed
44218 in sequential order. The order makes a difference when the @option{-x}
44224 List all options, with brief explanations.
44226 @item -symbols=@var{file}
44227 @itemx -s @var{file}
44228 Read symbol table from file @var{file}.
44231 Enable writing into executable and core files.
44233 @item -exec=@var{file}
44234 @itemx -e @var{file}
44235 Use file @var{file} as the executable file to execute when
44236 appropriate, and for examining pure data in conjunction with a core
44239 @item -se=@var{file}
44240 Read symbol table from file @var{file} and use it as the executable
44243 @item -core=@var{file}
44244 @itemx -c @var{file}
44245 Use file @var{file} as a core dump to examine.
44247 @item -command=@var{file}
44248 @itemx -x @var{file}
44249 Execute @value{GDBN} commands from file @var{file}.
44251 @item -ex @var{command}
44252 Execute given @value{GDBN} @var{command}.
44254 @item -directory=@var{directory}
44255 @itemx -d @var{directory}
44256 Add @var{directory} to the path to search for source files.
44259 Do not execute commands from @file{~/.gdbinit}.
44263 Do not execute commands from any @file{.gdbinit} initialization files.
44267 ``Quiet''. Do not print the introductory and copyright messages. These
44268 messages are also suppressed in batch mode.
44271 Run in batch mode. Exit with status @code{0} after processing all the command
44272 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
44273 Exit with nonzero status if an error occurs in executing the @value{GDBN}
44274 commands in the command files.
44276 Batch mode may be useful for running @value{GDBN} as a filter, for example to
44277 download and run a program on another computer; in order to make this
44278 more useful, the message
44281 Program exited normally.
44285 (which is ordinarily issued whenever a program running under @value{GDBN} control
44286 terminates) is not issued when running in batch mode.
44288 @item -cd=@var{directory}
44289 Run @value{GDBN} using @var{directory} as its working directory,
44290 instead of the current directory.
44294 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
44295 @value{GDBN} to output the full file name and line number in a standard,
44296 recognizable fashion each time a stack frame is displayed (which
44297 includes each time the program stops). This recognizable format looks
44298 like two @samp{\032} characters, followed by the file name, line number
44299 and character position separated by colons, and a newline. The
44300 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
44301 characters as a signal to display the source code for the frame.
44304 Set the line speed (baud rate or bits per second) of any serial
44305 interface used by @value{GDBN} for remote debugging.
44307 @item -tty=@var{device}
44308 Run using @var{device} for your program's standard input and output.
44312 @c man begin SEEALSO gdb
44314 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44315 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44316 documentation are properly installed at your site, the command
44323 should give you access to the complete manual.
44325 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44326 Richard M. Stallman and Roland H. Pesch, July 1991.
44330 @node gdbserver man
44331 @heading gdbserver man
44333 @c man title gdbserver Remote Server for the GNU Debugger
44335 @c man begin SYNOPSIS gdbserver
44336 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44338 gdbserver --attach @var{comm} @var{pid}
44340 gdbserver --multi @var{comm}
44344 @c man begin DESCRIPTION gdbserver
44345 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
44346 than the one which is running the program being debugged.
44349 @subheading Usage (server (target) side)
44352 Usage (server (target) side):
44355 First, you need to have a copy of the program you want to debug put onto
44356 the target system. The program can be stripped to save space if needed, as
44357 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
44358 the @value{GDBN} running on the host system.
44360 To use the server, you log on to the target system, and run the @command{gdbserver}
44361 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
44362 your program, and (c) its arguments. The general syntax is:
44365 target> gdbserver @var{comm} @var{program} [@var{args} ...]
44368 For example, using a serial port, you might say:
44372 @c @file would wrap it as F</dev/com1>.
44373 target> gdbserver /dev/com1 emacs foo.txt
44376 target> gdbserver @file{/dev/com1} emacs foo.txt
44380 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
44381 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
44382 waits patiently for the host @value{GDBN} to communicate with it.
44384 To use a TCP connection, you could say:
44387 target> gdbserver host:2345 emacs foo.txt
44390 This says pretty much the same thing as the last example, except that we are
44391 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
44392 that we are expecting to see a TCP connection from @code{host} to local TCP port
44393 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
44394 want for the port number as long as it does not conflict with any existing TCP
44395 ports on the target system. This same port number must be used in the host
44396 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
44397 you chose a port number that conflicts with another service, @command{gdbserver} will
44398 print an error message and exit.
44400 @command{gdbserver} can also attach to running programs.
44401 This is accomplished via the @option{--attach} argument. The syntax is:
44404 target> gdbserver --attach @var{comm} @var{pid}
44407 @var{pid} is the process ID of a currently running process. It isn't
44408 necessary to point @command{gdbserver} at a binary for the running process.
44410 To start @code{gdbserver} without supplying an initial command to run
44411 or process ID to attach, use the @option{--multi} command line option.
44412 In such case you should connect using @kbd{target extended-remote} to start
44413 the program you want to debug.
44416 target> gdbserver --multi @var{comm}
44420 @subheading Usage (host side)
44426 You need an unstripped copy of the target program on your host system, since
44427 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
44428 would, with the target program as the first argument. (You may need to use the
44429 @option{--baud} option if the serial line is running at anything except 9600 baud.)
44430 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
44431 new command you need to know about is @code{target remote}
44432 (or @code{target extended-remote}). Its argument is either
44433 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
44434 descriptor. For example:
44438 @c @file would wrap it as F</dev/ttyb>.
44439 (gdb) target remote /dev/ttyb
44442 (gdb) target remote @file{/dev/ttyb}
44447 communicates with the server via serial line @file{/dev/ttyb}, and:
44450 (gdb) target remote the-target:2345
44454 communicates via a TCP connection to port 2345 on host `the-target', where
44455 you previously started up @command{gdbserver} with the same port number. Note that for
44456 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
44457 command, otherwise you may get an error that looks something like
44458 `Connection refused'.
44460 @command{gdbserver} can also debug multiple inferiors at once,
44463 the @value{GDBN} manual in node @code{Inferiors and Programs}
44464 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
44467 @ref{Inferiors and Programs}.
44469 In such case use the @code{extended-remote} @value{GDBN} command variant:
44472 (gdb) target extended-remote the-target:2345
44475 The @command{gdbserver} option @option{--multi} may or may not be used in such
44479 @c man begin OPTIONS gdbserver
44480 There are three different modes for invoking @command{gdbserver}:
44485 Debug a specific program specified by its program name:
44488 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44491 The @var{comm} parameter specifies how should the server communicate
44492 with @value{GDBN}; it is either a device name (to use a serial line),
44493 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
44494 stdin/stdout of @code{gdbserver}. Specify the name of the program to
44495 debug in @var{prog}. Any remaining arguments will be passed to the
44496 program verbatim. When the program exits, @value{GDBN} will close the
44497 connection, and @code{gdbserver} will exit.
44500 Debug a specific program by specifying the process ID of a running
44504 gdbserver --attach @var{comm} @var{pid}
44507 The @var{comm} parameter is as described above. Supply the process ID
44508 of a running program in @var{pid}; @value{GDBN} will do everything
44509 else. Like with the previous mode, when the process @var{pid} exits,
44510 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
44513 Multi-process mode -- debug more than one program/process:
44516 gdbserver --multi @var{comm}
44519 In this mode, @value{GDBN} can instruct @command{gdbserver} which
44520 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
44521 close the connection when a process being debugged exits, so you can
44522 debug several processes in the same session.
44525 In each of the modes you may specify these options:
44530 List all options, with brief explanations.
44533 This option causes @command{gdbserver} to print its version number and exit.
44536 @command{gdbserver} will attach to a running program. The syntax is:
44539 target> gdbserver --attach @var{comm} @var{pid}
44542 @var{pid} is the process ID of a currently running process. It isn't
44543 necessary to point @command{gdbserver} at a binary for the running process.
44546 To start @code{gdbserver} without supplying an initial command to run
44547 or process ID to attach, use this command line option.
44548 Then you can connect using @kbd{target extended-remote} and start
44549 the program you want to debug. The syntax is:
44552 target> gdbserver --multi @var{comm}
44556 Instruct @code{gdbserver} to display extra status information about the debugging
44558 This option is intended for @code{gdbserver} development and for bug reports to
44561 @item --remote-debug
44562 Instruct @code{gdbserver} to display remote protocol debug output.
44563 This option is intended for @code{gdbserver} development and for bug reports to
44566 @item --debug-format=option1@r{[},option2,...@r{]}
44567 Instruct @code{gdbserver} to include extra information in each line
44568 of debugging output.
44569 @xref{Other Command-Line Arguments for gdbserver}.
44572 Specify a wrapper to launch programs
44573 for debugging. The option should be followed by the name of the
44574 wrapper, then any command-line arguments to pass to the wrapper, then
44575 @kbd{--} indicating the end of the wrapper arguments.
44578 By default, @command{gdbserver} keeps the listening TCP port open, so that
44579 additional connections are possible. However, if you start @code{gdbserver}
44580 with the @option{--once} option, it will stop listening for any further
44581 connection attempts after connecting to the first @value{GDBN} session.
44583 @c --disable-packet is not documented for users.
44585 @c --disable-randomization and --no-disable-randomization are superseded by
44586 @c QDisableRandomization.
44591 @c man begin SEEALSO gdbserver
44593 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44594 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44595 documentation are properly installed at your site, the command
44601 should give you access to the complete manual.
44603 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44604 Richard M. Stallman and Roland H. Pesch, July 1991.
44611 @c man title gcore Generate a core file of a running program
44614 @c man begin SYNOPSIS gcore
44615 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
44619 @c man begin DESCRIPTION gcore
44620 Generate core dumps of one or more running programs with process IDs
44621 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
44622 is equivalent to one produced by the kernel when the process crashes
44623 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
44624 limit). However, unlike after a crash, after @command{gcore} finishes
44625 its job the program remains running without any change.
44628 @c man begin OPTIONS gcore
44631 Dump all memory mappings. The actual effect of this option depends on
44632 the Operating System. On @sc{gnu}/Linux, it will disable
44633 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
44634 enable @code{dump-excluded-mappings} (@pxref{set
44635 dump-excluded-mappings}).
44637 @item -o @var{prefix}
44638 The optional argument @var{prefix} specifies the prefix to be used
44639 when composing the file names of the core dumps. The file name is
44640 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
44641 process ID of the running program being analyzed by @command{gcore}.
44642 If not specified, @var{prefix} defaults to @var{gcore}.
44646 @c man begin SEEALSO gcore
44648 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44649 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44650 documentation are properly installed at your site, the command
44657 should give you access to the complete manual.
44659 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44660 Richard M. Stallman and Roland H. Pesch, July 1991.
44667 @c man title gdbinit GDB initialization scripts
44670 @c man begin SYNOPSIS gdbinit
44671 @ifset SYSTEM_GDBINIT
44672 @value{SYSTEM_GDBINIT}
44681 @c man begin DESCRIPTION gdbinit
44682 These files contain @value{GDBN} commands to automatically execute during
44683 @value{GDBN} startup. The lines of contents are canned sequences of commands,
44686 the @value{GDBN} manual in node @code{Sequences}
44687 -- shell command @code{info -f gdb -n Sequences}.
44693 Please read more in
44695 the @value{GDBN} manual in node @code{Startup}
44696 -- shell command @code{info -f gdb -n Startup}.
44703 @ifset SYSTEM_GDBINIT
44704 @item @value{SYSTEM_GDBINIT}
44706 @ifclear SYSTEM_GDBINIT
44707 @item (not enabled with @code{--with-system-gdbinit} during compilation)
44709 System-wide initialization file. It is executed unless user specified
44710 @value{GDBN} option @code{-nx} or @code{-n}.
44713 the @value{GDBN} manual in node @code{System-wide configuration}
44714 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
44717 @ref{System-wide configuration}.
44721 User initialization file. It is executed unless user specified
44722 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
44725 Initialization file for current directory. It may need to be enabled with
44726 @value{GDBN} security command @code{set auto-load local-gdbinit}.
44729 the @value{GDBN} manual in node @code{Init File in the Current Directory}
44730 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
44733 @ref{Init File in the Current Directory}.
44738 @c man begin SEEALSO gdbinit
44740 gdb(1), @code{info -f gdb -n Startup}
44742 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44743 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44744 documentation are properly installed at your site, the command
44750 should give you access to the complete manual.
44752 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44753 Richard M. Stallman and Roland H. Pesch, July 1991.
44757 @node gdb-add-index man
44758 @heading gdb-add-index
44759 @pindex gdb-add-index
44760 @anchor{gdb-add-index}
44762 @c man title gdb-add-index Add index files to speed up GDB
44764 @c man begin SYNOPSIS gdb-add-index
44765 gdb-add-index @var{filename}
44768 @c man begin DESCRIPTION gdb-add-index
44769 When @value{GDBN} finds a symbol file, it scans the symbols in the
44770 file in order to construct an internal symbol table. This lets most
44771 @value{GDBN} operations work quickly--at the cost of a delay early on.
44772 For large programs, this delay can be quite lengthy, so @value{GDBN}
44773 provides a way to build an index, which speeds up startup.
44775 To determine whether a file contains such an index, use the command
44776 @kbd{readelf -S filename}: the index is stored in a section named
44777 @code{.gdb_index}. The index file can only be produced on systems
44778 which use ELF binaries and DWARF debug information (i.e., sections
44779 named @code{.debug_*}).
44781 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
44782 in the @env{PATH} environment variable. If you want to use different
44783 versions of these programs, you can specify them through the
44784 @env{GDB} and @env{OBJDUMP} environment variables.
44788 the @value{GDBN} manual in node @code{Index Files}
44789 -- shell command @kbd{info -f gdb -n "Index Files"}.
44796 @c man begin SEEALSO gdb-add-index
44798 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44799 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44800 documentation are properly installed at your site, the command
44806 should give you access to the complete manual.
44808 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44809 Richard M. Stallman and Roland H. Pesch, July 1991.
44815 @node GNU Free Documentation License
44816 @appendix GNU Free Documentation License
44819 @node Concept Index
44820 @unnumbered Concept Index
44824 @node Command and Variable Index
44825 @unnumbered Command, Variable, and Function Index
44830 % I think something like @@colophon should be in texinfo. In the
44832 \long\def\colophon{\hbox to0pt{}\vfill
44833 \centerline{The body of this manual is set in}
44834 \centerline{\fontname\tenrm,}
44835 \centerline{with headings in {\bf\fontname\tenbf}}
44836 \centerline{and examples in {\tt\fontname\tentt}.}
44837 \centerline{{\it\fontname\tenit\/},}
44838 \centerline{{\bf\fontname\tenbf}, and}
44839 \centerline{{\sl\fontname\tensl\/}}
44840 \centerline{are used for emphasis.}\vfill}
44842 % Blame: doc@@cygnus.com, 1991.