1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2017 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{} 1988-2017 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) 1988-2017 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.
550 @chapter A Sample @value{GDBN} Session
552 You can use this manual at your leisure to read all about @value{GDBN}.
553 However, a handful of commands are enough to get started using the
554 debugger. This chapter illustrates those commands.
557 In this sample session, we emphasize user input like this: @b{input},
558 to make it easier to pick out from the surrounding output.
561 @c FIXME: this example may not be appropriate for some configs, where
562 @c FIXME...primary interest is in remote use.
564 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
565 processor) exhibits the following bug: sometimes, when we change its
566 quote strings from the default, the commands used to capture one macro
567 definition within another stop working. In the following short @code{m4}
568 session, we define a macro @code{foo} which expands to @code{0000}; we
569 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
570 same thing. However, when we change the open quote string to
571 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
572 procedure fails to define a new synonym @code{baz}:
581 @b{define(bar,defn(`foo'))}
585 @b{changequote(<QUOTE>,<UNQUOTE>)}
587 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
590 m4: End of input: 0: fatal error: EOF in string
594 Let us use @value{GDBN} to try to see what is going on.
597 $ @b{@value{GDBP} m4}
598 @c FIXME: this falsifies the exact text played out, to permit smallbook
599 @c FIXME... format to come out better.
600 @value{GDBN} is free software and you are welcome to distribute copies
601 of it under certain conditions; type "show copying" to see
603 There is absolutely no warranty for @value{GDBN}; type "show warranty"
606 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
611 @value{GDBN} reads only enough symbol data to know where to find the
612 rest when needed; as a result, the first prompt comes up very quickly.
613 We now tell @value{GDBN} to use a narrower display width than usual, so
614 that examples fit in this manual.
617 (@value{GDBP}) @b{set width 70}
621 We need to see how the @code{m4} built-in @code{changequote} works.
622 Having looked at the source, we know the relevant subroutine is
623 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
624 @code{break} command.
627 (@value{GDBP}) @b{break m4_changequote}
628 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
632 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
633 control; as long as control does not reach the @code{m4_changequote}
634 subroutine, the program runs as usual:
637 (@value{GDBP}) @b{run}
638 Starting program: /work/Editorial/gdb/gnu/m4/m4
646 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
647 suspends execution of @code{m4}, displaying information about the
648 context where it stops.
651 @b{changequote(<QUOTE>,<UNQUOTE>)}
653 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
655 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
659 Now we use the command @code{n} (@code{next}) to advance execution to
660 the next line of the current function.
664 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
669 @code{set_quotes} looks like a promising subroutine. We can go into it
670 by using the command @code{s} (@code{step}) instead of @code{next}.
671 @code{step} goes to the next line to be executed in @emph{any}
672 subroutine, so it steps into @code{set_quotes}.
676 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
678 530 if (lquote != def_lquote)
682 The display that shows the subroutine where @code{m4} is now
683 suspended (and its arguments) is called a stack frame display. It
684 shows a summary of the stack. We can use the @code{backtrace}
685 command (which can also be spelled @code{bt}), to see where we are
686 in the stack as a whole: the @code{backtrace} command displays a
687 stack frame for each active subroutine.
690 (@value{GDBP}) @b{bt}
691 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
693 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
695 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
696 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
698 #4 0x79dc in expand_input () at macro.c:40
699 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
703 We step through a few more lines to see what happens. The first two
704 times, we can use @samp{s}; the next two times we use @code{n} to avoid
705 falling into the @code{xstrdup} subroutine.
709 0x3b5c 532 if (rquote != def_rquote)
711 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
712 def_lquote : xstrdup(lq);
714 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
717 538 len_lquote = strlen(rquote);
721 The last line displayed looks a little odd; we can examine the variables
722 @code{lquote} and @code{rquote} to see if they are in fact the new left
723 and right quotes we specified. We use the command @code{p}
724 (@code{print}) to see their values.
727 (@value{GDBP}) @b{p lquote}
728 $1 = 0x35d40 "<QUOTE>"
729 (@value{GDBP}) @b{p rquote}
730 $2 = 0x35d50 "<UNQUOTE>"
734 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
735 To look at some context, we can display ten lines of source
736 surrounding the current line with the @code{l} (@code{list}) command.
742 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
744 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
747 538 len_lquote = strlen(rquote);
748 539 len_rquote = strlen(lquote);
755 Let us step past the two lines that set @code{len_lquote} and
756 @code{len_rquote}, and then examine the values of those variables.
760 539 len_rquote = strlen(lquote);
763 (@value{GDBP}) @b{p len_lquote}
765 (@value{GDBP}) @b{p len_rquote}
770 That certainly looks wrong, assuming @code{len_lquote} and
771 @code{len_rquote} are meant to be the lengths of @code{lquote} and
772 @code{rquote} respectively. We can set them to better values using
773 the @code{p} command, since it can print the value of
774 any expression---and that expression can include subroutine calls and
778 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
780 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
785 Is that enough to fix the problem of using the new quotes with the
786 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
787 executing with the @code{c} (@code{continue}) command, and then try the
788 example that caused trouble initially:
794 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
801 Success! The new quotes now work just as well as the default ones. The
802 problem seems to have been just the two typos defining the wrong
803 lengths. We allow @code{m4} exit by giving it an EOF as input:
807 Program exited normally.
811 The message @samp{Program exited normally.} is from @value{GDBN}; it
812 indicates @code{m4} has finished executing. We can end our @value{GDBN}
813 session with the @value{GDBN} @code{quit} command.
816 (@value{GDBP}) @b{quit}
820 @chapter Getting In and Out of @value{GDBN}
822 This chapter discusses how to start @value{GDBN}, and how to get out of it.
826 type @samp{@value{GDBP}} to start @value{GDBN}.
828 type @kbd{quit} or @kbd{Ctrl-d} to exit.
832 * Invoking GDB:: How to start @value{GDBN}
833 * Quitting GDB:: How to quit @value{GDBN}
834 * Shell Commands:: How to use shell commands inside @value{GDBN}
835 * Logging Output:: How to log @value{GDBN}'s output to a file
839 @section Invoking @value{GDBN}
841 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
842 @value{GDBN} reads commands from the terminal until you tell it to exit.
844 You can also run @code{@value{GDBP}} with a variety of arguments and options,
845 to specify more of your debugging environment at the outset.
847 The command-line options described here are designed
848 to cover a variety of situations; in some environments, some of these
849 options may effectively be unavailable.
851 The most usual way to start @value{GDBN} is with one argument,
852 specifying an executable program:
855 @value{GDBP} @var{program}
859 You can also start with both an executable program and a core file
863 @value{GDBP} @var{program} @var{core}
866 You can, instead, specify a process ID as a second argument, if you want
867 to debug a running process:
870 @value{GDBP} @var{program} 1234
874 would attach @value{GDBN} to process @code{1234} (unless you also have a file
875 named @file{1234}; @value{GDBN} does check for a core file first).
877 Taking advantage of the second command-line argument requires a fairly
878 complete operating system; when you use @value{GDBN} as a remote
879 debugger attached to a bare board, there may not be any notion of
880 ``process'', and there is often no way to get a core dump. @value{GDBN}
881 will warn you if it is unable to attach or to read core dumps.
883 You can optionally have @code{@value{GDBP}} pass any arguments after the
884 executable file to the inferior using @code{--args}. This option stops
887 @value{GDBP} --args gcc -O2 -c foo.c
889 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
890 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
892 You can run @code{@value{GDBP}} without printing the front material, which describes
893 @value{GDBN}'s non-warranty, by specifying @code{--silent}
894 (or @code{-q}/@code{--quiet}):
897 @value{GDBP} --silent
901 You can further control how @value{GDBN} starts up by using command-line
902 options. @value{GDBN} itself can remind you of the options available.
912 to display all available options and briefly describe their use
913 (@samp{@value{GDBP} -h} is a shorter equivalent).
915 All options and command line arguments you give are processed
916 in sequential order. The order makes a difference when the
917 @samp{-x} option is used.
921 * File Options:: Choosing files
922 * Mode Options:: Choosing modes
923 * Startup:: What @value{GDBN} does during startup
927 @subsection Choosing Files
929 When @value{GDBN} starts, it reads any arguments other than options as
930 specifying an executable file and core file (or process ID). This is
931 the same as if the arguments were specified by the @samp{-se} and
932 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
933 first argument that does not have an associated option flag as
934 equivalent to the @samp{-se} option followed by that argument; and the
935 second argument that does not have an associated option flag, if any, as
936 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
937 If the second argument begins with a decimal digit, @value{GDBN} will
938 first attempt to attach to it as a process, and if that fails, attempt
939 to open it as a corefile. If you have a corefile whose name begins with
940 a digit, you can prevent @value{GDBN} from treating it as a pid by
941 prefixing it with @file{./}, e.g.@: @file{./12345}.
943 If @value{GDBN} has not been configured to included core file support,
944 such as for most embedded targets, then it will complain about a second
945 argument and ignore it.
947 Many options have both long and short forms; both are shown in the
948 following list. @value{GDBN} also recognizes the long forms if you truncate
949 them, so long as enough of the option is present to be unambiguous.
950 (If you prefer, you can flag option arguments with @samp{--} rather
951 than @samp{-}, though we illustrate the more usual convention.)
953 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
954 @c way, both those who look for -foo and --foo in the index, will find
958 @item -symbols @var{file}
960 @cindex @code{--symbols}
962 Read symbol table from file @var{file}.
964 @item -exec @var{file}
966 @cindex @code{--exec}
968 Use file @var{file} as the executable file to execute when appropriate,
969 and for examining pure data in conjunction with a core dump.
973 Read symbol table from file @var{file} and use it as the executable
976 @item -core @var{file}
978 @cindex @code{--core}
980 Use file @var{file} as a core dump to examine.
982 @item -pid @var{number}
983 @itemx -p @var{number}
986 Connect to process ID @var{number}, as with the @code{attach} command.
988 @item -command @var{file}
990 @cindex @code{--command}
992 Execute commands from file @var{file}. The contents of this file is
993 evaluated exactly as the @code{source} command would.
994 @xref{Command Files,, Command files}.
996 @item -eval-command @var{command}
997 @itemx -ex @var{command}
998 @cindex @code{--eval-command}
1000 Execute a single @value{GDBN} command.
1002 This option may be used multiple times to call multiple commands. It may
1003 also be interleaved with @samp{-command} as required.
1006 @value{GDBP} -ex 'target sim' -ex 'load' \
1007 -x setbreakpoints -ex 'run' a.out
1010 @item -init-command @var{file}
1011 @itemx -ix @var{file}
1012 @cindex @code{--init-command}
1014 Execute commands from file @var{file} before loading the inferior (but
1015 after loading gdbinit files).
1018 @item -init-eval-command @var{command}
1019 @itemx -iex @var{command}
1020 @cindex @code{--init-eval-command}
1022 Execute a single @value{GDBN} command before loading the inferior (but
1023 after loading gdbinit files).
1026 @item -directory @var{directory}
1027 @itemx -d @var{directory}
1028 @cindex @code{--directory}
1030 Add @var{directory} to the path to search for source and script files.
1034 @cindex @code{--readnow}
1036 Read each symbol file's entire symbol table immediately, rather than
1037 the default, which is to read it incrementally as it is needed.
1038 This makes startup slower, but makes future operations faster.
1041 @anchor{--readnever}
1042 @cindex @code{--readnever}, command-line option
1043 Do not read each symbol file's symbolic debug information. This makes
1044 startup faster but at the expense of not being able to perform
1045 symbolic debugging. DWARF unwind information is also not read,
1046 meaning backtraces may become incomplete or inaccurate. One use of
1047 this is when a user simply wants to do the following sequence: attach,
1048 dump core, detach. Loading the debugging information in this case is
1049 an unnecessary cause of delay.
1053 @subsection Choosing Modes
1055 You can run @value{GDBN} in various alternative modes---for example, in
1056 batch mode or quiet mode.
1064 Do not execute commands found in any initialization file.
1065 There are three init files, loaded in the following order:
1068 @item @file{system.gdbinit}
1069 This is the system-wide init file.
1070 Its location is specified with the @code{--with-system-gdbinit}
1071 configure option (@pxref{System-wide configuration}).
1072 It is loaded first when @value{GDBN} starts, before command line options
1073 have been processed.
1074 @item @file{~/.gdbinit}
1075 This is the init file in your home directory.
1076 It is loaded next, after @file{system.gdbinit}, and before
1077 command options have been processed.
1078 @item @file{./.gdbinit}
1079 This is the init file in the current directory.
1080 It is loaded last, after command line options other than @code{-x} and
1081 @code{-ex} have been processed. Command line options @code{-x} and
1082 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1085 For further documentation on startup processing, @xref{Startup}.
1086 For documentation on how to write command files,
1087 @xref{Command Files,,Command Files}.
1092 Do not execute commands found in @file{~/.gdbinit}, the init file
1093 in your home directory.
1099 @cindex @code{--quiet}
1100 @cindex @code{--silent}
1102 ``Quiet''. Do not print the introductory and copyright messages. These
1103 messages are also suppressed in batch mode.
1106 @cindex @code{--batch}
1107 Run in batch mode. Exit with status @code{0} after processing all the
1108 command files specified with @samp{-x} (and all commands from
1109 initialization files, if not inhibited with @samp{-n}). Exit with
1110 nonzero status if an error occurs in executing the @value{GDBN} commands
1111 in the command files. Batch mode also disables pagination, sets unlimited
1112 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1113 off} were in effect (@pxref{Messages/Warnings}).
1115 Batch mode may be useful for running @value{GDBN} as a filter, for
1116 example to download and run a program on another computer; in order to
1117 make this more useful, the message
1120 Program exited normally.
1124 (which is ordinarily issued whenever a program running under
1125 @value{GDBN} control terminates) is not issued when running in batch
1129 @cindex @code{--batch-silent}
1130 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1131 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1132 unaffected). This is much quieter than @samp{-silent} and would be useless
1133 for an interactive session.
1135 This is particularly useful when using targets that give @samp{Loading section}
1136 messages, for example.
1138 Note that targets that give their output via @value{GDBN}, as opposed to
1139 writing directly to @code{stdout}, will also be made silent.
1141 @item -return-child-result
1142 @cindex @code{--return-child-result}
1143 The return code from @value{GDBN} will be the return code from the child
1144 process (the process being debugged), with the following exceptions:
1148 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1149 internal error. In this case the exit code is the same as it would have been
1150 without @samp{-return-child-result}.
1152 The user quits with an explicit value. E.g., @samp{quit 1}.
1154 The child process never runs, or is not allowed to terminate, in which case
1155 the exit code will be -1.
1158 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1159 when @value{GDBN} is being used as a remote program loader or simulator
1164 @cindex @code{--nowindows}
1166 ``No windows''. If @value{GDBN} comes with a graphical user interface
1167 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1168 interface. If no GUI is available, this option has no effect.
1172 @cindex @code{--windows}
1174 If @value{GDBN} includes a GUI, then this option requires it to be
1177 @item -cd @var{directory}
1179 Run @value{GDBN} using @var{directory} as its working directory,
1180 instead of the current directory.
1182 @item -data-directory @var{directory}
1183 @itemx -D @var{directory}
1184 @cindex @code{--data-directory}
1186 Run @value{GDBN} using @var{directory} as its data directory.
1187 The data directory is where @value{GDBN} searches for its
1188 auxiliary files. @xref{Data Files}.
1192 @cindex @code{--fullname}
1194 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1195 subprocess. It tells @value{GDBN} to output the full file name and line
1196 number in a standard, recognizable fashion each time a stack frame is
1197 displayed (which includes each time your program stops). This
1198 recognizable format looks like two @samp{\032} characters, followed by
1199 the file name, line number and character position separated by colons,
1200 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1201 @samp{\032} characters as a signal to display the source code for the
1204 @item -annotate @var{level}
1205 @cindex @code{--annotate}
1206 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1207 effect is identical to using @samp{set annotate @var{level}}
1208 (@pxref{Annotations}). The annotation @var{level} controls how much
1209 information @value{GDBN} prints together with its prompt, values of
1210 expressions, source lines, and other types of output. Level 0 is the
1211 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1212 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1213 that control @value{GDBN}, and level 2 has been deprecated.
1215 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1219 @cindex @code{--args}
1220 Change interpretation of command line so that arguments following the
1221 executable file are passed as command line arguments to the inferior.
1222 This option stops option processing.
1224 @item -baud @var{bps}
1226 @cindex @code{--baud}
1228 Set the line speed (baud rate or bits per second) of any serial
1229 interface used by @value{GDBN} for remote debugging.
1231 @item -l @var{timeout}
1233 Set the timeout (in seconds) of any communication used by @value{GDBN}
1234 for remote debugging.
1236 @item -tty @var{device}
1237 @itemx -t @var{device}
1238 @cindex @code{--tty}
1240 Run using @var{device} for your program's standard input and output.
1241 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1243 @c resolve the situation of these eventually
1245 @cindex @code{--tui}
1246 Activate the @dfn{Text User Interface} when starting. The Text User
1247 Interface manages several text windows on the terminal, showing
1248 source, assembly, registers and @value{GDBN} command outputs
1249 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1250 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1251 Using @value{GDBN} under @sc{gnu} Emacs}).
1253 @item -interpreter @var{interp}
1254 @cindex @code{--interpreter}
1255 Use the interpreter @var{interp} for interface with the controlling
1256 program or device. This option is meant to be set by programs which
1257 communicate with @value{GDBN} using it as a back end.
1258 @xref{Interpreters, , Command Interpreters}.
1260 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1261 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1262 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1263 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1264 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1265 @sc{gdb/mi} interfaces are no longer supported.
1268 @cindex @code{--write}
1269 Open the executable and core files for both reading and writing. This
1270 is equivalent to the @samp{set write on} command inside @value{GDBN}
1274 @cindex @code{--statistics}
1275 This option causes @value{GDBN} to print statistics about time and
1276 memory usage after it completes each command and returns to the prompt.
1279 @cindex @code{--version}
1280 This option causes @value{GDBN} to print its version number and
1281 no-warranty blurb, and exit.
1283 @item -configuration
1284 @cindex @code{--configuration}
1285 This option causes @value{GDBN} to print details about its build-time
1286 configuration parameters, and then exit. These details can be
1287 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1292 @subsection What @value{GDBN} Does During Startup
1293 @cindex @value{GDBN} startup
1295 Here's the description of what @value{GDBN} does during session startup:
1299 Sets up the command interpreter as specified by the command line
1300 (@pxref{Mode Options, interpreter}).
1304 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1305 used when building @value{GDBN}; @pxref{System-wide configuration,
1306 ,System-wide configuration and settings}) and executes all the commands in
1309 @anchor{Home Directory Init File}
1311 Reads the init file (if any) in your home directory@footnote{On
1312 DOS/Windows systems, the home directory is the one pointed to by the
1313 @code{HOME} environment variable.} and executes all the commands in
1316 @anchor{Option -init-eval-command}
1318 Executes commands and command files specified by the @samp{-iex} and
1319 @samp{-ix} options in their specified order. Usually you should use the
1320 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1321 settings before @value{GDBN} init files get executed and before inferior
1325 Processes command line options and operands.
1327 @anchor{Init File in the Current Directory during Startup}
1329 Reads and executes the commands from init file (if any) in the current
1330 working directory as long as @samp{set auto-load local-gdbinit} is set to
1331 @samp{on} (@pxref{Init File in the Current Directory}).
1332 This is only done if the current directory is
1333 different from your home directory. Thus, you can have more than one
1334 init file, one generic in your home directory, and another, specific
1335 to the program you are debugging, in the directory where you invoke
1339 If the command line specified a program to debug, or a process to
1340 attach to, or a core file, @value{GDBN} loads any auto-loaded
1341 scripts provided for the program or for its loaded shared libraries.
1342 @xref{Auto-loading}.
1344 If you wish to disable the auto-loading during startup,
1345 you must do something like the following:
1348 $ gdb -iex "set auto-load python-scripts off" myprogram
1351 Option @samp{-ex} does not work because the auto-loading is then turned
1355 Executes commands and command files specified by the @samp{-ex} and
1356 @samp{-x} options in their specified order. @xref{Command Files}, for
1357 more details about @value{GDBN} command files.
1360 Reads the command history recorded in the @dfn{history file}.
1361 @xref{Command History}, for more details about the command history and the
1362 files where @value{GDBN} records it.
1365 Init files use the same syntax as @dfn{command files} (@pxref{Command
1366 Files}) and are processed by @value{GDBN} in the same way. The init
1367 file in your home directory can set options (such as @samp{set
1368 complaints}) that affect subsequent processing of command line options
1369 and operands. Init files are not executed if you use the @samp{-nx}
1370 option (@pxref{Mode Options, ,Choosing Modes}).
1372 To display the list of init files loaded by gdb at startup, you
1373 can use @kbd{gdb --help}.
1375 @cindex init file name
1376 @cindex @file{.gdbinit}
1377 @cindex @file{gdb.ini}
1378 The @value{GDBN} init files are normally called @file{.gdbinit}.
1379 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1380 the limitations of file names imposed by DOS filesystems. The Windows
1381 port of @value{GDBN} uses the standard name, but if it finds a
1382 @file{gdb.ini} file in your home directory, it warns you about that
1383 and suggests to rename the file to the standard name.
1387 @section Quitting @value{GDBN}
1388 @cindex exiting @value{GDBN}
1389 @cindex leaving @value{GDBN}
1392 @kindex quit @r{[}@var{expression}@r{]}
1393 @kindex q @r{(@code{quit})}
1394 @item quit @r{[}@var{expression}@r{]}
1396 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1397 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1398 do not supply @var{expression}, @value{GDBN} will terminate normally;
1399 otherwise it will terminate using the result of @var{expression} as the
1404 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1405 terminates the action of any @value{GDBN} command that is in progress and
1406 returns to @value{GDBN} command level. It is safe to type the interrupt
1407 character at any time because @value{GDBN} does not allow it to take effect
1408 until a time when it is safe.
1410 If you have been using @value{GDBN} to control an attached process or
1411 device, you can release it with the @code{detach} command
1412 (@pxref{Attach, ,Debugging an Already-running Process}).
1414 @node Shell Commands
1415 @section Shell Commands
1417 If you need to execute occasional shell commands during your
1418 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1419 just use the @code{shell} command.
1424 @cindex shell escape
1425 @item shell @var{command-string}
1426 @itemx !@var{command-string}
1427 Invoke a standard shell to execute @var{command-string}.
1428 Note that no space is needed between @code{!} and @var{command-string}.
1429 If it exists, the environment variable @code{SHELL} determines which
1430 shell to run. Otherwise @value{GDBN} uses the default shell
1431 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1434 The utility @code{make} is often needed in development environments.
1435 You do not have to use the @code{shell} command for this purpose in
1440 @cindex calling make
1441 @item make @var{make-args}
1442 Execute the @code{make} program with the specified
1443 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1446 @node Logging Output
1447 @section Logging Output
1448 @cindex logging @value{GDBN} output
1449 @cindex save @value{GDBN} output to a file
1451 You may want to save the output of @value{GDBN} commands to a file.
1452 There are several commands to control @value{GDBN}'s logging.
1456 @item set logging on
1458 @item set logging off
1460 @cindex logging file name
1461 @item set logging file @var{file}
1462 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1463 @item set logging overwrite [on|off]
1464 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1465 you want @code{set logging on} to overwrite the logfile instead.
1466 @item set logging redirect [on|off]
1467 By default, @value{GDBN} output will go to both the terminal and the logfile.
1468 Set @code{redirect} if you want output to go only to the log file.
1469 @kindex show logging
1471 Show the current values of the logging settings.
1475 @chapter @value{GDBN} Commands
1477 You can abbreviate a @value{GDBN} command to the first few letters of the command
1478 name, if that abbreviation is unambiguous; and you can repeat certain
1479 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1480 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1481 show you the alternatives available, if there is more than one possibility).
1484 * Command Syntax:: How to give commands to @value{GDBN}
1485 * Completion:: Command completion
1486 * Help:: How to ask @value{GDBN} for help
1489 @node Command Syntax
1490 @section Command Syntax
1492 A @value{GDBN} command is a single line of input. There is no limit on
1493 how long it can be. It starts with a command name, which is followed by
1494 arguments whose meaning depends on the command name. For example, the
1495 command @code{step} accepts an argument which is the number of times to
1496 step, as in @samp{step 5}. You can also use the @code{step} command
1497 with no arguments. Some commands do not allow any arguments.
1499 @cindex abbreviation
1500 @value{GDBN} command names may always be truncated if that abbreviation is
1501 unambiguous. Other possible command abbreviations are listed in the
1502 documentation for individual commands. In some cases, even ambiguous
1503 abbreviations are allowed; for example, @code{s} is specially defined as
1504 equivalent to @code{step} even though there are other commands whose
1505 names start with @code{s}. You can test abbreviations by using them as
1506 arguments to the @code{help} command.
1508 @cindex repeating commands
1509 @kindex RET @r{(repeat last command)}
1510 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1511 repeat the previous command. Certain commands (for example, @code{run})
1512 will not repeat this way; these are commands whose unintentional
1513 repetition might cause trouble and which you are unlikely to want to
1514 repeat. User-defined commands can disable this feature; see
1515 @ref{Define, dont-repeat}.
1517 The @code{list} and @code{x} commands, when you repeat them with
1518 @key{RET}, construct new arguments rather than repeating
1519 exactly as typed. This permits easy scanning of source or memory.
1521 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1522 output, in a way similar to the common utility @code{more}
1523 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1524 @key{RET} too many in this situation, @value{GDBN} disables command
1525 repetition after any command that generates this sort of display.
1527 @kindex # @r{(a comment)}
1529 Any text from a @kbd{#} to the end of the line is a comment; it does
1530 nothing. This is useful mainly in command files (@pxref{Command
1531 Files,,Command Files}).
1533 @cindex repeating command sequences
1534 @kindex Ctrl-o @r{(operate-and-get-next)}
1535 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1536 commands. This command accepts the current line, like @key{RET}, and
1537 then fetches the next line relative to the current line from the history
1541 @section Command Completion
1544 @cindex word completion
1545 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1546 only one possibility; it can also show you what the valid possibilities
1547 are for the next word in a command, at any time. This works for @value{GDBN}
1548 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1550 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1551 of a word. If there is only one possibility, @value{GDBN} fills in the
1552 word, and waits for you to finish the command (or press @key{RET} to
1553 enter it). For example, if you type
1555 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1556 @c complete accuracy in these examples; space introduced for clarity.
1557 @c If texinfo enhancements make it unnecessary, it would be nice to
1558 @c replace " @key" by "@key" in the following...
1560 (@value{GDBP}) info bre @key{TAB}
1564 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1565 the only @code{info} subcommand beginning with @samp{bre}:
1568 (@value{GDBP}) info breakpoints
1572 You can either press @key{RET} at this point, to run the @code{info
1573 breakpoints} command, or backspace and enter something else, if
1574 @samp{breakpoints} does not look like the command you expected. (If you
1575 were sure you wanted @code{info breakpoints} in the first place, you
1576 might as well just type @key{RET} immediately after @samp{info bre},
1577 to exploit command abbreviations rather than command completion).
1579 If there is more than one possibility for the next word when you press
1580 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1581 characters and try again, or just press @key{TAB} a second time;
1582 @value{GDBN} displays all the possible completions for that word. For
1583 example, you might want to set a breakpoint on a subroutine whose name
1584 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1585 just sounds the bell. Typing @key{TAB} again displays all the
1586 function names in your program that begin with those characters, for
1590 (@value{GDBP}) b make_ @key{TAB}
1591 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1592 make_a_section_from_file make_environ
1593 make_abs_section make_function_type
1594 make_blockvector make_pointer_type
1595 make_cleanup make_reference_type
1596 make_command make_symbol_completion_list
1597 (@value{GDBP}) b make_
1601 After displaying the available possibilities, @value{GDBN} copies your
1602 partial input (@samp{b make_} in the example) so you can finish the
1605 If you just want to see the list of alternatives in the first place, you
1606 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1607 means @kbd{@key{META} ?}. You can type this either by holding down a
1608 key designated as the @key{META} shift on your keyboard (if there is
1609 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1611 If the number of possible completions is large, @value{GDBN} will
1612 print as much of the list as it has collected, as well as a message
1613 indicating that the list may be truncated.
1616 (@value{GDBP}) b m@key{TAB}@key{TAB}
1618 <... the rest of the possible completions ...>
1619 *** List may be truncated, max-completions reached. ***
1624 This behavior can be controlled with the following commands:
1627 @kindex set max-completions
1628 @item set max-completions @var{limit}
1629 @itemx set max-completions unlimited
1630 Set the maximum number of completion candidates. @value{GDBN} will
1631 stop looking for more completions once it collects this many candidates.
1632 This is useful when completing on things like function names as collecting
1633 all the possible candidates can be time consuming.
1634 The default value is 200. A value of zero disables tab-completion.
1635 Note that setting either no limit or a very large limit can make
1637 @kindex show max-completions
1638 @item show max-completions
1639 Show the maximum number of candidates that @value{GDBN} will collect and show
1643 @cindex quotes in commands
1644 @cindex completion of quoted strings
1645 Sometimes the string you need, while logically a ``word'', may contain
1646 parentheses or other characters that @value{GDBN} normally excludes from
1647 its notion of a word. To permit word completion to work in this
1648 situation, you may enclose words in @code{'} (single quote marks) in
1649 @value{GDBN} commands.
1651 A likely situation where you might need this is in typing an
1652 expression that involves a C@t{++} symbol name with template
1653 parameters. This is because when completing expressions, GDB treats
1654 the @samp{<} character as word delimiter, assuming that it's the
1655 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1658 For example, when you want to call a C@t{++} template function
1659 interactively using the @code{print} or @code{call} commands, you may
1660 need to distinguish whether you mean the version of @code{name} that
1661 was specialized for @code{int}, @code{name<int>()}, or the version
1662 that was specialized for @code{float}, @code{name<float>()}. To use
1663 the word-completion facilities in this situation, type a single quote
1664 @code{'} at the beginning of the function name. This alerts
1665 @value{GDBN} that it may need to consider more information than usual
1666 when you press @key{TAB} or @kbd{M-?} to request word completion:
1669 (@value{GDBP}) p 'func< @kbd{M-?}
1670 func<int>() func<float>()
1671 (@value{GDBP}) p 'func<
1674 When setting breakpoints however (@pxref{Specify Location}), you don't
1675 usually need to type a quote before the function name, because
1676 @value{GDBN} understands that you want to set a breakpoint on a
1680 (@value{GDBP}) b func< @kbd{M-?}
1681 func<int>() func<float>()
1682 (@value{GDBP}) b func<
1685 This is true even in the case of typing the name of C@t{++} overloaded
1686 functions (multiple definitions of the same function, distinguished by
1687 argument type). For example, when you want to set a breakpoint you
1688 don't need to distinguish whether you mean the version of @code{name}
1689 that takes an @code{int} parameter, @code{name(int)}, or the version
1690 that takes a @code{float} parameter, @code{name(float)}.
1693 (@value{GDBP}) b bubble( @kbd{M-?}
1694 bubble(int) bubble(double)
1695 (@value{GDBP}) b bubble(dou @kbd{M-?}
1699 See @ref{quoting names} for a description of other scenarios that
1702 For more information about overloaded functions, see @ref{C Plus Plus
1703 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1704 overload-resolution off} to disable overload resolution;
1705 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1707 @cindex completion of structure field names
1708 @cindex structure field name completion
1709 @cindex completion of union field names
1710 @cindex union field name completion
1711 When completing in an expression which looks up a field in a
1712 structure, @value{GDBN} also tries@footnote{The completer can be
1713 confused by certain kinds of invalid expressions. Also, it only
1714 examines the static type of the expression, not the dynamic type.} to
1715 limit completions to the field names available in the type of the
1719 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1720 magic to_fputs to_rewind
1721 to_data to_isatty to_write
1722 to_delete to_put to_write_async_safe
1727 This is because the @code{gdb_stdout} is a variable of the type
1728 @code{struct ui_file} that is defined in @value{GDBN} sources as
1735 ui_file_flush_ftype *to_flush;
1736 ui_file_write_ftype *to_write;
1737 ui_file_write_async_safe_ftype *to_write_async_safe;
1738 ui_file_fputs_ftype *to_fputs;
1739 ui_file_read_ftype *to_read;
1740 ui_file_delete_ftype *to_delete;
1741 ui_file_isatty_ftype *to_isatty;
1742 ui_file_rewind_ftype *to_rewind;
1743 ui_file_put_ftype *to_put;
1750 @section Getting Help
1751 @cindex online documentation
1754 You can always ask @value{GDBN} itself for information on its commands,
1755 using the command @code{help}.
1758 @kindex h @r{(@code{help})}
1761 You can use @code{help} (abbreviated @code{h}) with no arguments to
1762 display a short list of named classes of commands:
1766 List of classes of commands:
1768 aliases -- Aliases of other commands
1769 breakpoints -- Making program stop at certain points
1770 data -- Examining data
1771 files -- Specifying and examining files
1772 internals -- Maintenance commands
1773 obscure -- Obscure features
1774 running -- Running the program
1775 stack -- Examining the stack
1776 status -- Status inquiries
1777 support -- Support facilities
1778 tracepoints -- Tracing of program execution without
1779 stopping the program
1780 user-defined -- User-defined commands
1782 Type "help" followed by a class name for a list of
1783 commands in that class.
1784 Type "help" followed by command name for full
1786 Command name abbreviations are allowed if unambiguous.
1789 @c the above line break eliminates huge line overfull...
1791 @item help @var{class}
1792 Using one of the general help classes as an argument, you can get a
1793 list of the individual commands in that class. For example, here is the
1794 help display for the class @code{status}:
1797 (@value{GDBP}) help status
1802 @c Line break in "show" line falsifies real output, but needed
1803 @c to fit in smallbook page size.
1804 info -- Generic command for showing things
1805 about the program being debugged
1806 show -- Generic command for showing things
1809 Type "help" followed by command name for full
1811 Command name abbreviations are allowed if unambiguous.
1815 @item help @var{command}
1816 With a command name as @code{help} argument, @value{GDBN} displays a
1817 short paragraph on how to use that command.
1820 @item apropos @var{args}
1821 The @code{apropos} command searches through all of the @value{GDBN}
1822 commands, and their documentation, for the regular expression specified in
1823 @var{args}. It prints out all matches found. For example:
1834 alias -- Define a new command that is an alias of an existing command
1835 aliases -- Aliases of other commands
1836 d -- Delete some breakpoints or auto-display expressions
1837 del -- Delete some breakpoints or auto-display expressions
1838 delete -- Delete some breakpoints or auto-display expressions
1843 @item complete @var{args}
1844 The @code{complete @var{args}} command lists all the possible completions
1845 for the beginning of a command. Use @var{args} to specify the beginning of the
1846 command you want completed. For example:
1852 @noindent results in:
1863 @noindent This is intended for use by @sc{gnu} Emacs.
1866 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1867 and @code{show} to inquire about the state of your program, or the state
1868 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1869 manual introduces each of them in the appropriate context. The listings
1870 under @code{info} and under @code{show} in the Command, Variable, and
1871 Function Index point to all the sub-commands. @xref{Command and Variable
1877 @kindex i @r{(@code{info})}
1879 This command (abbreviated @code{i}) is for describing the state of your
1880 program. For example, you can show the arguments passed to a function
1881 with @code{info args}, list the registers currently in use with @code{info
1882 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1883 You can get a complete list of the @code{info} sub-commands with
1884 @w{@code{help info}}.
1888 You can assign the result of an expression to an environment variable with
1889 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1890 @code{set prompt $}.
1894 In contrast to @code{info}, @code{show} is for describing the state of
1895 @value{GDBN} itself.
1896 You can change most of the things you can @code{show}, by using the
1897 related command @code{set}; for example, you can control what number
1898 system is used for displays with @code{set radix}, or simply inquire
1899 which is currently in use with @code{show radix}.
1902 To display all the settable parameters and their current
1903 values, you can use @code{show} with no arguments; you may also use
1904 @code{info set}. Both commands produce the same display.
1905 @c FIXME: "info set" violates the rule that "info" is for state of
1906 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1907 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1911 Here are several miscellaneous @code{show} subcommands, all of which are
1912 exceptional in lacking corresponding @code{set} commands:
1915 @kindex show version
1916 @cindex @value{GDBN} version number
1918 Show what version of @value{GDBN} is running. You should include this
1919 information in @value{GDBN} bug-reports. If multiple versions of
1920 @value{GDBN} are in use at your site, you may need to determine which
1921 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1922 commands are introduced, and old ones may wither away. Also, many
1923 system vendors ship variant versions of @value{GDBN}, and there are
1924 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1925 The version number is the same as the one announced when you start
1928 @kindex show copying
1929 @kindex info copying
1930 @cindex display @value{GDBN} copyright
1933 Display information about permission for copying @value{GDBN}.
1935 @kindex show warranty
1936 @kindex info warranty
1938 @itemx info warranty
1939 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1940 if your version of @value{GDBN} comes with one.
1942 @kindex show configuration
1943 @item show configuration
1944 Display detailed information about the way @value{GDBN} was configured
1945 when it was built. This displays the optional arguments passed to the
1946 @file{configure} script and also configuration parameters detected
1947 automatically by @command{configure}. When reporting a @value{GDBN}
1948 bug (@pxref{GDB Bugs}), it is important to include this information in
1954 @chapter Running Programs Under @value{GDBN}
1956 When you run a program under @value{GDBN}, you must first generate
1957 debugging information when you compile it.
1959 You may start @value{GDBN} with its arguments, if any, in an environment
1960 of your choice. If you are doing native debugging, you may redirect
1961 your program's input and output, debug an already running process, or
1962 kill a child process.
1965 * Compilation:: Compiling for debugging
1966 * Starting:: Starting your program
1967 * Arguments:: Your program's arguments
1968 * Environment:: Your program's environment
1970 * Working Directory:: Your program's working directory
1971 * Input/Output:: Your program's input and output
1972 * Attach:: Debugging an already-running process
1973 * Kill Process:: Killing the child process
1975 * Inferiors and Programs:: Debugging multiple inferiors and programs
1976 * Threads:: Debugging programs with multiple threads
1977 * Forks:: Debugging forks
1978 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1982 @section Compiling for Debugging
1984 In order to debug a program effectively, you need to generate
1985 debugging information when you compile it. This debugging information
1986 is stored in the object file; it describes the data type of each
1987 variable or function and the correspondence between source line numbers
1988 and addresses in the executable code.
1990 To request debugging information, specify the @samp{-g} option when you run
1993 Programs that are to be shipped to your customers are compiled with
1994 optimizations, using the @samp{-O} compiler option. However, some
1995 compilers are unable to handle the @samp{-g} and @samp{-O} options
1996 together. Using those compilers, you cannot generate optimized
1997 executables containing debugging information.
1999 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2000 without @samp{-O}, making it possible to debug optimized code. We
2001 recommend that you @emph{always} use @samp{-g} whenever you compile a
2002 program. You may think your program is correct, but there is no sense
2003 in pushing your luck. For more information, see @ref{Optimized Code}.
2005 Older versions of the @sc{gnu} C compiler permitted a variant option
2006 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2007 format; if your @sc{gnu} C compiler has this option, do not use it.
2009 @value{GDBN} knows about preprocessor macros and can show you their
2010 expansion (@pxref{Macros}). Most compilers do not include information
2011 about preprocessor macros in the debugging information if you specify
2012 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2013 the @sc{gnu} C compiler, provides macro information if you are using
2014 the DWARF debugging format, and specify the option @option{-g3}.
2016 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2017 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2018 information on @value{NGCC} options affecting debug information.
2020 You will have the best debugging experience if you use the latest
2021 version of the DWARF debugging format that your compiler supports.
2022 DWARF is currently the most expressive and best supported debugging
2023 format in @value{GDBN}.
2027 @section Starting your Program
2033 @kindex r @r{(@code{run})}
2036 Use the @code{run} command to start your program under @value{GDBN}.
2037 You must first specify the program name with an argument to
2038 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2039 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2040 command (@pxref{Files, ,Commands to Specify Files}).
2044 If you are running your program in an execution environment that
2045 supports processes, @code{run} creates an inferior process and makes
2046 that process run your program. In some environments without processes,
2047 @code{run} jumps to the start of your program. Other targets,
2048 like @samp{remote}, are always running. If you get an error
2049 message like this one:
2052 The "remote" target does not support "run".
2053 Try "help target" or "continue".
2057 then use @code{continue} to run your program. You may need @code{load}
2058 first (@pxref{load}).
2060 The execution of a program is affected by certain information it
2061 receives from its superior. @value{GDBN} provides ways to specify this
2062 information, which you must do @emph{before} starting your program. (You
2063 can change it after starting your program, but such changes only affect
2064 your program the next time you start it.) This information may be
2065 divided into four categories:
2068 @item The @emph{arguments.}
2069 Specify the arguments to give your program as the arguments of the
2070 @code{run} command. If a shell is available on your target, the shell
2071 is used to pass the arguments, so that you may use normal conventions
2072 (such as wildcard expansion or variable substitution) in describing
2074 In Unix systems, you can control which shell is used with the
2075 @code{SHELL} environment variable. If you do not define @code{SHELL},
2076 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2077 use of any shell with the @code{set startup-with-shell} command (see
2080 @item The @emph{environment.}
2081 Your program normally inherits its environment from @value{GDBN}, but you can
2082 use the @value{GDBN} commands @code{set environment} and @code{unset
2083 environment} to change parts of the environment that affect
2084 your program. @xref{Environment, ,Your Program's Environment}.
2086 @item The @emph{working directory.}
2087 You can set your program's working directory with the command
2088 @kbd{set cwd}. If you do not set any working directory with this
2089 command, your program will inherit @value{GDBN}'s working directory if
2090 native debugging, or the remote server's working directory if remote
2091 debugging. @xref{Working Directory, ,Your Program's Working
2094 @item The @emph{standard input and output.}
2095 Your program normally uses the same device for standard input and
2096 standard output as @value{GDBN} is using. You can redirect input and output
2097 in the @code{run} command line, or you can use the @code{tty} command to
2098 set a different device for your program.
2099 @xref{Input/Output, ,Your Program's Input and Output}.
2102 @emph{Warning:} While input and output redirection work, you cannot use
2103 pipes to pass the output of the program you are debugging to another
2104 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2108 When you issue the @code{run} command, your program begins to execute
2109 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2110 of how to arrange for your program to stop. Once your program has
2111 stopped, you may call functions in your program, using the @code{print}
2112 or @code{call} commands. @xref{Data, ,Examining Data}.
2114 If the modification time of your symbol file has changed since the last
2115 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2116 table, and reads it again. When it does this, @value{GDBN} tries to retain
2117 your current breakpoints.
2122 @cindex run to main procedure
2123 The name of the main procedure can vary from language to language.
2124 With C or C@t{++}, the main procedure name is always @code{main}, but
2125 other languages such as Ada do not require a specific name for their
2126 main procedure. The debugger provides a convenient way to start the
2127 execution of the program and to stop at the beginning of the main
2128 procedure, depending on the language used.
2130 The @samp{start} command does the equivalent of setting a temporary
2131 breakpoint at the beginning of the main procedure and then invoking
2132 the @samp{run} command.
2134 @cindex elaboration phase
2135 Some programs contain an @dfn{elaboration} phase where some startup code is
2136 executed before the main procedure is called. This depends on the
2137 languages used to write your program. In C@t{++}, for instance,
2138 constructors for static and global objects are executed before
2139 @code{main} is called. It is therefore possible that the debugger stops
2140 before reaching the main procedure. However, the temporary breakpoint
2141 will remain to halt execution.
2143 Specify the arguments to give to your program as arguments to the
2144 @samp{start} command. These arguments will be given verbatim to the
2145 underlying @samp{run} command. Note that the same arguments will be
2146 reused if no argument is provided during subsequent calls to
2147 @samp{start} or @samp{run}.
2149 It is sometimes necessary to debug the program during elaboration. In
2150 these cases, using the @code{start} command would stop the execution
2151 of your program too late, as the program would have already completed
2152 the elaboration phase. Under these circumstances, either insert
2153 breakpoints in your elaboration code before running your program or
2154 use the @code{starti} command.
2158 @cindex run to first instruction
2159 The @samp{starti} command does the equivalent of setting a temporary
2160 breakpoint at the first instruction of a program's execution and then
2161 invoking the @samp{run} command. For programs containing an
2162 elaboration phase, the @code{starti} command will stop execution at
2163 the start of the elaboration phase.
2165 @anchor{set exec-wrapper}
2166 @kindex set exec-wrapper
2167 @item set exec-wrapper @var{wrapper}
2168 @itemx show exec-wrapper
2169 @itemx unset exec-wrapper
2170 When @samp{exec-wrapper} is set, the specified wrapper is used to
2171 launch programs for debugging. @value{GDBN} starts your program
2172 with a shell command of the form @kbd{exec @var{wrapper}
2173 @var{program}}. Quoting is added to @var{program} and its
2174 arguments, but not to @var{wrapper}, so you should add quotes if
2175 appropriate for your shell. The wrapper runs until it executes
2176 your program, and then @value{GDBN} takes control.
2178 You can use any program that eventually calls @code{execve} with
2179 its arguments as a wrapper. Several standard Unix utilities do
2180 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2181 with @code{exec "$@@"} will also work.
2183 For example, you can use @code{env} to pass an environment variable to
2184 the debugged program, without setting the variable in your shell's
2188 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2192 This command is available when debugging locally on most targets, excluding
2193 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2195 @kindex set startup-with-shell
2196 @anchor{set startup-with-shell}
2197 @item set startup-with-shell
2198 @itemx set startup-with-shell on
2199 @itemx set startup-with-shell off
2200 @itemx show startup-with-shell
2201 On Unix systems, by default, if a shell is available on your target,
2202 @value{GDBN}) uses it to start your program. Arguments of the
2203 @code{run} command are passed to the shell, which does variable
2204 substitution, expands wildcard characters and performs redirection of
2205 I/O. In some circumstances, it may be useful to disable such use of a
2206 shell, for example, when debugging the shell itself or diagnosing
2207 startup failures such as:
2211 Starting program: ./a.out
2212 During startup program terminated with signal SIGSEGV, Segmentation fault.
2216 which indicates the shell or the wrapper specified with
2217 @samp{exec-wrapper} crashed, not your program. Most often, this is
2218 caused by something odd in your shell's non-interactive mode
2219 initialization file---such as @file{.cshrc} for C-shell,
2220 $@file{.zshenv} for the Z shell, or the file specified in the
2221 @samp{BASH_ENV} environment variable for BASH.
2223 @anchor{set auto-connect-native-target}
2224 @kindex set auto-connect-native-target
2225 @item set auto-connect-native-target
2226 @itemx set auto-connect-native-target on
2227 @itemx set auto-connect-native-target off
2228 @itemx show auto-connect-native-target
2230 By default, if not connected to any target yet (e.g., with
2231 @code{target remote}), the @code{run} command starts your program as a
2232 native process under @value{GDBN}, on your local machine. If you're
2233 sure you don't want to debug programs on your local machine, you can
2234 tell @value{GDBN} to not connect to the native target automatically
2235 with the @code{set auto-connect-native-target off} command.
2237 If @code{on}, which is the default, and if @value{GDBN} is not
2238 connected to a target already, the @code{run} command automaticaly
2239 connects to the native target, if one is available.
2241 If @code{off}, and if @value{GDBN} is not connected to a target
2242 already, the @code{run} command fails with an error:
2246 Don't know how to run. Try "help target".
2249 If @value{GDBN} is already connected to a target, @value{GDBN} always
2250 uses it with the @code{run} command.
2252 In any case, you can explicitly connect to the native target with the
2253 @code{target native} command. For example,
2256 (@value{GDBP}) set auto-connect-native-target off
2258 Don't know how to run. Try "help target".
2259 (@value{GDBP}) target native
2261 Starting program: ./a.out
2262 [Inferior 1 (process 10421) exited normally]
2265 In case you connected explicitly to the @code{native} target,
2266 @value{GDBN} remains connected even if all inferiors exit, ready for
2267 the next @code{run} command. Use the @code{disconnect} command to
2270 Examples of other commands that likewise respect the
2271 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2272 proc}, @code{info os}.
2274 @kindex set disable-randomization
2275 @item set disable-randomization
2276 @itemx set disable-randomization on
2277 This option (enabled by default in @value{GDBN}) will turn off the native
2278 randomization of the virtual address space of the started program. This option
2279 is useful for multiple debugging sessions to make the execution better
2280 reproducible and memory addresses reusable across debugging sessions.
2282 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2283 On @sc{gnu}/Linux you can get the same behavior using
2286 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2289 @item set disable-randomization off
2290 Leave the behavior of the started executable unchanged. Some bugs rear their
2291 ugly heads only when the program is loaded at certain addresses. If your bug
2292 disappears when you run the program under @value{GDBN}, that might be because
2293 @value{GDBN} by default disables the address randomization on platforms, such
2294 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2295 disable-randomization off} to try to reproduce such elusive bugs.
2297 On targets where it is available, virtual address space randomization
2298 protects the programs against certain kinds of security attacks. In these
2299 cases the attacker needs to know the exact location of a concrete executable
2300 code. Randomizing its location makes it impossible to inject jumps misusing
2301 a code at its expected addresses.
2303 Prelinking shared libraries provides a startup performance advantage but it
2304 makes addresses in these libraries predictable for privileged processes by
2305 having just unprivileged access at the target system. Reading the shared
2306 library binary gives enough information for assembling the malicious code
2307 misusing it. Still even a prelinked shared library can get loaded at a new
2308 random address just requiring the regular relocation process during the
2309 startup. Shared libraries not already prelinked are always loaded at
2310 a randomly chosen address.
2312 Position independent executables (PIE) contain position independent code
2313 similar to the shared libraries and therefore such executables get loaded at
2314 a randomly chosen address upon startup. PIE executables always load even
2315 already prelinked shared libraries at a random address. You can build such
2316 executable using @command{gcc -fPIE -pie}.
2318 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2319 (as long as the randomization is enabled).
2321 @item show disable-randomization
2322 Show the current setting of the explicit disable of the native randomization of
2323 the virtual address space of the started program.
2328 @section Your Program's Arguments
2330 @cindex arguments (to your program)
2331 The arguments to your program can be specified by the arguments of the
2333 They are passed to a shell, which expands wildcard characters and
2334 performs redirection of I/O, and thence to your program. Your
2335 @code{SHELL} environment variable (if it exists) specifies what shell
2336 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2337 the default shell (@file{/bin/sh} on Unix).
2339 On non-Unix systems, the program is usually invoked directly by
2340 @value{GDBN}, which emulates I/O redirection via the appropriate system
2341 calls, and the wildcard characters are expanded by the startup code of
2342 the program, not by the shell.
2344 @code{run} with no arguments uses the same arguments used by the previous
2345 @code{run}, or those set by the @code{set args} command.
2350 Specify the arguments to be used the next time your program is run. If
2351 @code{set args} has no arguments, @code{run} executes your program
2352 with no arguments. Once you have run your program with arguments,
2353 using @code{set args} before the next @code{run} is the only way to run
2354 it again without arguments.
2358 Show the arguments to give your program when it is started.
2362 @section Your Program's Environment
2364 @cindex environment (of your program)
2365 The @dfn{environment} consists of a set of environment variables and
2366 their values. Environment variables conventionally record such things as
2367 your user name, your home directory, your terminal type, and your search
2368 path for programs to run. Usually you set up environment variables with
2369 the shell and they are inherited by all the other programs you run. When
2370 debugging, it can be useful to try running your program with a modified
2371 environment without having to start @value{GDBN} over again.
2375 @item path @var{directory}
2376 Add @var{directory} to the front of the @code{PATH} environment variable
2377 (the search path for executables) that will be passed to your program.
2378 The value of @code{PATH} used by @value{GDBN} does not change.
2379 You may specify several directory names, separated by whitespace or by a
2380 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2381 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2382 is moved to the front, so it is searched sooner.
2384 You can use the string @samp{$cwd} to refer to whatever is the current
2385 working directory at the time @value{GDBN} searches the path. If you
2386 use @samp{.} instead, it refers to the directory where you executed the
2387 @code{path} command. @value{GDBN} replaces @samp{.} in the
2388 @var{directory} argument (with the current path) before adding
2389 @var{directory} to the search path.
2390 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2391 @c document that, since repeating it would be a no-op.
2395 Display the list of search paths for executables (the @code{PATH}
2396 environment variable).
2398 @kindex show environment
2399 @item show environment @r{[}@var{varname}@r{]}
2400 Print the value of environment variable @var{varname} to be given to
2401 your program when it starts. If you do not supply @var{varname},
2402 print the names and values of all environment variables to be given to
2403 your program. You can abbreviate @code{environment} as @code{env}.
2405 @kindex set environment
2406 @anchor{set environment}
2407 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2408 Set environment variable @var{varname} to @var{value}. The value
2409 changes for your program (and the shell @value{GDBN} uses to launch
2410 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2411 values of environment variables are just strings, and any
2412 interpretation is supplied by your program itself. The @var{value}
2413 parameter is optional; if it is eliminated, the variable is set to a
2415 @c "any string" here does not include leading, trailing
2416 @c blanks. Gnu asks: does anyone care?
2418 For example, this command:
2425 tells the debugged program, when subsequently run, that its user is named
2426 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2427 are not actually required.)
2429 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2430 which also inherits the environment set with @code{set environment}.
2431 If necessary, you can avoid that by using the @samp{env} program as a
2432 wrapper instead of using @code{set environment}. @xref{set
2433 exec-wrapper}, for an example doing just that.
2435 Environment variables that are set by the user are also transmitted to
2436 @command{gdbserver} to be used when starting the remote inferior.
2437 @pxref{QEnvironmentHexEncoded}.
2439 @kindex unset environment
2440 @anchor{unset environment}
2441 @item unset environment @var{varname}
2442 Remove variable @var{varname} from the environment to be passed to your
2443 program. This is different from @samp{set env @var{varname} =};
2444 @code{unset environment} removes the variable from the environment,
2445 rather than assigning it an empty value.
2447 Environment variables that are unset by the user are also unset on
2448 @command{gdbserver} when starting the remote inferior.
2449 @pxref{QEnvironmentUnset}.
2452 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2453 the shell indicated by your @code{SHELL} environment variable if it
2454 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2455 names a shell that runs an initialization file when started
2456 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2457 for the Z shell, or the file specified in the @samp{BASH_ENV}
2458 environment variable for BASH---any variables you set in that file
2459 affect your program. You may wish to move setting of environment
2460 variables to files that are only run when you sign on, such as
2461 @file{.login} or @file{.profile}.
2463 @node Working Directory
2464 @section Your Program's Working Directory
2466 @cindex working directory (of your program)
2467 Each time you start your program with @code{run}, the inferior will be
2468 initialized with the current working directory specified by the
2469 @kbd{set cwd} command. If no directory has been specified by this
2470 command, then the inferior will inherit @value{GDBN}'s current working
2471 directory as its working directory if native debugging, or it will
2472 inherit the remote server's current working directory if remote
2477 @cindex change inferior's working directory
2478 @anchor{set cwd command}
2479 @item set cwd @r{[}@var{directory}@r{]}
2480 Set the inferior's working directory to @var{directory}, which will be
2481 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2482 argument has been specified, the command clears the setting and resets
2483 it to an empty state. This setting has no effect on @value{GDBN}'s
2484 working directory, and it only takes effect the next time you start
2485 the inferior. The @file{~} in @var{directory} is a short for the
2486 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2487 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2488 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2491 You can also change @value{GDBN}'s current working directory by using
2492 the @code{cd} command.
2496 @cindex show inferior's working directory
2498 Show the inferior's working directory. If no directory has been
2499 specified by @kbd{set cwd}, then the default inferior's working
2500 directory is the same as @value{GDBN}'s working directory.
2503 @cindex change @value{GDBN}'s working directory
2505 @item cd @r{[}@var{directory}@r{]}
2506 Set the @value{GDBN} working directory to @var{directory}. If not
2507 given, @var{directory} uses @file{'~'}.
2509 The @value{GDBN} working directory serves as a default for the
2510 commands that specify files for @value{GDBN} to operate on.
2511 @xref{Files, ,Commands to Specify Files}.
2512 @xref{set cwd command}
2516 Print the @value{GDBN} working directory.
2519 It is generally impossible to find the current working directory of
2520 the process being debugged (since a program can change its directory
2521 during its run). If you work on a system where @value{GDBN} is
2522 configured with the @file{/proc} support, you can use the @code{info
2523 proc} command (@pxref{SVR4 Process Information}) to find out the
2524 current working directory of the debuggee.
2527 @section Your Program's Input and Output
2532 By default, the program you run under @value{GDBN} does input and output to
2533 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2534 to its own terminal modes to interact with you, but it records the terminal
2535 modes your program was using and switches back to them when you continue
2536 running your program.
2539 @kindex info terminal
2541 Displays information recorded by @value{GDBN} about the terminal modes your
2545 You can redirect your program's input and/or output using shell
2546 redirection with the @code{run} command. For example,
2553 starts your program, diverting its output to the file @file{outfile}.
2556 @cindex controlling terminal
2557 Another way to specify where your program should do input and output is
2558 with the @code{tty} command. This command accepts a file name as
2559 argument, and causes this file to be the default for future @code{run}
2560 commands. It also resets the controlling terminal for the child
2561 process, for future @code{run} commands. For example,
2568 directs that processes started with subsequent @code{run} commands
2569 default to do input and output on the terminal @file{/dev/ttyb} and have
2570 that as their controlling terminal.
2572 An explicit redirection in @code{run} overrides the @code{tty} command's
2573 effect on the input/output device, but not its effect on the controlling
2576 When you use the @code{tty} command or redirect input in the @code{run}
2577 command, only the input @emph{for your program} is affected. The input
2578 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2579 for @code{set inferior-tty}.
2581 @cindex inferior tty
2582 @cindex set inferior controlling terminal
2583 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2584 display the name of the terminal that will be used for future runs of your
2588 @item set inferior-tty [ @var{tty} ]
2589 @kindex set inferior-tty
2590 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2591 restores the default behavior, which is to use the same terminal as
2594 @item show inferior-tty
2595 @kindex show inferior-tty
2596 Show the current tty for the program being debugged.
2600 @section Debugging an Already-running Process
2605 @item attach @var{process-id}
2606 This command attaches to a running process---one that was started
2607 outside @value{GDBN}. (@code{info files} shows your active
2608 targets.) The command takes as argument a process ID. The usual way to
2609 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2610 or with the @samp{jobs -l} shell command.
2612 @code{attach} does not repeat if you press @key{RET} a second time after
2613 executing the command.
2616 To use @code{attach}, your program must be running in an environment
2617 which supports processes; for example, @code{attach} does not work for
2618 programs on bare-board targets that lack an operating system. You must
2619 also have permission to send the process a signal.
2621 When you use @code{attach}, the debugger finds the program running in
2622 the process first by looking in the current working directory, then (if
2623 the program is not found) by using the source file search path
2624 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2625 the @code{file} command to load the program. @xref{Files, ,Commands to
2628 The first thing @value{GDBN} does after arranging to debug the specified
2629 process is to stop it. You can examine and modify an attached process
2630 with all the @value{GDBN} commands that are ordinarily available when
2631 you start processes with @code{run}. You can insert breakpoints; you
2632 can step and continue; you can modify storage. If you would rather the
2633 process continue running, you may use the @code{continue} command after
2634 attaching @value{GDBN} to the process.
2639 When you have finished debugging the attached process, you can use the
2640 @code{detach} command to release it from @value{GDBN} control. Detaching
2641 the process continues its execution. After the @code{detach} command,
2642 that process and @value{GDBN} become completely independent once more, and you
2643 are ready to @code{attach} another process or start one with @code{run}.
2644 @code{detach} does not repeat if you press @key{RET} again after
2645 executing the command.
2648 If you exit @value{GDBN} while you have an attached process, you detach
2649 that process. If you use the @code{run} command, you kill that process.
2650 By default, @value{GDBN} asks for confirmation if you try to do either of these
2651 things; you can control whether or not you need to confirm by using the
2652 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2656 @section Killing the Child Process
2661 Kill the child process in which your program is running under @value{GDBN}.
2664 This command is useful if you wish to debug a core dump instead of a
2665 running process. @value{GDBN} ignores any core dump file while your program
2668 On some operating systems, a program cannot be executed outside @value{GDBN}
2669 while you have breakpoints set on it inside @value{GDBN}. You can use the
2670 @code{kill} command in this situation to permit running your program
2671 outside the debugger.
2673 The @code{kill} command is also useful if you wish to recompile and
2674 relink your program, since on many systems it is impossible to modify an
2675 executable file while it is running in a process. In this case, when you
2676 next type @code{run}, @value{GDBN} notices that the file has changed, and
2677 reads the symbol table again (while trying to preserve your current
2678 breakpoint settings).
2680 @node Inferiors and Programs
2681 @section Debugging Multiple Inferiors and Programs
2683 @value{GDBN} lets you run and debug multiple programs in a single
2684 session. In addition, @value{GDBN} on some systems may let you run
2685 several programs simultaneously (otherwise you have to exit from one
2686 before starting another). In the most general case, you can have
2687 multiple threads of execution in each of multiple processes, launched
2688 from multiple executables.
2691 @value{GDBN} represents the state of each program execution with an
2692 object called an @dfn{inferior}. An inferior typically corresponds to
2693 a process, but is more general and applies also to targets that do not
2694 have processes. Inferiors may be created before a process runs, and
2695 may be retained after a process exits. Inferiors have unique
2696 identifiers that are different from process ids. Usually each
2697 inferior will also have its own distinct address space, although some
2698 embedded targets may have several inferiors running in different parts
2699 of a single address space. Each inferior may in turn have multiple
2700 threads running in it.
2702 To find out what inferiors exist at any moment, use @w{@code{info
2706 @kindex info inferiors
2707 @item info inferiors
2708 Print a list of all inferiors currently being managed by @value{GDBN}.
2710 @value{GDBN} displays for each inferior (in this order):
2714 the inferior number assigned by @value{GDBN}
2717 the target system's inferior identifier
2720 the name of the executable the inferior is running.
2725 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2726 indicates the current inferior.
2730 @c end table here to get a little more width for example
2733 (@value{GDBP}) info inferiors
2734 Num Description Executable
2735 2 process 2307 hello
2736 * 1 process 3401 goodbye
2739 To switch focus between inferiors, use the @code{inferior} command:
2742 @kindex inferior @var{infno}
2743 @item inferior @var{infno}
2744 Make inferior number @var{infno} the current inferior. The argument
2745 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2746 in the first field of the @samp{info inferiors} display.
2749 @vindex $_inferior@r{, convenience variable}
2750 The debugger convenience variable @samp{$_inferior} contains the
2751 number of the current inferior. You may find this useful in writing
2752 breakpoint conditional expressions, command scripts, and so forth.
2753 @xref{Convenience Vars,, Convenience Variables}, for general
2754 information on convenience variables.
2756 You can get multiple executables into a debugging session via the
2757 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2758 systems @value{GDBN} can add inferiors to the debug session
2759 automatically by following calls to @code{fork} and @code{exec}. To
2760 remove inferiors from the debugging session use the
2761 @w{@code{remove-inferiors}} command.
2764 @kindex add-inferior
2765 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2766 Adds @var{n} inferiors to be run using @var{executable} as the
2767 executable; @var{n} defaults to 1. If no executable is specified,
2768 the inferiors begins empty, with no program. You can still assign or
2769 change the program assigned to the inferior at any time by using the
2770 @code{file} command with the executable name as its argument.
2772 @kindex clone-inferior
2773 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2774 Adds @var{n} inferiors ready to execute the same program as inferior
2775 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2776 number of the current inferior. This is a convenient command when you
2777 want to run another instance of the inferior you are debugging.
2780 (@value{GDBP}) info inferiors
2781 Num Description Executable
2782 * 1 process 29964 helloworld
2783 (@value{GDBP}) clone-inferior
2786 (@value{GDBP}) info inferiors
2787 Num Description Executable
2789 * 1 process 29964 helloworld
2792 You can now simply switch focus to inferior 2 and run it.
2794 @kindex remove-inferiors
2795 @item remove-inferiors @var{infno}@dots{}
2796 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2797 possible to remove an inferior that is running with this command. For
2798 those, use the @code{kill} or @code{detach} command first.
2802 To quit debugging one of the running inferiors that is not the current
2803 inferior, you can either detach from it by using the @w{@code{detach
2804 inferior}} command (allowing it to run independently), or kill it
2805 using the @w{@code{kill inferiors}} command:
2808 @kindex detach inferiors @var{infno}@dots{}
2809 @item detach inferior @var{infno}@dots{}
2810 Detach from the inferior or inferiors identified by @value{GDBN}
2811 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2812 still stays on the list of inferiors shown by @code{info inferiors},
2813 but its Description will show @samp{<null>}.
2815 @kindex kill inferiors @var{infno}@dots{}
2816 @item kill inferiors @var{infno}@dots{}
2817 Kill the inferior or inferiors identified by @value{GDBN} inferior
2818 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2819 stays on the list of inferiors shown by @code{info inferiors}, but its
2820 Description will show @samp{<null>}.
2823 After the successful completion of a command such as @code{detach},
2824 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2825 a normal process exit, the inferior is still valid and listed with
2826 @code{info inferiors}, ready to be restarted.
2829 To be notified when inferiors are started or exit under @value{GDBN}'s
2830 control use @w{@code{set print inferior-events}}:
2833 @kindex set print inferior-events
2834 @cindex print messages on inferior start and exit
2835 @item set print inferior-events
2836 @itemx set print inferior-events on
2837 @itemx set print inferior-events off
2838 The @code{set print inferior-events} command allows you to enable or
2839 disable printing of messages when @value{GDBN} notices that new
2840 inferiors have started or that inferiors have exited or have been
2841 detached. By default, these messages will not be printed.
2843 @kindex show print inferior-events
2844 @item show print inferior-events
2845 Show whether messages will be printed when @value{GDBN} detects that
2846 inferiors have started, exited or have been detached.
2849 Many commands will work the same with multiple programs as with a
2850 single program: e.g., @code{print myglobal} will simply display the
2851 value of @code{myglobal} in the current inferior.
2854 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2855 get more info about the relationship of inferiors, programs, address
2856 spaces in a debug session. You can do that with the @w{@code{maint
2857 info program-spaces}} command.
2860 @kindex maint info program-spaces
2861 @item maint info program-spaces
2862 Print a list of all program spaces currently being managed by
2865 @value{GDBN} displays for each program space (in this order):
2869 the program space number assigned by @value{GDBN}
2872 the name of the executable loaded into the program space, with e.g.,
2873 the @code{file} command.
2878 An asterisk @samp{*} preceding the @value{GDBN} program space number
2879 indicates the current program space.
2881 In addition, below each program space line, @value{GDBN} prints extra
2882 information that isn't suitable to display in tabular form. For
2883 example, the list of inferiors bound to the program space.
2886 (@value{GDBP}) maint info program-spaces
2890 Bound inferiors: ID 1 (process 21561)
2893 Here we can see that no inferior is running the program @code{hello},
2894 while @code{process 21561} is running the program @code{goodbye}. On
2895 some targets, it is possible that multiple inferiors are bound to the
2896 same program space. The most common example is that of debugging both
2897 the parent and child processes of a @code{vfork} call. For example,
2900 (@value{GDBP}) maint info program-spaces
2903 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2906 Here, both inferior 2 and inferior 1 are running in the same program
2907 space as a result of inferior 1 having executed a @code{vfork} call.
2911 @section Debugging Programs with Multiple Threads
2913 @cindex threads of execution
2914 @cindex multiple threads
2915 @cindex switching threads
2916 In some operating systems, such as GNU/Linux and Solaris, a single program
2917 may have more than one @dfn{thread} of execution. The precise semantics
2918 of threads differ from one operating system to another, but in general
2919 the threads of a single program are akin to multiple processes---except
2920 that they share one address space (that is, they can all examine and
2921 modify the same variables). On the other hand, each thread has its own
2922 registers and execution stack, and perhaps private memory.
2924 @value{GDBN} provides these facilities for debugging multi-thread
2928 @item automatic notification of new threads
2929 @item @samp{thread @var{thread-id}}, a command to switch among threads
2930 @item @samp{info threads}, a command to inquire about existing threads
2931 @item @samp{thread apply [@var{thread-id-list}] [@var{all}] @var{args}},
2932 a command to apply a command to a list of threads
2933 @item thread-specific breakpoints
2934 @item @samp{set print thread-events}, which controls printing of
2935 messages on thread start and exit.
2936 @item @samp{set libthread-db-search-path @var{path}}, which lets
2937 the user specify which @code{libthread_db} to use if the default choice
2938 isn't compatible with the program.
2941 @cindex focus of debugging
2942 @cindex current thread
2943 The @value{GDBN} thread debugging facility allows you to observe all
2944 threads while your program runs---but whenever @value{GDBN} takes
2945 control, one thread in particular is always the focus of debugging.
2946 This thread is called the @dfn{current thread}. Debugging commands show
2947 program information from the perspective of the current thread.
2949 @cindex @code{New} @var{systag} message
2950 @cindex thread identifier (system)
2951 @c FIXME-implementors!! It would be more helpful if the [New...] message
2952 @c included GDB's numeric thread handle, so you could just go to that
2953 @c thread without first checking `info threads'.
2954 Whenever @value{GDBN} detects a new thread in your program, it displays
2955 the target system's identification for the thread with a message in the
2956 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2957 whose form varies depending on the particular system. For example, on
2958 @sc{gnu}/Linux, you might see
2961 [New Thread 0x41e02940 (LWP 25582)]
2965 when @value{GDBN} notices a new thread. In contrast, on other systems,
2966 the @var{systag} is simply something like @samp{process 368}, with no
2969 @c FIXME!! (1) Does the [New...] message appear even for the very first
2970 @c thread of a program, or does it only appear for the
2971 @c second---i.e.@: when it becomes obvious we have a multithread
2973 @c (2) *Is* there necessarily a first thread always? Or do some
2974 @c multithread systems permit starting a program with multiple
2975 @c threads ab initio?
2977 @anchor{thread numbers}
2978 @cindex thread number, per inferior
2979 @cindex thread identifier (GDB)
2980 For debugging purposes, @value{GDBN} associates its own thread number
2981 ---always a single integer---with each thread of an inferior. This
2982 number is unique between all threads of an inferior, but not unique
2983 between threads of different inferiors.
2985 @cindex qualified thread ID
2986 You can refer to a given thread in an inferior using the qualified
2987 @var{inferior-num}.@var{thread-num} syntax, also known as
2988 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
2989 number and @var{thread-num} being the thread number of the given
2990 inferior. For example, thread @code{2.3} refers to thread number 3 of
2991 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
2992 then @value{GDBN} infers you're referring to a thread of the current
2995 Until you create a second inferior, @value{GDBN} does not show the
2996 @var{inferior-num} part of thread IDs, even though you can always use
2997 the full @var{inferior-num}.@var{thread-num} form to refer to threads
2998 of inferior 1, the initial inferior.
3000 @anchor{thread ID lists}
3001 @cindex thread ID lists
3002 Some commands accept a space-separated @dfn{thread ID list} as
3003 argument. A list element can be:
3007 A thread ID as shown in the first field of the @samp{info threads}
3008 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3012 A range of thread numbers, again with or without an inferior
3013 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3014 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3017 All threads of an inferior, specified with a star wildcard, with or
3018 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3019 @samp{1.*}) or @code{*}. The former refers to all threads of the
3020 given inferior, and the latter form without an inferior qualifier
3021 refers to all threads of the current inferior.
3025 For example, if the current inferior is 1, and inferior 7 has one
3026 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3027 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3028 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3029 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3033 @anchor{global thread numbers}
3034 @cindex global thread number
3035 @cindex global thread identifier (GDB)
3036 In addition to a @emph{per-inferior} number, each thread is also
3037 assigned a unique @emph{global} number, also known as @dfn{global
3038 thread ID}, a single integer. Unlike the thread number component of
3039 the thread ID, no two threads have the same global ID, even when
3040 you're debugging multiple inferiors.
3042 From @value{GDBN}'s perspective, a process always has at least one
3043 thread. In other words, @value{GDBN} assigns a thread number to the
3044 program's ``main thread'' even if the program is not multi-threaded.
3046 @vindex $_thread@r{, convenience variable}
3047 @vindex $_gthread@r{, convenience variable}
3048 The debugger convenience variables @samp{$_thread} and
3049 @samp{$_gthread} contain, respectively, the per-inferior thread number
3050 and the global thread number of the current thread. You may find this
3051 useful in writing breakpoint conditional expressions, command scripts,
3052 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3053 general information on convenience variables.
3055 If @value{GDBN} detects the program is multi-threaded, it augments the
3056 usual message about stopping at a breakpoint with the ID and name of
3057 the thread that hit the breakpoint.
3060 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3063 Likewise when the program receives a signal:
3066 Thread 1 "main" received signal SIGINT, Interrupt.
3070 @kindex info threads
3071 @item info threads @r{[}@var{thread-id-list}@r{]}
3073 Display information about one or more threads. With no arguments
3074 displays information about all threads. You can specify the list of
3075 threads that you want to display using the thread ID list syntax
3076 (@pxref{thread ID lists}).
3078 @value{GDBN} displays for each thread (in this order):
3082 the per-inferior thread number assigned by @value{GDBN}
3085 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3086 option was specified
3089 the target system's thread identifier (@var{systag})
3092 the thread's name, if one is known. A thread can either be named by
3093 the user (see @code{thread name}, below), or, in some cases, by the
3097 the current stack frame summary for that thread
3101 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3102 indicates the current thread.
3106 @c end table here to get a little more width for example
3109 (@value{GDBP}) info threads
3111 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3112 2 process 35 thread 23 0x34e5 in sigpause ()
3113 3 process 35 thread 27 0x34e5 in sigpause ()
3117 If you're debugging multiple inferiors, @value{GDBN} displays thread
3118 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3119 Otherwise, only @var{thread-num} is shown.
3121 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3122 indicating each thread's global thread ID:
3125 (@value{GDBP}) info threads
3126 Id GId Target Id Frame
3127 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3128 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3129 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3130 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3133 On Solaris, you can display more information about user threads with a
3134 Solaris-specific command:
3137 @item maint info sol-threads
3138 @kindex maint info sol-threads
3139 @cindex thread info (Solaris)
3140 Display info on Solaris user threads.
3144 @kindex thread @var{thread-id}
3145 @item thread @var{thread-id}
3146 Make thread ID @var{thread-id} the current thread. The command
3147 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3148 the first field of the @samp{info threads} display, with or without an
3149 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3151 @value{GDBN} responds by displaying the system identifier of the
3152 thread you selected, and its current stack frame summary:
3155 (@value{GDBP}) thread 2
3156 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3157 #0 some_function (ignore=0x0) at example.c:8
3158 8 printf ("hello\n");
3162 As with the @samp{[New @dots{}]} message, the form of the text after
3163 @samp{Switching to} depends on your system's conventions for identifying
3166 @kindex thread apply
3167 @cindex apply command to several threads
3168 @item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
3169 The @code{thread apply} command allows you to apply the named
3170 @var{command} to one or more threads. Specify the threads that you
3171 want affected using the thread ID list syntax (@pxref{thread ID
3172 lists}), or specify @code{all} to apply to all threads. To apply a
3173 command to all threads in descending order, type @kbd{thread apply all
3174 @var{command}}. To apply a command to all threads in ascending order,
3175 type @kbd{thread apply all -ascending @var{command}}.
3179 @cindex name a thread
3180 @item thread name [@var{name}]
3181 This command assigns a name to the current thread. If no argument is
3182 given, any existing user-specified name is removed. The thread name
3183 appears in the @samp{info threads} display.
3185 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3186 determine the name of the thread as given by the OS. On these
3187 systems, a name specified with @samp{thread name} will override the
3188 system-give name, and removing the user-specified name will cause
3189 @value{GDBN} to once again display the system-specified name.
3192 @cindex search for a thread
3193 @item thread find [@var{regexp}]
3194 Search for and display thread ids whose name or @var{systag}
3195 matches the supplied regular expression.
3197 As well as being the complement to the @samp{thread name} command,
3198 this command also allows you to identify a thread by its target
3199 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3203 (@value{GDBN}) thread find 26688
3204 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3205 (@value{GDBN}) info thread 4
3207 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3210 @kindex set print thread-events
3211 @cindex print messages on thread start and exit
3212 @item set print thread-events
3213 @itemx set print thread-events on
3214 @itemx set print thread-events off
3215 The @code{set print thread-events} command allows you to enable or
3216 disable printing of messages when @value{GDBN} notices that new threads have
3217 started or that threads have exited. By default, these messages will
3218 be printed if detection of these events is supported by the target.
3219 Note that these messages cannot be disabled on all targets.
3221 @kindex show print thread-events
3222 @item show print thread-events
3223 Show whether messages will be printed when @value{GDBN} detects that threads
3224 have started and exited.
3227 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3228 more information about how @value{GDBN} behaves when you stop and start
3229 programs with multiple threads.
3231 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3232 watchpoints in programs with multiple threads.
3234 @anchor{set libthread-db-search-path}
3236 @kindex set libthread-db-search-path
3237 @cindex search path for @code{libthread_db}
3238 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3239 If this variable is set, @var{path} is a colon-separated list of
3240 directories @value{GDBN} will use to search for @code{libthread_db}.
3241 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3242 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3243 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3246 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3247 @code{libthread_db} library to obtain information about threads in the
3248 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3249 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3250 specific thread debugging library loading is enabled
3251 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3253 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3254 refers to the default system directories that are
3255 normally searched for loading shared libraries. The @samp{$sdir} entry
3256 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3257 (@pxref{libthread_db.so.1 file}).
3259 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3260 refers to the directory from which @code{libpthread}
3261 was loaded in the inferior process.
3263 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3264 @value{GDBN} attempts to initialize it with the current inferior process.
3265 If this initialization fails (which could happen because of a version
3266 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3267 will unload @code{libthread_db}, and continue with the next directory.
3268 If none of @code{libthread_db} libraries initialize successfully,
3269 @value{GDBN} will issue a warning and thread debugging will be disabled.
3271 Setting @code{libthread-db-search-path} is currently implemented
3272 only on some platforms.
3274 @kindex show libthread-db-search-path
3275 @item show libthread-db-search-path
3276 Display current libthread_db search path.
3278 @kindex set debug libthread-db
3279 @kindex show debug libthread-db
3280 @cindex debugging @code{libthread_db}
3281 @item set debug libthread-db
3282 @itemx show debug libthread-db
3283 Turns on or off display of @code{libthread_db}-related events.
3284 Use @code{1} to enable, @code{0} to disable.
3288 @section Debugging Forks
3290 @cindex fork, debugging programs which call
3291 @cindex multiple processes
3292 @cindex processes, multiple
3293 On most systems, @value{GDBN} has no special support for debugging
3294 programs which create additional processes using the @code{fork}
3295 function. When a program forks, @value{GDBN} will continue to debug the
3296 parent process and the child process will run unimpeded. If you have
3297 set a breakpoint in any code which the child then executes, the child
3298 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3299 will cause it to terminate.
3301 However, if you want to debug the child process there is a workaround
3302 which isn't too painful. Put a call to @code{sleep} in the code which
3303 the child process executes after the fork. It may be useful to sleep
3304 only if a certain environment variable is set, or a certain file exists,
3305 so that the delay need not occur when you don't want to run @value{GDBN}
3306 on the child. While the child is sleeping, use the @code{ps} program to
3307 get its process ID. Then tell @value{GDBN} (a new invocation of
3308 @value{GDBN} if you are also debugging the parent process) to attach to
3309 the child process (@pxref{Attach}). From that point on you can debug
3310 the child process just like any other process which you attached to.
3312 On some systems, @value{GDBN} provides support for debugging programs
3313 that create additional processes using the @code{fork} or @code{vfork}
3314 functions. On @sc{gnu}/Linux platforms, this feature is supported
3315 with kernel version 2.5.46 and later.
3317 The fork debugging commands are supported in native mode and when
3318 connected to @code{gdbserver} in either @code{target remote} mode or
3319 @code{target extended-remote} mode.
3321 By default, when a program forks, @value{GDBN} will continue to debug
3322 the parent process and the child process will run unimpeded.
3324 If you want to follow the child process instead of the parent process,
3325 use the command @w{@code{set follow-fork-mode}}.
3328 @kindex set follow-fork-mode
3329 @item set follow-fork-mode @var{mode}
3330 Set the debugger response to a program call of @code{fork} or
3331 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3332 process. The @var{mode} argument can be:
3336 The original process is debugged after a fork. The child process runs
3337 unimpeded. This is the default.
3340 The new process is debugged after a fork. The parent process runs
3345 @kindex show follow-fork-mode
3346 @item show follow-fork-mode
3347 Display the current debugger response to a @code{fork} or @code{vfork} call.
3350 @cindex debugging multiple processes
3351 On Linux, if you want to debug both the parent and child processes, use the
3352 command @w{@code{set detach-on-fork}}.
3355 @kindex set detach-on-fork
3356 @item set detach-on-fork @var{mode}
3357 Tells gdb whether to detach one of the processes after a fork, or
3358 retain debugger control over them both.
3362 The child process (or parent process, depending on the value of
3363 @code{follow-fork-mode}) will be detached and allowed to run
3364 independently. This is the default.
3367 Both processes will be held under the control of @value{GDBN}.
3368 One process (child or parent, depending on the value of
3369 @code{follow-fork-mode}) is debugged as usual, while the other
3374 @kindex show detach-on-fork
3375 @item show detach-on-fork
3376 Show whether detach-on-fork mode is on/off.
3379 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3380 will retain control of all forked processes (including nested forks).
3381 You can list the forked processes under the control of @value{GDBN} by
3382 using the @w{@code{info inferiors}} command, and switch from one fork
3383 to another by using the @code{inferior} command (@pxref{Inferiors and
3384 Programs, ,Debugging Multiple Inferiors and Programs}).
3386 To quit debugging one of the forked processes, you can either detach
3387 from it by using the @w{@code{detach inferiors}} command (allowing it
3388 to run independently), or kill it using the @w{@code{kill inferiors}}
3389 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3392 If you ask to debug a child process and a @code{vfork} is followed by an
3393 @code{exec}, @value{GDBN} executes the new target up to the first
3394 breakpoint in the new target. If you have a breakpoint set on
3395 @code{main} in your original program, the breakpoint will also be set on
3396 the child process's @code{main}.
3398 On some systems, when a child process is spawned by @code{vfork}, you
3399 cannot debug the child or parent until an @code{exec} call completes.
3401 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3402 call executes, the new target restarts. To restart the parent
3403 process, use the @code{file} command with the parent executable name
3404 as its argument. By default, after an @code{exec} call executes,
3405 @value{GDBN} discards the symbols of the previous executable image.
3406 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3410 @kindex set follow-exec-mode
3411 @item set follow-exec-mode @var{mode}
3413 Set debugger response to a program call of @code{exec}. An
3414 @code{exec} call replaces the program image of a process.
3416 @code{follow-exec-mode} can be:
3420 @value{GDBN} creates a new inferior and rebinds the process to this
3421 new inferior. The program the process was running before the
3422 @code{exec} call can be restarted afterwards by restarting the
3428 (@value{GDBP}) info inferiors
3430 Id Description Executable
3433 process 12020 is executing new program: prog2
3434 Program exited normally.
3435 (@value{GDBP}) info inferiors
3436 Id Description Executable
3442 @value{GDBN} keeps the process bound to the same inferior. The new
3443 executable image replaces the previous executable loaded in the
3444 inferior. Restarting the inferior after the @code{exec} call, with
3445 e.g., the @code{run} command, restarts the executable the process was
3446 running after the @code{exec} call. This is the default mode.
3451 (@value{GDBP}) info inferiors
3452 Id Description Executable
3455 process 12020 is executing new program: prog2
3456 Program exited normally.
3457 (@value{GDBP}) info inferiors
3458 Id Description Executable
3465 @code{follow-exec-mode} is supported in native mode and
3466 @code{target extended-remote} mode.
3468 You can use the @code{catch} command to make @value{GDBN} stop whenever
3469 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3470 Catchpoints, ,Setting Catchpoints}.
3472 @node Checkpoint/Restart
3473 @section Setting a @emph{Bookmark} to Return to Later
3478 @cindex snapshot of a process
3479 @cindex rewind program state
3481 On certain operating systems@footnote{Currently, only
3482 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3483 program's state, called a @dfn{checkpoint}, and come back to it
3486 Returning to a checkpoint effectively undoes everything that has
3487 happened in the program since the @code{checkpoint} was saved. This
3488 includes changes in memory, registers, and even (within some limits)
3489 system state. Effectively, it is like going back in time to the
3490 moment when the checkpoint was saved.
3492 Thus, if you're stepping thru a program and you think you're
3493 getting close to the point where things go wrong, you can save
3494 a checkpoint. Then, if you accidentally go too far and miss
3495 the critical statement, instead of having to restart your program
3496 from the beginning, you can just go back to the checkpoint and
3497 start again from there.
3499 This can be especially useful if it takes a lot of time or
3500 steps to reach the point where you think the bug occurs.
3502 To use the @code{checkpoint}/@code{restart} method of debugging:
3507 Save a snapshot of the debugged program's current execution state.
3508 The @code{checkpoint} command takes no arguments, but each checkpoint
3509 is assigned a small integer id, similar to a breakpoint id.
3511 @kindex info checkpoints
3512 @item info checkpoints
3513 List the checkpoints that have been saved in the current debugging
3514 session. For each checkpoint, the following information will be
3521 @item Source line, or label
3524 @kindex restart @var{checkpoint-id}
3525 @item restart @var{checkpoint-id}
3526 Restore the program state that was saved as checkpoint number
3527 @var{checkpoint-id}. All program variables, registers, stack frames
3528 etc.@: will be returned to the values that they had when the checkpoint
3529 was saved. In essence, gdb will ``wind back the clock'' to the point
3530 in time when the checkpoint was saved.
3532 Note that breakpoints, @value{GDBN} variables, command history etc.
3533 are not affected by restoring a checkpoint. In general, a checkpoint
3534 only restores things that reside in the program being debugged, not in
3537 @kindex delete checkpoint @var{checkpoint-id}
3538 @item delete checkpoint @var{checkpoint-id}
3539 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3543 Returning to a previously saved checkpoint will restore the user state
3544 of the program being debugged, plus a significant subset of the system
3545 (OS) state, including file pointers. It won't ``un-write'' data from
3546 a file, but it will rewind the file pointer to the previous location,
3547 so that the previously written data can be overwritten. For files
3548 opened in read mode, the pointer will also be restored so that the
3549 previously read data can be read again.
3551 Of course, characters that have been sent to a printer (or other
3552 external device) cannot be ``snatched back'', and characters received
3553 from eg.@: a serial device can be removed from internal program buffers,
3554 but they cannot be ``pushed back'' into the serial pipeline, ready to
3555 be received again. Similarly, the actual contents of files that have
3556 been changed cannot be restored (at this time).
3558 However, within those constraints, you actually can ``rewind'' your
3559 program to a previously saved point in time, and begin debugging it
3560 again --- and you can change the course of events so as to debug a
3561 different execution path this time.
3563 @cindex checkpoints and process id
3564 Finally, there is one bit of internal program state that will be
3565 different when you return to a checkpoint --- the program's process
3566 id. Each checkpoint will have a unique process id (or @var{pid}),
3567 and each will be different from the program's original @var{pid}.
3568 If your program has saved a local copy of its process id, this could
3569 potentially pose a problem.
3571 @subsection A Non-obvious Benefit of Using Checkpoints
3573 On some systems such as @sc{gnu}/Linux, address space randomization
3574 is performed on new processes for security reasons. This makes it
3575 difficult or impossible to set a breakpoint, or watchpoint, on an
3576 absolute address if you have to restart the program, since the
3577 absolute location of a symbol will change from one execution to the
3580 A checkpoint, however, is an @emph{identical} copy of a process.
3581 Therefore if you create a checkpoint at (eg.@:) the start of main,
3582 and simply return to that checkpoint instead of restarting the
3583 process, you can avoid the effects of address randomization and
3584 your symbols will all stay in the same place.
3587 @chapter Stopping and Continuing
3589 The principal purposes of using a debugger are so that you can stop your
3590 program before it terminates; or so that, if your program runs into
3591 trouble, you can investigate and find out why.
3593 Inside @value{GDBN}, your program may stop for any of several reasons,
3594 such as a signal, a breakpoint, or reaching a new line after a
3595 @value{GDBN} command such as @code{step}. You may then examine and
3596 change variables, set new breakpoints or remove old ones, and then
3597 continue execution. Usually, the messages shown by @value{GDBN} provide
3598 ample explanation of the status of your program---but you can also
3599 explicitly request this information at any time.
3602 @kindex info program
3604 Display information about the status of your program: whether it is
3605 running or not, what process it is, and why it stopped.
3609 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3610 * Continuing and Stepping:: Resuming execution
3611 * Skipping Over Functions and Files::
3612 Skipping over functions and files
3614 * Thread Stops:: Stopping and starting multi-thread programs
3618 @section Breakpoints, Watchpoints, and Catchpoints
3621 A @dfn{breakpoint} makes your program stop whenever a certain point in
3622 the program is reached. For each breakpoint, you can add conditions to
3623 control in finer detail whether your program stops. You can set
3624 breakpoints with the @code{break} command and its variants (@pxref{Set
3625 Breaks, ,Setting Breakpoints}), to specify the place where your program
3626 should stop by line number, function name or exact address in the
3629 On some systems, you can set breakpoints in shared libraries before
3630 the executable is run.
3633 @cindex data breakpoints
3634 @cindex memory tracing
3635 @cindex breakpoint on memory address
3636 @cindex breakpoint on variable modification
3637 A @dfn{watchpoint} is a special breakpoint that stops your program
3638 when the value of an expression changes. The expression may be a value
3639 of a variable, or it could involve values of one or more variables
3640 combined by operators, such as @samp{a + b}. This is sometimes called
3641 @dfn{data breakpoints}. You must use a different command to set
3642 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3643 from that, you can manage a watchpoint like any other breakpoint: you
3644 enable, disable, and delete both breakpoints and watchpoints using the
3647 You can arrange to have values from your program displayed automatically
3648 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3652 @cindex breakpoint on events
3653 A @dfn{catchpoint} is another special breakpoint that stops your program
3654 when a certain kind of event occurs, such as the throwing of a C@t{++}
3655 exception or the loading of a library. As with watchpoints, you use a
3656 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3657 Catchpoints}), but aside from that, you can manage a catchpoint like any
3658 other breakpoint. (To stop when your program receives a signal, use the
3659 @code{handle} command; see @ref{Signals, ,Signals}.)
3661 @cindex breakpoint numbers
3662 @cindex numbers for breakpoints
3663 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3664 catchpoint when you create it; these numbers are successive integers
3665 starting with one. In many of the commands for controlling various
3666 features of breakpoints you use the breakpoint number to say which
3667 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3668 @dfn{disabled}; if disabled, it has no effect on your program until you
3671 @cindex breakpoint ranges
3672 @cindex breakpoint lists
3673 @cindex ranges of breakpoints
3674 @cindex lists of breakpoints
3675 Some @value{GDBN} commands accept a space-separated list of breakpoints
3676 on which to operate. A list element can be either a single breakpoint number,
3677 like @samp{5}, or a range of such numbers, like @samp{5-7}.
3678 When a breakpoint list is given to a command, all breakpoints in that list
3682 * Set Breaks:: Setting breakpoints
3683 * Set Watchpoints:: Setting watchpoints
3684 * Set Catchpoints:: Setting catchpoints
3685 * Delete Breaks:: Deleting breakpoints
3686 * Disabling:: Disabling breakpoints
3687 * Conditions:: Break conditions
3688 * Break Commands:: Breakpoint command lists
3689 * Dynamic Printf:: Dynamic printf
3690 * Save Breakpoints:: How to save breakpoints in a file
3691 * Static Probe Points:: Listing static probe points
3692 * Error in Breakpoints:: ``Cannot insert breakpoints''
3693 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3697 @subsection Setting Breakpoints
3699 @c FIXME LMB what does GDB do if no code on line of breakpt?
3700 @c consider in particular declaration with/without initialization.
3702 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3705 @kindex b @r{(@code{break})}
3706 @vindex $bpnum@r{, convenience variable}
3707 @cindex latest breakpoint
3708 Breakpoints are set with the @code{break} command (abbreviated
3709 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3710 number of the breakpoint you've set most recently; see @ref{Convenience
3711 Vars,, Convenience Variables}, for a discussion of what you can do with
3712 convenience variables.
3715 @item break @var{location}
3716 Set a breakpoint at the given @var{location}, which can specify a
3717 function name, a line number, or an address of an instruction.
3718 (@xref{Specify Location}, for a list of all the possible ways to
3719 specify a @var{location}.) The breakpoint will stop your program just
3720 before it executes any of the code in the specified @var{location}.
3722 When using source languages that permit overloading of symbols, such as
3723 C@t{++}, a function name may refer to more than one possible place to break.
3724 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3727 It is also possible to insert a breakpoint that will stop the program
3728 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3729 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3732 When called without any arguments, @code{break} sets a breakpoint at
3733 the next instruction to be executed in the selected stack frame
3734 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3735 innermost, this makes your program stop as soon as control
3736 returns to that frame. This is similar to the effect of a
3737 @code{finish} command in the frame inside the selected frame---except
3738 that @code{finish} does not leave an active breakpoint. If you use
3739 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3740 the next time it reaches the current location; this may be useful
3743 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3744 least one instruction has been executed. If it did not do this, you
3745 would be unable to proceed past a breakpoint without first disabling the
3746 breakpoint. This rule applies whether or not the breakpoint already
3747 existed when your program stopped.
3749 @item break @dots{} if @var{cond}
3750 Set a breakpoint with condition @var{cond}; evaluate the expression
3751 @var{cond} each time the breakpoint is reached, and stop only if the
3752 value is nonzero---that is, if @var{cond} evaluates as true.
3753 @samp{@dots{}} stands for one of the possible arguments described
3754 above (or no argument) specifying where to break. @xref{Conditions,
3755 ,Break Conditions}, for more information on breakpoint conditions.
3758 @item tbreak @var{args}
3759 Set a breakpoint enabled only for one stop. The @var{args} are the
3760 same as for the @code{break} command, and the breakpoint is set in the same
3761 way, but the breakpoint is automatically deleted after the first time your
3762 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3765 @cindex hardware breakpoints
3766 @item hbreak @var{args}
3767 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3768 @code{break} command and the breakpoint is set in the same way, but the
3769 breakpoint requires hardware support and some target hardware may not
3770 have this support. The main purpose of this is EPROM/ROM code
3771 debugging, so you can set a breakpoint at an instruction without
3772 changing the instruction. This can be used with the new trap-generation
3773 provided by SPARClite DSU and most x86-based targets. These targets
3774 will generate traps when a program accesses some data or instruction
3775 address that is assigned to the debug registers. However the hardware
3776 breakpoint registers can take a limited number of breakpoints. For
3777 example, on the DSU, only two data breakpoints can be set at a time, and
3778 @value{GDBN} will reject this command if more than two are used. Delete
3779 or disable unused hardware breakpoints before setting new ones
3780 (@pxref{Disabling, ,Disabling Breakpoints}).
3781 @xref{Conditions, ,Break Conditions}.
3782 For remote targets, you can restrict the number of hardware
3783 breakpoints @value{GDBN} will use, see @ref{set remote
3784 hardware-breakpoint-limit}.
3787 @item thbreak @var{args}
3788 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3789 are the same as for the @code{hbreak} command and the breakpoint is set in
3790 the same way. However, like the @code{tbreak} command,
3791 the breakpoint is automatically deleted after the
3792 first time your program stops there. Also, like the @code{hbreak}
3793 command, the breakpoint requires hardware support and some target hardware
3794 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3795 See also @ref{Conditions, ,Break Conditions}.
3798 @cindex regular expression
3799 @cindex breakpoints at functions matching a regexp
3800 @cindex set breakpoints in many functions
3801 @item rbreak @var{regex}
3802 Set breakpoints on all functions matching the regular expression
3803 @var{regex}. This command sets an unconditional breakpoint on all
3804 matches, printing a list of all breakpoints it set. Once these
3805 breakpoints are set, they are treated just like the breakpoints set with
3806 the @code{break} command. You can delete them, disable them, or make
3807 them conditional the same way as any other breakpoint.
3809 The syntax of the regular expression is the standard one used with tools
3810 like @file{grep}. Note that this is different from the syntax used by
3811 shells, so for instance @code{foo*} matches all functions that include
3812 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3813 @code{.*} leading and trailing the regular expression you supply, so to
3814 match only functions that begin with @code{foo}, use @code{^foo}.
3816 @cindex non-member C@t{++} functions, set breakpoint in
3817 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3818 breakpoints on overloaded functions that are not members of any special
3821 @cindex set breakpoints on all functions
3822 The @code{rbreak} command can be used to set breakpoints in
3823 @strong{all} the functions in a program, like this:
3826 (@value{GDBP}) rbreak .
3829 @item rbreak @var{file}:@var{regex}
3830 If @code{rbreak} is called with a filename qualification, it limits
3831 the search for functions matching the given regular expression to the
3832 specified @var{file}. This can be used, for example, to set breakpoints on
3833 every function in a given file:
3836 (@value{GDBP}) rbreak file.c:.
3839 The colon separating the filename qualifier from the regex may
3840 optionally be surrounded by spaces.
3842 @kindex info breakpoints
3843 @cindex @code{$_} and @code{info breakpoints}
3844 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3845 @itemx info break @r{[}@var{list}@dots{}@r{]}
3846 Print a table of all breakpoints, watchpoints, and catchpoints set and
3847 not deleted. Optional argument @var{n} means print information only
3848 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3849 For each breakpoint, following columns are printed:
3852 @item Breakpoint Numbers
3854 Breakpoint, watchpoint, or catchpoint.
3856 Whether the breakpoint is marked to be disabled or deleted when hit.
3857 @item Enabled or Disabled
3858 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3859 that are not enabled.
3861 Where the breakpoint is in your program, as a memory address. For a
3862 pending breakpoint whose address is not yet known, this field will
3863 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3864 library that has the symbol or line referred by breakpoint is loaded.
3865 See below for details. A breakpoint with several locations will
3866 have @samp{<MULTIPLE>} in this field---see below for details.
3868 Where the breakpoint is in the source for your program, as a file and
3869 line number. For a pending breakpoint, the original string passed to
3870 the breakpoint command will be listed as it cannot be resolved until
3871 the appropriate shared library is loaded in the future.
3875 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3876 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3877 @value{GDBN} on the host's side. If it is ``target'', then the condition
3878 is evaluated by the target. The @code{info break} command shows
3879 the condition on the line following the affected breakpoint, together with
3880 its condition evaluation mode in between parentheses.
3882 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3883 allowed to have a condition specified for it. The condition is not parsed for
3884 validity until a shared library is loaded that allows the pending
3885 breakpoint to resolve to a valid location.
3888 @code{info break} with a breakpoint
3889 number @var{n} as argument lists only that breakpoint. The
3890 convenience variable @code{$_} and the default examining-address for
3891 the @code{x} command are set to the address of the last breakpoint
3892 listed (@pxref{Memory, ,Examining Memory}).
3895 @code{info break} displays a count of the number of times the breakpoint
3896 has been hit. This is especially useful in conjunction with the
3897 @code{ignore} command. You can ignore a large number of breakpoint
3898 hits, look at the breakpoint info to see how many times the breakpoint
3899 was hit, and then run again, ignoring one less than that number. This
3900 will get you quickly to the last hit of that breakpoint.
3903 For a breakpoints with an enable count (xref) greater than 1,
3904 @code{info break} also displays that count.
3908 @value{GDBN} allows you to set any number of breakpoints at the same place in
3909 your program. There is nothing silly or meaningless about this. When
3910 the breakpoints are conditional, this is even useful
3911 (@pxref{Conditions, ,Break Conditions}).
3913 @cindex multiple locations, breakpoints
3914 @cindex breakpoints, multiple locations
3915 It is possible that a breakpoint corresponds to several locations
3916 in your program. Examples of this situation are:
3920 Multiple functions in the program may have the same name.
3923 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3924 instances of the function body, used in different cases.
3927 For a C@t{++} template function, a given line in the function can
3928 correspond to any number of instantiations.
3931 For an inlined function, a given source line can correspond to
3932 several places where that function is inlined.
3935 In all those cases, @value{GDBN} will insert a breakpoint at all
3936 the relevant locations.
3938 A breakpoint with multiple locations is displayed in the breakpoint
3939 table using several rows---one header row, followed by one row for
3940 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3941 address column. The rows for individual locations contain the actual
3942 addresses for locations, and show the functions to which those
3943 locations belong. The number column for a location is of the form
3944 @var{breakpoint-number}.@var{location-number}.
3949 Num Type Disp Enb Address What
3950 1 breakpoint keep y <MULTIPLE>
3952 breakpoint already hit 1 time
3953 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3954 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3957 You cannot delete the individual locations from a breakpoint. However,
3958 each location can be individually enabled or disabled by passing
3959 @var{breakpoint-number}.@var{location-number} as argument to the
3960 @code{enable} and @code{disable} commands. It's also possible to
3961 @code{enable} and @code{disable} a range of @var{location-number}
3962 locations using a @var{breakpoint-number} and two @var{location-number}s,
3963 in increasing order, separated by a hyphen, like
3964 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
3965 in which case @value{GDBN} acts on all the locations in the range (inclusive).
3966 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
3967 all of the locations that belong to that breakpoint.
3969 @cindex pending breakpoints
3970 It's quite common to have a breakpoint inside a shared library.
3971 Shared libraries can be loaded and unloaded explicitly,
3972 and possibly repeatedly, as the program is executed. To support
3973 this use case, @value{GDBN} updates breakpoint locations whenever
3974 any shared library is loaded or unloaded. Typically, you would
3975 set a breakpoint in a shared library at the beginning of your
3976 debugging session, when the library is not loaded, and when the
3977 symbols from the library are not available. When you try to set
3978 breakpoint, @value{GDBN} will ask you if you want to set
3979 a so called @dfn{pending breakpoint}---breakpoint whose address
3980 is not yet resolved.
3982 After the program is run, whenever a new shared library is loaded,
3983 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3984 shared library contains the symbol or line referred to by some
3985 pending breakpoint, that breakpoint is resolved and becomes an
3986 ordinary breakpoint. When a library is unloaded, all breakpoints
3987 that refer to its symbols or source lines become pending again.
3989 This logic works for breakpoints with multiple locations, too. For
3990 example, if you have a breakpoint in a C@t{++} template function, and
3991 a newly loaded shared library has an instantiation of that template,
3992 a new location is added to the list of locations for the breakpoint.
3994 Except for having unresolved address, pending breakpoints do not
3995 differ from regular breakpoints. You can set conditions or commands,
3996 enable and disable them and perform other breakpoint operations.
3998 @value{GDBN} provides some additional commands for controlling what
3999 happens when the @samp{break} command cannot resolve breakpoint
4000 address specification to an address:
4002 @kindex set breakpoint pending
4003 @kindex show breakpoint pending
4005 @item set breakpoint pending auto
4006 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4007 location, it queries you whether a pending breakpoint should be created.
4009 @item set breakpoint pending on
4010 This indicates that an unrecognized breakpoint location should automatically
4011 result in a pending breakpoint being created.
4013 @item set breakpoint pending off
4014 This indicates that pending breakpoints are not to be created. Any
4015 unrecognized breakpoint location results in an error. This setting does
4016 not affect any pending breakpoints previously created.
4018 @item show breakpoint pending
4019 Show the current behavior setting for creating pending breakpoints.
4022 The settings above only affect the @code{break} command and its
4023 variants. Once breakpoint is set, it will be automatically updated
4024 as shared libraries are loaded and unloaded.
4026 @cindex automatic hardware breakpoints
4027 For some targets, @value{GDBN} can automatically decide if hardware or
4028 software breakpoints should be used, depending on whether the
4029 breakpoint address is read-only or read-write. This applies to
4030 breakpoints set with the @code{break} command as well as to internal
4031 breakpoints set by commands like @code{next} and @code{finish}. For
4032 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4035 You can control this automatic behaviour with the following commands:
4037 @kindex set breakpoint auto-hw
4038 @kindex show breakpoint auto-hw
4040 @item set breakpoint auto-hw on
4041 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4042 will try to use the target memory map to decide if software or hardware
4043 breakpoint must be used.
4045 @item set breakpoint auto-hw off
4046 This indicates @value{GDBN} should not automatically select breakpoint
4047 type. If the target provides a memory map, @value{GDBN} will warn when
4048 trying to set software breakpoint at a read-only address.
4051 @value{GDBN} normally implements breakpoints by replacing the program code
4052 at the breakpoint address with a special instruction, which, when
4053 executed, given control to the debugger. By default, the program
4054 code is so modified only when the program is resumed. As soon as
4055 the program stops, @value{GDBN} restores the original instructions. This
4056 behaviour guards against leaving breakpoints inserted in the
4057 target should gdb abrubptly disconnect. However, with slow remote
4058 targets, inserting and removing breakpoint can reduce the performance.
4059 This behavior can be controlled with the following commands::
4061 @kindex set breakpoint always-inserted
4062 @kindex show breakpoint always-inserted
4064 @item set breakpoint always-inserted off
4065 All breakpoints, including newly added by the user, are inserted in
4066 the target only when the target is resumed. All breakpoints are
4067 removed from the target when it stops. This is the default mode.
4069 @item set breakpoint always-inserted on
4070 Causes all breakpoints to be inserted in the target at all times. If
4071 the user adds a new breakpoint, or changes an existing breakpoint, the
4072 breakpoints in the target are updated immediately. A breakpoint is
4073 removed from the target only when breakpoint itself is deleted.
4076 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4077 when a breakpoint breaks. If the condition is true, then the process being
4078 debugged stops, otherwise the process is resumed.
4080 If the target supports evaluating conditions on its end, @value{GDBN} may
4081 download the breakpoint, together with its conditions, to it.
4083 This feature can be controlled via the following commands:
4085 @kindex set breakpoint condition-evaluation
4086 @kindex show breakpoint condition-evaluation
4088 @item set breakpoint condition-evaluation host
4089 This option commands @value{GDBN} to evaluate the breakpoint
4090 conditions on the host's side. Unconditional breakpoints are sent to
4091 the target which in turn receives the triggers and reports them back to GDB
4092 for condition evaluation. This is the standard evaluation mode.
4094 @item set breakpoint condition-evaluation target
4095 This option commands @value{GDBN} to download breakpoint conditions
4096 to the target at the moment of their insertion. The target
4097 is responsible for evaluating the conditional expression and reporting
4098 breakpoint stop events back to @value{GDBN} whenever the condition
4099 is true. Due to limitations of target-side evaluation, some conditions
4100 cannot be evaluated there, e.g., conditions that depend on local data
4101 that is only known to the host. Examples include
4102 conditional expressions involving convenience variables, complex types
4103 that cannot be handled by the agent expression parser and expressions
4104 that are too long to be sent over to the target, specially when the
4105 target is a remote system. In these cases, the conditions will be
4106 evaluated by @value{GDBN}.
4108 @item set breakpoint condition-evaluation auto
4109 This is the default mode. If the target supports evaluating breakpoint
4110 conditions on its end, @value{GDBN} will download breakpoint conditions to
4111 the target (limitations mentioned previously apply). If the target does
4112 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4113 to evaluating all these conditions on the host's side.
4117 @cindex negative breakpoint numbers
4118 @cindex internal @value{GDBN} breakpoints
4119 @value{GDBN} itself sometimes sets breakpoints in your program for
4120 special purposes, such as proper handling of @code{longjmp} (in C
4121 programs). These internal breakpoints are assigned negative numbers,
4122 starting with @code{-1}; @samp{info breakpoints} does not display them.
4123 You can see these breakpoints with the @value{GDBN} maintenance command
4124 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4127 @node Set Watchpoints
4128 @subsection Setting Watchpoints
4130 @cindex setting watchpoints
4131 You can use a watchpoint to stop execution whenever the value of an
4132 expression changes, without having to predict a particular place where
4133 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4134 The expression may be as simple as the value of a single variable, or
4135 as complex as many variables combined by operators. Examples include:
4139 A reference to the value of a single variable.
4142 An address cast to an appropriate data type. For example,
4143 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4144 address (assuming an @code{int} occupies 4 bytes).
4147 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4148 expression can use any operators valid in the program's native
4149 language (@pxref{Languages}).
4152 You can set a watchpoint on an expression even if the expression can
4153 not be evaluated yet. For instance, you can set a watchpoint on
4154 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4155 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4156 the expression produces a valid value. If the expression becomes
4157 valid in some other way than changing a variable (e.g.@: if the memory
4158 pointed to by @samp{*global_ptr} becomes readable as the result of a
4159 @code{malloc} call), @value{GDBN} may not stop until the next time
4160 the expression changes.
4162 @cindex software watchpoints
4163 @cindex hardware watchpoints
4164 Depending on your system, watchpoints may be implemented in software or
4165 hardware. @value{GDBN} does software watchpointing by single-stepping your
4166 program and testing the variable's value each time, which is hundreds of
4167 times slower than normal execution. (But this may still be worth it, to
4168 catch errors where you have no clue what part of your program is the
4171 On some systems, such as most PowerPC or x86-based targets,
4172 @value{GDBN} includes support for hardware watchpoints, which do not
4173 slow down the running of your program.
4177 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4178 Set a watchpoint for an expression. @value{GDBN} will break when the
4179 expression @var{expr} is written into by the program and its value
4180 changes. The simplest (and the most popular) use of this command is
4181 to watch the value of a single variable:
4184 (@value{GDBP}) watch foo
4187 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4188 argument, @value{GDBN} breaks only when the thread identified by
4189 @var{thread-id} changes the value of @var{expr}. If any other threads
4190 change the value of @var{expr}, @value{GDBN} will not break. Note
4191 that watchpoints restricted to a single thread in this way only work
4192 with Hardware Watchpoints.
4194 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4195 (see below). The @code{-location} argument tells @value{GDBN} to
4196 instead watch the memory referred to by @var{expr}. In this case,
4197 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4198 and watch the memory at that address. The type of the result is used
4199 to determine the size of the watched memory. If the expression's
4200 result does not have an address, then @value{GDBN} will print an
4203 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4204 of masked watchpoints, if the current architecture supports this
4205 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4206 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4207 to an address to watch. The mask specifies that some bits of an address
4208 (the bits which are reset in the mask) should be ignored when matching
4209 the address accessed by the inferior against the watchpoint address.
4210 Thus, a masked watchpoint watches many addresses simultaneously---those
4211 addresses whose unmasked bits are identical to the unmasked bits in the
4212 watchpoint address. The @code{mask} argument implies @code{-location}.
4216 (@value{GDBP}) watch foo mask 0xffff00ff
4217 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4221 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4222 Set a watchpoint that will break when the value of @var{expr} is read
4226 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4227 Set a watchpoint that will break when @var{expr} is either read from
4228 or written into by the program.
4230 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4231 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4232 This command prints a list of watchpoints, using the same format as
4233 @code{info break} (@pxref{Set Breaks}).
4236 If you watch for a change in a numerically entered address you need to
4237 dereference it, as the address itself is just a constant number which will
4238 never change. @value{GDBN} refuses to create a watchpoint that watches
4239 a never-changing value:
4242 (@value{GDBP}) watch 0x600850
4243 Cannot watch constant value 0x600850.
4244 (@value{GDBP}) watch *(int *) 0x600850
4245 Watchpoint 1: *(int *) 6293584
4248 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4249 watchpoints execute very quickly, and the debugger reports a change in
4250 value at the exact instruction where the change occurs. If @value{GDBN}
4251 cannot set a hardware watchpoint, it sets a software watchpoint, which
4252 executes more slowly and reports the change in value at the next
4253 @emph{statement}, not the instruction, after the change occurs.
4255 @cindex use only software watchpoints
4256 You can force @value{GDBN} to use only software watchpoints with the
4257 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4258 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4259 the underlying system supports them. (Note that hardware-assisted
4260 watchpoints that were set @emph{before} setting
4261 @code{can-use-hw-watchpoints} to zero will still use the hardware
4262 mechanism of watching expression values.)
4265 @item set can-use-hw-watchpoints
4266 @kindex set can-use-hw-watchpoints
4267 Set whether or not to use hardware watchpoints.
4269 @item show can-use-hw-watchpoints
4270 @kindex show can-use-hw-watchpoints
4271 Show the current mode of using hardware watchpoints.
4274 For remote targets, you can restrict the number of hardware
4275 watchpoints @value{GDBN} will use, see @ref{set remote
4276 hardware-breakpoint-limit}.
4278 When you issue the @code{watch} command, @value{GDBN} reports
4281 Hardware watchpoint @var{num}: @var{expr}
4285 if it was able to set a hardware watchpoint.
4287 Currently, the @code{awatch} and @code{rwatch} commands can only set
4288 hardware watchpoints, because accesses to data that don't change the
4289 value of the watched expression cannot be detected without examining
4290 every instruction as it is being executed, and @value{GDBN} does not do
4291 that currently. If @value{GDBN} finds that it is unable to set a
4292 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4293 will print a message like this:
4296 Expression cannot be implemented with read/access watchpoint.
4299 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4300 data type of the watched expression is wider than what a hardware
4301 watchpoint on the target machine can handle. For example, some systems
4302 can only watch regions that are up to 4 bytes wide; on such systems you
4303 cannot set hardware watchpoints for an expression that yields a
4304 double-precision floating-point number (which is typically 8 bytes
4305 wide). As a work-around, it might be possible to break the large region
4306 into a series of smaller ones and watch them with separate watchpoints.
4308 If you set too many hardware watchpoints, @value{GDBN} might be unable
4309 to insert all of them when you resume the execution of your program.
4310 Since the precise number of active watchpoints is unknown until such
4311 time as the program is about to be resumed, @value{GDBN} might not be
4312 able to warn you about this when you set the watchpoints, and the
4313 warning will be printed only when the program is resumed:
4316 Hardware watchpoint @var{num}: Could not insert watchpoint
4320 If this happens, delete or disable some of the watchpoints.
4322 Watching complex expressions that reference many variables can also
4323 exhaust the resources available for hardware-assisted watchpoints.
4324 That's because @value{GDBN} needs to watch every variable in the
4325 expression with separately allocated resources.
4327 If you call a function interactively using @code{print} or @code{call},
4328 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4329 kind of breakpoint or the call completes.
4331 @value{GDBN} automatically deletes watchpoints that watch local
4332 (automatic) variables, or expressions that involve such variables, when
4333 they go out of scope, that is, when the execution leaves the block in
4334 which these variables were defined. In particular, when the program
4335 being debugged terminates, @emph{all} local variables go out of scope,
4336 and so only watchpoints that watch global variables remain set. If you
4337 rerun the program, you will need to set all such watchpoints again. One
4338 way of doing that would be to set a code breakpoint at the entry to the
4339 @code{main} function and when it breaks, set all the watchpoints.
4341 @cindex watchpoints and threads
4342 @cindex threads and watchpoints
4343 In multi-threaded programs, watchpoints will detect changes to the
4344 watched expression from every thread.
4347 @emph{Warning:} In multi-threaded programs, software watchpoints
4348 have only limited usefulness. If @value{GDBN} creates a software
4349 watchpoint, it can only watch the value of an expression @emph{in a
4350 single thread}. If you are confident that the expression can only
4351 change due to the current thread's activity (and if you are also
4352 confident that no other thread can become current), then you can use
4353 software watchpoints as usual. However, @value{GDBN} may not notice
4354 when a non-current thread's activity changes the expression. (Hardware
4355 watchpoints, in contrast, watch an expression in all threads.)
4358 @xref{set remote hardware-watchpoint-limit}.
4360 @node Set Catchpoints
4361 @subsection Setting Catchpoints
4362 @cindex catchpoints, setting
4363 @cindex exception handlers
4364 @cindex event handling
4366 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4367 kinds of program events, such as C@t{++} exceptions or the loading of a
4368 shared library. Use the @code{catch} command to set a catchpoint.
4372 @item catch @var{event}
4373 Stop when @var{event} occurs. The @var{event} can be any of the following:
4376 @item throw @r{[}@var{regexp}@r{]}
4377 @itemx rethrow @r{[}@var{regexp}@r{]}
4378 @itemx catch @r{[}@var{regexp}@r{]}
4380 @kindex catch rethrow
4382 @cindex stop on C@t{++} exceptions
4383 The throwing, re-throwing, or catching of a C@t{++} exception.
4385 If @var{regexp} is given, then only exceptions whose type matches the
4386 regular expression will be caught.
4388 @vindex $_exception@r{, convenience variable}
4389 The convenience variable @code{$_exception} is available at an
4390 exception-related catchpoint, on some systems. This holds the
4391 exception being thrown.
4393 There are currently some limitations to C@t{++} exception handling in
4398 The support for these commands is system-dependent. Currently, only
4399 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4403 The regular expression feature and the @code{$_exception} convenience
4404 variable rely on the presence of some SDT probes in @code{libstdc++}.
4405 If these probes are not present, then these features cannot be used.
4406 These probes were first available in the GCC 4.8 release, but whether
4407 or not they are available in your GCC also depends on how it was
4411 The @code{$_exception} convenience variable is only valid at the
4412 instruction at which an exception-related catchpoint is set.
4415 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4416 location in the system library which implements runtime exception
4417 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4418 (@pxref{Selection}) to get to your code.
4421 If you call a function interactively, @value{GDBN} normally returns
4422 control to you when the function has finished executing. If the call
4423 raises an exception, however, the call may bypass the mechanism that
4424 returns control to you and cause your program either to abort or to
4425 simply continue running until it hits a breakpoint, catches a signal
4426 that @value{GDBN} is listening for, or exits. This is the case even if
4427 you set a catchpoint for the exception; catchpoints on exceptions are
4428 disabled within interactive calls. @xref{Calling}, for information on
4429 controlling this with @code{set unwind-on-terminating-exception}.
4432 You cannot raise an exception interactively.
4435 You cannot install an exception handler interactively.
4439 @kindex catch exception
4440 @cindex Ada exception catching
4441 @cindex catch Ada exceptions
4442 An Ada exception being raised. If an exception name is specified
4443 at the end of the command (eg @code{catch exception Program_Error}),
4444 the debugger will stop only when this specific exception is raised.
4445 Otherwise, the debugger stops execution when any Ada exception is raised.
4447 When inserting an exception catchpoint on a user-defined exception whose
4448 name is identical to one of the exceptions defined by the language, the
4449 fully qualified name must be used as the exception name. Otherwise,
4450 @value{GDBN} will assume that it should stop on the pre-defined exception
4451 rather than the user-defined one. For instance, assuming an exception
4452 called @code{Constraint_Error} is defined in package @code{Pck}, then
4453 the command to use to catch such exceptions is @kbd{catch exception
4454 Pck.Constraint_Error}.
4456 @item exception unhandled
4457 @kindex catch exception unhandled
4458 An exception that was raised but is not handled by the program.
4461 @kindex catch assert
4462 A failed Ada assertion.
4466 @cindex break on fork/exec
4467 A call to @code{exec}.
4470 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4471 @kindex catch syscall
4472 @cindex break on a system call.
4473 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4474 syscall is a mechanism for application programs to request a service
4475 from the operating system (OS) or one of the OS system services.
4476 @value{GDBN} can catch some or all of the syscalls issued by the
4477 debuggee, and show the related information for each syscall. If no
4478 argument is specified, calls to and returns from all system calls
4481 @var{name} can be any system call name that is valid for the
4482 underlying OS. Just what syscalls are valid depends on the OS. On
4483 GNU and Unix systems, you can find the full list of valid syscall
4484 names on @file{/usr/include/asm/unistd.h}.
4486 @c For MS-Windows, the syscall names and the corresponding numbers
4487 @c can be found, e.g., on this URL:
4488 @c http://www.metasploit.com/users/opcode/syscalls.html
4489 @c but we don't support Windows syscalls yet.
4491 Normally, @value{GDBN} knows in advance which syscalls are valid for
4492 each OS, so you can use the @value{GDBN} command-line completion
4493 facilities (@pxref{Completion,, command completion}) to list the
4496 You may also specify the system call numerically. A syscall's
4497 number is the value passed to the OS's syscall dispatcher to
4498 identify the requested service. When you specify the syscall by its
4499 name, @value{GDBN} uses its database of syscalls to convert the name
4500 into the corresponding numeric code, but using the number directly
4501 may be useful if @value{GDBN}'s database does not have the complete
4502 list of syscalls on your system (e.g., because @value{GDBN} lags
4503 behind the OS upgrades).
4505 You may specify a group of related syscalls to be caught at once using
4506 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4507 instance, on some platforms @value{GDBN} allows you to catch all
4508 network related syscalls, by passing the argument @code{group:network}
4509 to @code{catch syscall}. Note that not all syscall groups are
4510 available in every system. You can use the command completion
4511 facilities (@pxref{Completion,, command completion}) to list the
4512 syscall groups available on your environment.
4514 The example below illustrates how this command works if you don't provide
4518 (@value{GDBP}) catch syscall
4519 Catchpoint 1 (syscall)
4521 Starting program: /tmp/catch-syscall
4523 Catchpoint 1 (call to syscall 'close'), \
4524 0xffffe424 in __kernel_vsyscall ()
4528 Catchpoint 1 (returned from syscall 'close'), \
4529 0xffffe424 in __kernel_vsyscall ()
4533 Here is an example of catching a system call by name:
4536 (@value{GDBP}) catch syscall chroot
4537 Catchpoint 1 (syscall 'chroot' [61])
4539 Starting program: /tmp/catch-syscall
4541 Catchpoint 1 (call to syscall 'chroot'), \
4542 0xffffe424 in __kernel_vsyscall ()
4546 Catchpoint 1 (returned from syscall 'chroot'), \
4547 0xffffe424 in __kernel_vsyscall ()
4551 An example of specifying a system call numerically. In the case
4552 below, the syscall number has a corresponding entry in the XML
4553 file, so @value{GDBN} finds its name and prints it:
4556 (@value{GDBP}) catch syscall 252
4557 Catchpoint 1 (syscall(s) 'exit_group')
4559 Starting program: /tmp/catch-syscall
4561 Catchpoint 1 (call to syscall 'exit_group'), \
4562 0xffffe424 in __kernel_vsyscall ()
4566 Program exited normally.
4570 Here is an example of catching a syscall group:
4573 (@value{GDBP}) catch syscall group:process
4574 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4575 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4576 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4578 Starting program: /tmp/catch-syscall
4580 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4581 from /lib64/ld-linux-x86-64.so.2
4587 However, there can be situations when there is no corresponding name
4588 in XML file for that syscall number. In this case, @value{GDBN} prints
4589 a warning message saying that it was not able to find the syscall name,
4590 but the catchpoint will be set anyway. See the example below:
4593 (@value{GDBP}) catch syscall 764
4594 warning: The number '764' does not represent a known syscall.
4595 Catchpoint 2 (syscall 764)
4599 If you configure @value{GDBN} using the @samp{--without-expat} option,
4600 it will not be able to display syscall names. Also, if your
4601 architecture does not have an XML file describing its system calls,
4602 you will not be able to see the syscall names. It is important to
4603 notice that these two features are used for accessing the syscall
4604 name database. In either case, you will see a warning like this:
4607 (@value{GDBP}) catch syscall
4608 warning: Could not open "syscalls/i386-linux.xml"
4609 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4610 GDB will not be able to display syscall names.
4611 Catchpoint 1 (syscall)
4615 Of course, the file name will change depending on your architecture and system.
4617 Still using the example above, you can also try to catch a syscall by its
4618 number. In this case, you would see something like:
4621 (@value{GDBP}) catch syscall 252
4622 Catchpoint 1 (syscall(s) 252)
4625 Again, in this case @value{GDBN} would not be able to display syscall's names.
4629 A call to @code{fork}.
4633 A call to @code{vfork}.
4635 @item load @r{[}regexp@r{]}
4636 @itemx unload @r{[}regexp@r{]}
4638 @kindex catch unload
4639 The loading or unloading of a shared library. If @var{regexp} is
4640 given, then the catchpoint will stop only if the regular expression
4641 matches one of the affected libraries.
4643 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4644 @kindex catch signal
4645 The delivery of a signal.
4647 With no arguments, this catchpoint will catch any signal that is not
4648 used internally by @value{GDBN}, specifically, all signals except
4649 @samp{SIGTRAP} and @samp{SIGINT}.
4651 With the argument @samp{all}, all signals, including those used by
4652 @value{GDBN}, will be caught. This argument cannot be used with other
4655 Otherwise, the arguments are a list of signal names as given to
4656 @code{handle} (@pxref{Signals}). Only signals specified in this list
4659 One reason that @code{catch signal} can be more useful than
4660 @code{handle} is that you can attach commands and conditions to the
4663 When a signal is caught by a catchpoint, the signal's @code{stop} and
4664 @code{print} settings, as specified by @code{handle}, are ignored.
4665 However, whether the signal is still delivered to the inferior depends
4666 on the @code{pass} setting; this can be changed in the catchpoint's
4671 @item tcatch @var{event}
4673 Set a catchpoint that is enabled only for one stop. The catchpoint is
4674 automatically deleted after the first time the event is caught.
4678 Use the @code{info break} command to list the current catchpoints.
4682 @subsection Deleting Breakpoints
4684 @cindex clearing breakpoints, watchpoints, catchpoints
4685 @cindex deleting breakpoints, watchpoints, catchpoints
4686 It is often necessary to eliminate a breakpoint, watchpoint, or
4687 catchpoint once it has done its job and you no longer want your program
4688 to stop there. This is called @dfn{deleting} the breakpoint. A
4689 breakpoint that has been deleted no longer exists; it is forgotten.
4691 With the @code{clear} command you can delete breakpoints according to
4692 where they are in your program. With the @code{delete} command you can
4693 delete individual breakpoints, watchpoints, or catchpoints by specifying
4694 their breakpoint numbers.
4696 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4697 automatically ignores breakpoints on the first instruction to be executed
4698 when you continue execution without changing the execution address.
4703 Delete any breakpoints at the next instruction to be executed in the
4704 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4705 the innermost frame is selected, this is a good way to delete a
4706 breakpoint where your program just stopped.
4708 @item clear @var{location}
4709 Delete any breakpoints set at the specified @var{location}.
4710 @xref{Specify Location}, for the various forms of @var{location}; the
4711 most useful ones are listed below:
4714 @item clear @var{function}
4715 @itemx clear @var{filename}:@var{function}
4716 Delete any breakpoints set at entry to the named @var{function}.
4718 @item clear @var{linenum}
4719 @itemx clear @var{filename}:@var{linenum}
4720 Delete any breakpoints set at or within the code of the specified
4721 @var{linenum} of the specified @var{filename}.
4724 @cindex delete breakpoints
4726 @kindex d @r{(@code{delete})}
4727 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4728 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4729 list specified as argument. If no argument is specified, delete all
4730 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4731 confirm off}). You can abbreviate this command as @code{d}.
4735 @subsection Disabling Breakpoints
4737 @cindex enable/disable a breakpoint
4738 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4739 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4740 it had been deleted, but remembers the information on the breakpoint so
4741 that you can @dfn{enable} it again later.
4743 You disable and enable breakpoints, watchpoints, and catchpoints with
4744 the @code{enable} and @code{disable} commands, optionally specifying
4745 one or more breakpoint numbers as arguments. Use @code{info break} to
4746 print a list of all breakpoints, watchpoints, and catchpoints if you
4747 do not know which numbers to use.
4749 Disabling and enabling a breakpoint that has multiple locations
4750 affects all of its locations.
4752 A breakpoint, watchpoint, or catchpoint can have any of several
4753 different states of enablement:
4757 Enabled. The breakpoint stops your program. A breakpoint set
4758 with the @code{break} command starts out in this state.
4760 Disabled. The breakpoint has no effect on your program.
4762 Enabled once. The breakpoint stops your program, but then becomes
4765 Enabled for a count. The breakpoint stops your program for the next
4766 N times, then becomes disabled.
4768 Enabled for deletion. The breakpoint stops your program, but
4769 immediately after it does so it is deleted permanently. A breakpoint
4770 set with the @code{tbreak} command starts out in this state.
4773 You can use the following commands to enable or disable breakpoints,
4774 watchpoints, and catchpoints:
4778 @kindex dis @r{(@code{disable})}
4779 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4780 Disable the specified breakpoints---or all breakpoints, if none are
4781 listed. A disabled breakpoint has no effect but is not forgotten. All
4782 options such as ignore-counts, conditions and commands are remembered in
4783 case the breakpoint is enabled again later. You may abbreviate
4784 @code{disable} as @code{dis}.
4787 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4788 Enable the specified breakpoints (or all defined breakpoints). They
4789 become effective once again in stopping your program.
4791 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4792 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4793 of these breakpoints immediately after stopping your program.
4795 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4796 Enable the specified breakpoints temporarily. @value{GDBN} records
4797 @var{count} with each of the specified breakpoints, and decrements a
4798 breakpoint's count when it is hit. When any count reaches 0,
4799 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4800 count (@pxref{Conditions, ,Break Conditions}), that will be
4801 decremented to 0 before @var{count} is affected.
4803 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4804 Enable the specified breakpoints to work once, then die. @value{GDBN}
4805 deletes any of these breakpoints as soon as your program stops there.
4806 Breakpoints set by the @code{tbreak} command start out in this state.
4809 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4810 @c confusing: tbreak is also initially enabled.
4811 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4812 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4813 subsequently, they become disabled or enabled only when you use one of
4814 the commands above. (The command @code{until} can set and delete a
4815 breakpoint of its own, but it does not change the state of your other
4816 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4820 @subsection Break Conditions
4821 @cindex conditional breakpoints
4822 @cindex breakpoint conditions
4824 @c FIXME what is scope of break condition expr? Context where wanted?
4825 @c in particular for a watchpoint?
4826 The simplest sort of breakpoint breaks every time your program reaches a
4827 specified place. You can also specify a @dfn{condition} for a
4828 breakpoint. A condition is just a Boolean expression in your
4829 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4830 a condition evaluates the expression each time your program reaches it,
4831 and your program stops only if the condition is @emph{true}.
4833 This is the converse of using assertions for program validation; in that
4834 situation, you want to stop when the assertion is violated---that is,
4835 when the condition is false. In C, if you want to test an assertion expressed
4836 by the condition @var{assert}, you should set the condition
4837 @samp{! @var{assert}} on the appropriate breakpoint.
4839 Conditions are also accepted for watchpoints; you may not need them,
4840 since a watchpoint is inspecting the value of an expression anyhow---but
4841 it might be simpler, say, to just set a watchpoint on a variable name,
4842 and specify a condition that tests whether the new value is an interesting
4845 Break conditions can have side effects, and may even call functions in
4846 your program. This can be useful, for example, to activate functions
4847 that log program progress, or to use your own print functions to
4848 format special data structures. The effects are completely predictable
4849 unless there is another enabled breakpoint at the same address. (In
4850 that case, @value{GDBN} might see the other breakpoint first and stop your
4851 program without checking the condition of this one.) Note that
4852 breakpoint commands are usually more convenient and flexible than break
4854 purpose of performing side effects when a breakpoint is reached
4855 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4857 Breakpoint conditions can also be evaluated on the target's side if
4858 the target supports it. Instead of evaluating the conditions locally,
4859 @value{GDBN} encodes the expression into an agent expression
4860 (@pxref{Agent Expressions}) suitable for execution on the target,
4861 independently of @value{GDBN}. Global variables become raw memory
4862 locations, locals become stack accesses, and so forth.
4864 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4865 when its condition evaluates to true. This mechanism may provide faster
4866 response times depending on the performance characteristics of the target
4867 since it does not need to keep @value{GDBN} informed about
4868 every breakpoint trigger, even those with false conditions.
4870 Break conditions can be specified when a breakpoint is set, by using
4871 @samp{if} in the arguments to the @code{break} command. @xref{Set
4872 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4873 with the @code{condition} command.
4875 You can also use the @code{if} keyword with the @code{watch} command.
4876 The @code{catch} command does not recognize the @code{if} keyword;
4877 @code{condition} is the only way to impose a further condition on a
4882 @item condition @var{bnum} @var{expression}
4883 Specify @var{expression} as the break condition for breakpoint,
4884 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4885 breakpoint @var{bnum} stops your program only if the value of
4886 @var{expression} is true (nonzero, in C). When you use
4887 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4888 syntactic correctness, and to determine whether symbols in it have
4889 referents in the context of your breakpoint. If @var{expression} uses
4890 symbols not referenced in the context of the breakpoint, @value{GDBN}
4891 prints an error message:
4894 No symbol "foo" in current context.
4899 not actually evaluate @var{expression} at the time the @code{condition}
4900 command (or a command that sets a breakpoint with a condition, like
4901 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4903 @item condition @var{bnum}
4904 Remove the condition from breakpoint number @var{bnum}. It becomes
4905 an ordinary unconditional breakpoint.
4908 @cindex ignore count (of breakpoint)
4909 A special case of a breakpoint condition is to stop only when the
4910 breakpoint has been reached a certain number of times. This is so
4911 useful that there is a special way to do it, using the @dfn{ignore
4912 count} of the breakpoint. Every breakpoint has an ignore count, which
4913 is an integer. Most of the time, the ignore count is zero, and
4914 therefore has no effect. But if your program reaches a breakpoint whose
4915 ignore count is positive, then instead of stopping, it just decrements
4916 the ignore count by one and continues. As a result, if the ignore count
4917 value is @var{n}, the breakpoint does not stop the next @var{n} times
4918 your program reaches it.
4922 @item ignore @var{bnum} @var{count}
4923 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4924 The next @var{count} times the breakpoint is reached, your program's
4925 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4928 To make the breakpoint stop the next time it is reached, specify
4931 When you use @code{continue} to resume execution of your program from a
4932 breakpoint, you can specify an ignore count directly as an argument to
4933 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4934 Stepping,,Continuing and Stepping}.
4936 If a breakpoint has a positive ignore count and a condition, the
4937 condition is not checked. Once the ignore count reaches zero,
4938 @value{GDBN} resumes checking the condition.
4940 You could achieve the effect of the ignore count with a condition such
4941 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4942 is decremented each time. @xref{Convenience Vars, ,Convenience
4946 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4949 @node Break Commands
4950 @subsection Breakpoint Command Lists
4952 @cindex breakpoint commands
4953 You can give any breakpoint (or watchpoint or catchpoint) a series of
4954 commands to execute when your program stops due to that breakpoint. For
4955 example, you might want to print the values of certain expressions, or
4956 enable other breakpoints.
4960 @kindex end@r{ (breakpoint commands)}
4961 @item commands @r{[}@var{list}@dots{}@r{]}
4962 @itemx @dots{} @var{command-list} @dots{}
4964 Specify a list of commands for the given breakpoints. The commands
4965 themselves appear on the following lines. Type a line containing just
4966 @code{end} to terminate the commands.
4968 To remove all commands from a breakpoint, type @code{commands} and
4969 follow it immediately with @code{end}; that is, give no commands.
4971 With no argument, @code{commands} refers to the last breakpoint,
4972 watchpoint, or catchpoint set (not to the breakpoint most recently
4973 encountered). If the most recent breakpoints were set with a single
4974 command, then the @code{commands} will apply to all the breakpoints
4975 set by that command. This applies to breakpoints set by
4976 @code{rbreak}, and also applies when a single @code{break} command
4977 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4981 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4982 disabled within a @var{command-list}.
4984 You can use breakpoint commands to start your program up again. Simply
4985 use the @code{continue} command, or @code{step}, or any other command
4986 that resumes execution.
4988 Any other commands in the command list, after a command that resumes
4989 execution, are ignored. This is because any time you resume execution
4990 (even with a simple @code{next} or @code{step}), you may encounter
4991 another breakpoint---which could have its own command list, leading to
4992 ambiguities about which list to execute.
4995 If the first command you specify in a command list is @code{silent}, the
4996 usual message about stopping at a breakpoint is not printed. This may
4997 be desirable for breakpoints that are to print a specific message and
4998 then continue. If none of the remaining commands print anything, you
4999 see no sign that the breakpoint was reached. @code{silent} is
5000 meaningful only at the beginning of a breakpoint command list.
5002 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5003 print precisely controlled output, and are often useful in silent
5004 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5006 For example, here is how you could use breakpoint commands to print the
5007 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5013 printf "x is %d\n",x
5018 One application for breakpoint commands is to compensate for one bug so
5019 you can test for another. Put a breakpoint just after the erroneous line
5020 of code, give it a condition to detect the case in which something
5021 erroneous has been done, and give it commands to assign correct values
5022 to any variables that need them. End with the @code{continue} command
5023 so that your program does not stop, and start with the @code{silent}
5024 command so that no output is produced. Here is an example:
5035 @node Dynamic Printf
5036 @subsection Dynamic Printf
5038 @cindex dynamic printf
5040 The dynamic printf command @code{dprintf} combines a breakpoint with
5041 formatted printing of your program's data to give you the effect of
5042 inserting @code{printf} calls into your program on-the-fly, without
5043 having to recompile it.
5045 In its most basic form, the output goes to the GDB console. However,
5046 you can set the variable @code{dprintf-style} for alternate handling.
5047 For instance, you can ask to format the output by calling your
5048 program's @code{printf} function. This has the advantage that the
5049 characters go to the program's output device, so they can recorded in
5050 redirects to files and so forth.
5052 If you are doing remote debugging with a stub or agent, you can also
5053 ask to have the printf handled by the remote agent. In addition to
5054 ensuring that the output goes to the remote program's device along
5055 with any other output the program might produce, you can also ask that
5056 the dprintf remain active even after disconnecting from the remote
5057 target. Using the stub/agent is also more efficient, as it can do
5058 everything without needing to communicate with @value{GDBN}.
5062 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5063 Whenever execution reaches @var{location}, print the values of one or
5064 more @var{expressions} under the control of the string @var{template}.
5065 To print several values, separate them with commas.
5067 @item set dprintf-style @var{style}
5068 Set the dprintf output to be handled in one of several different
5069 styles enumerated below. A change of style affects all existing
5070 dynamic printfs immediately. (If you need individual control over the
5071 print commands, simply define normal breakpoints with
5072 explicitly-supplied command lists.)
5076 @kindex dprintf-style gdb
5077 Handle the output using the @value{GDBN} @code{printf} command.
5080 @kindex dprintf-style call
5081 Handle the output by calling a function in your program (normally
5085 @kindex dprintf-style agent
5086 Have the remote debugging agent (such as @code{gdbserver}) handle
5087 the output itself. This style is only available for agents that
5088 support running commands on the target.
5091 @item set dprintf-function @var{function}
5092 Set the function to call if the dprintf style is @code{call}. By
5093 default its value is @code{printf}. You may set it to any expression.
5094 that @value{GDBN} can evaluate to a function, as per the @code{call}
5097 @item set dprintf-channel @var{channel}
5098 Set a ``channel'' for dprintf. If set to a non-empty value,
5099 @value{GDBN} will evaluate it as an expression and pass the result as
5100 a first argument to the @code{dprintf-function}, in the manner of
5101 @code{fprintf} and similar functions. Otherwise, the dprintf format
5102 string will be the first argument, in the manner of @code{printf}.
5104 As an example, if you wanted @code{dprintf} output to go to a logfile
5105 that is a standard I/O stream assigned to the variable @code{mylog},
5106 you could do the following:
5109 (gdb) set dprintf-style call
5110 (gdb) set dprintf-function fprintf
5111 (gdb) set dprintf-channel mylog
5112 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5113 Dprintf 1 at 0x123456: file main.c, line 25.
5115 1 dprintf keep y 0x00123456 in main at main.c:25
5116 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5121 Note that the @code{info break} displays the dynamic printf commands
5122 as normal breakpoint commands; you can thus easily see the effect of
5123 the variable settings.
5125 @item set disconnected-dprintf on
5126 @itemx set disconnected-dprintf off
5127 @kindex set disconnected-dprintf
5128 Choose whether @code{dprintf} commands should continue to run if
5129 @value{GDBN} has disconnected from the target. This only applies
5130 if the @code{dprintf-style} is @code{agent}.
5132 @item show disconnected-dprintf off
5133 @kindex show disconnected-dprintf
5134 Show the current choice for disconnected @code{dprintf}.
5138 @value{GDBN} does not check the validity of function and channel,
5139 relying on you to supply values that are meaningful for the contexts
5140 in which they are being used. For instance, the function and channel
5141 may be the values of local variables, but if that is the case, then
5142 all enabled dynamic prints must be at locations within the scope of
5143 those locals. If evaluation fails, @value{GDBN} will report an error.
5145 @node Save Breakpoints
5146 @subsection How to save breakpoints to a file
5148 To save breakpoint definitions to a file use the @w{@code{save
5149 breakpoints}} command.
5152 @kindex save breakpoints
5153 @cindex save breakpoints to a file for future sessions
5154 @item save breakpoints [@var{filename}]
5155 This command saves all current breakpoint definitions together with
5156 their commands and ignore counts, into a file @file{@var{filename}}
5157 suitable for use in a later debugging session. This includes all
5158 types of breakpoints (breakpoints, watchpoints, catchpoints,
5159 tracepoints). To read the saved breakpoint definitions, use the
5160 @code{source} command (@pxref{Command Files}). Note that watchpoints
5161 with expressions involving local variables may fail to be recreated
5162 because it may not be possible to access the context where the
5163 watchpoint is valid anymore. Because the saved breakpoint definitions
5164 are simply a sequence of @value{GDBN} commands that recreate the
5165 breakpoints, you can edit the file in your favorite editing program,
5166 and remove the breakpoint definitions you're not interested in, or
5167 that can no longer be recreated.
5170 @node Static Probe Points
5171 @subsection Static Probe Points
5173 @cindex static probe point, SystemTap
5174 @cindex static probe point, DTrace
5175 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5176 for Statically Defined Tracing, and the probes are designed to have a tiny
5177 runtime code and data footprint, and no dynamic relocations.
5179 Currently, the following types of probes are supported on
5180 ELF-compatible systems:
5184 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5185 @acronym{SDT} probes@footnote{See
5186 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5187 for more information on how to add @code{SystemTap} @acronym{SDT}
5188 probes in your applications.}. @code{SystemTap} probes are usable
5189 from assembly, C and C@t{++} languages@footnote{See
5190 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5191 for a good reference on how the @acronym{SDT} probes are implemented.}.
5193 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5194 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5198 @cindex semaphores on static probe points
5199 Some @code{SystemTap} probes have an associated semaphore variable;
5200 for instance, this happens automatically if you defined your probe
5201 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5202 @value{GDBN} will automatically enable it when you specify a
5203 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5204 breakpoint at a probe's location by some other method (e.g.,
5205 @code{break file:line}), then @value{GDBN} will not automatically set
5206 the semaphore. @code{DTrace} probes do not support semaphores.
5208 You can examine the available static static probes using @code{info
5209 probes}, with optional arguments:
5213 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5214 If given, @var{type} is either @code{stap} for listing
5215 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5216 probes. If omitted all probes are listed regardless of their types.
5218 If given, @var{provider} is a regular expression used to match against provider
5219 names when selecting which probes to list. If omitted, probes by all
5220 probes from all providers are listed.
5222 If given, @var{name} is a regular expression to match against probe names
5223 when selecting which probes to list. If omitted, probe names are not
5224 considered when deciding whether to display them.
5226 If given, @var{objfile} is a regular expression used to select which
5227 object files (executable or shared libraries) to examine. If not
5228 given, all object files are considered.
5230 @item info probes all
5231 List the available static probes, from all types.
5234 @cindex enabling and disabling probes
5235 Some probe points can be enabled and/or disabled. The effect of
5236 enabling or disabling a probe depends on the type of probe being
5237 handled. Some @code{DTrace} probes can be enabled or
5238 disabled, but @code{SystemTap} probes cannot be disabled.
5240 You can enable (or disable) one or more probes using the following
5241 commands, with optional arguments:
5244 @kindex enable probes
5245 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5246 If given, @var{provider} is a regular expression used to match against
5247 provider names when selecting which probes to enable. If omitted,
5248 all probes from all providers are enabled.
5250 If given, @var{name} is a regular expression to match against probe
5251 names when selecting which probes to enable. If omitted, probe names
5252 are not considered when deciding whether to enable them.
5254 If given, @var{objfile} is a regular expression used to select which
5255 object files (executable or shared libraries) to examine. If not
5256 given, all object files are considered.
5258 @kindex disable probes
5259 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5260 See the @code{enable probes} command above for a description of the
5261 optional arguments accepted by this command.
5264 @vindex $_probe_arg@r{, convenience variable}
5265 A probe may specify up to twelve arguments. These are available at the
5266 point at which the probe is defined---that is, when the current PC is
5267 at the probe's location. The arguments are available using the
5268 convenience variables (@pxref{Convenience Vars})
5269 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5270 probes each probe argument is an integer of the appropriate size;
5271 types are not preserved. In @code{DTrace} probes types are preserved
5272 provided that they are recognized as such by @value{GDBN}; otherwise
5273 the value of the probe argument will be a long integer. The
5274 convenience variable @code{$_probe_argc} holds the number of arguments
5275 at the current probe point.
5277 These variables are always available, but attempts to access them at
5278 any location other than a probe point will cause @value{GDBN} to give
5282 @c @ifclear BARETARGET
5283 @node Error in Breakpoints
5284 @subsection ``Cannot insert breakpoints''
5286 If you request too many active hardware-assisted breakpoints and
5287 watchpoints, you will see this error message:
5289 @c FIXME: the precise wording of this message may change; the relevant
5290 @c source change is not committed yet (Sep 3, 1999).
5292 Stopped; cannot insert breakpoints.
5293 You may have requested too many hardware breakpoints and watchpoints.
5297 This message is printed when you attempt to resume the program, since
5298 only then @value{GDBN} knows exactly how many hardware breakpoints and
5299 watchpoints it needs to insert.
5301 When this message is printed, you need to disable or remove some of the
5302 hardware-assisted breakpoints and watchpoints, and then continue.
5304 @node Breakpoint-related Warnings
5305 @subsection ``Breakpoint address adjusted...''
5306 @cindex breakpoint address adjusted
5308 Some processor architectures place constraints on the addresses at
5309 which breakpoints may be placed. For architectures thus constrained,
5310 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5311 with the constraints dictated by the architecture.
5313 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5314 a VLIW architecture in which a number of RISC-like instructions may be
5315 bundled together for parallel execution. The FR-V architecture
5316 constrains the location of a breakpoint instruction within such a
5317 bundle to the instruction with the lowest address. @value{GDBN}
5318 honors this constraint by adjusting a breakpoint's address to the
5319 first in the bundle.
5321 It is not uncommon for optimized code to have bundles which contain
5322 instructions from different source statements, thus it may happen that
5323 a breakpoint's address will be adjusted from one source statement to
5324 another. Since this adjustment may significantly alter @value{GDBN}'s
5325 breakpoint related behavior from what the user expects, a warning is
5326 printed when the breakpoint is first set and also when the breakpoint
5329 A warning like the one below is printed when setting a breakpoint
5330 that's been subject to address adjustment:
5333 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5336 Such warnings are printed both for user settable and @value{GDBN}'s
5337 internal breakpoints. If you see one of these warnings, you should
5338 verify that a breakpoint set at the adjusted address will have the
5339 desired affect. If not, the breakpoint in question may be removed and
5340 other breakpoints may be set which will have the desired behavior.
5341 E.g., it may be sufficient to place the breakpoint at a later
5342 instruction. A conditional breakpoint may also be useful in some
5343 cases to prevent the breakpoint from triggering too often.
5345 @value{GDBN} will also issue a warning when stopping at one of these
5346 adjusted breakpoints:
5349 warning: Breakpoint 1 address previously adjusted from 0x00010414
5353 When this warning is encountered, it may be too late to take remedial
5354 action except in cases where the breakpoint is hit earlier or more
5355 frequently than expected.
5357 @node Continuing and Stepping
5358 @section Continuing and Stepping
5362 @cindex resuming execution
5363 @dfn{Continuing} means resuming program execution until your program
5364 completes normally. In contrast, @dfn{stepping} means executing just
5365 one more ``step'' of your program, where ``step'' may mean either one
5366 line of source code, or one machine instruction (depending on what
5367 particular command you use). Either when continuing or when stepping,
5368 your program may stop even sooner, due to a breakpoint or a signal. (If
5369 it stops due to a signal, you may want to use @code{handle}, or use
5370 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5371 or you may step into the signal's handler (@pxref{stepping and signal
5376 @kindex c @r{(@code{continue})}
5377 @kindex fg @r{(resume foreground execution)}
5378 @item continue @r{[}@var{ignore-count}@r{]}
5379 @itemx c @r{[}@var{ignore-count}@r{]}
5380 @itemx fg @r{[}@var{ignore-count}@r{]}
5381 Resume program execution, at the address where your program last stopped;
5382 any breakpoints set at that address are bypassed. The optional argument
5383 @var{ignore-count} allows you to specify a further number of times to
5384 ignore a breakpoint at this location; its effect is like that of
5385 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5387 The argument @var{ignore-count} is meaningful only when your program
5388 stopped due to a breakpoint. At other times, the argument to
5389 @code{continue} is ignored.
5391 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5392 debugged program is deemed to be the foreground program) are provided
5393 purely for convenience, and have exactly the same behavior as
5397 To resume execution at a different place, you can use @code{return}
5398 (@pxref{Returning, ,Returning from a Function}) to go back to the
5399 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5400 Different Address}) to go to an arbitrary location in your program.
5402 A typical technique for using stepping is to set a breakpoint
5403 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5404 beginning of the function or the section of your program where a problem
5405 is believed to lie, run your program until it stops at that breakpoint,
5406 and then step through the suspect area, examining the variables that are
5407 interesting, until you see the problem happen.
5411 @kindex s @r{(@code{step})}
5413 Continue running your program until control reaches a different source
5414 line, then stop it and return control to @value{GDBN}. This command is
5415 abbreviated @code{s}.
5418 @c "without debugging information" is imprecise; actually "without line
5419 @c numbers in the debugging information". (gcc -g1 has debugging info but
5420 @c not line numbers). But it seems complex to try to make that
5421 @c distinction here.
5422 @emph{Warning:} If you use the @code{step} command while control is
5423 within a function that was compiled without debugging information,
5424 execution proceeds until control reaches a function that does have
5425 debugging information. Likewise, it will not step into a function which
5426 is compiled without debugging information. To step through functions
5427 without debugging information, use the @code{stepi} command, described
5431 The @code{step} command only stops at the first instruction of a source
5432 line. This prevents the multiple stops that could otherwise occur in
5433 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5434 to stop if a function that has debugging information is called within
5435 the line. In other words, @code{step} @emph{steps inside} any functions
5436 called within the line.
5438 Also, the @code{step} command only enters a function if there is line
5439 number information for the function. Otherwise it acts like the
5440 @code{next} command. This avoids problems when using @code{cc -gl}
5441 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5442 was any debugging information about the routine.
5444 @item step @var{count}
5445 Continue running as in @code{step}, but do so @var{count} times. If a
5446 breakpoint is reached, or a signal not related to stepping occurs before
5447 @var{count} steps, stepping stops right away.
5450 @kindex n @r{(@code{next})}
5451 @item next @r{[}@var{count}@r{]}
5452 Continue to the next source line in the current (innermost) stack frame.
5453 This is similar to @code{step}, but function calls that appear within
5454 the line of code are executed without stopping. Execution stops when
5455 control reaches a different line of code at the original stack level
5456 that was executing when you gave the @code{next} command. This command
5457 is abbreviated @code{n}.
5459 An argument @var{count} is a repeat count, as for @code{step}.
5462 @c FIX ME!! Do we delete this, or is there a way it fits in with
5463 @c the following paragraph? --- Vctoria
5465 @c @code{next} within a function that lacks debugging information acts like
5466 @c @code{step}, but any function calls appearing within the code of the
5467 @c function are executed without stopping.
5469 The @code{next} command only stops at the first instruction of a
5470 source line. This prevents multiple stops that could otherwise occur in
5471 @code{switch} statements, @code{for} loops, etc.
5473 @kindex set step-mode
5475 @cindex functions without line info, and stepping
5476 @cindex stepping into functions with no line info
5477 @itemx set step-mode on
5478 The @code{set step-mode on} command causes the @code{step} command to
5479 stop at the first instruction of a function which contains no debug line
5480 information rather than stepping over it.
5482 This is useful in cases where you may be interested in inspecting the
5483 machine instructions of a function which has no symbolic info and do not
5484 want @value{GDBN} to automatically skip over this function.
5486 @item set step-mode off
5487 Causes the @code{step} command to step over any functions which contains no
5488 debug information. This is the default.
5490 @item show step-mode
5491 Show whether @value{GDBN} will stop in or step over functions without
5492 source line debug information.
5495 @kindex fin @r{(@code{finish})}
5497 Continue running until just after function in the selected stack frame
5498 returns. Print the returned value (if any). This command can be
5499 abbreviated as @code{fin}.
5501 Contrast this with the @code{return} command (@pxref{Returning,
5502 ,Returning from a Function}).
5505 @kindex u @r{(@code{until})}
5506 @cindex run until specified location
5509 Continue running until a source line past the current line, in the
5510 current stack frame, is reached. This command is used to avoid single
5511 stepping through a loop more than once. It is like the @code{next}
5512 command, except that when @code{until} encounters a jump, it
5513 automatically continues execution until the program counter is greater
5514 than the address of the jump.
5516 This means that when you reach the end of a loop after single stepping
5517 though it, @code{until} makes your program continue execution until it
5518 exits the loop. In contrast, a @code{next} command at the end of a loop
5519 simply steps back to the beginning of the loop, which forces you to step
5520 through the next iteration.
5522 @code{until} always stops your program if it attempts to exit the current
5525 @code{until} may produce somewhat counterintuitive results if the order
5526 of machine code does not match the order of the source lines. For
5527 example, in the following excerpt from a debugging session, the @code{f}
5528 (@code{frame}) command shows that execution is stopped at line
5529 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5533 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5535 (@value{GDBP}) until
5536 195 for ( ; argc > 0; NEXTARG) @{
5539 This happened because, for execution efficiency, the compiler had
5540 generated code for the loop closure test at the end, rather than the
5541 start, of the loop---even though the test in a C @code{for}-loop is
5542 written before the body of the loop. The @code{until} command appeared
5543 to step back to the beginning of the loop when it advanced to this
5544 expression; however, it has not really gone to an earlier
5545 statement---not in terms of the actual machine code.
5547 @code{until} with no argument works by means of single
5548 instruction stepping, and hence is slower than @code{until} with an
5551 @item until @var{location}
5552 @itemx u @var{location}
5553 Continue running your program until either the specified @var{location} is
5554 reached, or the current stack frame returns. The location is any of
5555 the forms described in @ref{Specify Location}.
5556 This form of the command uses temporary breakpoints, and
5557 hence is quicker than @code{until} without an argument. The specified
5558 location is actually reached only if it is in the current frame. This
5559 implies that @code{until} can be used to skip over recursive function
5560 invocations. For instance in the code below, if the current location is
5561 line @code{96}, issuing @code{until 99} will execute the program up to
5562 line @code{99} in the same invocation of factorial, i.e., after the inner
5563 invocations have returned.
5566 94 int factorial (int value)
5568 96 if (value > 1) @{
5569 97 value *= factorial (value - 1);
5576 @kindex advance @var{location}
5577 @item advance @var{location}
5578 Continue running the program up to the given @var{location}. An argument is
5579 required, which should be of one of the forms described in
5580 @ref{Specify Location}.
5581 Execution will also stop upon exit from the current stack
5582 frame. This command is similar to @code{until}, but @code{advance} will
5583 not skip over recursive function calls, and the target location doesn't
5584 have to be in the same frame as the current one.
5588 @kindex si @r{(@code{stepi})}
5590 @itemx stepi @var{arg}
5592 Execute one machine instruction, then stop and return to the debugger.
5594 It is often useful to do @samp{display/i $pc} when stepping by machine
5595 instructions. This makes @value{GDBN} automatically display the next
5596 instruction to be executed, each time your program stops. @xref{Auto
5597 Display,, Automatic Display}.
5599 An argument is a repeat count, as in @code{step}.
5603 @kindex ni @r{(@code{nexti})}
5605 @itemx nexti @var{arg}
5607 Execute one machine instruction, but if it is a function call,
5608 proceed until the function returns.
5610 An argument is a repeat count, as in @code{next}.
5614 @anchor{range stepping}
5615 @cindex range stepping
5616 @cindex target-assisted range stepping
5617 By default, and if available, @value{GDBN} makes use of
5618 target-assisted @dfn{range stepping}. In other words, whenever you
5619 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5620 tells the target to step the corresponding range of instruction
5621 addresses instead of issuing multiple single-steps. This speeds up
5622 line stepping, particularly for remote targets. Ideally, there should
5623 be no reason you would want to turn range stepping off. However, it's
5624 possible that a bug in the debug info, a bug in the remote stub (for
5625 remote targets), or even a bug in @value{GDBN} could make line
5626 stepping behave incorrectly when target-assisted range stepping is
5627 enabled. You can use the following command to turn off range stepping
5631 @kindex set range-stepping
5632 @kindex show range-stepping
5633 @item set range-stepping
5634 @itemx show range-stepping
5635 Control whether range stepping is enabled.
5637 If @code{on}, and the target supports it, @value{GDBN} tells the
5638 target to step a range of addresses itself, instead of issuing
5639 multiple single-steps. If @code{off}, @value{GDBN} always issues
5640 single-steps, even if range stepping is supported by the target. The
5641 default is @code{on}.
5645 @node Skipping Over Functions and Files
5646 @section Skipping Over Functions and Files
5647 @cindex skipping over functions and files
5649 The program you are debugging may contain some functions which are
5650 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5651 skip a function, all functions in a file or a particular function in
5652 a particular file when stepping.
5654 For example, consider the following C function:
5665 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5666 are not interested in stepping through @code{boring}. If you run @code{step}
5667 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5668 step over both @code{foo} and @code{boring}!
5670 One solution is to @code{step} into @code{boring} and use the @code{finish}
5671 command to immediately exit it. But this can become tedious if @code{boring}
5672 is called from many places.
5674 A more flexible solution is to execute @kbd{skip boring}. This instructs
5675 @value{GDBN} never to step into @code{boring}. Now when you execute
5676 @code{step} at line 103, you'll step over @code{boring} and directly into
5679 Functions may be skipped by providing either a function name, linespec
5680 (@pxref{Specify Location}), regular expression that matches the function's
5681 name, file name or a @code{glob}-style pattern that matches the file name.
5683 On Posix systems the form of the regular expression is
5684 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5685 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5686 expression is whatever is provided by the @code{regcomp} function of
5687 the underlying system.
5688 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5689 description of @code{glob}-style patterns.
5693 @item skip @r{[}@var{options}@r{]}
5694 The basic form of the @code{skip} command takes zero or more options
5695 that specify what to skip.
5696 The @var{options} argument is any useful combination of the following:
5699 @item -file @var{file}
5700 @itemx -fi @var{file}
5701 Functions in @var{file} will be skipped over when stepping.
5703 @item -gfile @var{file-glob-pattern}
5704 @itemx -gfi @var{file-glob-pattern}
5705 @cindex skipping over files via glob-style patterns
5706 Functions in files matching @var{file-glob-pattern} will be skipped
5710 (gdb) skip -gfi utils/*.c
5713 @item -function @var{linespec}
5714 @itemx -fu @var{linespec}
5715 Functions named by @var{linespec} or the function containing the line
5716 named by @var{linespec} will be skipped over when stepping.
5717 @xref{Specify Location}.
5719 @item -rfunction @var{regexp}
5720 @itemx -rfu @var{regexp}
5721 @cindex skipping over functions via regular expressions
5722 Functions whose name matches @var{regexp} will be skipped over when stepping.
5724 This form is useful for complex function names.
5725 For example, there is generally no need to step into C@t{++} @code{std::string}
5726 constructors or destructors. Plus with C@t{++} templates it can be hard to
5727 write out the full name of the function, and often it doesn't matter what
5728 the template arguments are. Specifying the function to be skipped as a
5729 regular expression makes this easier.
5732 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5735 If you want to skip every templated C@t{++} constructor and destructor
5736 in the @code{std} namespace you can do:
5739 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5743 If no options are specified, the function you're currently debugging
5746 @kindex skip function
5747 @item skip function @r{[}@var{linespec}@r{]}
5748 After running this command, the function named by @var{linespec} or the
5749 function containing the line named by @var{linespec} will be skipped over when
5750 stepping. @xref{Specify Location}.
5752 If you do not specify @var{linespec}, the function you're currently debugging
5755 (If you have a function called @code{file} that you want to skip, use
5756 @kbd{skip function file}.)
5759 @item skip file @r{[}@var{filename}@r{]}
5760 After running this command, any function whose source lives in @var{filename}
5761 will be skipped over when stepping.
5764 (gdb) skip file boring.c
5765 File boring.c will be skipped when stepping.
5768 If you do not specify @var{filename}, functions whose source lives in the file
5769 you're currently debugging will be skipped.
5772 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5773 These are the commands for managing your list of skips:
5777 @item info skip @r{[}@var{range}@r{]}
5778 Print details about the specified skip(s). If @var{range} is not specified,
5779 print a table with details about all functions and files marked for skipping.
5780 @code{info skip} prints the following information about each skip:
5784 A number identifying this skip.
5785 @item Enabled or Disabled
5786 Enabled skips are marked with @samp{y}.
5787 Disabled skips are marked with @samp{n}.
5789 If the file name is a @samp{glob} pattern this is @samp{y}.
5790 Otherwise it is @samp{n}.
5792 The name or @samp{glob} pattern of the file to be skipped.
5793 If no file is specified this is @samp{<none>}.
5795 If the function name is a @samp{regular expression} this is @samp{y}.
5796 Otherwise it is @samp{n}.
5798 The name or regular expression of the function to skip.
5799 If no function is specified this is @samp{<none>}.
5803 @item skip delete @r{[}@var{range}@r{]}
5804 Delete the specified skip(s). If @var{range} is not specified, delete all
5808 @item skip enable @r{[}@var{range}@r{]}
5809 Enable the specified skip(s). If @var{range} is not specified, enable all
5812 @kindex skip disable
5813 @item skip disable @r{[}@var{range}@r{]}
5814 Disable the specified skip(s). If @var{range} is not specified, disable all
5823 A signal is an asynchronous event that can happen in a program. The
5824 operating system defines the possible kinds of signals, and gives each
5825 kind a name and a number. For example, in Unix @code{SIGINT} is the
5826 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5827 @code{SIGSEGV} is the signal a program gets from referencing a place in
5828 memory far away from all the areas in use; @code{SIGALRM} occurs when
5829 the alarm clock timer goes off (which happens only if your program has
5830 requested an alarm).
5832 @cindex fatal signals
5833 Some signals, including @code{SIGALRM}, are a normal part of the
5834 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5835 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5836 program has not specified in advance some other way to handle the signal.
5837 @code{SIGINT} does not indicate an error in your program, but it is normally
5838 fatal so it can carry out the purpose of the interrupt: to kill the program.
5840 @value{GDBN} has the ability to detect any occurrence of a signal in your
5841 program. You can tell @value{GDBN} in advance what to do for each kind of
5844 @cindex handling signals
5845 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5846 @code{SIGALRM} be silently passed to your program
5847 (so as not to interfere with their role in the program's functioning)
5848 but to stop your program immediately whenever an error signal happens.
5849 You can change these settings with the @code{handle} command.
5852 @kindex info signals
5856 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5857 handle each one. You can use this to see the signal numbers of all
5858 the defined types of signals.
5860 @item info signals @var{sig}
5861 Similar, but print information only about the specified signal number.
5863 @code{info handle} is an alias for @code{info signals}.
5865 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5866 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5867 for details about this command.
5870 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5871 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5872 can be the number of a signal or its name (with or without the
5873 @samp{SIG} at the beginning); a list of signal numbers of the form
5874 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5875 known signals. Optional arguments @var{keywords}, described below,
5876 say what change to make.
5880 The keywords allowed by the @code{handle} command can be abbreviated.
5881 Their full names are:
5885 @value{GDBN} should not stop your program when this signal happens. It may
5886 still print a message telling you that the signal has come in.
5889 @value{GDBN} should stop your program when this signal happens. This implies
5890 the @code{print} keyword as well.
5893 @value{GDBN} should print a message when this signal happens.
5896 @value{GDBN} should not mention the occurrence of the signal at all. This
5897 implies the @code{nostop} keyword as well.
5901 @value{GDBN} should allow your program to see this signal; your program
5902 can handle the signal, or else it may terminate if the signal is fatal
5903 and not handled. @code{pass} and @code{noignore} are synonyms.
5907 @value{GDBN} should not allow your program to see this signal.
5908 @code{nopass} and @code{ignore} are synonyms.
5912 When a signal stops your program, the signal is not visible to the
5914 continue. Your program sees the signal then, if @code{pass} is in
5915 effect for the signal in question @emph{at that time}. In other words,
5916 after @value{GDBN} reports a signal, you can use the @code{handle}
5917 command with @code{pass} or @code{nopass} to control whether your
5918 program sees that signal when you continue.
5920 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5921 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5922 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5925 You can also use the @code{signal} command to prevent your program from
5926 seeing a signal, or cause it to see a signal it normally would not see,
5927 or to give it any signal at any time. For example, if your program stopped
5928 due to some sort of memory reference error, you might store correct
5929 values into the erroneous variables and continue, hoping to see more
5930 execution; but your program would probably terminate immediately as
5931 a result of the fatal signal once it saw the signal. To prevent this,
5932 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5935 @cindex stepping and signal handlers
5936 @anchor{stepping and signal handlers}
5938 @value{GDBN} optimizes for stepping the mainline code. If a signal
5939 that has @code{handle nostop} and @code{handle pass} set arrives while
5940 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5941 in progress, @value{GDBN} lets the signal handler run and then resumes
5942 stepping the mainline code once the signal handler returns. In other
5943 words, @value{GDBN} steps over the signal handler. This prevents
5944 signals that you've specified as not interesting (with @code{handle
5945 nostop}) from changing the focus of debugging unexpectedly. Note that
5946 the signal handler itself may still hit a breakpoint, stop for another
5947 signal that has @code{handle stop} in effect, or for any other event
5948 that normally results in stopping the stepping command sooner. Also
5949 note that @value{GDBN} still informs you that the program received a
5950 signal if @code{handle print} is set.
5952 @anchor{stepping into signal handlers}
5954 If you set @code{handle pass} for a signal, and your program sets up a
5955 handler for it, then issuing a stepping command, such as @code{step}
5956 or @code{stepi}, when your program is stopped due to the signal will
5957 step @emph{into} the signal handler (if the target supports that).
5959 Likewise, if you use the @code{queue-signal} command to queue a signal
5960 to be delivered to the current thread when execution of the thread
5961 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5962 stepping command will step into the signal handler.
5964 Here's an example, using @code{stepi} to step to the first instruction
5965 of @code{SIGUSR1}'s handler:
5968 (@value{GDBP}) handle SIGUSR1
5969 Signal Stop Print Pass to program Description
5970 SIGUSR1 Yes Yes Yes User defined signal 1
5974 Program received signal SIGUSR1, User defined signal 1.
5975 main () sigusr1.c:28
5978 sigusr1_handler () at sigusr1.c:9
5982 The same, but using @code{queue-signal} instead of waiting for the
5983 program to receive the signal first:
5988 (@value{GDBP}) queue-signal SIGUSR1
5990 sigusr1_handler () at sigusr1.c:9
5995 @cindex extra signal information
5996 @anchor{extra signal information}
5998 On some targets, @value{GDBN} can inspect extra signal information
5999 associated with the intercepted signal, before it is actually
6000 delivered to the program being debugged. This information is exported
6001 by the convenience variable @code{$_siginfo}, and consists of data
6002 that is passed by the kernel to the signal handler at the time of the
6003 receipt of a signal. The data type of the information itself is
6004 target dependent. You can see the data type using the @code{ptype
6005 $_siginfo} command. On Unix systems, it typically corresponds to the
6006 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6009 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6010 referenced address that raised a segmentation fault.
6014 (@value{GDBP}) continue
6015 Program received signal SIGSEGV, Segmentation fault.
6016 0x0000000000400766 in main ()
6018 (@value{GDBP}) ptype $_siginfo
6025 struct @{...@} _kill;
6026 struct @{...@} _timer;
6028 struct @{...@} _sigchld;
6029 struct @{...@} _sigfault;
6030 struct @{...@} _sigpoll;
6033 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6037 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6038 $1 = (void *) 0x7ffff7ff7000
6042 Depending on target support, @code{$_siginfo} may also be writable.
6044 @cindex Intel MPX boundary violations
6045 @cindex boundary violations, Intel MPX
6046 On some targets, a @code{SIGSEGV} can be caused by a boundary
6047 violation, i.e., accessing an address outside of the allowed range.
6048 In those cases @value{GDBN} may displays additional information,
6049 depending on how @value{GDBN} has been told to handle the signal.
6050 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6051 kind: "Upper" or "Lower", the memory address accessed and the
6052 bounds, while with @code{handle nostop SIGSEGV} no additional
6053 information is displayed.
6055 The usual output of a segfault is:
6057 Program received signal SIGSEGV, Segmentation fault
6058 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6059 68 value = *(p + len);
6062 While a bound violation is presented as:
6064 Program received signal SIGSEGV, Segmentation fault
6065 Upper bound violation while accessing address 0x7fffffffc3b3
6066 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6067 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6068 68 value = *(p + len);
6072 @section Stopping and Starting Multi-thread Programs
6074 @cindex stopped threads
6075 @cindex threads, stopped
6077 @cindex continuing threads
6078 @cindex threads, continuing
6080 @value{GDBN} supports debugging programs with multiple threads
6081 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6082 are two modes of controlling execution of your program within the
6083 debugger. In the default mode, referred to as @dfn{all-stop mode},
6084 when any thread in your program stops (for example, at a breakpoint
6085 or while being stepped), all other threads in the program are also stopped by
6086 @value{GDBN}. On some targets, @value{GDBN} also supports
6087 @dfn{non-stop mode}, in which other threads can continue to run freely while
6088 you examine the stopped thread in the debugger.
6091 * All-Stop Mode:: All threads stop when GDB takes control
6092 * Non-Stop Mode:: Other threads continue to execute
6093 * Background Execution:: Running your program asynchronously
6094 * Thread-Specific Breakpoints:: Controlling breakpoints
6095 * Interrupted System Calls:: GDB may interfere with system calls
6096 * Observer Mode:: GDB does not alter program behavior
6100 @subsection All-Stop Mode
6102 @cindex all-stop mode
6104 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6105 @emph{all} threads of execution stop, not just the current thread. This
6106 allows you to examine the overall state of the program, including
6107 switching between threads, without worrying that things may change
6110 Conversely, whenever you restart the program, @emph{all} threads start
6111 executing. @emph{This is true even when single-stepping} with commands
6112 like @code{step} or @code{next}.
6114 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6115 Since thread scheduling is up to your debugging target's operating
6116 system (not controlled by @value{GDBN}), other threads may
6117 execute more than one statement while the current thread completes a
6118 single step. Moreover, in general other threads stop in the middle of a
6119 statement, rather than at a clean statement boundary, when the program
6122 You might even find your program stopped in another thread after
6123 continuing or even single-stepping. This happens whenever some other
6124 thread runs into a breakpoint, a signal, or an exception before the
6125 first thread completes whatever you requested.
6127 @cindex automatic thread selection
6128 @cindex switching threads automatically
6129 @cindex threads, automatic switching
6130 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6131 signal, it automatically selects the thread where that breakpoint or
6132 signal happened. @value{GDBN} alerts you to the context switch with a
6133 message such as @samp{[Switching to Thread @var{n}]} to identify the
6136 On some OSes, you can modify @value{GDBN}'s default behavior by
6137 locking the OS scheduler to allow only a single thread to run.
6140 @item set scheduler-locking @var{mode}
6141 @cindex scheduler locking mode
6142 @cindex lock scheduler
6143 Set the scheduler locking mode. It applies to normal execution,
6144 record mode, and replay mode. If it is @code{off}, then there is no
6145 locking and any thread may run at any time. If @code{on}, then only
6146 the current thread may run when the inferior is resumed. The
6147 @code{step} mode optimizes for single-stepping; it prevents other
6148 threads from preempting the current thread while you are stepping, so
6149 that the focus of debugging does not change unexpectedly. Other
6150 threads never get a chance to run when you step, and they are
6151 completely free to run when you use commands like @samp{continue},
6152 @samp{until}, or @samp{finish}. However, unless another thread hits a
6153 breakpoint during its timeslice, @value{GDBN} does not change the
6154 current thread away from the thread that you are debugging. The
6155 @code{replay} mode behaves like @code{off} in record mode and like
6156 @code{on} in replay mode.
6158 @item show scheduler-locking
6159 Display the current scheduler locking mode.
6162 @cindex resume threads of multiple processes simultaneously
6163 By default, when you issue one of the execution commands such as
6164 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6165 threads of the current inferior to run. For example, if @value{GDBN}
6166 is attached to two inferiors, each with two threads, the
6167 @code{continue} command resumes only the two threads of the current
6168 inferior. This is useful, for example, when you debug a program that
6169 forks and you want to hold the parent stopped (so that, for instance,
6170 it doesn't run to exit), while you debug the child. In other
6171 situations, you may not be interested in inspecting the current state
6172 of any of the processes @value{GDBN} is attached to, and you may want
6173 to resume them all until some breakpoint is hit. In the latter case,
6174 you can instruct @value{GDBN} to allow all threads of all the
6175 inferiors to run with the @w{@code{set schedule-multiple}} command.
6178 @kindex set schedule-multiple
6179 @item set schedule-multiple
6180 Set the mode for allowing threads of multiple processes to be resumed
6181 when an execution command is issued. When @code{on}, all threads of
6182 all processes are allowed to run. When @code{off}, only the threads
6183 of the current process are resumed. The default is @code{off}. The
6184 @code{scheduler-locking} mode takes precedence when set to @code{on},
6185 or while you are stepping and set to @code{step}.
6187 @item show schedule-multiple
6188 Display the current mode for resuming the execution of threads of
6193 @subsection Non-Stop Mode
6195 @cindex non-stop mode
6197 @c This section is really only a place-holder, and needs to be expanded
6198 @c with more details.
6200 For some multi-threaded targets, @value{GDBN} supports an optional
6201 mode of operation in which you can examine stopped program threads in
6202 the debugger while other threads continue to execute freely. This
6203 minimizes intrusion when debugging live systems, such as programs
6204 where some threads have real-time constraints or must continue to
6205 respond to external events. This is referred to as @dfn{non-stop} mode.
6207 In non-stop mode, when a thread stops to report a debugging event,
6208 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6209 threads as well, in contrast to the all-stop mode behavior. Additionally,
6210 execution commands such as @code{continue} and @code{step} apply by default
6211 only to the current thread in non-stop mode, rather than all threads as
6212 in all-stop mode. This allows you to control threads explicitly in
6213 ways that are not possible in all-stop mode --- for example, stepping
6214 one thread while allowing others to run freely, stepping
6215 one thread while holding all others stopped, or stepping several threads
6216 independently and simultaneously.
6218 To enter non-stop mode, use this sequence of commands before you run
6219 or attach to your program:
6222 # If using the CLI, pagination breaks non-stop.
6225 # Finally, turn it on!
6229 You can use these commands to manipulate the non-stop mode setting:
6232 @kindex set non-stop
6233 @item set non-stop on
6234 Enable selection of non-stop mode.
6235 @item set non-stop off
6236 Disable selection of non-stop mode.
6237 @kindex show non-stop
6239 Show the current non-stop enablement setting.
6242 Note these commands only reflect whether non-stop mode is enabled,
6243 not whether the currently-executing program is being run in non-stop mode.
6244 In particular, the @code{set non-stop} preference is only consulted when
6245 @value{GDBN} starts or connects to the target program, and it is generally
6246 not possible to switch modes once debugging has started. Furthermore,
6247 since not all targets support non-stop mode, even when you have enabled
6248 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6251 In non-stop mode, all execution commands apply only to the current thread
6252 by default. That is, @code{continue} only continues one thread.
6253 To continue all threads, issue @code{continue -a} or @code{c -a}.
6255 You can use @value{GDBN}'s background execution commands
6256 (@pxref{Background Execution}) to run some threads in the background
6257 while you continue to examine or step others from @value{GDBN}.
6258 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6259 always executed asynchronously in non-stop mode.
6261 Suspending execution is done with the @code{interrupt} command when
6262 running in the background, or @kbd{Ctrl-c} during foreground execution.
6263 In all-stop mode, this stops the whole process;
6264 but in non-stop mode the interrupt applies only to the current thread.
6265 To stop the whole program, use @code{interrupt -a}.
6267 Other execution commands do not currently support the @code{-a} option.
6269 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6270 that thread current, as it does in all-stop mode. This is because the
6271 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6272 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6273 changed to a different thread just as you entered a command to operate on the
6274 previously current thread.
6276 @node Background Execution
6277 @subsection Background Execution
6279 @cindex foreground execution
6280 @cindex background execution
6281 @cindex asynchronous execution
6282 @cindex execution, foreground, background and asynchronous
6284 @value{GDBN}'s execution commands have two variants: the normal
6285 foreground (synchronous) behavior, and a background
6286 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6287 the program to report that some thread has stopped before prompting for
6288 another command. In background execution, @value{GDBN} immediately gives
6289 a command prompt so that you can issue other commands while your program runs.
6291 If the target doesn't support async mode, @value{GDBN} issues an error
6292 message if you attempt to use the background execution commands.
6294 To specify background execution, add a @code{&} to the command. For example,
6295 the background form of the @code{continue} command is @code{continue&}, or
6296 just @code{c&}. The execution commands that accept background execution
6302 @xref{Starting, , Starting your Program}.
6306 @xref{Attach, , Debugging an Already-running Process}.
6310 @xref{Continuing and Stepping, step}.
6314 @xref{Continuing and Stepping, stepi}.
6318 @xref{Continuing and Stepping, next}.
6322 @xref{Continuing and Stepping, nexti}.
6326 @xref{Continuing and Stepping, continue}.
6330 @xref{Continuing and Stepping, finish}.
6334 @xref{Continuing and Stepping, until}.
6338 Background execution is especially useful in conjunction with non-stop
6339 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6340 However, you can also use these commands in the normal all-stop mode with
6341 the restriction that you cannot issue another execution command until the
6342 previous one finishes. Examples of commands that are valid in all-stop
6343 mode while the program is running include @code{help} and @code{info break}.
6345 You can interrupt your program while it is running in the background by
6346 using the @code{interrupt} command.
6353 Suspend execution of the running program. In all-stop mode,
6354 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6355 only the current thread. To stop the whole program in non-stop mode,
6356 use @code{interrupt -a}.
6359 @node Thread-Specific Breakpoints
6360 @subsection Thread-Specific Breakpoints
6362 When your program has multiple threads (@pxref{Threads,, Debugging
6363 Programs with Multiple Threads}), you can choose whether to set
6364 breakpoints on all threads, or on a particular thread.
6367 @cindex breakpoints and threads
6368 @cindex thread breakpoints
6369 @kindex break @dots{} thread @var{thread-id}
6370 @item break @var{location} thread @var{thread-id}
6371 @itemx break @var{location} thread @var{thread-id} if @dots{}
6372 @var{location} specifies source lines; there are several ways of
6373 writing them (@pxref{Specify Location}), but the effect is always to
6374 specify some source line.
6376 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6377 to specify that you only want @value{GDBN} to stop the program when a
6378 particular thread reaches this breakpoint. The @var{thread-id} specifier
6379 is one of the thread identifiers assigned by @value{GDBN}, shown
6380 in the first column of the @samp{info threads} display.
6382 If you do not specify @samp{thread @var{thread-id}} when you set a
6383 breakpoint, the breakpoint applies to @emph{all} threads of your
6386 You can use the @code{thread} qualifier on conditional breakpoints as
6387 well; in this case, place @samp{thread @var{thread-id}} before or
6388 after the breakpoint condition, like this:
6391 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6396 Thread-specific breakpoints are automatically deleted when
6397 @value{GDBN} detects the corresponding thread is no longer in the
6398 thread list. For example:
6402 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6405 There are several ways for a thread to disappear, such as a regular
6406 thread exit, but also when you detach from the process with the
6407 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6408 Process}), or if @value{GDBN} loses the remote connection
6409 (@pxref{Remote Debugging}), etc. Note that with some targets,
6410 @value{GDBN} is only able to detect a thread has exited when the user
6411 explictly asks for the thread list with the @code{info threads}
6414 @node Interrupted System Calls
6415 @subsection Interrupted System Calls
6417 @cindex thread breakpoints and system calls
6418 @cindex system calls and thread breakpoints
6419 @cindex premature return from system calls
6420 There is an unfortunate side effect when using @value{GDBN} to debug
6421 multi-threaded programs. If one thread stops for a
6422 breakpoint, or for some other reason, and another thread is blocked in a
6423 system call, then the system call may return prematurely. This is a
6424 consequence of the interaction between multiple threads and the signals
6425 that @value{GDBN} uses to implement breakpoints and other events that
6428 To handle this problem, your program should check the return value of
6429 each system call and react appropriately. This is good programming
6432 For example, do not write code like this:
6438 The call to @code{sleep} will return early if a different thread stops
6439 at a breakpoint or for some other reason.
6441 Instead, write this:
6446 unslept = sleep (unslept);
6449 A system call is allowed to return early, so the system is still
6450 conforming to its specification. But @value{GDBN} does cause your
6451 multi-threaded program to behave differently than it would without
6454 Also, @value{GDBN} uses internal breakpoints in the thread library to
6455 monitor certain events such as thread creation and thread destruction.
6456 When such an event happens, a system call in another thread may return
6457 prematurely, even though your program does not appear to stop.
6460 @subsection Observer Mode
6462 If you want to build on non-stop mode and observe program behavior
6463 without any chance of disruption by @value{GDBN}, you can set
6464 variables to disable all of the debugger's attempts to modify state,
6465 whether by writing memory, inserting breakpoints, etc. These operate
6466 at a low level, intercepting operations from all commands.
6468 When all of these are set to @code{off}, then @value{GDBN} is said to
6469 be @dfn{observer mode}. As a convenience, the variable
6470 @code{observer} can be set to disable these, plus enable non-stop
6473 Note that @value{GDBN} will not prevent you from making nonsensical
6474 combinations of these settings. For instance, if you have enabled
6475 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6476 then breakpoints that work by writing trap instructions into the code
6477 stream will still not be able to be placed.
6482 @item set observer on
6483 @itemx set observer off
6484 When set to @code{on}, this disables all the permission variables
6485 below (except for @code{insert-fast-tracepoints}), plus enables
6486 non-stop debugging. Setting this to @code{off} switches back to
6487 normal debugging, though remaining in non-stop mode.
6490 Show whether observer mode is on or off.
6492 @kindex may-write-registers
6493 @item set may-write-registers on
6494 @itemx set may-write-registers off
6495 This controls whether @value{GDBN} will attempt to alter the values of
6496 registers, such as with assignment expressions in @code{print}, or the
6497 @code{jump} command. It defaults to @code{on}.
6499 @item show may-write-registers
6500 Show the current permission to write registers.
6502 @kindex may-write-memory
6503 @item set may-write-memory on
6504 @itemx set may-write-memory off
6505 This controls whether @value{GDBN} will attempt to alter the contents
6506 of memory, such as with assignment expressions in @code{print}. It
6507 defaults to @code{on}.
6509 @item show may-write-memory
6510 Show the current permission to write memory.
6512 @kindex may-insert-breakpoints
6513 @item set may-insert-breakpoints on
6514 @itemx set may-insert-breakpoints off
6515 This controls whether @value{GDBN} will attempt to insert breakpoints.
6516 This affects all breakpoints, including internal breakpoints defined
6517 by @value{GDBN}. It defaults to @code{on}.
6519 @item show may-insert-breakpoints
6520 Show the current permission to insert breakpoints.
6522 @kindex may-insert-tracepoints
6523 @item set may-insert-tracepoints on
6524 @itemx set may-insert-tracepoints off
6525 This controls whether @value{GDBN} will attempt to insert (regular)
6526 tracepoints at the beginning of a tracing experiment. It affects only
6527 non-fast tracepoints, fast tracepoints being under the control of
6528 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6530 @item show may-insert-tracepoints
6531 Show the current permission to insert tracepoints.
6533 @kindex may-insert-fast-tracepoints
6534 @item set may-insert-fast-tracepoints on
6535 @itemx set may-insert-fast-tracepoints off
6536 This controls whether @value{GDBN} will attempt to insert fast
6537 tracepoints at the beginning of a tracing experiment. It affects only
6538 fast tracepoints, regular (non-fast) tracepoints being under the
6539 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6541 @item show may-insert-fast-tracepoints
6542 Show the current permission to insert fast tracepoints.
6544 @kindex may-interrupt
6545 @item set may-interrupt on
6546 @itemx set may-interrupt off
6547 This controls whether @value{GDBN} will attempt to interrupt or stop
6548 program execution. When this variable is @code{off}, the
6549 @code{interrupt} command will have no effect, nor will
6550 @kbd{Ctrl-c}. It defaults to @code{on}.
6552 @item show may-interrupt
6553 Show the current permission to interrupt or stop the program.
6557 @node Reverse Execution
6558 @chapter Running programs backward
6559 @cindex reverse execution
6560 @cindex running programs backward
6562 When you are debugging a program, it is not unusual to realize that
6563 you have gone too far, and some event of interest has already happened.
6564 If the target environment supports it, @value{GDBN} can allow you to
6565 ``rewind'' the program by running it backward.
6567 A target environment that supports reverse execution should be able
6568 to ``undo'' the changes in machine state that have taken place as the
6569 program was executing normally. Variables, registers etc.@: should
6570 revert to their previous values. Obviously this requires a great
6571 deal of sophistication on the part of the target environment; not
6572 all target environments can support reverse execution.
6574 When a program is executed in reverse, the instructions that
6575 have most recently been executed are ``un-executed'', in reverse
6576 order. The program counter runs backward, following the previous
6577 thread of execution in reverse. As each instruction is ``un-executed'',
6578 the values of memory and/or registers that were changed by that
6579 instruction are reverted to their previous states. After executing
6580 a piece of source code in reverse, all side effects of that code
6581 should be ``undone'', and all variables should be returned to their
6582 prior values@footnote{
6583 Note that some side effects are easier to undo than others. For instance,
6584 memory and registers are relatively easy, but device I/O is hard. Some
6585 targets may be able undo things like device I/O, and some may not.
6587 The contract between @value{GDBN} and the reverse executing target
6588 requires only that the target do something reasonable when
6589 @value{GDBN} tells it to execute backwards, and then report the
6590 results back to @value{GDBN}. Whatever the target reports back to
6591 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6592 assumes that the memory and registers that the target reports are in a
6593 consistant state, but @value{GDBN} accepts whatever it is given.
6596 If you are debugging in a target environment that supports
6597 reverse execution, @value{GDBN} provides the following commands.
6600 @kindex reverse-continue
6601 @kindex rc @r{(@code{reverse-continue})}
6602 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6603 @itemx rc @r{[}@var{ignore-count}@r{]}
6604 Beginning at the point where your program last stopped, start executing
6605 in reverse. Reverse execution will stop for breakpoints and synchronous
6606 exceptions (signals), just like normal execution. Behavior of
6607 asynchronous signals depends on the target environment.
6609 @kindex reverse-step
6610 @kindex rs @r{(@code{step})}
6611 @item reverse-step @r{[}@var{count}@r{]}
6612 Run the program backward until control reaches the start of a
6613 different source line; then stop it, and return control to @value{GDBN}.
6615 Like the @code{step} command, @code{reverse-step} will only stop
6616 at the beginning of a source line. It ``un-executes'' the previously
6617 executed source line. If the previous source line included calls to
6618 debuggable functions, @code{reverse-step} will step (backward) into
6619 the called function, stopping at the beginning of the @emph{last}
6620 statement in the called function (typically a return statement).
6622 Also, as with the @code{step} command, if non-debuggable functions are
6623 called, @code{reverse-step} will run thru them backward without stopping.
6625 @kindex reverse-stepi
6626 @kindex rsi @r{(@code{reverse-stepi})}
6627 @item reverse-stepi @r{[}@var{count}@r{]}
6628 Reverse-execute one machine instruction. Note that the instruction
6629 to be reverse-executed is @emph{not} the one pointed to by the program
6630 counter, but the instruction executed prior to that one. For instance,
6631 if the last instruction was a jump, @code{reverse-stepi} will take you
6632 back from the destination of the jump to the jump instruction itself.
6634 @kindex reverse-next
6635 @kindex rn @r{(@code{reverse-next})}
6636 @item reverse-next @r{[}@var{count}@r{]}
6637 Run backward to the beginning of the previous line executed in
6638 the current (innermost) stack frame. If the line contains function
6639 calls, they will be ``un-executed'' without stopping. Starting from
6640 the first line of a function, @code{reverse-next} will take you back
6641 to the caller of that function, @emph{before} the function was called,
6642 just as the normal @code{next} command would take you from the last
6643 line of a function back to its return to its caller
6644 @footnote{Unless the code is too heavily optimized.}.
6646 @kindex reverse-nexti
6647 @kindex rni @r{(@code{reverse-nexti})}
6648 @item reverse-nexti @r{[}@var{count}@r{]}
6649 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6650 in reverse, except that called functions are ``un-executed'' atomically.
6651 That is, if the previously executed instruction was a return from
6652 another function, @code{reverse-nexti} will continue to execute
6653 in reverse until the call to that function (from the current stack
6656 @kindex reverse-finish
6657 @item reverse-finish
6658 Just as the @code{finish} command takes you to the point where the
6659 current function returns, @code{reverse-finish} takes you to the point
6660 where it was called. Instead of ending up at the end of the current
6661 function invocation, you end up at the beginning.
6663 @kindex set exec-direction
6664 @item set exec-direction
6665 Set the direction of target execution.
6666 @item set exec-direction reverse
6667 @cindex execute forward or backward in time
6668 @value{GDBN} will perform all execution commands in reverse, until the
6669 exec-direction mode is changed to ``forward''. Affected commands include
6670 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6671 command cannot be used in reverse mode.
6672 @item set exec-direction forward
6673 @value{GDBN} will perform all execution commands in the normal fashion.
6674 This is the default.
6678 @node Process Record and Replay
6679 @chapter Recording Inferior's Execution and Replaying It
6680 @cindex process record and replay
6681 @cindex recording inferior's execution and replaying it
6683 On some platforms, @value{GDBN} provides a special @dfn{process record
6684 and replay} target that can record a log of the process execution, and
6685 replay it later with both forward and reverse execution commands.
6688 When this target is in use, if the execution log includes the record
6689 for the next instruction, @value{GDBN} will debug in @dfn{replay
6690 mode}. In the replay mode, the inferior does not really execute code
6691 instructions. Instead, all the events that normally happen during
6692 code execution are taken from the execution log. While code is not
6693 really executed in replay mode, the values of registers (including the
6694 program counter register) and the memory of the inferior are still
6695 changed as they normally would. Their contents are taken from the
6699 If the record for the next instruction is not in the execution log,
6700 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6701 inferior executes normally, and @value{GDBN} records the execution log
6704 The process record and replay target supports reverse execution
6705 (@pxref{Reverse Execution}), even if the platform on which the
6706 inferior runs does not. However, the reverse execution is limited in
6707 this case by the range of the instructions recorded in the execution
6708 log. In other words, reverse execution on platforms that don't
6709 support it directly can only be done in the replay mode.
6711 When debugging in the reverse direction, @value{GDBN} will work in
6712 replay mode as long as the execution log includes the record for the
6713 previous instruction; otherwise, it will work in record mode, if the
6714 platform supports reverse execution, or stop if not.
6716 For architecture environments that support process record and replay,
6717 @value{GDBN} provides the following commands:
6720 @kindex target record
6721 @kindex target record-full
6722 @kindex target record-btrace
6725 @kindex record btrace
6726 @kindex record btrace bts
6727 @kindex record btrace pt
6733 @kindex rec btrace bts
6734 @kindex rec btrace pt
6737 @item record @var{method}
6738 This command starts the process record and replay target. The
6739 recording method can be specified as parameter. Without a parameter
6740 the command uses the @code{full} recording method. The following
6741 recording methods are available:
6745 Full record/replay recording using @value{GDBN}'s software record and
6746 replay implementation. This method allows replaying and reverse
6749 @item btrace @var{format}
6750 Hardware-supported instruction recording. This method does not record
6751 data. Further, the data is collected in a ring buffer so old data will
6752 be overwritten when the buffer is full. It allows limited reverse
6753 execution. Variables and registers are not available during reverse
6754 execution. In remote debugging, recording continues on disconnect.
6755 Recorded data can be inspected after reconnecting. The recording may
6756 be stopped using @code{record stop}.
6758 The recording format can be specified as parameter. Without a parameter
6759 the command chooses the recording format. The following recording
6760 formats are available:
6764 @cindex branch trace store
6765 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6766 this format, the processor stores a from/to record for each executed
6767 branch in the btrace ring buffer.
6770 @cindex Intel Processor Trace
6771 Use the @dfn{Intel Processor Trace} recording format. In this
6772 format, the processor stores the execution trace in a compressed form
6773 that is afterwards decoded by @value{GDBN}.
6775 The trace can be recorded with very low overhead. The compressed
6776 trace format also allows small trace buffers to already contain a big
6777 number of instructions compared to @acronym{BTS}.
6779 Decoding the recorded execution trace, on the other hand, is more
6780 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6781 increased number of instructions to process. You should increase the
6782 buffer-size with care.
6785 Not all recording formats may be available on all processors.
6788 The process record and replay target can only debug a process that is
6789 already running. Therefore, you need first to start the process with
6790 the @kbd{run} or @kbd{start} commands, and then start the recording
6791 with the @kbd{record @var{method}} command.
6793 @cindex displaced stepping, and process record and replay
6794 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6795 will be automatically disabled when process record and replay target
6796 is started. That's because the process record and replay target
6797 doesn't support displaced stepping.
6799 @cindex non-stop mode, and process record and replay
6800 @cindex asynchronous execution, and process record and replay
6801 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6802 the asynchronous execution mode (@pxref{Background Execution}), not
6803 all recording methods are available. The @code{full} recording method
6804 does not support these two modes.
6809 Stop the process record and replay target. When process record and
6810 replay target stops, the entire execution log will be deleted and the
6811 inferior will either be terminated, or will remain in its final state.
6813 When you stop the process record and replay target in record mode (at
6814 the end of the execution log), the inferior will be stopped at the
6815 next instruction that would have been recorded. In other words, if
6816 you record for a while and then stop recording, the inferior process
6817 will be left in the same state as if the recording never happened.
6819 On the other hand, if the process record and replay target is stopped
6820 while in replay mode (that is, not at the end of the execution log,
6821 but at some earlier point), the inferior process will become ``live''
6822 at that earlier state, and it will then be possible to continue the
6823 usual ``live'' debugging of the process from that state.
6825 When the inferior process exits, or @value{GDBN} detaches from it,
6826 process record and replay target will automatically stop itself.
6830 Go to a specific location in the execution log. There are several
6831 ways to specify the location to go to:
6834 @item record goto begin
6835 @itemx record goto start
6836 Go to the beginning of the execution log.
6838 @item record goto end
6839 Go to the end of the execution log.
6841 @item record goto @var{n}
6842 Go to instruction number @var{n} in the execution log.
6846 @item record save @var{filename}
6847 Save the execution log to a file @file{@var{filename}}.
6848 Default filename is @file{gdb_record.@var{process_id}}, where
6849 @var{process_id} is the process ID of the inferior.
6851 This command may not be available for all recording methods.
6853 @kindex record restore
6854 @item record restore @var{filename}
6855 Restore the execution log from a file @file{@var{filename}}.
6856 File must have been created with @code{record save}.
6858 @kindex set record full
6859 @item set record full insn-number-max @var{limit}
6860 @itemx set record full insn-number-max unlimited
6861 Set the limit of instructions to be recorded for the @code{full}
6862 recording method. Default value is 200000.
6864 If @var{limit} is a positive number, then @value{GDBN} will start
6865 deleting instructions from the log once the number of the record
6866 instructions becomes greater than @var{limit}. For every new recorded
6867 instruction, @value{GDBN} will delete the earliest recorded
6868 instruction to keep the number of recorded instructions at the limit.
6869 (Since deleting recorded instructions loses information, @value{GDBN}
6870 lets you control what happens when the limit is reached, by means of
6871 the @code{stop-at-limit} option, described below.)
6873 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6874 delete recorded instructions from the execution log. The number of
6875 recorded instructions is limited only by the available memory.
6877 @kindex show record full
6878 @item show record full insn-number-max
6879 Show the limit of instructions to be recorded with the @code{full}
6882 @item set record full stop-at-limit
6883 Control the behavior of the @code{full} recording method when the
6884 number of recorded instructions reaches the limit. If ON (the
6885 default), @value{GDBN} will stop when the limit is reached for the
6886 first time and ask you whether you want to stop the inferior or
6887 continue running it and recording the execution log. If you decide
6888 to continue recording, each new recorded instruction will cause the
6889 oldest one to be deleted.
6891 If this option is OFF, @value{GDBN} will automatically delete the
6892 oldest record to make room for each new one, without asking.
6894 @item show record full stop-at-limit
6895 Show the current setting of @code{stop-at-limit}.
6897 @item set record full memory-query
6898 Control the behavior when @value{GDBN} is unable to record memory
6899 changes caused by an instruction for the @code{full} recording method.
6900 If ON, @value{GDBN} will query whether to stop the inferior in that
6903 If this option is OFF (the default), @value{GDBN} will automatically
6904 ignore the effect of such instructions on memory. Later, when
6905 @value{GDBN} replays this execution log, it will mark the log of this
6906 instruction as not accessible, and it will not affect the replay
6909 @item show record full memory-query
6910 Show the current setting of @code{memory-query}.
6912 @kindex set record btrace
6913 The @code{btrace} record target does not trace data. As a
6914 convenience, when replaying, @value{GDBN} reads read-only memory off
6915 the live program directly, assuming that the addresses of the
6916 read-only areas don't change. This for example makes it possible to
6917 disassemble code while replaying, but not to print variables.
6918 In some cases, being able to inspect variables might be useful.
6919 You can use the following command for that:
6921 @item set record btrace replay-memory-access
6922 Control the behavior of the @code{btrace} recording method when
6923 accessing memory during replay. If @code{read-only} (the default),
6924 @value{GDBN} will only allow accesses to read-only memory.
6925 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6926 and to read-write memory. Beware that the accessed memory corresponds
6927 to the live target and not necessarily to the current replay
6930 @kindex show record btrace
6931 @item show record btrace replay-memory-access
6932 Show the current setting of @code{replay-memory-access}.
6934 @kindex set record btrace bts
6935 @item set record btrace bts buffer-size @var{size}
6936 @itemx set record btrace bts buffer-size unlimited
6937 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6938 format. Default is 64KB.
6940 If @var{size} is a positive number, then @value{GDBN} will try to
6941 allocate a buffer of at least @var{size} bytes for each new thread
6942 that uses the btrace recording method and the @acronym{BTS} format.
6943 The actually obtained buffer size may differ from the requested
6944 @var{size}. Use the @code{info record} command to see the actual
6945 buffer size for each thread that uses the btrace recording method and
6946 the @acronym{BTS} format.
6948 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6949 allocate a buffer of 4MB.
6951 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6952 also need longer to process the branch trace data before it can be used.
6954 @item show record btrace bts buffer-size @var{size}
6955 Show the current setting of the requested ring buffer size for branch
6956 tracing in @acronym{BTS} format.
6958 @kindex set record btrace pt
6959 @item set record btrace pt buffer-size @var{size}
6960 @itemx set record btrace pt buffer-size unlimited
6961 Set the requested ring buffer size for branch tracing in Intel
6962 Processor Trace format. Default is 16KB.
6964 If @var{size} is a positive number, then @value{GDBN} will try to
6965 allocate a buffer of at least @var{size} bytes for each new thread
6966 that uses the btrace recording method and the Intel Processor Trace
6967 format. The actually obtained buffer size may differ from the
6968 requested @var{size}. Use the @code{info record} command to see the
6969 actual buffer size for each thread.
6971 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6972 allocate a buffer of 4MB.
6974 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6975 also need longer to process the branch trace data before it can be used.
6977 @item show record btrace pt buffer-size @var{size}
6978 Show the current setting of the requested ring buffer size for branch
6979 tracing in Intel Processor Trace format.
6983 Show various statistics about the recording depending on the recording
6988 For the @code{full} recording method, it shows the state of process
6989 record and its in-memory execution log buffer, including:
6993 Whether in record mode or replay mode.
6995 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6997 Highest recorded instruction number.
6999 Current instruction about to be replayed (if in replay mode).
7001 Number of instructions contained in the execution log.
7003 Maximum number of instructions that may be contained in the execution log.
7007 For the @code{btrace} recording method, it shows:
7013 Number of instructions that have been recorded.
7015 Number of blocks of sequential control-flow formed by the recorded
7018 Whether in record mode or replay mode.
7021 For the @code{bts} recording format, it also shows:
7024 Size of the perf ring buffer.
7027 For the @code{pt} recording format, it also shows:
7030 Size of the perf ring buffer.
7034 @kindex record delete
7037 When record target runs in replay mode (``in the past''), delete the
7038 subsequent execution log and begin to record a new execution log starting
7039 from the current address. This means you will abandon the previously
7040 recorded ``future'' and begin recording a new ``future''.
7042 @kindex record instruction-history
7043 @kindex rec instruction-history
7044 @item record instruction-history
7045 Disassembles instructions from the recorded execution log. By
7046 default, ten instructions are disassembled. This can be changed using
7047 the @code{set record instruction-history-size} command. Instructions
7048 are printed in execution order.
7050 It can also print mixed source+disassembly if you specify the the
7051 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7052 as well as in symbolic form by specifying the @code{/r} modifier.
7054 The current position marker is printed for the instruction at the
7055 current program counter value. This instruction can appear multiple
7056 times in the trace and the current position marker will be printed
7057 every time. To omit the current position marker, specify the
7060 To better align the printed instructions when the trace contains
7061 instructions from more than one function, the function name may be
7062 omitted by specifying the @code{/f} modifier.
7064 Speculatively executed instructions are prefixed with @samp{?}. This
7065 feature is not available for all recording formats.
7067 There are several ways to specify what part of the execution log to
7071 @item record instruction-history @var{insn}
7072 Disassembles ten instructions starting from instruction number
7075 @item record instruction-history @var{insn}, +/-@var{n}
7076 Disassembles @var{n} instructions around instruction number
7077 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7078 @var{n} instructions after instruction number @var{insn}. If
7079 @var{n} is preceded with @code{-}, disassembles @var{n}
7080 instructions before instruction number @var{insn}.
7082 @item record instruction-history
7083 Disassembles ten more instructions after the last disassembly.
7085 @item record instruction-history -
7086 Disassembles ten more instructions before the last disassembly.
7088 @item record instruction-history @var{begin}, @var{end}
7089 Disassembles instructions beginning with instruction number
7090 @var{begin} until instruction number @var{end}. The instruction
7091 number @var{end} is included.
7094 This command may not be available for all recording methods.
7097 @item set record instruction-history-size @var{size}
7098 @itemx set record instruction-history-size unlimited
7099 Define how many instructions to disassemble in the @code{record
7100 instruction-history} command. The default value is 10.
7101 A @var{size} of @code{unlimited} means unlimited instructions.
7104 @item show record instruction-history-size
7105 Show how many instructions to disassemble in the @code{record
7106 instruction-history} command.
7108 @kindex record function-call-history
7109 @kindex rec function-call-history
7110 @item record function-call-history
7111 Prints the execution history at function granularity. It prints one
7112 line for each sequence of instructions that belong to the same
7113 function giving the name of that function, the source lines
7114 for this instruction sequence (if the @code{/l} modifier is
7115 specified), and the instructions numbers that form the sequence (if
7116 the @code{/i} modifier is specified). The function names are indented
7117 to reflect the call stack depth if the @code{/c} modifier is
7118 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7122 (@value{GDBP}) @b{list 1, 10}
7133 (@value{GDBP}) @b{record function-call-history /ilc}
7134 1 bar inst 1,4 at foo.c:6,8
7135 2 foo inst 5,10 at foo.c:2,3
7136 3 bar inst 11,13 at foo.c:9,10
7139 By default, ten lines are printed. This can be changed using the
7140 @code{set record function-call-history-size} command. Functions are
7141 printed in execution order. There are several ways to specify what
7145 @item record function-call-history @var{func}
7146 Prints ten functions starting from function number @var{func}.
7148 @item record function-call-history @var{func}, +/-@var{n}
7149 Prints @var{n} functions around function number @var{func}. If
7150 @var{n} is preceded with @code{+}, prints @var{n} functions after
7151 function number @var{func}. If @var{n} is preceded with @code{-},
7152 prints @var{n} functions before function number @var{func}.
7154 @item record function-call-history
7155 Prints ten more functions after the last ten-line print.
7157 @item record function-call-history -
7158 Prints ten more functions before the last ten-line print.
7160 @item record function-call-history @var{begin}, @var{end}
7161 Prints functions beginning with function number @var{begin} until
7162 function number @var{end}. The function number @var{end} is included.
7165 This command may not be available for all recording methods.
7167 @item set record function-call-history-size @var{size}
7168 @itemx set record function-call-history-size unlimited
7169 Define how many lines to print in the
7170 @code{record function-call-history} command. The default value is 10.
7171 A size of @code{unlimited} means unlimited lines.
7173 @item show record function-call-history-size
7174 Show how many lines to print in the
7175 @code{record function-call-history} command.
7180 @chapter Examining the Stack
7182 When your program has stopped, the first thing you need to know is where it
7183 stopped and how it got there.
7186 Each time your program performs a function call, information about the call
7188 That information includes the location of the call in your program,
7189 the arguments of the call,
7190 and the local variables of the function being called.
7191 The information is saved in a block of data called a @dfn{stack frame}.
7192 The stack frames are allocated in a region of memory called the @dfn{call
7195 When your program stops, the @value{GDBN} commands for examining the
7196 stack allow you to see all of this information.
7198 @cindex selected frame
7199 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7200 @value{GDBN} commands refer implicitly to the selected frame. In
7201 particular, whenever you ask @value{GDBN} for the value of a variable in
7202 your program, the value is found in the selected frame. There are
7203 special @value{GDBN} commands to select whichever frame you are
7204 interested in. @xref{Selection, ,Selecting a Frame}.
7206 When your program stops, @value{GDBN} automatically selects the
7207 currently executing frame and describes it briefly, similar to the
7208 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7211 * Frames:: Stack frames
7212 * Backtrace:: Backtraces
7213 * Selection:: Selecting a frame
7214 * Frame Info:: Information on a frame
7215 * Frame Filter Management:: Managing frame filters
7220 @section Stack Frames
7222 @cindex frame, definition
7224 The call stack is divided up into contiguous pieces called @dfn{stack
7225 frames}, or @dfn{frames} for short; each frame is the data associated
7226 with one call to one function. The frame contains the arguments given
7227 to the function, the function's local variables, and the address at
7228 which the function is executing.
7230 @cindex initial frame
7231 @cindex outermost frame
7232 @cindex innermost frame
7233 When your program is started, the stack has only one frame, that of the
7234 function @code{main}. This is called the @dfn{initial} frame or the
7235 @dfn{outermost} frame. Each time a function is called, a new frame is
7236 made. Each time a function returns, the frame for that function invocation
7237 is eliminated. If a function is recursive, there can be many frames for
7238 the same function. The frame for the function in which execution is
7239 actually occurring is called the @dfn{innermost} frame. This is the most
7240 recently created of all the stack frames that still exist.
7242 @cindex frame pointer
7243 Inside your program, stack frames are identified by their addresses. A
7244 stack frame consists of many bytes, each of which has its own address; each
7245 kind of computer has a convention for choosing one byte whose
7246 address serves as the address of the frame. Usually this address is kept
7247 in a register called the @dfn{frame pointer register}
7248 (@pxref{Registers, $fp}) while execution is going on in that frame.
7250 @cindex frame number
7251 @value{GDBN} assigns numbers to all existing stack frames, starting with
7252 zero for the innermost frame, one for the frame that called it,
7253 and so on upward. These numbers do not really exist in your program;
7254 they are assigned by @value{GDBN} to give you a way of designating stack
7255 frames in @value{GDBN} commands.
7257 @c The -fomit-frame-pointer below perennially causes hbox overflow
7258 @c underflow problems.
7259 @cindex frameless execution
7260 Some compilers provide a way to compile functions so that they operate
7261 without stack frames. (For example, the @value{NGCC} option
7263 @samp{-fomit-frame-pointer}
7265 generates functions without a frame.)
7266 This is occasionally done with heavily used library functions to save
7267 the frame setup time. @value{GDBN} has limited facilities for dealing
7268 with these function invocations. If the innermost function invocation
7269 has no stack frame, @value{GDBN} nevertheless regards it as though
7270 it had a separate frame, which is numbered zero as usual, allowing
7271 correct tracing of the function call chain. However, @value{GDBN} has
7272 no provision for frameless functions elsewhere in the stack.
7278 @cindex call stack traces
7279 A backtrace is a summary of how your program got where it is. It shows one
7280 line per frame, for many frames, starting with the currently executing
7281 frame (frame zero), followed by its caller (frame one), and on up the
7284 @anchor{backtrace-command}
7287 @kindex bt @r{(@code{backtrace})}
7290 Print a backtrace of the entire stack: one line per frame for all
7291 frames in the stack.
7293 You can stop the backtrace at any time by typing the system interrupt
7294 character, normally @kbd{Ctrl-c}.
7296 @item backtrace @var{n}
7298 Similar, but print only the innermost @var{n} frames.
7300 @item backtrace -@var{n}
7302 Similar, but print only the outermost @var{n} frames.
7304 @item backtrace full
7306 @itemx bt full @var{n}
7307 @itemx bt full -@var{n}
7308 Print the values of the local variables also. As described above,
7309 @var{n} specifies the number of frames to print.
7311 @item backtrace no-filters
7312 @itemx bt no-filters
7313 @itemx bt no-filters @var{n}
7314 @itemx bt no-filters -@var{n}
7315 @itemx bt no-filters full
7316 @itemx bt no-filters full @var{n}
7317 @itemx bt no-filters full -@var{n}
7318 Do not run Python frame filters on this backtrace. @xref{Frame
7319 Filter API}, for more information. Additionally use @ref{disable
7320 frame-filter all} to turn off all frame filters. This is only
7321 relevant when @value{GDBN} has been configured with @code{Python}
7327 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7328 are additional aliases for @code{backtrace}.
7330 @cindex multiple threads, backtrace
7331 In a multi-threaded program, @value{GDBN} by default shows the
7332 backtrace only for the current thread. To display the backtrace for
7333 several or all of the threads, use the command @code{thread apply}
7334 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7335 apply all backtrace}, @value{GDBN} will display the backtrace for all
7336 the threads; this is handy when you debug a core dump of a
7337 multi-threaded program.
7339 Each line in the backtrace shows the frame number and the function name.
7340 The program counter value is also shown---unless you use @code{set
7341 print address off}. The backtrace also shows the source file name and
7342 line number, as well as the arguments to the function. The program
7343 counter value is omitted if it is at the beginning of the code for that
7346 Here is an example of a backtrace. It was made with the command
7347 @samp{bt 3}, so it shows the innermost three frames.
7351 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7353 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7354 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7356 (More stack frames follow...)
7361 The display for frame zero does not begin with a program counter
7362 value, indicating that your program has stopped at the beginning of the
7363 code for line @code{993} of @code{builtin.c}.
7366 The value of parameter @code{data} in frame 1 has been replaced by
7367 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7368 only if it is a scalar (integer, pointer, enumeration, etc). See command
7369 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7370 on how to configure the way function parameter values are printed.
7372 @cindex optimized out, in backtrace
7373 @cindex function call arguments, optimized out
7374 If your program was compiled with optimizations, some compilers will
7375 optimize away arguments passed to functions if those arguments are
7376 never used after the call. Such optimizations generate code that
7377 passes arguments through registers, but doesn't store those arguments
7378 in the stack frame. @value{GDBN} has no way of displaying such
7379 arguments in stack frames other than the innermost one. Here's what
7380 such a backtrace might look like:
7384 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7386 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7387 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7389 (More stack frames follow...)
7394 The values of arguments that were not saved in their stack frames are
7395 shown as @samp{<optimized out>}.
7397 If you need to display the values of such optimized-out arguments,
7398 either deduce that from other variables whose values depend on the one
7399 you are interested in, or recompile without optimizations.
7401 @cindex backtrace beyond @code{main} function
7402 @cindex program entry point
7403 @cindex startup code, and backtrace
7404 Most programs have a standard user entry point---a place where system
7405 libraries and startup code transition into user code. For C this is
7406 @code{main}@footnote{
7407 Note that embedded programs (the so-called ``free-standing''
7408 environment) are not required to have a @code{main} function as the
7409 entry point. They could even have multiple entry points.}.
7410 When @value{GDBN} finds the entry function in a backtrace
7411 it will terminate the backtrace, to avoid tracing into highly
7412 system-specific (and generally uninteresting) code.
7414 If you need to examine the startup code, or limit the number of levels
7415 in a backtrace, you can change this behavior:
7418 @item set backtrace past-main
7419 @itemx set backtrace past-main on
7420 @kindex set backtrace
7421 Backtraces will continue past the user entry point.
7423 @item set backtrace past-main off
7424 Backtraces will stop when they encounter the user entry point. This is the
7427 @item show backtrace past-main
7428 @kindex show backtrace
7429 Display the current user entry point backtrace policy.
7431 @item set backtrace past-entry
7432 @itemx set backtrace past-entry on
7433 Backtraces will continue past the internal entry point of an application.
7434 This entry point is encoded by the linker when the application is built,
7435 and is likely before the user entry point @code{main} (or equivalent) is called.
7437 @item set backtrace past-entry off
7438 Backtraces will stop when they encounter the internal entry point of an
7439 application. This is the default.
7441 @item show backtrace past-entry
7442 Display the current internal entry point backtrace policy.
7444 @item set backtrace limit @var{n}
7445 @itemx set backtrace limit 0
7446 @itemx set backtrace limit unlimited
7447 @cindex backtrace limit
7448 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7449 or zero means unlimited levels.
7451 @item show backtrace limit
7452 Display the current limit on backtrace levels.
7455 You can control how file names are displayed.
7458 @item set filename-display
7459 @itemx set filename-display relative
7460 @cindex filename-display
7461 Display file names relative to the compilation directory. This is the default.
7463 @item set filename-display basename
7464 Display only basename of a filename.
7466 @item set filename-display absolute
7467 Display an absolute filename.
7469 @item show filename-display
7470 Show the current way to display filenames.
7474 @section Selecting a Frame
7476 Most commands for examining the stack and other data in your program work on
7477 whichever stack frame is selected at the moment. Here are the commands for
7478 selecting a stack frame; all of them finish by printing a brief description
7479 of the stack frame just selected.
7482 @kindex frame@r{, selecting}
7483 @kindex f @r{(@code{frame})}
7486 Select frame number @var{n}. Recall that frame zero is the innermost
7487 (currently executing) frame, frame one is the frame that called the
7488 innermost one, and so on. The highest-numbered frame is the one for
7491 @item frame @var{stack-addr} [ @var{pc-addr} ]
7492 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7493 Select the frame at address @var{stack-addr}. This is useful mainly if the
7494 chaining of stack frames has been damaged by a bug, making it
7495 impossible for @value{GDBN} to assign numbers properly to all frames. In
7496 addition, this can be useful when your program has multiple stacks and
7497 switches between them. The optional @var{pc-addr} can also be given to
7498 specify the value of PC for the stack frame.
7502 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7503 numbers @var{n}, this advances toward the outermost frame, to higher
7504 frame numbers, to frames that have existed longer.
7507 @kindex do @r{(@code{down})}
7509 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7510 positive numbers @var{n}, this advances toward the innermost frame, to
7511 lower frame numbers, to frames that were created more recently.
7512 You may abbreviate @code{down} as @code{do}.
7515 All of these commands end by printing two lines of output describing the
7516 frame. The first line shows the frame number, the function name, the
7517 arguments, and the source file and line number of execution in that
7518 frame. The second line shows the text of that source line.
7526 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7528 10 read_input_file (argv[i]);
7532 After such a printout, the @code{list} command with no arguments
7533 prints ten lines centered on the point of execution in the frame.
7534 You can also edit the program at the point of execution with your favorite
7535 editing program by typing @code{edit}.
7536 @xref{List, ,Printing Source Lines},
7540 @kindex select-frame
7542 The @code{select-frame} command is a variant of @code{frame} that does
7543 not display the new frame after selecting it. This command is
7544 intended primarily for use in @value{GDBN} command scripts, where the
7545 output might be unnecessary and distracting.
7547 @kindex down-silently
7549 @item up-silently @var{n}
7550 @itemx down-silently @var{n}
7551 These two commands are variants of @code{up} and @code{down},
7552 respectively; they differ in that they do their work silently, without
7553 causing display of the new frame. They are intended primarily for use
7554 in @value{GDBN} command scripts, where the output might be unnecessary and
7559 @section Information About a Frame
7561 There are several other commands to print information about the selected
7567 When used without any argument, this command does not change which
7568 frame is selected, but prints a brief description of the currently
7569 selected stack frame. It can be abbreviated @code{f}. With an
7570 argument, this command is used to select a stack frame.
7571 @xref{Selection, ,Selecting a Frame}.
7574 @kindex info f @r{(@code{info frame})}
7577 This command prints a verbose description of the selected stack frame,
7582 the address of the frame
7584 the address of the next frame down (called by this frame)
7586 the address of the next frame up (caller of this frame)
7588 the language in which the source code corresponding to this frame is written
7590 the address of the frame's arguments
7592 the address of the frame's local variables
7594 the program counter saved in it (the address of execution in the caller frame)
7596 which registers were saved in the frame
7599 @noindent The verbose description is useful when
7600 something has gone wrong that has made the stack format fail to fit
7601 the usual conventions.
7603 @item info frame @var{addr}
7604 @itemx info f @var{addr}
7605 Print a verbose description of the frame at address @var{addr}, without
7606 selecting that frame. The selected frame remains unchanged by this
7607 command. This requires the same kind of address (more than one for some
7608 architectures) that you specify in the @code{frame} command.
7609 @xref{Selection, ,Selecting a Frame}.
7613 Print the arguments of the selected frame, each on a separate line.
7617 Print the local variables of the selected frame, each on a separate
7618 line. These are all variables (declared either static or automatic)
7619 accessible at the point of execution of the selected frame.
7623 @node Frame Filter Management
7624 @section Management of Frame Filters.
7625 @cindex managing frame filters
7627 Frame filters are Python based utilities to manage and decorate the
7628 output of frames. @xref{Frame Filter API}, for further information.
7630 Managing frame filters is performed by several commands available
7631 within @value{GDBN}, detailed here.
7634 @kindex info frame-filter
7635 @item info frame-filter
7636 Print a list of installed frame filters from all dictionaries, showing
7637 their name, priority and enabled status.
7639 @kindex disable frame-filter
7640 @anchor{disable frame-filter all}
7641 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7642 Disable a frame filter in the dictionary matching
7643 @var{filter-dictionary} and @var{filter-name}. The
7644 @var{filter-dictionary} may be @code{all}, @code{global},
7645 @code{progspace}, or the name of the object file where the frame filter
7646 dictionary resides. When @code{all} is specified, all frame filters
7647 across all dictionaries are disabled. The @var{filter-name} is the name
7648 of the frame filter and is used when @code{all} is not the option for
7649 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7650 may be enabled again later.
7652 @kindex enable frame-filter
7653 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7654 Enable a frame filter in the dictionary matching
7655 @var{filter-dictionary} and @var{filter-name}. The
7656 @var{filter-dictionary} may be @code{all}, @code{global},
7657 @code{progspace} or the name of the object file where the frame filter
7658 dictionary resides. When @code{all} is specified, all frame filters across
7659 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7660 filter and is used when @code{all} is not the option for
7661 @var{filter-dictionary}.
7666 (gdb) info frame-filter
7668 global frame-filters:
7669 Priority Enabled Name
7670 1000 No PrimaryFunctionFilter
7673 progspace /build/test frame-filters:
7674 Priority Enabled Name
7675 100 Yes ProgspaceFilter
7677 objfile /build/test frame-filters:
7678 Priority Enabled Name
7679 999 Yes BuildProgra Filter
7681 (gdb) disable frame-filter /build/test BuildProgramFilter
7682 (gdb) info frame-filter
7684 global frame-filters:
7685 Priority Enabled Name
7686 1000 No PrimaryFunctionFilter
7689 progspace /build/test frame-filters:
7690 Priority Enabled Name
7691 100 Yes ProgspaceFilter
7693 objfile /build/test frame-filters:
7694 Priority Enabled Name
7695 999 No BuildProgramFilter
7697 (gdb) enable frame-filter global PrimaryFunctionFilter
7698 (gdb) info frame-filter
7700 global frame-filters:
7701 Priority Enabled Name
7702 1000 Yes PrimaryFunctionFilter
7705 progspace /build/test frame-filters:
7706 Priority Enabled Name
7707 100 Yes ProgspaceFilter
7709 objfile /build/test frame-filters:
7710 Priority Enabled Name
7711 999 No BuildProgramFilter
7714 @kindex set frame-filter priority
7715 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7716 Set the @var{priority} of a frame filter in the dictionary matching
7717 @var{filter-dictionary}, and the frame filter name matching
7718 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7719 @code{progspace} or the name of the object file where the frame filter
7720 dictionary resides. The @var{priority} is an integer.
7722 @kindex show frame-filter priority
7723 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7724 Show the @var{priority} of a frame filter in the dictionary matching
7725 @var{filter-dictionary}, and the frame filter name matching
7726 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7727 @code{progspace} or the name of the object file where the frame filter
7733 (gdb) info frame-filter
7735 global frame-filters:
7736 Priority Enabled Name
7737 1000 Yes PrimaryFunctionFilter
7740 progspace /build/test frame-filters:
7741 Priority Enabled Name
7742 100 Yes ProgspaceFilter
7744 objfile /build/test frame-filters:
7745 Priority Enabled Name
7746 999 No BuildProgramFilter
7748 (gdb) set frame-filter priority global Reverse 50
7749 (gdb) info frame-filter
7751 global frame-filters:
7752 Priority Enabled Name
7753 1000 Yes PrimaryFunctionFilter
7756 progspace /build/test frame-filters:
7757 Priority Enabled Name
7758 100 Yes ProgspaceFilter
7760 objfile /build/test frame-filters:
7761 Priority Enabled Name
7762 999 No BuildProgramFilter
7767 @chapter Examining Source Files
7769 @value{GDBN} can print parts of your program's source, since the debugging
7770 information recorded in the program tells @value{GDBN} what source files were
7771 used to build it. When your program stops, @value{GDBN} spontaneously prints
7772 the line where it stopped. Likewise, when you select a stack frame
7773 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7774 execution in that frame has stopped. You can print other portions of
7775 source files by explicit command.
7777 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7778 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7779 @value{GDBN} under @sc{gnu} Emacs}.
7782 * List:: Printing source lines
7783 * Specify Location:: How to specify code locations
7784 * Edit:: Editing source files
7785 * Search:: Searching source files
7786 * Source Path:: Specifying source directories
7787 * Machine Code:: Source and machine code
7791 @section Printing Source Lines
7794 @kindex l @r{(@code{list})}
7795 To print lines from a source file, use the @code{list} command
7796 (abbreviated @code{l}). By default, ten lines are printed.
7797 There are several ways to specify what part of the file you want to
7798 print; see @ref{Specify Location}, for the full list.
7800 Here are the forms of the @code{list} command most commonly used:
7803 @item list @var{linenum}
7804 Print lines centered around line number @var{linenum} in the
7805 current source file.
7807 @item list @var{function}
7808 Print lines centered around the beginning of function
7812 Print more lines. If the last lines printed were printed with a
7813 @code{list} command, this prints lines following the last lines
7814 printed; however, if the last line printed was a solitary line printed
7815 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7816 Stack}), this prints lines centered around that line.
7819 Print lines just before the lines last printed.
7822 @cindex @code{list}, how many lines to display
7823 By default, @value{GDBN} prints ten source lines with any of these forms of
7824 the @code{list} command. You can change this using @code{set listsize}:
7827 @kindex set listsize
7828 @item set listsize @var{count}
7829 @itemx set listsize unlimited
7830 Make the @code{list} command display @var{count} source lines (unless
7831 the @code{list} argument explicitly specifies some other number).
7832 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7834 @kindex show listsize
7836 Display the number of lines that @code{list} prints.
7839 Repeating a @code{list} command with @key{RET} discards the argument,
7840 so it is equivalent to typing just @code{list}. This is more useful
7841 than listing the same lines again. An exception is made for an
7842 argument of @samp{-}; that argument is preserved in repetition so that
7843 each repetition moves up in the source file.
7845 In general, the @code{list} command expects you to supply zero, one or two
7846 @dfn{locations}. Locations specify source lines; there are several ways
7847 of writing them (@pxref{Specify Location}), but the effect is always
7848 to specify some source line.
7850 Here is a complete description of the possible arguments for @code{list}:
7853 @item list @var{location}
7854 Print lines centered around the line specified by @var{location}.
7856 @item list @var{first},@var{last}
7857 Print lines from @var{first} to @var{last}. Both arguments are
7858 locations. When a @code{list} command has two locations, and the
7859 source file of the second location is omitted, this refers to
7860 the same source file as the first location.
7862 @item list ,@var{last}
7863 Print lines ending with @var{last}.
7865 @item list @var{first},
7866 Print lines starting with @var{first}.
7869 Print lines just after the lines last printed.
7872 Print lines just before the lines last printed.
7875 As described in the preceding table.
7878 @node Specify Location
7879 @section Specifying a Location
7880 @cindex specifying location
7882 @cindex source location
7885 * Linespec Locations:: Linespec locations
7886 * Explicit Locations:: Explicit locations
7887 * Address Locations:: Address locations
7890 Several @value{GDBN} commands accept arguments that specify a location
7891 of your program's code. Since @value{GDBN} is a source-level
7892 debugger, a location usually specifies some line in the source code.
7893 Locations may be specified using three different formats:
7894 linespec locations, explicit locations, or address locations.
7896 @node Linespec Locations
7897 @subsection Linespec Locations
7898 @cindex linespec locations
7900 A @dfn{linespec} is a colon-separated list of source location parameters such
7901 as file name, function name, etc. Here are all the different ways of
7902 specifying a linespec:
7906 Specifies the line number @var{linenum} of the current source file.
7909 @itemx +@var{offset}
7910 Specifies the line @var{offset} lines before or after the @dfn{current
7911 line}. For the @code{list} command, the current line is the last one
7912 printed; for the breakpoint commands, this is the line at which
7913 execution stopped in the currently selected @dfn{stack frame}
7914 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7915 used as the second of the two linespecs in a @code{list} command,
7916 this specifies the line @var{offset} lines up or down from the first
7919 @item @var{filename}:@var{linenum}
7920 Specifies the line @var{linenum} in the source file @var{filename}.
7921 If @var{filename} is a relative file name, then it will match any
7922 source file name with the same trailing components. For example, if
7923 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7924 name of @file{/build/trunk/gcc/expr.c}, but not
7925 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7927 @item @var{function}
7928 Specifies the line that begins the body of the function @var{function}.
7929 For example, in C, this is the line with the open brace.
7931 By default, in C@t{++} and Ada, @var{function} is interpreted as
7932 specifying all functions named @var{function} in all scopes. For
7933 C@t{++}, this means in all namespaces and classes. For Ada, this
7934 means in all packages.
7936 For example, assuming a program with C@t{++} symbols named
7937 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
7938 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
7940 Commands that accept a linespec let you override this with the
7941 @code{-qualified} option. For example, @w{@kbd{break -qualified
7942 func}} sets a breakpoint on a free-function named @code{func} ignoring
7943 any C@t{++} class methods and namespace functions called @code{func}.
7945 @xref{Explicit Locations}.
7947 @item @var{function}:@var{label}
7948 Specifies the line where @var{label} appears in @var{function}.
7950 @item @var{filename}:@var{function}
7951 Specifies the line that begins the body of the function @var{function}
7952 in the file @var{filename}. You only need the file name with a
7953 function name to avoid ambiguity when there are identically named
7954 functions in different source files.
7957 Specifies the line at which the label named @var{label} appears
7958 in the function corresponding to the currently selected stack frame.
7959 If there is no current selected stack frame (for instance, if the inferior
7960 is not running), then @value{GDBN} will not search for a label.
7962 @cindex breakpoint at static probe point
7963 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7964 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7965 applications to embed static probes. @xref{Static Probe Points}, for more
7966 information on finding and using static probes. This form of linespec
7967 specifies the location of such a static probe.
7969 If @var{objfile} is given, only probes coming from that shared library
7970 or executable matching @var{objfile} as a regular expression are considered.
7971 If @var{provider} is given, then only probes from that provider are considered.
7972 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7973 each one of those probes.
7976 @node Explicit Locations
7977 @subsection Explicit Locations
7978 @cindex explicit locations
7980 @dfn{Explicit locations} allow the user to directly specify the source
7981 location's parameters using option-value pairs.
7983 Explicit locations are useful when several functions, labels, or
7984 file names have the same name (base name for files) in the program's
7985 sources. In these cases, explicit locations point to the source
7986 line you meant more accurately and unambiguously. Also, using
7987 explicit locations might be faster in large programs.
7989 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7990 defined in the file named @file{foo} or the label @code{bar} in a function
7991 named @code{foo}. @value{GDBN} must search either the file system or
7992 the symbol table to know.
7994 The list of valid explicit location options is summarized in the
7998 @item -source @var{filename}
7999 The value specifies the source file name. To differentiate between
8000 files with the same base name, prepend as many directories as is necessary
8001 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8002 @value{GDBN} will use the first file it finds with the given base
8003 name. This option requires the use of either @code{-function} or @code{-line}.
8005 @item -function @var{function}
8006 The value specifies the name of a function. Operations
8007 on function locations unmodified by other options (such as @code{-label}
8008 or @code{-line}) refer to the line that begins the body of the function.
8009 In C, for example, this is the line with the open brace.
8011 By default, in C@t{++} and Ada, @var{function} is interpreted as
8012 specifying all functions named @var{function} in all scopes. For
8013 C@t{++}, this means in all namespaces and classes. For Ada, this
8014 means in all packages.
8016 For example, assuming a program with C@t{++} symbols named
8017 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8018 -function func}} and @w{@kbd{break -function B::func}} set a
8019 breakpoint on both symbols.
8021 You can use the @kbd{-qualified} flag to override this (see below).
8025 This flag makes @value{GDBN} interpret a function name specified with
8026 @kbd{-function} as a complete fully-qualified name.
8028 For example, assuming a C@t{++} program with symbols named
8029 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8030 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8032 (Note: the @kbd{-qualified} option can precede a linespec as well
8033 (@pxref{Linespec Locations}), so the particular example above could be
8034 simplified as @w{@kbd{break -qualified B::func}}.)
8036 @item -label @var{label}
8037 The value specifies the name of a label. When the function
8038 name is not specified, the label is searched in the function of the currently
8039 selected stack frame.
8041 @item -line @var{number}
8042 The value specifies a line offset for the location. The offset may either
8043 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8044 the command. When specified without any other options, the line offset is
8045 relative to the current line.
8048 Explicit location options may be abbreviated by omitting any non-unique
8049 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8051 @node Address Locations
8052 @subsection Address Locations
8053 @cindex address locations
8055 @dfn{Address locations} indicate a specific program address. They have
8056 the generalized form *@var{address}.
8058 For line-oriented commands, such as @code{list} and @code{edit}, this
8059 specifies a source line that contains @var{address}. For @code{break} and
8060 other breakpoint-oriented commands, this can be used to set breakpoints in
8061 parts of your program which do not have debugging information or
8064 Here @var{address} may be any expression valid in the current working
8065 language (@pxref{Languages, working language}) that specifies a code
8066 address. In addition, as a convenience, @value{GDBN} extends the
8067 semantics of expressions used in locations to cover several situations
8068 that frequently occur during debugging. Here are the various forms
8072 @item @var{expression}
8073 Any expression valid in the current working language.
8075 @item @var{funcaddr}
8076 An address of a function or procedure derived from its name. In C,
8077 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8078 simply the function's name @var{function} (and actually a special case
8079 of a valid expression). In Pascal and Modula-2, this is
8080 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8081 (although the Pascal form also works).
8083 This form specifies the address of the function's first instruction,
8084 before the stack frame and arguments have been set up.
8086 @item '@var{filename}':@var{funcaddr}
8087 Like @var{funcaddr} above, but also specifies the name of the source
8088 file explicitly. This is useful if the name of the function does not
8089 specify the function unambiguously, e.g., if there are several
8090 functions with identical names in different source files.
8094 @section Editing Source Files
8095 @cindex editing source files
8098 @kindex e @r{(@code{edit})}
8099 To edit the lines in a source file, use the @code{edit} command.
8100 The editing program of your choice
8101 is invoked with the current line set to
8102 the active line in the program.
8103 Alternatively, there are several ways to specify what part of the file you
8104 want to print if you want to see other parts of the program:
8107 @item edit @var{location}
8108 Edit the source file specified by @code{location}. Editing starts at
8109 that @var{location}, e.g., at the specified source line of the
8110 specified file. @xref{Specify Location}, for all the possible forms
8111 of the @var{location} argument; here are the forms of the @code{edit}
8112 command most commonly used:
8115 @item edit @var{number}
8116 Edit the current source file with @var{number} as the active line number.
8118 @item edit @var{function}
8119 Edit the file containing @var{function} at the beginning of its definition.
8124 @subsection Choosing your Editor
8125 You can customize @value{GDBN} to use any editor you want
8127 The only restriction is that your editor (say @code{ex}), recognizes the
8128 following command-line syntax:
8130 ex +@var{number} file
8132 The optional numeric value +@var{number} specifies the number of the line in
8133 the file where to start editing.}.
8134 By default, it is @file{@value{EDITOR}}, but you can change this
8135 by setting the environment variable @code{EDITOR} before using
8136 @value{GDBN}. For example, to configure @value{GDBN} to use the
8137 @code{vi} editor, you could use these commands with the @code{sh} shell:
8143 or in the @code{csh} shell,
8145 setenv EDITOR /usr/bin/vi
8150 @section Searching Source Files
8151 @cindex searching source files
8153 There are two commands for searching through the current source file for a
8158 @kindex forward-search
8159 @kindex fo @r{(@code{forward-search})}
8160 @item forward-search @var{regexp}
8161 @itemx search @var{regexp}
8162 The command @samp{forward-search @var{regexp}} checks each line,
8163 starting with the one following the last line listed, for a match for
8164 @var{regexp}. It lists the line that is found. You can use the
8165 synonym @samp{search @var{regexp}} or abbreviate the command name as
8168 @kindex reverse-search
8169 @item reverse-search @var{regexp}
8170 The command @samp{reverse-search @var{regexp}} checks each line, starting
8171 with the one before the last line listed and going backward, for a match
8172 for @var{regexp}. It lists the line that is found. You can abbreviate
8173 this command as @code{rev}.
8177 @section Specifying Source Directories
8180 @cindex directories for source files
8181 Executable programs sometimes do not record the directories of the source
8182 files from which they were compiled, just the names. Even when they do,
8183 the directories could be moved between the compilation and your debugging
8184 session. @value{GDBN} has a list of directories to search for source files;
8185 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8186 it tries all the directories in the list, in the order they are present
8187 in the list, until it finds a file with the desired name.
8189 For example, suppose an executable references the file
8190 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8191 @file{/mnt/cross}. The file is first looked up literally; if this
8192 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8193 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8194 message is printed. @value{GDBN} does not look up the parts of the
8195 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8196 Likewise, the subdirectories of the source path are not searched: if
8197 the source path is @file{/mnt/cross}, and the binary refers to
8198 @file{foo.c}, @value{GDBN} would not find it under
8199 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8201 Plain file names, relative file names with leading directories, file
8202 names containing dots, etc.@: are all treated as described above; for
8203 instance, if the source path is @file{/mnt/cross}, and the source file
8204 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8205 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8206 that---@file{/mnt/cross/foo.c}.
8208 Note that the executable search path is @emph{not} used to locate the
8211 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8212 any information it has cached about where source files are found and where
8213 each line is in the file.
8217 When you start @value{GDBN}, its source path includes only @samp{cdir}
8218 and @samp{cwd}, in that order.
8219 To add other directories, use the @code{directory} command.
8221 The search path is used to find both program source files and @value{GDBN}
8222 script files (read using the @samp{-command} option and @samp{source} command).
8224 In addition to the source path, @value{GDBN} provides a set of commands
8225 that manage a list of source path substitution rules. A @dfn{substitution
8226 rule} specifies how to rewrite source directories stored in the program's
8227 debug information in case the sources were moved to a different
8228 directory between compilation and debugging. A rule is made of
8229 two strings, the first specifying what needs to be rewritten in
8230 the path, and the second specifying how it should be rewritten.
8231 In @ref{set substitute-path}, we name these two parts @var{from} and
8232 @var{to} respectively. @value{GDBN} does a simple string replacement
8233 of @var{from} with @var{to} at the start of the directory part of the
8234 source file name, and uses that result instead of the original file
8235 name to look up the sources.
8237 Using the previous example, suppose the @file{foo-1.0} tree has been
8238 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8239 @value{GDBN} to replace @file{/usr/src} in all source path names with
8240 @file{/mnt/cross}. The first lookup will then be
8241 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8242 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8243 substitution rule, use the @code{set substitute-path} command
8244 (@pxref{set substitute-path}).
8246 To avoid unexpected substitution results, a rule is applied only if the
8247 @var{from} part of the directory name ends at a directory separator.
8248 For instance, a rule substituting @file{/usr/source} into
8249 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8250 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8251 is applied only at the beginning of the directory name, this rule will
8252 not be applied to @file{/root/usr/source/baz.c} either.
8254 In many cases, you can achieve the same result using the @code{directory}
8255 command. However, @code{set substitute-path} can be more efficient in
8256 the case where the sources are organized in a complex tree with multiple
8257 subdirectories. With the @code{directory} command, you need to add each
8258 subdirectory of your project. If you moved the entire tree while
8259 preserving its internal organization, then @code{set substitute-path}
8260 allows you to direct the debugger to all the sources with one single
8263 @code{set substitute-path} is also more than just a shortcut command.
8264 The source path is only used if the file at the original location no
8265 longer exists. On the other hand, @code{set substitute-path} modifies
8266 the debugger behavior to look at the rewritten location instead. So, if
8267 for any reason a source file that is not relevant to your executable is
8268 located at the original location, a substitution rule is the only
8269 method available to point @value{GDBN} at the new location.
8271 @cindex @samp{--with-relocated-sources}
8272 @cindex default source path substitution
8273 You can configure a default source path substitution rule by
8274 configuring @value{GDBN} with the
8275 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8276 should be the name of a directory under @value{GDBN}'s configured
8277 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8278 directory names in debug information under @var{dir} will be adjusted
8279 automatically if the installed @value{GDBN} is moved to a new
8280 location. This is useful if @value{GDBN}, libraries or executables
8281 with debug information and corresponding source code are being moved
8285 @item directory @var{dirname} @dots{}
8286 @item dir @var{dirname} @dots{}
8287 Add directory @var{dirname} to the front of the source path. Several
8288 directory names may be given to this command, separated by @samp{:}
8289 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8290 part of absolute file names) or
8291 whitespace. You may specify a directory that is already in the source
8292 path; this moves it forward, so @value{GDBN} searches it sooner.
8296 @vindex $cdir@r{, convenience variable}
8297 @vindex $cwd@r{, convenience variable}
8298 @cindex compilation directory
8299 @cindex current directory
8300 @cindex working directory
8301 @cindex directory, current
8302 @cindex directory, compilation
8303 You can use the string @samp{$cdir} to refer to the compilation
8304 directory (if one is recorded), and @samp{$cwd} to refer to the current
8305 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8306 tracks the current working directory as it changes during your @value{GDBN}
8307 session, while the latter is immediately expanded to the current
8308 directory at the time you add an entry to the source path.
8311 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8313 @c RET-repeat for @code{directory} is explicitly disabled, but since
8314 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8316 @item set directories @var{path-list}
8317 @kindex set directories
8318 Set the source path to @var{path-list}.
8319 @samp{$cdir:$cwd} are added if missing.
8321 @item show directories
8322 @kindex show directories
8323 Print the source path: show which directories it contains.
8325 @anchor{set substitute-path}
8326 @item set substitute-path @var{from} @var{to}
8327 @kindex set substitute-path
8328 Define a source path substitution rule, and add it at the end of the
8329 current list of existing substitution rules. If a rule with the same
8330 @var{from} was already defined, then the old rule is also deleted.
8332 For example, if the file @file{/foo/bar/baz.c} was moved to
8333 @file{/mnt/cross/baz.c}, then the command
8336 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8340 will tell @value{GDBN} to replace @samp{/foo/bar} with
8341 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8342 @file{baz.c} even though it was moved.
8344 In the case when more than one substitution rule have been defined,
8345 the rules are evaluated one by one in the order where they have been
8346 defined. The first one matching, if any, is selected to perform
8349 For instance, if we had entered the following commands:
8352 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8353 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8357 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8358 @file{/mnt/include/defs.h} by using the first rule. However, it would
8359 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8360 @file{/mnt/src/lib/foo.c}.
8363 @item unset substitute-path [path]
8364 @kindex unset substitute-path
8365 If a path is specified, search the current list of substitution rules
8366 for a rule that would rewrite that path. Delete that rule if found.
8367 A warning is emitted by the debugger if no rule could be found.
8369 If no path is specified, then all substitution rules are deleted.
8371 @item show substitute-path [path]
8372 @kindex show substitute-path
8373 If a path is specified, then print the source path substitution rule
8374 which would rewrite that path, if any.
8376 If no path is specified, then print all existing source path substitution
8381 If your source path is cluttered with directories that are no longer of
8382 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8383 versions of source. You can correct the situation as follows:
8387 Use @code{directory} with no argument to reset the source path to its default value.
8390 Use @code{directory} with suitable arguments to reinstall the
8391 directories you want in the source path. You can add all the
8392 directories in one command.
8396 @section Source and Machine Code
8397 @cindex source line and its code address
8399 You can use the command @code{info line} to map source lines to program
8400 addresses (and vice versa), and the command @code{disassemble} to display
8401 a range of addresses as machine instructions. You can use the command
8402 @code{set disassemble-next-line} to set whether to disassemble next
8403 source line when execution stops. When run under @sc{gnu} Emacs
8404 mode, the @code{info line} command causes the arrow to point to the
8405 line specified. Also, @code{info line} prints addresses in symbolic form as
8410 @item info line @var{location}
8411 Print the starting and ending addresses of the compiled code for
8412 source line @var{location}. You can specify source lines in any of
8413 the ways documented in @ref{Specify Location}.
8416 For example, we can use @code{info line} to discover the location of
8417 the object code for the first line of function
8418 @code{m4_changequote}:
8420 @c FIXME: I think this example should also show the addresses in
8421 @c symbolic form, as they usually would be displayed.
8423 (@value{GDBP}) info line m4_changequote
8424 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8428 @cindex code address and its source line
8429 We can also inquire (using @code{*@var{addr}} as the form for
8430 @var{location}) what source line covers a particular address:
8432 (@value{GDBP}) info line *0x63ff
8433 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8436 @cindex @code{$_} and @code{info line}
8437 @cindex @code{x} command, default address
8438 @kindex x@r{(examine), and} info line
8439 After @code{info line}, the default address for the @code{x} command
8440 is changed to the starting address of the line, so that @samp{x/i} is
8441 sufficient to begin examining the machine code (@pxref{Memory,
8442 ,Examining Memory}). Also, this address is saved as the value of the
8443 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8448 @cindex assembly instructions
8449 @cindex instructions, assembly
8450 @cindex machine instructions
8451 @cindex listing machine instructions
8453 @itemx disassemble /m
8454 @itemx disassemble /s
8455 @itemx disassemble /r
8456 This specialized command dumps a range of memory as machine
8457 instructions. It can also print mixed source+disassembly by specifying
8458 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8459 as well as in symbolic form by specifying the @code{/r} modifier.
8460 The default memory range is the function surrounding the
8461 program counter of the selected frame. A single argument to this
8462 command is a program counter value; @value{GDBN} dumps the function
8463 surrounding this value. When two arguments are given, they should
8464 be separated by a comma, possibly surrounded by whitespace. The
8465 arguments specify a range of addresses to dump, in one of two forms:
8468 @item @var{start},@var{end}
8469 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8470 @item @var{start},+@var{length}
8471 the addresses from @var{start} (inclusive) to
8472 @code{@var{start}+@var{length}} (exclusive).
8476 When 2 arguments are specified, the name of the function is also
8477 printed (since there could be several functions in the given range).
8479 The argument(s) can be any expression yielding a numeric value, such as
8480 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8482 If the range of memory being disassembled contains current program counter,
8483 the instruction at that location is shown with a @code{=>} marker.
8486 The following example shows the disassembly of a range of addresses of
8487 HP PA-RISC 2.0 code:
8490 (@value{GDBP}) disas 0x32c4, 0x32e4
8491 Dump of assembler code from 0x32c4 to 0x32e4:
8492 0x32c4 <main+204>: addil 0,dp
8493 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8494 0x32cc <main+212>: ldil 0x3000,r31
8495 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8496 0x32d4 <main+220>: ldo 0(r31),rp
8497 0x32d8 <main+224>: addil -0x800,dp
8498 0x32dc <main+228>: ldo 0x588(r1),r26
8499 0x32e0 <main+232>: ldil 0x3000,r31
8500 End of assembler dump.
8503 Here is an example showing mixed source+assembly for Intel x86
8504 with @code{/m} or @code{/s}, when the program is stopped just after
8505 function prologue in a non-optimized function with no inline code.
8508 (@value{GDBP}) disas /m main
8509 Dump of assembler code for function main:
8511 0x08048330 <+0>: push %ebp
8512 0x08048331 <+1>: mov %esp,%ebp
8513 0x08048333 <+3>: sub $0x8,%esp
8514 0x08048336 <+6>: and $0xfffffff0,%esp
8515 0x08048339 <+9>: sub $0x10,%esp
8517 6 printf ("Hello.\n");
8518 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8519 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8523 0x08048348 <+24>: mov $0x0,%eax
8524 0x0804834d <+29>: leave
8525 0x0804834e <+30>: ret
8527 End of assembler dump.
8530 The @code{/m} option is deprecated as its output is not useful when
8531 there is either inlined code or re-ordered code.
8532 The @code{/s} option is the preferred choice.
8533 Here is an example for AMD x86-64 showing the difference between
8534 @code{/m} output and @code{/s} output.
8535 This example has one inline function defined in a header file,
8536 and the code is compiled with @samp{-O2} optimization.
8537 Note how the @code{/m} output is missing the disassembly of
8538 several instructions that are present in the @code{/s} output.
8568 (@value{GDBP}) disas /m main
8569 Dump of assembler code for function main:
8573 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8574 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8578 0x000000000040041d <+29>: xor %eax,%eax
8579 0x000000000040041f <+31>: retq
8580 0x0000000000400420 <+32>: add %eax,%eax
8581 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8583 End of assembler dump.
8584 (@value{GDBP}) disas /s main
8585 Dump of assembler code for function main:
8589 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8593 0x0000000000400406 <+6>: test %eax,%eax
8594 0x0000000000400408 <+8>: js 0x400420 <main+32>
8599 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8600 0x000000000040040d <+13>: test %eax,%eax
8601 0x000000000040040f <+15>: mov $0x1,%eax
8602 0x0000000000400414 <+20>: cmovne %edx,%eax
8606 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8610 0x000000000040041d <+29>: xor %eax,%eax
8611 0x000000000040041f <+31>: retq
8615 0x0000000000400420 <+32>: add %eax,%eax
8616 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8617 End of assembler dump.
8620 Here is another example showing raw instructions in hex for AMD x86-64,
8623 (gdb) disas /r 0x400281,+10
8624 Dump of assembler code from 0x400281 to 0x40028b:
8625 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8626 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8627 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8628 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8629 End of assembler dump.
8632 Addresses cannot be specified as a location (@pxref{Specify Location}).
8633 So, for example, if you want to disassemble function @code{bar}
8634 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8635 and not @samp{disassemble foo.c:bar}.
8637 Some architectures have more than one commonly-used set of instruction
8638 mnemonics or other syntax.
8640 For programs that were dynamically linked and use shared libraries,
8641 instructions that call functions or branch to locations in the shared
8642 libraries might show a seemingly bogus location---it's actually a
8643 location of the relocation table. On some architectures, @value{GDBN}
8644 might be able to resolve these to actual function names.
8647 @kindex set disassembler-options
8648 @cindex disassembler options
8649 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
8650 This command controls the passing of target specific information to
8651 the disassembler. For a list of valid options, please refer to the
8652 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
8653 manual and/or the output of @kbd{objdump --help}
8654 (@pxref{objdump,,objdump,binutils.info,The GNU Binary Utilities}).
8655 The default value is the empty string.
8657 If it is necessary to specify more than one disassembler option, then
8658 multiple options can be placed together into a comma separated list.
8659 Currently this command is only supported on targets ARM, PowerPC
8662 @kindex show disassembler-options
8663 @item show disassembler-options
8664 Show the current setting of the disassembler options.
8668 @kindex set disassembly-flavor
8669 @cindex Intel disassembly flavor
8670 @cindex AT&T disassembly flavor
8671 @item set disassembly-flavor @var{instruction-set}
8672 Select the instruction set to use when disassembling the
8673 program via the @code{disassemble} or @code{x/i} commands.
8675 Currently this command is only defined for the Intel x86 family. You
8676 can set @var{instruction-set} to either @code{intel} or @code{att}.
8677 The default is @code{att}, the AT&T flavor used by default by Unix
8678 assemblers for x86-based targets.
8680 @kindex show disassembly-flavor
8681 @item show disassembly-flavor
8682 Show the current setting of the disassembly flavor.
8686 @kindex set disassemble-next-line
8687 @kindex show disassemble-next-line
8688 @item set disassemble-next-line
8689 @itemx show disassemble-next-line
8690 Control whether or not @value{GDBN} will disassemble the next source
8691 line or instruction when execution stops. If ON, @value{GDBN} will
8692 display disassembly of the next source line when execution of the
8693 program being debugged stops. This is @emph{in addition} to
8694 displaying the source line itself, which @value{GDBN} always does if
8695 possible. If the next source line cannot be displayed for some reason
8696 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8697 info in the debug info), @value{GDBN} will display disassembly of the
8698 next @emph{instruction} instead of showing the next source line. If
8699 AUTO, @value{GDBN} will display disassembly of next instruction only
8700 if the source line cannot be displayed. This setting causes
8701 @value{GDBN} to display some feedback when you step through a function
8702 with no line info or whose source file is unavailable. The default is
8703 OFF, which means never display the disassembly of the next line or
8709 @chapter Examining Data
8711 @cindex printing data
8712 @cindex examining data
8715 The usual way to examine data in your program is with the @code{print}
8716 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8717 evaluates and prints the value of an expression of the language your
8718 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8719 Different Languages}). It may also print the expression using a
8720 Python-based pretty-printer (@pxref{Pretty Printing}).
8723 @item print @var{expr}
8724 @itemx print /@var{f} @var{expr}
8725 @var{expr} is an expression (in the source language). By default the
8726 value of @var{expr} is printed in a format appropriate to its data type;
8727 you can choose a different format by specifying @samp{/@var{f}}, where
8728 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8732 @itemx print /@var{f}
8733 @cindex reprint the last value
8734 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8735 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8736 conveniently inspect the same value in an alternative format.
8739 A more low-level way of examining data is with the @code{x} command.
8740 It examines data in memory at a specified address and prints it in a
8741 specified format. @xref{Memory, ,Examining Memory}.
8743 If you are interested in information about types, or about how the
8744 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8745 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8748 @cindex exploring hierarchical data structures
8750 Another way of examining values of expressions and type information is
8751 through the Python extension command @code{explore} (available only if
8752 the @value{GDBN} build is configured with @code{--with-python}). It
8753 offers an interactive way to start at the highest level (or, the most
8754 abstract level) of the data type of an expression (or, the data type
8755 itself) and explore all the way down to leaf scalar values/fields
8756 embedded in the higher level data types.
8759 @item explore @var{arg}
8760 @var{arg} is either an expression (in the source language), or a type
8761 visible in the current context of the program being debugged.
8764 The working of the @code{explore} command can be illustrated with an
8765 example. If a data type @code{struct ComplexStruct} is defined in your
8775 struct ComplexStruct
8777 struct SimpleStruct *ss_p;
8783 followed by variable declarations as
8786 struct SimpleStruct ss = @{ 10, 1.11 @};
8787 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8791 then, the value of the variable @code{cs} can be explored using the
8792 @code{explore} command as follows.
8796 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8797 the following fields:
8799 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8800 arr = <Enter 1 to explore this field of type `int [10]'>
8802 Enter the field number of choice:
8806 Since the fields of @code{cs} are not scalar values, you are being
8807 prompted to chose the field you want to explore. Let's say you choose
8808 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8809 pointer, you will be asked if it is pointing to a single value. From
8810 the declaration of @code{cs} above, it is indeed pointing to a single
8811 value, hence you enter @code{y}. If you enter @code{n}, then you will
8812 be asked if it were pointing to an array of values, in which case this
8813 field will be explored as if it were an array.
8816 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8817 Continue exploring it as a pointer to a single value [y/n]: y
8818 The value of `*(cs.ss_p)' is a struct/class of type `struct
8819 SimpleStruct' with the following fields:
8821 i = 10 .. (Value of type `int')
8822 d = 1.1100000000000001 .. (Value of type `double')
8824 Press enter to return to parent value:
8828 If the field @code{arr} of @code{cs} was chosen for exploration by
8829 entering @code{1} earlier, then since it is as array, you will be
8830 prompted to enter the index of the element in the array that you want
8834 `cs.arr' is an array of `int'.
8835 Enter the index of the element you want to explore in `cs.arr': 5
8837 `(cs.arr)[5]' is a scalar value of type `int'.
8841 Press enter to return to parent value:
8844 In general, at any stage of exploration, you can go deeper towards the
8845 leaf values by responding to the prompts appropriately, or hit the
8846 return key to return to the enclosing data structure (the @i{higher}
8847 level data structure).
8849 Similar to exploring values, you can use the @code{explore} command to
8850 explore types. Instead of specifying a value (which is typically a
8851 variable name or an expression valid in the current context of the
8852 program being debugged), you specify a type name. If you consider the
8853 same example as above, your can explore the type
8854 @code{struct ComplexStruct} by passing the argument
8855 @code{struct ComplexStruct} to the @code{explore} command.
8858 (gdb) explore struct ComplexStruct
8862 By responding to the prompts appropriately in the subsequent interactive
8863 session, you can explore the type @code{struct ComplexStruct} in a
8864 manner similar to how the value @code{cs} was explored in the above
8867 The @code{explore} command also has two sub-commands,
8868 @code{explore value} and @code{explore type}. The former sub-command is
8869 a way to explicitly specify that value exploration of the argument is
8870 being invoked, while the latter is a way to explicitly specify that type
8871 exploration of the argument is being invoked.
8874 @item explore value @var{expr}
8875 @cindex explore value
8876 This sub-command of @code{explore} explores the value of the
8877 expression @var{expr} (if @var{expr} is an expression valid in the
8878 current context of the program being debugged). The behavior of this
8879 command is identical to that of the behavior of the @code{explore}
8880 command being passed the argument @var{expr}.
8882 @item explore type @var{arg}
8883 @cindex explore type
8884 This sub-command of @code{explore} explores the type of @var{arg} (if
8885 @var{arg} is a type visible in the current context of program being
8886 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8887 is an expression valid in the current context of the program being
8888 debugged). If @var{arg} is a type, then the behavior of this command is
8889 identical to that of the @code{explore} command being passed the
8890 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8891 this command will be identical to that of the @code{explore} command
8892 being passed the type of @var{arg} as the argument.
8896 * Expressions:: Expressions
8897 * Ambiguous Expressions:: Ambiguous Expressions
8898 * Variables:: Program variables
8899 * Arrays:: Artificial arrays
8900 * Output Formats:: Output formats
8901 * Memory:: Examining memory
8902 * Auto Display:: Automatic display
8903 * Print Settings:: Print settings
8904 * Pretty Printing:: Python pretty printing
8905 * Value History:: Value history
8906 * Convenience Vars:: Convenience variables
8907 * Convenience Funs:: Convenience functions
8908 * Registers:: Registers
8909 * Floating Point Hardware:: Floating point hardware
8910 * Vector Unit:: Vector Unit
8911 * OS Information:: Auxiliary data provided by operating system
8912 * Memory Region Attributes:: Memory region attributes
8913 * Dump/Restore Files:: Copy between memory and a file
8914 * Core File Generation:: Cause a program dump its core
8915 * Character Sets:: Debugging programs that use a different
8916 character set than GDB does
8917 * Caching Target Data:: Data caching for targets
8918 * Searching Memory:: Searching memory for a sequence of bytes
8919 * Value Sizes:: Managing memory allocated for values
8923 @section Expressions
8926 @code{print} and many other @value{GDBN} commands accept an expression and
8927 compute its value. Any kind of constant, variable or operator defined
8928 by the programming language you are using is valid in an expression in
8929 @value{GDBN}. This includes conditional expressions, function calls,
8930 casts, and string constants. It also includes preprocessor macros, if
8931 you compiled your program to include this information; see
8934 @cindex arrays in expressions
8935 @value{GDBN} supports array constants in expressions input by
8936 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8937 you can use the command @code{print @{1, 2, 3@}} to create an array
8938 of three integers. If you pass an array to a function or assign it
8939 to a program variable, @value{GDBN} copies the array to memory that
8940 is @code{malloc}ed in the target program.
8942 Because C is so widespread, most of the expressions shown in examples in
8943 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8944 Languages}, for information on how to use expressions in other
8947 In this section, we discuss operators that you can use in @value{GDBN}
8948 expressions regardless of your programming language.
8950 @cindex casts, in expressions
8951 Casts are supported in all languages, not just in C, because it is so
8952 useful to cast a number into a pointer in order to examine a structure
8953 at that address in memory.
8954 @c FIXME: casts supported---Mod2 true?
8956 @value{GDBN} supports these operators, in addition to those common
8957 to programming languages:
8961 @samp{@@} is a binary operator for treating parts of memory as arrays.
8962 @xref{Arrays, ,Artificial Arrays}, for more information.
8965 @samp{::} allows you to specify a variable in terms of the file or
8966 function where it is defined. @xref{Variables, ,Program Variables}.
8968 @cindex @{@var{type}@}
8969 @cindex type casting memory
8970 @cindex memory, viewing as typed object
8971 @cindex casts, to view memory
8972 @item @{@var{type}@} @var{addr}
8973 Refers to an object of type @var{type} stored at address @var{addr} in
8974 memory. The address @var{addr} may be any expression whose value is
8975 an integer or pointer (but parentheses are required around binary
8976 operators, just as in a cast). This construct is allowed regardless
8977 of what kind of data is normally supposed to reside at @var{addr}.
8980 @node Ambiguous Expressions
8981 @section Ambiguous Expressions
8982 @cindex ambiguous expressions
8984 Expressions can sometimes contain some ambiguous elements. For instance,
8985 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8986 a single function name to be defined several times, for application in
8987 different contexts. This is called @dfn{overloading}. Another example
8988 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8989 templates and is typically instantiated several times, resulting in
8990 the same function name being defined in different contexts.
8992 In some cases and depending on the language, it is possible to adjust
8993 the expression to remove the ambiguity. For instance in C@t{++}, you
8994 can specify the signature of the function you want to break on, as in
8995 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8996 qualified name of your function often makes the expression unambiguous
8999 When an ambiguity that needs to be resolved is detected, the debugger
9000 has the capability to display a menu of numbered choices for each
9001 possibility, and then waits for the selection with the prompt @samp{>}.
9002 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9003 aborts the current command. If the command in which the expression was
9004 used allows more than one choice to be selected, the next option in the
9005 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9008 For example, the following session excerpt shows an attempt to set a
9009 breakpoint at the overloaded symbol @code{String::after}.
9010 We choose three particular definitions of that function name:
9012 @c FIXME! This is likely to change to show arg type lists, at least
9015 (@value{GDBP}) b String::after
9018 [2] file:String.cc; line number:867
9019 [3] file:String.cc; line number:860
9020 [4] file:String.cc; line number:875
9021 [5] file:String.cc; line number:853
9022 [6] file:String.cc; line number:846
9023 [7] file:String.cc; line number:735
9025 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9026 Breakpoint 2 at 0xb344: file String.cc, line 875.
9027 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9028 Multiple breakpoints were set.
9029 Use the "delete" command to delete unwanted
9036 @kindex set multiple-symbols
9037 @item set multiple-symbols @var{mode}
9038 @cindex multiple-symbols menu
9040 This option allows you to adjust the debugger behavior when an expression
9043 By default, @var{mode} is set to @code{all}. If the command with which
9044 the expression is used allows more than one choice, then @value{GDBN}
9045 automatically selects all possible choices. For instance, inserting
9046 a breakpoint on a function using an ambiguous name results in a breakpoint
9047 inserted on each possible match. However, if a unique choice must be made,
9048 then @value{GDBN} uses the menu to help you disambiguate the expression.
9049 For instance, printing the address of an overloaded function will result
9050 in the use of the menu.
9052 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9053 when an ambiguity is detected.
9055 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9056 an error due to the ambiguity and the command is aborted.
9058 @kindex show multiple-symbols
9059 @item show multiple-symbols
9060 Show the current value of the @code{multiple-symbols} setting.
9064 @section Program Variables
9066 The most common kind of expression to use is the name of a variable
9069 Variables in expressions are understood in the selected stack frame
9070 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9074 global (or file-static)
9081 visible according to the scope rules of the
9082 programming language from the point of execution in that frame
9085 @noindent This means that in the function
9100 you can examine and use the variable @code{a} whenever your program is
9101 executing within the function @code{foo}, but you can only use or
9102 examine the variable @code{b} while your program is executing inside
9103 the block where @code{b} is declared.
9105 @cindex variable name conflict
9106 There is an exception: you can refer to a variable or function whose
9107 scope is a single source file even if the current execution point is not
9108 in this file. But it is possible to have more than one such variable or
9109 function with the same name (in different source files). If that
9110 happens, referring to that name has unpredictable effects. If you wish,
9111 you can specify a static variable in a particular function or file by
9112 using the colon-colon (@code{::}) notation:
9114 @cindex colon-colon, context for variables/functions
9116 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9117 @cindex @code{::}, context for variables/functions
9120 @var{file}::@var{variable}
9121 @var{function}::@var{variable}
9125 Here @var{file} or @var{function} is the name of the context for the
9126 static @var{variable}. In the case of file names, you can use quotes to
9127 make sure @value{GDBN} parses the file name as a single word---for example,
9128 to print a global value of @code{x} defined in @file{f2.c}:
9131 (@value{GDBP}) p 'f2.c'::x
9134 The @code{::} notation is normally used for referring to
9135 static variables, since you typically disambiguate uses of local variables
9136 in functions by selecting the appropriate frame and using the
9137 simple name of the variable. However, you may also use this notation
9138 to refer to local variables in frames enclosing the selected frame:
9147 process (a); /* Stop here */
9158 For example, if there is a breakpoint at the commented line,
9159 here is what you might see
9160 when the program stops after executing the call @code{bar(0)}:
9165 (@value{GDBP}) p bar::a
9168 #2 0x080483d0 in foo (a=5) at foobar.c:12
9171 (@value{GDBP}) p bar::a
9175 @cindex C@t{++} scope resolution
9176 These uses of @samp{::} are very rarely in conflict with the very
9177 similar use of the same notation in C@t{++}. When they are in
9178 conflict, the C@t{++} meaning takes precedence; however, this can be
9179 overridden by quoting the file or function name with single quotes.
9181 For example, suppose the program is stopped in a method of a class
9182 that has a field named @code{includefile}, and there is also an
9183 include file named @file{includefile} that defines a variable,
9187 (@value{GDBP}) p includefile
9189 (@value{GDBP}) p includefile::some_global
9190 A syntax error in expression, near `'.
9191 (@value{GDBP}) p 'includefile'::some_global
9195 @cindex wrong values
9196 @cindex variable values, wrong
9197 @cindex function entry/exit, wrong values of variables
9198 @cindex optimized code, wrong values of variables
9200 @emph{Warning:} Occasionally, a local variable may appear to have the
9201 wrong value at certain points in a function---just after entry to a new
9202 scope, and just before exit.
9204 You may see this problem when you are stepping by machine instructions.
9205 This is because, on most machines, it takes more than one instruction to
9206 set up a stack frame (including local variable definitions); if you are
9207 stepping by machine instructions, variables may appear to have the wrong
9208 values until the stack frame is completely built. On exit, it usually
9209 also takes more than one machine instruction to destroy a stack frame;
9210 after you begin stepping through that group of instructions, local
9211 variable definitions may be gone.
9213 This may also happen when the compiler does significant optimizations.
9214 To be sure of always seeing accurate values, turn off all optimization
9217 @cindex ``No symbol "foo" in current context''
9218 Another possible effect of compiler optimizations is to optimize
9219 unused variables out of existence, or assign variables to registers (as
9220 opposed to memory addresses). Depending on the support for such cases
9221 offered by the debug info format used by the compiler, @value{GDBN}
9222 might not be able to display values for such local variables. If that
9223 happens, @value{GDBN} will print a message like this:
9226 No symbol "foo" in current context.
9229 To solve such problems, either recompile without optimizations, or use a
9230 different debug info format, if the compiler supports several such
9231 formats. @xref{Compilation}, for more information on choosing compiler
9232 options. @xref{C, ,C and C@t{++}}, for more information about debug
9233 info formats that are best suited to C@t{++} programs.
9235 If you ask to print an object whose contents are unknown to
9236 @value{GDBN}, e.g., because its data type is not completely specified
9237 by the debug information, @value{GDBN} will say @samp{<incomplete
9238 type>}. @xref{Symbols, incomplete type}, for more about this.
9240 @cindex no debug info variables
9241 If you try to examine or use the value of a (global) variable for
9242 which @value{GDBN} has no type information, e.g., because the program
9243 includes no debug information, @value{GDBN} displays an error message.
9244 @xref{Symbols, unknown type}, for more about unknown types. If you
9245 cast the variable to its declared type, @value{GDBN} gets the
9246 variable's value using the cast-to type as the variable's type. For
9247 example, in a C program:
9250 (@value{GDBP}) p var
9251 'var' has unknown type; cast it to its declared type
9252 (@value{GDBP}) p (float) var
9256 If you append @kbd{@@entry} string to a function parameter name you get its
9257 value at the time the function got called. If the value is not available an
9258 error message is printed. Entry values are available only with some compilers.
9259 Entry values are normally also printed at the function parameter list according
9260 to @ref{set print entry-values}.
9263 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9269 (gdb) print i@@entry
9273 Strings are identified as arrays of @code{char} values without specified
9274 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9275 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9276 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9277 defines literal string type @code{"char"} as @code{char} without a sign.
9282 signed char var1[] = "A";
9285 You get during debugging
9290 $2 = @{65 'A', 0 '\0'@}
9294 @section Artificial Arrays
9296 @cindex artificial array
9298 @kindex @@@r{, referencing memory as an array}
9299 It is often useful to print out several successive objects of the
9300 same type in memory; a section of an array, or an array of
9301 dynamically determined size for which only a pointer exists in the
9304 You can do this by referring to a contiguous span of memory as an
9305 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9306 operand of @samp{@@} should be the first element of the desired array
9307 and be an individual object. The right operand should be the desired length
9308 of the array. The result is an array value whose elements are all of
9309 the type of the left argument. The first element is actually the left
9310 argument; the second element comes from bytes of memory immediately
9311 following those that hold the first element, and so on. Here is an
9312 example. If a program says
9315 int *array = (int *) malloc (len * sizeof (int));
9319 you can print the contents of @code{array} with
9325 The left operand of @samp{@@} must reside in memory. Array values made
9326 with @samp{@@} in this way behave just like other arrays in terms of
9327 subscripting, and are coerced to pointers when used in expressions.
9328 Artificial arrays most often appear in expressions via the value history
9329 (@pxref{Value History, ,Value History}), after printing one out.
9331 Another way to create an artificial array is to use a cast.
9332 This re-interprets a value as if it were an array.
9333 The value need not be in memory:
9335 (@value{GDBP}) p/x (short[2])0x12345678
9336 $1 = @{0x1234, 0x5678@}
9339 As a convenience, if you leave the array length out (as in
9340 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9341 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9343 (@value{GDBP}) p/x (short[])0x12345678
9344 $2 = @{0x1234, 0x5678@}
9347 Sometimes the artificial array mechanism is not quite enough; in
9348 moderately complex data structures, the elements of interest may not
9349 actually be adjacent---for example, if you are interested in the values
9350 of pointers in an array. One useful work-around in this situation is
9351 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9352 Variables}) as a counter in an expression that prints the first
9353 interesting value, and then repeat that expression via @key{RET}. For
9354 instance, suppose you have an array @code{dtab} of pointers to
9355 structures, and you are interested in the values of a field @code{fv}
9356 in each structure. Here is an example of what you might type:
9366 @node Output Formats
9367 @section Output Formats
9369 @cindex formatted output
9370 @cindex output formats
9371 By default, @value{GDBN} prints a value according to its data type. Sometimes
9372 this is not what you want. For example, you might want to print a number
9373 in hex, or a pointer in decimal. Or you might want to view data in memory
9374 at a certain address as a character string or as an instruction. To do
9375 these things, specify an @dfn{output format} when you print a value.
9377 The simplest use of output formats is to say how to print a value
9378 already computed. This is done by starting the arguments of the
9379 @code{print} command with a slash and a format letter. The format
9380 letters supported are:
9384 Regard the bits of the value as an integer, and print the integer in
9388 Print as integer in signed decimal.
9391 Print as integer in unsigned decimal.
9394 Print as integer in octal.
9397 Print as integer in binary. The letter @samp{t} stands for ``two''.
9398 @footnote{@samp{b} cannot be used because these format letters are also
9399 used with the @code{x} command, where @samp{b} stands for ``byte'';
9400 see @ref{Memory,,Examining Memory}.}
9403 @cindex unknown address, locating
9404 @cindex locate address
9405 Print as an address, both absolute in hexadecimal and as an offset from
9406 the nearest preceding symbol. You can use this format used to discover
9407 where (in what function) an unknown address is located:
9410 (@value{GDBP}) p/a 0x54320
9411 $3 = 0x54320 <_initialize_vx+396>
9415 The command @code{info symbol 0x54320} yields similar results.
9416 @xref{Symbols, info symbol}.
9419 Regard as an integer and print it as a character constant. This
9420 prints both the numerical value and its character representation. The
9421 character representation is replaced with the octal escape @samp{\nnn}
9422 for characters outside the 7-bit @sc{ascii} range.
9424 Without this format, @value{GDBN} displays @code{char},
9425 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9426 constants. Single-byte members of vectors are displayed as integer
9430 Regard the bits of the value as a floating point number and print
9431 using typical floating point syntax.
9434 @cindex printing strings
9435 @cindex printing byte arrays
9436 Regard as a string, if possible. With this format, pointers to single-byte
9437 data are displayed as null-terminated strings and arrays of single-byte data
9438 are displayed as fixed-length strings. Other values are displayed in their
9441 Without this format, @value{GDBN} displays pointers to and arrays of
9442 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9443 strings. Single-byte members of a vector are displayed as an integer
9447 Like @samp{x} formatting, the value is treated as an integer and
9448 printed as hexadecimal, but leading zeros are printed to pad the value
9449 to the size of the integer type.
9452 @cindex raw printing
9453 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9454 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9455 Printing}). This typically results in a higher-level display of the
9456 value's contents. The @samp{r} format bypasses any Python
9457 pretty-printer which might exist.
9460 For example, to print the program counter in hex (@pxref{Registers}), type
9467 Note that no space is required before the slash; this is because command
9468 names in @value{GDBN} cannot contain a slash.
9470 To reprint the last value in the value history with a different format,
9471 you can use the @code{print} command with just a format and no
9472 expression. For example, @samp{p/x} reprints the last value in hex.
9475 @section Examining Memory
9477 You can use the command @code{x} (for ``examine'') to examine memory in
9478 any of several formats, independently of your program's data types.
9480 @cindex examining memory
9482 @kindex x @r{(examine memory)}
9483 @item x/@var{nfu} @var{addr}
9486 Use the @code{x} command to examine memory.
9489 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9490 much memory to display and how to format it; @var{addr} is an
9491 expression giving the address where you want to start displaying memory.
9492 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9493 Several commands set convenient defaults for @var{addr}.
9496 @item @var{n}, the repeat count
9497 The repeat count is a decimal integer; the default is 1. It specifies
9498 how much memory (counting by units @var{u}) to display. If a negative
9499 number is specified, memory is examined backward from @var{addr}.
9500 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9503 @item @var{f}, the display format
9504 The display format is one of the formats used by @code{print}
9505 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9506 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9507 The default is @samp{x} (hexadecimal) initially. The default changes
9508 each time you use either @code{x} or @code{print}.
9510 @item @var{u}, the unit size
9511 The unit size is any of
9517 Halfwords (two bytes).
9519 Words (four bytes). This is the initial default.
9521 Giant words (eight bytes).
9524 Each time you specify a unit size with @code{x}, that size becomes the
9525 default unit the next time you use @code{x}. For the @samp{i} format,
9526 the unit size is ignored and is normally not written. For the @samp{s} format,
9527 the unit size defaults to @samp{b}, unless it is explicitly given.
9528 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9529 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9530 Note that the results depend on the programming language of the
9531 current compilation unit. If the language is C, the @samp{s}
9532 modifier will use the UTF-16 encoding while @samp{w} will use
9533 UTF-32. The encoding is set by the programming language and cannot
9536 @item @var{addr}, starting display address
9537 @var{addr} is the address where you want @value{GDBN} to begin displaying
9538 memory. The expression need not have a pointer value (though it may);
9539 it is always interpreted as an integer address of a byte of memory.
9540 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9541 @var{addr} is usually just after the last address examined---but several
9542 other commands also set the default address: @code{info breakpoints} (to
9543 the address of the last breakpoint listed), @code{info line} (to the
9544 starting address of a line), and @code{print} (if you use it to display
9545 a value from memory).
9548 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9549 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9550 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9551 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9552 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9554 You can also specify a negative repeat count to examine memory backward
9555 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9556 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9558 Since the letters indicating unit sizes are all distinct from the
9559 letters specifying output formats, you do not have to remember whether
9560 unit size or format comes first; either order works. The output
9561 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9562 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9564 Even though the unit size @var{u} is ignored for the formats @samp{s}
9565 and @samp{i}, you might still want to use a count @var{n}; for example,
9566 @samp{3i} specifies that you want to see three machine instructions,
9567 including any operands. For convenience, especially when used with
9568 the @code{display} command, the @samp{i} format also prints branch delay
9569 slot instructions, if any, beyond the count specified, which immediately
9570 follow the last instruction that is within the count. The command
9571 @code{disassemble} gives an alternative way of inspecting machine
9572 instructions; see @ref{Machine Code,,Source and Machine Code}.
9574 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9575 the command displays null-terminated strings or instructions before the given
9576 address as many as the absolute value of the given number. For the @samp{i}
9577 format, we use line number information in the debug info to accurately locate
9578 instruction boundaries while disassembling backward. If line info is not
9579 available, the command stops examining memory with an error message.
9581 All the defaults for the arguments to @code{x} are designed to make it
9582 easy to continue scanning memory with minimal specifications each time
9583 you use @code{x}. For example, after you have inspected three machine
9584 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9585 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9586 the repeat count @var{n} is used again; the other arguments default as
9587 for successive uses of @code{x}.
9589 When examining machine instructions, the instruction at current program
9590 counter is shown with a @code{=>} marker. For example:
9593 (@value{GDBP}) x/5i $pc-6
9594 0x804837f <main+11>: mov %esp,%ebp
9595 0x8048381 <main+13>: push %ecx
9596 0x8048382 <main+14>: sub $0x4,%esp
9597 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9598 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9601 @cindex @code{$_}, @code{$__}, and value history
9602 The addresses and contents printed by the @code{x} command are not saved
9603 in the value history because there is often too much of them and they
9604 would get in the way. Instead, @value{GDBN} makes these values available for
9605 subsequent use in expressions as values of the convenience variables
9606 @code{$_} and @code{$__}. After an @code{x} command, the last address
9607 examined is available for use in expressions in the convenience variable
9608 @code{$_}. The contents of that address, as examined, are available in
9609 the convenience variable @code{$__}.
9611 If the @code{x} command has a repeat count, the address and contents saved
9612 are from the last memory unit printed; this is not the same as the last
9613 address printed if several units were printed on the last line of output.
9615 @anchor{addressable memory unit}
9616 @cindex addressable memory unit
9617 Most targets have an addressable memory unit size of 8 bits. This means
9618 that to each memory address are associated 8 bits of data. Some
9619 targets, however, have other addressable memory unit sizes.
9620 Within @value{GDBN} and this document, the term
9621 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9622 when explicitly referring to a chunk of data of that size. The word
9623 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9624 the addressable memory unit size of the target. For most systems,
9625 addressable memory unit is a synonym of byte.
9627 @cindex remote memory comparison
9628 @cindex target memory comparison
9629 @cindex verify remote memory image
9630 @cindex verify target memory image
9631 When you are debugging a program running on a remote target machine
9632 (@pxref{Remote Debugging}), you may wish to verify the program's image
9633 in the remote machine's memory against the executable file you
9634 downloaded to the target. Or, on any target, you may want to check
9635 whether the program has corrupted its own read-only sections. The
9636 @code{compare-sections} command is provided for such situations.
9639 @kindex compare-sections
9640 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9641 Compare the data of a loadable section @var{section-name} in the
9642 executable file of the program being debugged with the same section in
9643 the target machine's memory, and report any mismatches. With no
9644 arguments, compares all loadable sections. With an argument of
9645 @code{-r}, compares all loadable read-only sections.
9647 Note: for remote targets, this command can be accelerated if the
9648 target supports computing the CRC checksum of a block of memory
9649 (@pxref{qCRC packet}).
9653 @section Automatic Display
9654 @cindex automatic display
9655 @cindex display of expressions
9657 If you find that you want to print the value of an expression frequently
9658 (to see how it changes), you might want to add it to the @dfn{automatic
9659 display list} so that @value{GDBN} prints its value each time your program stops.
9660 Each expression added to the list is given a number to identify it;
9661 to remove an expression from the list, you specify that number.
9662 The automatic display looks like this:
9666 3: bar[5] = (struct hack *) 0x3804
9670 This display shows item numbers, expressions and their current values. As with
9671 displays you request manually using @code{x} or @code{print}, you can
9672 specify the output format you prefer; in fact, @code{display} decides
9673 whether to use @code{print} or @code{x} depending your format
9674 specification---it uses @code{x} if you specify either the @samp{i}
9675 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9679 @item display @var{expr}
9680 Add the expression @var{expr} to the list of expressions to display
9681 each time your program stops. @xref{Expressions, ,Expressions}.
9683 @code{display} does not repeat if you press @key{RET} again after using it.
9685 @item display/@var{fmt} @var{expr}
9686 For @var{fmt} specifying only a display format and not a size or
9687 count, add the expression @var{expr} to the auto-display list but
9688 arrange to display it each time in the specified format @var{fmt}.
9689 @xref{Output Formats,,Output Formats}.
9691 @item display/@var{fmt} @var{addr}
9692 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9693 number of units, add the expression @var{addr} as a memory address to
9694 be examined each time your program stops. Examining means in effect
9695 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9698 For example, @samp{display/i $pc} can be helpful, to see the machine
9699 instruction about to be executed each time execution stops (@samp{$pc}
9700 is a common name for the program counter; @pxref{Registers, ,Registers}).
9703 @kindex delete display
9705 @item undisplay @var{dnums}@dots{}
9706 @itemx delete display @var{dnums}@dots{}
9707 Remove items from the list of expressions to display. Specify the
9708 numbers of the displays that you want affected with the command
9709 argument @var{dnums}. It can be a single display number, one of the
9710 numbers shown in the first field of the @samp{info display} display;
9711 or it could be a range of display numbers, as in @code{2-4}.
9713 @code{undisplay} does not repeat if you press @key{RET} after using it.
9714 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9716 @kindex disable display
9717 @item disable display @var{dnums}@dots{}
9718 Disable the display of item numbers @var{dnums}. A disabled display
9719 item is not printed automatically, but is not forgotten. It may be
9720 enabled again later. Specify the numbers of the displays that you
9721 want affected with the command argument @var{dnums}. It can be a
9722 single display number, one of the numbers shown in the first field of
9723 the @samp{info display} display; or it could be a range of display
9724 numbers, as in @code{2-4}.
9726 @kindex enable display
9727 @item enable display @var{dnums}@dots{}
9728 Enable display of item numbers @var{dnums}. It becomes effective once
9729 again in auto display of its expression, until you specify otherwise.
9730 Specify the numbers of the displays that you want affected with the
9731 command argument @var{dnums}. It can be a single display number, one
9732 of the numbers shown in the first field of the @samp{info display}
9733 display; or it could be a range of display numbers, as in @code{2-4}.
9736 Display the current values of the expressions on the list, just as is
9737 done when your program stops.
9739 @kindex info display
9741 Print the list of expressions previously set up to display
9742 automatically, each one with its item number, but without showing the
9743 values. This includes disabled expressions, which are marked as such.
9744 It also includes expressions which would not be displayed right now
9745 because they refer to automatic variables not currently available.
9748 @cindex display disabled out of scope
9749 If a display expression refers to local variables, then it does not make
9750 sense outside the lexical context for which it was set up. Such an
9751 expression is disabled when execution enters a context where one of its
9752 variables is not defined. For example, if you give the command
9753 @code{display last_char} while inside a function with an argument
9754 @code{last_char}, @value{GDBN} displays this argument while your program
9755 continues to stop inside that function. When it stops elsewhere---where
9756 there is no variable @code{last_char}---the display is disabled
9757 automatically. The next time your program stops where @code{last_char}
9758 is meaningful, you can enable the display expression once again.
9760 @node Print Settings
9761 @section Print Settings
9763 @cindex format options
9764 @cindex print settings
9765 @value{GDBN} provides the following ways to control how arrays, structures,
9766 and symbols are printed.
9769 These settings are useful for debugging programs in any language:
9773 @item set print address
9774 @itemx set print address on
9775 @cindex print/don't print memory addresses
9776 @value{GDBN} prints memory addresses showing the location of stack
9777 traces, structure values, pointer values, breakpoints, and so forth,
9778 even when it also displays the contents of those addresses. The default
9779 is @code{on}. For example, this is what a stack frame display looks like with
9780 @code{set print address on}:
9785 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9787 530 if (lquote != def_lquote)
9791 @item set print address off
9792 Do not print addresses when displaying their contents. For example,
9793 this is the same stack frame displayed with @code{set print address off}:
9797 (@value{GDBP}) set print addr off
9799 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9800 530 if (lquote != def_lquote)
9804 You can use @samp{set print address off} to eliminate all machine
9805 dependent displays from the @value{GDBN} interface. For example, with
9806 @code{print address off}, you should get the same text for backtraces on
9807 all machines---whether or not they involve pointer arguments.
9810 @item show print address
9811 Show whether or not addresses are to be printed.
9814 When @value{GDBN} prints a symbolic address, it normally prints the
9815 closest earlier symbol plus an offset. If that symbol does not uniquely
9816 identify the address (for example, it is a name whose scope is a single
9817 source file), you may need to clarify. One way to do this is with
9818 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9819 you can set @value{GDBN} to print the source file and line number when
9820 it prints a symbolic address:
9823 @item set print symbol-filename on
9824 @cindex source file and line of a symbol
9825 @cindex symbol, source file and line
9826 Tell @value{GDBN} to print the source file name and line number of a
9827 symbol in the symbolic form of an address.
9829 @item set print symbol-filename off
9830 Do not print source file name and line number of a symbol. This is the
9833 @item show print symbol-filename
9834 Show whether or not @value{GDBN} will print the source file name and
9835 line number of a symbol in the symbolic form of an address.
9838 Another situation where it is helpful to show symbol filenames and line
9839 numbers is when disassembling code; @value{GDBN} shows you the line
9840 number and source file that corresponds to each instruction.
9842 Also, you may wish to see the symbolic form only if the address being
9843 printed is reasonably close to the closest earlier symbol:
9846 @item set print max-symbolic-offset @var{max-offset}
9847 @itemx set print max-symbolic-offset unlimited
9848 @cindex maximum value for offset of closest symbol
9849 Tell @value{GDBN} to only display the symbolic form of an address if the
9850 offset between the closest earlier symbol and the address is less than
9851 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9852 to always print the symbolic form of an address if any symbol precedes
9853 it. Zero is equivalent to @code{unlimited}.
9855 @item show print max-symbolic-offset
9856 Ask how large the maximum offset is that @value{GDBN} prints in a
9860 @cindex wild pointer, interpreting
9861 @cindex pointer, finding referent
9862 If you have a pointer and you are not sure where it points, try
9863 @samp{set print symbol-filename on}. Then you can determine the name
9864 and source file location of the variable where it points, using
9865 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9866 For example, here @value{GDBN} shows that a variable @code{ptt} points
9867 at another variable @code{t}, defined in @file{hi2.c}:
9870 (@value{GDBP}) set print symbol-filename on
9871 (@value{GDBP}) p/a ptt
9872 $4 = 0xe008 <t in hi2.c>
9876 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9877 does not show the symbol name and filename of the referent, even with
9878 the appropriate @code{set print} options turned on.
9881 You can also enable @samp{/a}-like formatting all the time using
9882 @samp{set print symbol on}:
9885 @item set print symbol on
9886 Tell @value{GDBN} to print the symbol corresponding to an address, if
9889 @item set print symbol off
9890 Tell @value{GDBN} not to print the symbol corresponding to an
9891 address. In this mode, @value{GDBN} will still print the symbol
9892 corresponding to pointers to functions. This is the default.
9894 @item show print symbol
9895 Show whether @value{GDBN} will display the symbol corresponding to an
9899 Other settings control how different kinds of objects are printed:
9902 @item set print array
9903 @itemx set print array on
9904 @cindex pretty print arrays
9905 Pretty print arrays. This format is more convenient to read,
9906 but uses more space. The default is off.
9908 @item set print array off
9909 Return to compressed format for arrays.
9911 @item show print array
9912 Show whether compressed or pretty format is selected for displaying
9915 @cindex print array indexes
9916 @item set print array-indexes
9917 @itemx set print array-indexes on
9918 Print the index of each element when displaying arrays. May be more
9919 convenient to locate a given element in the array or quickly find the
9920 index of a given element in that printed array. The default is off.
9922 @item set print array-indexes off
9923 Stop printing element indexes when displaying arrays.
9925 @item show print array-indexes
9926 Show whether the index of each element is printed when displaying
9929 @item set print elements @var{number-of-elements}
9930 @itemx set print elements unlimited
9931 @cindex number of array elements to print
9932 @cindex limit on number of printed array elements
9933 Set a limit on how many elements of an array @value{GDBN} will print.
9934 If @value{GDBN} is printing a large array, it stops printing after it has
9935 printed the number of elements set by the @code{set print elements} command.
9936 This limit also applies to the display of strings.
9937 When @value{GDBN} starts, this limit is set to 200.
9938 Setting @var{number-of-elements} to @code{unlimited} or zero means
9939 that the number of elements to print is unlimited.
9941 @item show print elements
9942 Display the number of elements of a large array that @value{GDBN} will print.
9943 If the number is 0, then the printing is unlimited.
9945 @item set print frame-arguments @var{value}
9946 @kindex set print frame-arguments
9947 @cindex printing frame argument values
9948 @cindex print all frame argument values
9949 @cindex print frame argument values for scalars only
9950 @cindex do not print frame argument values
9951 This command allows to control how the values of arguments are printed
9952 when the debugger prints a frame (@pxref{Frames}). The possible
9957 The values of all arguments are printed.
9960 Print the value of an argument only if it is a scalar. The value of more
9961 complex arguments such as arrays, structures, unions, etc, is replaced
9962 by @code{@dots{}}. This is the default. Here is an example where
9963 only scalar arguments are shown:
9966 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9971 None of the argument values are printed. Instead, the value of each argument
9972 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9975 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9980 By default, only scalar arguments are printed. This command can be used
9981 to configure the debugger to print the value of all arguments, regardless
9982 of their type. However, it is often advantageous to not print the value
9983 of more complex parameters. For instance, it reduces the amount of
9984 information printed in each frame, making the backtrace more readable.
9985 Also, it improves performance when displaying Ada frames, because
9986 the computation of large arguments can sometimes be CPU-intensive,
9987 especially in large applications. Setting @code{print frame-arguments}
9988 to @code{scalars} (the default) or @code{none} avoids this computation,
9989 thus speeding up the display of each Ada frame.
9991 @item show print frame-arguments
9992 Show how the value of arguments should be displayed when printing a frame.
9994 @item set print raw frame-arguments on
9995 Print frame arguments in raw, non pretty-printed, form.
9997 @item set print raw frame-arguments off
9998 Print frame arguments in pretty-printed form, if there is a pretty-printer
9999 for the value (@pxref{Pretty Printing}),
10000 otherwise print the value in raw form.
10001 This is the default.
10003 @item show print raw frame-arguments
10004 Show whether to print frame arguments in raw form.
10006 @anchor{set print entry-values}
10007 @item set print entry-values @var{value}
10008 @kindex set print entry-values
10009 Set printing of frame argument values at function entry. In some cases
10010 @value{GDBN} can determine the value of function argument which was passed by
10011 the function caller, even if the value was modified inside the called function
10012 and therefore is different. With optimized code, the current value could be
10013 unavailable, but the entry value may still be known.
10015 The default value is @code{default} (see below for its description). Older
10016 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10017 this feature will behave in the @code{default} setting the same way as with the
10020 This functionality is currently supported only by DWARF 2 debugging format and
10021 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10022 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10025 The @var{value} parameter can be one of the following:
10029 Print only actual parameter values, never print values from function entry
10033 #0 different (val=6)
10034 #0 lost (val=<optimized out>)
10036 #0 invalid (val=<optimized out>)
10040 Print only parameter values from function entry point. The actual parameter
10041 values are never printed.
10043 #0 equal (val@@entry=5)
10044 #0 different (val@@entry=5)
10045 #0 lost (val@@entry=5)
10046 #0 born (val@@entry=<optimized out>)
10047 #0 invalid (val@@entry=<optimized out>)
10051 Print only parameter values from function entry point. If value from function
10052 entry point is not known while the actual value is known, print the actual
10053 value for such parameter.
10055 #0 equal (val@@entry=5)
10056 #0 different (val@@entry=5)
10057 #0 lost (val@@entry=5)
10059 #0 invalid (val@@entry=<optimized out>)
10063 Print actual parameter values. If actual parameter value is not known while
10064 value from function entry point is known, print the entry point value for such
10068 #0 different (val=6)
10069 #0 lost (val@@entry=5)
10071 #0 invalid (val=<optimized out>)
10075 Always print both the actual parameter value and its value from function entry
10076 point, even if values of one or both are not available due to compiler
10079 #0 equal (val=5, val@@entry=5)
10080 #0 different (val=6, val@@entry=5)
10081 #0 lost (val=<optimized out>, val@@entry=5)
10082 #0 born (val=10, val@@entry=<optimized out>)
10083 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10087 Print the actual parameter value if it is known and also its value from
10088 function entry point if it is known. If neither is known, print for the actual
10089 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10090 values are known and identical, print the shortened
10091 @code{param=param@@entry=VALUE} notation.
10093 #0 equal (val=val@@entry=5)
10094 #0 different (val=6, val@@entry=5)
10095 #0 lost (val@@entry=5)
10097 #0 invalid (val=<optimized out>)
10101 Always print the actual parameter value. Print also its value from function
10102 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10103 if both values are known and identical, print the shortened
10104 @code{param=param@@entry=VALUE} notation.
10106 #0 equal (val=val@@entry=5)
10107 #0 different (val=6, val@@entry=5)
10108 #0 lost (val=<optimized out>, val@@entry=5)
10110 #0 invalid (val=<optimized out>)
10114 For analysis messages on possible failures of frame argument values at function
10115 entry resolution see @ref{set debug entry-values}.
10117 @item show print entry-values
10118 Show the method being used for printing of frame argument values at function
10121 @item set print repeats @var{number-of-repeats}
10122 @itemx set print repeats unlimited
10123 @cindex repeated array elements
10124 Set the threshold for suppressing display of repeated array
10125 elements. When the number of consecutive identical elements of an
10126 array exceeds the threshold, @value{GDBN} prints the string
10127 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10128 identical repetitions, instead of displaying the identical elements
10129 themselves. Setting the threshold to @code{unlimited} or zero will
10130 cause all elements to be individually printed. The default threshold
10133 @item show print repeats
10134 Display the current threshold for printing repeated identical
10137 @item set print null-stop
10138 @cindex @sc{null} elements in arrays
10139 Cause @value{GDBN} to stop printing the characters of an array when the first
10140 @sc{null} is encountered. This is useful when large arrays actually
10141 contain only short strings.
10142 The default is off.
10144 @item show print null-stop
10145 Show whether @value{GDBN} stops printing an array on the first
10146 @sc{null} character.
10148 @item set print pretty on
10149 @cindex print structures in indented form
10150 @cindex indentation in structure display
10151 Cause @value{GDBN} to print structures in an indented format with one member
10152 per line, like this:
10167 @item set print pretty off
10168 Cause @value{GDBN} to print structures in a compact format, like this:
10172 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10173 meat = 0x54 "Pork"@}
10178 This is the default format.
10180 @item show print pretty
10181 Show which format @value{GDBN} is using to print structures.
10183 @item set print sevenbit-strings on
10184 @cindex eight-bit characters in strings
10185 @cindex octal escapes in strings
10186 Print using only seven-bit characters; if this option is set,
10187 @value{GDBN} displays any eight-bit characters (in strings or
10188 character values) using the notation @code{\}@var{nnn}. This setting is
10189 best if you are working in English (@sc{ascii}) and you use the
10190 high-order bit of characters as a marker or ``meta'' bit.
10192 @item set print sevenbit-strings off
10193 Print full eight-bit characters. This allows the use of more
10194 international character sets, and is the default.
10196 @item show print sevenbit-strings
10197 Show whether or not @value{GDBN} is printing only seven-bit characters.
10199 @item set print union on
10200 @cindex unions in structures, printing
10201 Tell @value{GDBN} to print unions which are contained in structures
10202 and other unions. This is the default setting.
10204 @item set print union off
10205 Tell @value{GDBN} not to print unions which are contained in
10206 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10209 @item show print union
10210 Ask @value{GDBN} whether or not it will print unions which are contained in
10211 structures and other unions.
10213 For example, given the declarations
10216 typedef enum @{Tree, Bug@} Species;
10217 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10218 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10229 struct thing foo = @{Tree, @{Acorn@}@};
10233 with @code{set print union on} in effect @samp{p foo} would print
10236 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10240 and with @code{set print union off} in effect it would print
10243 $1 = @{it = Tree, form = @{...@}@}
10247 @code{set print union} affects programs written in C-like languages
10253 These settings are of interest when debugging C@t{++} programs:
10256 @cindex demangling C@t{++} names
10257 @item set print demangle
10258 @itemx set print demangle on
10259 Print C@t{++} names in their source form rather than in the encoded
10260 (``mangled'') form passed to the assembler and linker for type-safe
10261 linkage. The default is on.
10263 @item show print demangle
10264 Show whether C@t{++} names are printed in mangled or demangled form.
10266 @item set print asm-demangle
10267 @itemx set print asm-demangle on
10268 Print C@t{++} names in their source form rather than their mangled form, even
10269 in assembler code printouts such as instruction disassemblies.
10270 The default is off.
10272 @item show print asm-demangle
10273 Show whether C@t{++} names in assembly listings are printed in mangled
10276 @cindex C@t{++} symbol decoding style
10277 @cindex symbol decoding style, C@t{++}
10278 @kindex set demangle-style
10279 @item set demangle-style @var{style}
10280 Choose among several encoding schemes used by different compilers to
10281 represent C@t{++} names. The choices for @var{style} are currently:
10285 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10286 This is the default.
10289 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10292 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10295 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10298 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10299 @strong{Warning:} this setting alone is not sufficient to allow
10300 debugging @code{cfront}-generated executables. @value{GDBN} would
10301 require further enhancement to permit that.
10304 If you omit @var{style}, you will see a list of possible formats.
10306 @item show demangle-style
10307 Display the encoding style currently in use for decoding C@t{++} symbols.
10309 @item set print object
10310 @itemx set print object on
10311 @cindex derived type of an object, printing
10312 @cindex display derived types
10313 When displaying a pointer to an object, identify the @emph{actual}
10314 (derived) type of the object rather than the @emph{declared} type, using
10315 the virtual function table. Note that the virtual function table is
10316 required---this feature can only work for objects that have run-time
10317 type identification; a single virtual method in the object's declared
10318 type is sufficient. Note that this setting is also taken into account when
10319 working with variable objects via MI (@pxref{GDB/MI}).
10321 @item set print object off
10322 Display only the declared type of objects, without reference to the
10323 virtual function table. This is the default setting.
10325 @item show print object
10326 Show whether actual, or declared, object types are displayed.
10328 @item set print static-members
10329 @itemx set print static-members on
10330 @cindex static members of C@t{++} objects
10331 Print static members when displaying a C@t{++} object. The default is on.
10333 @item set print static-members off
10334 Do not print static members when displaying a C@t{++} object.
10336 @item show print static-members
10337 Show whether C@t{++} static members are printed or not.
10339 @item set print pascal_static-members
10340 @itemx set print pascal_static-members on
10341 @cindex static members of Pascal objects
10342 @cindex Pascal objects, static members display
10343 Print static members when displaying a Pascal object. The default is on.
10345 @item set print pascal_static-members off
10346 Do not print static members when displaying a Pascal object.
10348 @item show print pascal_static-members
10349 Show whether Pascal static members are printed or not.
10351 @c These don't work with HP ANSI C++ yet.
10352 @item set print vtbl
10353 @itemx set print vtbl on
10354 @cindex pretty print C@t{++} virtual function tables
10355 @cindex virtual functions (C@t{++}) display
10356 @cindex VTBL display
10357 Pretty print C@t{++} virtual function tables. The default is off.
10358 (The @code{vtbl} commands do not work on programs compiled with the HP
10359 ANSI C@t{++} compiler (@code{aCC}).)
10361 @item set print vtbl off
10362 Do not pretty print C@t{++} virtual function tables.
10364 @item show print vtbl
10365 Show whether C@t{++} virtual function tables are pretty printed, or not.
10368 @node Pretty Printing
10369 @section Pretty Printing
10371 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10372 Python code. It greatly simplifies the display of complex objects. This
10373 mechanism works for both MI and the CLI.
10376 * Pretty-Printer Introduction:: Introduction to pretty-printers
10377 * Pretty-Printer Example:: An example pretty-printer
10378 * Pretty-Printer Commands:: Pretty-printer commands
10381 @node Pretty-Printer Introduction
10382 @subsection Pretty-Printer Introduction
10384 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10385 registered for the value. If there is then @value{GDBN} invokes the
10386 pretty-printer to print the value. Otherwise the value is printed normally.
10388 Pretty-printers are normally named. This makes them easy to manage.
10389 The @samp{info pretty-printer} command will list all the installed
10390 pretty-printers with their names.
10391 If a pretty-printer can handle multiple data types, then its
10392 @dfn{subprinters} are the printers for the individual data types.
10393 Each such subprinter has its own name.
10394 The format of the name is @var{printer-name};@var{subprinter-name}.
10396 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10397 Typically they are automatically loaded and registered when the corresponding
10398 debug information is loaded, thus making them available without having to
10399 do anything special.
10401 There are three places where a pretty-printer can be registered.
10405 Pretty-printers registered globally are available when debugging
10409 Pretty-printers registered with a program space are available only
10410 when debugging that program.
10411 @xref{Progspaces In Python}, for more details on program spaces in Python.
10414 Pretty-printers registered with an objfile are loaded and unloaded
10415 with the corresponding objfile (e.g., shared library).
10416 @xref{Objfiles In Python}, for more details on objfiles in Python.
10419 @xref{Selecting Pretty-Printers}, for further information on how
10420 pretty-printers are selected,
10422 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10425 @node Pretty-Printer Example
10426 @subsection Pretty-Printer Example
10428 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10431 (@value{GDBP}) print s
10433 static npos = 4294967295,
10435 <std::allocator<char>> = @{
10436 <__gnu_cxx::new_allocator<char>> = @{
10437 <No data fields>@}, <No data fields>
10439 members of std::basic_string<char, std::char_traits<char>,
10440 std::allocator<char> >::_Alloc_hider:
10441 _M_p = 0x804a014 "abcd"
10446 With a pretty-printer for @code{std::string} only the contents are printed:
10449 (@value{GDBP}) print s
10453 @node Pretty-Printer Commands
10454 @subsection Pretty-Printer Commands
10455 @cindex pretty-printer commands
10458 @kindex info pretty-printer
10459 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10460 Print the list of installed pretty-printers.
10461 This includes disabled pretty-printers, which are marked as such.
10463 @var{object-regexp} is a regular expression matching the objects
10464 whose pretty-printers to list.
10465 Objects can be @code{global}, the program space's file
10466 (@pxref{Progspaces In Python}),
10467 and the object files within that program space (@pxref{Objfiles In Python}).
10468 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10469 looks up a printer from these three objects.
10471 @var{name-regexp} is a regular expression matching the name of the printers
10474 @kindex disable pretty-printer
10475 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10476 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10477 A disabled pretty-printer is not forgotten, it may be enabled again later.
10479 @kindex enable pretty-printer
10480 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10481 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10486 Suppose we have three pretty-printers installed: one from library1.so
10487 named @code{foo} that prints objects of type @code{foo}, and
10488 another from library2.so named @code{bar} that prints two types of objects,
10489 @code{bar1} and @code{bar2}.
10492 (gdb) info pretty-printer
10499 (gdb) info pretty-printer library2
10504 (gdb) disable pretty-printer library1
10506 2 of 3 printers enabled
10507 (gdb) info pretty-printer
10514 (gdb) disable pretty-printer library2 bar:bar1
10516 1 of 3 printers enabled
10517 (gdb) info pretty-printer library2
10524 (gdb) disable pretty-printer library2 bar
10526 0 of 3 printers enabled
10527 (gdb) info pretty-printer library2
10536 Note that for @code{bar} the entire printer can be disabled,
10537 as can each individual subprinter.
10539 @node Value History
10540 @section Value History
10542 @cindex value history
10543 @cindex history of values printed by @value{GDBN}
10544 Values printed by the @code{print} command are saved in the @value{GDBN}
10545 @dfn{value history}. This allows you to refer to them in other expressions.
10546 Values are kept until the symbol table is re-read or discarded
10547 (for example with the @code{file} or @code{symbol-file} commands).
10548 When the symbol table changes, the value history is discarded,
10549 since the values may contain pointers back to the types defined in the
10554 @cindex history number
10555 The values printed are given @dfn{history numbers} by which you can
10556 refer to them. These are successive integers starting with one.
10557 @code{print} shows you the history number assigned to a value by
10558 printing @samp{$@var{num} = } before the value; here @var{num} is the
10561 To refer to any previous value, use @samp{$} followed by the value's
10562 history number. The way @code{print} labels its output is designed to
10563 remind you of this. Just @code{$} refers to the most recent value in
10564 the history, and @code{$$} refers to the value before that.
10565 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10566 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10567 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10569 For example, suppose you have just printed a pointer to a structure and
10570 want to see the contents of the structure. It suffices to type
10576 If you have a chain of structures where the component @code{next} points
10577 to the next one, you can print the contents of the next one with this:
10584 You can print successive links in the chain by repeating this
10585 command---which you can do by just typing @key{RET}.
10587 Note that the history records values, not expressions. If the value of
10588 @code{x} is 4 and you type these commands:
10596 then the value recorded in the value history by the @code{print} command
10597 remains 4 even though the value of @code{x} has changed.
10600 @kindex show values
10602 Print the last ten values in the value history, with their item numbers.
10603 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10604 values} does not change the history.
10606 @item show values @var{n}
10607 Print ten history values centered on history item number @var{n}.
10609 @item show values +
10610 Print ten history values just after the values last printed. If no more
10611 values are available, @code{show values +} produces no display.
10614 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10615 same effect as @samp{show values +}.
10617 @node Convenience Vars
10618 @section Convenience Variables
10620 @cindex convenience variables
10621 @cindex user-defined variables
10622 @value{GDBN} provides @dfn{convenience variables} that you can use within
10623 @value{GDBN} to hold on to a value and refer to it later. These variables
10624 exist entirely within @value{GDBN}; they are not part of your program, and
10625 setting a convenience variable has no direct effect on further execution
10626 of your program. That is why you can use them freely.
10628 Convenience variables are prefixed with @samp{$}. Any name preceded by
10629 @samp{$} can be used for a convenience variable, unless it is one of
10630 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10631 (Value history references, in contrast, are @emph{numbers} preceded
10632 by @samp{$}. @xref{Value History, ,Value History}.)
10634 You can save a value in a convenience variable with an assignment
10635 expression, just as you would set a variable in your program.
10639 set $foo = *object_ptr
10643 would save in @code{$foo} the value contained in the object pointed to by
10646 Using a convenience variable for the first time creates it, but its
10647 value is @code{void} until you assign a new value. You can alter the
10648 value with another assignment at any time.
10650 Convenience variables have no fixed types. You can assign a convenience
10651 variable any type of value, including structures and arrays, even if
10652 that variable already has a value of a different type. The convenience
10653 variable, when used as an expression, has the type of its current value.
10656 @kindex show convenience
10657 @cindex show all user variables and functions
10658 @item show convenience
10659 Print a list of convenience variables used so far, and their values,
10660 as well as a list of the convenience functions.
10661 Abbreviated @code{show conv}.
10663 @kindex init-if-undefined
10664 @cindex convenience variables, initializing
10665 @item init-if-undefined $@var{variable} = @var{expression}
10666 Set a convenience variable if it has not already been set. This is useful
10667 for user-defined commands that keep some state. It is similar, in concept,
10668 to using local static variables with initializers in C (except that
10669 convenience variables are global). It can also be used to allow users to
10670 override default values used in a command script.
10672 If the variable is already defined then the expression is not evaluated so
10673 any side-effects do not occur.
10676 One of the ways to use a convenience variable is as a counter to be
10677 incremented or a pointer to be advanced. For example, to print
10678 a field from successive elements of an array of structures:
10682 print bar[$i++]->contents
10686 Repeat that command by typing @key{RET}.
10688 Some convenience variables are created automatically by @value{GDBN} and given
10689 values likely to be useful.
10692 @vindex $_@r{, convenience variable}
10694 The variable @code{$_} is automatically set by the @code{x} command to
10695 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10696 commands which provide a default address for @code{x} to examine also
10697 set @code{$_} to that address; these commands include @code{info line}
10698 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10699 except when set by the @code{x} command, in which case it is a pointer
10700 to the type of @code{$__}.
10702 @vindex $__@r{, convenience variable}
10704 The variable @code{$__} is automatically set by the @code{x} command
10705 to the value found in the last address examined. Its type is chosen
10706 to match the format in which the data was printed.
10709 @vindex $_exitcode@r{, convenience variable}
10710 When the program being debugged terminates normally, @value{GDBN}
10711 automatically sets this variable to the exit code of the program, and
10712 resets @code{$_exitsignal} to @code{void}.
10715 @vindex $_exitsignal@r{, convenience variable}
10716 When the program being debugged dies due to an uncaught signal,
10717 @value{GDBN} automatically sets this variable to that signal's number,
10718 and resets @code{$_exitcode} to @code{void}.
10720 To distinguish between whether the program being debugged has exited
10721 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10722 @code{$_exitsignal} is not @code{void}), the convenience function
10723 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10724 Functions}). For example, considering the following source code:
10727 #include <signal.h>
10730 main (int argc, char *argv[])
10737 A valid way of telling whether the program being debugged has exited
10738 or signalled would be:
10741 (@value{GDBP}) define has_exited_or_signalled
10742 Type commands for definition of ``has_exited_or_signalled''.
10743 End with a line saying just ``end''.
10744 >if $_isvoid ($_exitsignal)
10745 >echo The program has exited\n
10747 >echo The program has signalled\n
10753 Program terminated with signal SIGALRM, Alarm clock.
10754 The program no longer exists.
10755 (@value{GDBP}) has_exited_or_signalled
10756 The program has signalled
10759 As can be seen, @value{GDBN} correctly informs that the program being
10760 debugged has signalled, since it calls @code{raise} and raises a
10761 @code{SIGALRM} signal. If the program being debugged had not called
10762 @code{raise}, then @value{GDBN} would report a normal exit:
10765 (@value{GDBP}) has_exited_or_signalled
10766 The program has exited
10770 The variable @code{$_exception} is set to the exception object being
10771 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10774 @itemx $_probe_arg0@dots{}$_probe_arg11
10775 Arguments to a static probe. @xref{Static Probe Points}.
10778 @vindex $_sdata@r{, inspect, convenience variable}
10779 The variable @code{$_sdata} contains extra collected static tracepoint
10780 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10781 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10782 if extra static tracepoint data has not been collected.
10785 @vindex $_siginfo@r{, convenience variable}
10786 The variable @code{$_siginfo} contains extra signal information
10787 (@pxref{extra signal information}). Note that @code{$_siginfo}
10788 could be empty, if the application has not yet received any signals.
10789 For example, it will be empty before you execute the @code{run} command.
10792 @vindex $_tlb@r{, convenience variable}
10793 The variable @code{$_tlb} is automatically set when debugging
10794 applications running on MS-Windows in native mode or connected to
10795 gdbserver that supports the @code{qGetTIBAddr} request.
10796 @xref{General Query Packets}.
10797 This variable contains the address of the thread information block.
10800 The number of the current inferior. @xref{Inferiors and
10801 Programs, ,Debugging Multiple Inferiors and Programs}.
10804 The thread number of the current thread. @xref{thread numbers}.
10807 The global number of the current thread. @xref{global thread numbers}.
10811 @node Convenience Funs
10812 @section Convenience Functions
10814 @cindex convenience functions
10815 @value{GDBN} also supplies some @dfn{convenience functions}. These
10816 have a syntax similar to convenience variables. A convenience
10817 function can be used in an expression just like an ordinary function;
10818 however, a convenience function is implemented internally to
10821 These functions do not require @value{GDBN} to be configured with
10822 @code{Python} support, which means that they are always available.
10826 @item $_isvoid (@var{expr})
10827 @findex $_isvoid@r{, convenience function}
10828 Return one if the expression @var{expr} is @code{void}. Otherwise it
10831 A @code{void} expression is an expression where the type of the result
10832 is @code{void}. For example, you can examine a convenience variable
10833 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10837 (@value{GDBP}) print $_exitcode
10839 (@value{GDBP}) print $_isvoid ($_exitcode)
10842 Starting program: ./a.out
10843 [Inferior 1 (process 29572) exited normally]
10844 (@value{GDBP}) print $_exitcode
10846 (@value{GDBP}) print $_isvoid ($_exitcode)
10850 In the example above, we used @code{$_isvoid} to check whether
10851 @code{$_exitcode} is @code{void} before and after the execution of the
10852 program being debugged. Before the execution there is no exit code to
10853 be examined, therefore @code{$_exitcode} is @code{void}. After the
10854 execution the program being debugged returned zero, therefore
10855 @code{$_exitcode} is zero, which means that it is not @code{void}
10858 The @code{void} expression can also be a call of a function from the
10859 program being debugged. For example, given the following function:
10868 The result of calling it inside @value{GDBN} is @code{void}:
10871 (@value{GDBP}) print foo ()
10873 (@value{GDBP}) print $_isvoid (foo ())
10875 (@value{GDBP}) set $v = foo ()
10876 (@value{GDBP}) print $v
10878 (@value{GDBP}) print $_isvoid ($v)
10884 These functions require @value{GDBN} to be configured with
10885 @code{Python} support.
10889 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10890 @findex $_memeq@r{, convenience function}
10891 Returns one if the @var{length} bytes at the addresses given by
10892 @var{buf1} and @var{buf2} are equal.
10893 Otherwise it returns zero.
10895 @item $_regex(@var{str}, @var{regex})
10896 @findex $_regex@r{, convenience function}
10897 Returns one if the string @var{str} matches the regular expression
10898 @var{regex}. Otherwise it returns zero.
10899 The syntax of the regular expression is that specified by @code{Python}'s
10900 regular expression support.
10902 @item $_streq(@var{str1}, @var{str2})
10903 @findex $_streq@r{, convenience function}
10904 Returns one if the strings @var{str1} and @var{str2} are equal.
10905 Otherwise it returns zero.
10907 @item $_strlen(@var{str})
10908 @findex $_strlen@r{, convenience function}
10909 Returns the length of string @var{str}.
10911 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10912 @findex $_caller_is@r{, convenience function}
10913 Returns one if the calling function's name is equal to @var{name}.
10914 Otherwise it returns zero.
10916 If the optional argument @var{number_of_frames} is provided,
10917 it is the number of frames up in the stack to look.
10925 at testsuite/gdb.python/py-caller-is.c:21
10926 #1 0x00000000004005a0 in middle_func ()
10927 at testsuite/gdb.python/py-caller-is.c:27
10928 #2 0x00000000004005ab in top_func ()
10929 at testsuite/gdb.python/py-caller-is.c:33
10930 #3 0x00000000004005b6 in main ()
10931 at testsuite/gdb.python/py-caller-is.c:39
10932 (gdb) print $_caller_is ("middle_func")
10934 (gdb) print $_caller_is ("top_func", 2)
10938 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10939 @findex $_caller_matches@r{, convenience function}
10940 Returns one if the calling function's name matches the regular expression
10941 @var{regexp}. Otherwise it returns zero.
10943 If the optional argument @var{number_of_frames} is provided,
10944 it is the number of frames up in the stack to look.
10947 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10948 @findex $_any_caller_is@r{, convenience function}
10949 Returns one if any calling function's name is equal to @var{name}.
10950 Otherwise it returns zero.
10952 If the optional argument @var{number_of_frames} is provided,
10953 it is the number of frames up in the stack to look.
10956 This function differs from @code{$_caller_is} in that this function
10957 checks all stack frames from the immediate caller to the frame specified
10958 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10959 frame specified by @var{number_of_frames}.
10961 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10962 @findex $_any_caller_matches@r{, convenience function}
10963 Returns one if any calling function's name matches the regular expression
10964 @var{regexp}. Otherwise it returns zero.
10966 If the optional argument @var{number_of_frames} is provided,
10967 it is the number of frames up in the stack to look.
10970 This function differs from @code{$_caller_matches} in that this function
10971 checks all stack frames from the immediate caller to the frame specified
10972 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10973 frame specified by @var{number_of_frames}.
10975 @item $_as_string(@var{value})
10976 @findex $_as_string@r{, convenience function}
10977 Return the string representation of @var{value}.
10979 This function is useful to obtain the textual label (enumerator) of an
10980 enumeration value. For example, assuming the variable @var{node} is of
10981 an enumerated type:
10984 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
10985 Visiting node of type NODE_INTEGER
10990 @value{GDBN} provides the ability to list and get help on
10991 convenience functions.
10994 @item help function
10995 @kindex help function
10996 @cindex show all convenience functions
10997 Print a list of all convenience functions.
11004 You can refer to machine register contents, in expressions, as variables
11005 with names starting with @samp{$}. The names of registers are different
11006 for each machine; use @code{info registers} to see the names used on
11010 @kindex info registers
11011 @item info registers
11012 Print the names and values of all registers except floating-point
11013 and vector registers (in the selected stack frame).
11015 @kindex info all-registers
11016 @cindex floating point registers
11017 @item info all-registers
11018 Print the names and values of all registers, including floating-point
11019 and vector registers (in the selected stack frame).
11021 @item info registers @var{regname} @dots{}
11022 Print the @dfn{relativized} value of each specified register @var{regname}.
11023 As discussed in detail below, register values are normally relative to
11024 the selected stack frame. The @var{regname} may be any register name valid on
11025 the machine you are using, with or without the initial @samp{$}.
11028 @anchor{standard registers}
11029 @cindex stack pointer register
11030 @cindex program counter register
11031 @cindex process status register
11032 @cindex frame pointer register
11033 @cindex standard registers
11034 @value{GDBN} has four ``standard'' register names that are available (in
11035 expressions) on most machines---whenever they do not conflict with an
11036 architecture's canonical mnemonics for registers. The register names
11037 @code{$pc} and @code{$sp} are used for the program counter register and
11038 the stack pointer. @code{$fp} is used for a register that contains a
11039 pointer to the current stack frame, and @code{$ps} is used for a
11040 register that contains the processor status. For example,
11041 you could print the program counter in hex with
11048 or print the instruction to be executed next with
11055 or add four to the stack pointer@footnote{This is a way of removing
11056 one word from the stack, on machines where stacks grow downward in
11057 memory (most machines, nowadays). This assumes that the innermost
11058 stack frame is selected; setting @code{$sp} is not allowed when other
11059 stack frames are selected. To pop entire frames off the stack,
11060 regardless of machine architecture, use @code{return};
11061 see @ref{Returning, ,Returning from a Function}.} with
11067 Whenever possible, these four standard register names are available on
11068 your machine even though the machine has different canonical mnemonics,
11069 so long as there is no conflict. The @code{info registers} command
11070 shows the canonical names. For example, on the SPARC, @code{info
11071 registers} displays the processor status register as @code{$psr} but you
11072 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11073 is an alias for the @sc{eflags} register.
11075 @value{GDBN} always considers the contents of an ordinary register as an
11076 integer when the register is examined in this way. Some machines have
11077 special registers which can hold nothing but floating point; these
11078 registers are considered to have floating point values. There is no way
11079 to refer to the contents of an ordinary register as floating point value
11080 (although you can @emph{print} it as a floating point value with
11081 @samp{print/f $@var{regname}}).
11083 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11084 means that the data format in which the register contents are saved by
11085 the operating system is not the same one that your program normally
11086 sees. For example, the registers of the 68881 floating point
11087 coprocessor are always saved in ``extended'' (raw) format, but all C
11088 programs expect to work with ``double'' (virtual) format. In such
11089 cases, @value{GDBN} normally works with the virtual format only (the format
11090 that makes sense for your program), but the @code{info registers} command
11091 prints the data in both formats.
11093 @cindex SSE registers (x86)
11094 @cindex MMX registers (x86)
11095 Some machines have special registers whose contents can be interpreted
11096 in several different ways. For example, modern x86-based machines
11097 have SSE and MMX registers that can hold several values packed
11098 together in several different formats. @value{GDBN} refers to such
11099 registers in @code{struct} notation:
11102 (@value{GDBP}) print $xmm1
11104 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11105 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11106 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11107 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11108 v4_int32 = @{0, 20657912, 11, 13@},
11109 v2_int64 = @{88725056443645952, 55834574859@},
11110 uint128 = 0x0000000d0000000b013b36f800000000
11115 To set values of such registers, you need to tell @value{GDBN} which
11116 view of the register you wish to change, as if you were assigning
11117 value to a @code{struct} member:
11120 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11123 Normally, register values are relative to the selected stack frame
11124 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11125 value that the register would contain if all stack frames farther in
11126 were exited and their saved registers restored. In order to see the
11127 true contents of hardware registers, you must select the innermost
11128 frame (with @samp{frame 0}).
11130 @cindex caller-saved registers
11131 @cindex call-clobbered registers
11132 @cindex volatile registers
11133 @cindex <not saved> values
11134 Usually ABIs reserve some registers as not needed to be saved by the
11135 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11136 registers). It may therefore not be possible for @value{GDBN} to know
11137 the value a register had before the call (in other words, in the outer
11138 frame), if the register value has since been changed by the callee.
11139 @value{GDBN} tries to deduce where the inner frame saved
11140 (``callee-saved'') registers, from the debug info, unwind info, or the
11141 machine code generated by your compiler. If some register is not
11142 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11143 its own knowledge of the ABI, or because the debug/unwind info
11144 explicitly says the register's value is undefined), @value{GDBN}
11145 displays @w{@samp{<not saved>}} as the register's value. With targets
11146 that @value{GDBN} has no knowledge of the register saving convention,
11147 if a register was not saved by the callee, then its value and location
11148 in the outer frame are assumed to be the same of the inner frame.
11149 This is usually harmless, because if the register is call-clobbered,
11150 the caller either does not care what is in the register after the
11151 call, or has code to restore the value that it does care about. Note,
11152 however, that if you change such a register in the outer frame, you
11153 may also be affecting the inner frame. Also, the more ``outer'' the
11154 frame is you're looking at, the more likely a call-clobbered
11155 register's value is to be wrong, in the sense that it doesn't actually
11156 represent the value the register had just before the call.
11158 @node Floating Point Hardware
11159 @section Floating Point Hardware
11160 @cindex floating point
11162 Depending on the configuration, @value{GDBN} may be able to give
11163 you more information about the status of the floating point hardware.
11168 Display hardware-dependent information about the floating
11169 point unit. The exact contents and layout vary depending on the
11170 floating point chip. Currently, @samp{info float} is supported on
11171 the ARM and x86 machines.
11175 @section Vector Unit
11176 @cindex vector unit
11178 Depending on the configuration, @value{GDBN} may be able to give you
11179 more information about the status of the vector unit.
11182 @kindex info vector
11184 Display information about the vector unit. The exact contents and
11185 layout vary depending on the hardware.
11188 @node OS Information
11189 @section Operating System Auxiliary Information
11190 @cindex OS information
11192 @value{GDBN} provides interfaces to useful OS facilities that can help
11193 you debug your program.
11195 @cindex auxiliary vector
11196 @cindex vector, auxiliary
11197 Some operating systems supply an @dfn{auxiliary vector} to programs at
11198 startup. This is akin to the arguments and environment that you
11199 specify for a program, but contains a system-dependent variety of
11200 binary values that tell system libraries important details about the
11201 hardware, operating system, and process. Each value's purpose is
11202 identified by an integer tag; the meanings are well-known but system-specific.
11203 Depending on the configuration and operating system facilities,
11204 @value{GDBN} may be able to show you this information. For remote
11205 targets, this functionality may further depend on the remote stub's
11206 support of the @samp{qXfer:auxv:read} packet, see
11207 @ref{qXfer auxiliary vector read}.
11212 Display the auxiliary vector of the inferior, which can be either a
11213 live process or a core dump file. @value{GDBN} prints each tag value
11214 numerically, and also shows names and text descriptions for recognized
11215 tags. Some values in the vector are numbers, some bit masks, and some
11216 pointers to strings or other data. @value{GDBN} displays each value in the
11217 most appropriate form for a recognized tag, and in hexadecimal for
11218 an unrecognized tag.
11221 On some targets, @value{GDBN} can access operating system-specific
11222 information and show it to you. The types of information available
11223 will differ depending on the type of operating system running on the
11224 target. The mechanism used to fetch the data is described in
11225 @ref{Operating System Information}. For remote targets, this
11226 functionality depends on the remote stub's support of the
11227 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11231 @item info os @var{infotype}
11233 Display OS information of the requested type.
11235 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11237 @anchor{linux info os infotypes}
11239 @kindex info os cpus
11241 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11242 the available fields from /proc/cpuinfo. For each supported architecture
11243 different fields are available. Two common entries are processor which gives
11244 CPU number and bogomips; a system constant that is calculated during
11245 kernel initialization.
11247 @kindex info os files
11249 Display the list of open file descriptors on the target. For each
11250 file descriptor, @value{GDBN} prints the identifier of the process
11251 owning the descriptor, the command of the owning process, the value
11252 of the descriptor, and the target of the descriptor.
11254 @kindex info os modules
11256 Display the list of all loaded kernel modules on the target. For each
11257 module, @value{GDBN} prints the module name, the size of the module in
11258 bytes, the number of times the module is used, the dependencies of the
11259 module, the status of the module, and the address of the loaded module
11262 @kindex info os msg
11264 Display the list of all System V message queues on the target. For each
11265 message queue, @value{GDBN} prints the message queue key, the message
11266 queue identifier, the access permissions, the current number of bytes
11267 on the queue, the current number of messages on the queue, the processes
11268 that last sent and received a message on the queue, the user and group
11269 of the owner and creator of the message queue, the times at which a
11270 message was last sent and received on the queue, and the time at which
11271 the message queue was last changed.
11273 @kindex info os processes
11275 Display the list of processes on the target. For each process,
11276 @value{GDBN} prints the process identifier, the name of the user, the
11277 command corresponding to the process, and the list of processor cores
11278 that the process is currently running on. (To understand what these
11279 properties mean, for this and the following info types, please consult
11280 the general @sc{gnu}/Linux documentation.)
11282 @kindex info os procgroups
11284 Display the list of process groups on the target. For each process,
11285 @value{GDBN} prints the identifier of the process group that it belongs
11286 to, the command corresponding to the process group leader, the process
11287 identifier, and the command line of the process. The list is sorted
11288 first by the process group identifier, then by the process identifier,
11289 so that processes belonging to the same process group are grouped together
11290 and the process group leader is listed first.
11292 @kindex info os semaphores
11294 Display the list of all System V semaphore sets on the target. For each
11295 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11296 set identifier, the access permissions, the number of semaphores in the
11297 set, the user and group of the owner and creator of the semaphore set,
11298 and the times at which the semaphore set was operated upon and changed.
11300 @kindex info os shm
11302 Display the list of all System V shared-memory regions on the target.
11303 For each shared-memory region, @value{GDBN} prints the region key,
11304 the shared-memory identifier, the access permissions, the size of the
11305 region, the process that created the region, the process that last
11306 attached to or detached from the region, the current number of live
11307 attaches to the region, and the times at which the region was last
11308 attached to, detach from, and changed.
11310 @kindex info os sockets
11312 Display the list of Internet-domain sockets on the target. For each
11313 socket, @value{GDBN} prints the address and port of the local and
11314 remote endpoints, the current state of the connection, the creator of
11315 the socket, the IP address family of the socket, and the type of the
11318 @kindex info os threads
11320 Display the list of threads running on the target. For each thread,
11321 @value{GDBN} prints the identifier of the process that the thread
11322 belongs to, the command of the process, the thread identifier, and the
11323 processor core that it is currently running on. The main thread of a
11324 process is not listed.
11328 If @var{infotype} is omitted, then list the possible values for
11329 @var{infotype} and the kind of OS information available for each
11330 @var{infotype}. If the target does not return a list of possible
11331 types, this command will report an error.
11334 @node Memory Region Attributes
11335 @section Memory Region Attributes
11336 @cindex memory region attributes
11338 @dfn{Memory region attributes} allow you to describe special handling
11339 required by regions of your target's memory. @value{GDBN} uses
11340 attributes to determine whether to allow certain types of memory
11341 accesses; whether to use specific width accesses; and whether to cache
11342 target memory. By default the description of memory regions is
11343 fetched from the target (if the current target supports this), but the
11344 user can override the fetched regions.
11346 Defined memory regions can be individually enabled and disabled. When a
11347 memory region is disabled, @value{GDBN} uses the default attributes when
11348 accessing memory in that region. Similarly, if no memory regions have
11349 been defined, @value{GDBN} uses the default attributes when accessing
11352 When a memory region is defined, it is given a number to identify it;
11353 to enable, disable, or remove a memory region, you specify that number.
11357 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11358 Define a memory region bounded by @var{lower} and @var{upper} with
11359 attributes @var{attributes}@dots{}, and add it to the list of regions
11360 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11361 case: it is treated as the target's maximum memory address.
11362 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11365 Discard any user changes to the memory regions and use target-supplied
11366 regions, if available, or no regions if the target does not support.
11369 @item delete mem @var{nums}@dots{}
11370 Remove memory regions @var{nums}@dots{} from the list of regions
11371 monitored by @value{GDBN}.
11373 @kindex disable mem
11374 @item disable mem @var{nums}@dots{}
11375 Disable monitoring of memory regions @var{nums}@dots{}.
11376 A disabled memory region is not forgotten.
11377 It may be enabled again later.
11380 @item enable mem @var{nums}@dots{}
11381 Enable monitoring of memory regions @var{nums}@dots{}.
11385 Print a table of all defined memory regions, with the following columns
11389 @item Memory Region Number
11390 @item Enabled or Disabled.
11391 Enabled memory regions are marked with @samp{y}.
11392 Disabled memory regions are marked with @samp{n}.
11395 The address defining the inclusive lower bound of the memory region.
11398 The address defining the exclusive upper bound of the memory region.
11401 The list of attributes set for this memory region.
11406 @subsection Attributes
11408 @subsubsection Memory Access Mode
11409 The access mode attributes set whether @value{GDBN} may make read or
11410 write accesses to a memory region.
11412 While these attributes prevent @value{GDBN} from performing invalid
11413 memory accesses, they do nothing to prevent the target system, I/O DMA,
11414 etc.@: from accessing memory.
11418 Memory is read only.
11420 Memory is write only.
11422 Memory is read/write. This is the default.
11425 @subsubsection Memory Access Size
11426 The access size attribute tells @value{GDBN} to use specific sized
11427 accesses in the memory region. Often memory mapped device registers
11428 require specific sized accesses. If no access size attribute is
11429 specified, @value{GDBN} may use accesses of any size.
11433 Use 8 bit memory accesses.
11435 Use 16 bit memory accesses.
11437 Use 32 bit memory accesses.
11439 Use 64 bit memory accesses.
11442 @c @subsubsection Hardware/Software Breakpoints
11443 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11444 @c will use hardware or software breakpoints for the internal breakpoints
11445 @c used by the step, next, finish, until, etc. commands.
11449 @c Always use hardware breakpoints
11450 @c @item swbreak (default)
11453 @subsubsection Data Cache
11454 The data cache attributes set whether @value{GDBN} will cache target
11455 memory. While this generally improves performance by reducing debug
11456 protocol overhead, it can lead to incorrect results because @value{GDBN}
11457 does not know about volatile variables or memory mapped device
11462 Enable @value{GDBN} to cache target memory.
11464 Disable @value{GDBN} from caching target memory. This is the default.
11467 @subsection Memory Access Checking
11468 @value{GDBN} can be instructed to refuse accesses to memory that is
11469 not explicitly described. This can be useful if accessing such
11470 regions has undesired effects for a specific target, or to provide
11471 better error checking. The following commands control this behaviour.
11474 @kindex set mem inaccessible-by-default
11475 @item set mem inaccessible-by-default [on|off]
11476 If @code{on} is specified, make @value{GDBN} treat memory not
11477 explicitly described by the memory ranges as non-existent and refuse accesses
11478 to such memory. The checks are only performed if there's at least one
11479 memory range defined. If @code{off} is specified, make @value{GDBN}
11480 treat the memory not explicitly described by the memory ranges as RAM.
11481 The default value is @code{on}.
11482 @kindex show mem inaccessible-by-default
11483 @item show mem inaccessible-by-default
11484 Show the current handling of accesses to unknown memory.
11488 @c @subsubsection Memory Write Verification
11489 @c The memory write verification attributes set whether @value{GDBN}
11490 @c will re-reads data after each write to verify the write was successful.
11494 @c @item noverify (default)
11497 @node Dump/Restore Files
11498 @section Copy Between Memory and a File
11499 @cindex dump/restore files
11500 @cindex append data to a file
11501 @cindex dump data to a file
11502 @cindex restore data from a file
11504 You can use the commands @code{dump}, @code{append}, and
11505 @code{restore} to copy data between target memory and a file. The
11506 @code{dump} and @code{append} commands write data to a file, and the
11507 @code{restore} command reads data from a file back into the inferior's
11508 memory. Files may be in binary, Motorola S-record, Intel hex,
11509 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11510 append to binary files, and cannot read from Verilog Hex files.
11515 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11516 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11517 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11518 or the value of @var{expr}, to @var{filename} in the given format.
11520 The @var{format} parameter may be any one of:
11527 Motorola S-record format.
11529 Tektronix Hex format.
11531 Verilog Hex format.
11534 @value{GDBN} uses the same definitions of these formats as the
11535 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11536 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11540 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11541 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11542 Append the contents of memory from @var{start_addr} to @var{end_addr},
11543 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11544 (@value{GDBN} can only append data to files in raw binary form.)
11547 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11548 Restore the contents of file @var{filename} into memory. The
11549 @code{restore} command can automatically recognize any known @sc{bfd}
11550 file format, except for raw binary. To restore a raw binary file you
11551 must specify the optional keyword @code{binary} after the filename.
11553 If @var{bias} is non-zero, its value will be added to the addresses
11554 contained in the file. Binary files always start at address zero, so
11555 they will be restored at address @var{bias}. Other bfd files have
11556 a built-in location; they will be restored at offset @var{bias}
11557 from that location.
11559 If @var{start} and/or @var{end} are non-zero, then only data between
11560 file offset @var{start} and file offset @var{end} will be restored.
11561 These offsets are relative to the addresses in the file, before
11562 the @var{bias} argument is applied.
11566 @node Core File Generation
11567 @section How to Produce a Core File from Your Program
11568 @cindex dump core from inferior
11570 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11571 image of a running process and its process status (register values
11572 etc.). Its primary use is post-mortem debugging of a program that
11573 crashed while it ran outside a debugger. A program that crashes
11574 automatically produces a core file, unless this feature is disabled by
11575 the user. @xref{Files}, for information on invoking @value{GDBN} in
11576 the post-mortem debugging mode.
11578 Occasionally, you may wish to produce a core file of the program you
11579 are debugging in order to preserve a snapshot of its state.
11580 @value{GDBN} has a special command for that.
11584 @kindex generate-core-file
11585 @item generate-core-file [@var{file}]
11586 @itemx gcore [@var{file}]
11587 Produce a core dump of the inferior process. The optional argument
11588 @var{file} specifies the file name where to put the core dump. If not
11589 specified, the file name defaults to @file{core.@var{pid}}, where
11590 @var{pid} is the inferior process ID.
11592 Note that this command is implemented only for some systems (as of
11593 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11595 On @sc{gnu}/Linux, this command can take into account the value of the
11596 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11597 dump (@pxref{set use-coredump-filter}), and by default honors the
11598 @code{VM_DONTDUMP} flag for mappings where it is present in the file
11599 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
11601 @kindex set use-coredump-filter
11602 @anchor{set use-coredump-filter}
11603 @item set use-coredump-filter on
11604 @itemx set use-coredump-filter off
11605 Enable or disable the use of the file
11606 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11607 files. This file is used by the Linux kernel to decide what types of
11608 memory mappings will be dumped or ignored when generating a core dump
11609 file. @var{pid} is the process ID of a currently running process.
11611 To make use of this feature, you have to write in the
11612 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11613 which is a bit mask representing the memory mapping types. If a bit
11614 is set in the bit mask, then the memory mappings of the corresponding
11615 types will be dumped; otherwise, they will be ignored. This
11616 configuration is inherited by child processes. For more information
11617 about the bits that can be set in the
11618 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11619 manpage of @code{core(5)}.
11621 By default, this option is @code{on}. If this option is turned
11622 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11623 and instead uses the same default value as the Linux kernel in order
11624 to decide which pages will be dumped in the core dump file. This
11625 value is currently @code{0x33}, which means that bits @code{0}
11626 (anonymous private mappings), @code{1} (anonymous shared mappings),
11627 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11628 This will cause these memory mappings to be dumped automatically.
11630 @kindex set dump-excluded-mappings
11631 @anchor{set dump-excluded-mappings}
11632 @item set dump-excluded-mappings on
11633 @itemx set dump-excluded-mappings off
11634 If @code{on} is specified, @value{GDBN} will dump memory mappings
11635 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
11636 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
11638 The default value is @code{off}.
11641 @node Character Sets
11642 @section Character Sets
11643 @cindex character sets
11645 @cindex translating between character sets
11646 @cindex host character set
11647 @cindex target character set
11649 If the program you are debugging uses a different character set to
11650 represent characters and strings than the one @value{GDBN} uses itself,
11651 @value{GDBN} can automatically translate between the character sets for
11652 you. The character set @value{GDBN} uses we call the @dfn{host
11653 character set}; the one the inferior program uses we call the
11654 @dfn{target character set}.
11656 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11657 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11658 remote protocol (@pxref{Remote Debugging}) to debug a program
11659 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11660 then the host character set is Latin-1, and the target character set is
11661 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11662 target-charset EBCDIC-US}, then @value{GDBN} translates between
11663 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11664 character and string literals in expressions.
11666 @value{GDBN} has no way to automatically recognize which character set
11667 the inferior program uses; you must tell it, using the @code{set
11668 target-charset} command, described below.
11670 Here are the commands for controlling @value{GDBN}'s character set
11674 @item set target-charset @var{charset}
11675 @kindex set target-charset
11676 Set the current target character set to @var{charset}. To display the
11677 list of supported target character sets, type
11678 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11680 @item set host-charset @var{charset}
11681 @kindex set host-charset
11682 Set the current host character set to @var{charset}.
11684 By default, @value{GDBN} uses a host character set appropriate to the
11685 system it is running on; you can override that default using the
11686 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11687 automatically determine the appropriate host character set. In this
11688 case, @value{GDBN} uses @samp{UTF-8}.
11690 @value{GDBN} can only use certain character sets as its host character
11691 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11692 @value{GDBN} will list the host character sets it supports.
11694 @item set charset @var{charset}
11695 @kindex set charset
11696 Set the current host and target character sets to @var{charset}. As
11697 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11698 @value{GDBN} will list the names of the character sets that can be used
11699 for both host and target.
11702 @kindex show charset
11703 Show the names of the current host and target character sets.
11705 @item show host-charset
11706 @kindex show host-charset
11707 Show the name of the current host character set.
11709 @item show target-charset
11710 @kindex show target-charset
11711 Show the name of the current target character set.
11713 @item set target-wide-charset @var{charset}
11714 @kindex set target-wide-charset
11715 Set the current target's wide character set to @var{charset}. This is
11716 the character set used by the target's @code{wchar_t} type. To
11717 display the list of supported wide character sets, type
11718 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11720 @item show target-wide-charset
11721 @kindex show target-wide-charset
11722 Show the name of the current target's wide character set.
11725 Here is an example of @value{GDBN}'s character set support in action.
11726 Assume that the following source code has been placed in the file
11727 @file{charset-test.c}:
11733 = @{72, 101, 108, 108, 111, 44, 32, 119,
11734 111, 114, 108, 100, 33, 10, 0@};
11735 char ibm1047_hello[]
11736 = @{200, 133, 147, 147, 150, 107, 64, 166,
11737 150, 153, 147, 132, 90, 37, 0@};
11741 printf ("Hello, world!\n");
11745 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11746 containing the string @samp{Hello, world!} followed by a newline,
11747 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11749 We compile the program, and invoke the debugger on it:
11752 $ gcc -g charset-test.c -o charset-test
11753 $ gdb -nw charset-test
11754 GNU gdb 2001-12-19-cvs
11755 Copyright 2001 Free Software Foundation, Inc.
11760 We can use the @code{show charset} command to see what character sets
11761 @value{GDBN} is currently using to interpret and display characters and
11765 (@value{GDBP}) show charset
11766 The current host and target character set is `ISO-8859-1'.
11770 For the sake of printing this manual, let's use @sc{ascii} as our
11771 initial character set:
11773 (@value{GDBP}) set charset ASCII
11774 (@value{GDBP}) show charset
11775 The current host and target character set is `ASCII'.
11779 Let's assume that @sc{ascii} is indeed the correct character set for our
11780 host system --- in other words, let's assume that if @value{GDBN} prints
11781 characters using the @sc{ascii} character set, our terminal will display
11782 them properly. Since our current target character set is also
11783 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11786 (@value{GDBP}) print ascii_hello
11787 $1 = 0x401698 "Hello, world!\n"
11788 (@value{GDBP}) print ascii_hello[0]
11793 @value{GDBN} uses the target character set for character and string
11794 literals you use in expressions:
11797 (@value{GDBP}) print '+'
11802 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11805 @value{GDBN} relies on the user to tell it which character set the
11806 target program uses. If we print @code{ibm1047_hello} while our target
11807 character set is still @sc{ascii}, we get jibberish:
11810 (@value{GDBP}) print ibm1047_hello
11811 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11812 (@value{GDBP}) print ibm1047_hello[0]
11817 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11818 @value{GDBN} tells us the character sets it supports:
11821 (@value{GDBP}) set target-charset
11822 ASCII EBCDIC-US IBM1047 ISO-8859-1
11823 (@value{GDBP}) set target-charset
11826 We can select @sc{ibm1047} as our target character set, and examine the
11827 program's strings again. Now the @sc{ascii} string is wrong, but
11828 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11829 target character set, @sc{ibm1047}, to the host character set,
11830 @sc{ascii}, and they display correctly:
11833 (@value{GDBP}) set target-charset IBM1047
11834 (@value{GDBP}) show charset
11835 The current host character set is `ASCII'.
11836 The current target character set is `IBM1047'.
11837 (@value{GDBP}) print ascii_hello
11838 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11839 (@value{GDBP}) print ascii_hello[0]
11841 (@value{GDBP}) print ibm1047_hello
11842 $8 = 0x4016a8 "Hello, world!\n"
11843 (@value{GDBP}) print ibm1047_hello[0]
11848 As above, @value{GDBN} uses the target character set for character and
11849 string literals you use in expressions:
11852 (@value{GDBP}) print '+'
11857 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11860 @node Caching Target Data
11861 @section Caching Data of Targets
11862 @cindex caching data of targets
11864 @value{GDBN} caches data exchanged between the debugger and a target.
11865 Each cache is associated with the address space of the inferior.
11866 @xref{Inferiors and Programs}, about inferior and address space.
11867 Such caching generally improves performance in remote debugging
11868 (@pxref{Remote Debugging}), because it reduces the overhead of the
11869 remote protocol by bundling memory reads and writes into large chunks.
11870 Unfortunately, simply caching everything would lead to incorrect results,
11871 since @value{GDBN} does not necessarily know anything about volatile
11872 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11873 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11875 Therefore, by default, @value{GDBN} only caches data
11876 known to be on the stack@footnote{In non-stop mode, it is moderately
11877 rare for a running thread to modify the stack of a stopped thread
11878 in a way that would interfere with a backtrace, and caching of
11879 stack reads provides a significant speed up of remote backtraces.} or
11880 in the code segment.
11881 Other regions of memory can be explicitly marked as
11882 cacheable; @pxref{Memory Region Attributes}.
11885 @kindex set remotecache
11886 @item set remotecache on
11887 @itemx set remotecache off
11888 This option no longer does anything; it exists for compatibility
11891 @kindex show remotecache
11892 @item show remotecache
11893 Show the current state of the obsolete remotecache flag.
11895 @kindex set stack-cache
11896 @item set stack-cache on
11897 @itemx set stack-cache off
11898 Enable or disable caching of stack accesses. When @code{on}, use
11899 caching. By default, this option is @code{on}.
11901 @kindex show stack-cache
11902 @item show stack-cache
11903 Show the current state of data caching for memory accesses.
11905 @kindex set code-cache
11906 @item set code-cache on
11907 @itemx set code-cache off
11908 Enable or disable caching of code segment accesses. When @code{on},
11909 use caching. By default, this option is @code{on}. This improves
11910 performance of disassembly in remote debugging.
11912 @kindex show code-cache
11913 @item show code-cache
11914 Show the current state of target memory cache for code segment
11917 @kindex info dcache
11918 @item info dcache @r{[}line@r{]}
11919 Print the information about the performance of data cache of the
11920 current inferior's address space. The information displayed
11921 includes the dcache width and depth, and for each cache line, its
11922 number, address, and how many times it was referenced. This
11923 command is useful for debugging the data cache operation.
11925 If a line number is specified, the contents of that line will be
11928 @item set dcache size @var{size}
11929 @cindex dcache size
11930 @kindex set dcache size
11931 Set maximum number of entries in dcache (dcache depth above).
11933 @item set dcache line-size @var{line-size}
11934 @cindex dcache line-size
11935 @kindex set dcache line-size
11936 Set number of bytes each dcache entry caches (dcache width above).
11937 Must be a power of 2.
11939 @item show dcache size
11940 @kindex show dcache size
11941 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11943 @item show dcache line-size
11944 @kindex show dcache line-size
11945 Show default size of dcache lines.
11949 @node Searching Memory
11950 @section Search Memory
11951 @cindex searching memory
11953 Memory can be searched for a particular sequence of bytes with the
11954 @code{find} command.
11958 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11959 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11960 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11961 etc. The search begins at address @var{start_addr} and continues for either
11962 @var{len} bytes or through to @var{end_addr} inclusive.
11965 @var{s} and @var{n} are optional parameters.
11966 They may be specified in either order, apart or together.
11969 @item @var{s}, search query size
11970 The size of each search query value.
11976 halfwords (two bytes)
11980 giant words (eight bytes)
11983 All values are interpreted in the current language.
11984 This means, for example, that if the current source language is C/C@t{++}
11985 then searching for the string ``hello'' includes the trailing '\0'.
11986 The null terminator can be removed from searching by using casts,
11987 e.g.: @samp{@{char[5]@}"hello"}.
11989 If the value size is not specified, it is taken from the
11990 value's type in the current language.
11991 This is useful when one wants to specify the search
11992 pattern as a mixture of types.
11993 Note that this means, for example, that in the case of C-like languages
11994 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11995 which is typically four bytes.
11997 @item @var{n}, maximum number of finds
11998 The maximum number of matches to print. The default is to print all finds.
12001 You can use strings as search values. Quote them with double-quotes
12003 The string value is copied into the search pattern byte by byte,
12004 regardless of the endianness of the target and the size specification.
12006 The address of each match found is printed as well as a count of the
12007 number of matches found.
12009 The address of the last value found is stored in convenience variable
12011 A count of the number of matches is stored in @samp{$numfound}.
12013 For example, if stopped at the @code{printf} in this function:
12019 static char hello[] = "hello-hello";
12020 static struct @{ char c; short s; int i; @}
12021 __attribute__ ((packed)) mixed
12022 = @{ 'c', 0x1234, 0x87654321 @};
12023 printf ("%s\n", hello);
12028 you get during debugging:
12031 (gdb) find &hello[0], +sizeof(hello), "hello"
12032 0x804956d <hello.1620+6>
12034 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12035 0x8049567 <hello.1620>
12036 0x804956d <hello.1620+6>
12038 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12039 0x8049567 <hello.1620>
12040 0x804956d <hello.1620+6>
12042 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12043 0x8049567 <hello.1620>
12045 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12046 0x8049560 <mixed.1625>
12048 (gdb) print $numfound
12051 $2 = (void *) 0x8049560
12055 @section Value Sizes
12057 Whenever @value{GDBN} prints a value memory will be allocated within
12058 @value{GDBN} to hold the contents of the value. It is possible in
12059 some languages with dynamic typing systems, that an invalid program
12060 may indicate a value that is incorrectly large, this in turn may cause
12061 @value{GDBN} to try and allocate an overly large ammount of memory.
12064 @kindex set max-value-size
12065 @item set max-value-size @var{bytes}
12066 @itemx set max-value-size unlimited
12067 Set the maximum size of memory that @value{GDBN} will allocate for the
12068 contents of a value to @var{bytes}, trying to display a value that
12069 requires more memory than that will result in an error.
12071 Setting this variable does not effect values that have already been
12072 allocated within @value{GDBN}, only future allocations.
12074 There's a minimum size that @code{max-value-size} can be set to in
12075 order that @value{GDBN} can still operate correctly, this minimum is
12076 currently 16 bytes.
12078 The limit applies to the results of some subexpressions as well as to
12079 complete expressions. For example, an expression denoting a simple
12080 integer component, such as @code{x.y.z}, may fail if the size of
12081 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12082 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12083 @var{A} is an array variable with non-constant size, will generally
12084 succeed regardless of the bounds on @var{A}, as long as the component
12085 size is less than @var{bytes}.
12087 The default value of @code{max-value-size} is currently 64k.
12089 @kindex show max-value-size
12090 @item show max-value-size
12091 Show the maximum size of memory, in bytes, that @value{GDBN} will
12092 allocate for the contents of a value.
12095 @node Optimized Code
12096 @chapter Debugging Optimized Code
12097 @cindex optimized code, debugging
12098 @cindex debugging optimized code
12100 Almost all compilers support optimization. With optimization
12101 disabled, the compiler generates assembly code that corresponds
12102 directly to your source code, in a simplistic way. As the compiler
12103 applies more powerful optimizations, the generated assembly code
12104 diverges from your original source code. With help from debugging
12105 information generated by the compiler, @value{GDBN} can map from
12106 the running program back to constructs from your original source.
12108 @value{GDBN} is more accurate with optimization disabled. If you
12109 can recompile without optimization, it is easier to follow the
12110 progress of your program during debugging. But, there are many cases
12111 where you may need to debug an optimized version.
12113 When you debug a program compiled with @samp{-g -O}, remember that the
12114 optimizer has rearranged your code; the debugger shows you what is
12115 really there. Do not be too surprised when the execution path does not
12116 exactly match your source file! An extreme example: if you define a
12117 variable, but never use it, @value{GDBN} never sees that
12118 variable---because the compiler optimizes it out of existence.
12120 Some things do not work as well with @samp{-g -O} as with just
12121 @samp{-g}, particularly on machines with instruction scheduling. If in
12122 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12123 please report it to us as a bug (including a test case!).
12124 @xref{Variables}, for more information about debugging optimized code.
12127 * Inline Functions:: How @value{GDBN} presents inlining
12128 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12131 @node Inline Functions
12132 @section Inline Functions
12133 @cindex inline functions, debugging
12135 @dfn{Inlining} is an optimization that inserts a copy of the function
12136 body directly at each call site, instead of jumping to a shared
12137 routine. @value{GDBN} displays inlined functions just like
12138 non-inlined functions. They appear in backtraces. You can view their
12139 arguments and local variables, step into them with @code{step}, skip
12140 them with @code{next}, and escape from them with @code{finish}.
12141 You can check whether a function was inlined by using the
12142 @code{info frame} command.
12144 For @value{GDBN} to support inlined functions, the compiler must
12145 record information about inlining in the debug information ---
12146 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12147 other compilers do also. @value{GDBN} only supports inlined functions
12148 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12149 do not emit two required attributes (@samp{DW_AT_call_file} and
12150 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12151 function calls with earlier versions of @value{NGCC}. It instead
12152 displays the arguments and local variables of inlined functions as
12153 local variables in the caller.
12155 The body of an inlined function is directly included at its call site;
12156 unlike a non-inlined function, there are no instructions devoted to
12157 the call. @value{GDBN} still pretends that the call site and the
12158 start of the inlined function are different instructions. Stepping to
12159 the call site shows the call site, and then stepping again shows
12160 the first line of the inlined function, even though no additional
12161 instructions are executed.
12163 This makes source-level debugging much clearer; you can see both the
12164 context of the call and then the effect of the call. Only stepping by
12165 a single instruction using @code{stepi} or @code{nexti} does not do
12166 this; single instruction steps always show the inlined body.
12168 There are some ways that @value{GDBN} does not pretend that inlined
12169 function calls are the same as normal calls:
12173 Setting breakpoints at the call site of an inlined function may not
12174 work, because the call site does not contain any code. @value{GDBN}
12175 may incorrectly move the breakpoint to the next line of the enclosing
12176 function, after the call. This limitation will be removed in a future
12177 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12178 or inside the inlined function instead.
12181 @value{GDBN} cannot locate the return value of inlined calls after
12182 using the @code{finish} command. This is a limitation of compiler-generated
12183 debugging information; after @code{finish}, you can step to the next line
12184 and print a variable where your program stored the return value.
12188 @node Tail Call Frames
12189 @section Tail Call Frames
12190 @cindex tail call frames, debugging
12192 Function @code{B} can call function @code{C} in its very last statement. In
12193 unoptimized compilation the call of @code{C} is immediately followed by return
12194 instruction at the end of @code{B} code. Optimizing compiler may replace the
12195 call and return in function @code{B} into one jump to function @code{C}
12196 instead. Such use of a jump instruction is called @dfn{tail call}.
12198 During execution of function @code{C}, there will be no indication in the
12199 function call stack frames that it was tail-called from @code{B}. If function
12200 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12201 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12202 some cases @value{GDBN} can determine that @code{C} was tail-called from
12203 @code{B}, and it will then create fictitious call frame for that, with the
12204 return address set up as if @code{B} called @code{C} normally.
12206 This functionality is currently supported only by DWARF 2 debugging format and
12207 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12208 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12211 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12212 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12216 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12218 Stack level 1, frame at 0x7fffffffda30:
12219 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12220 tail call frame, caller of frame at 0x7fffffffda30
12221 source language c++.
12222 Arglist at unknown address.
12223 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12226 The detection of all the possible code path executions can find them ambiguous.
12227 There is no execution history stored (possible @ref{Reverse Execution} is never
12228 used for this purpose) and the last known caller could have reached the known
12229 callee by multiple different jump sequences. In such case @value{GDBN} still
12230 tries to show at least all the unambiguous top tail callers and all the
12231 unambiguous bottom tail calees, if any.
12234 @anchor{set debug entry-values}
12235 @item set debug entry-values
12236 @kindex set debug entry-values
12237 When set to on, enables printing of analysis messages for both frame argument
12238 values at function entry and tail calls. It will show all the possible valid
12239 tail calls code paths it has considered. It will also print the intersection
12240 of them with the final unambiguous (possibly partial or even empty) code path
12243 @item show debug entry-values
12244 @kindex show debug entry-values
12245 Show the current state of analysis messages printing for both frame argument
12246 values at function entry and tail calls.
12249 The analysis messages for tail calls can for example show why the virtual tail
12250 call frame for function @code{c} has not been recognized (due to the indirect
12251 reference by variable @code{x}):
12254 static void __attribute__((noinline, noclone)) c (void);
12255 void (*x) (void) = c;
12256 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12257 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12258 int main (void) @{ x (); return 0; @}
12260 Breakpoint 1, DW_OP_entry_value resolving cannot find
12261 DW_TAG_call_site 0x40039a in main
12263 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12266 #1 0x000000000040039a in main () at t.c:5
12269 Another possibility is an ambiguous virtual tail call frames resolution:
12273 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12274 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12275 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12276 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12277 static void __attribute__((noinline, noclone)) b (void)
12278 @{ if (i) c (); else e (); @}
12279 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12280 int main (void) @{ a (); return 0; @}
12282 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12283 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12284 tailcall: reduced: 0x4004d2(a) |
12287 #1 0x00000000004004d2 in a () at t.c:8
12288 #2 0x0000000000400395 in main () at t.c:9
12291 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12292 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12294 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12295 @ifset HAVE_MAKEINFO_CLICK
12296 @set ARROW @click{}
12297 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12298 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12300 @ifclear HAVE_MAKEINFO_CLICK
12302 @set CALLSEQ1B @value{CALLSEQ1A}
12303 @set CALLSEQ2B @value{CALLSEQ2A}
12306 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12307 The code can have possible execution paths @value{CALLSEQ1B} or
12308 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12310 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12311 has found. It then finds another possible calling sequcen - that one is
12312 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12313 printed as the @code{reduced:} calling sequence. That one could have many
12314 futher @code{compare:} and @code{reduced:} statements as long as there remain
12315 any non-ambiguous sequence entries.
12317 For the frame of function @code{b} in both cases there are different possible
12318 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12319 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12320 therefore this one is displayed to the user while the ambiguous frames are
12323 There can be also reasons why printing of frame argument values at function
12328 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12329 static void __attribute__((noinline, noclone)) a (int i);
12330 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12331 static void __attribute__((noinline, noclone)) a (int i)
12332 @{ if (i) b (i - 1); else c (0); @}
12333 int main (void) @{ a (5); return 0; @}
12336 #0 c (i=i@@entry=0) at t.c:2
12337 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12338 function "a" at 0x400420 can call itself via tail calls
12339 i=<optimized out>) at t.c:6
12340 #2 0x000000000040036e in main () at t.c:7
12343 @value{GDBN} cannot find out from the inferior state if and how many times did
12344 function @code{a} call itself (via function @code{b}) as these calls would be
12345 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12346 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12347 prints @code{<optimized out>} instead.
12350 @chapter C Preprocessor Macros
12352 Some languages, such as C and C@t{++}, provide a way to define and invoke
12353 ``preprocessor macros'' which expand into strings of tokens.
12354 @value{GDBN} can evaluate expressions containing macro invocations, show
12355 the result of macro expansion, and show a macro's definition, including
12356 where it was defined.
12358 You may need to compile your program specially to provide @value{GDBN}
12359 with information about preprocessor macros. Most compilers do not
12360 include macros in their debugging information, even when you compile
12361 with the @option{-g} flag. @xref{Compilation}.
12363 A program may define a macro at one point, remove that definition later,
12364 and then provide a different definition after that. Thus, at different
12365 points in the program, a macro may have different definitions, or have
12366 no definition at all. If there is a current stack frame, @value{GDBN}
12367 uses the macros in scope at that frame's source code line. Otherwise,
12368 @value{GDBN} uses the macros in scope at the current listing location;
12371 Whenever @value{GDBN} evaluates an expression, it always expands any
12372 macro invocations present in the expression. @value{GDBN} also provides
12373 the following commands for working with macros explicitly.
12377 @kindex macro expand
12378 @cindex macro expansion, showing the results of preprocessor
12379 @cindex preprocessor macro expansion, showing the results of
12380 @cindex expanding preprocessor macros
12381 @item macro expand @var{expression}
12382 @itemx macro exp @var{expression}
12383 Show the results of expanding all preprocessor macro invocations in
12384 @var{expression}. Since @value{GDBN} simply expands macros, but does
12385 not parse the result, @var{expression} need not be a valid expression;
12386 it can be any string of tokens.
12389 @item macro expand-once @var{expression}
12390 @itemx macro exp1 @var{expression}
12391 @cindex expand macro once
12392 @i{(This command is not yet implemented.)} Show the results of
12393 expanding those preprocessor macro invocations that appear explicitly in
12394 @var{expression}. Macro invocations appearing in that expansion are
12395 left unchanged. This command allows you to see the effect of a
12396 particular macro more clearly, without being confused by further
12397 expansions. Since @value{GDBN} simply expands macros, but does not
12398 parse the result, @var{expression} need not be a valid expression; it
12399 can be any string of tokens.
12402 @cindex macro definition, showing
12403 @cindex definition of a macro, showing
12404 @cindex macros, from debug info
12405 @item info macro [-a|-all] [--] @var{macro}
12406 Show the current definition or all definitions of the named @var{macro},
12407 and describe the source location or compiler command-line where that
12408 definition was established. The optional double dash is to signify the end of
12409 argument processing and the beginning of @var{macro} for non C-like macros where
12410 the macro may begin with a hyphen.
12412 @kindex info macros
12413 @item info macros @var{location}
12414 Show all macro definitions that are in effect at the location specified
12415 by @var{location}, and describe the source location or compiler
12416 command-line where those definitions were established.
12418 @kindex macro define
12419 @cindex user-defined macros
12420 @cindex defining macros interactively
12421 @cindex macros, user-defined
12422 @item macro define @var{macro} @var{replacement-list}
12423 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12424 Introduce a definition for a preprocessor macro named @var{macro},
12425 invocations of which are replaced by the tokens given in
12426 @var{replacement-list}. The first form of this command defines an
12427 ``object-like'' macro, which takes no arguments; the second form
12428 defines a ``function-like'' macro, which takes the arguments given in
12431 A definition introduced by this command is in scope in every
12432 expression evaluated in @value{GDBN}, until it is removed with the
12433 @code{macro undef} command, described below. The definition overrides
12434 all definitions for @var{macro} present in the program being debugged,
12435 as well as any previous user-supplied definition.
12437 @kindex macro undef
12438 @item macro undef @var{macro}
12439 Remove any user-supplied definition for the macro named @var{macro}.
12440 This command only affects definitions provided with the @code{macro
12441 define} command, described above; it cannot remove definitions present
12442 in the program being debugged.
12446 List all the macros defined using the @code{macro define} command.
12449 @cindex macros, example of debugging with
12450 Here is a transcript showing the above commands in action. First, we
12451 show our source files:
12456 #include "sample.h"
12459 #define ADD(x) (M + x)
12464 printf ("Hello, world!\n");
12466 printf ("We're so creative.\n");
12468 printf ("Goodbye, world!\n");
12475 Now, we compile the program using the @sc{gnu} C compiler,
12476 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12477 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12478 and @option{-gdwarf-4}; we recommend always choosing the most recent
12479 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12480 includes information about preprocessor macros in the debugging
12484 $ gcc -gdwarf-2 -g3 sample.c -o sample
12488 Now, we start @value{GDBN} on our sample program:
12492 GNU gdb 2002-05-06-cvs
12493 Copyright 2002 Free Software Foundation, Inc.
12494 GDB is free software, @dots{}
12498 We can expand macros and examine their definitions, even when the
12499 program is not running. @value{GDBN} uses the current listing position
12500 to decide which macro definitions are in scope:
12503 (@value{GDBP}) list main
12506 5 #define ADD(x) (M + x)
12511 10 printf ("Hello, world!\n");
12513 12 printf ("We're so creative.\n");
12514 (@value{GDBP}) info macro ADD
12515 Defined at /home/jimb/gdb/macros/play/sample.c:5
12516 #define ADD(x) (M + x)
12517 (@value{GDBP}) info macro Q
12518 Defined at /home/jimb/gdb/macros/play/sample.h:1
12519 included at /home/jimb/gdb/macros/play/sample.c:2
12521 (@value{GDBP}) macro expand ADD(1)
12522 expands to: (42 + 1)
12523 (@value{GDBP}) macro expand-once ADD(1)
12524 expands to: once (M + 1)
12528 In the example above, note that @code{macro expand-once} expands only
12529 the macro invocation explicit in the original text --- the invocation of
12530 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12531 which was introduced by @code{ADD}.
12533 Once the program is running, @value{GDBN} uses the macro definitions in
12534 force at the source line of the current stack frame:
12537 (@value{GDBP}) break main
12538 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12540 Starting program: /home/jimb/gdb/macros/play/sample
12542 Breakpoint 1, main () at sample.c:10
12543 10 printf ("Hello, world!\n");
12547 At line 10, the definition of the macro @code{N} at line 9 is in force:
12550 (@value{GDBP}) info macro N
12551 Defined at /home/jimb/gdb/macros/play/sample.c:9
12553 (@value{GDBP}) macro expand N Q M
12554 expands to: 28 < 42
12555 (@value{GDBP}) print N Q M
12560 As we step over directives that remove @code{N}'s definition, and then
12561 give it a new definition, @value{GDBN} finds the definition (or lack
12562 thereof) in force at each point:
12565 (@value{GDBP}) next
12567 12 printf ("We're so creative.\n");
12568 (@value{GDBP}) info macro N
12569 The symbol `N' has no definition as a C/C++ preprocessor macro
12570 at /home/jimb/gdb/macros/play/sample.c:12
12571 (@value{GDBP}) next
12573 14 printf ("Goodbye, world!\n");
12574 (@value{GDBP}) info macro N
12575 Defined at /home/jimb/gdb/macros/play/sample.c:13
12577 (@value{GDBP}) macro expand N Q M
12578 expands to: 1729 < 42
12579 (@value{GDBP}) print N Q M
12584 In addition to source files, macros can be defined on the compilation command
12585 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12586 such a way, @value{GDBN} displays the location of their definition as line zero
12587 of the source file submitted to the compiler.
12590 (@value{GDBP}) info macro __STDC__
12591 Defined at /home/jimb/gdb/macros/play/sample.c:0
12598 @chapter Tracepoints
12599 @c This chapter is based on the documentation written by Michael
12600 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12602 @cindex tracepoints
12603 In some applications, it is not feasible for the debugger to interrupt
12604 the program's execution long enough for the developer to learn
12605 anything helpful about its behavior. If the program's correctness
12606 depends on its real-time behavior, delays introduced by a debugger
12607 might cause the program to change its behavior drastically, or perhaps
12608 fail, even when the code itself is correct. It is useful to be able
12609 to observe the program's behavior without interrupting it.
12611 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12612 specify locations in the program, called @dfn{tracepoints}, and
12613 arbitrary expressions to evaluate when those tracepoints are reached.
12614 Later, using the @code{tfind} command, you can examine the values
12615 those expressions had when the program hit the tracepoints. The
12616 expressions may also denote objects in memory---structures or arrays,
12617 for example---whose values @value{GDBN} should record; while visiting
12618 a particular tracepoint, you may inspect those objects as if they were
12619 in memory at that moment. However, because @value{GDBN} records these
12620 values without interacting with you, it can do so quickly and
12621 unobtrusively, hopefully not disturbing the program's behavior.
12623 The tracepoint facility is currently available only for remote
12624 targets. @xref{Targets}. In addition, your remote target must know
12625 how to collect trace data. This functionality is implemented in the
12626 remote stub; however, none of the stubs distributed with @value{GDBN}
12627 support tracepoints as of this writing. The format of the remote
12628 packets used to implement tracepoints are described in @ref{Tracepoint
12631 It is also possible to get trace data from a file, in a manner reminiscent
12632 of corefiles; you specify the filename, and use @code{tfind} to search
12633 through the file. @xref{Trace Files}, for more details.
12635 This chapter describes the tracepoint commands and features.
12638 * Set Tracepoints::
12639 * Analyze Collected Data::
12640 * Tracepoint Variables::
12644 @node Set Tracepoints
12645 @section Commands to Set Tracepoints
12647 Before running such a @dfn{trace experiment}, an arbitrary number of
12648 tracepoints can be set. A tracepoint is actually a special type of
12649 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12650 standard breakpoint commands. For instance, as with breakpoints,
12651 tracepoint numbers are successive integers starting from one, and many
12652 of the commands associated with tracepoints take the tracepoint number
12653 as their argument, to identify which tracepoint to work on.
12655 For each tracepoint, you can specify, in advance, some arbitrary set
12656 of data that you want the target to collect in the trace buffer when
12657 it hits that tracepoint. The collected data can include registers,
12658 local variables, or global data. Later, you can use @value{GDBN}
12659 commands to examine the values these data had at the time the
12660 tracepoint was hit.
12662 Tracepoints do not support every breakpoint feature. Ignore counts on
12663 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12664 commands when they are hit. Tracepoints may not be thread-specific
12667 @cindex fast tracepoints
12668 Some targets may support @dfn{fast tracepoints}, which are inserted in
12669 a different way (such as with a jump instead of a trap), that is
12670 faster but possibly restricted in where they may be installed.
12672 @cindex static tracepoints
12673 @cindex markers, static tracepoints
12674 @cindex probing markers, static tracepoints
12675 Regular and fast tracepoints are dynamic tracing facilities, meaning
12676 that they can be used to insert tracepoints at (almost) any location
12677 in the target. Some targets may also support controlling @dfn{static
12678 tracepoints} from @value{GDBN}. With static tracing, a set of
12679 instrumentation points, also known as @dfn{markers}, are embedded in
12680 the target program, and can be activated or deactivated by name or
12681 address. These are usually placed at locations which facilitate
12682 investigating what the target is actually doing. @value{GDBN}'s
12683 support for static tracing includes being able to list instrumentation
12684 points, and attach them with @value{GDBN} defined high level
12685 tracepoints that expose the whole range of convenience of
12686 @value{GDBN}'s tracepoints support. Namely, support for collecting
12687 registers values and values of global or local (to the instrumentation
12688 point) variables; tracepoint conditions and trace state variables.
12689 The act of installing a @value{GDBN} static tracepoint on an
12690 instrumentation point, or marker, is referred to as @dfn{probing} a
12691 static tracepoint marker.
12693 @code{gdbserver} supports tracepoints on some target systems.
12694 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12696 This section describes commands to set tracepoints and associated
12697 conditions and actions.
12700 * Create and Delete Tracepoints::
12701 * Enable and Disable Tracepoints::
12702 * Tracepoint Passcounts::
12703 * Tracepoint Conditions::
12704 * Trace State Variables::
12705 * Tracepoint Actions::
12706 * Listing Tracepoints::
12707 * Listing Static Tracepoint Markers::
12708 * Starting and Stopping Trace Experiments::
12709 * Tracepoint Restrictions::
12712 @node Create and Delete Tracepoints
12713 @subsection Create and Delete Tracepoints
12716 @cindex set tracepoint
12718 @item trace @var{location}
12719 The @code{trace} command is very similar to the @code{break} command.
12720 Its argument @var{location} can be any valid location.
12721 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12722 which is a point in the target program where the debugger will briefly stop,
12723 collect some data, and then allow the program to continue. Setting a tracepoint
12724 or changing its actions takes effect immediately if the remote stub
12725 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12727 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12728 these changes don't take effect until the next @code{tstart}
12729 command, and once a trace experiment is running, further changes will
12730 not have any effect until the next trace experiment starts. In addition,
12731 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12732 address is not yet resolved. (This is similar to pending breakpoints.)
12733 Pending tracepoints are not downloaded to the target and not installed
12734 until they are resolved. The resolution of pending tracepoints requires
12735 @value{GDBN} support---when debugging with the remote target, and
12736 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12737 tracing}), pending tracepoints can not be resolved (and downloaded to
12738 the remote stub) while @value{GDBN} is disconnected.
12740 Here are some examples of using the @code{trace} command:
12743 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12745 (@value{GDBP}) @b{trace +2} // 2 lines forward
12747 (@value{GDBP}) @b{trace my_function} // first source line of function
12749 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12751 (@value{GDBP}) @b{trace *0x2117c4} // an address
12755 You can abbreviate @code{trace} as @code{tr}.
12757 @item trace @var{location} if @var{cond}
12758 Set a tracepoint with condition @var{cond}; evaluate the expression
12759 @var{cond} each time the tracepoint is reached, and collect data only
12760 if the value is nonzero---that is, if @var{cond} evaluates as true.
12761 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12762 information on tracepoint conditions.
12764 @item ftrace @var{location} [ if @var{cond} ]
12765 @cindex set fast tracepoint
12766 @cindex fast tracepoints, setting
12768 The @code{ftrace} command sets a fast tracepoint. For targets that
12769 support them, fast tracepoints will use a more efficient but possibly
12770 less general technique to trigger data collection, such as a jump
12771 instruction instead of a trap, or some sort of hardware support. It
12772 may not be possible to create a fast tracepoint at the desired
12773 location, in which case the command will exit with an explanatory
12776 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12779 On 32-bit x86-architecture systems, fast tracepoints normally need to
12780 be placed at an instruction that is 5 bytes or longer, but can be
12781 placed at 4-byte instructions if the low 64K of memory of the target
12782 program is available to install trampolines. Some Unix-type systems,
12783 such as @sc{gnu}/Linux, exclude low addresses from the program's
12784 address space; but for instance with the Linux kernel it is possible
12785 to let @value{GDBN} use this area by doing a @command{sysctl} command
12786 to set the @code{mmap_min_addr} kernel parameter, as in
12789 sudo sysctl -w vm.mmap_min_addr=32768
12793 which sets the low address to 32K, which leaves plenty of room for
12794 trampolines. The minimum address should be set to a page boundary.
12796 @item strace @var{location} [ if @var{cond} ]
12797 @cindex set static tracepoint
12798 @cindex static tracepoints, setting
12799 @cindex probe static tracepoint marker
12801 The @code{strace} command sets a static tracepoint. For targets that
12802 support it, setting a static tracepoint probes a static
12803 instrumentation point, or marker, found at @var{location}. It may not
12804 be possible to set a static tracepoint at the desired location, in
12805 which case the command will exit with an explanatory message.
12807 @value{GDBN} handles arguments to @code{strace} exactly as for
12808 @code{trace}, with the addition that the user can also specify
12809 @code{-m @var{marker}} as @var{location}. This probes the marker
12810 identified by the @var{marker} string identifier. This identifier
12811 depends on the static tracepoint backend library your program is
12812 using. You can find all the marker identifiers in the @samp{ID} field
12813 of the @code{info static-tracepoint-markers} command output.
12814 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12815 Markers}. For example, in the following small program using the UST
12821 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12826 the marker id is composed of joining the first two arguments to the
12827 @code{trace_mark} call with a slash, which translates to:
12830 (@value{GDBP}) info static-tracepoint-markers
12831 Cnt Enb ID Address What
12832 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12838 so you may probe the marker above with:
12841 (@value{GDBP}) strace -m ust/bar33
12844 Static tracepoints accept an extra collect action --- @code{collect
12845 $_sdata}. This collects arbitrary user data passed in the probe point
12846 call to the tracing library. In the UST example above, you'll see
12847 that the third argument to @code{trace_mark} is a printf-like format
12848 string. The user data is then the result of running that formating
12849 string against the following arguments. Note that @code{info
12850 static-tracepoint-markers} command output lists that format string in
12851 the @samp{Data:} field.
12853 You can inspect this data when analyzing the trace buffer, by printing
12854 the $_sdata variable like any other variable available to
12855 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12858 @cindex last tracepoint number
12859 @cindex recent tracepoint number
12860 @cindex tracepoint number
12861 The convenience variable @code{$tpnum} records the tracepoint number
12862 of the most recently set tracepoint.
12864 @kindex delete tracepoint
12865 @cindex tracepoint deletion
12866 @item delete tracepoint @r{[}@var{num}@r{]}
12867 Permanently delete one or more tracepoints. With no argument, the
12868 default is to delete all tracepoints. Note that the regular
12869 @code{delete} command can remove tracepoints also.
12874 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12876 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12880 You can abbreviate this command as @code{del tr}.
12883 @node Enable and Disable Tracepoints
12884 @subsection Enable and Disable Tracepoints
12886 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12889 @kindex disable tracepoint
12890 @item disable tracepoint @r{[}@var{num}@r{]}
12891 Disable tracepoint @var{num}, or all tracepoints if no argument
12892 @var{num} is given. A disabled tracepoint will have no effect during
12893 a trace experiment, but it is not forgotten. You can re-enable
12894 a disabled tracepoint using the @code{enable tracepoint} command.
12895 If the command is issued during a trace experiment and the debug target
12896 has support for disabling tracepoints during a trace experiment, then the
12897 change will be effective immediately. Otherwise, it will be applied to the
12898 next trace experiment.
12900 @kindex enable tracepoint
12901 @item enable tracepoint @r{[}@var{num}@r{]}
12902 Enable tracepoint @var{num}, or all tracepoints. If this command is
12903 issued during a trace experiment and the debug target supports enabling
12904 tracepoints during a trace experiment, then the enabled tracepoints will
12905 become effective immediately. Otherwise, they will become effective the
12906 next time a trace experiment is run.
12909 @node Tracepoint Passcounts
12910 @subsection Tracepoint Passcounts
12914 @cindex tracepoint pass count
12915 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12916 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12917 automatically stop a trace experiment. If a tracepoint's passcount is
12918 @var{n}, then the trace experiment will be automatically stopped on
12919 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12920 @var{num} is not specified, the @code{passcount} command sets the
12921 passcount of the most recently defined tracepoint. If no passcount is
12922 given, the trace experiment will run until stopped explicitly by the
12928 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12929 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12931 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12932 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12933 (@value{GDBP}) @b{trace foo}
12934 (@value{GDBP}) @b{pass 3}
12935 (@value{GDBP}) @b{trace bar}
12936 (@value{GDBP}) @b{pass 2}
12937 (@value{GDBP}) @b{trace baz}
12938 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12939 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12940 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12941 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12945 @node Tracepoint Conditions
12946 @subsection Tracepoint Conditions
12947 @cindex conditional tracepoints
12948 @cindex tracepoint conditions
12950 The simplest sort of tracepoint collects data every time your program
12951 reaches a specified place. You can also specify a @dfn{condition} for
12952 a tracepoint. A condition is just a Boolean expression in your
12953 programming language (@pxref{Expressions, ,Expressions}). A
12954 tracepoint with a condition evaluates the expression each time your
12955 program reaches it, and data collection happens only if the condition
12958 Tracepoint conditions can be specified when a tracepoint is set, by
12959 using @samp{if} in the arguments to the @code{trace} command.
12960 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12961 also be set or changed at any time with the @code{condition} command,
12962 just as with breakpoints.
12964 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12965 the conditional expression itself. Instead, @value{GDBN} encodes the
12966 expression into an agent expression (@pxref{Agent Expressions})
12967 suitable for execution on the target, independently of @value{GDBN}.
12968 Global variables become raw memory locations, locals become stack
12969 accesses, and so forth.
12971 For instance, suppose you have a function that is usually called
12972 frequently, but should not be called after an error has occurred. You
12973 could use the following tracepoint command to collect data about calls
12974 of that function that happen while the error code is propagating
12975 through the program; an unconditional tracepoint could end up
12976 collecting thousands of useless trace frames that you would have to
12980 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12983 @node Trace State Variables
12984 @subsection Trace State Variables
12985 @cindex trace state variables
12987 A @dfn{trace state variable} is a special type of variable that is
12988 created and managed by target-side code. The syntax is the same as
12989 that for GDB's convenience variables (a string prefixed with ``$''),
12990 but they are stored on the target. They must be created explicitly,
12991 using a @code{tvariable} command. They are always 64-bit signed
12994 Trace state variables are remembered by @value{GDBN}, and downloaded
12995 to the target along with tracepoint information when the trace
12996 experiment starts. There are no intrinsic limits on the number of
12997 trace state variables, beyond memory limitations of the target.
12999 @cindex convenience variables, and trace state variables
13000 Although trace state variables are managed by the target, you can use
13001 them in print commands and expressions as if they were convenience
13002 variables; @value{GDBN} will get the current value from the target
13003 while the trace experiment is running. Trace state variables share
13004 the same namespace as other ``$'' variables, which means that you
13005 cannot have trace state variables with names like @code{$23} or
13006 @code{$pc}, nor can you have a trace state variable and a convenience
13007 variable with the same name.
13011 @item tvariable $@var{name} [ = @var{expression} ]
13013 The @code{tvariable} command creates a new trace state variable named
13014 @code{$@var{name}}, and optionally gives it an initial value of
13015 @var{expression}. The @var{expression} is evaluated when this command is
13016 entered; the result will be converted to an integer if possible,
13017 otherwise @value{GDBN} will report an error. A subsequent
13018 @code{tvariable} command specifying the same name does not create a
13019 variable, but instead assigns the supplied initial value to the
13020 existing variable of that name, overwriting any previous initial
13021 value. The default initial value is 0.
13023 @item info tvariables
13024 @kindex info tvariables
13025 List all the trace state variables along with their initial values.
13026 Their current values may also be displayed, if the trace experiment is
13029 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13030 @kindex delete tvariable
13031 Delete the given trace state variables, or all of them if no arguments
13036 @node Tracepoint Actions
13037 @subsection Tracepoint Action Lists
13041 @cindex tracepoint actions
13042 @item actions @r{[}@var{num}@r{]}
13043 This command will prompt for a list of actions to be taken when the
13044 tracepoint is hit. If the tracepoint number @var{num} is not
13045 specified, this command sets the actions for the one that was most
13046 recently defined (so that you can define a tracepoint and then say
13047 @code{actions} without bothering about its number). You specify the
13048 actions themselves on the following lines, one action at a time, and
13049 terminate the actions list with a line containing just @code{end}. So
13050 far, the only defined actions are @code{collect}, @code{teval}, and
13051 @code{while-stepping}.
13053 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13054 Commands, ,Breakpoint Command Lists}), except that only the defined
13055 actions are allowed; any other @value{GDBN} command is rejected.
13057 @cindex remove actions from a tracepoint
13058 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13059 and follow it immediately with @samp{end}.
13062 (@value{GDBP}) @b{collect @var{data}} // collect some data
13064 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13066 (@value{GDBP}) @b{end} // signals the end of actions.
13069 In the following example, the action list begins with @code{collect}
13070 commands indicating the things to be collected when the tracepoint is
13071 hit. Then, in order to single-step and collect additional data
13072 following the tracepoint, a @code{while-stepping} command is used,
13073 followed by the list of things to be collected after each step in a
13074 sequence of single steps. The @code{while-stepping} command is
13075 terminated by its own separate @code{end} command. Lastly, the action
13076 list is terminated by an @code{end} command.
13079 (@value{GDBP}) @b{trace foo}
13080 (@value{GDBP}) @b{actions}
13081 Enter actions for tracepoint 1, one per line:
13084 > while-stepping 12
13085 > collect $pc, arr[i]
13090 @kindex collect @r{(tracepoints)}
13091 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13092 Collect values of the given expressions when the tracepoint is hit.
13093 This command accepts a comma-separated list of any valid expressions.
13094 In addition to global, static, or local variables, the following
13095 special arguments are supported:
13099 Collect all registers.
13102 Collect all function arguments.
13105 Collect all local variables.
13108 Collect the return address. This is helpful if you want to see more
13111 @emph{Note:} The return address location can not always be reliably
13112 determined up front, and the wrong address / registers may end up
13113 collected instead. On some architectures the reliability is higher
13114 for tracepoints at function entry, while on others it's the opposite.
13115 When this happens, backtracing will stop because the return address is
13116 found unavailable (unless another collect rule happened to match it).
13119 Collects the number of arguments from the static probe at which the
13120 tracepoint is located.
13121 @xref{Static Probe Points}.
13123 @item $_probe_arg@var{n}
13124 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13125 from the static probe at which the tracepoint is located.
13126 @xref{Static Probe Points}.
13129 @vindex $_sdata@r{, collect}
13130 Collect static tracepoint marker specific data. Only available for
13131 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13132 Lists}. On the UST static tracepoints library backend, an
13133 instrumentation point resembles a @code{printf} function call. The
13134 tracing library is able to collect user specified data formatted to a
13135 character string using the format provided by the programmer that
13136 instrumented the program. Other backends have similar mechanisms.
13137 Here's an example of a UST marker call:
13140 const char master_name[] = "$your_name";
13141 trace_mark(channel1, marker1, "hello %s", master_name)
13144 In this case, collecting @code{$_sdata} collects the string
13145 @samp{hello $yourname}. When analyzing the trace buffer, you can
13146 inspect @samp{$_sdata} like any other variable available to
13150 You can give several consecutive @code{collect} commands, each one
13151 with a single argument, or one @code{collect} command with several
13152 arguments separated by commas; the effect is the same.
13154 The optional @var{mods} changes the usual handling of the arguments.
13155 @code{s} requests that pointers to chars be handled as strings, in
13156 particular collecting the contents of the memory being pointed at, up
13157 to the first zero. The upper bound is by default the value of the
13158 @code{print elements} variable; if @code{s} is followed by a decimal
13159 number, that is the upper bound instead. So for instance
13160 @samp{collect/s25 mystr} collects as many as 25 characters at
13163 The command @code{info scope} (@pxref{Symbols, info scope}) is
13164 particularly useful for figuring out what data to collect.
13166 @kindex teval @r{(tracepoints)}
13167 @item teval @var{expr1}, @var{expr2}, @dots{}
13168 Evaluate the given expressions when the tracepoint is hit. This
13169 command accepts a comma-separated list of expressions. The results
13170 are discarded, so this is mainly useful for assigning values to trace
13171 state variables (@pxref{Trace State Variables}) without adding those
13172 values to the trace buffer, as would be the case if the @code{collect}
13175 @kindex while-stepping @r{(tracepoints)}
13176 @item while-stepping @var{n}
13177 Perform @var{n} single-step instruction traces after the tracepoint,
13178 collecting new data after each step. The @code{while-stepping}
13179 command is followed by the list of what to collect while stepping
13180 (followed by its own @code{end} command):
13183 > while-stepping 12
13184 > collect $regs, myglobal
13190 Note that @code{$pc} is not automatically collected by
13191 @code{while-stepping}; you need to explicitly collect that register if
13192 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13195 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13196 @kindex set default-collect
13197 @cindex default collection action
13198 This variable is a list of expressions to collect at each tracepoint
13199 hit. It is effectively an additional @code{collect} action prepended
13200 to every tracepoint action list. The expressions are parsed
13201 individually for each tracepoint, so for instance a variable named
13202 @code{xyz} may be interpreted as a global for one tracepoint, and a
13203 local for another, as appropriate to the tracepoint's location.
13205 @item show default-collect
13206 @kindex show default-collect
13207 Show the list of expressions that are collected by default at each
13212 @node Listing Tracepoints
13213 @subsection Listing Tracepoints
13216 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13217 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13218 @cindex information about tracepoints
13219 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13220 Display information about the tracepoint @var{num}. If you don't
13221 specify a tracepoint number, displays information about all the
13222 tracepoints defined so far. The format is similar to that used for
13223 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13224 command, simply restricting itself to tracepoints.
13226 A tracepoint's listing may include additional information specific to
13231 its passcount as given by the @code{passcount @var{n}} command
13234 the state about installed on target of each location
13238 (@value{GDBP}) @b{info trace}
13239 Num Type Disp Enb Address What
13240 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13242 collect globfoo, $regs
13247 2 tracepoint keep y <MULTIPLE>
13249 2.1 y 0x0804859c in func4 at change-loc.h:35
13250 installed on target
13251 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13252 installed on target
13253 2.3 y <PENDING> set_tracepoint
13254 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13255 not installed on target
13260 This command can be abbreviated @code{info tp}.
13263 @node Listing Static Tracepoint Markers
13264 @subsection Listing Static Tracepoint Markers
13267 @kindex info static-tracepoint-markers
13268 @cindex information about static tracepoint markers
13269 @item info static-tracepoint-markers
13270 Display information about all static tracepoint markers defined in the
13273 For each marker, the following columns are printed:
13277 An incrementing counter, output to help readability. This is not a
13280 The marker ID, as reported by the target.
13281 @item Enabled or Disabled
13282 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13283 that are not enabled.
13285 Where the marker is in your program, as a memory address.
13287 Where the marker is in the source for your program, as a file and line
13288 number. If the debug information included in the program does not
13289 allow @value{GDBN} to locate the source of the marker, this column
13290 will be left blank.
13294 In addition, the following information may be printed for each marker:
13298 User data passed to the tracing library by the marker call. In the
13299 UST backend, this is the format string passed as argument to the
13301 @item Static tracepoints probing the marker
13302 The list of static tracepoints attached to the marker.
13306 (@value{GDBP}) info static-tracepoint-markers
13307 Cnt ID Enb Address What
13308 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13309 Data: number1 %d number2 %d
13310 Probed by static tracepoints: #2
13311 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13317 @node Starting and Stopping Trace Experiments
13318 @subsection Starting and Stopping Trace Experiments
13321 @kindex tstart [ @var{notes} ]
13322 @cindex start a new trace experiment
13323 @cindex collected data discarded
13325 This command starts the trace experiment, and begins collecting data.
13326 It has the side effect of discarding all the data collected in the
13327 trace buffer during the previous trace experiment. If any arguments
13328 are supplied, they are taken as a note and stored with the trace
13329 experiment's state. The notes may be arbitrary text, and are
13330 especially useful with disconnected tracing in a multi-user context;
13331 the notes can explain what the trace is doing, supply user contact
13332 information, and so forth.
13334 @kindex tstop [ @var{notes} ]
13335 @cindex stop a running trace experiment
13337 This command stops the trace experiment. If any arguments are
13338 supplied, they are recorded with the experiment as a note. This is
13339 useful if you are stopping a trace started by someone else, for
13340 instance if the trace is interfering with the system's behavior and
13341 needs to be stopped quickly.
13343 @strong{Note}: a trace experiment and data collection may stop
13344 automatically if any tracepoint's passcount is reached
13345 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13348 @cindex status of trace data collection
13349 @cindex trace experiment, status of
13351 This command displays the status of the current trace data
13355 Here is an example of the commands we described so far:
13358 (@value{GDBP}) @b{trace gdb_c_test}
13359 (@value{GDBP}) @b{actions}
13360 Enter actions for tracepoint #1, one per line.
13361 > collect $regs,$locals,$args
13362 > while-stepping 11
13366 (@value{GDBP}) @b{tstart}
13367 [time passes @dots{}]
13368 (@value{GDBP}) @b{tstop}
13371 @anchor{disconnected tracing}
13372 @cindex disconnected tracing
13373 You can choose to continue running the trace experiment even if
13374 @value{GDBN} disconnects from the target, voluntarily or
13375 involuntarily. For commands such as @code{detach}, the debugger will
13376 ask what you want to do with the trace. But for unexpected
13377 terminations (@value{GDBN} crash, network outage), it would be
13378 unfortunate to lose hard-won trace data, so the variable
13379 @code{disconnected-tracing} lets you decide whether the trace should
13380 continue running without @value{GDBN}.
13383 @item set disconnected-tracing on
13384 @itemx set disconnected-tracing off
13385 @kindex set disconnected-tracing
13386 Choose whether a tracing run should continue to run if @value{GDBN}
13387 has disconnected from the target. Note that @code{detach} or
13388 @code{quit} will ask you directly what to do about a running trace no
13389 matter what this variable's setting, so the variable is mainly useful
13390 for handling unexpected situations, such as loss of the network.
13392 @item show disconnected-tracing
13393 @kindex show disconnected-tracing
13394 Show the current choice for disconnected tracing.
13398 When you reconnect to the target, the trace experiment may or may not
13399 still be running; it might have filled the trace buffer in the
13400 meantime, or stopped for one of the other reasons. If it is running,
13401 it will continue after reconnection.
13403 Upon reconnection, the target will upload information about the
13404 tracepoints in effect. @value{GDBN} will then compare that
13405 information to the set of tracepoints currently defined, and attempt
13406 to match them up, allowing for the possibility that the numbers may
13407 have changed due to creation and deletion in the meantime. If one of
13408 the target's tracepoints does not match any in @value{GDBN}, the
13409 debugger will create a new tracepoint, so that you have a number with
13410 which to specify that tracepoint. This matching-up process is
13411 necessarily heuristic, and it may result in useless tracepoints being
13412 created; you may simply delete them if they are of no use.
13414 @cindex circular trace buffer
13415 If your target agent supports a @dfn{circular trace buffer}, then you
13416 can run a trace experiment indefinitely without filling the trace
13417 buffer; when space runs out, the agent deletes already-collected trace
13418 frames, oldest first, until there is enough room to continue
13419 collecting. This is especially useful if your tracepoints are being
13420 hit too often, and your trace gets terminated prematurely because the
13421 buffer is full. To ask for a circular trace buffer, simply set
13422 @samp{circular-trace-buffer} to on. You can set this at any time,
13423 including during tracing; if the agent can do it, it will change
13424 buffer handling on the fly, otherwise it will not take effect until
13428 @item set circular-trace-buffer on
13429 @itemx set circular-trace-buffer off
13430 @kindex set circular-trace-buffer
13431 Choose whether a tracing run should use a linear or circular buffer
13432 for trace data. A linear buffer will not lose any trace data, but may
13433 fill up prematurely, while a circular buffer will discard old trace
13434 data, but it will have always room for the latest tracepoint hits.
13436 @item show circular-trace-buffer
13437 @kindex show circular-trace-buffer
13438 Show the current choice for the trace buffer. Note that this may not
13439 match the agent's current buffer handling, nor is it guaranteed to
13440 match the setting that might have been in effect during a past run,
13441 for instance if you are looking at frames from a trace file.
13446 @item set trace-buffer-size @var{n}
13447 @itemx set trace-buffer-size unlimited
13448 @kindex set trace-buffer-size
13449 Request that the target use a trace buffer of @var{n} bytes. Not all
13450 targets will honor the request; they may have a compiled-in size for
13451 the trace buffer, or some other limitation. Set to a value of
13452 @code{unlimited} or @code{-1} to let the target use whatever size it
13453 likes. This is also the default.
13455 @item show trace-buffer-size
13456 @kindex show trace-buffer-size
13457 Show the current requested size for the trace buffer. Note that this
13458 will only match the actual size if the target supports size-setting,
13459 and was able to handle the requested size. For instance, if the
13460 target can only change buffer size between runs, this variable will
13461 not reflect the change until the next run starts. Use @code{tstatus}
13462 to get a report of the actual buffer size.
13466 @item set trace-user @var{text}
13467 @kindex set trace-user
13469 @item show trace-user
13470 @kindex show trace-user
13472 @item set trace-notes @var{text}
13473 @kindex set trace-notes
13474 Set the trace run's notes.
13476 @item show trace-notes
13477 @kindex show trace-notes
13478 Show the trace run's notes.
13480 @item set trace-stop-notes @var{text}
13481 @kindex set trace-stop-notes
13482 Set the trace run's stop notes. The handling of the note is as for
13483 @code{tstop} arguments; the set command is convenient way to fix a
13484 stop note that is mistaken or incomplete.
13486 @item show trace-stop-notes
13487 @kindex show trace-stop-notes
13488 Show the trace run's stop notes.
13492 @node Tracepoint Restrictions
13493 @subsection Tracepoint Restrictions
13495 @cindex tracepoint restrictions
13496 There are a number of restrictions on the use of tracepoints. As
13497 described above, tracepoint data gathering occurs on the target
13498 without interaction from @value{GDBN}. Thus the full capabilities of
13499 the debugger are not available during data gathering, and then at data
13500 examination time, you will be limited by only having what was
13501 collected. The following items describe some common problems, but it
13502 is not exhaustive, and you may run into additional difficulties not
13508 Tracepoint expressions are intended to gather objects (lvalues). Thus
13509 the full flexibility of GDB's expression evaluator is not available.
13510 You cannot call functions, cast objects to aggregate types, access
13511 convenience variables or modify values (except by assignment to trace
13512 state variables). Some language features may implicitly call
13513 functions (for instance Objective-C fields with accessors), and therefore
13514 cannot be collected either.
13517 Collection of local variables, either individually or in bulk with
13518 @code{$locals} or @code{$args}, during @code{while-stepping} may
13519 behave erratically. The stepping action may enter a new scope (for
13520 instance by stepping into a function), or the location of the variable
13521 may change (for instance it is loaded into a register). The
13522 tracepoint data recorded uses the location information for the
13523 variables that is correct for the tracepoint location. When the
13524 tracepoint is created, it is not possible, in general, to determine
13525 where the steps of a @code{while-stepping} sequence will advance the
13526 program---particularly if a conditional branch is stepped.
13529 Collection of an incompletely-initialized or partially-destroyed object
13530 may result in something that @value{GDBN} cannot display, or displays
13531 in a misleading way.
13534 When @value{GDBN} displays a pointer to character it automatically
13535 dereferences the pointer to also display characters of the string
13536 being pointed to. However, collecting the pointer during tracing does
13537 not automatically collect the string. You need to explicitly
13538 dereference the pointer and provide size information if you want to
13539 collect not only the pointer, but the memory pointed to. For example,
13540 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13544 It is not possible to collect a complete stack backtrace at a
13545 tracepoint. Instead, you may collect the registers and a few hundred
13546 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13547 (adjust to use the name of the actual stack pointer register on your
13548 target architecture, and the amount of stack you wish to capture).
13549 Then the @code{backtrace} command will show a partial backtrace when
13550 using a trace frame. The number of stack frames that can be examined
13551 depends on the sizes of the frames in the collected stack. Note that
13552 if you ask for a block so large that it goes past the bottom of the
13553 stack, the target agent may report an error trying to read from an
13557 If you do not collect registers at a tracepoint, @value{GDBN} can
13558 infer that the value of @code{$pc} must be the same as the address of
13559 the tracepoint and use that when you are looking at a trace frame
13560 for that tracepoint. However, this cannot work if the tracepoint has
13561 multiple locations (for instance if it was set in a function that was
13562 inlined), or if it has a @code{while-stepping} loop. In those cases
13563 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13568 @node Analyze Collected Data
13569 @section Using the Collected Data
13571 After the tracepoint experiment ends, you use @value{GDBN} commands
13572 for examining the trace data. The basic idea is that each tracepoint
13573 collects a trace @dfn{snapshot} every time it is hit and another
13574 snapshot every time it single-steps. All these snapshots are
13575 consecutively numbered from zero and go into a buffer, and you can
13576 examine them later. The way you examine them is to @dfn{focus} on a
13577 specific trace snapshot. When the remote stub is focused on a trace
13578 snapshot, it will respond to all @value{GDBN} requests for memory and
13579 registers by reading from the buffer which belongs to that snapshot,
13580 rather than from @emph{real} memory or registers of the program being
13581 debugged. This means that @strong{all} @value{GDBN} commands
13582 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13583 behave as if we were currently debugging the program state as it was
13584 when the tracepoint occurred. Any requests for data that are not in
13585 the buffer will fail.
13588 * tfind:: How to select a trace snapshot
13589 * tdump:: How to display all data for a snapshot
13590 * save tracepoints:: How to save tracepoints for a future run
13594 @subsection @code{tfind @var{n}}
13597 @cindex select trace snapshot
13598 @cindex find trace snapshot
13599 The basic command for selecting a trace snapshot from the buffer is
13600 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13601 counting from zero. If no argument @var{n} is given, the next
13602 snapshot is selected.
13604 Here are the various forms of using the @code{tfind} command.
13608 Find the first snapshot in the buffer. This is a synonym for
13609 @code{tfind 0} (since 0 is the number of the first snapshot).
13612 Stop debugging trace snapshots, resume @emph{live} debugging.
13615 Same as @samp{tfind none}.
13618 No argument means find the next trace snapshot or find the first
13619 one if no trace snapshot is selected.
13622 Find the previous trace snapshot before the current one. This permits
13623 retracing earlier steps.
13625 @item tfind tracepoint @var{num}
13626 Find the next snapshot associated with tracepoint @var{num}. Search
13627 proceeds forward from the last examined trace snapshot. If no
13628 argument @var{num} is given, it means find the next snapshot collected
13629 for the same tracepoint as the current snapshot.
13631 @item tfind pc @var{addr}
13632 Find the next snapshot associated with the value @var{addr} of the
13633 program counter. Search proceeds forward from the last examined trace
13634 snapshot. If no argument @var{addr} is given, it means find the next
13635 snapshot with the same value of PC as the current snapshot.
13637 @item tfind outside @var{addr1}, @var{addr2}
13638 Find the next snapshot whose PC is outside the given range of
13639 addresses (exclusive).
13641 @item tfind range @var{addr1}, @var{addr2}
13642 Find the next snapshot whose PC is between @var{addr1} and
13643 @var{addr2} (inclusive).
13645 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13646 Find the next snapshot associated with the source line @var{n}. If
13647 the optional argument @var{file} is given, refer to line @var{n} in
13648 that source file. Search proceeds forward from the last examined
13649 trace snapshot. If no argument @var{n} is given, it means find the
13650 next line other than the one currently being examined; thus saying
13651 @code{tfind line} repeatedly can appear to have the same effect as
13652 stepping from line to line in a @emph{live} debugging session.
13655 The default arguments for the @code{tfind} commands are specifically
13656 designed to make it easy to scan through the trace buffer. For
13657 instance, @code{tfind} with no argument selects the next trace
13658 snapshot, and @code{tfind -} with no argument selects the previous
13659 trace snapshot. So, by giving one @code{tfind} command, and then
13660 simply hitting @key{RET} repeatedly you can examine all the trace
13661 snapshots in order. Or, by saying @code{tfind -} and then hitting
13662 @key{RET} repeatedly you can examine the snapshots in reverse order.
13663 The @code{tfind line} command with no argument selects the snapshot
13664 for the next source line executed. The @code{tfind pc} command with
13665 no argument selects the next snapshot with the same program counter
13666 (PC) as the current frame. The @code{tfind tracepoint} command with
13667 no argument selects the next trace snapshot collected by the same
13668 tracepoint as the current one.
13670 In addition to letting you scan through the trace buffer manually,
13671 these commands make it easy to construct @value{GDBN} scripts that
13672 scan through the trace buffer and print out whatever collected data
13673 you are interested in. Thus, if we want to examine the PC, FP, and SP
13674 registers from each trace frame in the buffer, we can say this:
13677 (@value{GDBP}) @b{tfind start}
13678 (@value{GDBP}) @b{while ($trace_frame != -1)}
13679 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13680 $trace_frame, $pc, $sp, $fp
13684 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13685 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13686 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13687 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13688 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13689 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13690 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13691 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13692 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13693 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13694 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13697 Or, if we want to examine the variable @code{X} at each source line in
13701 (@value{GDBP}) @b{tfind start}
13702 (@value{GDBP}) @b{while ($trace_frame != -1)}
13703 > printf "Frame %d, X == %d\n", $trace_frame, X
13713 @subsection @code{tdump}
13715 @cindex dump all data collected at tracepoint
13716 @cindex tracepoint data, display
13718 This command takes no arguments. It prints all the data collected at
13719 the current trace snapshot.
13722 (@value{GDBP}) @b{trace 444}
13723 (@value{GDBP}) @b{actions}
13724 Enter actions for tracepoint #2, one per line:
13725 > collect $regs, $locals, $args, gdb_long_test
13728 (@value{GDBP}) @b{tstart}
13730 (@value{GDBP}) @b{tfind line 444}
13731 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13733 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13735 (@value{GDBP}) @b{tdump}
13736 Data collected at tracepoint 2, trace frame 1:
13737 d0 0xc4aa0085 -995491707
13741 d4 0x71aea3d 119204413
13744 d7 0x380035 3670069
13745 a0 0x19e24a 1696330
13746 a1 0x3000668 50333288
13748 a3 0x322000 3284992
13749 a4 0x3000698 50333336
13750 a5 0x1ad3cc 1758156
13751 fp 0x30bf3c 0x30bf3c
13752 sp 0x30bf34 0x30bf34
13754 pc 0x20b2c8 0x20b2c8
13758 p = 0x20e5b4 "gdb-test"
13765 gdb_long_test = 17 '\021'
13770 @code{tdump} works by scanning the tracepoint's current collection
13771 actions and printing the value of each expression listed. So
13772 @code{tdump} can fail, if after a run, you change the tracepoint's
13773 actions to mention variables that were not collected during the run.
13775 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13776 uses the collected value of @code{$pc} to distinguish between trace
13777 frames that were collected at the tracepoint hit, and frames that were
13778 collected while stepping. This allows it to correctly choose whether
13779 to display the basic list of collections, or the collections from the
13780 body of the while-stepping loop. However, if @code{$pc} was not collected,
13781 then @code{tdump} will always attempt to dump using the basic collection
13782 list, and may fail if a while-stepping frame does not include all the
13783 same data that is collected at the tracepoint hit.
13784 @c This is getting pretty arcane, example would be good.
13786 @node save tracepoints
13787 @subsection @code{save tracepoints @var{filename}}
13788 @kindex save tracepoints
13789 @kindex save-tracepoints
13790 @cindex save tracepoints for future sessions
13792 This command saves all current tracepoint definitions together with
13793 their actions and passcounts, into a file @file{@var{filename}}
13794 suitable for use in a later debugging session. To read the saved
13795 tracepoint definitions, use the @code{source} command (@pxref{Command
13796 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13797 alias for @w{@code{save tracepoints}}
13799 @node Tracepoint Variables
13800 @section Convenience Variables for Tracepoints
13801 @cindex tracepoint variables
13802 @cindex convenience variables for tracepoints
13805 @vindex $trace_frame
13806 @item (int) $trace_frame
13807 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13808 snapshot is selected.
13810 @vindex $tracepoint
13811 @item (int) $tracepoint
13812 The tracepoint for the current trace snapshot.
13814 @vindex $trace_line
13815 @item (int) $trace_line
13816 The line number for the current trace snapshot.
13818 @vindex $trace_file
13819 @item (char []) $trace_file
13820 The source file for the current trace snapshot.
13822 @vindex $trace_func
13823 @item (char []) $trace_func
13824 The name of the function containing @code{$tracepoint}.
13827 Note: @code{$trace_file} is not suitable for use in @code{printf},
13828 use @code{output} instead.
13830 Here's a simple example of using these convenience variables for
13831 stepping through all the trace snapshots and printing some of their
13832 data. Note that these are not the same as trace state variables,
13833 which are managed by the target.
13836 (@value{GDBP}) @b{tfind start}
13838 (@value{GDBP}) @b{while $trace_frame != -1}
13839 > output $trace_file
13840 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13846 @section Using Trace Files
13847 @cindex trace files
13849 In some situations, the target running a trace experiment may no
13850 longer be available; perhaps it crashed, or the hardware was needed
13851 for a different activity. To handle these cases, you can arrange to
13852 dump the trace data into a file, and later use that file as a source
13853 of trace data, via the @code{target tfile} command.
13858 @item tsave [ -r ] @var{filename}
13859 @itemx tsave [-ctf] @var{dirname}
13860 Save the trace data to @var{filename}. By default, this command
13861 assumes that @var{filename} refers to the host filesystem, so if
13862 necessary @value{GDBN} will copy raw trace data up from the target and
13863 then save it. If the target supports it, you can also supply the
13864 optional argument @code{-r} (``remote'') to direct the target to save
13865 the data directly into @var{filename} in its own filesystem, which may be
13866 more efficient if the trace buffer is very large. (Note, however, that
13867 @code{target tfile} can only read from files accessible to the host.)
13868 By default, this command will save trace frame in tfile format.
13869 You can supply the optional argument @code{-ctf} to save data in CTF
13870 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13871 that can be shared by multiple debugging and tracing tools. Please go to
13872 @indicateurl{http://www.efficios.com/ctf} to get more information.
13874 @kindex target tfile
13878 @item target tfile @var{filename}
13879 @itemx target ctf @var{dirname}
13880 Use the file named @var{filename} or directory named @var{dirname} as
13881 a source of trace data. Commands that examine data work as they do with
13882 a live target, but it is not possible to run any new trace experiments.
13883 @code{tstatus} will report the state of the trace run at the moment
13884 the data was saved, as well as the current trace frame you are examining.
13885 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13889 (@value{GDBP}) target ctf ctf.ctf
13890 (@value{GDBP}) tfind
13891 Found trace frame 0, tracepoint 2
13892 39 ++a; /* set tracepoint 1 here */
13893 (@value{GDBP}) tdump
13894 Data collected at tracepoint 2, trace frame 0:
13898 c = @{"123", "456", "789", "123", "456", "789"@}
13899 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13907 @chapter Debugging Programs That Use Overlays
13910 If your program is too large to fit completely in your target system's
13911 memory, you can sometimes use @dfn{overlays} to work around this
13912 problem. @value{GDBN} provides some support for debugging programs that
13916 * How Overlays Work:: A general explanation of overlays.
13917 * Overlay Commands:: Managing overlays in @value{GDBN}.
13918 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13919 mapped by asking the inferior.
13920 * Overlay Sample Program:: A sample program using overlays.
13923 @node How Overlays Work
13924 @section How Overlays Work
13925 @cindex mapped overlays
13926 @cindex unmapped overlays
13927 @cindex load address, overlay's
13928 @cindex mapped address
13929 @cindex overlay area
13931 Suppose you have a computer whose instruction address space is only 64
13932 kilobytes long, but which has much more memory which can be accessed by
13933 other means: special instructions, segment registers, or memory
13934 management hardware, for example. Suppose further that you want to
13935 adapt a program which is larger than 64 kilobytes to run on this system.
13937 One solution is to identify modules of your program which are relatively
13938 independent, and need not call each other directly; call these modules
13939 @dfn{overlays}. Separate the overlays from the main program, and place
13940 their machine code in the larger memory. Place your main program in
13941 instruction memory, but leave at least enough space there to hold the
13942 largest overlay as well.
13944 Now, to call a function located in an overlay, you must first copy that
13945 overlay's machine code from the large memory into the space set aside
13946 for it in the instruction memory, and then jump to its entry point
13949 @c NB: In the below the mapped area's size is greater or equal to the
13950 @c size of all overlays. This is intentional to remind the developer
13951 @c that overlays don't necessarily need to be the same size.
13955 Data Instruction Larger
13956 Address Space Address Space Address Space
13957 +-----------+ +-----------+ +-----------+
13959 +-----------+ +-----------+ +-----------+<-- overlay 1
13960 | program | | main | .----| overlay 1 | load address
13961 | variables | | program | | +-----------+
13962 | and heap | | | | | |
13963 +-----------+ | | | +-----------+<-- overlay 2
13964 | | +-----------+ | | | load address
13965 +-----------+ | | | .-| overlay 2 |
13967 mapped --->+-----------+ | | +-----------+
13968 address | | | | | |
13969 | overlay | <-' | | |
13970 | area | <---' +-----------+<-- overlay 3
13971 | | <---. | | load address
13972 +-----------+ `--| overlay 3 |
13979 @anchor{A code overlay}A code overlay
13983 The diagram (@pxref{A code overlay}) shows a system with separate data
13984 and instruction address spaces. To map an overlay, the program copies
13985 its code from the larger address space to the instruction address space.
13986 Since the overlays shown here all use the same mapped address, only one
13987 may be mapped at a time. For a system with a single address space for
13988 data and instructions, the diagram would be similar, except that the
13989 program variables and heap would share an address space with the main
13990 program and the overlay area.
13992 An overlay loaded into instruction memory and ready for use is called a
13993 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13994 instruction memory. An overlay not present (or only partially present)
13995 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13996 is its address in the larger memory. The mapped address is also called
13997 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13998 called the @dfn{load memory address}, or @dfn{LMA}.
14000 Unfortunately, overlays are not a completely transparent way to adapt a
14001 program to limited instruction memory. They introduce a new set of
14002 global constraints you must keep in mind as you design your program:
14007 Before calling or returning to a function in an overlay, your program
14008 must make sure that overlay is actually mapped. Otherwise, the call or
14009 return will transfer control to the right address, but in the wrong
14010 overlay, and your program will probably crash.
14013 If the process of mapping an overlay is expensive on your system, you
14014 will need to choose your overlays carefully to minimize their effect on
14015 your program's performance.
14018 The executable file you load onto your system must contain each
14019 overlay's instructions, appearing at the overlay's load address, not its
14020 mapped address. However, each overlay's instructions must be relocated
14021 and its symbols defined as if the overlay were at its mapped address.
14022 You can use GNU linker scripts to specify different load and relocation
14023 addresses for pieces of your program; see @ref{Overlay Description,,,
14024 ld.info, Using ld: the GNU linker}.
14027 The procedure for loading executable files onto your system must be able
14028 to load their contents into the larger address space as well as the
14029 instruction and data spaces.
14033 The overlay system described above is rather simple, and could be
14034 improved in many ways:
14039 If your system has suitable bank switch registers or memory management
14040 hardware, you could use those facilities to make an overlay's load area
14041 contents simply appear at their mapped address in instruction space.
14042 This would probably be faster than copying the overlay to its mapped
14043 area in the usual way.
14046 If your overlays are small enough, you could set aside more than one
14047 overlay area, and have more than one overlay mapped at a time.
14050 You can use overlays to manage data, as well as instructions. In
14051 general, data overlays are even less transparent to your design than
14052 code overlays: whereas code overlays only require care when you call or
14053 return to functions, data overlays require care every time you access
14054 the data. Also, if you change the contents of a data overlay, you
14055 must copy its contents back out to its load address before you can copy a
14056 different data overlay into the same mapped area.
14061 @node Overlay Commands
14062 @section Overlay Commands
14064 To use @value{GDBN}'s overlay support, each overlay in your program must
14065 correspond to a separate section of the executable file. The section's
14066 virtual memory address and load memory address must be the overlay's
14067 mapped and load addresses. Identifying overlays with sections allows
14068 @value{GDBN} to determine the appropriate address of a function or
14069 variable, depending on whether the overlay is mapped or not.
14071 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14072 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14077 Disable @value{GDBN}'s overlay support. When overlay support is
14078 disabled, @value{GDBN} assumes that all functions and variables are
14079 always present at their mapped addresses. By default, @value{GDBN}'s
14080 overlay support is disabled.
14082 @item overlay manual
14083 @cindex manual overlay debugging
14084 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14085 relies on you to tell it which overlays are mapped, and which are not,
14086 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14087 commands described below.
14089 @item overlay map-overlay @var{overlay}
14090 @itemx overlay map @var{overlay}
14091 @cindex map an overlay
14092 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14093 be the name of the object file section containing the overlay. When an
14094 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14095 functions and variables at their mapped addresses. @value{GDBN} assumes
14096 that any other overlays whose mapped ranges overlap that of
14097 @var{overlay} are now unmapped.
14099 @item overlay unmap-overlay @var{overlay}
14100 @itemx overlay unmap @var{overlay}
14101 @cindex unmap an overlay
14102 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14103 must be the name of the object file section containing the overlay.
14104 When an overlay is unmapped, @value{GDBN} assumes it can find the
14105 overlay's functions and variables at their load addresses.
14108 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14109 consults a data structure the overlay manager maintains in the inferior
14110 to see which overlays are mapped. For details, see @ref{Automatic
14111 Overlay Debugging}.
14113 @item overlay load-target
14114 @itemx overlay load
14115 @cindex reloading the overlay table
14116 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14117 re-reads the table @value{GDBN} automatically each time the inferior
14118 stops, so this command should only be necessary if you have changed the
14119 overlay mapping yourself using @value{GDBN}. This command is only
14120 useful when using automatic overlay debugging.
14122 @item overlay list-overlays
14123 @itemx overlay list
14124 @cindex listing mapped overlays
14125 Display a list of the overlays currently mapped, along with their mapped
14126 addresses, load addresses, and sizes.
14130 Normally, when @value{GDBN} prints a code address, it includes the name
14131 of the function the address falls in:
14134 (@value{GDBP}) print main
14135 $3 = @{int ()@} 0x11a0 <main>
14138 When overlay debugging is enabled, @value{GDBN} recognizes code in
14139 unmapped overlays, and prints the names of unmapped functions with
14140 asterisks around them. For example, if @code{foo} is a function in an
14141 unmapped overlay, @value{GDBN} prints it this way:
14144 (@value{GDBP}) overlay list
14145 No sections are mapped.
14146 (@value{GDBP}) print foo
14147 $5 = @{int (int)@} 0x100000 <*foo*>
14150 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14154 (@value{GDBP}) overlay list
14155 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14156 mapped at 0x1016 - 0x104a
14157 (@value{GDBP}) print foo
14158 $6 = @{int (int)@} 0x1016 <foo>
14161 When overlay debugging is enabled, @value{GDBN} can find the correct
14162 address for functions and variables in an overlay, whether or not the
14163 overlay is mapped. This allows most @value{GDBN} commands, like
14164 @code{break} and @code{disassemble}, to work normally, even on unmapped
14165 code. However, @value{GDBN}'s breakpoint support has some limitations:
14169 @cindex breakpoints in overlays
14170 @cindex overlays, setting breakpoints in
14171 You can set breakpoints in functions in unmapped overlays, as long as
14172 @value{GDBN} can write to the overlay at its load address.
14174 @value{GDBN} can not set hardware or simulator-based breakpoints in
14175 unmapped overlays. However, if you set a breakpoint at the end of your
14176 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14177 you are using manual overlay management), @value{GDBN} will re-set its
14178 breakpoints properly.
14182 @node Automatic Overlay Debugging
14183 @section Automatic Overlay Debugging
14184 @cindex automatic overlay debugging
14186 @value{GDBN} can automatically track which overlays are mapped and which
14187 are not, given some simple co-operation from the overlay manager in the
14188 inferior. If you enable automatic overlay debugging with the
14189 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14190 looks in the inferior's memory for certain variables describing the
14191 current state of the overlays.
14193 Here are the variables your overlay manager must define to support
14194 @value{GDBN}'s automatic overlay debugging:
14198 @item @code{_ovly_table}:
14199 This variable must be an array of the following structures:
14204 /* The overlay's mapped address. */
14207 /* The size of the overlay, in bytes. */
14208 unsigned long size;
14210 /* The overlay's load address. */
14213 /* Non-zero if the overlay is currently mapped;
14215 unsigned long mapped;
14219 @item @code{_novlys}:
14220 This variable must be a four-byte signed integer, holding the total
14221 number of elements in @code{_ovly_table}.
14225 To decide whether a particular overlay is mapped or not, @value{GDBN}
14226 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14227 @code{lma} members equal the VMA and LMA of the overlay's section in the
14228 executable file. When @value{GDBN} finds a matching entry, it consults
14229 the entry's @code{mapped} member to determine whether the overlay is
14232 In addition, your overlay manager may define a function called
14233 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14234 will silently set a breakpoint there. If the overlay manager then
14235 calls this function whenever it has changed the overlay table, this
14236 will enable @value{GDBN} to accurately keep track of which overlays
14237 are in program memory, and update any breakpoints that may be set
14238 in overlays. This will allow breakpoints to work even if the
14239 overlays are kept in ROM or other non-writable memory while they
14240 are not being executed.
14242 @node Overlay Sample Program
14243 @section Overlay Sample Program
14244 @cindex overlay example program
14246 When linking a program which uses overlays, you must place the overlays
14247 at their load addresses, while relocating them to run at their mapped
14248 addresses. To do this, you must write a linker script (@pxref{Overlay
14249 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14250 since linker scripts are specific to a particular host system, target
14251 architecture, and target memory layout, this manual cannot provide
14252 portable sample code demonstrating @value{GDBN}'s overlay support.
14254 However, the @value{GDBN} source distribution does contain an overlaid
14255 program, with linker scripts for a few systems, as part of its test
14256 suite. The program consists of the following files from
14257 @file{gdb/testsuite/gdb.base}:
14261 The main program file.
14263 A simple overlay manager, used by @file{overlays.c}.
14268 Overlay modules, loaded and used by @file{overlays.c}.
14271 Linker scripts for linking the test program on the @code{d10v-elf}
14272 and @code{m32r-elf} targets.
14275 You can build the test program using the @code{d10v-elf} GCC
14276 cross-compiler like this:
14279 $ d10v-elf-gcc -g -c overlays.c
14280 $ d10v-elf-gcc -g -c ovlymgr.c
14281 $ d10v-elf-gcc -g -c foo.c
14282 $ d10v-elf-gcc -g -c bar.c
14283 $ d10v-elf-gcc -g -c baz.c
14284 $ d10v-elf-gcc -g -c grbx.c
14285 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14286 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14289 The build process is identical for any other architecture, except that
14290 you must substitute the appropriate compiler and linker script for the
14291 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14295 @chapter Using @value{GDBN} with Different Languages
14298 Although programming languages generally have common aspects, they are
14299 rarely expressed in the same manner. For instance, in ANSI C,
14300 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14301 Modula-2, it is accomplished by @code{p^}. Values can also be
14302 represented (and displayed) differently. Hex numbers in C appear as
14303 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14305 @cindex working language
14306 Language-specific information is built into @value{GDBN} for some languages,
14307 allowing you to express operations like the above in your program's
14308 native language, and allowing @value{GDBN} to output values in a manner
14309 consistent with the syntax of your program's native language. The
14310 language you use to build expressions is called the @dfn{working
14314 * Setting:: Switching between source languages
14315 * Show:: Displaying the language
14316 * Checks:: Type and range checks
14317 * Supported Languages:: Supported languages
14318 * Unsupported Languages:: Unsupported languages
14322 @section Switching Between Source Languages
14324 There are two ways to control the working language---either have @value{GDBN}
14325 set it automatically, or select it manually yourself. You can use the
14326 @code{set language} command for either purpose. On startup, @value{GDBN}
14327 defaults to setting the language automatically. The working language is
14328 used to determine how expressions you type are interpreted, how values
14331 In addition to the working language, every source file that
14332 @value{GDBN} knows about has its own working language. For some object
14333 file formats, the compiler might indicate which language a particular
14334 source file is in. However, most of the time @value{GDBN} infers the
14335 language from the name of the file. The language of a source file
14336 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14337 show each frame appropriately for its own language. There is no way to
14338 set the language of a source file from within @value{GDBN}, but you can
14339 set the language associated with a filename extension. @xref{Show, ,
14340 Displaying the Language}.
14342 This is most commonly a problem when you use a program, such
14343 as @code{cfront} or @code{f2c}, that generates C but is written in
14344 another language. In that case, make the
14345 program use @code{#line} directives in its C output; that way
14346 @value{GDBN} will know the correct language of the source code of the original
14347 program, and will display that source code, not the generated C code.
14350 * Filenames:: Filename extensions and languages.
14351 * Manually:: Setting the working language manually
14352 * Automatically:: Having @value{GDBN} infer the source language
14356 @subsection List of Filename Extensions and Languages
14358 If a source file name ends in one of the following extensions, then
14359 @value{GDBN} infers that its language is the one indicated.
14377 C@t{++} source file
14383 Objective-C source file
14387 Fortran source file
14390 Modula-2 source file
14394 Assembler source file. This actually behaves almost like C, but
14395 @value{GDBN} does not skip over function prologues when stepping.
14398 In addition, you may set the language associated with a filename
14399 extension. @xref{Show, , Displaying the Language}.
14402 @subsection Setting the Working Language
14404 If you allow @value{GDBN} to set the language automatically,
14405 expressions are interpreted the same way in your debugging session and
14408 @kindex set language
14409 If you wish, you may set the language manually. To do this, issue the
14410 command @samp{set language @var{lang}}, where @var{lang} is the name of
14411 a language, such as
14412 @code{c} or @code{modula-2}.
14413 For a list of the supported languages, type @samp{set language}.
14415 Setting the language manually prevents @value{GDBN} from updating the working
14416 language automatically. This can lead to confusion if you try
14417 to debug a program when the working language is not the same as the
14418 source language, when an expression is acceptable to both
14419 languages---but means different things. For instance, if the current
14420 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14428 might not have the effect you intended. In C, this means to add
14429 @code{b} and @code{c} and place the result in @code{a}. The result
14430 printed would be the value of @code{a}. In Modula-2, this means to compare
14431 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14433 @node Automatically
14434 @subsection Having @value{GDBN} Infer the Source Language
14436 To have @value{GDBN} set the working language automatically, use
14437 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14438 then infers the working language. That is, when your program stops in a
14439 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14440 working language to the language recorded for the function in that
14441 frame. If the language for a frame is unknown (that is, if the function
14442 or block corresponding to the frame was defined in a source file that
14443 does not have a recognized extension), the current working language is
14444 not changed, and @value{GDBN} issues a warning.
14446 This may not seem necessary for most programs, which are written
14447 entirely in one source language. However, program modules and libraries
14448 written in one source language can be used by a main program written in
14449 a different source language. Using @samp{set language auto} in this
14450 case frees you from having to set the working language manually.
14453 @section Displaying the Language
14455 The following commands help you find out which language is the
14456 working language, and also what language source files were written in.
14459 @item show language
14460 @anchor{show language}
14461 @kindex show language
14462 Display the current working language. This is the
14463 language you can use with commands such as @code{print} to
14464 build and compute expressions that may involve variables in your program.
14467 @kindex info frame@r{, show the source language}
14468 Display the source language for this frame. This language becomes the
14469 working language if you use an identifier from this frame.
14470 @xref{Frame Info, ,Information about a Frame}, to identify the other
14471 information listed here.
14474 @kindex info source@r{, show the source language}
14475 Display the source language of this source file.
14476 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14477 information listed here.
14480 In unusual circumstances, you may have source files with extensions
14481 not in the standard list. You can then set the extension associated
14482 with a language explicitly:
14485 @item set extension-language @var{ext} @var{language}
14486 @kindex set extension-language
14487 Tell @value{GDBN} that source files with extension @var{ext} are to be
14488 assumed as written in the source language @var{language}.
14490 @item info extensions
14491 @kindex info extensions
14492 List all the filename extensions and the associated languages.
14496 @section Type and Range Checking
14498 Some languages are designed to guard you against making seemingly common
14499 errors through a series of compile- and run-time checks. These include
14500 checking the type of arguments to functions and operators and making
14501 sure mathematical overflows are caught at run time. Checks such as
14502 these help to ensure a program's correctness once it has been compiled
14503 by eliminating type mismatches and providing active checks for range
14504 errors when your program is running.
14506 By default @value{GDBN} checks for these errors according to the
14507 rules of the current source language. Although @value{GDBN} does not check
14508 the statements in your program, it can check expressions entered directly
14509 into @value{GDBN} for evaluation via the @code{print} command, for example.
14512 * Type Checking:: An overview of type checking
14513 * Range Checking:: An overview of range checking
14516 @cindex type checking
14517 @cindex checks, type
14518 @node Type Checking
14519 @subsection An Overview of Type Checking
14521 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14522 arguments to operators and functions have to be of the correct type,
14523 otherwise an error occurs. These checks prevent type mismatch
14524 errors from ever causing any run-time problems. For example,
14527 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14529 (@value{GDBP}) print obj.my_method (0)
14532 (@value{GDBP}) print obj.my_method (0x1234)
14533 Cannot resolve method klass::my_method to any overloaded instance
14536 The second example fails because in C@t{++} the integer constant
14537 @samp{0x1234} is not type-compatible with the pointer parameter type.
14539 For the expressions you use in @value{GDBN} commands, you can tell
14540 @value{GDBN} to not enforce strict type checking or
14541 to treat any mismatches as errors and abandon the expression;
14542 When type checking is disabled, @value{GDBN} successfully evaluates
14543 expressions like the second example above.
14545 Even if type checking is off, there may be other reasons
14546 related to type that prevent @value{GDBN} from evaluating an expression.
14547 For instance, @value{GDBN} does not know how to add an @code{int} and
14548 a @code{struct foo}. These particular type errors have nothing to do
14549 with the language in use and usually arise from expressions which make
14550 little sense to evaluate anyway.
14552 @value{GDBN} provides some additional commands for controlling type checking:
14554 @kindex set check type
14555 @kindex show check type
14557 @item set check type on
14558 @itemx set check type off
14559 Set strict type checking on or off. If any type mismatches occur in
14560 evaluating an expression while type checking is on, @value{GDBN} prints a
14561 message and aborts evaluation of the expression.
14563 @item show check type
14564 Show the current setting of type checking and whether @value{GDBN}
14565 is enforcing strict type checking rules.
14568 @cindex range checking
14569 @cindex checks, range
14570 @node Range Checking
14571 @subsection An Overview of Range Checking
14573 In some languages (such as Modula-2), it is an error to exceed the
14574 bounds of a type; this is enforced with run-time checks. Such range
14575 checking is meant to ensure program correctness by making sure
14576 computations do not overflow, or indices on an array element access do
14577 not exceed the bounds of the array.
14579 For expressions you use in @value{GDBN} commands, you can tell
14580 @value{GDBN} to treat range errors in one of three ways: ignore them,
14581 always treat them as errors and abandon the expression, or issue
14582 warnings but evaluate the expression anyway.
14584 A range error can result from numerical overflow, from exceeding an
14585 array index bound, or when you type a constant that is not a member
14586 of any type. Some languages, however, do not treat overflows as an
14587 error. In many implementations of C, mathematical overflow causes the
14588 result to ``wrap around'' to lower values---for example, if @var{m} is
14589 the largest integer value, and @var{s} is the smallest, then
14592 @var{m} + 1 @result{} @var{s}
14595 This, too, is specific to individual languages, and in some cases
14596 specific to individual compilers or machines. @xref{Supported Languages, ,
14597 Supported Languages}, for further details on specific languages.
14599 @value{GDBN} provides some additional commands for controlling the range checker:
14601 @kindex set check range
14602 @kindex show check range
14604 @item set check range auto
14605 Set range checking on or off based on the current working language.
14606 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14609 @item set check range on
14610 @itemx set check range off
14611 Set range checking on or off, overriding the default setting for the
14612 current working language. A warning is issued if the setting does not
14613 match the language default. If a range error occurs and range checking is on,
14614 then a message is printed and evaluation of the expression is aborted.
14616 @item set check range warn
14617 Output messages when the @value{GDBN} range checker detects a range error,
14618 but attempt to evaluate the expression anyway. Evaluating the
14619 expression may still be impossible for other reasons, such as accessing
14620 memory that the process does not own (a typical example from many Unix
14624 Show the current setting of the range checker, and whether or not it is
14625 being set automatically by @value{GDBN}.
14628 @node Supported Languages
14629 @section Supported Languages
14631 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
14632 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
14633 @c This is false ...
14634 Some @value{GDBN} features may be used in expressions regardless of the
14635 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14636 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14637 ,Expressions}) can be used with the constructs of any supported
14640 The following sections detail to what degree each source language is
14641 supported by @value{GDBN}. These sections are not meant to be language
14642 tutorials or references, but serve only as a reference guide to what the
14643 @value{GDBN} expression parser accepts, and what input and output
14644 formats should look like for different languages. There are many good
14645 books written on each of these languages; please look to these for a
14646 language reference or tutorial.
14649 * C:: C and C@t{++}
14652 * Objective-C:: Objective-C
14653 * OpenCL C:: OpenCL C
14654 * Fortran:: Fortran
14657 * Modula-2:: Modula-2
14662 @subsection C and C@t{++}
14664 @cindex C and C@t{++}
14665 @cindex expressions in C or C@t{++}
14667 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14668 to both languages. Whenever this is the case, we discuss those languages
14672 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14673 @cindex @sc{gnu} C@t{++}
14674 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14675 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14676 effectively, you must compile your C@t{++} programs with a supported
14677 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14678 compiler (@code{aCC}).
14681 * C Operators:: C and C@t{++} operators
14682 * C Constants:: C and C@t{++} constants
14683 * C Plus Plus Expressions:: C@t{++} expressions
14684 * C Defaults:: Default settings for C and C@t{++}
14685 * C Checks:: C and C@t{++} type and range checks
14686 * Debugging C:: @value{GDBN} and C
14687 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14688 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14692 @subsubsection C and C@t{++} Operators
14694 @cindex C and C@t{++} operators
14696 Operators must be defined on values of specific types. For instance,
14697 @code{+} is defined on numbers, but not on structures. Operators are
14698 often defined on groups of types.
14700 For the purposes of C and C@t{++}, the following definitions hold:
14705 @emph{Integral types} include @code{int} with any of its storage-class
14706 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14709 @emph{Floating-point types} include @code{float}, @code{double}, and
14710 @code{long double} (if supported by the target platform).
14713 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14716 @emph{Scalar types} include all of the above.
14721 The following operators are supported. They are listed here
14722 in order of increasing precedence:
14726 The comma or sequencing operator. Expressions in a comma-separated list
14727 are evaluated from left to right, with the result of the entire
14728 expression being the last expression evaluated.
14731 Assignment. The value of an assignment expression is the value
14732 assigned. Defined on scalar types.
14735 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14736 and translated to @w{@code{@var{a} = @var{a op b}}}.
14737 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14738 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14739 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14742 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14743 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14744 should be of an integral type.
14747 Logical @sc{or}. Defined on integral types.
14750 Logical @sc{and}. Defined on integral types.
14753 Bitwise @sc{or}. Defined on integral types.
14756 Bitwise exclusive-@sc{or}. Defined on integral types.
14759 Bitwise @sc{and}. Defined on integral types.
14762 Equality and inequality. Defined on scalar types. The value of these
14763 expressions is 0 for false and non-zero for true.
14765 @item <@r{, }>@r{, }<=@r{, }>=
14766 Less than, greater than, less than or equal, greater than or equal.
14767 Defined on scalar types. The value of these expressions is 0 for false
14768 and non-zero for true.
14771 left shift, and right shift. Defined on integral types.
14774 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14777 Addition and subtraction. Defined on integral types, floating-point types and
14780 @item *@r{, }/@r{, }%
14781 Multiplication, division, and modulus. Multiplication and division are
14782 defined on integral and floating-point types. Modulus is defined on
14786 Increment and decrement. When appearing before a variable, the
14787 operation is performed before the variable is used in an expression;
14788 when appearing after it, the variable's value is used before the
14789 operation takes place.
14792 Pointer dereferencing. Defined on pointer types. Same precedence as
14796 Address operator. Defined on variables. Same precedence as @code{++}.
14798 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14799 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14800 to examine the address
14801 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14805 Negative. Defined on integral and floating-point types. Same
14806 precedence as @code{++}.
14809 Logical negation. Defined on integral types. Same precedence as
14813 Bitwise complement operator. Defined on integral types. Same precedence as
14818 Structure member, and pointer-to-structure member. For convenience,
14819 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14820 pointer based on the stored type information.
14821 Defined on @code{struct} and @code{union} data.
14824 Dereferences of pointers to members.
14827 Array indexing. @code{@var{a}[@var{i}]} is defined as
14828 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14831 Function parameter list. Same precedence as @code{->}.
14834 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14835 and @code{class} types.
14838 Doubled colons also represent the @value{GDBN} scope operator
14839 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14843 If an operator is redefined in the user code, @value{GDBN} usually
14844 attempts to invoke the redefined version instead of using the operator's
14845 predefined meaning.
14848 @subsubsection C and C@t{++} Constants
14850 @cindex C and C@t{++} constants
14852 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14857 Integer constants are a sequence of digits. Octal constants are
14858 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14859 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14860 @samp{l}, specifying that the constant should be treated as a
14864 Floating point constants are a sequence of digits, followed by a decimal
14865 point, followed by a sequence of digits, and optionally followed by an
14866 exponent. An exponent is of the form:
14867 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14868 sequence of digits. The @samp{+} is optional for positive exponents.
14869 A floating-point constant may also end with a letter @samp{f} or
14870 @samp{F}, specifying that the constant should be treated as being of
14871 the @code{float} (as opposed to the default @code{double}) type; or with
14872 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14876 Enumerated constants consist of enumerated identifiers, or their
14877 integral equivalents.
14880 Character constants are a single character surrounded by single quotes
14881 (@code{'}), or a number---the ordinal value of the corresponding character
14882 (usually its @sc{ascii} value). Within quotes, the single character may
14883 be represented by a letter or by @dfn{escape sequences}, which are of
14884 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14885 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14886 @samp{@var{x}} is a predefined special character---for example,
14887 @samp{\n} for newline.
14889 Wide character constants can be written by prefixing a character
14890 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14891 form of @samp{x}. The target wide character set is used when
14892 computing the value of this constant (@pxref{Character Sets}).
14895 String constants are a sequence of character constants surrounded by
14896 double quotes (@code{"}). Any valid character constant (as described
14897 above) may appear. Double quotes within the string must be preceded by
14898 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14901 Wide string constants can be written by prefixing a string constant
14902 with @samp{L}, as in C. The target wide character set is used when
14903 computing the value of this constant (@pxref{Character Sets}).
14906 Pointer constants are an integral value. You can also write pointers
14907 to constants using the C operator @samp{&}.
14910 Array constants are comma-separated lists surrounded by braces @samp{@{}
14911 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14912 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14913 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14916 @node C Plus Plus Expressions
14917 @subsubsection C@t{++} Expressions
14919 @cindex expressions in C@t{++}
14920 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14922 @cindex debugging C@t{++} programs
14923 @cindex C@t{++} compilers
14924 @cindex debug formats and C@t{++}
14925 @cindex @value{NGCC} and C@t{++}
14927 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14928 the proper compiler and the proper debug format. Currently,
14929 @value{GDBN} works best when debugging C@t{++} code that is compiled
14930 with the most recent version of @value{NGCC} possible. The DWARF
14931 debugging format is preferred; @value{NGCC} defaults to this on most
14932 popular platforms. Other compilers and/or debug formats are likely to
14933 work badly or not at all when using @value{GDBN} to debug C@t{++}
14934 code. @xref{Compilation}.
14939 @cindex member functions
14941 Member function calls are allowed; you can use expressions like
14944 count = aml->GetOriginal(x, y)
14947 @vindex this@r{, inside C@t{++} member functions}
14948 @cindex namespace in C@t{++}
14950 While a member function is active (in the selected stack frame), your
14951 expressions have the same namespace available as the member function;
14952 that is, @value{GDBN} allows implicit references to the class instance
14953 pointer @code{this} following the same rules as C@t{++}. @code{using}
14954 declarations in the current scope are also respected by @value{GDBN}.
14956 @cindex call overloaded functions
14957 @cindex overloaded functions, calling
14958 @cindex type conversions in C@t{++}
14960 You can call overloaded functions; @value{GDBN} resolves the function
14961 call to the right definition, with some restrictions. @value{GDBN} does not
14962 perform overload resolution involving user-defined type conversions,
14963 calls to constructors, or instantiations of templates that do not exist
14964 in the program. It also cannot handle ellipsis argument lists or
14967 It does perform integral conversions and promotions, floating-point
14968 promotions, arithmetic conversions, pointer conversions, conversions of
14969 class objects to base classes, and standard conversions such as those of
14970 functions or arrays to pointers; it requires an exact match on the
14971 number of function arguments.
14973 Overload resolution is always performed, unless you have specified
14974 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14975 ,@value{GDBN} Features for C@t{++}}.
14977 You must specify @code{set overload-resolution off} in order to use an
14978 explicit function signature to call an overloaded function, as in
14980 p 'foo(char,int)'('x', 13)
14983 The @value{GDBN} command-completion facility can simplify this;
14984 see @ref{Completion, ,Command Completion}.
14986 @cindex reference declarations
14988 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
14989 references; you can use them in expressions just as you do in C@t{++}
14990 source---they are automatically dereferenced.
14992 In the parameter list shown when @value{GDBN} displays a frame, the values of
14993 reference variables are not displayed (unlike other variables); this
14994 avoids clutter, since references are often used for large structures.
14995 The @emph{address} of a reference variable is always shown, unless
14996 you have specified @samp{set print address off}.
14999 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
15000 expressions can use it just as expressions in your program do. Since
15001 one scope may be defined in another, you can use @code{::} repeatedly if
15002 necessary, for example in an expression like
15003 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
15004 resolving name scope by reference to source files, in both C and C@t{++}
15005 debugging (@pxref{Variables, ,Program Variables}).
15008 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15013 @subsubsection C and C@t{++} Defaults
15015 @cindex C and C@t{++} defaults
15017 If you allow @value{GDBN} to set range checking automatically, it
15018 defaults to @code{off} whenever the working language changes to
15019 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15020 selects the working language.
15022 If you allow @value{GDBN} to set the language automatically, it
15023 recognizes source files whose names end with @file{.c}, @file{.C}, or
15024 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15025 these files, it sets the working language to C or C@t{++}.
15026 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15027 for further details.
15030 @subsubsection C and C@t{++} Type and Range Checks
15032 @cindex C and C@t{++} checks
15034 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15035 checking is used. However, if you turn type checking off, @value{GDBN}
15036 will allow certain non-standard conversions, such as promoting integer
15037 constants to pointers.
15039 Range checking, if turned on, is done on mathematical operations. Array
15040 indices are not checked, since they are often used to index a pointer
15041 that is not itself an array.
15044 @subsubsection @value{GDBN} and C
15046 The @code{set print union} and @code{show print union} commands apply to
15047 the @code{union} type. When set to @samp{on}, any @code{union} that is
15048 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15049 appears as @samp{@{...@}}.
15051 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15052 with pointers and a memory allocation function. @xref{Expressions,
15055 @node Debugging C Plus Plus
15056 @subsubsection @value{GDBN} Features for C@t{++}
15058 @cindex commands for C@t{++}
15060 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15061 designed specifically for use with C@t{++}. Here is a summary:
15064 @cindex break in overloaded functions
15065 @item @r{breakpoint menus}
15066 When you want a breakpoint in a function whose name is overloaded,
15067 @value{GDBN} has the capability to display a menu of possible breakpoint
15068 locations to help you specify which function definition you want.
15069 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15071 @cindex overloading in C@t{++}
15072 @item rbreak @var{regex}
15073 Setting breakpoints using regular expressions is helpful for setting
15074 breakpoints on overloaded functions that are not members of any special
15076 @xref{Set Breaks, ,Setting Breakpoints}.
15078 @cindex C@t{++} exception handling
15080 @itemx catch rethrow
15082 Debug C@t{++} exception handling using these commands. @xref{Set
15083 Catchpoints, , Setting Catchpoints}.
15085 @cindex inheritance
15086 @item ptype @var{typename}
15087 Print inheritance relationships as well as other information for type
15089 @xref{Symbols, ,Examining the Symbol Table}.
15091 @item info vtbl @var{expression}.
15092 The @code{info vtbl} command can be used to display the virtual
15093 method tables of the object computed by @var{expression}. This shows
15094 one entry per virtual table; there may be multiple virtual tables when
15095 multiple inheritance is in use.
15097 @cindex C@t{++} demangling
15098 @item demangle @var{name}
15099 Demangle @var{name}.
15100 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15102 @cindex C@t{++} symbol display
15103 @item set print demangle
15104 @itemx show print demangle
15105 @itemx set print asm-demangle
15106 @itemx show print asm-demangle
15107 Control whether C@t{++} symbols display in their source form, both when
15108 displaying code as C@t{++} source and when displaying disassemblies.
15109 @xref{Print Settings, ,Print Settings}.
15111 @item set print object
15112 @itemx show print object
15113 Choose whether to print derived (actual) or declared types of objects.
15114 @xref{Print Settings, ,Print Settings}.
15116 @item set print vtbl
15117 @itemx show print vtbl
15118 Control the format for printing virtual function tables.
15119 @xref{Print Settings, ,Print Settings}.
15120 (The @code{vtbl} commands do not work on programs compiled with the HP
15121 ANSI C@t{++} compiler (@code{aCC}).)
15123 @kindex set overload-resolution
15124 @cindex overloaded functions, overload resolution
15125 @item set overload-resolution on
15126 Enable overload resolution for C@t{++} expression evaluation. The default
15127 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15128 and searches for a function whose signature matches the argument types,
15129 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15130 Expressions, ,C@t{++} Expressions}, for details).
15131 If it cannot find a match, it emits a message.
15133 @item set overload-resolution off
15134 Disable overload resolution for C@t{++} expression evaluation. For
15135 overloaded functions that are not class member functions, @value{GDBN}
15136 chooses the first function of the specified name that it finds in the
15137 symbol table, whether or not its arguments are of the correct type. For
15138 overloaded functions that are class member functions, @value{GDBN}
15139 searches for a function whose signature @emph{exactly} matches the
15142 @kindex show overload-resolution
15143 @item show overload-resolution
15144 Show the current setting of overload resolution.
15146 @item @r{Overloaded symbol names}
15147 You can specify a particular definition of an overloaded symbol, using
15148 the same notation that is used to declare such symbols in C@t{++}: type
15149 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15150 also use the @value{GDBN} command-line word completion facilities to list the
15151 available choices, or to finish the type list for you.
15152 @xref{Completion,, Command Completion}, for details on how to do this.
15154 @item @r{Breakpoints in functions with ABI tags}
15156 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15157 correspond to changes in the ABI of a type, function, or variable that
15158 would not otherwise be reflected in a mangled name. See
15159 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15162 The ABI tags are visible in C@t{++} demangled names. For example, a
15163 function that returns a std::string:
15166 std::string function(int);
15170 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15171 tag, and @value{GDBN} displays the symbol like this:
15174 function[abi:cxx11](int)
15177 You can set a breakpoint on such functions simply as if they had no
15181 (gdb) b function(int)
15182 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15183 (gdb) info breakpoints
15184 Num Type Disp Enb Address What
15185 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15189 On the rare occasion you need to disambiguate between different ABI
15190 tags, you can do so by simply including the ABI tag in the function
15194 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15198 @node Decimal Floating Point
15199 @subsubsection Decimal Floating Point format
15200 @cindex decimal floating point format
15202 @value{GDBN} can examine, set and perform computations with numbers in
15203 decimal floating point format, which in the C language correspond to the
15204 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15205 specified by the extension to support decimal floating-point arithmetic.
15207 There are two encodings in use, depending on the architecture: BID (Binary
15208 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15209 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15212 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15213 to manipulate decimal floating point numbers, it is not possible to convert
15214 (using a cast, for example) integers wider than 32-bit to decimal float.
15216 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15217 point computations, error checking in decimal float operations ignores
15218 underflow, overflow and divide by zero exceptions.
15220 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15221 to inspect @code{_Decimal128} values stored in floating point registers.
15222 See @ref{PowerPC,,PowerPC} for more details.
15228 @value{GDBN} can be used to debug programs written in D and compiled with
15229 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15230 specific feature --- dynamic arrays.
15235 @cindex Go (programming language)
15236 @value{GDBN} can be used to debug programs written in Go and compiled with
15237 @file{gccgo} or @file{6g} compilers.
15239 Here is a summary of the Go-specific features and restrictions:
15242 @cindex current Go package
15243 @item The current Go package
15244 The name of the current package does not need to be specified when
15245 specifying global variables and functions.
15247 For example, given the program:
15251 var myglob = "Shall we?"
15257 When stopped inside @code{main} either of these work:
15261 (gdb) p main.myglob
15264 @cindex builtin Go types
15265 @item Builtin Go types
15266 The @code{string} type is recognized by @value{GDBN} and is printed
15269 @cindex builtin Go functions
15270 @item Builtin Go functions
15271 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15272 function and handles it internally.
15274 @cindex restrictions on Go expressions
15275 @item Restrictions on Go expressions
15276 All Go operators are supported except @code{&^}.
15277 The Go @code{_} ``blank identifier'' is not supported.
15278 Automatic dereferencing of pointers is not supported.
15282 @subsection Objective-C
15284 @cindex Objective-C
15285 This section provides information about some commands and command
15286 options that are useful for debugging Objective-C code. See also
15287 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15288 few more commands specific to Objective-C support.
15291 * Method Names in Commands::
15292 * The Print Command with Objective-C::
15295 @node Method Names in Commands
15296 @subsubsection Method Names in Commands
15298 The following commands have been extended to accept Objective-C method
15299 names as line specifications:
15301 @kindex clear@r{, and Objective-C}
15302 @kindex break@r{, and Objective-C}
15303 @kindex info line@r{, and Objective-C}
15304 @kindex jump@r{, and Objective-C}
15305 @kindex list@r{, and Objective-C}
15309 @item @code{info line}
15314 A fully qualified Objective-C method name is specified as
15317 -[@var{Class} @var{methodName}]
15320 where the minus sign is used to indicate an instance method and a
15321 plus sign (not shown) is used to indicate a class method. The class
15322 name @var{Class} and method name @var{methodName} are enclosed in
15323 brackets, similar to the way messages are specified in Objective-C
15324 source code. For example, to set a breakpoint at the @code{create}
15325 instance method of class @code{Fruit} in the program currently being
15329 break -[Fruit create]
15332 To list ten program lines around the @code{initialize} class method,
15336 list +[NSText initialize]
15339 In the current version of @value{GDBN}, the plus or minus sign is
15340 required. In future versions of @value{GDBN}, the plus or minus
15341 sign will be optional, but you can use it to narrow the search. It
15342 is also possible to specify just a method name:
15348 You must specify the complete method name, including any colons. If
15349 your program's source files contain more than one @code{create} method,
15350 you'll be presented with a numbered list of classes that implement that
15351 method. Indicate your choice by number, or type @samp{0} to exit if
15354 As another example, to clear a breakpoint established at the
15355 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15358 clear -[NSWindow makeKeyAndOrderFront:]
15361 @node The Print Command with Objective-C
15362 @subsubsection The Print Command With Objective-C
15363 @cindex Objective-C, print objects
15364 @kindex print-object
15365 @kindex po @r{(@code{print-object})}
15367 The print command has also been extended to accept methods. For example:
15370 print -[@var{object} hash]
15373 @cindex print an Objective-C object description
15374 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15376 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15377 and print the result. Also, an additional command has been added,
15378 @code{print-object} or @code{po} for short, which is meant to print
15379 the description of an object. However, this command may only work
15380 with certain Objective-C libraries that have a particular hook
15381 function, @code{_NSPrintForDebugger}, defined.
15384 @subsection OpenCL C
15387 This section provides information about @value{GDBN}s OpenCL C support.
15390 * OpenCL C Datatypes::
15391 * OpenCL C Expressions::
15392 * OpenCL C Operators::
15395 @node OpenCL C Datatypes
15396 @subsubsection OpenCL C Datatypes
15398 @cindex OpenCL C Datatypes
15399 @value{GDBN} supports the builtin scalar and vector datatypes specified
15400 by OpenCL 1.1. In addition the half- and double-precision floating point
15401 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15402 extensions are also known to @value{GDBN}.
15404 @node OpenCL C Expressions
15405 @subsubsection OpenCL C Expressions
15407 @cindex OpenCL C Expressions
15408 @value{GDBN} supports accesses to vector components including the access as
15409 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15410 supported by @value{GDBN} can be used as well.
15412 @node OpenCL C Operators
15413 @subsubsection OpenCL C Operators
15415 @cindex OpenCL C Operators
15416 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15420 @subsection Fortran
15421 @cindex Fortran-specific support in @value{GDBN}
15423 @value{GDBN} can be used to debug programs written in Fortran, but it
15424 currently supports only the features of Fortran 77 language.
15426 @cindex trailing underscore, in Fortran symbols
15427 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15428 among them) append an underscore to the names of variables and
15429 functions. When you debug programs compiled by those compilers, you
15430 will need to refer to variables and functions with a trailing
15434 * Fortran Operators:: Fortran operators and expressions
15435 * Fortran Defaults:: Default settings for Fortran
15436 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15439 @node Fortran Operators
15440 @subsubsection Fortran Operators and Expressions
15442 @cindex Fortran operators and expressions
15444 Operators must be defined on values of specific types. For instance,
15445 @code{+} is defined on numbers, but not on characters or other non-
15446 arithmetic types. Operators are often defined on groups of types.
15450 The exponentiation operator. It raises the first operand to the power
15454 The range operator. Normally used in the form of array(low:high) to
15455 represent a section of array.
15458 The access component operator. Normally used to access elements in derived
15459 types. Also suitable for unions. As unions aren't part of regular Fortran,
15460 this can only happen when accessing a register that uses a gdbarch-defined
15464 @node Fortran Defaults
15465 @subsubsection Fortran Defaults
15467 @cindex Fortran Defaults
15469 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15470 default uses case-insensitive matches for Fortran symbols. You can
15471 change that with the @samp{set case-insensitive} command, see
15472 @ref{Symbols}, for the details.
15474 @node Special Fortran Commands
15475 @subsubsection Special Fortran Commands
15477 @cindex Special Fortran commands
15479 @value{GDBN} has some commands to support Fortran-specific features,
15480 such as displaying common blocks.
15483 @cindex @code{COMMON} blocks, Fortran
15484 @kindex info common
15485 @item info common @r{[}@var{common-name}@r{]}
15486 This command prints the values contained in the Fortran @code{COMMON}
15487 block whose name is @var{common-name}. With no argument, the names of
15488 all @code{COMMON} blocks visible at the current program location are
15495 @cindex Pascal support in @value{GDBN}, limitations
15496 Debugging Pascal programs which use sets, subranges, file variables, or
15497 nested functions does not currently work. @value{GDBN} does not support
15498 entering expressions, printing values, or similar features using Pascal
15501 The Pascal-specific command @code{set print pascal_static-members}
15502 controls whether static members of Pascal objects are displayed.
15503 @xref{Print Settings, pascal_static-members}.
15508 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15509 Programming Language}. Type- and value-printing, and expression
15510 parsing, are reasonably complete. However, there are a few
15511 peculiarities and holes to be aware of.
15515 Linespecs (@pxref{Specify Location}) are never relative to the current
15516 crate. Instead, they act as if there were a global namespace of
15517 crates, somewhat similar to the way @code{extern crate} behaves.
15519 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15520 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15521 to set a breakpoint in a function named @samp{f} in a crate named
15524 As a consequence of this approach, linespecs also cannot refer to
15525 items using @samp{self::} or @samp{super::}.
15528 Because @value{GDBN} implements Rust name-lookup semantics in
15529 expressions, it will sometimes prepend the current crate to a name.
15530 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15531 @samp{K}, then @code{print ::x::y} will try to find the symbol
15534 However, since it is useful to be able to refer to other crates when
15535 debugging, @value{GDBN} provides the @code{extern} extension to
15536 circumvent this. To use the extension, just put @code{extern} before
15537 a path expression to refer to the otherwise unavailable ``global''
15540 In the above example, if you wanted to refer to the symbol @samp{y} in
15541 the crate @samp{x}, you would use @code{print extern x::y}.
15544 The Rust expression evaluator does not support ``statement-like''
15545 expressions such as @code{if} or @code{match}, or lambda expressions.
15548 Tuple expressions are not implemented.
15551 The Rust expression evaluator does not currently implement the
15552 @code{Drop} trait. Objects that may be created by the evaluator will
15553 never be destroyed.
15556 @value{GDBN} does not implement type inference for generics. In order
15557 to call generic functions or otherwise refer to generic items, you
15558 will have to specify the type parameters manually.
15561 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15562 cases this does not cause any problems. However, in an expression
15563 context, completing a generic function name will give syntactically
15564 invalid results. This happens because Rust requires the @samp{::}
15565 operator between the function name and its generic arguments. For
15566 example, @value{GDBN} might provide a completion like
15567 @code{crate::f<u32>}, where the parser would require
15568 @code{crate::f::<u32>}.
15571 As of this writing, the Rust compiler (version 1.8) has a few holes in
15572 the debugging information it generates. These holes prevent certain
15573 features from being implemented by @value{GDBN}:
15577 Method calls cannot be made via traits.
15580 Operator overloading is not implemented.
15583 When debugging in a monomorphized function, you cannot use the generic
15587 The type @code{Self} is not available.
15590 @code{use} statements are not available, so some names may not be
15591 available in the crate.
15596 @subsection Modula-2
15598 @cindex Modula-2, @value{GDBN} support
15600 The extensions made to @value{GDBN} to support Modula-2 only support
15601 output from the @sc{gnu} Modula-2 compiler (which is currently being
15602 developed). Other Modula-2 compilers are not currently supported, and
15603 attempting to debug executables produced by them is most likely
15604 to give an error as @value{GDBN} reads in the executable's symbol
15607 @cindex expressions in Modula-2
15609 * M2 Operators:: Built-in operators
15610 * Built-In Func/Proc:: Built-in functions and procedures
15611 * M2 Constants:: Modula-2 constants
15612 * M2 Types:: Modula-2 types
15613 * M2 Defaults:: Default settings for Modula-2
15614 * Deviations:: Deviations from standard Modula-2
15615 * M2 Checks:: Modula-2 type and range checks
15616 * M2 Scope:: The scope operators @code{::} and @code{.}
15617 * GDB/M2:: @value{GDBN} and Modula-2
15621 @subsubsection Operators
15622 @cindex Modula-2 operators
15624 Operators must be defined on values of specific types. For instance,
15625 @code{+} is defined on numbers, but not on structures. Operators are
15626 often defined on groups of types. For the purposes of Modula-2, the
15627 following definitions hold:
15632 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15636 @emph{Character types} consist of @code{CHAR} and its subranges.
15639 @emph{Floating-point types} consist of @code{REAL}.
15642 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15646 @emph{Scalar types} consist of all of the above.
15649 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15652 @emph{Boolean types} consist of @code{BOOLEAN}.
15656 The following operators are supported, and appear in order of
15657 increasing precedence:
15661 Function argument or array index separator.
15664 Assignment. The value of @var{var} @code{:=} @var{value} is
15668 Less than, greater than on integral, floating-point, or enumerated
15672 Less than or equal to, greater than or equal to
15673 on integral, floating-point and enumerated types, or set inclusion on
15674 set types. Same precedence as @code{<}.
15676 @item =@r{, }<>@r{, }#
15677 Equality and two ways of expressing inequality, valid on scalar types.
15678 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15679 available for inequality, since @code{#} conflicts with the script
15683 Set membership. Defined on set types and the types of their members.
15684 Same precedence as @code{<}.
15687 Boolean disjunction. Defined on boolean types.
15690 Boolean conjunction. Defined on boolean types.
15693 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15696 Addition and subtraction on integral and floating-point types, or union
15697 and difference on set types.
15700 Multiplication on integral and floating-point types, or set intersection
15704 Division on floating-point types, or symmetric set difference on set
15705 types. Same precedence as @code{*}.
15708 Integer division and remainder. Defined on integral types. Same
15709 precedence as @code{*}.
15712 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15715 Pointer dereferencing. Defined on pointer types.
15718 Boolean negation. Defined on boolean types. Same precedence as
15722 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15723 precedence as @code{^}.
15726 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15729 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15733 @value{GDBN} and Modula-2 scope operators.
15737 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15738 treats the use of the operator @code{IN}, or the use of operators
15739 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15740 @code{<=}, and @code{>=} on sets as an error.
15744 @node Built-In Func/Proc
15745 @subsubsection Built-in Functions and Procedures
15746 @cindex Modula-2 built-ins
15748 Modula-2 also makes available several built-in procedures and functions.
15749 In describing these, the following metavariables are used:
15754 represents an @code{ARRAY} variable.
15757 represents a @code{CHAR} constant or variable.
15760 represents a variable or constant of integral type.
15763 represents an identifier that belongs to a set. Generally used in the
15764 same function with the metavariable @var{s}. The type of @var{s} should
15765 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15768 represents a variable or constant of integral or floating-point type.
15771 represents a variable or constant of floating-point type.
15777 represents a variable.
15780 represents a variable or constant of one of many types. See the
15781 explanation of the function for details.
15784 All Modula-2 built-in procedures also return a result, described below.
15788 Returns the absolute value of @var{n}.
15791 If @var{c} is a lower case letter, it returns its upper case
15792 equivalent, otherwise it returns its argument.
15795 Returns the character whose ordinal value is @var{i}.
15798 Decrements the value in the variable @var{v} by one. Returns the new value.
15800 @item DEC(@var{v},@var{i})
15801 Decrements the value in the variable @var{v} by @var{i}. Returns the
15804 @item EXCL(@var{m},@var{s})
15805 Removes the element @var{m} from the set @var{s}. Returns the new
15808 @item FLOAT(@var{i})
15809 Returns the floating point equivalent of the integer @var{i}.
15811 @item HIGH(@var{a})
15812 Returns the index of the last member of @var{a}.
15815 Increments the value in the variable @var{v} by one. Returns the new value.
15817 @item INC(@var{v},@var{i})
15818 Increments the value in the variable @var{v} by @var{i}. Returns the
15821 @item INCL(@var{m},@var{s})
15822 Adds the element @var{m} to the set @var{s} if it is not already
15823 there. Returns the new set.
15826 Returns the maximum value of the type @var{t}.
15829 Returns the minimum value of the type @var{t}.
15832 Returns boolean TRUE if @var{i} is an odd number.
15835 Returns the ordinal value of its argument. For example, the ordinal
15836 value of a character is its @sc{ascii} value (on machines supporting
15837 the @sc{ascii} character set). The argument @var{x} must be of an
15838 ordered type, which include integral, character and enumerated types.
15840 @item SIZE(@var{x})
15841 Returns the size of its argument. The argument @var{x} can be a
15842 variable or a type.
15844 @item TRUNC(@var{r})
15845 Returns the integral part of @var{r}.
15847 @item TSIZE(@var{x})
15848 Returns the size of its argument. The argument @var{x} can be a
15849 variable or a type.
15851 @item VAL(@var{t},@var{i})
15852 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15856 @emph{Warning:} Sets and their operations are not yet supported, so
15857 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15861 @cindex Modula-2 constants
15863 @subsubsection Constants
15865 @value{GDBN} allows you to express the constants of Modula-2 in the following
15871 Integer constants are simply a sequence of digits. When used in an
15872 expression, a constant is interpreted to be type-compatible with the
15873 rest of the expression. Hexadecimal integers are specified by a
15874 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15877 Floating point constants appear as a sequence of digits, followed by a
15878 decimal point and another sequence of digits. An optional exponent can
15879 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15880 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15881 digits of the floating point constant must be valid decimal (base 10)
15885 Character constants consist of a single character enclosed by a pair of
15886 like quotes, either single (@code{'}) or double (@code{"}). They may
15887 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15888 followed by a @samp{C}.
15891 String constants consist of a sequence of characters enclosed by a
15892 pair of like quotes, either single (@code{'}) or double (@code{"}).
15893 Escape sequences in the style of C are also allowed. @xref{C
15894 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15898 Enumerated constants consist of an enumerated identifier.
15901 Boolean constants consist of the identifiers @code{TRUE} and
15905 Pointer constants consist of integral values only.
15908 Set constants are not yet supported.
15912 @subsubsection Modula-2 Types
15913 @cindex Modula-2 types
15915 Currently @value{GDBN} can print the following data types in Modula-2
15916 syntax: array types, record types, set types, pointer types, procedure
15917 types, enumerated types, subrange types and base types. You can also
15918 print the contents of variables declared using these type.
15919 This section gives a number of simple source code examples together with
15920 sample @value{GDBN} sessions.
15922 The first example contains the following section of code:
15931 and you can request @value{GDBN} to interrogate the type and value of
15932 @code{r} and @code{s}.
15935 (@value{GDBP}) print s
15937 (@value{GDBP}) ptype s
15939 (@value{GDBP}) print r
15941 (@value{GDBP}) ptype r
15946 Likewise if your source code declares @code{s} as:
15950 s: SET ['A'..'Z'] ;
15954 then you may query the type of @code{s} by:
15957 (@value{GDBP}) ptype s
15958 type = SET ['A'..'Z']
15962 Note that at present you cannot interactively manipulate set
15963 expressions using the debugger.
15965 The following example shows how you might declare an array in Modula-2
15966 and how you can interact with @value{GDBN} to print its type and contents:
15970 s: ARRAY [-10..10] OF CHAR ;
15974 (@value{GDBP}) ptype s
15975 ARRAY [-10..10] OF CHAR
15978 Note that the array handling is not yet complete and although the type
15979 is printed correctly, expression handling still assumes that all
15980 arrays have a lower bound of zero and not @code{-10} as in the example
15983 Here are some more type related Modula-2 examples:
15987 colour = (blue, red, yellow, green) ;
15988 t = [blue..yellow] ;
15996 The @value{GDBN} interaction shows how you can query the data type
15997 and value of a variable.
16000 (@value{GDBP}) print s
16002 (@value{GDBP}) ptype t
16003 type = [blue..yellow]
16007 In this example a Modula-2 array is declared and its contents
16008 displayed. Observe that the contents are written in the same way as
16009 their @code{C} counterparts.
16013 s: ARRAY [1..5] OF CARDINAL ;
16019 (@value{GDBP}) print s
16020 $1 = @{1, 0, 0, 0, 0@}
16021 (@value{GDBP}) ptype s
16022 type = ARRAY [1..5] OF CARDINAL
16025 The Modula-2 language interface to @value{GDBN} also understands
16026 pointer types as shown in this example:
16030 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16037 and you can request that @value{GDBN} describes the type of @code{s}.
16040 (@value{GDBP}) ptype s
16041 type = POINTER TO ARRAY [1..5] OF CARDINAL
16044 @value{GDBN} handles compound types as we can see in this example.
16045 Here we combine array types, record types, pointer types and subrange
16056 myarray = ARRAY myrange OF CARDINAL ;
16057 myrange = [-2..2] ;
16059 s: POINTER TO ARRAY myrange OF foo ;
16063 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16067 (@value{GDBP}) ptype s
16068 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16071 f3 : ARRAY [-2..2] OF CARDINAL;
16076 @subsubsection Modula-2 Defaults
16077 @cindex Modula-2 defaults
16079 If type and range checking are set automatically by @value{GDBN}, they
16080 both default to @code{on} whenever the working language changes to
16081 Modula-2. This happens regardless of whether you or @value{GDBN}
16082 selected the working language.
16084 If you allow @value{GDBN} to set the language automatically, then entering
16085 code compiled from a file whose name ends with @file{.mod} sets the
16086 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16087 Infer the Source Language}, for further details.
16090 @subsubsection Deviations from Standard Modula-2
16091 @cindex Modula-2, deviations from
16093 A few changes have been made to make Modula-2 programs easier to debug.
16094 This is done primarily via loosening its type strictness:
16098 Unlike in standard Modula-2, pointer constants can be formed by
16099 integers. This allows you to modify pointer variables during
16100 debugging. (In standard Modula-2, the actual address contained in a
16101 pointer variable is hidden from you; it can only be modified
16102 through direct assignment to another pointer variable or expression that
16103 returned a pointer.)
16106 C escape sequences can be used in strings and characters to represent
16107 non-printable characters. @value{GDBN} prints out strings with these
16108 escape sequences embedded. Single non-printable characters are
16109 printed using the @samp{CHR(@var{nnn})} format.
16112 The assignment operator (@code{:=}) returns the value of its right-hand
16116 All built-in procedures both modify @emph{and} return their argument.
16120 @subsubsection Modula-2 Type and Range Checks
16121 @cindex Modula-2 checks
16124 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16127 @c FIXME remove warning when type/range checks added
16129 @value{GDBN} considers two Modula-2 variables type equivalent if:
16133 They are of types that have been declared equivalent via a @code{TYPE
16134 @var{t1} = @var{t2}} statement
16137 They have been declared on the same line. (Note: This is true of the
16138 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16141 As long as type checking is enabled, any attempt to combine variables
16142 whose types are not equivalent is an error.
16144 Range checking is done on all mathematical operations, assignment, array
16145 index bounds, and all built-in functions and procedures.
16148 @subsubsection The Scope Operators @code{::} and @code{.}
16150 @cindex @code{.}, Modula-2 scope operator
16151 @cindex colon, doubled as scope operator
16153 @vindex colon-colon@r{, in Modula-2}
16154 @c Info cannot handle :: but TeX can.
16157 @vindex ::@r{, in Modula-2}
16160 There are a few subtle differences between the Modula-2 scope operator
16161 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16166 @var{module} . @var{id}
16167 @var{scope} :: @var{id}
16171 where @var{scope} is the name of a module or a procedure,
16172 @var{module} the name of a module, and @var{id} is any declared
16173 identifier within your program, except another module.
16175 Using the @code{::} operator makes @value{GDBN} search the scope
16176 specified by @var{scope} for the identifier @var{id}. If it is not
16177 found in the specified scope, then @value{GDBN} searches all scopes
16178 enclosing the one specified by @var{scope}.
16180 Using the @code{.} operator makes @value{GDBN} search the current scope for
16181 the identifier specified by @var{id} that was imported from the
16182 definition module specified by @var{module}. With this operator, it is
16183 an error if the identifier @var{id} was not imported from definition
16184 module @var{module}, or if @var{id} is not an identifier in
16188 @subsubsection @value{GDBN} and Modula-2
16190 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16191 Five subcommands of @code{set print} and @code{show print} apply
16192 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16193 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16194 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16195 analogue in Modula-2.
16197 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16198 with any language, is not useful with Modula-2. Its
16199 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16200 created in Modula-2 as they can in C or C@t{++}. However, because an
16201 address can be specified by an integral constant, the construct
16202 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16204 @cindex @code{#} in Modula-2
16205 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16206 interpreted as the beginning of a comment. Use @code{<>} instead.
16212 The extensions made to @value{GDBN} for Ada only support
16213 output from the @sc{gnu} Ada (GNAT) compiler.
16214 Other Ada compilers are not currently supported, and
16215 attempting to debug executables produced by them is most likely
16219 @cindex expressions in Ada
16221 * Ada Mode Intro:: General remarks on the Ada syntax
16222 and semantics supported by Ada mode
16224 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16225 * Additions to Ada:: Extensions of the Ada expression syntax.
16226 * Overloading support for Ada:: Support for expressions involving overloaded
16228 * Stopping Before Main Program:: Debugging the program during elaboration.
16229 * Ada Exceptions:: Ada Exceptions
16230 * Ada Tasks:: Listing and setting breakpoints in tasks.
16231 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16232 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16234 * Ada Glitches:: Known peculiarities of Ada mode.
16237 @node Ada Mode Intro
16238 @subsubsection Introduction
16239 @cindex Ada mode, general
16241 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16242 syntax, with some extensions.
16243 The philosophy behind the design of this subset is
16247 That @value{GDBN} should provide basic literals and access to operations for
16248 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16249 leaving more sophisticated computations to subprograms written into the
16250 program (which therefore may be called from @value{GDBN}).
16253 That type safety and strict adherence to Ada language restrictions
16254 are not particularly important to the @value{GDBN} user.
16257 That brevity is important to the @value{GDBN} user.
16260 Thus, for brevity, the debugger acts as if all names declared in
16261 user-written packages are directly visible, even if they are not visible
16262 according to Ada rules, thus making it unnecessary to fully qualify most
16263 names with their packages, regardless of context. Where this causes
16264 ambiguity, @value{GDBN} asks the user's intent.
16266 The debugger will start in Ada mode if it detects an Ada main program.
16267 As for other languages, it will enter Ada mode when stopped in a program that
16268 was translated from an Ada source file.
16270 While in Ada mode, you may use `@t{--}' for comments. This is useful
16271 mostly for documenting command files. The standard @value{GDBN} comment
16272 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16273 middle (to allow based literals).
16275 @node Omissions from Ada
16276 @subsubsection Omissions from Ada
16277 @cindex Ada, omissions from
16279 Here are the notable omissions from the subset:
16283 Only a subset of the attributes are supported:
16287 @t{'First}, @t{'Last}, and @t{'Length}
16288 on array objects (not on types and subtypes).
16291 @t{'Min} and @t{'Max}.
16294 @t{'Pos} and @t{'Val}.
16300 @t{'Range} on array objects (not subtypes), but only as the right
16301 operand of the membership (@code{in}) operator.
16304 @t{'Access}, @t{'Unchecked_Access}, and
16305 @t{'Unrestricted_Access} (a GNAT extension).
16313 @code{Characters.Latin_1} are not available and
16314 concatenation is not implemented. Thus, escape characters in strings are
16315 not currently available.
16318 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16319 equality of representations. They will generally work correctly
16320 for strings and arrays whose elements have integer or enumeration types.
16321 They may not work correctly for arrays whose element
16322 types have user-defined equality, for arrays of real values
16323 (in particular, IEEE-conformant floating point, because of negative
16324 zeroes and NaNs), and for arrays whose elements contain unused bits with
16325 indeterminate values.
16328 The other component-by-component array operations (@code{and}, @code{or},
16329 @code{xor}, @code{not}, and relational tests other than equality)
16330 are not implemented.
16333 @cindex array aggregates (Ada)
16334 @cindex record aggregates (Ada)
16335 @cindex aggregates (Ada)
16336 There is limited support for array and record aggregates. They are
16337 permitted only on the right sides of assignments, as in these examples:
16340 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16341 (@value{GDBP}) set An_Array := (1, others => 0)
16342 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16343 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16344 (@value{GDBP}) set A_Record := (1, "Peter", True);
16345 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16349 discriminant's value by assigning an aggregate has an
16350 undefined effect if that discriminant is used within the record.
16351 However, you can first modify discriminants by directly assigning to
16352 them (which normally would not be allowed in Ada), and then performing an
16353 aggregate assignment. For example, given a variable @code{A_Rec}
16354 declared to have a type such as:
16357 type Rec (Len : Small_Integer := 0) is record
16359 Vals : IntArray (1 .. Len);
16363 you can assign a value with a different size of @code{Vals} with two
16367 (@value{GDBP}) set A_Rec.Len := 4
16368 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16371 As this example also illustrates, @value{GDBN} is very loose about the usual
16372 rules concerning aggregates. You may leave out some of the
16373 components of an array or record aggregate (such as the @code{Len}
16374 component in the assignment to @code{A_Rec} above); they will retain their
16375 original values upon assignment. You may freely use dynamic values as
16376 indices in component associations. You may even use overlapping or
16377 redundant component associations, although which component values are
16378 assigned in such cases is not defined.
16381 Calls to dispatching subprograms are not implemented.
16384 The overloading algorithm is much more limited (i.e., less selective)
16385 than that of real Ada. It makes only limited use of the context in
16386 which a subexpression appears to resolve its meaning, and it is much
16387 looser in its rules for allowing type matches. As a result, some
16388 function calls will be ambiguous, and the user will be asked to choose
16389 the proper resolution.
16392 The @code{new} operator is not implemented.
16395 Entry calls are not implemented.
16398 Aside from printing, arithmetic operations on the native VAX floating-point
16399 formats are not supported.
16402 It is not possible to slice a packed array.
16405 The names @code{True} and @code{False}, when not part of a qualified name,
16406 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16408 Should your program
16409 redefine these names in a package or procedure (at best a dubious practice),
16410 you will have to use fully qualified names to access their new definitions.
16413 @node Additions to Ada
16414 @subsubsection Additions to Ada
16415 @cindex Ada, deviations from
16417 As it does for other languages, @value{GDBN} makes certain generic
16418 extensions to Ada (@pxref{Expressions}):
16422 If the expression @var{E} is a variable residing in memory (typically
16423 a local variable or array element) and @var{N} is a positive integer,
16424 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16425 @var{N}-1 adjacent variables following it in memory as an array. In
16426 Ada, this operator is generally not necessary, since its prime use is
16427 in displaying parts of an array, and slicing will usually do this in
16428 Ada. However, there are occasional uses when debugging programs in
16429 which certain debugging information has been optimized away.
16432 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16433 appears in function or file @var{B}.'' When @var{B} is a file name,
16434 you must typically surround it in single quotes.
16437 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16438 @var{type} that appears at address @var{addr}.''
16441 A name starting with @samp{$} is a convenience variable
16442 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16445 In addition, @value{GDBN} provides a few other shortcuts and outright
16446 additions specific to Ada:
16450 The assignment statement is allowed as an expression, returning
16451 its right-hand operand as its value. Thus, you may enter
16454 (@value{GDBP}) set x := y + 3
16455 (@value{GDBP}) print A(tmp := y + 1)
16459 The semicolon is allowed as an ``operator,'' returning as its value
16460 the value of its right-hand operand.
16461 This allows, for example,
16462 complex conditional breaks:
16465 (@value{GDBP}) break f
16466 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16470 Rather than use catenation and symbolic character names to introduce special
16471 characters into strings, one may instead use a special bracket notation,
16472 which is also used to print strings. A sequence of characters of the form
16473 @samp{["@var{XX}"]} within a string or character literal denotes the
16474 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16475 sequence of characters @samp{["""]} also denotes a single quotation mark
16476 in strings. For example,
16478 "One line.["0a"]Next line.["0a"]"
16481 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16485 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16486 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16490 (@value{GDBP}) print 'max(x, y)
16494 When printing arrays, @value{GDBN} uses positional notation when the
16495 array has a lower bound of 1, and uses a modified named notation otherwise.
16496 For example, a one-dimensional array of three integers with a lower bound
16497 of 3 might print as
16504 That is, in contrast to valid Ada, only the first component has a @code{=>}
16508 You may abbreviate attributes in expressions with any unique,
16509 multi-character subsequence of
16510 their names (an exact match gets preference).
16511 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16512 in place of @t{a'length}.
16515 @cindex quoting Ada internal identifiers
16516 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16517 to lower case. The GNAT compiler uses upper-case characters for
16518 some of its internal identifiers, which are normally of no interest to users.
16519 For the rare occasions when you actually have to look at them,
16520 enclose them in angle brackets to avoid the lower-case mapping.
16523 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16527 Printing an object of class-wide type or dereferencing an
16528 access-to-class-wide value will display all the components of the object's
16529 specific type (as indicated by its run-time tag). Likewise, component
16530 selection on such a value will operate on the specific type of the
16535 @node Overloading support for Ada
16536 @subsubsection Overloading support for Ada
16537 @cindex overloading, Ada
16539 The debugger supports limited overloading. Given a subprogram call in which
16540 the function symbol has multiple definitions, it will use the number of
16541 actual parameters and some information about their types to attempt to narrow
16542 the set of definitions. It also makes very limited use of context, preferring
16543 procedures to functions in the context of the @code{call} command, and
16544 functions to procedures elsewhere.
16546 If, after narrowing, the set of matching definitions still contains more than
16547 one definition, @value{GDBN} will display a menu to query which one it should
16551 (@value{GDBP}) print f(1)
16552 Multiple matches for f
16554 [1] foo.f (integer) return boolean at foo.adb:23
16555 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16559 In this case, just select one menu entry either to cancel expression evaluation
16560 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16561 instance (type the corresponding number and press @key{RET}).
16563 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16568 @kindex set ada print-signatures
16569 @item set ada print-signatures
16570 Control whether parameter types and return types are displayed in overloads
16571 selection menus. It is @code{on} by default.
16572 @xref{Overloading support for Ada}.
16574 @kindex show ada print-signatures
16575 @item show ada print-signatures
16576 Show the current setting for displaying parameter types and return types in
16577 overloads selection menu.
16578 @xref{Overloading support for Ada}.
16582 @node Stopping Before Main Program
16583 @subsubsection Stopping at the Very Beginning
16585 @cindex breakpointing Ada elaboration code
16586 It is sometimes necessary to debug the program during elaboration, and
16587 before reaching the main procedure.
16588 As defined in the Ada Reference
16589 Manual, the elaboration code is invoked from a procedure called
16590 @code{adainit}. To run your program up to the beginning of
16591 elaboration, simply use the following two commands:
16592 @code{tbreak adainit} and @code{run}.
16594 @node Ada Exceptions
16595 @subsubsection Ada Exceptions
16597 A command is provided to list all Ada exceptions:
16600 @kindex info exceptions
16601 @item info exceptions
16602 @itemx info exceptions @var{regexp}
16603 The @code{info exceptions} command allows you to list all Ada exceptions
16604 defined within the program being debugged, as well as their addresses.
16605 With a regular expression, @var{regexp}, as argument, only those exceptions
16606 whose names match @var{regexp} are listed.
16609 Below is a small example, showing how the command can be used, first
16610 without argument, and next with a regular expression passed as an
16614 (@value{GDBP}) info exceptions
16615 All defined Ada exceptions:
16616 constraint_error: 0x613da0
16617 program_error: 0x613d20
16618 storage_error: 0x613ce0
16619 tasking_error: 0x613ca0
16620 const.aint_global_e: 0x613b00
16621 (@value{GDBP}) info exceptions const.aint
16622 All Ada exceptions matching regular expression "const.aint":
16623 constraint_error: 0x613da0
16624 const.aint_global_e: 0x613b00
16627 It is also possible to ask @value{GDBN} to stop your program's execution
16628 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16631 @subsubsection Extensions for Ada Tasks
16632 @cindex Ada, tasking
16634 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16635 @value{GDBN} provides the following task-related commands:
16640 This command shows a list of current Ada tasks, as in the following example:
16647 (@value{GDBP}) info tasks
16648 ID TID P-ID Pri State Name
16649 1 8088000 0 15 Child Activation Wait main_task
16650 2 80a4000 1 15 Accept Statement b
16651 3 809a800 1 15 Child Activation Wait a
16652 * 4 80ae800 3 15 Runnable c
16657 In this listing, the asterisk before the last task indicates it to be the
16658 task currently being inspected.
16662 Represents @value{GDBN}'s internal task number.
16668 The parent's task ID (@value{GDBN}'s internal task number).
16671 The base priority of the task.
16674 Current state of the task.
16678 The task has been created but has not been activated. It cannot be
16682 The task is not blocked for any reason known to Ada. (It may be waiting
16683 for a mutex, though.) It is conceptually "executing" in normal mode.
16686 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16687 that were waiting on terminate alternatives have been awakened and have
16688 terminated themselves.
16690 @item Child Activation Wait
16691 The task is waiting for created tasks to complete activation.
16693 @item Accept Statement
16694 The task is waiting on an accept or selective wait statement.
16696 @item Waiting on entry call
16697 The task is waiting on an entry call.
16699 @item Async Select Wait
16700 The task is waiting to start the abortable part of an asynchronous
16704 The task is waiting on a select statement with only a delay
16707 @item Child Termination Wait
16708 The task is sleeping having completed a master within itself, and is
16709 waiting for the tasks dependent on that master to become terminated or
16710 waiting on a terminate Phase.
16712 @item Wait Child in Term Alt
16713 The task is sleeping waiting for tasks on terminate alternatives to
16714 finish terminating.
16716 @item Accepting RV with @var{taskno}
16717 The task is accepting a rendez-vous with the task @var{taskno}.
16721 Name of the task in the program.
16725 @kindex info task @var{taskno}
16726 @item info task @var{taskno}
16727 This command shows detailled informations on the specified task, as in
16728 the following example:
16733 (@value{GDBP}) info tasks
16734 ID TID P-ID Pri State Name
16735 1 8077880 0 15 Child Activation Wait main_task
16736 * 2 807c468 1 15 Runnable task_1
16737 (@value{GDBP}) info task 2
16738 Ada Task: 0x807c468
16741 Parent: 1 (main_task)
16747 @kindex task@r{ (Ada)}
16748 @cindex current Ada task ID
16749 This command prints the ID of the current task.
16755 (@value{GDBP}) info tasks
16756 ID TID P-ID Pri State Name
16757 1 8077870 0 15 Child Activation Wait main_task
16758 * 2 807c458 1 15 Runnable t
16759 (@value{GDBP}) task
16760 [Current task is 2]
16763 @item task @var{taskno}
16764 @cindex Ada task switching
16765 This command is like the @code{thread @var{thread-id}}
16766 command (@pxref{Threads}). It switches the context of debugging
16767 from the current task to the given task.
16773 (@value{GDBP}) info tasks
16774 ID TID P-ID Pri State Name
16775 1 8077870 0 15 Child Activation Wait main_task
16776 * 2 807c458 1 15 Runnable t
16777 (@value{GDBP}) task 1
16778 [Switching to task 1]
16779 #0 0x8067726 in pthread_cond_wait ()
16781 #0 0x8067726 in pthread_cond_wait ()
16782 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16783 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16784 #3 0x806153e in system.tasking.stages.activate_tasks ()
16785 #4 0x804aacc in un () at un.adb:5
16788 @item break @var{location} task @var{taskno}
16789 @itemx break @var{location} task @var{taskno} if @dots{}
16790 @cindex breakpoints and tasks, in Ada
16791 @cindex task breakpoints, in Ada
16792 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16793 These commands are like the @code{break @dots{} thread @dots{}}
16794 command (@pxref{Thread Stops}). The
16795 @var{location} argument specifies source lines, as described
16796 in @ref{Specify Location}.
16798 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16799 to specify that you only want @value{GDBN} to stop the program when a
16800 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16801 numeric task identifiers assigned by @value{GDBN}, shown in the first
16802 column of the @samp{info tasks} display.
16804 If you do not specify @samp{task @var{taskno}} when you set a
16805 breakpoint, the breakpoint applies to @emph{all} tasks of your
16808 You can use the @code{task} qualifier on conditional breakpoints as
16809 well; in this case, place @samp{task @var{taskno}} before the
16810 breakpoint condition (before the @code{if}).
16818 (@value{GDBP}) info tasks
16819 ID TID P-ID Pri State Name
16820 1 140022020 0 15 Child Activation Wait main_task
16821 2 140045060 1 15 Accept/Select Wait t2
16822 3 140044840 1 15 Runnable t1
16823 * 4 140056040 1 15 Runnable t3
16824 (@value{GDBP}) b 15 task 2
16825 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16826 (@value{GDBP}) cont
16831 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16833 (@value{GDBP}) info tasks
16834 ID TID P-ID Pri State Name
16835 1 140022020 0 15 Child Activation Wait main_task
16836 * 2 140045060 1 15 Runnable t2
16837 3 140044840 1 15 Runnable t1
16838 4 140056040 1 15 Delay Sleep t3
16842 @node Ada Tasks and Core Files
16843 @subsubsection Tasking Support when Debugging Core Files
16844 @cindex Ada tasking and core file debugging
16846 When inspecting a core file, as opposed to debugging a live program,
16847 tasking support may be limited or even unavailable, depending on
16848 the platform being used.
16849 For instance, on x86-linux, the list of tasks is available, but task
16850 switching is not supported.
16852 On certain platforms, the debugger needs to perform some
16853 memory writes in order to provide Ada tasking support. When inspecting
16854 a core file, this means that the core file must be opened with read-write
16855 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16856 Under these circumstances, you should make a backup copy of the core
16857 file before inspecting it with @value{GDBN}.
16859 @node Ravenscar Profile
16860 @subsubsection Tasking Support when using the Ravenscar Profile
16861 @cindex Ravenscar Profile
16863 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16864 specifically designed for systems with safety-critical real-time
16868 @kindex set ravenscar task-switching on
16869 @cindex task switching with program using Ravenscar Profile
16870 @item set ravenscar task-switching on
16871 Allows task switching when debugging a program that uses the Ravenscar
16872 Profile. This is the default.
16874 @kindex set ravenscar task-switching off
16875 @item set ravenscar task-switching off
16876 Turn off task switching when debugging a program that uses the Ravenscar
16877 Profile. This is mostly intended to disable the code that adds support
16878 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16879 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16880 To be effective, this command should be run before the program is started.
16882 @kindex show ravenscar task-switching
16883 @item show ravenscar task-switching
16884 Show whether it is possible to switch from task to task in a program
16885 using the Ravenscar Profile.
16890 @subsubsection Known Peculiarities of Ada Mode
16891 @cindex Ada, problems
16893 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16894 we know of several problems with and limitations of Ada mode in
16896 some of which will be fixed with planned future releases of the debugger
16897 and the GNU Ada compiler.
16901 Static constants that the compiler chooses not to materialize as objects in
16902 storage are invisible to the debugger.
16905 Named parameter associations in function argument lists are ignored (the
16906 argument lists are treated as positional).
16909 Many useful library packages are currently invisible to the debugger.
16912 Fixed-point arithmetic, conversions, input, and output is carried out using
16913 floating-point arithmetic, and may give results that only approximate those on
16917 The GNAT compiler never generates the prefix @code{Standard} for any of
16918 the standard symbols defined by the Ada language. @value{GDBN} knows about
16919 this: it will strip the prefix from names when you use it, and will never
16920 look for a name you have so qualified among local symbols, nor match against
16921 symbols in other packages or subprograms. If you have
16922 defined entities anywhere in your program other than parameters and
16923 local variables whose simple names match names in @code{Standard},
16924 GNAT's lack of qualification here can cause confusion. When this happens,
16925 you can usually resolve the confusion
16926 by qualifying the problematic names with package
16927 @code{Standard} explicitly.
16930 Older versions of the compiler sometimes generate erroneous debugging
16931 information, resulting in the debugger incorrectly printing the value
16932 of affected entities. In some cases, the debugger is able to work
16933 around an issue automatically. In other cases, the debugger is able
16934 to work around the issue, but the work-around has to be specifically
16937 @kindex set ada trust-PAD-over-XVS
16938 @kindex show ada trust-PAD-over-XVS
16941 @item set ada trust-PAD-over-XVS on
16942 Configure GDB to strictly follow the GNAT encoding when computing the
16943 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16944 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16945 a complete description of the encoding used by the GNAT compiler).
16946 This is the default.
16948 @item set ada trust-PAD-over-XVS off
16949 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16950 sometimes prints the wrong value for certain entities, changing @code{ada
16951 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16952 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16953 @code{off}, but this incurs a slight performance penalty, so it is
16954 recommended to leave this setting to @code{on} unless necessary.
16958 @cindex GNAT descriptive types
16959 @cindex GNAT encoding
16960 Internally, the debugger also relies on the compiler following a number
16961 of conventions known as the @samp{GNAT Encoding}, all documented in
16962 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16963 how the debugging information should be generated for certain types.
16964 In particular, this convention makes use of @dfn{descriptive types},
16965 which are artificial types generated purely to help the debugger.
16967 These encodings were defined at a time when the debugging information
16968 format used was not powerful enough to describe some of the more complex
16969 types available in Ada. Since DWARF allows us to express nearly all
16970 Ada features, the long-term goal is to slowly replace these descriptive
16971 types by their pure DWARF equivalent. To facilitate that transition,
16972 a new maintenance option is available to force the debugger to ignore
16973 those descriptive types. It allows the user to quickly evaluate how
16974 well @value{GDBN} works without them.
16978 @kindex maint ada set ignore-descriptive-types
16979 @item maintenance ada set ignore-descriptive-types [on|off]
16980 Control whether the debugger should ignore descriptive types.
16981 The default is not to ignore descriptives types (@code{off}).
16983 @kindex maint ada show ignore-descriptive-types
16984 @item maintenance ada show ignore-descriptive-types
16985 Show if descriptive types are ignored by @value{GDBN}.
16989 @node Unsupported Languages
16990 @section Unsupported Languages
16992 @cindex unsupported languages
16993 @cindex minimal language
16994 In addition to the other fully-supported programming languages,
16995 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16996 It does not represent a real programming language, but provides a set
16997 of capabilities close to what the C or assembly languages provide.
16998 This should allow most simple operations to be performed while debugging
16999 an application that uses a language currently not supported by @value{GDBN}.
17001 If the language is set to @code{auto}, @value{GDBN} will automatically
17002 select this language if the current frame corresponds to an unsupported
17006 @chapter Examining the Symbol Table
17008 The commands described in this chapter allow you to inquire about the
17009 symbols (names of variables, functions and types) defined in your
17010 program. This information is inherent in the text of your program and
17011 does not change as your program executes. @value{GDBN} finds it in your
17012 program's symbol table, in the file indicated when you started @value{GDBN}
17013 (@pxref{File Options, ,Choosing Files}), or by one of the
17014 file-management commands (@pxref{Files, ,Commands to Specify Files}).
17016 @cindex symbol names
17017 @cindex names of symbols
17018 @cindex quoting names
17019 @anchor{quoting names}
17020 Occasionally, you may need to refer to symbols that contain unusual
17021 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17022 most frequent case is in referring to static variables in other
17023 source files (@pxref{Variables,,Program Variables}). File names
17024 are recorded in object files as debugging symbols, but @value{GDBN} would
17025 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17026 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17027 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17034 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17037 @cindex case-insensitive symbol names
17038 @cindex case sensitivity in symbol names
17039 @kindex set case-sensitive
17040 @item set case-sensitive on
17041 @itemx set case-sensitive off
17042 @itemx set case-sensitive auto
17043 Normally, when @value{GDBN} looks up symbols, it matches their names
17044 with case sensitivity determined by the current source language.
17045 Occasionally, you may wish to control that. The command @code{set
17046 case-sensitive} lets you do that by specifying @code{on} for
17047 case-sensitive matches or @code{off} for case-insensitive ones. If
17048 you specify @code{auto}, case sensitivity is reset to the default
17049 suitable for the source language. The default is case-sensitive
17050 matches for all languages except for Fortran, for which the default is
17051 case-insensitive matches.
17053 @kindex show case-sensitive
17054 @item show case-sensitive
17055 This command shows the current setting of case sensitivity for symbols
17058 @kindex set print type methods
17059 @item set print type methods
17060 @itemx set print type methods on
17061 @itemx set print type methods off
17062 Normally, when @value{GDBN} prints a class, it displays any methods
17063 declared in that class. You can control this behavior either by
17064 passing the appropriate flag to @code{ptype}, or using @command{set
17065 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17066 display the methods; this is the default. Specifying @code{off} will
17067 cause @value{GDBN} to omit the methods.
17069 @kindex show print type methods
17070 @item show print type methods
17071 This command shows the current setting of method display when printing
17074 @kindex set print type nested-type-limit
17075 @item set print type nested-type-limit @var{limit}
17076 @itemx set print type nested-type-limit unlimited
17077 Set the limit of displayed nested types that the type printer will
17078 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
17079 nested definitions. By default, the type printer will not show any nested
17080 types defined in classes.
17082 @kindex show print type nested-type-limit
17083 @item show print type nested-type-limit
17084 This command shows the current display limit of nested types when
17087 @kindex set print type typedefs
17088 @item set print type typedefs
17089 @itemx set print type typedefs on
17090 @itemx set print type typedefs off
17092 Normally, when @value{GDBN} prints a class, it displays any typedefs
17093 defined in that class. You can control this behavior either by
17094 passing the appropriate flag to @code{ptype}, or using @command{set
17095 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17096 display the typedef definitions; this is the default. Specifying
17097 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17098 Note that this controls whether the typedef definition itself is
17099 printed, not whether typedef names are substituted when printing other
17102 @kindex show print type typedefs
17103 @item show print type typedefs
17104 This command shows the current setting of typedef display when
17107 @kindex info address
17108 @cindex address of a symbol
17109 @item info address @var{symbol}
17110 Describe where the data for @var{symbol} is stored. For a register
17111 variable, this says which register it is kept in. For a non-register
17112 local variable, this prints the stack-frame offset at which the variable
17115 Note the contrast with @samp{print &@var{symbol}}, which does not work
17116 at all for a register variable, and for a stack local variable prints
17117 the exact address of the current instantiation of the variable.
17119 @kindex info symbol
17120 @cindex symbol from address
17121 @cindex closest symbol and offset for an address
17122 @item info symbol @var{addr}
17123 Print the name of a symbol which is stored at the address @var{addr}.
17124 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17125 nearest symbol and an offset from it:
17128 (@value{GDBP}) info symbol 0x54320
17129 _initialize_vx + 396 in section .text
17133 This is the opposite of the @code{info address} command. You can use
17134 it to find out the name of a variable or a function given its address.
17136 For dynamically linked executables, the name of executable or shared
17137 library containing the symbol is also printed:
17140 (@value{GDBP}) info symbol 0x400225
17141 _start + 5 in section .text of /tmp/a.out
17142 (@value{GDBP}) info symbol 0x2aaaac2811cf
17143 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17148 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17149 Demangle @var{name}.
17150 If @var{language} is provided it is the name of the language to demangle
17151 @var{name} in. Otherwise @var{name} is demangled in the current language.
17153 The @samp{--} option specifies the end of options,
17154 and is useful when @var{name} begins with a dash.
17156 The parameter @code{demangle-style} specifies how to interpret the kind
17157 of mangling used. @xref{Print Settings}.
17160 @item whatis[/@var{flags}] [@var{arg}]
17161 Print the data type of @var{arg}, which can be either an expression
17162 or a name of a data type. With no argument, print the data type of
17163 @code{$}, the last value in the value history.
17165 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17166 is not actually evaluated, and any side-effecting operations (such as
17167 assignments or function calls) inside it do not take place.
17169 If @var{arg} is a variable or an expression, @code{whatis} prints its
17170 literal type as it is used in the source code. If the type was
17171 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17172 the data type underlying the @code{typedef}. If the type of the
17173 variable or the expression is a compound data type, such as
17174 @code{struct} or @code{class}, @code{whatis} never prints their
17175 fields or methods. It just prints the @code{struct}/@code{class}
17176 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17177 such a compound data type, use @code{ptype}.
17179 If @var{arg} is a type name that was defined using @code{typedef},
17180 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17181 Unrolling means that @code{whatis} will show the underlying type used
17182 in the @code{typedef} declaration of @var{arg}. However, if that
17183 underlying type is also a @code{typedef}, @code{whatis} will not
17186 For C code, the type names may also have the form @samp{class
17187 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17188 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17190 @var{flags} can be used to modify how the type is displayed.
17191 Available flags are:
17195 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17196 parameters and typedefs defined in a class when printing the class'
17197 members. The @code{/r} flag disables this.
17200 Do not print methods defined in the class.
17203 Print methods defined in the class. This is the default, but the flag
17204 exists in case you change the default with @command{set print type methods}.
17207 Do not print typedefs defined in the class. Note that this controls
17208 whether the typedef definition itself is printed, not whether typedef
17209 names are substituted when printing other types.
17212 Print typedefs defined in the class. This is the default, but the flag
17213 exists in case you change the default with @command{set print type typedefs}.
17217 @item ptype[/@var{flags}] [@var{arg}]
17218 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17219 detailed description of the type, instead of just the name of the type.
17220 @xref{Expressions, ,Expressions}.
17222 Contrary to @code{whatis}, @code{ptype} always unrolls any
17223 @code{typedef}s in its argument declaration, whether the argument is
17224 a variable, expression, or a data type. This means that @code{ptype}
17225 of a variable or an expression will not print literally its type as
17226 present in the source code---use @code{whatis} for that. @code{typedef}s at
17227 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17228 fields, methods and inner @code{class typedef}s of @code{struct}s,
17229 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17231 For example, for this variable declaration:
17234 typedef double real_t;
17235 struct complex @{ real_t real; double imag; @};
17236 typedef struct complex complex_t;
17238 real_t *real_pointer_var;
17242 the two commands give this output:
17246 (@value{GDBP}) whatis var
17248 (@value{GDBP}) ptype var
17249 type = struct complex @{
17253 (@value{GDBP}) whatis complex_t
17254 type = struct complex
17255 (@value{GDBP}) whatis struct complex
17256 type = struct complex
17257 (@value{GDBP}) ptype struct complex
17258 type = struct complex @{
17262 (@value{GDBP}) whatis real_pointer_var
17264 (@value{GDBP}) ptype real_pointer_var
17270 As with @code{whatis}, using @code{ptype} without an argument refers to
17271 the type of @code{$}, the last value in the value history.
17273 @cindex incomplete type
17274 Sometimes, programs use opaque data types or incomplete specifications
17275 of complex data structure. If the debug information included in the
17276 program does not allow @value{GDBN} to display a full declaration of
17277 the data type, it will say @samp{<incomplete type>}. For example,
17278 given these declarations:
17282 struct foo *fooptr;
17286 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17289 (@value{GDBP}) ptype foo
17290 $1 = <incomplete type>
17294 ``Incomplete type'' is C terminology for data types that are not
17295 completely specified.
17297 @cindex unknown type
17298 Othertimes, information about a variable's type is completely absent
17299 from the debug information included in the program. This most often
17300 happens when the program or library where the variable is defined
17301 includes no debug information at all. @value{GDBN} knows the variable
17302 exists from inspecting the linker/loader symbol table (e.g., the ELF
17303 dynamic symbol table), but such symbols do not contain type
17304 information. Inspecting the type of a (global) variable for which
17305 @value{GDBN} has no type information shows:
17308 (@value{GDBP}) ptype var
17309 type = <data variable, no debug info>
17312 @xref{Variables, no debug info variables}, for how to print the values
17316 @item info types @var{regexp}
17318 Print a brief description of all types whose names match the regular
17319 expression @var{regexp} (or all types in your program, if you supply
17320 no argument). Each complete typename is matched as though it were a
17321 complete line; thus, @samp{i type value} gives information on all
17322 types in your program whose names include the string @code{value}, but
17323 @samp{i type ^value$} gives information only on types whose complete
17324 name is @code{value}.
17326 This command differs from @code{ptype} in two ways: first, like
17327 @code{whatis}, it does not print a detailed description; second, it
17328 lists all source files where a type is defined.
17330 @kindex info type-printers
17331 @item info type-printers
17332 Versions of @value{GDBN} that ship with Python scripting enabled may
17333 have ``type printers'' available. When using @command{ptype} or
17334 @command{whatis}, these printers are consulted when the name of a type
17335 is needed. @xref{Type Printing API}, for more information on writing
17338 @code{info type-printers} displays all the available type printers.
17340 @kindex enable type-printer
17341 @kindex disable type-printer
17342 @item enable type-printer @var{name}@dots{}
17343 @item disable type-printer @var{name}@dots{}
17344 These commands can be used to enable or disable type printers.
17347 @cindex local variables
17348 @item info scope @var{location}
17349 List all the variables local to a particular scope. This command
17350 accepts a @var{location} argument---a function name, a source line, or
17351 an address preceded by a @samp{*}, and prints all the variables local
17352 to the scope defined by that location. (@xref{Specify Location}, for
17353 details about supported forms of @var{location}.) For example:
17356 (@value{GDBP}) @b{info scope command_line_handler}
17357 Scope for command_line_handler:
17358 Symbol rl is an argument at stack/frame offset 8, length 4.
17359 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17360 Symbol linelength is in static storage at address 0x150a1c, length 4.
17361 Symbol p is a local variable in register $esi, length 4.
17362 Symbol p1 is a local variable in register $ebx, length 4.
17363 Symbol nline is a local variable in register $edx, length 4.
17364 Symbol repeat is a local variable at frame offset -8, length 4.
17368 This command is especially useful for determining what data to collect
17369 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17372 @kindex info source
17374 Show information about the current source file---that is, the source file for
17375 the function containing the current point of execution:
17378 the name of the source file, and the directory containing it,
17380 the directory it was compiled in,
17382 its length, in lines,
17384 which programming language it is written in,
17386 if the debug information provides it, the program that compiled the file
17387 (which may include, e.g., the compiler version and command line arguments),
17389 whether the executable includes debugging information for that file, and
17390 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17392 whether the debugging information includes information about
17393 preprocessor macros.
17397 @kindex info sources
17399 Print the names of all source files in your program for which there is
17400 debugging information, organized into two lists: files whose symbols
17401 have already been read, and files whose symbols will be read when needed.
17403 @kindex info functions
17404 @item info functions
17405 Print the names and data types of all defined functions.
17407 @item info functions @var{regexp}
17408 Print the names and data types of all defined functions
17409 whose names contain a match for regular expression @var{regexp}.
17410 Thus, @samp{info fun step} finds all functions whose names
17411 include @code{step}; @samp{info fun ^step} finds those whose names
17412 start with @code{step}. If a function name contains characters
17413 that conflict with the regular expression language (e.g.@:
17414 @samp{operator*()}), they may be quoted with a backslash.
17416 @kindex info variables
17417 @item info variables
17418 Print the names and data types of all variables that are defined
17419 outside of functions (i.e.@: excluding local variables).
17421 @item info variables @var{regexp}
17422 Print the names and data types of all variables (except for local
17423 variables) whose names contain a match for regular expression
17426 @kindex info classes
17427 @cindex Objective-C, classes and selectors
17429 @itemx info classes @var{regexp}
17430 Display all Objective-C classes in your program, or
17431 (with the @var{regexp} argument) all those matching a particular regular
17434 @kindex info selectors
17435 @item info selectors
17436 @itemx info selectors @var{regexp}
17437 Display all Objective-C selectors in your program, or
17438 (with the @var{regexp} argument) all those matching a particular regular
17442 This was never implemented.
17443 @kindex info methods
17445 @itemx info methods @var{regexp}
17446 The @code{info methods} command permits the user to examine all defined
17447 methods within C@t{++} program, or (with the @var{regexp} argument) a
17448 specific set of methods found in the various C@t{++} classes. Many
17449 C@t{++} classes provide a large number of methods. Thus, the output
17450 from the @code{ptype} command can be overwhelming and hard to use. The
17451 @code{info-methods} command filters the methods, printing only those
17452 which match the regular-expression @var{regexp}.
17455 @cindex opaque data types
17456 @kindex set opaque-type-resolution
17457 @item set opaque-type-resolution on
17458 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17459 declared as a pointer to a @code{struct}, @code{class}, or
17460 @code{union}---for example, @code{struct MyType *}---that is used in one
17461 source file although the full declaration of @code{struct MyType} is in
17462 another source file. The default is on.
17464 A change in the setting of this subcommand will not take effect until
17465 the next time symbols for a file are loaded.
17467 @item set opaque-type-resolution off
17468 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17469 is printed as follows:
17471 @{<no data fields>@}
17474 @kindex show opaque-type-resolution
17475 @item show opaque-type-resolution
17476 Show whether opaque types are resolved or not.
17478 @kindex set print symbol-loading
17479 @cindex print messages when symbols are loaded
17480 @item set print symbol-loading
17481 @itemx set print symbol-loading full
17482 @itemx set print symbol-loading brief
17483 @itemx set print symbol-loading off
17484 The @code{set print symbol-loading} command allows you to control the
17485 printing of messages when @value{GDBN} loads symbol information.
17486 By default a message is printed for the executable and one for each
17487 shared library, and normally this is what you want. However, when
17488 debugging apps with large numbers of shared libraries these messages
17490 When set to @code{brief} a message is printed for each executable,
17491 and when @value{GDBN} loads a collection of shared libraries at once
17492 it will only print one message regardless of the number of shared
17493 libraries. When set to @code{off} no messages are printed.
17495 @kindex show print symbol-loading
17496 @item show print symbol-loading
17497 Show whether messages will be printed when a @value{GDBN} command
17498 entered from the keyboard causes symbol information to be loaded.
17500 @kindex maint print symbols
17501 @cindex symbol dump
17502 @kindex maint print psymbols
17503 @cindex partial symbol dump
17504 @kindex maint print msymbols
17505 @cindex minimal symbol dump
17506 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
17507 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17508 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17509 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17510 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17511 Write a dump of debugging symbol data into the file @var{filename} or
17512 the terminal if @var{filename} is unspecified.
17513 If @code{-objfile @var{objfile}} is specified, only dump symbols for
17515 If @code{-pc @var{address}} is specified, only dump symbols for the file
17516 with code at that address. Note that @var{address} may be a symbol like
17518 If @code{-source @var{source}} is specified, only dump symbols for that
17521 These commands are used to debug the @value{GDBN} symbol-reading code.
17522 These commands do not modify internal @value{GDBN} state, therefore
17523 @samp{maint print symbols} will only print symbols for already expanded symbol
17525 You can use the command @code{info sources} to find out which files these are.
17526 If you use @samp{maint print psymbols} instead, the dump shows information
17527 about symbols that @value{GDBN} only knows partially---that is, symbols
17528 defined in files that @value{GDBN} has skimmed, but not yet read completely.
17529 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
17532 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17533 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17535 @kindex maint info symtabs
17536 @kindex maint info psymtabs
17537 @cindex listing @value{GDBN}'s internal symbol tables
17538 @cindex symbol tables, listing @value{GDBN}'s internal
17539 @cindex full symbol tables, listing @value{GDBN}'s internal
17540 @cindex partial symbol tables, listing @value{GDBN}'s internal
17541 @item maint info symtabs @r{[} @var{regexp} @r{]}
17542 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17544 List the @code{struct symtab} or @code{struct partial_symtab}
17545 structures whose names match @var{regexp}. If @var{regexp} is not
17546 given, list them all. The output includes expressions which you can
17547 copy into a @value{GDBN} debugging this one to examine a particular
17548 structure in more detail. For example:
17551 (@value{GDBP}) maint info psymtabs dwarf2read
17552 @{ objfile /home/gnu/build/gdb/gdb
17553 ((struct objfile *) 0x82e69d0)
17554 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17555 ((struct partial_symtab *) 0x8474b10)
17558 text addresses 0x814d3c8 -- 0x8158074
17559 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17560 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17561 dependencies (none)
17564 (@value{GDBP}) maint info symtabs
17568 We see that there is one partial symbol table whose filename contains
17569 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17570 and we see that @value{GDBN} has not read in any symtabs yet at all.
17571 If we set a breakpoint on a function, that will cause @value{GDBN} to
17572 read the symtab for the compilation unit containing that function:
17575 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17576 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17578 (@value{GDBP}) maint info symtabs
17579 @{ objfile /home/gnu/build/gdb/gdb
17580 ((struct objfile *) 0x82e69d0)
17581 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17582 ((struct symtab *) 0x86c1f38)
17585 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17586 linetable ((struct linetable *) 0x8370fa0)
17587 debugformat DWARF 2
17593 @kindex maint info line-table
17594 @cindex listing @value{GDBN}'s internal line tables
17595 @cindex line tables, listing @value{GDBN}'s internal
17596 @item maint info line-table @r{[} @var{regexp} @r{]}
17598 List the @code{struct linetable} from all @code{struct symtab}
17599 instances whose name matches @var{regexp}. If @var{regexp} is not
17600 given, list the @code{struct linetable} from all @code{struct symtab}.
17602 @kindex maint set symbol-cache-size
17603 @cindex symbol cache size
17604 @item maint set symbol-cache-size @var{size}
17605 Set the size of the symbol cache to @var{size}.
17606 The default size is intended to be good enough for debugging
17607 most applications. This option exists to allow for experimenting
17608 with different sizes.
17610 @kindex maint show symbol-cache-size
17611 @item maint show symbol-cache-size
17612 Show the size of the symbol cache.
17614 @kindex maint print symbol-cache
17615 @cindex symbol cache, printing its contents
17616 @item maint print symbol-cache
17617 Print the contents of the symbol cache.
17618 This is useful when debugging symbol cache issues.
17620 @kindex maint print symbol-cache-statistics
17621 @cindex symbol cache, printing usage statistics
17622 @item maint print symbol-cache-statistics
17623 Print symbol cache usage statistics.
17624 This helps determine how well the cache is being utilized.
17626 @kindex maint flush-symbol-cache
17627 @cindex symbol cache, flushing
17628 @item maint flush-symbol-cache
17629 Flush the contents of the symbol cache, all entries are removed.
17630 This command is useful when debugging the symbol cache.
17631 It is also useful when collecting performance data.
17636 @chapter Altering Execution
17638 Once you think you have found an error in your program, you might want to
17639 find out for certain whether correcting the apparent error would lead to
17640 correct results in the rest of the run. You can find the answer by
17641 experiment, using the @value{GDBN} features for altering execution of the
17644 For example, you can store new values into variables or memory
17645 locations, give your program a signal, restart it at a different
17646 address, or even return prematurely from a function.
17649 * Assignment:: Assignment to variables
17650 * Jumping:: Continuing at a different address
17651 * Signaling:: Giving your program a signal
17652 * Returning:: Returning from a function
17653 * Calling:: Calling your program's functions
17654 * Patching:: Patching your program
17655 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17659 @section Assignment to Variables
17662 @cindex setting variables
17663 To alter the value of a variable, evaluate an assignment expression.
17664 @xref{Expressions, ,Expressions}. For example,
17671 stores the value 4 into the variable @code{x}, and then prints the
17672 value of the assignment expression (which is 4).
17673 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17674 information on operators in supported languages.
17676 @kindex set variable
17677 @cindex variables, setting
17678 If you are not interested in seeing the value of the assignment, use the
17679 @code{set} command instead of the @code{print} command. @code{set} is
17680 really the same as @code{print} except that the expression's value is
17681 not printed and is not put in the value history (@pxref{Value History,
17682 ,Value History}). The expression is evaluated only for its effects.
17684 If the beginning of the argument string of the @code{set} command
17685 appears identical to a @code{set} subcommand, use the @code{set
17686 variable} command instead of just @code{set}. This command is identical
17687 to @code{set} except for its lack of subcommands. For example, if your
17688 program has a variable @code{width}, you get an error if you try to set
17689 a new value with just @samp{set width=13}, because @value{GDBN} has the
17690 command @code{set width}:
17693 (@value{GDBP}) whatis width
17695 (@value{GDBP}) p width
17697 (@value{GDBP}) set width=47
17698 Invalid syntax in expression.
17702 The invalid expression, of course, is @samp{=47}. In
17703 order to actually set the program's variable @code{width}, use
17706 (@value{GDBP}) set var width=47
17709 Because the @code{set} command has many subcommands that can conflict
17710 with the names of program variables, it is a good idea to use the
17711 @code{set variable} command instead of just @code{set}. For example, if
17712 your program has a variable @code{g}, you run into problems if you try
17713 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17714 the command @code{set gnutarget}, abbreviated @code{set g}:
17718 (@value{GDBP}) whatis g
17722 (@value{GDBP}) set g=4
17726 The program being debugged has been started already.
17727 Start it from the beginning? (y or n) y
17728 Starting program: /home/smith/cc_progs/a.out
17729 "/home/smith/cc_progs/a.out": can't open to read symbols:
17730 Invalid bfd target.
17731 (@value{GDBP}) show g
17732 The current BFD target is "=4".
17737 The program variable @code{g} did not change, and you silently set the
17738 @code{gnutarget} to an invalid value. In order to set the variable
17742 (@value{GDBP}) set var g=4
17745 @value{GDBN} allows more implicit conversions in assignments than C; you can
17746 freely store an integer value into a pointer variable or vice versa,
17747 and you can convert any structure to any other structure that is the
17748 same length or shorter.
17749 @comment FIXME: how do structs align/pad in these conversions?
17750 @comment /doc@cygnus.com 18dec1990
17752 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17753 construct to generate a value of specified type at a specified address
17754 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17755 to memory location @code{0x83040} as an integer (which implies a certain size
17756 and representation in memory), and
17759 set @{int@}0x83040 = 4
17763 stores the value 4 into that memory location.
17766 @section Continuing at a Different Address
17768 Ordinarily, when you continue your program, you do so at the place where
17769 it stopped, with the @code{continue} command. You can instead continue at
17770 an address of your own choosing, with the following commands:
17774 @kindex j @r{(@code{jump})}
17775 @item jump @var{location}
17776 @itemx j @var{location}
17777 Resume execution at @var{location}. Execution stops again immediately
17778 if there is a breakpoint there. @xref{Specify Location}, for a description
17779 of the different forms of @var{location}. It is common
17780 practice to use the @code{tbreak} command in conjunction with
17781 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17783 The @code{jump} command does not change the current stack frame, or
17784 the stack pointer, or the contents of any memory location or any
17785 register other than the program counter. If @var{location} is in
17786 a different function from the one currently executing, the results may
17787 be bizarre if the two functions expect different patterns of arguments or
17788 of local variables. For this reason, the @code{jump} command requests
17789 confirmation if the specified line is not in the function currently
17790 executing. However, even bizarre results are predictable if you are
17791 well acquainted with the machine-language code of your program.
17794 On many systems, you can get much the same effect as the @code{jump}
17795 command by storing a new value into the register @code{$pc}. The
17796 difference is that this does not start your program running; it only
17797 changes the address of where it @emph{will} run when you continue. For
17805 makes the next @code{continue} command or stepping command execute at
17806 address @code{0x485}, rather than at the address where your program stopped.
17807 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17809 The most common occasion to use the @code{jump} command is to back
17810 up---perhaps with more breakpoints set---over a portion of a program
17811 that has already executed, in order to examine its execution in more
17816 @section Giving your Program a Signal
17817 @cindex deliver a signal to a program
17821 @item signal @var{signal}
17822 Resume execution where your program is stopped, but immediately give it the
17823 signal @var{signal}. The @var{signal} can be the name or the number of a
17824 signal. For example, on many systems @code{signal 2} and @code{signal
17825 SIGINT} are both ways of sending an interrupt signal.
17827 Alternatively, if @var{signal} is zero, continue execution without
17828 giving a signal. This is useful when your program stopped on account of
17829 a signal and would ordinarily see the signal when resumed with the
17830 @code{continue} command; @samp{signal 0} causes it to resume without a
17833 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17834 delivered to the currently selected thread, not the thread that last
17835 reported a stop. This includes the situation where a thread was
17836 stopped due to a signal. So if you want to continue execution
17837 suppressing the signal that stopped a thread, you should select that
17838 same thread before issuing the @samp{signal 0} command. If you issue
17839 the @samp{signal 0} command with another thread as the selected one,
17840 @value{GDBN} detects that and asks for confirmation.
17842 Invoking the @code{signal} command is not the same as invoking the
17843 @code{kill} utility from the shell. Sending a signal with @code{kill}
17844 causes @value{GDBN} to decide what to do with the signal depending on
17845 the signal handling tables (@pxref{Signals}). The @code{signal} command
17846 passes the signal directly to your program.
17848 @code{signal} does not repeat when you press @key{RET} a second time
17849 after executing the command.
17851 @kindex queue-signal
17852 @item queue-signal @var{signal}
17853 Queue @var{signal} to be delivered immediately to the current thread
17854 when execution of the thread resumes. The @var{signal} can be the name or
17855 the number of a signal. For example, on many systems @code{signal 2} and
17856 @code{signal SIGINT} are both ways of sending an interrupt signal.
17857 The handling of the signal must be set to pass the signal to the program,
17858 otherwise @value{GDBN} will report an error.
17859 You can control the handling of signals from @value{GDBN} with the
17860 @code{handle} command (@pxref{Signals}).
17862 Alternatively, if @var{signal} is zero, any currently queued signal
17863 for the current thread is discarded and when execution resumes no signal
17864 will be delivered. This is useful when your program stopped on account
17865 of a signal and would ordinarily see the signal when resumed with the
17866 @code{continue} command.
17868 This command differs from the @code{signal} command in that the signal
17869 is just queued, execution is not resumed. And @code{queue-signal} cannot
17870 be used to pass a signal whose handling state has been set to @code{nopass}
17875 @xref{stepping into signal handlers}, for information on how stepping
17876 commands behave when the thread has a signal queued.
17879 @section Returning from a Function
17882 @cindex returning from a function
17885 @itemx return @var{expression}
17886 You can cancel execution of a function call with the @code{return}
17887 command. If you give an
17888 @var{expression} argument, its value is used as the function's return
17892 When you use @code{return}, @value{GDBN} discards the selected stack frame
17893 (and all frames within it). You can think of this as making the
17894 discarded frame return prematurely. If you wish to specify a value to
17895 be returned, give that value as the argument to @code{return}.
17897 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17898 Frame}), and any other frames inside of it, leaving its caller as the
17899 innermost remaining frame. That frame becomes selected. The
17900 specified value is stored in the registers used for returning values
17903 The @code{return} command does not resume execution; it leaves the
17904 program stopped in the state that would exist if the function had just
17905 returned. In contrast, the @code{finish} command (@pxref{Continuing
17906 and Stepping, ,Continuing and Stepping}) resumes execution until the
17907 selected stack frame returns naturally.
17909 @value{GDBN} needs to know how the @var{expression} argument should be set for
17910 the inferior. The concrete registers assignment depends on the OS ABI and the
17911 type being returned by the selected stack frame. For example it is common for
17912 OS ABI to return floating point values in FPU registers while integer values in
17913 CPU registers. Still some ABIs return even floating point values in CPU
17914 registers. Larger integer widths (such as @code{long long int}) also have
17915 specific placement rules. @value{GDBN} already knows the OS ABI from its
17916 current target so it needs to find out also the type being returned to make the
17917 assignment into the right register(s).
17919 Normally, the selected stack frame has debug info. @value{GDBN} will always
17920 use the debug info instead of the implicit type of @var{expression} when the
17921 debug info is available. For example, if you type @kbd{return -1}, and the
17922 function in the current stack frame is declared to return a @code{long long
17923 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17924 into a @code{long long int}:
17927 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17929 (@value{GDBP}) return -1
17930 Make func return now? (y or n) y
17931 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17932 43 printf ("result=%lld\n", func ());
17936 However, if the selected stack frame does not have a debug info, e.g., if the
17937 function was compiled without debug info, @value{GDBN} has to find out the type
17938 to return from user. Specifying a different type by mistake may set the value
17939 in different inferior registers than the caller code expects. For example,
17940 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17941 of a @code{long long int} result for a debug info less function (on 32-bit
17942 architectures). Therefore the user is required to specify the return type by
17943 an appropriate cast explicitly:
17946 Breakpoint 2, 0x0040050b in func ()
17947 (@value{GDBP}) return -1
17948 Return value type not available for selected stack frame.
17949 Please use an explicit cast of the value to return.
17950 (@value{GDBP}) return (long long int) -1
17951 Make selected stack frame return now? (y or n) y
17952 #0 0x00400526 in main ()
17957 @section Calling Program Functions
17960 @cindex calling functions
17961 @cindex inferior functions, calling
17962 @item print @var{expr}
17963 Evaluate the expression @var{expr} and display the resulting value.
17964 The expression may include calls to functions in the program being
17968 @item call @var{expr}
17969 Evaluate the expression @var{expr} without displaying @code{void}
17972 You can use this variant of the @code{print} command if you want to
17973 execute a function from your program that does not return anything
17974 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17975 with @code{void} returned values that @value{GDBN} will otherwise
17976 print. If the result is not void, it is printed and saved in the
17980 It is possible for the function you call via the @code{print} or
17981 @code{call} command to generate a signal (e.g., if there's a bug in
17982 the function, or if you passed it incorrect arguments). What happens
17983 in that case is controlled by the @code{set unwindonsignal} command.
17985 Similarly, with a C@t{++} program it is possible for the function you
17986 call via the @code{print} or @code{call} command to generate an
17987 exception that is not handled due to the constraints of the dummy
17988 frame. In this case, any exception that is raised in the frame, but has
17989 an out-of-frame exception handler will not be found. GDB builds a
17990 dummy-frame for the inferior function call, and the unwinder cannot
17991 seek for exception handlers outside of this dummy-frame. What happens
17992 in that case is controlled by the
17993 @code{set unwind-on-terminating-exception} command.
17996 @item set unwindonsignal
17997 @kindex set unwindonsignal
17998 @cindex unwind stack in called functions
17999 @cindex call dummy stack unwinding
18000 Set unwinding of the stack if a signal is received while in a function
18001 that @value{GDBN} called in the program being debugged. If set to on,
18002 @value{GDBN} unwinds the stack it created for the call and restores
18003 the context to what it was before the call. If set to off (the
18004 default), @value{GDBN} stops in the frame where the signal was
18007 @item show unwindonsignal
18008 @kindex show unwindonsignal
18009 Show the current setting of stack unwinding in the functions called by
18012 @item set unwind-on-terminating-exception
18013 @kindex set unwind-on-terminating-exception
18014 @cindex unwind stack in called functions with unhandled exceptions
18015 @cindex call dummy stack unwinding on unhandled exception.
18016 Set unwinding of the stack if a C@t{++} exception is raised, but left
18017 unhandled while in a function that @value{GDBN} called in the program being
18018 debugged. If set to on (the default), @value{GDBN} unwinds the stack
18019 it created for the call and restores the context to what it was before
18020 the call. If set to off, @value{GDBN} the exception is delivered to
18021 the default C@t{++} exception handler and the inferior terminated.
18023 @item show unwind-on-terminating-exception
18024 @kindex show unwind-on-terminating-exception
18025 Show the current setting of stack unwinding in the functions called by
18030 @subsection Calling functions with no debug info
18032 @cindex no debug info functions
18033 Sometimes, a function you wish to call is missing debug information.
18034 In such case, @value{GDBN} does not know the type of the function,
18035 including the types of the function's parameters. To avoid calling
18036 the inferior function incorrectly, which could result in the called
18037 function functioning erroneously and even crash, @value{GDBN} refuses
18038 to call the function unless you tell it the type of the function.
18040 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18041 to do that. The simplest is to cast the call to the function's
18042 declared return type. For example:
18045 (@value{GDBP}) p getenv ("PATH")
18046 'getenv' has unknown return type; cast the call to its declared return type
18047 (@value{GDBP}) p (char *) getenv ("PATH")
18048 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18051 Casting the return type of a no-debug function is equivalent to
18052 casting the function to a pointer to a prototyped function that has a
18053 prototype that matches the types of the passed-in arguments, and
18054 calling that. I.e., the call above is equivalent to:
18057 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18061 and given this prototyped C or C++ function with float parameters:
18064 float multiply (float v1, float v2) @{ return v1 * v2; @}
18068 these calls are equivalent:
18071 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18072 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18075 If the function you wish to call is declared as unprototyped (i.e.@:
18076 old K&R style), you must use the cast-to-function-pointer syntax, so
18077 that @value{GDBN} knows that it needs to apply default argument
18078 promotions (promote float arguments to double). @xref{ABI, float
18079 promotion}. For example, given this unprototyped C function with
18080 float parameters, and no debug info:
18084 multiply_noproto (v1, v2)
18092 you call it like this:
18095 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18099 @section Patching Programs
18101 @cindex patching binaries
18102 @cindex writing into executables
18103 @cindex writing into corefiles
18105 By default, @value{GDBN} opens the file containing your program's
18106 executable code (or the corefile) read-only. This prevents accidental
18107 alterations to machine code; but it also prevents you from intentionally
18108 patching your program's binary.
18110 If you'd like to be able to patch the binary, you can specify that
18111 explicitly with the @code{set write} command. For example, you might
18112 want to turn on internal debugging flags, or even to make emergency
18118 @itemx set write off
18119 If you specify @samp{set write on}, @value{GDBN} opens executable and
18120 core files for both reading and writing; if you specify @kbd{set write
18121 off} (the default), @value{GDBN} opens them read-only.
18123 If you have already loaded a file, you must load it again (using the
18124 @code{exec-file} or @code{core-file} command) after changing @code{set
18125 write}, for your new setting to take effect.
18129 Display whether executable files and core files are opened for writing
18130 as well as reading.
18133 @node Compiling and Injecting Code
18134 @section Compiling and injecting code in @value{GDBN}
18135 @cindex injecting code
18136 @cindex writing into executables
18137 @cindex compiling code
18139 @value{GDBN} supports on-demand compilation and code injection into
18140 programs running under @value{GDBN}. GCC 5.0 or higher built with
18141 @file{libcc1.so} must be installed for this functionality to be enabled.
18142 This functionality is implemented with the following commands.
18145 @kindex compile code
18146 @item compile code @var{source-code}
18147 @itemx compile code -raw @var{--} @var{source-code}
18148 Compile @var{source-code} with the compiler language found as the current
18149 language in @value{GDBN} (@pxref{Languages}). If compilation and
18150 injection is not supported with the current language specified in
18151 @value{GDBN}, or the compiler does not support this feature, an error
18152 message will be printed. If @var{source-code} compiles and links
18153 successfully, @value{GDBN} will load the object-code emitted,
18154 and execute it within the context of the currently selected inferior.
18155 It is important to note that the compiled code is executed immediately.
18156 After execution, the compiled code is removed from @value{GDBN} and any
18157 new types or variables you have defined will be deleted.
18159 The command allows you to specify @var{source-code} in two ways.
18160 The simplest method is to provide a single line of code to the command.
18164 compile code printf ("hello world\n");
18167 If you specify options on the command line as well as source code, they
18168 may conflict. The @samp{--} delimiter can be used to separate options
18169 from actual source code. E.g.:
18172 compile code -r -- printf ("hello world\n");
18175 Alternatively you can enter source code as multiple lines of text. To
18176 enter this mode, invoke the @samp{compile code} command without any text
18177 following the command. This will start the multiple-line editor and
18178 allow you to type as many lines of source code as required. When you
18179 have completed typing, enter @samp{end} on its own line to exit the
18184 >printf ("hello\n");
18185 >printf ("world\n");
18189 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18190 provided @var{source-code} in a callable scope. In this case, you must
18191 specify the entry point of the code by defining a function named
18192 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18193 inferior. Using @samp{-raw} option may be needed for example when
18194 @var{source-code} requires @samp{#include} lines which may conflict with
18195 inferior symbols otherwise.
18197 @kindex compile file
18198 @item compile file @var{filename}
18199 @itemx compile file -raw @var{filename}
18200 Like @code{compile code}, but take the source code from @var{filename}.
18203 compile file /home/user/example.c
18208 @item compile print @var{expr}
18209 @itemx compile print /@var{f} @var{expr}
18210 Compile and execute @var{expr} with the compiler language found as the
18211 current language in @value{GDBN} (@pxref{Languages}). By default the
18212 value of @var{expr} is printed in a format appropriate to its data type;
18213 you can choose a different format by specifying @samp{/@var{f}}, where
18214 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18217 @item compile print
18218 @itemx compile print /@var{f}
18219 @cindex reprint the last value
18220 Alternatively you can enter the expression (source code producing it) as
18221 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18222 command without any text following the command. This will start the
18223 multiple-line editor.
18227 The process of compiling and injecting the code can be inspected using:
18230 @anchor{set debug compile}
18231 @item set debug compile
18232 @cindex compile command debugging info
18233 Turns on or off display of @value{GDBN} process of compiling and
18234 injecting the code. The default is off.
18236 @item show debug compile
18237 Displays the current state of displaying @value{GDBN} process of
18238 compiling and injecting the code.
18241 @subsection Compilation options for the @code{compile} command
18243 @value{GDBN} needs to specify the right compilation options for the code
18244 to be injected, in part to make its ABI compatible with the inferior
18245 and in part to make the injected code compatible with @value{GDBN}'s
18249 The options used, in increasing precedence:
18252 @item target architecture and OS options (@code{gdbarch})
18253 These options depend on target processor type and target operating
18254 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18255 (@code{-m64}) compilation option.
18257 @item compilation options recorded in the target
18258 @value{NGCC} (since version 4.7) stores the options used for compilation
18259 into @code{DW_AT_producer} part of DWARF debugging information according
18260 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18261 explicitly specify @code{-g} during inferior compilation otherwise
18262 @value{NGCC} produces no DWARF. This feature is only relevant for
18263 platforms where @code{-g} produces DWARF by default, otherwise one may
18264 try to enforce DWARF by using @code{-gdwarf-4}.
18266 @item compilation options set by @code{set compile-args}
18270 You can override compilation options using the following command:
18273 @item set compile-args
18274 @cindex compile command options override
18275 Set compilation options used for compiling and injecting code with the
18276 @code{compile} commands. These options override any conflicting ones
18277 from the target architecture and/or options stored during inferior
18280 @item show compile-args
18281 Displays the current state of compilation options override.
18282 This does not show all the options actually used during compilation,
18283 use @ref{set debug compile} for that.
18286 @subsection Caveats when using the @code{compile} command
18288 There are a few caveats to keep in mind when using the @code{compile}
18289 command. As the caveats are different per language, the table below
18290 highlights specific issues on a per language basis.
18293 @item C code examples and caveats
18294 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18295 attempt to compile the source code with a @samp{C} compiler. The source
18296 code provided to the @code{compile} command will have much the same
18297 access to variables and types as it normally would if it were part of
18298 the program currently being debugged in @value{GDBN}.
18300 Below is a sample program that forms the basis of the examples that
18301 follow. This program has been compiled and loaded into @value{GDBN},
18302 much like any other normal debugging session.
18305 void function1 (void)
18308 printf ("function 1\n");
18311 void function2 (void)
18326 For the purposes of the examples in this section, the program above has
18327 been compiled, loaded into @value{GDBN}, stopped at the function
18328 @code{main}, and @value{GDBN} is awaiting input from the user.
18330 To access variables and types for any program in @value{GDBN}, the
18331 program must be compiled and packaged with debug information. The
18332 @code{compile} command is not an exception to this rule. Without debug
18333 information, you can still use the @code{compile} command, but you will
18334 be very limited in what variables and types you can access.
18336 So with that in mind, the example above has been compiled with debug
18337 information enabled. The @code{compile} command will have access to
18338 all variables and types (except those that may have been optimized
18339 out). Currently, as @value{GDBN} has stopped the program in the
18340 @code{main} function, the @code{compile} command would have access to
18341 the variable @code{k}. You could invoke the @code{compile} command
18342 and type some source code to set the value of @code{k}. You can also
18343 read it, or do anything with that variable you would normally do in
18344 @code{C}. Be aware that changes to inferior variables in the
18345 @code{compile} command are persistent. In the following example:
18348 compile code k = 3;
18352 the variable @code{k} is now 3. It will retain that value until
18353 something else in the example program changes it, or another
18354 @code{compile} command changes it.
18356 Normal scope and access rules apply to source code compiled and
18357 injected by the @code{compile} command. In the example, the variables
18358 @code{j} and @code{k} are not accessible yet, because the program is
18359 currently stopped in the @code{main} function, where these variables
18360 are not in scope. Therefore, the following command
18363 compile code j = 3;
18367 will result in a compilation error message.
18369 Once the program is continued, execution will bring these variables in
18370 scope, and they will become accessible; then the code you specify via
18371 the @code{compile} command will be able to access them.
18373 You can create variables and types with the @code{compile} command as
18374 part of your source code. Variables and types that are created as part
18375 of the @code{compile} command are not visible to the rest of the program for
18376 the duration of its run. This example is valid:
18379 compile code int ff = 5; printf ("ff is %d\n", ff);
18382 However, if you were to type the following into @value{GDBN} after that
18383 command has completed:
18386 compile code printf ("ff is %d\n'', ff);
18390 a compiler error would be raised as the variable @code{ff} no longer
18391 exists. Object code generated and injected by the @code{compile}
18392 command is removed when its execution ends. Caution is advised
18393 when assigning to program variables values of variables created by the
18394 code submitted to the @code{compile} command. This example is valid:
18397 compile code int ff = 5; k = ff;
18400 The value of the variable @code{ff} is assigned to @code{k}. The variable
18401 @code{k} does not require the existence of @code{ff} to maintain the value
18402 it has been assigned. However, pointers require particular care in
18403 assignment. If the source code compiled with the @code{compile} command
18404 changed the address of a pointer in the example program, perhaps to a
18405 variable created in the @code{compile} command, that pointer would point
18406 to an invalid location when the command exits. The following example
18407 would likely cause issues with your debugged program:
18410 compile code int ff = 5; p = &ff;
18413 In this example, @code{p} would point to @code{ff} when the
18414 @code{compile} command is executing the source code provided to it.
18415 However, as variables in the (example) program persist with their
18416 assigned values, the variable @code{p} would point to an invalid
18417 location when the command exists. A general rule should be followed
18418 in that you should either assign @code{NULL} to any assigned pointers,
18419 or restore a valid location to the pointer before the command exits.
18421 Similar caution must be exercised with any structs, unions, and typedefs
18422 defined in @code{compile} command. Types defined in the @code{compile}
18423 command will no longer be available in the next @code{compile} command.
18424 Therefore, if you cast a variable to a type defined in the
18425 @code{compile} command, care must be taken to ensure that any future
18426 need to resolve the type can be achieved.
18429 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18430 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18431 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18432 Compilation failed.
18433 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18437 Variables that have been optimized away by the compiler are not
18438 accessible to the code submitted to the @code{compile} command.
18439 Access to those variables will generate a compiler error which @value{GDBN}
18440 will print to the console.
18443 @subsection Compiler search for the @code{compile} command
18445 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
18446 which may not be obvious for remote targets of different architecture
18447 than where @value{GDBN} is running. Environment variable @code{PATH} on
18448 @value{GDBN} host is searched for @value{NGCC} binary matching the
18449 target architecture and operating system. This search can be overriden
18450 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
18451 taken from shell that executed @value{GDBN}, it is not the value set by
18452 @value{GDBN} command @code{set environment}). @xref{Environment}.
18455 Specifically @code{PATH} is searched for binaries matching regular expression
18456 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18457 debugged. @var{arch} is processor name --- multiarch is supported, so for
18458 example both @code{i386} and @code{x86_64} targets look for pattern
18459 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18460 for pattern @code{s390x?}. @var{os} is currently supported only for
18461 pattern @code{linux(-gnu)?}.
18463 On Posix hosts the compiler driver @value{GDBN} needs to find also
18464 shared library @file{libcc1.so} from the compiler. It is searched in
18465 default shared library search path (overridable with usual environment
18466 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
18467 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
18468 according to the installation of the found compiler --- as possibly
18469 specified by the @code{set compile-gcc} command.
18472 @item set compile-gcc
18473 @cindex compile command driver filename override
18474 Set compilation command used for compiling and injecting code with the
18475 @code{compile} commands. If this option is not set (it is set to
18476 an empty string), the search described above will occur --- that is the
18479 @item show compile-gcc
18480 Displays the current compile command @value{NGCC} driver filename.
18481 If set, it is the main command @command{gcc}, found usually for example
18482 under name @file{x86_64-linux-gnu-gcc}.
18486 @chapter @value{GDBN} Files
18488 @value{GDBN} needs to know the file name of the program to be debugged,
18489 both in order to read its symbol table and in order to start your
18490 program. To debug a core dump of a previous run, you must also tell
18491 @value{GDBN} the name of the core dump file.
18494 * Files:: Commands to specify files
18495 * File Caching:: Information about @value{GDBN}'s file caching
18496 * Separate Debug Files:: Debugging information in separate files
18497 * MiniDebugInfo:: Debugging information in a special section
18498 * Index Files:: Index files speed up GDB
18499 * Symbol Errors:: Errors reading symbol files
18500 * Data Files:: GDB data files
18504 @section Commands to Specify Files
18506 @cindex symbol table
18507 @cindex core dump file
18509 You may want to specify executable and core dump file names. The usual
18510 way to do this is at start-up time, using the arguments to
18511 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18512 Out of @value{GDBN}}).
18514 Occasionally it is necessary to change to a different file during a
18515 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18516 specify a file you want to use. Or you are debugging a remote target
18517 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18518 Program}). In these situations the @value{GDBN} commands to specify
18519 new files are useful.
18522 @cindex executable file
18524 @item file @var{filename}
18525 Use @var{filename} as the program to be debugged. It is read for its
18526 symbols and for the contents of pure memory. It is also the program
18527 executed when you use the @code{run} command. If you do not specify a
18528 directory and the file is not found in the @value{GDBN} working directory,
18529 @value{GDBN} uses the environment variable @code{PATH} as a list of
18530 directories to search, just as the shell does when looking for a program
18531 to run. You can change the value of this variable, for both @value{GDBN}
18532 and your program, using the @code{path} command.
18534 @cindex unlinked object files
18535 @cindex patching object files
18536 You can load unlinked object @file{.o} files into @value{GDBN} using
18537 the @code{file} command. You will not be able to ``run'' an object
18538 file, but you can disassemble functions and inspect variables. Also,
18539 if the underlying BFD functionality supports it, you could use
18540 @kbd{gdb -write} to patch object files using this technique. Note
18541 that @value{GDBN} can neither interpret nor modify relocations in this
18542 case, so branches and some initialized variables will appear to go to
18543 the wrong place. But this feature is still handy from time to time.
18546 @code{file} with no argument makes @value{GDBN} discard any information it
18547 has on both executable file and the symbol table.
18550 @item exec-file @r{[} @var{filename} @r{]}
18551 Specify that the program to be run (but not the symbol table) is found
18552 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18553 if necessary to locate your program. Omitting @var{filename} means to
18554 discard information on the executable file.
18556 @kindex symbol-file
18557 @item symbol-file @r{[} @var{filename} @r{]}
18558 Read symbol table information from file @var{filename}. @code{PATH} is
18559 searched when necessary. Use the @code{file} command to get both symbol
18560 table and program to run from the same file.
18562 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18563 program's symbol table.
18565 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18566 some breakpoints and auto-display expressions. This is because they may
18567 contain pointers to the internal data recording symbols and data types,
18568 which are part of the old symbol table data being discarded inside
18571 @code{symbol-file} does not repeat if you press @key{RET} again after
18574 When @value{GDBN} is configured for a particular environment, it
18575 understands debugging information in whatever format is the standard
18576 generated for that environment; you may use either a @sc{gnu} compiler, or
18577 other compilers that adhere to the local conventions.
18578 Best results are usually obtained from @sc{gnu} compilers; for example,
18579 using @code{@value{NGCC}} you can generate debugging information for
18582 For most kinds of object files, with the exception of old SVR3 systems
18583 using COFF, the @code{symbol-file} command does not normally read the
18584 symbol table in full right away. Instead, it scans the symbol table
18585 quickly to find which source files and which symbols are present. The
18586 details are read later, one source file at a time, as they are needed.
18588 The purpose of this two-stage reading strategy is to make @value{GDBN}
18589 start up faster. For the most part, it is invisible except for
18590 occasional pauses while the symbol table details for a particular source
18591 file are being read. (The @code{set verbose} command can turn these
18592 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18593 Warnings and Messages}.)
18595 We have not implemented the two-stage strategy for COFF yet. When the
18596 symbol table is stored in COFF format, @code{symbol-file} reads the
18597 symbol table data in full right away. Note that ``stabs-in-COFF''
18598 still does the two-stage strategy, since the debug info is actually
18602 @cindex reading symbols immediately
18603 @cindex symbols, reading immediately
18604 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18605 @itemx file @r{[} -readnow @r{]} @var{filename}
18606 You can override the @value{GDBN} two-stage strategy for reading symbol
18607 tables by using the @samp{-readnow} option with any of the commands that
18608 load symbol table information, if you want to be sure @value{GDBN} has the
18609 entire symbol table available.
18611 @cindex @code{-readnever}, option for symbol-file command
18612 @cindex never read symbols
18613 @cindex symbols, never read
18614 @item symbol-file @r{[} -readnever @r{]} @var{filename}
18615 @itemx file @r{[} -readnever @r{]} @var{filename}
18616 You can instruct @value{GDBN} to never read the symbolic information
18617 contained in @var{filename} by using the @samp{-readnever} option.
18618 @xref{--readnever}.
18620 @c FIXME: for now no mention of directories, since this seems to be in
18621 @c flux. 13mar1992 status is that in theory GDB would look either in
18622 @c current dir or in same dir as myprog; but issues like competing
18623 @c GDB's, or clutter in system dirs, mean that in practice right now
18624 @c only current dir is used. FFish says maybe a special GDB hierarchy
18625 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18629 @item core-file @r{[}@var{filename}@r{]}
18631 Specify the whereabouts of a core dump file to be used as the ``contents
18632 of memory''. Traditionally, core files contain only some parts of the
18633 address space of the process that generated them; @value{GDBN} can access the
18634 executable file itself for other parts.
18636 @code{core-file} with no argument specifies that no core file is
18639 Note that the core file is ignored when your program is actually running
18640 under @value{GDBN}. So, if you have been running your program and you
18641 wish to debug a core file instead, you must kill the subprocess in which
18642 the program is running. To do this, use the @code{kill} command
18643 (@pxref{Kill Process, ,Killing the Child Process}).
18645 @kindex add-symbol-file
18646 @cindex dynamic linking
18647 @item add-symbol-file @var{filename} @var{address}
18648 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{|} -readnever @r{]}
18649 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18650 The @code{add-symbol-file} command reads additional symbol table
18651 information from the file @var{filename}. You would use this command
18652 when @var{filename} has been dynamically loaded (by some other means)
18653 into the program that is running. The @var{address} should give the memory
18654 address at which the file has been loaded; @value{GDBN} cannot figure
18655 this out for itself. You can additionally specify an arbitrary number
18656 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18657 section name and base address for that section. You can specify any
18658 @var{address} as an expression.
18660 The symbol table of the file @var{filename} is added to the symbol table
18661 originally read with the @code{symbol-file} command. You can use the
18662 @code{add-symbol-file} command any number of times; the new symbol data
18663 thus read is kept in addition to the old.
18665 Changes can be reverted using the command @code{remove-symbol-file}.
18667 @cindex relocatable object files, reading symbols from
18668 @cindex object files, relocatable, reading symbols from
18669 @cindex reading symbols from relocatable object files
18670 @cindex symbols, reading from relocatable object files
18671 @cindex @file{.o} files, reading symbols from
18672 Although @var{filename} is typically a shared library file, an
18673 executable file, or some other object file which has been fully
18674 relocated for loading into a process, you can also load symbolic
18675 information from relocatable @file{.o} files, as long as:
18679 the file's symbolic information refers only to linker symbols defined in
18680 that file, not to symbols defined by other object files,
18682 every section the file's symbolic information refers to has actually
18683 been loaded into the inferior, as it appears in the file, and
18685 you can determine the address at which every section was loaded, and
18686 provide these to the @code{add-symbol-file} command.
18690 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18691 relocatable files into an already running program; such systems
18692 typically make the requirements above easy to meet. However, it's
18693 important to recognize that many native systems use complex link
18694 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18695 assembly, for example) that make the requirements difficult to meet. In
18696 general, one cannot assume that using @code{add-symbol-file} to read a
18697 relocatable object file's symbolic information will have the same effect
18698 as linking the relocatable object file into the program in the normal
18701 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18703 @kindex remove-symbol-file
18704 @item remove-symbol-file @var{filename}
18705 @item remove-symbol-file -a @var{address}
18706 Remove a symbol file added via the @code{add-symbol-file} command. The
18707 file to remove can be identified by its @var{filename} or by an @var{address}
18708 that lies within the boundaries of this symbol file in memory. Example:
18711 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18712 add symbol table from file "/home/user/gdb/mylib.so" at
18713 .text_addr = 0x7ffff7ff9480
18715 Reading symbols from /home/user/gdb/mylib.so...done.
18716 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18717 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18722 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18724 @kindex add-symbol-file-from-memory
18725 @cindex @code{syscall DSO}
18726 @cindex load symbols from memory
18727 @item add-symbol-file-from-memory @var{address}
18728 Load symbols from the given @var{address} in a dynamically loaded
18729 object file whose image is mapped directly into the inferior's memory.
18730 For example, the Linux kernel maps a @code{syscall DSO} into each
18731 process's address space; this DSO provides kernel-specific code for
18732 some system calls. The argument can be any expression whose
18733 evaluation yields the address of the file's shared object file header.
18734 For this command to work, you must have used @code{symbol-file} or
18735 @code{exec-file} commands in advance.
18738 @item section @var{section} @var{addr}
18739 The @code{section} command changes the base address of the named
18740 @var{section} of the exec file to @var{addr}. This can be used if the
18741 exec file does not contain section addresses, (such as in the
18742 @code{a.out} format), or when the addresses specified in the file
18743 itself are wrong. Each section must be changed separately. The
18744 @code{info files} command, described below, lists all the sections and
18748 @kindex info target
18751 @code{info files} and @code{info target} are synonymous; both print the
18752 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18753 including the names of the executable and core dump files currently in
18754 use by @value{GDBN}, and the files from which symbols were loaded. The
18755 command @code{help target} lists all possible targets rather than
18758 @kindex maint info sections
18759 @item maint info sections
18760 Another command that can give you extra information about program sections
18761 is @code{maint info sections}. In addition to the section information
18762 displayed by @code{info files}, this command displays the flags and file
18763 offset of each section in the executable and core dump files. In addition,
18764 @code{maint info sections} provides the following command options (which
18765 may be arbitrarily combined):
18769 Display sections for all loaded object files, including shared libraries.
18770 @item @var{sections}
18771 Display info only for named @var{sections}.
18772 @item @var{section-flags}
18773 Display info only for sections for which @var{section-flags} are true.
18774 The section flags that @value{GDBN} currently knows about are:
18777 Section will have space allocated in the process when loaded.
18778 Set for all sections except those containing debug information.
18780 Section will be loaded from the file into the child process memory.
18781 Set for pre-initialized code and data, clear for @code{.bss} sections.
18783 Section needs to be relocated before loading.
18785 Section cannot be modified by the child process.
18787 Section contains executable code only.
18789 Section contains data only (no executable code).
18791 Section will reside in ROM.
18793 Section contains data for constructor/destructor lists.
18795 Section is not empty.
18797 An instruction to the linker to not output the section.
18798 @item COFF_SHARED_LIBRARY
18799 A notification to the linker that the section contains
18800 COFF shared library information.
18802 Section contains common symbols.
18805 @kindex set trust-readonly-sections
18806 @cindex read-only sections
18807 @item set trust-readonly-sections on
18808 Tell @value{GDBN} that readonly sections in your object file
18809 really are read-only (i.e.@: that their contents will not change).
18810 In that case, @value{GDBN} can fetch values from these sections
18811 out of the object file, rather than from the target program.
18812 For some targets (notably embedded ones), this can be a significant
18813 enhancement to debugging performance.
18815 The default is off.
18817 @item set trust-readonly-sections off
18818 Tell @value{GDBN} not to trust readonly sections. This means that
18819 the contents of the section might change while the program is running,
18820 and must therefore be fetched from the target when needed.
18822 @item show trust-readonly-sections
18823 Show the current setting of trusting readonly sections.
18826 All file-specifying commands allow both absolute and relative file names
18827 as arguments. @value{GDBN} always converts the file name to an absolute file
18828 name and remembers it that way.
18830 @cindex shared libraries
18831 @anchor{Shared Libraries}
18832 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18833 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18834 DSBT (TIC6X) shared libraries.
18836 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18837 shared libraries. @xref{Expat}.
18839 @value{GDBN} automatically loads symbol definitions from shared libraries
18840 when you use the @code{run} command, or when you examine a core file.
18841 (Before you issue the @code{run} command, @value{GDBN} does not understand
18842 references to a function in a shared library, however---unless you are
18843 debugging a core file).
18845 @c FIXME: some @value{GDBN} release may permit some refs to undef
18846 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18847 @c FIXME...lib; check this from time to time when updating manual
18849 There are times, however, when you may wish to not automatically load
18850 symbol definitions from shared libraries, such as when they are
18851 particularly large or there are many of them.
18853 To control the automatic loading of shared library symbols, use the
18857 @kindex set auto-solib-add
18858 @item set auto-solib-add @var{mode}
18859 If @var{mode} is @code{on}, symbols from all shared object libraries
18860 will be loaded automatically when the inferior begins execution, you
18861 attach to an independently started inferior, or when the dynamic linker
18862 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18863 is @code{off}, symbols must be loaded manually, using the
18864 @code{sharedlibrary} command. The default value is @code{on}.
18866 @cindex memory used for symbol tables
18867 If your program uses lots of shared libraries with debug info that
18868 takes large amounts of memory, you can decrease the @value{GDBN}
18869 memory footprint by preventing it from automatically loading the
18870 symbols from shared libraries. To that end, type @kbd{set
18871 auto-solib-add off} before running the inferior, then load each
18872 library whose debug symbols you do need with @kbd{sharedlibrary
18873 @var{regexp}}, where @var{regexp} is a regular expression that matches
18874 the libraries whose symbols you want to be loaded.
18876 @kindex show auto-solib-add
18877 @item show auto-solib-add
18878 Display the current autoloading mode.
18881 @cindex load shared library
18882 To explicitly load shared library symbols, use the @code{sharedlibrary}
18886 @kindex info sharedlibrary
18888 @item info share @var{regex}
18889 @itemx info sharedlibrary @var{regex}
18890 Print the names of the shared libraries which are currently loaded
18891 that match @var{regex}. If @var{regex} is omitted then print
18892 all shared libraries that are loaded.
18895 @item info dll @var{regex}
18896 This is an alias of @code{info sharedlibrary}.
18898 @kindex sharedlibrary
18900 @item sharedlibrary @var{regex}
18901 @itemx share @var{regex}
18902 Load shared object library symbols for files matching a
18903 Unix regular expression.
18904 As with files loaded automatically, it only loads shared libraries
18905 required by your program for a core file or after typing @code{run}. If
18906 @var{regex} is omitted all shared libraries required by your program are
18909 @item nosharedlibrary
18910 @kindex nosharedlibrary
18911 @cindex unload symbols from shared libraries
18912 Unload all shared object library symbols. This discards all symbols
18913 that have been loaded from all shared libraries. Symbols from shared
18914 libraries that were loaded by explicit user requests are not
18918 Sometimes you may wish that @value{GDBN} stops and gives you control
18919 when any of shared library events happen. The best way to do this is
18920 to use @code{catch load} and @code{catch unload} (@pxref{Set
18923 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18924 command for this. This command exists for historical reasons. It is
18925 less useful than setting a catchpoint, because it does not allow for
18926 conditions or commands as a catchpoint does.
18929 @item set stop-on-solib-events
18930 @kindex set stop-on-solib-events
18931 This command controls whether @value{GDBN} should give you control
18932 when the dynamic linker notifies it about some shared library event.
18933 The most common event of interest is loading or unloading of a new
18936 @item show stop-on-solib-events
18937 @kindex show stop-on-solib-events
18938 Show whether @value{GDBN} stops and gives you control when shared
18939 library events happen.
18942 Shared libraries are also supported in many cross or remote debugging
18943 configurations. @value{GDBN} needs to have access to the target's libraries;
18944 this can be accomplished either by providing copies of the libraries
18945 on the host system, or by asking @value{GDBN} to automatically retrieve the
18946 libraries from the target. If copies of the target libraries are
18947 provided, they need to be the same as the target libraries, although the
18948 copies on the target can be stripped as long as the copies on the host are
18951 @cindex where to look for shared libraries
18952 For remote debugging, you need to tell @value{GDBN} where the target
18953 libraries are, so that it can load the correct copies---otherwise, it
18954 may try to load the host's libraries. @value{GDBN} has two variables
18955 to specify the search directories for target libraries.
18958 @cindex prefix for executable and shared library file names
18959 @cindex system root, alternate
18960 @kindex set solib-absolute-prefix
18961 @kindex set sysroot
18962 @item set sysroot @var{path}
18963 Use @var{path} as the system root for the program being debugged. Any
18964 absolute shared library paths will be prefixed with @var{path}; many
18965 runtime loaders store the absolute paths to the shared library in the
18966 target program's memory. When starting processes remotely, and when
18967 attaching to already-running processes (local or remote), their
18968 executable filenames will be prefixed with @var{path} if reported to
18969 @value{GDBN} as absolute by the operating system. If you use
18970 @code{set sysroot} to find executables and shared libraries, they need
18971 to be laid out in the same way that they are on the target, with
18972 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18975 If @var{path} starts with the sequence @file{target:} and the target
18976 system is remote then @value{GDBN} will retrieve the target binaries
18977 from the remote system. This is only supported when using a remote
18978 target that supports the @code{remote get} command (@pxref{File
18979 Transfer,,Sending files to a remote system}). The part of @var{path}
18980 following the initial @file{target:} (if present) is used as system
18981 root prefix on the remote file system. If @var{path} starts with the
18982 sequence @file{remote:} this is converted to the sequence
18983 @file{target:} by @code{set sysroot}@footnote{Historically the
18984 functionality to retrieve binaries from the remote system was
18985 provided by prefixing @var{path} with @file{remote:}}. If you want
18986 to specify a local system root using a directory that happens to be
18987 named @file{target:} or @file{remote:}, you need to use some
18988 equivalent variant of the name like @file{./target:}.
18990 For targets with an MS-DOS based filesystem, such as MS-Windows and
18991 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18992 absolute file name with @var{path}. But first, on Unix hosts,
18993 @value{GDBN} converts all backslash directory separators into forward
18994 slashes, because the backslash is not a directory separator on Unix:
18997 c:\foo\bar.dll @result{} c:/foo/bar.dll
19000 Then, @value{GDBN} attempts prefixing the target file name with
19001 @var{path}, and looks for the resulting file name in the host file
19005 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
19008 If that does not find the binary, @value{GDBN} tries removing
19009 the @samp{:} character from the drive spec, both for convenience, and,
19010 for the case of the host file system not supporting file names with
19014 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
19017 This makes it possible to have a system root that mirrors a target
19018 with more than one drive. E.g., you may want to setup your local
19019 copies of the target system shared libraries like so (note @samp{c} vs
19023 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19024 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19025 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19029 and point the system root at @file{/path/to/sysroot}, so that
19030 @value{GDBN} can find the correct copies of both
19031 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19033 If that still does not find the binary, @value{GDBN} tries
19034 removing the whole drive spec from the target file name:
19037 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19040 This last lookup makes it possible to not care about the drive name,
19041 if you don't want or need to.
19043 The @code{set solib-absolute-prefix} command is an alias for @code{set
19046 @cindex default system root
19047 @cindex @samp{--with-sysroot}
19048 You can set the default system root by using the configure-time
19049 @samp{--with-sysroot} option. If the system root is inside
19050 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19051 @samp{--exec-prefix}), then the default system root will be updated
19052 automatically if the installed @value{GDBN} is moved to a new
19055 @kindex show sysroot
19057 Display the current executable and shared library prefix.
19059 @kindex set solib-search-path
19060 @item set solib-search-path @var{path}
19061 If this variable is set, @var{path} is a colon-separated list of
19062 directories to search for shared libraries. @samp{solib-search-path}
19063 is used after @samp{sysroot} fails to locate the library, or if the
19064 path to the library is relative instead of absolute. If you want to
19065 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19066 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19067 finding your host's libraries. @samp{sysroot} is preferred; setting
19068 it to a nonexistent directory may interfere with automatic loading
19069 of shared library symbols.
19071 @kindex show solib-search-path
19072 @item show solib-search-path
19073 Display the current shared library search path.
19075 @cindex DOS file-name semantics of file names.
19076 @kindex set target-file-system-kind (unix|dos-based|auto)
19077 @kindex show target-file-system-kind
19078 @item set target-file-system-kind @var{kind}
19079 Set assumed file system kind for target reported file names.
19081 Shared library file names as reported by the target system may not
19082 make sense as is on the system @value{GDBN} is running on. For
19083 example, when remote debugging a target that has MS-DOS based file
19084 system semantics, from a Unix host, the target may be reporting to
19085 @value{GDBN} a list of loaded shared libraries with file names such as
19086 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19087 drive letters, so the @samp{c:\} prefix is not normally understood as
19088 indicating an absolute file name, and neither is the backslash
19089 normally considered a directory separator character. In that case,
19090 the native file system would interpret this whole absolute file name
19091 as a relative file name with no directory components. This would make
19092 it impossible to point @value{GDBN} at a copy of the remote target's
19093 shared libraries on the host using @code{set sysroot}, and impractical
19094 with @code{set solib-search-path}. Setting
19095 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19096 to interpret such file names similarly to how the target would, and to
19097 map them to file names valid on @value{GDBN}'s native file system
19098 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19099 to one of the supported file system kinds. In that case, @value{GDBN}
19100 tries to determine the appropriate file system variant based on the
19101 current target's operating system (@pxref{ABI, ,Configuring the
19102 Current ABI}). The supported file system settings are:
19106 Instruct @value{GDBN} to assume the target file system is of Unix
19107 kind. Only file names starting the forward slash (@samp{/}) character
19108 are considered absolute, and the directory separator character is also
19112 Instruct @value{GDBN} to assume the target file system is DOS based.
19113 File names starting with either a forward slash, or a drive letter
19114 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19115 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19116 considered directory separators.
19119 Instruct @value{GDBN} to use the file system kind associated with the
19120 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19121 This is the default.
19125 @cindex file name canonicalization
19126 @cindex base name differences
19127 When processing file names provided by the user, @value{GDBN}
19128 frequently needs to compare them to the file names recorded in the
19129 program's debug info. Normally, @value{GDBN} compares just the
19130 @dfn{base names} of the files as strings, which is reasonably fast
19131 even for very large programs. (The base name of a file is the last
19132 portion of its name, after stripping all the leading directories.)
19133 This shortcut in comparison is based upon the assumption that files
19134 cannot have more than one base name. This is usually true, but
19135 references to files that use symlinks or similar filesystem
19136 facilities violate that assumption. If your program records files
19137 using such facilities, or if you provide file names to @value{GDBN}
19138 using symlinks etc., you can set @code{basenames-may-differ} to
19139 @code{true} to instruct @value{GDBN} to completely canonicalize each
19140 pair of file names it needs to compare. This will make file-name
19141 comparisons accurate, but at a price of a significant slowdown.
19144 @item set basenames-may-differ
19145 @kindex set basenames-may-differ
19146 Set whether a source file may have multiple base names.
19148 @item show basenames-may-differ
19149 @kindex show basenames-may-differ
19150 Show whether a source file may have multiple base names.
19154 @section File Caching
19155 @cindex caching of opened files
19156 @cindex caching of bfd objects
19158 To speed up file loading, and reduce memory usage, @value{GDBN} will
19159 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19160 BFD, bfd, The Binary File Descriptor Library}. The following commands
19161 allow visibility and control of the caching behavior.
19164 @kindex maint info bfds
19165 @item maint info bfds
19166 This prints information about each @code{bfd} object that is known to
19169 @kindex maint set bfd-sharing
19170 @kindex maint show bfd-sharing
19171 @kindex bfd caching
19172 @item maint set bfd-sharing
19173 @item maint show bfd-sharing
19174 Control whether @code{bfd} objects can be shared. When sharing is
19175 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19176 than reopening the same file. Turning sharing off does not cause
19177 already shared @code{bfd} objects to be unshared, but all future files
19178 that are opened will create a new @code{bfd} object. Similarly,
19179 re-enabling sharing does not cause multiple existing @code{bfd}
19180 objects to be collapsed into a single shared @code{bfd} object.
19182 @kindex set debug bfd-cache @var{level}
19183 @kindex bfd caching
19184 @item set debug bfd-cache @var{level}
19185 Turns on debugging of the bfd cache, setting the level to @var{level}.
19187 @kindex show debug bfd-cache
19188 @kindex bfd caching
19189 @item show debug bfd-cache
19190 Show the current debugging level of the bfd cache.
19193 @node Separate Debug Files
19194 @section Debugging Information in Separate Files
19195 @cindex separate debugging information files
19196 @cindex debugging information in separate files
19197 @cindex @file{.debug} subdirectories
19198 @cindex debugging information directory, global
19199 @cindex global debugging information directories
19200 @cindex build ID, and separate debugging files
19201 @cindex @file{.build-id} directory
19203 @value{GDBN} allows you to put a program's debugging information in a
19204 file separate from the executable itself, in a way that allows
19205 @value{GDBN} to find and load the debugging information automatically.
19206 Since debugging information can be very large---sometimes larger
19207 than the executable code itself---some systems distribute debugging
19208 information for their executables in separate files, which users can
19209 install only when they need to debug a problem.
19211 @value{GDBN} supports two ways of specifying the separate debug info
19216 The executable contains a @dfn{debug link} that specifies the name of
19217 the separate debug info file. The separate debug file's name is
19218 usually @file{@var{executable}.debug}, where @var{executable} is the
19219 name of the corresponding executable file without leading directories
19220 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19221 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19222 checksum for the debug file, which @value{GDBN} uses to validate that
19223 the executable and the debug file came from the same build.
19226 The executable contains a @dfn{build ID}, a unique bit string that is
19227 also present in the corresponding debug info file. (This is supported
19228 only on some operating systems, when using the ELF or PE file formats
19229 for binary files and the @sc{gnu} Binutils.) For more details about
19230 this feature, see the description of the @option{--build-id}
19231 command-line option in @ref{Options, , Command Line Options, ld.info,
19232 The GNU Linker}. The debug info file's name is not specified
19233 explicitly by the build ID, but can be computed from the build ID, see
19237 Depending on the way the debug info file is specified, @value{GDBN}
19238 uses two different methods of looking for the debug file:
19242 For the ``debug link'' method, @value{GDBN} looks up the named file in
19243 the directory of the executable file, then in a subdirectory of that
19244 directory named @file{.debug}, and finally under each one of the global debug
19245 directories, in a subdirectory whose name is identical to the leading
19246 directories of the executable's absolute file name.
19249 For the ``build ID'' method, @value{GDBN} looks in the
19250 @file{.build-id} subdirectory of each one of the global debug directories for
19251 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19252 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19253 are the rest of the bit string. (Real build ID strings are 32 or more
19254 hex characters, not 10.)
19257 So, for example, suppose you ask @value{GDBN} to debug
19258 @file{/usr/bin/ls}, which has a debug link that specifies the
19259 file @file{ls.debug}, and a build ID whose value in hex is
19260 @code{abcdef1234}. If the list of the global debug directories includes
19261 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19262 debug information files, in the indicated order:
19266 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19268 @file{/usr/bin/ls.debug}
19270 @file{/usr/bin/.debug/ls.debug}
19272 @file{/usr/lib/debug/usr/bin/ls.debug}.
19275 @anchor{debug-file-directory}
19276 Global debugging info directories default to what is set by @value{GDBN}
19277 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19278 you can also set the global debugging info directories, and view the list
19279 @value{GDBN} is currently using.
19283 @kindex set debug-file-directory
19284 @item set debug-file-directory @var{directories}
19285 Set the directories which @value{GDBN} searches for separate debugging
19286 information files to @var{directory}. Multiple path components can be set
19287 concatenating them by a path separator.
19289 @kindex show debug-file-directory
19290 @item show debug-file-directory
19291 Show the directories @value{GDBN} searches for separate debugging
19296 @cindex @code{.gnu_debuglink} sections
19297 @cindex debug link sections
19298 A debug link is a special section of the executable file named
19299 @code{.gnu_debuglink}. The section must contain:
19303 A filename, with any leading directory components removed, followed by
19306 zero to three bytes of padding, as needed to reach the next four-byte
19307 boundary within the section, and
19309 a four-byte CRC checksum, stored in the same endianness used for the
19310 executable file itself. The checksum is computed on the debugging
19311 information file's full contents by the function given below, passing
19312 zero as the @var{crc} argument.
19315 Any executable file format can carry a debug link, as long as it can
19316 contain a section named @code{.gnu_debuglink} with the contents
19319 @cindex @code{.note.gnu.build-id} sections
19320 @cindex build ID sections
19321 The build ID is a special section in the executable file (and in other
19322 ELF binary files that @value{GDBN} may consider). This section is
19323 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19324 It contains unique identification for the built files---the ID remains
19325 the same across multiple builds of the same build tree. The default
19326 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
19327 content for the build ID string. The same section with an identical
19328 value is present in the original built binary with symbols, in its
19329 stripped variant, and in the separate debugging information file.
19331 The debugging information file itself should be an ordinary
19332 executable, containing a full set of linker symbols, sections, and
19333 debugging information. The sections of the debugging information file
19334 should have the same names, addresses, and sizes as the original file,
19335 but they need not contain any data---much like a @code{.bss} section
19336 in an ordinary executable.
19338 The @sc{gnu} binary utilities (Binutils) package includes the
19339 @samp{objcopy} utility that can produce
19340 the separated executable / debugging information file pairs using the
19341 following commands:
19344 @kbd{objcopy --only-keep-debug foo foo.debug}
19349 These commands remove the debugging
19350 information from the executable file @file{foo} and place it in the file
19351 @file{foo.debug}. You can use the first, second or both methods to link the
19356 The debug link method needs the following additional command to also leave
19357 behind a debug link in @file{foo}:
19360 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
19363 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
19364 a version of the @code{strip} command such that the command @kbd{strip foo -f
19365 foo.debug} has the same functionality as the two @code{objcopy} commands and
19366 the @code{ln -s} command above, together.
19369 Build ID gets embedded into the main executable using @code{ld --build-id} or
19370 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19371 compatibility fixes for debug files separation are present in @sc{gnu} binary
19372 utilities (Binutils) package since version 2.18.
19377 @cindex CRC algorithm definition
19378 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19379 IEEE 802.3 using the polynomial:
19381 @c TexInfo requires naked braces for multi-digit exponents for Tex
19382 @c output, but this causes HTML output to barf. HTML has to be set using
19383 @c raw commands. So we end up having to specify this equation in 2
19388 <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>
19389 + <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
19395 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19396 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19400 The function is computed byte at a time, taking the least
19401 significant bit of each byte first. The initial pattern
19402 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19403 the final result is inverted to ensure trailing zeros also affect the
19406 @emph{Note:} This is the same CRC polynomial as used in handling the
19407 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19408 However in the case of the Remote Serial Protocol, the CRC is computed
19409 @emph{most} significant bit first, and the result is not inverted, so
19410 trailing zeros have no effect on the CRC value.
19412 To complete the description, we show below the code of the function
19413 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19414 initially supplied @code{crc} argument means that an initial call to
19415 this function passing in zero will start computing the CRC using
19418 @kindex gnu_debuglink_crc32
19421 gnu_debuglink_crc32 (unsigned long crc,
19422 unsigned char *buf, size_t len)
19424 static const unsigned long crc32_table[256] =
19426 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19427 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19428 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19429 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19430 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19431 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19432 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19433 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19434 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19435 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19436 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19437 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19438 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19439 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19440 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19441 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19442 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19443 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19444 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19445 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19446 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19447 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19448 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19449 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19450 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19451 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19452 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19453 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19454 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19455 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19456 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19457 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19458 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19459 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19460 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19461 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19462 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19463 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19464 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19465 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19466 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19467 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19468 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19469 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19470 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19471 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19472 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19473 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19474 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19475 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19476 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19479 unsigned char *end;
19481 crc = ~crc & 0xffffffff;
19482 for (end = buf + len; buf < end; ++buf)
19483 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19484 return ~crc & 0xffffffff;
19489 This computation does not apply to the ``build ID'' method.
19491 @node MiniDebugInfo
19492 @section Debugging information in a special section
19493 @cindex separate debug sections
19494 @cindex @samp{.gnu_debugdata} section
19496 Some systems ship pre-built executables and libraries that have a
19497 special @samp{.gnu_debugdata} section. This feature is called
19498 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19499 is used to supply extra symbols for backtraces.
19501 The intent of this section is to provide extra minimal debugging
19502 information for use in simple backtraces. It is not intended to be a
19503 replacement for full separate debugging information (@pxref{Separate
19504 Debug Files}). The example below shows the intended use; however,
19505 @value{GDBN} does not currently put restrictions on what sort of
19506 debugging information might be included in the section.
19508 @value{GDBN} has support for this extension. If the section exists,
19509 then it is used provided that no other source of debugging information
19510 can be found, and that @value{GDBN} was configured with LZMA support.
19512 This section can be easily created using @command{objcopy} and other
19513 standard utilities:
19516 # Extract the dynamic symbols from the main binary, there is no need
19517 # to also have these in the normal symbol table.
19518 nm -D @var{binary} --format=posix --defined-only \
19519 | awk '@{ print $1 @}' | sort > dynsyms
19521 # Extract all the text (i.e. function) symbols from the debuginfo.
19522 # (Note that we actually also accept "D" symbols, for the benefit
19523 # of platforms like PowerPC64 that use function descriptors.)
19524 nm @var{binary} --format=posix --defined-only \
19525 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19528 # Keep all the function symbols not already in the dynamic symbol
19530 comm -13 dynsyms funcsyms > keep_symbols
19532 # Separate full debug info into debug binary.
19533 objcopy --only-keep-debug @var{binary} debug
19535 # Copy the full debuginfo, keeping only a minimal set of symbols and
19536 # removing some unnecessary sections.
19537 objcopy -S --remove-section .gdb_index --remove-section .comment \
19538 --keep-symbols=keep_symbols debug mini_debuginfo
19540 # Drop the full debug info from the original binary.
19541 strip --strip-all -R .comment @var{binary}
19543 # Inject the compressed data into the .gnu_debugdata section of the
19546 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19550 @section Index Files Speed Up @value{GDBN}
19551 @cindex index files
19552 @cindex @samp{.gdb_index} section
19554 When @value{GDBN} finds a symbol file, it scans the symbols in the
19555 file in order to construct an internal symbol table. This lets most
19556 @value{GDBN} operations work quickly---at the cost of a delay early
19557 on. For large programs, this delay can be quite lengthy, so
19558 @value{GDBN} provides a way to build an index, which speeds up
19561 The index is stored as a section in the symbol file. @value{GDBN} can
19562 write the index to a file, then you can put it into the symbol file
19563 using @command{objcopy}.
19565 To create an index file, use the @code{save gdb-index} command:
19568 @item save gdb-index [-dwarf-5] @var{directory}
19569 @kindex save gdb-index
19570 Create index files for all symbol files currently known by
19571 @value{GDBN}. For each known @var{symbol-file}, this command by
19572 default creates it produces a single file
19573 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
19574 the @option{-dwarf-5} option, it produces 2 files:
19575 @file{@var{symbol-file}.debug_names} and
19576 @file{@var{symbol-file}.debug_str}. The files are created in the
19577 given @var{directory}.
19580 Once you have created an index file you can merge it into your symbol
19581 file, here named @file{symfile}, using @command{objcopy}:
19584 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19585 --set-section-flags .gdb_index=readonly symfile symfile
19588 Or for @code{-dwarf-5}:
19591 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
19592 $ cat symfile.debug_str >>symfile.debug_str.new
19593 $ objcopy --add-section .debug_names=symfile.gdb-index \
19594 --set-section-flags .debug_names=readonly \
19595 --update-section .debug_str=symfile.debug_str.new symfile symfile
19598 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19599 sections that have been deprecated. Usually they are deprecated because
19600 they are missing a new feature or have performance issues.
19601 To tell @value{GDBN} to use a deprecated index section anyway
19602 specify @code{set use-deprecated-index-sections on}.
19603 The default is @code{off}.
19604 This can speed up startup, but may result in some functionality being lost.
19605 @xref{Index Section Format}.
19607 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19608 must be done before gdb reads the file. The following will not work:
19611 $ gdb -ex "set use-deprecated-index-sections on" <program>
19614 Instead you must do, for example,
19617 $ gdb -iex "set use-deprecated-index-sections on" <program>
19620 There are currently some limitation on indices. They only work when
19621 for DWARF debugging information, not stabs. And, they do not
19622 currently work for programs using Ada.
19624 @node Symbol Errors
19625 @section Errors Reading Symbol Files
19627 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19628 such as symbol types it does not recognize, or known bugs in compiler
19629 output. By default, @value{GDBN} does not notify you of such problems, since
19630 they are relatively common and primarily of interest to people
19631 debugging compilers. If you are interested in seeing information
19632 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19633 only one message about each such type of problem, no matter how many
19634 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19635 to see how many times the problems occur, with the @code{set
19636 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19639 The messages currently printed, and their meanings, include:
19642 @item inner block not inside outer block in @var{symbol}
19644 The symbol information shows where symbol scopes begin and end
19645 (such as at the start of a function or a block of statements). This
19646 error indicates that an inner scope block is not fully contained
19647 in its outer scope blocks.
19649 @value{GDBN} circumvents the problem by treating the inner block as if it had
19650 the same scope as the outer block. In the error message, @var{symbol}
19651 may be shown as ``@code{(don't know)}'' if the outer block is not a
19654 @item block at @var{address} out of order
19656 The symbol information for symbol scope blocks should occur in
19657 order of increasing addresses. This error indicates that it does not
19660 @value{GDBN} does not circumvent this problem, and has trouble
19661 locating symbols in the source file whose symbols it is reading. (You
19662 can often determine what source file is affected by specifying
19663 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19666 @item bad block start address patched
19668 The symbol information for a symbol scope block has a start address
19669 smaller than the address of the preceding source line. This is known
19670 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19672 @value{GDBN} circumvents the problem by treating the symbol scope block as
19673 starting on the previous source line.
19675 @item bad string table offset in symbol @var{n}
19678 Symbol number @var{n} contains a pointer into the string table which is
19679 larger than the size of the string table.
19681 @value{GDBN} circumvents the problem by considering the symbol to have the
19682 name @code{foo}, which may cause other problems if many symbols end up
19685 @item unknown symbol type @code{0x@var{nn}}
19687 The symbol information contains new data types that @value{GDBN} does
19688 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19689 uncomprehended information, in hexadecimal.
19691 @value{GDBN} circumvents the error by ignoring this symbol information.
19692 This usually allows you to debug your program, though certain symbols
19693 are not accessible. If you encounter such a problem and feel like
19694 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19695 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19696 and examine @code{*bufp} to see the symbol.
19698 @item stub type has NULL name
19700 @value{GDBN} could not find the full definition for a struct or class.
19702 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19703 The symbol information for a C@t{++} member function is missing some
19704 information that recent versions of the compiler should have output for
19707 @item info mismatch between compiler and debugger
19709 @value{GDBN} could not parse a type specification output by the compiler.
19714 @section GDB Data Files
19716 @cindex prefix for data files
19717 @value{GDBN} will sometimes read an auxiliary data file. These files
19718 are kept in a directory known as the @dfn{data directory}.
19720 You can set the data directory's name, and view the name @value{GDBN}
19721 is currently using.
19724 @kindex set data-directory
19725 @item set data-directory @var{directory}
19726 Set the directory which @value{GDBN} searches for auxiliary data files
19727 to @var{directory}.
19729 @kindex show data-directory
19730 @item show data-directory
19731 Show the directory @value{GDBN} searches for auxiliary data files.
19734 @cindex default data directory
19735 @cindex @samp{--with-gdb-datadir}
19736 You can set the default data directory by using the configure-time
19737 @samp{--with-gdb-datadir} option. If the data directory is inside
19738 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19739 @samp{--exec-prefix}), then the default data directory will be updated
19740 automatically if the installed @value{GDBN} is moved to a new
19743 The data directory may also be specified with the
19744 @code{--data-directory} command line option.
19745 @xref{Mode Options}.
19748 @chapter Specifying a Debugging Target
19750 @cindex debugging target
19751 A @dfn{target} is the execution environment occupied by your program.
19753 Often, @value{GDBN} runs in the same host environment as your program;
19754 in that case, the debugging target is specified as a side effect when
19755 you use the @code{file} or @code{core} commands. When you need more
19756 flexibility---for example, running @value{GDBN} on a physically separate
19757 host, or controlling a standalone system over a serial port or a
19758 realtime system over a TCP/IP connection---you can use the @code{target}
19759 command to specify one of the target types configured for @value{GDBN}
19760 (@pxref{Target Commands, ,Commands for Managing Targets}).
19762 @cindex target architecture
19763 It is possible to build @value{GDBN} for several different @dfn{target
19764 architectures}. When @value{GDBN} is built like that, you can choose
19765 one of the available architectures with the @kbd{set architecture}
19769 @kindex set architecture
19770 @kindex show architecture
19771 @item set architecture @var{arch}
19772 This command sets the current target architecture to @var{arch}. The
19773 value of @var{arch} can be @code{"auto"}, in addition to one of the
19774 supported architectures.
19776 @item show architecture
19777 Show the current target architecture.
19779 @item set processor
19781 @kindex set processor
19782 @kindex show processor
19783 These are alias commands for, respectively, @code{set architecture}
19784 and @code{show architecture}.
19788 * Active Targets:: Active targets
19789 * Target Commands:: Commands for managing targets
19790 * Byte Order:: Choosing target byte order
19793 @node Active Targets
19794 @section Active Targets
19796 @cindex stacking targets
19797 @cindex active targets
19798 @cindex multiple targets
19800 There are multiple classes of targets such as: processes, executable files or
19801 recording sessions. Core files belong to the process class, making core file
19802 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19803 on multiple active targets, one in each class. This allows you to (for
19804 example) start a process and inspect its activity, while still having access to
19805 the executable file after the process finishes. Or if you start process
19806 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19807 presented a virtual layer of the recording target, while the process target
19808 remains stopped at the chronologically last point of the process execution.
19810 Use the @code{core-file} and @code{exec-file} commands to select a new core
19811 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19812 specify as a target a process that is already running, use the @code{attach}
19813 command (@pxref{Attach, ,Debugging an Already-running Process}).
19815 @node Target Commands
19816 @section Commands for Managing Targets
19819 @item target @var{type} @var{parameters}
19820 Connects the @value{GDBN} host environment to a target machine or
19821 process. A target is typically a protocol for talking to debugging
19822 facilities. You use the argument @var{type} to specify the type or
19823 protocol of the target machine.
19825 Further @var{parameters} are interpreted by the target protocol, but
19826 typically include things like device names or host names to connect
19827 with, process numbers, and baud rates.
19829 The @code{target} command does not repeat if you press @key{RET} again
19830 after executing the command.
19832 @kindex help target
19834 Displays the names of all targets available. To display targets
19835 currently selected, use either @code{info target} or @code{info files}
19836 (@pxref{Files, ,Commands to Specify Files}).
19838 @item help target @var{name}
19839 Describe a particular target, including any parameters necessary to
19842 @kindex set gnutarget
19843 @item set gnutarget @var{args}
19844 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19845 knows whether it is reading an @dfn{executable},
19846 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19847 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19848 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19851 @emph{Warning:} To specify a file format with @code{set gnutarget},
19852 you must know the actual BFD name.
19856 @xref{Files, , Commands to Specify Files}.
19858 @kindex show gnutarget
19859 @item show gnutarget
19860 Use the @code{show gnutarget} command to display what file format
19861 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19862 @value{GDBN} will determine the file format for each file automatically,
19863 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19866 @cindex common targets
19867 Here are some common targets (available, or not, depending on the GDB
19872 @item target exec @var{program}
19873 @cindex executable file target
19874 An executable file. @samp{target exec @var{program}} is the same as
19875 @samp{exec-file @var{program}}.
19877 @item target core @var{filename}
19878 @cindex core dump file target
19879 A core dump file. @samp{target core @var{filename}} is the same as
19880 @samp{core-file @var{filename}}.
19882 @item target remote @var{medium}
19883 @cindex remote target
19884 A remote system connected to @value{GDBN} via a serial line or network
19885 connection. This command tells @value{GDBN} to use its own remote
19886 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19888 For example, if you have a board connected to @file{/dev/ttya} on the
19889 machine running @value{GDBN}, you could say:
19892 target remote /dev/ttya
19895 @code{target remote} supports the @code{load} command. This is only
19896 useful if you have some other way of getting the stub to the target
19897 system, and you can put it somewhere in memory where it won't get
19898 clobbered by the download.
19900 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19901 @cindex built-in simulator target
19902 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19910 works; however, you cannot assume that a specific memory map, device
19911 drivers, or even basic I/O is available, although some simulators do
19912 provide these. For info about any processor-specific simulator details,
19913 see the appropriate section in @ref{Embedded Processors, ,Embedded
19916 @item target native
19917 @cindex native target
19918 Setup for local/native process debugging. Useful to make the
19919 @code{run} command spawn native processes (likewise @code{attach},
19920 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19921 (@pxref{set auto-connect-native-target}).
19925 Different targets are available on different configurations of @value{GDBN};
19926 your configuration may have more or fewer targets.
19928 Many remote targets require you to download the executable's code once
19929 you've successfully established a connection. You may wish to control
19930 various aspects of this process.
19935 @kindex set hash@r{, for remote monitors}
19936 @cindex hash mark while downloading
19937 This command controls whether a hash mark @samp{#} is displayed while
19938 downloading a file to the remote monitor. If on, a hash mark is
19939 displayed after each S-record is successfully downloaded to the
19943 @kindex show hash@r{, for remote monitors}
19944 Show the current status of displaying the hash mark.
19946 @item set debug monitor
19947 @kindex set debug monitor
19948 @cindex display remote monitor communications
19949 Enable or disable display of communications messages between
19950 @value{GDBN} and the remote monitor.
19952 @item show debug monitor
19953 @kindex show debug monitor
19954 Show the current status of displaying communications between
19955 @value{GDBN} and the remote monitor.
19960 @kindex load @var{filename} @var{offset}
19961 @item load @var{filename} @var{offset}
19963 Depending on what remote debugging facilities are configured into
19964 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19965 is meant to make @var{filename} (an executable) available for debugging
19966 on the remote system---by downloading, or dynamic linking, for example.
19967 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19968 the @code{add-symbol-file} command.
19970 If your @value{GDBN} does not have a @code{load} command, attempting to
19971 execute it gets the error message ``@code{You can't do that when your
19972 target is @dots{}}''
19974 The file is loaded at whatever address is specified in the executable.
19975 For some object file formats, you can specify the load address when you
19976 link the program; for other formats, like a.out, the object file format
19977 specifies a fixed address.
19978 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19980 It is also possible to tell @value{GDBN} to load the executable file at a
19981 specific offset described by the optional argument @var{offset}. When
19982 @var{offset} is provided, @var{filename} must also be provided.
19984 Depending on the remote side capabilities, @value{GDBN} may be able to
19985 load programs into flash memory.
19987 @code{load} does not repeat if you press @key{RET} again after using it.
19992 @kindex flash-erase
19994 @anchor{flash-erase}
19996 Erases all known flash memory regions on the target.
20001 @section Choosing Target Byte Order
20003 @cindex choosing target byte order
20004 @cindex target byte order
20006 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
20007 offer the ability to run either big-endian or little-endian byte
20008 orders. Usually the executable or symbol will include a bit to
20009 designate the endian-ness, and you will not need to worry about
20010 which to use. However, you may still find it useful to adjust
20011 @value{GDBN}'s idea of processor endian-ness manually.
20015 @item set endian big
20016 Instruct @value{GDBN} to assume the target is big-endian.
20018 @item set endian little
20019 Instruct @value{GDBN} to assume the target is little-endian.
20021 @item set endian auto
20022 Instruct @value{GDBN} to use the byte order associated with the
20026 Display @value{GDBN}'s current idea of the target byte order.
20030 Note that these commands merely adjust interpretation of symbolic
20031 data on the host, and that they have absolutely no effect on the
20035 @node Remote Debugging
20036 @chapter Debugging Remote Programs
20037 @cindex remote debugging
20039 If you are trying to debug a program running on a machine that cannot run
20040 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20041 For example, you might use remote debugging on an operating system kernel,
20042 or on a small system which does not have a general purpose operating system
20043 powerful enough to run a full-featured debugger.
20045 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20046 to make this work with particular debugging targets. In addition,
20047 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20048 but not specific to any particular target system) which you can use if you
20049 write the remote stubs---the code that runs on the remote system to
20050 communicate with @value{GDBN}.
20052 Other remote targets may be available in your
20053 configuration of @value{GDBN}; use @code{help target} to list them.
20056 * Connecting:: Connecting to a remote target
20057 * File Transfer:: Sending files to a remote system
20058 * Server:: Using the gdbserver program
20059 * Remote Configuration:: Remote configuration
20060 * Remote Stub:: Implementing a remote stub
20064 @section Connecting to a Remote Target
20065 @cindex remote debugging, connecting
20066 @cindex @code{gdbserver}, connecting
20067 @cindex remote debugging, types of connections
20068 @cindex @code{gdbserver}, types of connections
20069 @cindex @code{gdbserver}, @code{target remote} mode
20070 @cindex @code{gdbserver}, @code{target extended-remote} mode
20072 This section describes how to connect to a remote target, including the
20073 types of connections and their differences, how to set up executable and
20074 symbol files on the host and target, and the commands used for
20075 connecting to and disconnecting from the remote target.
20077 @subsection Types of Remote Connections
20079 @value{GDBN} supports two types of remote connections, @code{target remote}
20080 mode and @code{target extended-remote} mode. Note that many remote targets
20081 support only @code{target remote} mode. There are several major
20082 differences between the two types of connections, enumerated here:
20086 @cindex remote debugging, detach and program exit
20087 @item Result of detach or program exit
20088 @strong{With target remote mode:} When the debugged program exits or you
20089 detach from it, @value{GDBN} disconnects from the target. When using
20090 @code{gdbserver}, @code{gdbserver} will exit.
20092 @strong{With target extended-remote mode:} When the debugged program exits or
20093 you detach from it, @value{GDBN} remains connected to the target, even
20094 though no program is running. You can rerun the program, attach to a
20095 running program, or use @code{monitor} commands specific to the target.
20097 When using @code{gdbserver} in this case, it does not exit unless it was
20098 invoked using the @option{--once} option. If the @option{--once} option
20099 was not used, you can ask @code{gdbserver} to exit using the
20100 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20102 @item Specifying the program to debug
20103 For both connection types you use the @code{file} command to specify the
20104 program on the host system. If you are using @code{gdbserver} there are
20105 some differences in how to specify the location of the program on the
20108 @strong{With target remote mode:} You must either specify the program to debug
20109 on the @code{gdbserver} command line or use the @option{--attach} option
20110 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20112 @cindex @option{--multi}, @code{gdbserver} option
20113 @strong{With target extended-remote mode:} You may specify the program to debug
20114 on the @code{gdbserver} command line, or you can load the program or attach
20115 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20117 @anchor{--multi Option in Types of Remote Connnections}
20118 You can start @code{gdbserver} without supplying an initial command to run
20119 or process ID to attach. To do this, use the @option{--multi} command line
20120 option. Then you can connect using @code{target extended-remote} and start
20121 the program you want to debug (see below for details on using the
20122 @code{run} command in this scenario). Note that the conditions under which
20123 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20124 (@code{target remote} or @code{target extended-remote}). The
20125 @option{--multi} option to @code{gdbserver} has no influence on that.
20127 @item The @code{run} command
20128 @strong{With target remote mode:} The @code{run} command is not
20129 supported. Once a connection has been established, you can use all
20130 the usual @value{GDBN} commands to examine and change data. The
20131 remote program is already running, so you can use commands like
20132 @kbd{step} and @kbd{continue}.
20134 @strong{With target extended-remote mode:} The @code{run} command is
20135 supported. The @code{run} command uses the value set by
20136 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20137 the program to run. Command line arguments are supported, except for
20138 wildcard expansion and I/O redirection (@pxref{Arguments}).
20140 If you specify the program to debug on the command line, then the
20141 @code{run} command is not required to start execution, and you can
20142 resume using commands like @kbd{step} and @kbd{continue} as with
20143 @code{target remote} mode.
20145 @anchor{Attaching in Types of Remote Connections}
20147 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20148 not supported. To attach to a running program using @code{gdbserver}, you
20149 must use the @option{--attach} option (@pxref{Running gdbserver}).
20151 @strong{With target extended-remote mode:} To attach to a running program,
20152 you may use the @code{attach} command after the connection has been
20153 established. If you are using @code{gdbserver}, you may also invoke
20154 @code{gdbserver} using the @option{--attach} option
20155 (@pxref{Running gdbserver}).
20159 @anchor{Host and target files}
20160 @subsection Host and Target Files
20161 @cindex remote debugging, symbol files
20162 @cindex symbol files, remote debugging
20164 @value{GDBN}, running on the host, needs access to symbol and debugging
20165 information for your program running on the target. This requires
20166 access to an unstripped copy of your program, and possibly any associated
20167 symbol files. Note that this section applies equally to both @code{target
20168 remote} mode and @code{target extended-remote} mode.
20170 Some remote targets (@pxref{qXfer executable filename read}, and
20171 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20172 the same connection used to communicate with @value{GDBN}. With such a
20173 target, if the remote program is unstripped, the only command you need is
20174 @code{target remote} (or @code{target extended-remote}).
20176 If the remote program is stripped, or the target does not support remote
20177 program file access, start up @value{GDBN} using the name of the local
20178 unstripped copy of your program as the first argument, or use the
20179 @code{file} command. Use @code{set sysroot} to specify the location (on
20180 the host) of target libraries (unless your @value{GDBN} was compiled with
20181 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20182 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20185 The symbol file and target libraries must exactly match the executable
20186 and libraries on the target, with one exception: the files on the host
20187 system should not be stripped, even if the files on the target system
20188 are. Mismatched or missing files will lead to confusing results
20189 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20190 files may also prevent @code{gdbserver} from debugging multi-threaded
20193 @subsection Remote Connection Commands
20194 @cindex remote connection commands
20195 @value{GDBN} can communicate with the target over a serial line, or
20196 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20197 each case, @value{GDBN} uses the same protocol for debugging your
20198 program; only the medium carrying the debugging packets varies. The
20199 @code{target remote} and @code{target extended-remote} commands
20200 establish a connection to the target. Both commands accept the same
20201 arguments, which indicate the medium to use:
20205 @item target remote @var{serial-device}
20206 @itemx target extended-remote @var{serial-device}
20207 @cindex serial line, @code{target remote}
20208 Use @var{serial-device} to communicate with the target. For example,
20209 to use a serial line connected to the device named @file{/dev/ttyb}:
20212 target remote /dev/ttyb
20215 If you're using a serial line, you may want to give @value{GDBN} the
20216 @samp{--baud} option, or use the @code{set serial baud} command
20217 (@pxref{Remote Configuration, set serial baud}) before the
20218 @code{target} command.
20220 @item target remote @code{@var{host}:@var{port}}
20221 @itemx target remote @code{tcp:@var{host}:@var{port}}
20222 @itemx target extended-remote @code{@var{host}:@var{port}}
20223 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
20224 @cindex @acronym{TCP} port, @code{target remote}
20225 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
20226 The @var{host} may be either a host name or a numeric @acronym{IP}
20227 address; @var{port} must be a decimal number. The @var{host} could be
20228 the target machine itself, if it is directly connected to the net, or
20229 it might be a terminal server which in turn has a serial line to the
20232 For example, to connect to port 2828 on a terminal server named
20236 target remote manyfarms:2828
20239 If your remote target is actually running on the same machine as your
20240 debugger session (e.g.@: a simulator for your target running on the
20241 same host), you can omit the hostname. For example, to connect to
20242 port 1234 on your local machine:
20245 target remote :1234
20249 Note that the colon is still required here.
20251 @item target remote @code{udp:@var{host}:@var{port}}
20252 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
20253 @cindex @acronym{UDP} port, @code{target remote}
20254 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
20255 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
20258 target remote udp:manyfarms:2828
20261 When using a @acronym{UDP} connection for remote debugging, you should
20262 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
20263 can silently drop packets on busy or unreliable networks, which will
20264 cause havoc with your debugging session.
20266 @item target remote | @var{command}
20267 @itemx target extended-remote | @var{command}
20268 @cindex pipe, @code{target remote} to
20269 Run @var{command} in the background and communicate with it using a
20270 pipe. The @var{command} is a shell command, to be parsed and expanded
20271 by the system's command shell, @code{/bin/sh}; it should expect remote
20272 protocol packets on its standard input, and send replies on its
20273 standard output. You could use this to run a stand-alone simulator
20274 that speaks the remote debugging protocol, to make net connections
20275 using programs like @code{ssh}, or for other similar tricks.
20277 If @var{command} closes its standard output (perhaps by exiting),
20278 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
20279 program has already exited, this will have no effect.)
20283 @cindex interrupting remote programs
20284 @cindex remote programs, interrupting
20285 Whenever @value{GDBN} is waiting for the remote program, if you type the
20286 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
20287 program. This may or may not succeed, depending in part on the hardware
20288 and the serial drivers the remote system uses. If you type the
20289 interrupt character once again, @value{GDBN} displays this prompt:
20292 Interrupted while waiting for the program.
20293 Give up (and stop debugging it)? (y or n)
20296 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
20297 the remote debugging session. (If you decide you want to try again later,
20298 you can use @kbd{target remote} again to connect once more.) If you type
20299 @kbd{n}, @value{GDBN} goes back to waiting.
20301 In @code{target extended-remote} mode, typing @kbd{n} will leave
20302 @value{GDBN} connected to the target.
20305 @kindex detach (remote)
20307 When you have finished debugging the remote program, you can use the
20308 @code{detach} command to release it from @value{GDBN} control.
20309 Detaching from the target normally resumes its execution, but the results
20310 will depend on your particular remote stub. After the @code{detach}
20311 command in @code{target remote} mode, @value{GDBN} is free to connect to
20312 another target. In @code{target extended-remote} mode, @value{GDBN} is
20313 still connected to the target.
20317 The @code{disconnect} command closes the connection to the target, and
20318 the target is generally not resumed. It will wait for @value{GDBN}
20319 (this instance or another one) to connect and continue debugging. After
20320 the @code{disconnect} command, @value{GDBN} is again free to connect to
20323 @cindex send command to remote monitor
20324 @cindex extend @value{GDBN} for remote targets
20325 @cindex add new commands for external monitor
20327 @item monitor @var{cmd}
20328 This command allows you to send arbitrary commands directly to the
20329 remote monitor. Since @value{GDBN} doesn't care about the commands it
20330 sends like this, this command is the way to extend @value{GDBN}---you
20331 can add new commands that only the external monitor will understand
20335 @node File Transfer
20336 @section Sending files to a remote system
20337 @cindex remote target, file transfer
20338 @cindex file transfer
20339 @cindex sending files to remote systems
20341 Some remote targets offer the ability to transfer files over the same
20342 connection used to communicate with @value{GDBN}. This is convenient
20343 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
20344 running @code{gdbserver} over a network interface. For other targets,
20345 e.g.@: embedded devices with only a single serial port, this may be
20346 the only way to upload or download files.
20348 Not all remote targets support these commands.
20352 @item remote put @var{hostfile} @var{targetfile}
20353 Copy file @var{hostfile} from the host system (the machine running
20354 @value{GDBN}) to @var{targetfile} on the target system.
20357 @item remote get @var{targetfile} @var{hostfile}
20358 Copy file @var{targetfile} from the target system to @var{hostfile}
20359 on the host system.
20361 @kindex remote delete
20362 @item remote delete @var{targetfile}
20363 Delete @var{targetfile} from the target system.
20368 @section Using the @code{gdbserver} Program
20371 @cindex remote connection without stubs
20372 @code{gdbserver} is a control program for Unix-like systems, which
20373 allows you to connect your program with a remote @value{GDBN} via
20374 @code{target remote} or @code{target extended-remote}---but without
20375 linking in the usual debugging stub.
20377 @code{gdbserver} is not a complete replacement for the debugging stubs,
20378 because it requires essentially the same operating-system facilities
20379 that @value{GDBN} itself does. In fact, a system that can run
20380 @code{gdbserver} to connect to a remote @value{GDBN} could also run
20381 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
20382 because it is a much smaller program than @value{GDBN} itself. It is
20383 also easier to port than all of @value{GDBN}, so you may be able to get
20384 started more quickly on a new system by using @code{gdbserver}.
20385 Finally, if you develop code for real-time systems, you may find that
20386 the tradeoffs involved in real-time operation make it more convenient to
20387 do as much development work as possible on another system, for example
20388 by cross-compiling. You can use @code{gdbserver} to make a similar
20389 choice for debugging.
20391 @value{GDBN} and @code{gdbserver} communicate via either a serial line
20392 or a TCP connection, using the standard @value{GDBN} remote serial
20396 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20397 Do not run @code{gdbserver} connected to any public network; a
20398 @value{GDBN} connection to @code{gdbserver} provides access to the
20399 target system with the same privileges as the user running
20403 @anchor{Running gdbserver}
20404 @subsection Running @code{gdbserver}
20405 @cindex arguments, to @code{gdbserver}
20406 @cindex @code{gdbserver}, command-line arguments
20408 Run @code{gdbserver} on the target system. You need a copy of the
20409 program you want to debug, including any libraries it requires.
20410 @code{gdbserver} does not need your program's symbol table, so you can
20411 strip the program if necessary to save space. @value{GDBN} on the host
20412 system does all the symbol handling.
20414 To use the server, you must tell it how to communicate with @value{GDBN};
20415 the name of your program; and the arguments for your program. The usual
20419 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20422 @var{comm} is either a device name (to use a serial line), or a TCP
20423 hostname and portnumber, or @code{-} or @code{stdio} to use
20424 stdin/stdout of @code{gdbserver}.
20425 For example, to debug Emacs with the argument
20426 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20430 target> gdbserver /dev/com1 emacs foo.txt
20433 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20436 To use a TCP connection instead of a serial line:
20439 target> gdbserver host:2345 emacs foo.txt
20442 The only difference from the previous example is the first argument,
20443 specifying that you are communicating with the host @value{GDBN} via
20444 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20445 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20446 (Currently, the @samp{host} part is ignored.) You can choose any number
20447 you want for the port number as long as it does not conflict with any
20448 TCP ports already in use on the target system (for example, @code{23} is
20449 reserved for @code{telnet}).@footnote{If you choose a port number that
20450 conflicts with another service, @code{gdbserver} prints an error message
20451 and exits.} You must use the same port number with the host @value{GDBN}
20452 @code{target remote} command.
20454 The @code{stdio} connection is useful when starting @code{gdbserver}
20458 (gdb) target remote | ssh -T hostname gdbserver - hello
20461 The @samp{-T} option to ssh is provided because we don't need a remote pty,
20462 and we don't want escape-character handling. Ssh does this by default when
20463 a command is provided, the flag is provided to make it explicit.
20464 You could elide it if you want to.
20466 Programs started with stdio-connected gdbserver have @file{/dev/null} for
20467 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
20468 display through a pipe connected to gdbserver.
20469 Both @code{stdout} and @code{stderr} use the same pipe.
20471 @anchor{Attaching to a program}
20472 @subsubsection Attaching to a Running Program
20473 @cindex attach to a program, @code{gdbserver}
20474 @cindex @option{--attach}, @code{gdbserver} option
20476 On some targets, @code{gdbserver} can also attach to running programs.
20477 This is accomplished via the @code{--attach} argument. The syntax is:
20480 target> gdbserver --attach @var{comm} @var{pid}
20483 @var{pid} is the process ID of a currently running process. It isn't
20484 necessary to point @code{gdbserver} at a binary for the running process.
20486 In @code{target extended-remote} mode, you can also attach using the
20487 @value{GDBN} attach command
20488 (@pxref{Attaching in Types of Remote Connections}).
20491 You can debug processes by name instead of process ID if your target has the
20492 @code{pidof} utility:
20495 target> gdbserver --attach @var{comm} `pidof @var{program}`
20498 In case more than one copy of @var{program} is running, or @var{program}
20499 has multiple threads, most versions of @code{pidof} support the
20500 @code{-s} option to only return the first process ID.
20502 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
20504 This section applies only when @code{gdbserver} is run to listen on a TCP
20507 @code{gdbserver} normally terminates after all of its debugged processes have
20508 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
20509 extended-remote}, @code{gdbserver} stays running even with no processes left.
20510 @value{GDBN} normally terminates the spawned debugged process on its exit,
20511 which normally also terminates @code{gdbserver} in the @kbd{target remote}
20512 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
20513 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
20514 stays running even in the @kbd{target remote} mode.
20516 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
20517 Such reconnecting is useful for features like @ref{disconnected tracing}. For
20518 completeness, at most one @value{GDBN} can be connected at a time.
20520 @cindex @option{--once}, @code{gdbserver} option
20521 By default, @code{gdbserver} keeps the listening TCP port open, so that
20522 subsequent connections are possible. However, if you start @code{gdbserver}
20523 with the @option{--once} option, it will stop listening for any further
20524 connection attempts after connecting to the first @value{GDBN} session. This
20525 means no further connections to @code{gdbserver} will be possible after the
20526 first one. It also means @code{gdbserver} will terminate after the first
20527 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20528 connections and even in the @kbd{target extended-remote} mode. The
20529 @option{--once} option allows reusing the same port number for connecting to
20530 multiple instances of @code{gdbserver} running on the same host, since each
20531 instance closes its port after the first connection.
20533 @anchor{Other Command-Line Arguments for gdbserver}
20534 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20536 You can use the @option{--multi} option to start @code{gdbserver} without
20537 specifying a program to debug or a process to attach to. Then you can
20538 attach in @code{target extended-remote} mode and run or attach to a
20539 program. For more information,
20540 @pxref{--multi Option in Types of Remote Connnections}.
20542 @cindex @option{--debug}, @code{gdbserver} option
20543 The @option{--debug} option tells @code{gdbserver} to display extra
20544 status information about the debugging process.
20545 @cindex @option{--remote-debug}, @code{gdbserver} option
20546 The @option{--remote-debug} option tells @code{gdbserver} to display
20547 remote protocol debug output. These options are intended for
20548 @code{gdbserver} development and for bug reports to the developers.
20550 @cindex @option{--debug-format}, @code{gdbserver} option
20551 The @option{--debug-format=option1[,option2,...]} option tells
20552 @code{gdbserver} to include additional information in each output.
20553 Possible options are:
20557 Turn off all extra information in debugging output.
20559 Turn on all extra information in debugging output.
20561 Include a timestamp in each line of debugging output.
20564 Options are processed in order. Thus, for example, if @option{none}
20565 appears last then no additional information is added to debugging output.
20567 @cindex @option{--wrapper}, @code{gdbserver} option
20568 The @option{--wrapper} option specifies a wrapper to launch programs
20569 for debugging. The option should be followed by the name of the
20570 wrapper, then any command-line arguments to pass to the wrapper, then
20571 @kbd{--} indicating the end of the wrapper arguments.
20573 @code{gdbserver} runs the specified wrapper program with a combined
20574 command line including the wrapper arguments, then the name of the
20575 program to debug, then any arguments to the program. The wrapper
20576 runs until it executes your program, and then @value{GDBN} gains control.
20578 You can use any program that eventually calls @code{execve} with
20579 its arguments as a wrapper. Several standard Unix utilities do
20580 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20581 with @code{exec "$@@"} will also work.
20583 For example, you can use @code{env} to pass an environment variable to
20584 the debugged program, without setting the variable in @code{gdbserver}'s
20588 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20591 @cindex @option{--selftest}
20592 The @option{--selftest} option runs the self tests in @code{gdbserver}:
20595 $ gdbserver --selftest
20596 Ran 2 unit tests, 0 failed
20599 These tests are disabled in release.
20600 @subsection Connecting to @code{gdbserver}
20602 The basic procedure for connecting to the remote target is:
20606 Run @value{GDBN} on the host system.
20609 Make sure you have the necessary symbol files
20610 (@pxref{Host and target files}).
20611 Load symbols for your application using the @code{file} command before you
20612 connect. Use @code{set sysroot} to locate target libraries (unless your
20613 @value{GDBN} was compiled with the correct sysroot using
20614 @code{--with-sysroot}).
20617 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20618 For TCP connections, you must start up @code{gdbserver} prior to using
20619 the @code{target} command. Otherwise you may get an error whose
20620 text depends on the host system, but which usually looks something like
20621 @samp{Connection refused}. Don't use the @code{load}
20622 command in @value{GDBN} when using @code{target remote} mode, since the
20623 program is already on the target.
20627 @anchor{Monitor Commands for gdbserver}
20628 @subsection Monitor Commands for @code{gdbserver}
20629 @cindex monitor commands, for @code{gdbserver}
20631 During a @value{GDBN} session using @code{gdbserver}, you can use the
20632 @code{monitor} command to send special requests to @code{gdbserver}.
20633 Here are the available commands.
20637 List the available monitor commands.
20639 @item monitor set debug 0
20640 @itemx monitor set debug 1
20641 Disable or enable general debugging messages.
20643 @item monitor set remote-debug 0
20644 @itemx monitor set remote-debug 1
20645 Disable or enable specific debugging messages associated with the remote
20646 protocol (@pxref{Remote Protocol}).
20648 @item monitor set debug-format option1@r{[},option2,...@r{]}
20649 Specify additional text to add to debugging messages.
20650 Possible options are:
20654 Turn off all extra information in debugging output.
20656 Turn on all extra information in debugging output.
20658 Include a timestamp in each line of debugging output.
20661 Options are processed in order. Thus, for example, if @option{none}
20662 appears last then no additional information is added to debugging output.
20664 @item monitor set libthread-db-search-path [PATH]
20665 @cindex gdbserver, search path for @code{libthread_db}
20666 When this command is issued, @var{path} is a colon-separated list of
20667 directories to search for @code{libthread_db} (@pxref{Threads,,set
20668 libthread-db-search-path}). If you omit @var{path},
20669 @samp{libthread-db-search-path} will be reset to its default value.
20671 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20672 not supported in @code{gdbserver}.
20675 Tell gdbserver to exit immediately. This command should be followed by
20676 @code{disconnect} to close the debugging session. @code{gdbserver} will
20677 detach from any attached processes and kill any processes it created.
20678 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20679 of a multi-process mode debug session.
20683 @subsection Tracepoints support in @code{gdbserver}
20684 @cindex tracepoints support in @code{gdbserver}
20686 On some targets, @code{gdbserver} supports tracepoints, fast
20687 tracepoints and static tracepoints.
20689 For fast or static tracepoints to work, a special library called the
20690 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20691 This library is built and distributed as an integral part of
20692 @code{gdbserver}. In addition, support for static tracepoints
20693 requires building the in-process agent library with static tracepoints
20694 support. At present, the UST (LTTng Userspace Tracer,
20695 @url{http://lttng.org/ust}) tracing engine is supported. This support
20696 is automatically available if UST development headers are found in the
20697 standard include path when @code{gdbserver} is built, or if
20698 @code{gdbserver} was explicitly configured using @option{--with-ust}
20699 to point at such headers. You can explicitly disable the support
20700 using @option{--with-ust=no}.
20702 There are several ways to load the in-process agent in your program:
20705 @item Specifying it as dependency at link time
20707 You can link your program dynamically with the in-process agent
20708 library. On most systems, this is accomplished by adding
20709 @code{-linproctrace} to the link command.
20711 @item Using the system's preloading mechanisms
20713 You can force loading the in-process agent at startup time by using
20714 your system's support for preloading shared libraries. Many Unixes
20715 support the concept of preloading user defined libraries. In most
20716 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20717 in the environment. See also the description of @code{gdbserver}'s
20718 @option{--wrapper} command line option.
20720 @item Using @value{GDBN} to force loading the agent at run time
20722 On some systems, you can force the inferior to load a shared library,
20723 by calling a dynamic loader function in the inferior that takes care
20724 of dynamically looking up and loading a shared library. On most Unix
20725 systems, the function is @code{dlopen}. You'll use the @code{call}
20726 command for that. For example:
20729 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
20732 Note that on most Unix systems, for the @code{dlopen} function to be
20733 available, the program needs to be linked with @code{-ldl}.
20736 On systems that have a userspace dynamic loader, like most Unix
20737 systems, when you connect to @code{gdbserver} using @code{target
20738 remote}, you'll find that the program is stopped at the dynamic
20739 loader's entry point, and no shared library has been loaded in the
20740 program's address space yet, including the in-process agent. In that
20741 case, before being able to use any of the fast or static tracepoints
20742 features, you need to let the loader run and load the shared
20743 libraries. The simplest way to do that is to run the program to the
20744 main procedure. E.g., if debugging a C or C@t{++} program, start
20745 @code{gdbserver} like so:
20748 $ gdbserver :9999 myprogram
20751 Start GDB and connect to @code{gdbserver} like so, and run to main:
20755 (@value{GDBP}) target remote myhost:9999
20756 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20757 (@value{GDBP}) b main
20758 (@value{GDBP}) continue
20761 The in-process tracing agent library should now be loaded into the
20762 process; you can confirm it with the @code{info sharedlibrary}
20763 command, which will list @file{libinproctrace.so} as loaded in the
20764 process. You are now ready to install fast tracepoints, list static
20765 tracepoint markers, probe static tracepoints markers, and start
20768 @node Remote Configuration
20769 @section Remote Configuration
20772 @kindex show remote
20773 This section documents the configuration options available when
20774 debugging remote programs. For the options related to the File I/O
20775 extensions of the remote protocol, see @ref{system,
20776 system-call-allowed}.
20779 @item set remoteaddresssize @var{bits}
20780 @cindex address size for remote targets
20781 @cindex bits in remote address
20782 Set the maximum size of address in a memory packet to the specified
20783 number of bits. @value{GDBN} will mask off the address bits above
20784 that number, when it passes addresses to the remote target. The
20785 default value is the number of bits in the target's address.
20787 @item show remoteaddresssize
20788 Show the current value of remote address size in bits.
20790 @item set serial baud @var{n}
20791 @cindex baud rate for remote targets
20792 Set the baud rate for the remote serial I/O to @var{n} baud. The
20793 value is used to set the speed of the serial port used for debugging
20796 @item show serial baud
20797 Show the current speed of the remote connection.
20799 @item set serial parity @var{parity}
20800 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20801 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20803 @item show serial parity
20804 Show the current parity of the serial port.
20806 @item set remotebreak
20807 @cindex interrupt remote programs
20808 @cindex BREAK signal instead of Ctrl-C
20809 @anchor{set remotebreak}
20810 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20811 when you type @kbd{Ctrl-c} to interrupt the program running
20812 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20813 character instead. The default is off, since most remote systems
20814 expect to see @samp{Ctrl-C} as the interrupt signal.
20816 @item show remotebreak
20817 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20818 interrupt the remote program.
20820 @item set remoteflow on
20821 @itemx set remoteflow off
20822 @kindex set remoteflow
20823 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20824 on the serial port used to communicate to the remote target.
20826 @item show remoteflow
20827 @kindex show remoteflow
20828 Show the current setting of hardware flow control.
20830 @item set remotelogbase @var{base}
20831 Set the base (a.k.a.@: radix) of logging serial protocol
20832 communications to @var{base}. Supported values of @var{base} are:
20833 @code{ascii}, @code{octal}, and @code{hex}. The default is
20836 @item show remotelogbase
20837 Show the current setting of the radix for logging remote serial
20840 @item set remotelogfile @var{file}
20841 @cindex record serial communications on file
20842 Record remote serial communications on the named @var{file}. The
20843 default is not to record at all.
20845 @item show remotelogfile.
20846 Show the current setting of the file name on which to record the
20847 serial communications.
20849 @item set remotetimeout @var{num}
20850 @cindex timeout for serial communications
20851 @cindex remote timeout
20852 Set the timeout limit to wait for the remote target to respond to
20853 @var{num} seconds. The default is 2 seconds.
20855 @item show remotetimeout
20856 Show the current number of seconds to wait for the remote target
20859 @cindex limit hardware breakpoints and watchpoints
20860 @cindex remote target, limit break- and watchpoints
20861 @anchor{set remote hardware-watchpoint-limit}
20862 @anchor{set remote hardware-breakpoint-limit}
20863 @item set remote hardware-watchpoint-limit @var{limit}
20864 @itemx set remote hardware-breakpoint-limit @var{limit}
20865 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
20866 watchpoints. A limit of -1, the default, is treated as unlimited.
20868 @cindex limit hardware watchpoints length
20869 @cindex remote target, limit watchpoints length
20870 @anchor{set remote hardware-watchpoint-length-limit}
20871 @item set remote hardware-watchpoint-length-limit @var{limit}
20872 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
20873 a remote hardware watchpoint. A limit of -1, the default, is treated
20876 @item show remote hardware-watchpoint-length-limit
20877 Show the current limit (in bytes) of the maximum length of
20878 a remote hardware watchpoint.
20880 @item set remote exec-file @var{filename}
20881 @itemx show remote exec-file
20882 @anchor{set remote exec-file}
20883 @cindex executable file, for remote target
20884 Select the file used for @code{run} with @code{target
20885 extended-remote}. This should be set to a filename valid on the
20886 target system. If it is not set, the target will use a default
20887 filename (e.g.@: the last program run).
20889 @item set remote interrupt-sequence
20890 @cindex interrupt remote programs
20891 @cindex select Ctrl-C, BREAK or BREAK-g
20892 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
20893 @samp{BREAK-g} as the
20894 sequence to the remote target in order to interrupt the execution.
20895 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
20896 is high level of serial line for some certain time.
20897 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
20898 It is @code{BREAK} signal followed by character @code{g}.
20900 @item show interrupt-sequence
20901 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
20902 is sent by @value{GDBN} to interrupt the remote program.
20903 @code{BREAK-g} is BREAK signal followed by @code{g} and
20904 also known as Magic SysRq g.
20906 @item set remote interrupt-on-connect
20907 @cindex send interrupt-sequence on start
20908 Specify whether interrupt-sequence is sent to remote target when
20909 @value{GDBN} connects to it. This is mostly needed when you debug
20910 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
20911 which is known as Magic SysRq g in order to connect @value{GDBN}.
20913 @item show interrupt-on-connect
20914 Show whether interrupt-sequence is sent
20915 to remote target when @value{GDBN} connects to it.
20919 @item set tcp auto-retry on
20920 @cindex auto-retry, for remote TCP target
20921 Enable auto-retry for remote TCP connections. This is useful if the remote
20922 debugging agent is launched in parallel with @value{GDBN}; there is a race
20923 condition because the agent may not become ready to accept the connection
20924 before @value{GDBN} attempts to connect. When auto-retry is
20925 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20926 to establish the connection using the timeout specified by
20927 @code{set tcp connect-timeout}.
20929 @item set tcp auto-retry off
20930 Do not auto-retry failed TCP connections.
20932 @item show tcp auto-retry
20933 Show the current auto-retry setting.
20935 @item set tcp connect-timeout @var{seconds}
20936 @itemx set tcp connect-timeout unlimited
20937 @cindex connection timeout, for remote TCP target
20938 @cindex timeout, for remote target connection
20939 Set the timeout for establishing a TCP connection to the remote target to
20940 @var{seconds}. The timeout affects both polling to retry failed connections
20941 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20942 that are merely slow to complete, and represents an approximate cumulative
20943 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20944 @value{GDBN} will keep attempting to establish a connection forever,
20945 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20947 @item show tcp connect-timeout
20948 Show the current connection timeout setting.
20951 @cindex remote packets, enabling and disabling
20952 The @value{GDBN} remote protocol autodetects the packets supported by
20953 your debugging stub. If you need to override the autodetection, you
20954 can use these commands to enable or disable individual packets. Each
20955 packet can be set to @samp{on} (the remote target supports this
20956 packet), @samp{off} (the remote target does not support this packet),
20957 or @samp{auto} (detect remote target support for this packet). They
20958 all default to @samp{auto}. For more information about each packet,
20959 see @ref{Remote Protocol}.
20961 During normal use, you should not have to use any of these commands.
20962 If you do, that may be a bug in your remote debugging stub, or a bug
20963 in @value{GDBN}. You may want to report the problem to the
20964 @value{GDBN} developers.
20966 For each packet @var{name}, the command to enable or disable the
20967 packet is @code{set remote @var{name}-packet}. The available settings
20970 @multitable @columnfractions 0.28 0.32 0.25
20973 @tab Related Features
20975 @item @code{fetch-register}
20977 @tab @code{info registers}
20979 @item @code{set-register}
20983 @item @code{binary-download}
20985 @tab @code{load}, @code{set}
20987 @item @code{read-aux-vector}
20988 @tab @code{qXfer:auxv:read}
20989 @tab @code{info auxv}
20991 @item @code{symbol-lookup}
20992 @tab @code{qSymbol}
20993 @tab Detecting multiple threads
20995 @item @code{attach}
20996 @tab @code{vAttach}
20999 @item @code{verbose-resume}
21001 @tab Stepping or resuming multiple threads
21007 @item @code{software-breakpoint}
21011 @item @code{hardware-breakpoint}
21015 @item @code{write-watchpoint}
21019 @item @code{read-watchpoint}
21023 @item @code{access-watchpoint}
21027 @item @code{pid-to-exec-file}
21028 @tab @code{qXfer:exec-file:read}
21029 @tab @code{attach}, @code{run}
21031 @item @code{target-features}
21032 @tab @code{qXfer:features:read}
21033 @tab @code{set architecture}
21035 @item @code{library-info}
21036 @tab @code{qXfer:libraries:read}
21037 @tab @code{info sharedlibrary}
21039 @item @code{memory-map}
21040 @tab @code{qXfer:memory-map:read}
21041 @tab @code{info mem}
21043 @item @code{read-sdata-object}
21044 @tab @code{qXfer:sdata:read}
21045 @tab @code{print $_sdata}
21047 @item @code{read-spu-object}
21048 @tab @code{qXfer:spu:read}
21049 @tab @code{info spu}
21051 @item @code{write-spu-object}
21052 @tab @code{qXfer:spu:write}
21053 @tab @code{info spu}
21055 @item @code{read-siginfo-object}
21056 @tab @code{qXfer:siginfo:read}
21057 @tab @code{print $_siginfo}
21059 @item @code{write-siginfo-object}
21060 @tab @code{qXfer:siginfo:write}
21061 @tab @code{set $_siginfo}
21063 @item @code{threads}
21064 @tab @code{qXfer:threads:read}
21065 @tab @code{info threads}
21067 @item @code{get-thread-local-@*storage-address}
21068 @tab @code{qGetTLSAddr}
21069 @tab Displaying @code{__thread} variables
21071 @item @code{get-thread-information-block-address}
21072 @tab @code{qGetTIBAddr}
21073 @tab Display MS-Windows Thread Information Block.
21075 @item @code{search-memory}
21076 @tab @code{qSearch:memory}
21079 @item @code{supported-packets}
21080 @tab @code{qSupported}
21081 @tab Remote communications parameters
21083 @item @code{catch-syscalls}
21084 @tab @code{QCatchSyscalls}
21085 @tab @code{catch syscall}
21087 @item @code{pass-signals}
21088 @tab @code{QPassSignals}
21089 @tab @code{handle @var{signal}}
21091 @item @code{program-signals}
21092 @tab @code{QProgramSignals}
21093 @tab @code{handle @var{signal}}
21095 @item @code{hostio-close-packet}
21096 @tab @code{vFile:close}
21097 @tab @code{remote get}, @code{remote put}
21099 @item @code{hostio-open-packet}
21100 @tab @code{vFile:open}
21101 @tab @code{remote get}, @code{remote put}
21103 @item @code{hostio-pread-packet}
21104 @tab @code{vFile:pread}
21105 @tab @code{remote get}, @code{remote put}
21107 @item @code{hostio-pwrite-packet}
21108 @tab @code{vFile:pwrite}
21109 @tab @code{remote get}, @code{remote put}
21111 @item @code{hostio-unlink-packet}
21112 @tab @code{vFile:unlink}
21113 @tab @code{remote delete}
21115 @item @code{hostio-readlink-packet}
21116 @tab @code{vFile:readlink}
21119 @item @code{hostio-fstat-packet}
21120 @tab @code{vFile:fstat}
21123 @item @code{hostio-setfs-packet}
21124 @tab @code{vFile:setfs}
21127 @item @code{noack-packet}
21128 @tab @code{QStartNoAckMode}
21129 @tab Packet acknowledgment
21131 @item @code{osdata}
21132 @tab @code{qXfer:osdata:read}
21133 @tab @code{info os}
21135 @item @code{query-attached}
21136 @tab @code{qAttached}
21137 @tab Querying remote process attach state.
21139 @item @code{trace-buffer-size}
21140 @tab @code{QTBuffer:size}
21141 @tab @code{set trace-buffer-size}
21143 @item @code{trace-status}
21144 @tab @code{qTStatus}
21145 @tab @code{tstatus}
21147 @item @code{traceframe-info}
21148 @tab @code{qXfer:traceframe-info:read}
21149 @tab Traceframe info
21151 @item @code{install-in-trace}
21152 @tab @code{InstallInTrace}
21153 @tab Install tracepoint in tracing
21155 @item @code{disable-randomization}
21156 @tab @code{QDisableRandomization}
21157 @tab @code{set disable-randomization}
21159 @item @code{startup-with-shell}
21160 @tab @code{QStartupWithShell}
21161 @tab @code{set startup-with-shell}
21163 @item @code{environment-hex-encoded}
21164 @tab @code{QEnvironmentHexEncoded}
21165 @tab @code{set environment}
21167 @item @code{environment-unset}
21168 @tab @code{QEnvironmentUnset}
21169 @tab @code{unset environment}
21171 @item @code{environment-reset}
21172 @tab @code{QEnvironmentReset}
21173 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
21175 @item @code{set-working-dir}
21176 @tab @code{QSetWorkingDir}
21177 @tab @code{set cwd}
21179 @item @code{conditional-breakpoints-packet}
21180 @tab @code{Z0 and Z1}
21181 @tab @code{Support for target-side breakpoint condition evaluation}
21183 @item @code{multiprocess-extensions}
21184 @tab @code{multiprocess extensions}
21185 @tab Debug multiple processes and remote process PID awareness
21187 @item @code{swbreak-feature}
21188 @tab @code{swbreak stop reason}
21191 @item @code{hwbreak-feature}
21192 @tab @code{hwbreak stop reason}
21195 @item @code{fork-event-feature}
21196 @tab @code{fork stop reason}
21199 @item @code{vfork-event-feature}
21200 @tab @code{vfork stop reason}
21203 @item @code{exec-event-feature}
21204 @tab @code{exec stop reason}
21207 @item @code{thread-events}
21208 @tab @code{QThreadEvents}
21209 @tab Tracking thread lifetime.
21211 @item @code{no-resumed-stop-reply}
21212 @tab @code{no resumed thread left stop reply}
21213 @tab Tracking thread lifetime.
21218 @section Implementing a Remote Stub
21220 @cindex debugging stub, example
21221 @cindex remote stub, example
21222 @cindex stub example, remote debugging
21223 The stub files provided with @value{GDBN} implement the target side of the
21224 communication protocol, and the @value{GDBN} side is implemented in the
21225 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
21226 these subroutines to communicate, and ignore the details. (If you're
21227 implementing your own stub file, you can still ignore the details: start
21228 with one of the existing stub files. @file{sparc-stub.c} is the best
21229 organized, and therefore the easiest to read.)
21231 @cindex remote serial debugging, overview
21232 To debug a program running on another machine (the debugging
21233 @dfn{target} machine), you must first arrange for all the usual
21234 prerequisites for the program to run by itself. For example, for a C
21239 A startup routine to set up the C runtime environment; these usually
21240 have a name like @file{crt0}. The startup routine may be supplied by
21241 your hardware supplier, or you may have to write your own.
21244 A C subroutine library to support your program's
21245 subroutine calls, notably managing input and output.
21248 A way of getting your program to the other machine---for example, a
21249 download program. These are often supplied by the hardware
21250 manufacturer, but you may have to write your own from hardware
21254 The next step is to arrange for your program to use a serial port to
21255 communicate with the machine where @value{GDBN} is running (the @dfn{host}
21256 machine). In general terms, the scheme looks like this:
21260 @value{GDBN} already understands how to use this protocol; when everything
21261 else is set up, you can simply use the @samp{target remote} command
21262 (@pxref{Targets,,Specifying a Debugging Target}).
21264 @item On the target,
21265 you must link with your program a few special-purpose subroutines that
21266 implement the @value{GDBN} remote serial protocol. The file containing these
21267 subroutines is called a @dfn{debugging stub}.
21269 On certain remote targets, you can use an auxiliary program
21270 @code{gdbserver} instead of linking a stub into your program.
21271 @xref{Server,,Using the @code{gdbserver} Program}, for details.
21274 The debugging stub is specific to the architecture of the remote
21275 machine; for example, use @file{sparc-stub.c} to debug programs on
21278 @cindex remote serial stub list
21279 These working remote stubs are distributed with @value{GDBN}:
21284 @cindex @file{i386-stub.c}
21287 For Intel 386 and compatible architectures.
21290 @cindex @file{m68k-stub.c}
21291 @cindex Motorola 680x0
21293 For Motorola 680x0 architectures.
21296 @cindex @file{sh-stub.c}
21299 For Renesas SH architectures.
21302 @cindex @file{sparc-stub.c}
21304 For @sc{sparc} architectures.
21306 @item sparcl-stub.c
21307 @cindex @file{sparcl-stub.c}
21310 For Fujitsu @sc{sparclite} architectures.
21314 The @file{README} file in the @value{GDBN} distribution may list other
21315 recently added stubs.
21318 * Stub Contents:: What the stub can do for you
21319 * Bootstrapping:: What you must do for the stub
21320 * Debug Session:: Putting it all together
21323 @node Stub Contents
21324 @subsection What the Stub Can Do for You
21326 @cindex remote serial stub
21327 The debugging stub for your architecture supplies these three
21331 @item set_debug_traps
21332 @findex set_debug_traps
21333 @cindex remote serial stub, initialization
21334 This routine arranges for @code{handle_exception} to run when your
21335 program stops. You must call this subroutine explicitly in your
21336 program's startup code.
21338 @item handle_exception
21339 @findex handle_exception
21340 @cindex remote serial stub, main routine
21341 This is the central workhorse, but your program never calls it
21342 explicitly---the setup code arranges for @code{handle_exception} to
21343 run when a trap is triggered.
21345 @code{handle_exception} takes control when your program stops during
21346 execution (for example, on a breakpoint), and mediates communications
21347 with @value{GDBN} on the host machine. This is where the communications
21348 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
21349 representative on the target machine. It begins by sending summary
21350 information on the state of your program, then continues to execute,
21351 retrieving and transmitting any information @value{GDBN} needs, until you
21352 execute a @value{GDBN} command that makes your program resume; at that point,
21353 @code{handle_exception} returns control to your own code on the target
21357 @cindex @code{breakpoint} subroutine, remote
21358 Use this auxiliary subroutine to make your program contain a
21359 breakpoint. Depending on the particular situation, this may be the only
21360 way for @value{GDBN} to get control. For instance, if your target
21361 machine has some sort of interrupt button, you won't need to call this;
21362 pressing the interrupt button transfers control to
21363 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
21364 simply receiving characters on the serial port may also trigger a trap;
21365 again, in that situation, you don't need to call @code{breakpoint} from
21366 your own program---simply running @samp{target remote} from the host
21367 @value{GDBN} session gets control.
21369 Call @code{breakpoint} if none of these is true, or if you simply want
21370 to make certain your program stops at a predetermined point for the
21371 start of your debugging session.
21374 @node Bootstrapping
21375 @subsection What You Must Do for the Stub
21377 @cindex remote stub, support routines
21378 The debugging stubs that come with @value{GDBN} are set up for a particular
21379 chip architecture, but they have no information about the rest of your
21380 debugging target machine.
21382 First of all you need to tell the stub how to communicate with the
21386 @item int getDebugChar()
21387 @findex getDebugChar
21388 Write this subroutine to read a single character from the serial port.
21389 It may be identical to @code{getchar} for your target system; a
21390 different name is used to allow you to distinguish the two if you wish.
21392 @item void putDebugChar(int)
21393 @findex putDebugChar
21394 Write this subroutine to write a single character to the serial port.
21395 It may be identical to @code{putchar} for your target system; a
21396 different name is used to allow you to distinguish the two if you wish.
21399 @cindex control C, and remote debugging
21400 @cindex interrupting remote targets
21401 If you want @value{GDBN} to be able to stop your program while it is
21402 running, you need to use an interrupt-driven serial driver, and arrange
21403 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
21404 character). That is the character which @value{GDBN} uses to tell the
21405 remote system to stop.
21407 Getting the debugging target to return the proper status to @value{GDBN}
21408 probably requires changes to the standard stub; one quick and dirty way
21409 is to just execute a breakpoint instruction (the ``dirty'' part is that
21410 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
21412 Other routines you need to supply are:
21415 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
21416 @findex exceptionHandler
21417 Write this function to install @var{exception_address} in the exception
21418 handling tables. You need to do this because the stub does not have any
21419 way of knowing what the exception handling tables on your target system
21420 are like (for example, the processor's table might be in @sc{rom},
21421 containing entries which point to a table in @sc{ram}).
21422 The @var{exception_number} specifies the exception which should be changed;
21423 its meaning is architecture-dependent (for example, different numbers
21424 might represent divide by zero, misaligned access, etc). When this
21425 exception occurs, control should be transferred directly to
21426 @var{exception_address}, and the processor state (stack, registers,
21427 and so on) should be just as it is when a processor exception occurs. So if
21428 you want to use a jump instruction to reach @var{exception_address}, it
21429 should be a simple jump, not a jump to subroutine.
21431 For the 386, @var{exception_address} should be installed as an interrupt
21432 gate so that interrupts are masked while the handler runs. The gate
21433 should be at privilege level 0 (the most privileged level). The
21434 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21435 help from @code{exceptionHandler}.
21437 @item void flush_i_cache()
21438 @findex flush_i_cache
21439 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
21440 instruction cache, if any, on your target machine. If there is no
21441 instruction cache, this subroutine may be a no-op.
21443 On target machines that have instruction caches, @value{GDBN} requires this
21444 function to make certain that the state of your program is stable.
21448 You must also make sure this library routine is available:
21451 @item void *memset(void *, int, int)
21453 This is the standard library function @code{memset} that sets an area of
21454 memory to a known value. If you have one of the free versions of
21455 @code{libc.a}, @code{memset} can be found there; otherwise, you must
21456 either obtain it from your hardware manufacturer, or write your own.
21459 If you do not use the GNU C compiler, you may need other standard
21460 library subroutines as well; this varies from one stub to another,
21461 but in general the stubs are likely to use any of the common library
21462 subroutines which @code{@value{NGCC}} generates as inline code.
21465 @node Debug Session
21466 @subsection Putting it All Together
21468 @cindex remote serial debugging summary
21469 In summary, when your program is ready to debug, you must follow these
21474 Make sure you have defined the supporting low-level routines
21475 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
21477 @code{getDebugChar}, @code{putDebugChar},
21478 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
21482 Insert these lines in your program's startup code, before the main
21483 procedure is called:
21490 On some machines, when a breakpoint trap is raised, the hardware
21491 automatically makes the PC point to the instruction after the
21492 breakpoint. If your machine doesn't do that, you may need to adjust
21493 @code{handle_exception} to arrange for it to return to the instruction
21494 after the breakpoint on this first invocation, so that your program
21495 doesn't keep hitting the initial breakpoint instead of making
21499 For the 680x0 stub only, you need to provide a variable called
21500 @code{exceptionHook}. Normally you just use:
21503 void (*exceptionHook)() = 0;
21507 but if before calling @code{set_debug_traps}, you set it to point to a
21508 function in your program, that function is called when
21509 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
21510 error). The function indicated by @code{exceptionHook} is called with
21511 one parameter: an @code{int} which is the exception number.
21514 Compile and link together: your program, the @value{GDBN} debugging stub for
21515 your target architecture, and the supporting subroutines.
21518 Make sure you have a serial connection between your target machine and
21519 the @value{GDBN} host, and identify the serial port on the host.
21522 @c The "remote" target now provides a `load' command, so we should
21523 @c document that. FIXME.
21524 Download your program to your target machine (or get it there by
21525 whatever means the manufacturer provides), and start it.
21528 Start @value{GDBN} on the host, and connect to the target
21529 (@pxref{Connecting,,Connecting to a Remote Target}).
21533 @node Configurations
21534 @chapter Configuration-Specific Information
21536 While nearly all @value{GDBN} commands are available for all native and
21537 cross versions of the debugger, there are some exceptions. This chapter
21538 describes things that are only available in certain configurations.
21540 There are three major categories of configurations: native
21541 configurations, where the host and target are the same, embedded
21542 operating system configurations, which are usually the same for several
21543 different processor architectures, and bare embedded processors, which
21544 are quite different from each other.
21549 * Embedded Processors::
21556 This section describes details specific to particular native
21560 * BSD libkvm Interface:: Debugging BSD kernel memory images
21561 * SVR4 Process Information:: SVR4 process information
21562 * DJGPP Native:: Features specific to the DJGPP port
21563 * Cygwin Native:: Features specific to the Cygwin port
21564 * Hurd Native:: Features specific to @sc{gnu} Hurd
21565 * Darwin:: Features specific to Darwin
21568 @node BSD libkvm Interface
21569 @subsection BSD libkvm Interface
21572 @cindex kernel memory image
21573 @cindex kernel crash dump
21575 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21576 interface that provides a uniform interface for accessing kernel virtual
21577 memory images, including live systems and crash dumps. @value{GDBN}
21578 uses this interface to allow you to debug live kernels and kernel crash
21579 dumps on many native BSD configurations. This is implemented as a
21580 special @code{kvm} debugging target. For debugging a live system, load
21581 the currently running kernel into @value{GDBN} and connect to the
21585 (@value{GDBP}) @b{target kvm}
21588 For debugging crash dumps, provide the file name of the crash dump as an
21592 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21595 Once connected to the @code{kvm} target, the following commands are
21601 Set current context from the @dfn{Process Control Block} (PCB) address.
21604 Set current context from proc address. This command isn't available on
21605 modern FreeBSD systems.
21608 @node SVR4 Process Information
21609 @subsection SVR4 Process Information
21611 @cindex examine process image
21612 @cindex process info via @file{/proc}
21614 Many versions of SVR4 and compatible systems provide a facility called
21615 @samp{/proc} that can be used to examine the image of a running
21616 process using file-system subroutines.
21618 If @value{GDBN} is configured for an operating system with this
21619 facility, the command @code{info proc} is available to report
21620 information about the process running your program, or about any
21621 process running on your system. This includes, as of this writing,
21622 @sc{gnu}/Linux and Solaris, for example.
21624 This command may also work on core files that were created on a system
21625 that has the @samp{/proc} facility.
21631 @itemx info proc @var{process-id}
21632 Summarize available information about any running process. If a
21633 process ID is specified by @var{process-id}, display information about
21634 that process; otherwise display information about the program being
21635 debugged. The summary includes the debugged process ID, the command
21636 line used to invoke it, its current working directory, and its
21637 executable file's absolute file name.
21639 On some systems, @var{process-id} can be of the form
21640 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21641 within a process. If the optional @var{pid} part is missing, it means
21642 a thread from the process being debugged (the leading @samp{/} still
21643 needs to be present, or else @value{GDBN} will interpret the number as
21644 a process ID rather than a thread ID).
21646 @item info proc cmdline
21647 @cindex info proc cmdline
21648 Show the original command line of the process. This command is
21649 specific to @sc{gnu}/Linux.
21651 @item info proc cwd
21652 @cindex info proc cwd
21653 Show the current working directory of the process. This command is
21654 specific to @sc{gnu}/Linux.
21656 @item info proc exe
21657 @cindex info proc exe
21658 Show the name of executable of the process. This command is specific
21661 @item info proc mappings
21662 @cindex memory address space mappings
21663 Report the memory address space ranges accessible in the program, with
21664 information on whether the process has read, write, or execute access
21665 rights to each range. On @sc{gnu}/Linux systems, each memory range
21666 includes the object file which is mapped to that range, instead of the
21667 memory access rights to that range.
21669 @item info proc stat
21670 @itemx info proc status
21671 @cindex process detailed status information
21672 These subcommands are specific to @sc{gnu}/Linux systems. They show
21673 the process-related information, including the user ID and group ID;
21674 how many threads are there in the process; its virtual memory usage;
21675 the signals that are pending, blocked, and ignored; its TTY; its
21676 consumption of system and user time; its stack size; its @samp{nice}
21677 value; etc. For more information, see the @samp{proc} man page
21678 (type @kbd{man 5 proc} from your shell prompt).
21680 @item info proc all
21681 Show all the information about the process described under all of the
21682 above @code{info proc} subcommands.
21685 @comment These sub-options of 'info proc' were not included when
21686 @comment procfs.c was re-written. Keep their descriptions around
21687 @comment against the day when someone finds the time to put them back in.
21688 @kindex info proc times
21689 @item info proc times
21690 Starting time, user CPU time, and system CPU time for your program and
21693 @kindex info proc id
21695 Report on the process IDs related to your program: its own process ID,
21696 the ID of its parent, the process group ID, and the session ID.
21699 @item set procfs-trace
21700 @kindex set procfs-trace
21701 @cindex @code{procfs} API calls
21702 This command enables and disables tracing of @code{procfs} API calls.
21704 @item show procfs-trace
21705 @kindex show procfs-trace
21706 Show the current state of @code{procfs} API call tracing.
21708 @item set procfs-file @var{file}
21709 @kindex set procfs-file
21710 Tell @value{GDBN} to write @code{procfs} API trace to the named
21711 @var{file}. @value{GDBN} appends the trace info to the previous
21712 contents of the file. The default is to display the trace on the
21715 @item show procfs-file
21716 @kindex show procfs-file
21717 Show the file to which @code{procfs} API trace is written.
21719 @item proc-trace-entry
21720 @itemx proc-trace-exit
21721 @itemx proc-untrace-entry
21722 @itemx proc-untrace-exit
21723 @kindex proc-trace-entry
21724 @kindex proc-trace-exit
21725 @kindex proc-untrace-entry
21726 @kindex proc-untrace-exit
21727 These commands enable and disable tracing of entries into and exits
21728 from the @code{syscall} interface.
21731 @kindex info pidlist
21732 @cindex process list, QNX Neutrino
21733 For QNX Neutrino only, this command displays the list of all the
21734 processes and all the threads within each process.
21737 @kindex info meminfo
21738 @cindex mapinfo list, QNX Neutrino
21739 For QNX Neutrino only, this command displays the list of all mapinfos.
21743 @subsection Features for Debugging @sc{djgpp} Programs
21744 @cindex @sc{djgpp} debugging
21745 @cindex native @sc{djgpp} debugging
21746 @cindex MS-DOS-specific commands
21749 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
21750 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
21751 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
21752 top of real-mode DOS systems and their emulations.
21754 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
21755 defines a few commands specific to the @sc{djgpp} port. This
21756 subsection describes those commands.
21761 This is a prefix of @sc{djgpp}-specific commands which print
21762 information about the target system and important OS structures.
21765 @cindex MS-DOS system info
21766 @cindex free memory information (MS-DOS)
21767 @item info dos sysinfo
21768 This command displays assorted information about the underlying
21769 platform: the CPU type and features, the OS version and flavor, the
21770 DPMI version, and the available conventional and DPMI memory.
21775 @cindex segment descriptor tables
21776 @cindex descriptor tables display
21778 @itemx info dos ldt
21779 @itemx info dos idt
21780 These 3 commands display entries from, respectively, Global, Local,
21781 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21782 tables are data structures which store a descriptor for each segment
21783 that is currently in use. The segment's selector is an index into a
21784 descriptor table; the table entry for that index holds the
21785 descriptor's base address and limit, and its attributes and access
21788 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21789 segment (used for both data and the stack), and a DOS segment (which
21790 allows access to DOS/BIOS data structures and absolute addresses in
21791 conventional memory). However, the DPMI host will usually define
21792 additional segments in order to support the DPMI environment.
21794 @cindex garbled pointers
21795 These commands allow to display entries from the descriptor tables.
21796 Without an argument, all entries from the specified table are
21797 displayed. An argument, which should be an integer expression, means
21798 display a single entry whose index is given by the argument. For
21799 example, here's a convenient way to display information about the
21800 debugged program's data segment:
21803 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21804 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21808 This comes in handy when you want to see whether a pointer is outside
21809 the data segment's limit (i.e.@: @dfn{garbled}).
21811 @cindex page tables display (MS-DOS)
21813 @itemx info dos pte
21814 These two commands display entries from, respectively, the Page
21815 Directory and the Page Tables. Page Directories and Page Tables are
21816 data structures which control how virtual memory addresses are mapped
21817 into physical addresses. A Page Table includes an entry for every
21818 page of memory that is mapped into the program's address space; there
21819 may be several Page Tables, each one holding up to 4096 entries. A
21820 Page Directory has up to 4096 entries, one each for every Page Table
21821 that is currently in use.
21823 Without an argument, @kbd{info dos pde} displays the entire Page
21824 Directory, and @kbd{info dos pte} displays all the entries in all of
21825 the Page Tables. An argument, an integer expression, given to the
21826 @kbd{info dos pde} command means display only that entry from the Page
21827 Directory table. An argument given to the @kbd{info dos pte} command
21828 means display entries from a single Page Table, the one pointed to by
21829 the specified entry in the Page Directory.
21831 @cindex direct memory access (DMA) on MS-DOS
21832 These commands are useful when your program uses @dfn{DMA} (Direct
21833 Memory Access), which needs physical addresses to program the DMA
21836 These commands are supported only with some DPMI servers.
21838 @cindex physical address from linear address
21839 @item info dos address-pte @var{addr}
21840 This command displays the Page Table entry for a specified linear
21841 address. The argument @var{addr} is a linear address which should
21842 already have the appropriate segment's base address added to it,
21843 because this command accepts addresses which may belong to @emph{any}
21844 segment. For example, here's how to display the Page Table entry for
21845 the page where a variable @code{i} is stored:
21848 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21849 @exdent @code{Page Table entry for address 0x11a00d30:}
21850 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21854 This says that @code{i} is stored at offset @code{0xd30} from the page
21855 whose physical base address is @code{0x02698000}, and shows all the
21856 attributes of that page.
21858 Note that you must cast the addresses of variables to a @code{char *},
21859 since otherwise the value of @code{__djgpp_base_address}, the base
21860 address of all variables and functions in a @sc{djgpp} program, will
21861 be added using the rules of C pointer arithmetics: if @code{i} is
21862 declared an @code{int}, @value{GDBN} will add 4 times the value of
21863 @code{__djgpp_base_address} to the address of @code{i}.
21865 Here's another example, it displays the Page Table entry for the
21869 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
21870 @exdent @code{Page Table entry for address 0x29110:}
21871 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
21875 (The @code{+ 3} offset is because the transfer buffer's address is the
21876 3rd member of the @code{_go32_info_block} structure.) The output
21877 clearly shows that this DPMI server maps the addresses in conventional
21878 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
21879 linear (@code{0x29110}) addresses are identical.
21881 This command is supported only with some DPMI servers.
21884 @cindex DOS serial data link, remote debugging
21885 In addition to native debugging, the DJGPP port supports remote
21886 debugging via a serial data link. The following commands are specific
21887 to remote serial debugging in the DJGPP port of @value{GDBN}.
21890 @kindex set com1base
21891 @kindex set com1irq
21892 @kindex set com2base
21893 @kindex set com2irq
21894 @kindex set com3base
21895 @kindex set com3irq
21896 @kindex set com4base
21897 @kindex set com4irq
21898 @item set com1base @var{addr}
21899 This command sets the base I/O port address of the @file{COM1} serial
21902 @item set com1irq @var{irq}
21903 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
21904 for the @file{COM1} serial port.
21906 There are similar commands @samp{set com2base}, @samp{set com3irq},
21907 etc.@: for setting the port address and the @code{IRQ} lines for the
21910 @kindex show com1base
21911 @kindex show com1irq
21912 @kindex show com2base
21913 @kindex show com2irq
21914 @kindex show com3base
21915 @kindex show com3irq
21916 @kindex show com4base
21917 @kindex show com4irq
21918 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
21919 display the current settings of the base address and the @code{IRQ}
21920 lines used by the COM ports.
21923 @kindex info serial
21924 @cindex DOS serial port status
21925 This command prints the status of the 4 DOS serial ports. For each
21926 port, it prints whether it's active or not, its I/O base address and
21927 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
21928 counts of various errors encountered so far.
21932 @node Cygwin Native
21933 @subsection Features for Debugging MS Windows PE Executables
21934 @cindex MS Windows debugging
21935 @cindex native Cygwin debugging
21936 @cindex Cygwin-specific commands
21938 @value{GDBN} supports native debugging of MS Windows programs, including
21939 DLLs with and without symbolic debugging information.
21941 @cindex Ctrl-BREAK, MS-Windows
21942 @cindex interrupt debuggee on MS-Windows
21943 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21944 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21945 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21946 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21947 sequence, which can be used to interrupt the debuggee even if it
21950 There are various additional Cygwin-specific commands, described in
21951 this section. Working with DLLs that have no debugging symbols is
21952 described in @ref{Non-debug DLL Symbols}.
21957 This is a prefix of MS Windows-specific commands which print
21958 information about the target system and important OS structures.
21960 @item info w32 selector
21961 This command displays information returned by
21962 the Win32 API @code{GetThreadSelectorEntry} function.
21963 It takes an optional argument that is evaluated to
21964 a long value to give the information about this given selector.
21965 Without argument, this command displays information
21966 about the six segment registers.
21968 @item info w32 thread-information-block
21969 This command displays thread specific information stored in the
21970 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21971 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21973 @kindex signal-event
21974 @item signal-event @var{id}
21975 This command signals an event with user-provided @var{id}. Used to resume
21976 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
21978 To use it, create or edit the following keys in
21979 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
21980 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
21981 (for x86_64 versions):
21985 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
21986 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
21987 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
21989 The first @code{%ld} will be replaced by the process ID of the
21990 crashing process, the second @code{%ld} will be replaced by the ID of
21991 the event that blocks the crashing process, waiting for @value{GDBN}
21995 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
21996 make the system run debugger specified by the Debugger key
21997 automatically, @code{0} will cause a dialog box with ``OK'' and
21998 ``Cancel'' buttons to appear, which allows the user to either
21999 terminate the crashing process (OK) or debug it (Cancel).
22002 @kindex set cygwin-exceptions
22003 @cindex debugging the Cygwin DLL
22004 @cindex Cygwin DLL, debugging
22005 @item set cygwin-exceptions @var{mode}
22006 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
22007 happen inside the Cygwin DLL. If @var{mode} is @code{off},
22008 @value{GDBN} will delay recognition of exceptions, and may ignore some
22009 exceptions which seem to be caused by internal Cygwin DLL
22010 ``bookkeeping''. This option is meant primarily for debugging the
22011 Cygwin DLL itself; the default value is @code{off} to avoid annoying
22012 @value{GDBN} users with false @code{SIGSEGV} signals.
22014 @kindex show cygwin-exceptions
22015 @item show cygwin-exceptions
22016 Displays whether @value{GDBN} will break on exceptions that happen
22017 inside the Cygwin DLL itself.
22019 @kindex set new-console
22020 @item set new-console @var{mode}
22021 If @var{mode} is @code{on} the debuggee will
22022 be started in a new console on next start.
22023 If @var{mode} is @code{off}, the debuggee will
22024 be started in the same console as the debugger.
22026 @kindex show new-console
22027 @item show new-console
22028 Displays whether a new console is used
22029 when the debuggee is started.
22031 @kindex set new-group
22032 @item set new-group @var{mode}
22033 This boolean value controls whether the debuggee should
22034 start a new group or stay in the same group as the debugger.
22035 This affects the way the Windows OS handles
22038 @kindex show new-group
22039 @item show new-group
22040 Displays current value of new-group boolean.
22042 @kindex set debugevents
22043 @item set debugevents
22044 This boolean value adds debug output concerning kernel events related
22045 to the debuggee seen by the debugger. This includes events that
22046 signal thread and process creation and exit, DLL loading and
22047 unloading, console interrupts, and debugging messages produced by the
22048 Windows @code{OutputDebugString} API call.
22050 @kindex set debugexec
22051 @item set debugexec
22052 This boolean value adds debug output concerning execute events
22053 (such as resume thread) seen by the debugger.
22055 @kindex set debugexceptions
22056 @item set debugexceptions
22057 This boolean value adds debug output concerning exceptions in the
22058 debuggee seen by the debugger.
22060 @kindex set debugmemory
22061 @item set debugmemory
22062 This boolean value adds debug output concerning debuggee memory reads
22063 and writes by the debugger.
22067 This boolean values specifies whether the debuggee is called
22068 via a shell or directly (default value is on).
22072 Displays if the debuggee will be started with a shell.
22077 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
22080 @node Non-debug DLL Symbols
22081 @subsubsection Support for DLLs without Debugging Symbols
22082 @cindex DLLs with no debugging symbols
22083 @cindex Minimal symbols and DLLs
22085 Very often on windows, some of the DLLs that your program relies on do
22086 not include symbolic debugging information (for example,
22087 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
22088 symbols in a DLL, it relies on the minimal amount of symbolic
22089 information contained in the DLL's export table. This section
22090 describes working with such symbols, known internally to @value{GDBN} as
22091 ``minimal symbols''.
22093 Note that before the debugged program has started execution, no DLLs
22094 will have been loaded. The easiest way around this problem is simply to
22095 start the program --- either by setting a breakpoint or letting the
22096 program run once to completion.
22098 @subsubsection DLL Name Prefixes
22100 In keeping with the naming conventions used by the Microsoft debugging
22101 tools, DLL export symbols are made available with a prefix based on the
22102 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
22103 also entered into the symbol table, so @code{CreateFileA} is often
22104 sufficient. In some cases there will be name clashes within a program
22105 (particularly if the executable itself includes full debugging symbols)
22106 necessitating the use of the fully qualified name when referring to the
22107 contents of the DLL. Use single-quotes around the name to avoid the
22108 exclamation mark (``!'') being interpreted as a language operator.
22110 Note that the internal name of the DLL may be all upper-case, even
22111 though the file name of the DLL is lower-case, or vice-versa. Since
22112 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
22113 some confusion. If in doubt, try the @code{info functions} and
22114 @code{info variables} commands or even @code{maint print msymbols}
22115 (@pxref{Symbols}). Here's an example:
22118 (@value{GDBP}) info function CreateFileA
22119 All functions matching regular expression "CreateFileA":
22121 Non-debugging symbols:
22122 0x77e885f4 CreateFileA
22123 0x77e885f4 KERNEL32!CreateFileA
22127 (@value{GDBP}) info function !
22128 All functions matching regular expression "!":
22130 Non-debugging symbols:
22131 0x6100114c cygwin1!__assert
22132 0x61004034 cygwin1!_dll_crt0@@0
22133 0x61004240 cygwin1!dll_crt0(per_process *)
22137 @subsubsection Working with Minimal Symbols
22139 Symbols extracted from a DLL's export table do not contain very much
22140 type information. All that @value{GDBN} can do is guess whether a symbol
22141 refers to a function or variable depending on the linker section that
22142 contains the symbol. Also note that the actual contents of the memory
22143 contained in a DLL are not available unless the program is running. This
22144 means that you cannot examine the contents of a variable or disassemble
22145 a function within a DLL without a running program.
22147 Variables are generally treated as pointers and dereferenced
22148 automatically. For this reason, it is often necessary to prefix a
22149 variable name with the address-of operator (``&'') and provide explicit
22150 type information in the command. Here's an example of the type of
22154 (@value{GDBP}) print 'cygwin1!__argv'
22155 'cygwin1!__argv' has unknown type; cast it to its declared type
22159 (@value{GDBP}) x 'cygwin1!__argv'
22160 'cygwin1!__argv' has unknown type; cast it to its declared type
22163 And two possible solutions:
22166 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
22167 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
22171 (@value{GDBP}) x/2x &'cygwin1!__argv'
22172 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
22173 (@value{GDBP}) x/x 0x10021608
22174 0x10021608: 0x0022fd98
22175 (@value{GDBP}) x/s 0x0022fd98
22176 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
22179 Setting a break point within a DLL is possible even before the program
22180 starts execution. However, under these circumstances, @value{GDBN} can't
22181 examine the initial instructions of the function in order to skip the
22182 function's frame set-up code. You can work around this by using ``*&''
22183 to set the breakpoint at a raw memory address:
22186 (@value{GDBP}) break *&'python22!PyOS_Readline'
22187 Breakpoint 1 at 0x1e04eff0
22190 The author of these extensions is not entirely convinced that setting a
22191 break point within a shared DLL like @file{kernel32.dll} is completely
22195 @subsection Commands Specific to @sc{gnu} Hurd Systems
22196 @cindex @sc{gnu} Hurd debugging
22198 This subsection describes @value{GDBN} commands specific to the
22199 @sc{gnu} Hurd native debugging.
22204 @kindex set signals@r{, Hurd command}
22205 @kindex set sigs@r{, Hurd command}
22206 This command toggles the state of inferior signal interception by
22207 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
22208 affected by this command. @code{sigs} is a shorthand alias for
22213 @kindex show signals@r{, Hurd command}
22214 @kindex show sigs@r{, Hurd command}
22215 Show the current state of intercepting inferior's signals.
22217 @item set signal-thread
22218 @itemx set sigthread
22219 @kindex set signal-thread
22220 @kindex set sigthread
22221 This command tells @value{GDBN} which thread is the @code{libc} signal
22222 thread. That thread is run when a signal is delivered to a running
22223 process. @code{set sigthread} is the shorthand alias of @code{set
22226 @item show signal-thread
22227 @itemx show sigthread
22228 @kindex show signal-thread
22229 @kindex show sigthread
22230 These two commands show which thread will run when the inferior is
22231 delivered a signal.
22234 @kindex set stopped@r{, Hurd command}
22235 This commands tells @value{GDBN} that the inferior process is stopped,
22236 as with the @code{SIGSTOP} signal. The stopped process can be
22237 continued by delivering a signal to it.
22240 @kindex show stopped@r{, Hurd command}
22241 This command shows whether @value{GDBN} thinks the debuggee is
22244 @item set exceptions
22245 @kindex set exceptions@r{, Hurd command}
22246 Use this command to turn off trapping of exceptions in the inferior.
22247 When exception trapping is off, neither breakpoints nor
22248 single-stepping will work. To restore the default, set exception
22251 @item show exceptions
22252 @kindex show exceptions@r{, Hurd command}
22253 Show the current state of trapping exceptions in the inferior.
22255 @item set task pause
22256 @kindex set task@r{, Hurd commands}
22257 @cindex task attributes (@sc{gnu} Hurd)
22258 @cindex pause current task (@sc{gnu} Hurd)
22259 This command toggles task suspension when @value{GDBN} has control.
22260 Setting it to on takes effect immediately, and the task is suspended
22261 whenever @value{GDBN} gets control. Setting it to off will take
22262 effect the next time the inferior is continued. If this option is set
22263 to off, you can use @code{set thread default pause on} or @code{set
22264 thread pause on} (see below) to pause individual threads.
22266 @item show task pause
22267 @kindex show task@r{, Hurd commands}
22268 Show the current state of task suspension.
22270 @item set task detach-suspend-count
22271 @cindex task suspend count
22272 @cindex detach from task, @sc{gnu} Hurd
22273 This command sets the suspend count the task will be left with when
22274 @value{GDBN} detaches from it.
22276 @item show task detach-suspend-count
22277 Show the suspend count the task will be left with when detaching.
22279 @item set task exception-port
22280 @itemx set task excp
22281 @cindex task exception port, @sc{gnu} Hurd
22282 This command sets the task exception port to which @value{GDBN} will
22283 forward exceptions. The argument should be the value of the @dfn{send
22284 rights} of the task. @code{set task excp} is a shorthand alias.
22286 @item set noninvasive
22287 @cindex noninvasive task options
22288 This command switches @value{GDBN} to a mode that is the least
22289 invasive as far as interfering with the inferior is concerned. This
22290 is the same as using @code{set task pause}, @code{set exceptions}, and
22291 @code{set signals} to values opposite to the defaults.
22293 @item info send-rights
22294 @itemx info receive-rights
22295 @itemx info port-rights
22296 @itemx info port-sets
22297 @itemx info dead-names
22300 @cindex send rights, @sc{gnu} Hurd
22301 @cindex receive rights, @sc{gnu} Hurd
22302 @cindex port rights, @sc{gnu} Hurd
22303 @cindex port sets, @sc{gnu} Hurd
22304 @cindex dead names, @sc{gnu} Hurd
22305 These commands display information about, respectively, send rights,
22306 receive rights, port rights, port sets, and dead names of a task.
22307 There are also shorthand aliases: @code{info ports} for @code{info
22308 port-rights} and @code{info psets} for @code{info port-sets}.
22310 @item set thread pause
22311 @kindex set thread@r{, Hurd command}
22312 @cindex thread properties, @sc{gnu} Hurd
22313 @cindex pause current thread (@sc{gnu} Hurd)
22314 This command toggles current thread suspension when @value{GDBN} has
22315 control. Setting it to on takes effect immediately, and the current
22316 thread is suspended whenever @value{GDBN} gets control. Setting it to
22317 off will take effect the next time the inferior is continued.
22318 Normally, this command has no effect, since when @value{GDBN} has
22319 control, the whole task is suspended. However, if you used @code{set
22320 task pause off} (see above), this command comes in handy to suspend
22321 only the current thread.
22323 @item show thread pause
22324 @kindex show thread@r{, Hurd command}
22325 This command shows the state of current thread suspension.
22327 @item set thread run
22328 This command sets whether the current thread is allowed to run.
22330 @item show thread run
22331 Show whether the current thread is allowed to run.
22333 @item set thread detach-suspend-count
22334 @cindex thread suspend count, @sc{gnu} Hurd
22335 @cindex detach from thread, @sc{gnu} Hurd
22336 This command sets the suspend count @value{GDBN} will leave on a
22337 thread when detaching. This number is relative to the suspend count
22338 found by @value{GDBN} when it notices the thread; use @code{set thread
22339 takeover-suspend-count} to force it to an absolute value.
22341 @item show thread detach-suspend-count
22342 Show the suspend count @value{GDBN} will leave on the thread when
22345 @item set thread exception-port
22346 @itemx set thread excp
22347 Set the thread exception port to which to forward exceptions. This
22348 overrides the port set by @code{set task exception-port} (see above).
22349 @code{set thread excp} is the shorthand alias.
22351 @item set thread takeover-suspend-count
22352 Normally, @value{GDBN}'s thread suspend counts are relative to the
22353 value @value{GDBN} finds when it notices each thread. This command
22354 changes the suspend counts to be absolute instead.
22356 @item set thread default
22357 @itemx show thread default
22358 @cindex thread default settings, @sc{gnu} Hurd
22359 Each of the above @code{set thread} commands has a @code{set thread
22360 default} counterpart (e.g., @code{set thread default pause}, @code{set
22361 thread default exception-port}, etc.). The @code{thread default}
22362 variety of commands sets the default thread properties for all
22363 threads; you can then change the properties of individual threads with
22364 the non-default commands.
22371 @value{GDBN} provides the following commands specific to the Darwin target:
22374 @item set debug darwin @var{num}
22375 @kindex set debug darwin
22376 When set to a non zero value, enables debugging messages specific to
22377 the Darwin support. Higher values produce more verbose output.
22379 @item show debug darwin
22380 @kindex show debug darwin
22381 Show the current state of Darwin messages.
22383 @item set debug mach-o @var{num}
22384 @kindex set debug mach-o
22385 When set to a non zero value, enables debugging messages while
22386 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
22387 file format used on Darwin for object and executable files.) Higher
22388 values produce more verbose output. This is a command to diagnose
22389 problems internal to @value{GDBN} and should not be needed in normal
22392 @item show debug mach-o
22393 @kindex show debug mach-o
22394 Show the current state of Mach-O file messages.
22396 @item set mach-exceptions on
22397 @itemx set mach-exceptions off
22398 @kindex set mach-exceptions
22399 On Darwin, faults are first reported as a Mach exception and are then
22400 mapped to a Posix signal. Use this command to turn on trapping of
22401 Mach exceptions in the inferior. This might be sometimes useful to
22402 better understand the cause of a fault. The default is off.
22404 @item show mach-exceptions
22405 @kindex show mach-exceptions
22406 Show the current state of exceptions trapping.
22411 @section Embedded Operating Systems
22413 This section describes configurations involving the debugging of
22414 embedded operating systems that are available for several different
22417 @value{GDBN} includes the ability to debug programs running on
22418 various real-time operating systems.
22420 @node Embedded Processors
22421 @section Embedded Processors
22423 This section goes into details specific to particular embedded
22426 @cindex send command to simulator
22427 Whenever a specific embedded processor has a simulator, @value{GDBN}
22428 allows to send an arbitrary command to the simulator.
22431 @item sim @var{command}
22432 @kindex sim@r{, a command}
22433 Send an arbitrary @var{command} string to the simulator. Consult the
22434 documentation for the specific simulator in use for information about
22435 acceptable commands.
22440 * ARC:: Synopsys ARC
22442 * M68K:: Motorola M68K
22443 * MicroBlaze:: Xilinx MicroBlaze
22444 * MIPS Embedded:: MIPS Embedded
22445 * PowerPC Embedded:: PowerPC Embedded
22448 * Super-H:: Renesas Super-H
22452 @subsection Synopsys ARC
22453 @cindex Synopsys ARC
22454 @cindex ARC specific commands
22460 @value{GDBN} provides the following ARC-specific commands:
22463 @item set debug arc
22464 @kindex set debug arc
22465 Control the level of ARC specific debug messages. Use 0 for no messages (the
22466 default), 1 for debug messages, and 2 for even more debug messages.
22468 @item show debug arc
22469 @kindex show debug arc
22470 Show the level of ARC specific debugging in operation.
22472 @item maint print arc arc-instruction @var{address}
22473 @kindex maint print arc arc-instruction
22474 Print internal disassembler information about instruction at a given address.
22481 @value{GDBN} provides the following ARM-specific commands:
22484 @item set arm disassembler
22486 This commands selects from a list of disassembly styles. The
22487 @code{"std"} style is the standard style.
22489 @item show arm disassembler
22491 Show the current disassembly style.
22493 @item set arm apcs32
22494 @cindex ARM 32-bit mode
22495 This command toggles ARM operation mode between 32-bit and 26-bit.
22497 @item show arm apcs32
22498 Display the current usage of the ARM 32-bit mode.
22500 @item set arm fpu @var{fputype}
22501 This command sets the ARM floating-point unit (FPU) type. The
22502 argument @var{fputype} can be one of these:
22506 Determine the FPU type by querying the OS ABI.
22508 Software FPU, with mixed-endian doubles on little-endian ARM
22511 GCC-compiled FPA co-processor.
22513 Software FPU with pure-endian doubles.
22519 Show the current type of the FPU.
22522 This command forces @value{GDBN} to use the specified ABI.
22525 Show the currently used ABI.
22527 @item set arm fallback-mode (arm|thumb|auto)
22528 @value{GDBN} uses the symbol table, when available, to determine
22529 whether instructions are ARM or Thumb. This command controls
22530 @value{GDBN}'s default behavior when the symbol table is not
22531 available. The default is @samp{auto}, which causes @value{GDBN} to
22532 use the current execution mode (from the @code{T} bit in the @code{CPSR}
22535 @item show arm fallback-mode
22536 Show the current fallback instruction mode.
22538 @item set arm force-mode (arm|thumb|auto)
22539 This command overrides use of the symbol table to determine whether
22540 instructions are ARM or Thumb. The default is @samp{auto}, which
22541 causes @value{GDBN} to use the symbol table and then the setting
22542 of @samp{set arm fallback-mode}.
22544 @item show arm force-mode
22545 Show the current forced instruction mode.
22547 @item set debug arm
22548 Toggle whether to display ARM-specific debugging messages from the ARM
22549 target support subsystem.
22551 @item show debug arm
22552 Show whether ARM-specific debugging messages are enabled.
22556 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22557 The @value{GDBN} ARM simulator accepts the following optional arguments.
22560 @item --swi-support=@var{type}
22561 Tell the simulator which SWI interfaces to support. The argument
22562 @var{type} may be a comma separated list of the following values.
22563 The default value is @code{all}.
22578 The Motorola m68k configuration includes ColdFire support.
22581 @subsection MicroBlaze
22582 @cindex Xilinx MicroBlaze
22583 @cindex XMD, Xilinx Microprocessor Debugger
22585 The MicroBlaze is a soft-core processor supported on various Xilinx
22586 FPGAs, such as Spartan or Virtex series. Boards with these processors
22587 usually have JTAG ports which connect to a host system running the Xilinx
22588 Embedded Development Kit (EDK) or Software Development Kit (SDK).
22589 This host system is used to download the configuration bitstream to
22590 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
22591 communicates with the target board using the JTAG interface and
22592 presents a @code{gdbserver} interface to the board. By default
22593 @code{xmd} uses port @code{1234}. (While it is possible to change
22594 this default port, it requires the use of undocumented @code{xmd}
22595 commands. Contact Xilinx support if you need to do this.)
22597 Use these GDB commands to connect to the MicroBlaze target processor.
22600 @item target remote :1234
22601 Use this command to connect to the target if you are running @value{GDBN}
22602 on the same system as @code{xmd}.
22604 @item target remote @var{xmd-host}:1234
22605 Use this command to connect to the target if it is connected to @code{xmd}
22606 running on a different system named @var{xmd-host}.
22609 Use this command to download a program to the MicroBlaze target.
22611 @item set debug microblaze @var{n}
22612 Enable MicroBlaze-specific debugging messages if non-zero.
22614 @item show debug microblaze @var{n}
22615 Show MicroBlaze-specific debugging level.
22618 @node MIPS Embedded
22619 @subsection @acronym{MIPS} Embedded
22622 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22625 @item set mipsfpu double
22626 @itemx set mipsfpu single
22627 @itemx set mipsfpu none
22628 @itemx set mipsfpu auto
22629 @itemx show mipsfpu
22630 @kindex set mipsfpu
22631 @kindex show mipsfpu
22632 @cindex @acronym{MIPS} remote floating point
22633 @cindex floating point, @acronym{MIPS} remote
22634 If your target board does not support the @acronym{MIPS} floating point
22635 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22636 need this, you may wish to put the command in your @value{GDBN} init
22637 file). This tells @value{GDBN} how to find the return value of
22638 functions which return floating point values. It also allows
22639 @value{GDBN} to avoid saving the floating point registers when calling
22640 functions on the board. If you are using a floating point coprocessor
22641 with only single precision floating point support, as on the @sc{r4650}
22642 processor, use the command @samp{set mipsfpu single}. The default
22643 double precision floating point coprocessor may be selected using
22644 @samp{set mipsfpu double}.
22646 In previous versions the only choices were double precision or no
22647 floating point, so @samp{set mipsfpu on} will select double precision
22648 and @samp{set mipsfpu off} will select no floating point.
22650 As usual, you can inquire about the @code{mipsfpu} variable with
22651 @samp{show mipsfpu}.
22654 @node PowerPC Embedded
22655 @subsection PowerPC Embedded
22657 @cindex DVC register
22658 @value{GDBN} supports using the DVC (Data Value Compare) register to
22659 implement in hardware simple hardware watchpoint conditions of the form:
22662 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22663 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22666 The DVC register will be automatically used when @value{GDBN} detects
22667 such pattern in a condition expression, and the created watchpoint uses one
22668 debug register (either the @code{exact-watchpoints} option is on and the
22669 variable is scalar, or the variable has a length of one byte). This feature
22670 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22673 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22674 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22675 in which case watchpoints using only one debug register are created when
22676 watching variables of scalar types.
22678 You can create an artificial array to watch an arbitrary memory
22679 region using one of the following commands (@pxref{Expressions}):
22682 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22683 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22686 PowerPC embedded processors support masked watchpoints. See the discussion
22687 about the @code{mask} argument in @ref{Set Watchpoints}.
22689 @cindex ranged breakpoint
22690 PowerPC embedded processors support hardware accelerated
22691 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22692 the inferior whenever it executes an instruction at any address within
22693 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22694 use the @code{break-range} command.
22696 @value{GDBN} provides the following PowerPC-specific commands:
22699 @kindex break-range
22700 @item break-range @var{start-location}, @var{end-location}
22701 Set a breakpoint for an address range given by
22702 @var{start-location} and @var{end-location}, which can specify a function name,
22703 a line number, an offset of lines from the current line or from the start
22704 location, or an address of an instruction (see @ref{Specify Location},
22705 for a list of all the possible ways to specify a @var{location}.)
22706 The breakpoint will stop execution of the inferior whenever it
22707 executes an instruction at any address within the specified range,
22708 (including @var{start-location} and @var{end-location}.)
22710 @kindex set powerpc
22711 @item set powerpc soft-float
22712 @itemx show powerpc soft-float
22713 Force @value{GDBN} to use (or not use) a software floating point calling
22714 convention. By default, @value{GDBN} selects the calling convention based
22715 on the selected architecture and the provided executable file.
22717 @item set powerpc vector-abi
22718 @itemx show powerpc vector-abi
22719 Force @value{GDBN} to use the specified calling convention for vector
22720 arguments and return values. The valid options are @samp{auto};
22721 @samp{generic}, to avoid vector registers even if they are present;
22722 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22723 registers. By default, @value{GDBN} selects the calling convention
22724 based on the selected architecture and the provided executable file.
22726 @item set powerpc exact-watchpoints
22727 @itemx show powerpc exact-watchpoints
22728 Allow @value{GDBN} to use only one debug register when watching a variable
22729 of scalar type, thus assuming that the variable is accessed through the
22730 address of its first byte.
22735 @subsection Atmel AVR
22738 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22739 following AVR-specific commands:
22742 @item info io_registers
22743 @kindex info io_registers@r{, AVR}
22744 @cindex I/O registers (Atmel AVR)
22745 This command displays information about the AVR I/O registers. For
22746 each register, @value{GDBN} prints its number and value.
22753 When configured for debugging CRIS, @value{GDBN} provides the
22754 following CRIS-specific commands:
22757 @item set cris-version @var{ver}
22758 @cindex CRIS version
22759 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22760 The CRIS version affects register names and sizes. This command is useful in
22761 case autodetection of the CRIS version fails.
22763 @item show cris-version
22764 Show the current CRIS version.
22766 @item set cris-dwarf2-cfi
22767 @cindex DWARF-2 CFI and CRIS
22768 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22769 Change to @samp{off} when using @code{gcc-cris} whose version is below
22772 @item show cris-dwarf2-cfi
22773 Show the current state of using DWARF-2 CFI.
22775 @item set cris-mode @var{mode}
22777 Set the current CRIS mode to @var{mode}. It should only be changed when
22778 debugging in guru mode, in which case it should be set to
22779 @samp{guru} (the default is @samp{normal}).
22781 @item show cris-mode
22782 Show the current CRIS mode.
22786 @subsection Renesas Super-H
22789 For the Renesas Super-H processor, @value{GDBN} provides these
22793 @item set sh calling-convention @var{convention}
22794 @kindex set sh calling-convention
22795 Set the calling-convention used when calling functions from @value{GDBN}.
22796 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22797 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22798 convention. If the DWARF-2 information of the called function specifies
22799 that the function follows the Renesas calling convention, the function
22800 is called using the Renesas calling convention. If the calling convention
22801 is set to @samp{renesas}, the Renesas calling convention is always used,
22802 regardless of the DWARF-2 information. This can be used to override the
22803 default of @samp{gcc} if debug information is missing, or the compiler
22804 does not emit the DWARF-2 calling convention entry for a function.
22806 @item show sh calling-convention
22807 @kindex show sh calling-convention
22808 Show the current calling convention setting.
22813 @node Architectures
22814 @section Architectures
22816 This section describes characteristics of architectures that affect
22817 all uses of @value{GDBN} with the architecture, both native and cross.
22824 * HPPA:: HP PA architecture
22825 * SPU:: Cell Broadband Engine SPU architecture
22832 @subsection AArch64
22833 @cindex AArch64 support
22835 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22836 following special commands:
22839 @item set debug aarch64
22840 @kindex set debug aarch64
22841 This command determines whether AArch64 architecture-specific debugging
22842 messages are to be displayed.
22844 @item show debug aarch64
22845 Show whether AArch64 debugging messages are displayed.
22850 @subsection x86 Architecture-specific Issues
22853 @item set struct-convention @var{mode}
22854 @kindex set struct-convention
22855 @cindex struct return convention
22856 @cindex struct/union returned in registers
22857 Set the convention used by the inferior to return @code{struct}s and
22858 @code{union}s from functions to @var{mode}. Possible values of
22859 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22860 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22861 are returned on the stack, while @code{"reg"} means that a
22862 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22863 be returned in a register.
22865 @item show struct-convention
22866 @kindex show struct-convention
22867 Show the current setting of the convention to return @code{struct}s
22872 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
22873 @cindex Intel Memory Protection Extensions (MPX).
22875 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22876 @footnote{The register named with capital letters represent the architecture
22877 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22878 which are the lower bound and upper bound. Bounds are effective addresses or
22879 memory locations. The upper bounds are architecturally represented in 1's
22880 complement form. A bound having lower bound = 0, and upper bound = 0
22881 (1's complement of all bits set) will allow access to the entire address space.
22883 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22884 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22885 display the upper bound performing the complement of one operation on the
22886 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22887 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22888 can also be noted that the upper bounds are inclusive.
22890 As an example, assume that the register BND0 holds bounds for a pointer having
22891 access allowed for the range between 0x32 and 0x71. The values present on
22892 bnd0raw and bnd registers are presented as follows:
22895 bnd0raw = @{0x32, 0xffffffff8e@}
22896 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22899 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22900 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22901 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22902 Python, the display includes the memory size, in bits, accessible to
22905 Bounds can also be stored in bounds tables, which are stored in
22906 application memory. These tables store bounds for pointers by specifying
22907 the bounds pointer's value along with its bounds. Evaluating and changing
22908 bounds located in bound tables is therefore interesting while investigating
22909 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22912 @item show mpx bound @var{pointer}
22913 @kindex show mpx bound
22914 Display bounds of the given @var{pointer}.
22916 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22917 @kindex set mpx bound
22918 Set the bounds of a pointer in the bound table.
22919 This command takes three parameters: @var{pointer} is the pointers
22920 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22921 for lower and upper bounds respectively.
22924 When you call an inferior function on an Intel MPX enabled program,
22925 GDB sets the inferior's bound registers to the init (disabled) state
22926 before calling the function. As a consequence, bounds checks for the
22927 pointer arguments passed to the function will always pass.
22929 This is necessary because when you call an inferior function, the
22930 program is usually in the middle of the execution of other function.
22931 Since at that point bound registers are in an arbitrary state, not
22932 clearing them would lead to random bound violations in the called
22935 You can still examine the influence of the bound registers on the
22936 execution of the called function by stopping the execution of the
22937 called function at its prologue, setting bound registers, and
22938 continuing the execution. For example:
22942 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
22943 $ print upper (a, b, c, d, 1)
22944 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
22946 @{lbound = 0x0, ubound = ffffffff@} : size -1
22949 At this last step the value of bnd0 can be changed for investigation of bound
22950 violations caused along the execution of the call. In order to know how to
22951 set the bound registers or bound table for the call consult the ABI.
22956 See the following section.
22959 @subsection @acronym{MIPS}
22961 @cindex stack on Alpha
22962 @cindex stack on @acronym{MIPS}
22963 @cindex Alpha stack
22964 @cindex @acronym{MIPS} stack
22965 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22966 sometimes requires @value{GDBN} to search backward in the object code to
22967 find the beginning of a function.
22969 @cindex response time, @acronym{MIPS} debugging
22970 To improve response time (especially for embedded applications, where
22971 @value{GDBN} may be restricted to a slow serial line for this search)
22972 you may want to limit the size of this search, using one of these
22976 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22977 @item set heuristic-fence-post @var{limit}
22978 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22979 search for the beginning of a function. A value of @var{0} (the
22980 default) means there is no limit. However, except for @var{0}, the
22981 larger the limit the more bytes @code{heuristic-fence-post} must search
22982 and therefore the longer it takes to run. You should only need to use
22983 this command when debugging a stripped executable.
22985 @item show heuristic-fence-post
22986 Display the current limit.
22990 These commands are available @emph{only} when @value{GDBN} is configured
22991 for debugging programs on Alpha or @acronym{MIPS} processors.
22993 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22997 @item set mips abi @var{arg}
22998 @kindex set mips abi
22999 @cindex set ABI for @acronym{MIPS}
23000 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
23001 values of @var{arg} are:
23005 The default ABI associated with the current binary (this is the
23015 @item show mips abi
23016 @kindex show mips abi
23017 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
23019 @item set mips compression @var{arg}
23020 @kindex set mips compression
23021 @cindex code compression, @acronym{MIPS}
23022 Tell @value{GDBN} which @acronym{MIPS} compressed
23023 @acronym{ISA, Instruction Set Architecture} encoding is used by the
23024 inferior. @value{GDBN} uses this for code disassembly and other
23025 internal interpretation purposes. This setting is only referred to
23026 when no executable has been associated with the debugging session or
23027 the executable does not provide information about the encoding it uses.
23028 Otherwise this setting is automatically updated from information
23029 provided by the executable.
23031 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
23032 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
23033 executables containing @acronym{MIPS16} code frequently are not
23034 identified as such.
23036 This setting is ``sticky''; that is, it retains its value across
23037 debugging sessions until reset either explicitly with this command or
23038 implicitly from an executable.
23040 The compiler and/or assembler typically add symbol table annotations to
23041 identify functions compiled for the @acronym{MIPS16} or
23042 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
23043 are present, @value{GDBN} uses them in preference to the global
23044 compressed @acronym{ISA} encoding setting.
23046 @item show mips compression
23047 @kindex show mips compression
23048 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
23049 @value{GDBN} to debug the inferior.
23052 @itemx show mipsfpu
23053 @xref{MIPS Embedded, set mipsfpu}.
23055 @item set mips mask-address @var{arg}
23056 @kindex set mips mask-address
23057 @cindex @acronym{MIPS} addresses, masking
23058 This command determines whether the most-significant 32 bits of 64-bit
23059 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
23060 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
23061 setting, which lets @value{GDBN} determine the correct value.
23063 @item show mips mask-address
23064 @kindex show mips mask-address
23065 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
23068 @item set remote-mips64-transfers-32bit-regs
23069 @kindex set remote-mips64-transfers-32bit-regs
23070 This command controls compatibility with 64-bit @acronym{MIPS} targets that
23071 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
23072 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
23073 and 64 bits for other registers, set this option to @samp{on}.
23075 @item show remote-mips64-transfers-32bit-regs
23076 @kindex show remote-mips64-transfers-32bit-regs
23077 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
23079 @item set debug mips
23080 @kindex set debug mips
23081 This command turns on and off debugging messages for the @acronym{MIPS}-specific
23082 target code in @value{GDBN}.
23084 @item show debug mips
23085 @kindex show debug mips
23086 Show the current setting of @acronym{MIPS} debugging messages.
23092 @cindex HPPA support
23094 When @value{GDBN} is debugging the HP PA architecture, it provides the
23095 following special commands:
23098 @item set debug hppa
23099 @kindex set debug hppa
23100 This command determines whether HPPA architecture-specific debugging
23101 messages are to be displayed.
23103 @item show debug hppa
23104 Show whether HPPA debugging messages are displayed.
23106 @item maint print unwind @var{address}
23107 @kindex maint print unwind@r{, HPPA}
23108 This command displays the contents of the unwind table entry at the
23109 given @var{address}.
23115 @subsection Cell Broadband Engine SPU architecture
23116 @cindex Cell Broadband Engine
23119 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
23120 it provides the following special commands:
23123 @item info spu event
23125 Display SPU event facility status. Shows current event mask
23126 and pending event status.
23128 @item info spu signal
23129 Display SPU signal notification facility status. Shows pending
23130 signal-control word and signal notification mode of both signal
23131 notification channels.
23133 @item info spu mailbox
23134 Display SPU mailbox facility status. Shows all pending entries,
23135 in order of processing, in each of the SPU Write Outbound,
23136 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
23139 Display MFC DMA status. Shows all pending commands in the MFC
23140 DMA queue. For each entry, opcode, tag, class IDs, effective
23141 and local store addresses and transfer size are shown.
23143 @item info spu proxydma
23144 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
23145 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
23146 and local store addresses and transfer size are shown.
23150 When @value{GDBN} is debugging a combined PowerPC/SPU application
23151 on the Cell Broadband Engine, it provides in addition the following
23155 @item set spu stop-on-load @var{arg}
23157 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
23158 will give control to the user when a new SPE thread enters its @code{main}
23159 function. The default is @code{off}.
23161 @item show spu stop-on-load
23163 Show whether to stop for new SPE threads.
23165 @item set spu auto-flush-cache @var{arg}
23166 Set whether to automatically flush the software-managed cache. When set to
23167 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
23168 cache to be flushed whenever SPE execution stops. This provides a consistent
23169 view of PowerPC memory that is accessed via the cache. If an application
23170 does not use the software-managed cache, this option has no effect.
23172 @item show spu auto-flush-cache
23173 Show whether to automatically flush the software-managed cache.
23178 @subsection PowerPC
23179 @cindex PowerPC architecture
23181 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
23182 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
23183 numbers stored in the floating point registers. These values must be stored
23184 in two consecutive registers, always starting at an even register like
23185 @code{f0} or @code{f2}.
23187 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
23188 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
23189 @code{f2} and @code{f3} for @code{$dl1} and so on.
23191 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
23192 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
23195 @subsection Nios II
23196 @cindex Nios II architecture
23198 When @value{GDBN} is debugging the Nios II architecture,
23199 it provides the following special commands:
23203 @item set debug nios2
23204 @kindex set debug nios2
23205 This command turns on and off debugging messages for the Nios II
23206 target code in @value{GDBN}.
23208 @item show debug nios2
23209 @kindex show debug nios2
23210 Show the current setting of Nios II debugging messages.
23214 @subsection Sparc64
23215 @cindex Sparc64 support
23216 @cindex Application Data Integrity
23217 @subsubsection ADI Support
23219 The M7 processor supports an Application Data Integrity (ADI) feature that
23220 detects invalid data accesses. When software allocates memory and enables
23221 ADI on the allocated memory, it chooses a 4-bit version number, sets the
23222 version in the upper 4 bits of the 64-bit pointer to that data, and stores
23223 the 4-bit version in every cacheline of that data. Hardware saves the latter
23224 in spare bits in the cache and memory hierarchy. On each load and store,
23225 the processor compares the upper 4 VA (virtual address) bits to the
23226 cacheline's version. If there is a mismatch, the processor generates a
23227 version mismatch trap which can be either precise or disrupting. The trap
23228 is an error condition which the kernel delivers to the process as a SIGSEGV
23231 Note that only 64-bit applications can use ADI and need to be built with
23234 Values of the ADI version tags, which are in granularity of a
23235 cacheline (64 bytes), can be viewed or modified.
23239 @kindex adi examine
23240 @item adi (examine | x) [ / @var{n} ] @var{addr}
23242 The @code{adi examine} command displays the value of one ADI version tag per
23245 @var{n} is a decimal integer specifying the number in bytes; the default
23246 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
23247 block size, to display.
23249 @var{addr} is the address in user address space where you want @value{GDBN}
23250 to begin displaying the ADI version tags.
23252 Below is an example of displaying ADI versions of variable "shmaddr".
23255 (@value{GDBP}) adi x/100 shmaddr
23256 0xfff800010002c000: 0 0
23260 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
23262 The @code{adi assign} command is used to assign new ADI version tag
23265 @var{n} is a decimal integer specifying the number in bytes;
23266 the default is 1. It specifies how much ADI version information, at the
23267 ratio of 1:ADI block size, to modify.
23269 @var{addr} is the address in user address space where you want @value{GDBN}
23270 to begin modifying the ADI version tags.
23272 @var{tag} is the new ADI version tag.
23274 For example, do the following to modify then verify ADI versions of
23275 variable "shmaddr":
23278 (@value{GDBP}) adi a/100 shmaddr = 7
23279 (@value{GDBP}) adi x/100 shmaddr
23280 0xfff800010002c000: 7 7
23285 @node Controlling GDB
23286 @chapter Controlling @value{GDBN}
23288 You can alter the way @value{GDBN} interacts with you by using the
23289 @code{set} command. For commands controlling how @value{GDBN} displays
23290 data, see @ref{Print Settings, ,Print Settings}. Other settings are
23295 * Editing:: Command editing
23296 * Command History:: Command history
23297 * Screen Size:: Screen size
23298 * Numbers:: Numbers
23299 * ABI:: Configuring the current ABI
23300 * Auto-loading:: Automatically loading associated files
23301 * Messages/Warnings:: Optional warnings and messages
23302 * Debugging Output:: Optional messages about internal happenings
23303 * Other Misc Settings:: Other Miscellaneous Settings
23311 @value{GDBN} indicates its readiness to read a command by printing a string
23312 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
23313 can change the prompt string with the @code{set prompt} command. For
23314 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
23315 the prompt in one of the @value{GDBN} sessions so that you can always tell
23316 which one you are talking to.
23318 @emph{Note:} @code{set prompt} does not add a space for you after the
23319 prompt you set. This allows you to set a prompt which ends in a space
23320 or a prompt that does not.
23324 @item set prompt @var{newprompt}
23325 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
23327 @kindex show prompt
23329 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
23332 Versions of @value{GDBN} that ship with Python scripting enabled have
23333 prompt extensions. The commands for interacting with these extensions
23337 @kindex set extended-prompt
23338 @item set extended-prompt @var{prompt}
23339 Set an extended prompt that allows for substitutions.
23340 @xref{gdb.prompt}, for a list of escape sequences that can be used for
23341 substitution. Any escape sequences specified as part of the prompt
23342 string are replaced with the corresponding strings each time the prompt
23348 set extended-prompt Current working directory: \w (gdb)
23351 Note that when an extended-prompt is set, it takes control of the
23352 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
23354 @kindex show extended-prompt
23355 @item show extended-prompt
23356 Prints the extended prompt. Any escape sequences specified as part of
23357 the prompt string with @code{set extended-prompt}, are replaced with the
23358 corresponding strings each time the prompt is displayed.
23362 @section Command Editing
23364 @cindex command line editing
23366 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
23367 @sc{gnu} library provides consistent behavior for programs which provide a
23368 command line interface to the user. Advantages are @sc{gnu} Emacs-style
23369 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
23370 substitution, and a storage and recall of command history across
23371 debugging sessions.
23373 You may control the behavior of command line editing in @value{GDBN} with the
23374 command @code{set}.
23377 @kindex set editing
23380 @itemx set editing on
23381 Enable command line editing (enabled by default).
23383 @item set editing off
23384 Disable command line editing.
23386 @kindex show editing
23388 Show whether command line editing is enabled.
23391 @ifset SYSTEM_READLINE
23392 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
23394 @ifclear SYSTEM_READLINE
23395 @xref{Command Line Editing},
23397 for more details about the Readline
23398 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
23399 encouraged to read that chapter.
23401 @node Command History
23402 @section Command History
23403 @cindex command history
23405 @value{GDBN} can keep track of the commands you type during your
23406 debugging sessions, so that you can be certain of precisely what
23407 happened. Use these commands to manage the @value{GDBN} command
23410 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
23411 package, to provide the history facility.
23412 @ifset SYSTEM_READLINE
23413 @xref{Using History Interactively, , , history, GNU History Library},
23415 @ifclear SYSTEM_READLINE
23416 @xref{Using History Interactively},
23418 for the detailed description of the History library.
23420 To issue a command to @value{GDBN} without affecting certain aspects of
23421 the state which is seen by users, prefix it with @samp{server }
23422 (@pxref{Server Prefix}). This
23423 means that this command will not affect the command history, nor will it
23424 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
23425 pressed on a line by itself.
23427 @cindex @code{server}, command prefix
23428 The server prefix does not affect the recording of values into the value
23429 history; to print a value without recording it into the value history,
23430 use the @code{output} command instead of the @code{print} command.
23432 Here is the description of @value{GDBN} commands related to command
23436 @cindex history substitution
23437 @cindex history file
23438 @kindex set history filename
23439 @cindex @env{GDBHISTFILE}, environment variable
23440 @item set history filename @var{fname}
23441 Set the name of the @value{GDBN} command history file to @var{fname}.
23442 This is the file where @value{GDBN} reads an initial command history
23443 list, and where it writes the command history from this session when it
23444 exits. You can access this list through history expansion or through
23445 the history command editing characters listed below. This file defaults
23446 to the value of the environment variable @code{GDBHISTFILE}, or to
23447 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
23450 @cindex save command history
23451 @kindex set history save
23452 @item set history save
23453 @itemx set history save on
23454 Record command history in a file, whose name may be specified with the
23455 @code{set history filename} command. By default, this option is disabled.
23457 @item set history save off
23458 Stop recording command history in a file.
23460 @cindex history size
23461 @kindex set history size
23462 @cindex @env{GDBHISTSIZE}, environment variable
23463 @item set history size @var{size}
23464 @itemx set history size unlimited
23465 Set the number of commands which @value{GDBN} keeps in its history list.
23466 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
23467 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
23468 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
23469 either a negative number or the empty string, then the number of commands
23470 @value{GDBN} keeps in the history list is unlimited.
23472 @cindex remove duplicate history
23473 @kindex set history remove-duplicates
23474 @item set history remove-duplicates @var{count}
23475 @itemx set history remove-duplicates unlimited
23476 Control the removal of duplicate history entries in the command history list.
23477 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
23478 history entries and remove the first entry that is a duplicate of the current
23479 entry being added to the command history list. If @var{count} is
23480 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
23481 removal of duplicate history entries is disabled.
23483 Only history entries added during the current session are considered for
23484 removal. This option is set to 0 by default.
23488 History expansion assigns special meaning to the character @kbd{!}.
23489 @ifset SYSTEM_READLINE
23490 @xref{Event Designators, , , history, GNU History Library},
23492 @ifclear SYSTEM_READLINE
23493 @xref{Event Designators},
23497 @cindex history expansion, turn on/off
23498 Since @kbd{!} is also the logical not operator in C, history expansion
23499 is off by default. If you decide to enable history expansion with the
23500 @code{set history expansion on} command, you may sometimes need to
23501 follow @kbd{!} (when it is used as logical not, in an expression) with
23502 a space or a tab to prevent it from being expanded. The readline
23503 history facilities do not attempt substitution on the strings
23504 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
23506 The commands to control history expansion are:
23509 @item set history expansion on
23510 @itemx set history expansion
23511 @kindex set history expansion
23512 Enable history expansion. History expansion is off by default.
23514 @item set history expansion off
23515 Disable history expansion.
23518 @kindex show history
23520 @itemx show history filename
23521 @itemx show history save
23522 @itemx show history size
23523 @itemx show history expansion
23524 These commands display the state of the @value{GDBN} history parameters.
23525 @code{show history} by itself displays all four states.
23530 @kindex show commands
23531 @cindex show last commands
23532 @cindex display command history
23533 @item show commands
23534 Display the last ten commands in the command history.
23536 @item show commands @var{n}
23537 Print ten commands centered on command number @var{n}.
23539 @item show commands +
23540 Print ten commands just after the commands last printed.
23544 @section Screen Size
23545 @cindex size of screen
23546 @cindex screen size
23549 @cindex pauses in output
23551 Certain commands to @value{GDBN} may produce large amounts of
23552 information output to the screen. To help you read all of it,
23553 @value{GDBN} pauses and asks you for input at the end of each page of
23554 output. Type @key{RET} when you want to continue the output, or @kbd{q}
23555 to discard the remaining output. Also, the screen width setting
23556 determines when to wrap lines of output. Depending on what is being
23557 printed, @value{GDBN} tries to break the line at a readable place,
23558 rather than simply letting it overflow onto the following line.
23560 Normally @value{GDBN} knows the size of the screen from the terminal
23561 driver software. For example, on Unix @value{GDBN} uses the termcap data base
23562 together with the value of the @code{TERM} environment variable and the
23563 @code{stty rows} and @code{stty cols} settings. If this is not correct,
23564 you can override it with the @code{set height} and @code{set
23571 @kindex show height
23572 @item set height @var{lpp}
23573 @itemx set height unlimited
23575 @itemx set width @var{cpl}
23576 @itemx set width unlimited
23578 These @code{set} commands specify a screen height of @var{lpp} lines and
23579 a screen width of @var{cpl} characters. The associated @code{show}
23580 commands display the current settings.
23582 If you specify a height of either @code{unlimited} or zero lines,
23583 @value{GDBN} does not pause during output no matter how long the
23584 output is. This is useful if output is to a file or to an editor
23587 Likewise, you can specify @samp{set width unlimited} or @samp{set
23588 width 0} to prevent @value{GDBN} from wrapping its output.
23590 @item set pagination on
23591 @itemx set pagination off
23592 @kindex set pagination
23593 Turn the output pagination on or off; the default is on. Turning
23594 pagination off is the alternative to @code{set height unlimited}. Note that
23595 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23596 Options, -batch}) also automatically disables pagination.
23598 @item show pagination
23599 @kindex show pagination
23600 Show the current pagination mode.
23605 @cindex number representation
23606 @cindex entering numbers
23608 You can always enter numbers in octal, decimal, or hexadecimal in
23609 @value{GDBN} by the usual conventions: octal numbers begin with
23610 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23611 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23612 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23613 10; likewise, the default display for numbers---when no particular
23614 format is specified---is base 10. You can change the default base for
23615 both input and output with the commands described below.
23618 @kindex set input-radix
23619 @item set input-radix @var{base}
23620 Set the default base for numeric input. Supported choices
23621 for @var{base} are decimal 8, 10, or 16. The base must itself be
23622 specified either unambiguously or using the current input radix; for
23626 set input-radix 012
23627 set input-radix 10.
23628 set input-radix 0xa
23632 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23633 leaves the input radix unchanged, no matter what it was, since
23634 @samp{10}, being without any leading or trailing signs of its base, is
23635 interpreted in the current radix. Thus, if the current radix is 16,
23636 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23639 @kindex set output-radix
23640 @item set output-radix @var{base}
23641 Set the default base for numeric display. Supported choices
23642 for @var{base} are decimal 8, 10, or 16. The base must itself be
23643 specified either unambiguously or using the current input radix.
23645 @kindex show input-radix
23646 @item show input-radix
23647 Display the current default base for numeric input.
23649 @kindex show output-radix
23650 @item show output-radix
23651 Display the current default base for numeric display.
23653 @item set radix @r{[}@var{base}@r{]}
23657 These commands set and show the default base for both input and output
23658 of numbers. @code{set radix} sets the radix of input and output to
23659 the same base; without an argument, it resets the radix back to its
23660 default value of 10.
23665 @section Configuring the Current ABI
23667 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23668 application automatically. However, sometimes you need to override its
23669 conclusions. Use these commands to manage @value{GDBN}'s view of the
23675 @cindex Newlib OS ABI and its influence on the longjmp handling
23677 One @value{GDBN} configuration can debug binaries for multiple operating
23678 system targets, either via remote debugging or native emulation.
23679 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
23680 but you can override its conclusion using the @code{set osabi} command.
23681 One example where this is useful is in debugging of binaries which use
23682 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
23683 not have the same identifying marks that the standard C library for your
23686 When @value{GDBN} is debugging the AArch64 architecture, it provides a
23687 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
23688 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
23689 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
23693 Show the OS ABI currently in use.
23696 With no argument, show the list of registered available OS ABI's.
23698 @item set osabi @var{abi}
23699 Set the current OS ABI to @var{abi}.
23702 @cindex float promotion
23704 Generally, the way that an argument of type @code{float} is passed to a
23705 function depends on whether the function is prototyped. For a prototyped
23706 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
23707 according to the architecture's convention for @code{float}. For unprototyped
23708 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
23709 @code{double} and then passed.
23711 Unfortunately, some forms of debug information do not reliably indicate whether
23712 a function is prototyped. If @value{GDBN} calls a function that is not marked
23713 as prototyped, it consults @kbd{set coerce-float-to-double}.
23716 @kindex set coerce-float-to-double
23717 @item set coerce-float-to-double
23718 @itemx set coerce-float-to-double on
23719 Arguments of type @code{float} will be promoted to @code{double} when passed
23720 to an unprototyped function. This is the default setting.
23722 @item set coerce-float-to-double off
23723 Arguments of type @code{float} will be passed directly to unprototyped
23726 @kindex show coerce-float-to-double
23727 @item show coerce-float-to-double
23728 Show the current setting of promoting @code{float} to @code{double}.
23732 @kindex show cp-abi
23733 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23734 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23735 used to build your application. @value{GDBN} only fully supports
23736 programs with a single C@t{++} ABI; if your program contains code using
23737 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23738 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23739 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23740 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23741 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23742 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23747 Show the C@t{++} ABI currently in use.
23750 With no argument, show the list of supported C@t{++} ABI's.
23752 @item set cp-abi @var{abi}
23753 @itemx set cp-abi auto
23754 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23758 @section Automatically loading associated files
23759 @cindex auto-loading
23761 @value{GDBN} sometimes reads files with commands and settings automatically,
23762 without being explicitly told so by the user. We call this feature
23763 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23764 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23765 results or introduce security risks (e.g., if the file comes from untrusted
23769 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23770 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23772 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23773 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23776 There are various kinds of files @value{GDBN} can automatically load.
23777 In addition to these files, @value{GDBN} supports auto-loading code written
23778 in various extension languages. @xref{Auto-loading extensions}.
23780 Note that loading of these associated files (including the local @file{.gdbinit}
23781 file) requires accordingly configured @code{auto-load safe-path}
23782 (@pxref{Auto-loading safe path}).
23784 For these reasons, @value{GDBN} includes commands and options to let you
23785 control when to auto-load files and which files should be auto-loaded.
23788 @anchor{set auto-load off}
23789 @kindex set auto-load off
23790 @item set auto-load off
23791 Globally disable loading of all auto-loaded files.
23792 You may want to use this command with the @samp{-iex} option
23793 (@pxref{Option -init-eval-command}) such as:
23795 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23798 Be aware that system init file (@pxref{System-wide configuration})
23799 and init files from your home directory (@pxref{Home Directory Init File})
23800 still get read (as they come from generally trusted directories).
23801 To prevent @value{GDBN} from auto-loading even those init files, use the
23802 @option{-nx} option (@pxref{Mode Options}), in addition to
23803 @code{set auto-load no}.
23805 @anchor{show auto-load}
23806 @kindex show auto-load
23807 @item show auto-load
23808 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23812 (gdb) show auto-load
23813 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23814 libthread-db: Auto-loading of inferior specific libthread_db is on.
23815 local-gdbinit: Auto-loading of .gdbinit script from current directory
23817 python-scripts: Auto-loading of Python scripts is on.
23818 safe-path: List of directories from which it is safe to auto-load files
23819 is $debugdir:$datadir/auto-load.
23820 scripts-directory: List of directories from which to load auto-loaded scripts
23821 is $debugdir:$datadir/auto-load.
23824 @anchor{info auto-load}
23825 @kindex info auto-load
23826 @item info auto-load
23827 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23831 (gdb) info auto-load
23834 Yes /home/user/gdb/gdb-gdb.gdb
23835 libthread-db: No auto-loaded libthread-db.
23836 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
23840 Yes /home/user/gdb/gdb-gdb.py
23844 These are @value{GDBN} control commands for the auto-loading:
23846 @multitable @columnfractions .5 .5
23847 @item @xref{set auto-load off}.
23848 @tab Disable auto-loading globally.
23849 @item @xref{show auto-load}.
23850 @tab Show setting of all kinds of files.
23851 @item @xref{info auto-load}.
23852 @tab Show state of all kinds of files.
23853 @item @xref{set auto-load gdb-scripts}.
23854 @tab Control for @value{GDBN} command scripts.
23855 @item @xref{show auto-load gdb-scripts}.
23856 @tab Show setting of @value{GDBN} command scripts.
23857 @item @xref{info auto-load gdb-scripts}.
23858 @tab Show state of @value{GDBN} command scripts.
23859 @item @xref{set auto-load python-scripts}.
23860 @tab Control for @value{GDBN} Python scripts.
23861 @item @xref{show auto-load python-scripts}.
23862 @tab Show setting of @value{GDBN} Python scripts.
23863 @item @xref{info auto-load python-scripts}.
23864 @tab Show state of @value{GDBN} Python scripts.
23865 @item @xref{set auto-load guile-scripts}.
23866 @tab Control for @value{GDBN} Guile scripts.
23867 @item @xref{show auto-load guile-scripts}.
23868 @tab Show setting of @value{GDBN} Guile scripts.
23869 @item @xref{info auto-load guile-scripts}.
23870 @tab Show state of @value{GDBN} Guile scripts.
23871 @item @xref{set auto-load scripts-directory}.
23872 @tab Control for @value{GDBN} auto-loaded scripts location.
23873 @item @xref{show auto-load scripts-directory}.
23874 @tab Show @value{GDBN} auto-loaded scripts location.
23875 @item @xref{add-auto-load-scripts-directory}.
23876 @tab Add directory for auto-loaded scripts location list.
23877 @item @xref{set auto-load local-gdbinit}.
23878 @tab Control for init file in the current directory.
23879 @item @xref{show auto-load local-gdbinit}.
23880 @tab Show setting of init file in the current directory.
23881 @item @xref{info auto-load local-gdbinit}.
23882 @tab Show state of init file in the current directory.
23883 @item @xref{set auto-load libthread-db}.
23884 @tab Control for thread debugging library.
23885 @item @xref{show auto-load libthread-db}.
23886 @tab Show setting of thread debugging library.
23887 @item @xref{info auto-load libthread-db}.
23888 @tab Show state of thread debugging library.
23889 @item @xref{set auto-load safe-path}.
23890 @tab Control directories trusted for automatic loading.
23891 @item @xref{show auto-load safe-path}.
23892 @tab Show directories trusted for automatic loading.
23893 @item @xref{add-auto-load-safe-path}.
23894 @tab Add directory trusted for automatic loading.
23897 @node Init File in the Current Directory
23898 @subsection Automatically loading init file in the current directory
23899 @cindex auto-loading init file in the current directory
23901 By default, @value{GDBN} reads and executes the canned sequences of commands
23902 from init file (if any) in the current working directory,
23903 see @ref{Init File in the Current Directory during Startup}.
23905 Note that loading of this local @file{.gdbinit} file also requires accordingly
23906 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23909 @anchor{set auto-load local-gdbinit}
23910 @kindex set auto-load local-gdbinit
23911 @item set auto-load local-gdbinit [on|off]
23912 Enable or disable the auto-loading of canned sequences of commands
23913 (@pxref{Sequences}) found in init file in the current directory.
23915 @anchor{show auto-load local-gdbinit}
23916 @kindex show auto-load local-gdbinit
23917 @item show auto-load local-gdbinit
23918 Show whether auto-loading of canned sequences of commands from init file in the
23919 current directory is enabled or disabled.
23921 @anchor{info auto-load local-gdbinit}
23922 @kindex info auto-load local-gdbinit
23923 @item info auto-load local-gdbinit
23924 Print whether canned sequences of commands from init file in the
23925 current directory have been auto-loaded.
23928 @node libthread_db.so.1 file
23929 @subsection Automatically loading thread debugging library
23930 @cindex auto-loading libthread_db.so.1
23932 This feature is currently present only on @sc{gnu}/Linux native hosts.
23934 @value{GDBN} reads in some cases thread debugging library from places specific
23935 to the inferior (@pxref{set libthread-db-search-path}).
23937 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23938 without checking this @samp{set auto-load libthread-db} switch as system
23939 libraries have to be trusted in general. In all other cases of
23940 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23941 auto-load libthread-db} is enabled before trying to open such thread debugging
23944 Note that loading of this debugging library also requires accordingly configured
23945 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23948 @anchor{set auto-load libthread-db}
23949 @kindex set auto-load libthread-db
23950 @item set auto-load libthread-db [on|off]
23951 Enable or disable the auto-loading of inferior specific thread debugging library.
23953 @anchor{show auto-load libthread-db}
23954 @kindex show auto-load libthread-db
23955 @item show auto-load libthread-db
23956 Show whether auto-loading of inferior specific thread debugging library is
23957 enabled or disabled.
23959 @anchor{info auto-load libthread-db}
23960 @kindex info auto-load libthread-db
23961 @item info auto-load libthread-db
23962 Print the list of all loaded inferior specific thread debugging libraries and
23963 for each such library print list of inferior @var{pid}s using it.
23966 @node Auto-loading safe path
23967 @subsection Security restriction for auto-loading
23968 @cindex auto-loading safe-path
23970 As the files of inferior can come from untrusted source (such as submitted by
23971 an application user) @value{GDBN} does not always load any files automatically.
23972 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23973 directories trusted for loading files not explicitly requested by user.
23974 Each directory can also be a shell wildcard pattern.
23976 If the path is not set properly you will see a warning and the file will not
23981 Reading symbols from /home/user/gdb/gdb...done.
23982 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23983 declined by your `auto-load safe-path' set
23984 to "$debugdir:$datadir/auto-load".
23985 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23986 declined by your `auto-load safe-path' set
23987 to "$debugdir:$datadir/auto-load".
23991 To instruct @value{GDBN} to go ahead and use the init files anyway,
23992 invoke @value{GDBN} like this:
23995 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23998 The list of trusted directories is controlled by the following commands:
24001 @anchor{set auto-load safe-path}
24002 @kindex set auto-load safe-path
24003 @item set auto-load safe-path @r{[}@var{directories}@r{]}
24004 Set the list of directories (and their subdirectories) trusted for automatic
24005 loading and execution of scripts. You can also enter a specific trusted file.
24006 Each directory can also be a shell wildcard pattern; wildcards do not match
24007 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
24008 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
24009 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
24010 its default value as specified during @value{GDBN} compilation.
24012 The list of directories uses path separator (@samp{:} on GNU and Unix
24013 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24014 to the @env{PATH} environment variable.
24016 @anchor{show auto-load safe-path}
24017 @kindex show auto-load safe-path
24018 @item show auto-load safe-path
24019 Show the list of directories trusted for automatic loading and execution of
24022 @anchor{add-auto-load-safe-path}
24023 @kindex add-auto-load-safe-path
24024 @item add-auto-load-safe-path
24025 Add an entry (or list of entries) to the list of directories trusted for
24026 automatic loading and execution of scripts. Multiple entries may be delimited
24027 by the host platform path separator in use.
24030 This variable defaults to what @code{--with-auto-load-dir} has been configured
24031 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
24032 substitution applies the same as for @ref{set auto-load scripts-directory}.
24033 The default @code{set auto-load safe-path} value can be also overriden by
24034 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
24036 Setting this variable to @file{/} disables this security protection,
24037 corresponding @value{GDBN} configuration option is
24038 @option{--without-auto-load-safe-path}.
24039 This variable is supposed to be set to the system directories writable by the
24040 system superuser only. Users can add their source directories in init files in
24041 their home directories (@pxref{Home Directory Init File}). See also deprecated
24042 init file in the current directory
24043 (@pxref{Init File in the Current Directory during Startup}).
24045 To force @value{GDBN} to load the files it declined to load in the previous
24046 example, you could use one of the following ways:
24049 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
24050 Specify this trusted directory (or a file) as additional component of the list.
24051 You have to specify also any existing directories displayed by
24052 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
24054 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
24055 Specify this directory as in the previous case but just for a single
24056 @value{GDBN} session.
24058 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
24059 Disable auto-loading safety for a single @value{GDBN} session.
24060 This assumes all the files you debug during this @value{GDBN} session will come
24061 from trusted sources.
24063 @item @kbd{./configure --without-auto-load-safe-path}
24064 During compilation of @value{GDBN} you may disable any auto-loading safety.
24065 This assumes all the files you will ever debug with this @value{GDBN} come from
24069 On the other hand you can also explicitly forbid automatic files loading which
24070 also suppresses any such warning messages:
24073 @item @kbd{gdb -iex "set auto-load no" @dots{}}
24074 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
24076 @item @file{~/.gdbinit}: @samp{set auto-load no}
24077 Disable auto-loading globally for the user
24078 (@pxref{Home Directory Init File}). While it is improbable, you could also
24079 use system init file instead (@pxref{System-wide configuration}).
24082 This setting applies to the file names as entered by user. If no entry matches
24083 @value{GDBN} tries as a last resort to also resolve all the file names into
24084 their canonical form (typically resolving symbolic links) and compare the
24085 entries again. @value{GDBN} already canonicalizes most of the filenames on its
24086 own before starting the comparison so a canonical form of directories is
24087 recommended to be entered.
24089 @node Auto-loading verbose mode
24090 @subsection Displaying files tried for auto-load
24091 @cindex auto-loading verbose mode
24093 For better visibility of all the file locations where you can place scripts to
24094 be auto-loaded with inferior --- or to protect yourself against accidental
24095 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
24096 all the files attempted to be loaded. Both existing and non-existing files may
24099 For example the list of directories from which it is safe to auto-load files
24100 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
24101 may not be too obvious while setting it up.
24104 (gdb) set debug auto-load on
24105 (gdb) file ~/src/t/true
24106 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
24107 for objfile "/tmp/true".
24108 auto-load: Updating directories of "/usr:/opt".
24109 auto-load: Using directory "/usr".
24110 auto-load: Using directory "/opt".
24111 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
24112 by your `auto-load safe-path' set to "/usr:/opt".
24116 @anchor{set debug auto-load}
24117 @kindex set debug auto-load
24118 @item set debug auto-load [on|off]
24119 Set whether to print the filenames attempted to be auto-loaded.
24121 @anchor{show debug auto-load}
24122 @kindex show debug auto-load
24123 @item show debug auto-load
24124 Show whether printing of the filenames attempted to be auto-loaded is turned
24128 @node Messages/Warnings
24129 @section Optional Warnings and Messages
24131 @cindex verbose operation
24132 @cindex optional warnings
24133 By default, @value{GDBN} is silent about its inner workings. If you are
24134 running on a slow machine, you may want to use the @code{set verbose}
24135 command. This makes @value{GDBN} tell you when it does a lengthy
24136 internal operation, so you will not think it has crashed.
24138 Currently, the messages controlled by @code{set verbose} are those
24139 which announce that the symbol table for a source file is being read;
24140 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
24143 @kindex set verbose
24144 @item set verbose on
24145 Enables @value{GDBN} output of certain informational messages.
24147 @item set verbose off
24148 Disables @value{GDBN} output of certain informational messages.
24150 @kindex show verbose
24152 Displays whether @code{set verbose} is on or off.
24155 By default, if @value{GDBN} encounters bugs in the symbol table of an
24156 object file, it is silent; but if you are debugging a compiler, you may
24157 find this information useful (@pxref{Symbol Errors, ,Errors Reading
24162 @kindex set complaints
24163 @item set complaints @var{limit}
24164 Permits @value{GDBN} to output @var{limit} complaints about each type of
24165 unusual symbols before becoming silent about the problem. Set
24166 @var{limit} to zero to suppress all complaints; set it to a large number
24167 to prevent complaints from being suppressed.
24169 @kindex show complaints
24170 @item show complaints
24171 Displays how many symbol complaints @value{GDBN} is permitted to produce.
24175 @anchor{confirmation requests}
24176 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
24177 lot of stupid questions to confirm certain commands. For example, if
24178 you try to run a program which is already running:
24182 The program being debugged has been started already.
24183 Start it from the beginning? (y or n)
24186 If you are willing to unflinchingly face the consequences of your own
24187 commands, you can disable this ``feature'':
24191 @kindex set confirm
24193 @cindex confirmation
24194 @cindex stupid questions
24195 @item set confirm off
24196 Disables confirmation requests. Note that running @value{GDBN} with
24197 the @option{--batch} option (@pxref{Mode Options, -batch}) also
24198 automatically disables confirmation requests.
24200 @item set confirm on
24201 Enables confirmation requests (the default).
24203 @kindex show confirm
24205 Displays state of confirmation requests.
24209 @cindex command tracing
24210 If you need to debug user-defined commands or sourced files you may find it
24211 useful to enable @dfn{command tracing}. In this mode each command will be
24212 printed as it is executed, prefixed with one or more @samp{+} symbols, the
24213 quantity denoting the call depth of each command.
24216 @kindex set trace-commands
24217 @cindex command scripts, debugging
24218 @item set trace-commands on
24219 Enable command tracing.
24220 @item set trace-commands off
24221 Disable command tracing.
24222 @item show trace-commands
24223 Display the current state of command tracing.
24226 @node Debugging Output
24227 @section Optional Messages about Internal Happenings
24228 @cindex optional debugging messages
24230 @value{GDBN} has commands that enable optional debugging messages from
24231 various @value{GDBN} subsystems; normally these commands are of
24232 interest to @value{GDBN} maintainers, or when reporting a bug. This
24233 section documents those commands.
24236 @kindex set exec-done-display
24237 @item set exec-done-display
24238 Turns on or off the notification of asynchronous commands'
24239 completion. When on, @value{GDBN} will print a message when an
24240 asynchronous command finishes its execution. The default is off.
24241 @kindex show exec-done-display
24242 @item show exec-done-display
24243 Displays the current setting of asynchronous command completion
24246 @cindex ARM AArch64
24247 @item set debug aarch64
24248 Turns on or off display of debugging messages related to ARM AArch64.
24249 The default is off.
24251 @item show debug aarch64
24252 Displays the current state of displaying debugging messages related to
24254 @cindex gdbarch debugging info
24255 @cindex architecture debugging info
24256 @item set debug arch
24257 Turns on or off display of gdbarch debugging info. The default is off
24258 @item show debug arch
24259 Displays the current state of displaying gdbarch debugging info.
24260 @item set debug aix-solib
24261 @cindex AIX shared library debugging
24262 Control display of debugging messages from the AIX shared library
24263 support module. The default is off.
24264 @item show debug aix-thread
24265 Show the current state of displaying AIX shared library debugging messages.
24266 @item set debug aix-thread
24267 @cindex AIX threads
24268 Display debugging messages about inner workings of the AIX thread
24270 @item show debug aix-thread
24271 Show the current state of AIX thread debugging info display.
24272 @item set debug check-physname
24274 Check the results of the ``physname'' computation. When reading DWARF
24275 debugging information for C@t{++}, @value{GDBN} attempts to compute
24276 each entity's name. @value{GDBN} can do this computation in two
24277 different ways, depending on exactly what information is present.
24278 When enabled, this setting causes @value{GDBN} to compute the names
24279 both ways and display any discrepancies.
24280 @item show debug check-physname
24281 Show the current state of ``physname'' checking.
24282 @item set debug coff-pe-read
24283 @cindex COFF/PE exported symbols
24284 Control display of debugging messages related to reading of COFF/PE
24285 exported symbols. The default is off.
24286 @item show debug coff-pe-read
24287 Displays the current state of displaying debugging messages related to
24288 reading of COFF/PE exported symbols.
24289 @item set debug dwarf-die
24291 Dump DWARF DIEs after they are read in.
24292 The value is the number of nesting levels to print.
24293 A value of zero turns off the display.
24294 @item show debug dwarf-die
24295 Show the current state of DWARF DIE debugging.
24296 @item set debug dwarf-line
24297 @cindex DWARF Line Tables
24298 Turns on or off display of debugging messages related to reading
24299 DWARF line tables. The default is 0 (off).
24300 A value of 1 provides basic information.
24301 A value greater than 1 provides more verbose information.
24302 @item show debug dwarf-line
24303 Show the current state of DWARF line table debugging.
24304 @item set debug dwarf-read
24305 @cindex DWARF Reading
24306 Turns on or off display of debugging messages related to reading
24307 DWARF debug info. The default is 0 (off).
24308 A value of 1 provides basic information.
24309 A value greater than 1 provides more verbose information.
24310 @item show debug dwarf-read
24311 Show the current state of DWARF reader debugging.
24312 @item set debug displaced
24313 @cindex displaced stepping debugging info
24314 Turns on or off display of @value{GDBN} debugging info for the
24315 displaced stepping support. The default is off.
24316 @item show debug displaced
24317 Displays the current state of displaying @value{GDBN} debugging info
24318 related to displaced stepping.
24319 @item set debug event
24320 @cindex event debugging info
24321 Turns on or off display of @value{GDBN} event debugging info. The
24323 @item show debug event
24324 Displays the current state of displaying @value{GDBN} event debugging
24326 @item set debug expression
24327 @cindex expression debugging info
24328 Turns on or off display of debugging info about @value{GDBN}
24329 expression parsing. The default is off.
24330 @item show debug expression
24331 Displays the current state of displaying debugging info about
24332 @value{GDBN} expression parsing.
24333 @item set debug fbsd-lwp
24334 @cindex FreeBSD LWP debug messages
24335 Turns on or off debugging messages from the FreeBSD LWP debug support.
24336 @item show debug fbsd-lwp
24337 Show the current state of FreeBSD LWP debugging messages.
24338 @item set debug frame
24339 @cindex frame debugging info
24340 Turns on or off display of @value{GDBN} frame debugging info. The
24342 @item show debug frame
24343 Displays the current state of displaying @value{GDBN} frame debugging
24345 @item set debug gnu-nat
24346 @cindex @sc{gnu}/Hurd debug messages
24347 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
24348 @item show debug gnu-nat
24349 Show the current state of @sc{gnu}/Hurd debugging messages.
24350 @item set debug infrun
24351 @cindex inferior debugging info
24352 Turns on or off display of @value{GDBN} debugging info for running the inferior.
24353 The default is off. @file{infrun.c} contains GDB's runtime state machine used
24354 for implementing operations such as single-stepping the inferior.
24355 @item show debug infrun
24356 Displays the current state of @value{GDBN} inferior debugging.
24357 @item set debug jit
24358 @cindex just-in-time compilation, debugging messages
24359 Turn on or off debugging messages from JIT debug support.
24360 @item show debug jit
24361 Displays the current state of @value{GDBN} JIT debugging.
24362 @item set debug lin-lwp
24363 @cindex @sc{gnu}/Linux LWP debug messages
24364 @cindex Linux lightweight processes
24365 Turn on or off debugging messages from the Linux LWP debug support.
24366 @item show debug lin-lwp
24367 Show the current state of Linux LWP debugging messages.
24368 @item set debug linux-namespaces
24369 @cindex @sc{gnu}/Linux namespaces debug messages
24370 Turn on or off debugging messages from the Linux namespaces debug support.
24371 @item show debug linux-namespaces
24372 Show the current state of Linux namespaces debugging messages.
24373 @item set debug mach-o
24374 @cindex Mach-O symbols processing
24375 Control display of debugging messages related to Mach-O symbols
24376 processing. The default is off.
24377 @item show debug mach-o
24378 Displays the current state of displaying debugging messages related to
24379 reading of COFF/PE exported symbols.
24380 @item set debug notification
24381 @cindex remote async notification debugging info
24382 Turn on or off debugging messages about remote async notification.
24383 The default is off.
24384 @item show debug notification
24385 Displays the current state of remote async notification debugging messages.
24386 @item set debug observer
24387 @cindex observer debugging info
24388 Turns on or off display of @value{GDBN} observer debugging. This
24389 includes info such as the notification of observable events.
24390 @item show debug observer
24391 Displays the current state of observer debugging.
24392 @item set debug overload
24393 @cindex C@t{++} overload debugging info
24394 Turns on or off display of @value{GDBN} C@t{++} overload debugging
24395 info. This includes info such as ranking of functions, etc. The default
24397 @item show debug overload
24398 Displays the current state of displaying @value{GDBN} C@t{++} overload
24400 @cindex expression parser, debugging info
24401 @cindex debug expression parser
24402 @item set debug parser
24403 Turns on or off the display of expression parser debugging output.
24404 Internally, this sets the @code{yydebug} variable in the expression
24405 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
24406 details. The default is off.
24407 @item show debug parser
24408 Show the current state of expression parser debugging.
24409 @cindex packets, reporting on stdout
24410 @cindex serial connections, debugging
24411 @cindex debug remote protocol
24412 @cindex remote protocol debugging
24413 @cindex display remote packets
24414 @item set debug remote
24415 Turns on or off display of reports on all packets sent back and forth across
24416 the serial line to the remote machine. The info is printed on the
24417 @value{GDBN} standard output stream. The default is off.
24418 @item show debug remote
24419 Displays the state of display of remote packets.
24421 @item set debug separate-debug-file
24422 Turns on or off display of debug output about separate debug file search.
24423 @item show debug separate-debug-file
24424 Displays the state of separate debug file search debug output.
24426 @item set debug serial
24427 Turns on or off display of @value{GDBN} serial debugging info. The
24429 @item show debug serial
24430 Displays the current state of displaying @value{GDBN} serial debugging
24432 @item set debug solib-frv
24433 @cindex FR-V shared-library debugging
24434 Turn on or off debugging messages for FR-V shared-library code.
24435 @item show debug solib-frv
24436 Display the current state of FR-V shared-library code debugging
24438 @item set debug symbol-lookup
24439 @cindex symbol lookup
24440 Turns on or off display of debugging messages related to symbol lookup.
24441 The default is 0 (off).
24442 A value of 1 provides basic information.
24443 A value greater than 1 provides more verbose information.
24444 @item show debug symbol-lookup
24445 Show the current state of symbol lookup debugging messages.
24446 @item set debug symfile
24447 @cindex symbol file functions
24448 Turns on or off display of debugging messages related to symbol file functions.
24449 The default is off. @xref{Files}.
24450 @item show debug symfile
24451 Show the current state of symbol file debugging messages.
24452 @item set debug symtab-create
24453 @cindex symbol table creation
24454 Turns on or off display of debugging messages related to symbol table creation.
24455 The default is 0 (off).
24456 A value of 1 provides basic information.
24457 A value greater than 1 provides more verbose information.
24458 @item show debug symtab-create
24459 Show the current state of symbol table creation debugging.
24460 @item set debug target
24461 @cindex target debugging info
24462 Turns on or off display of @value{GDBN} target debugging info. This info
24463 includes what is going on at the target level of GDB, as it happens. The
24464 default is 0. Set it to 1 to track events, and to 2 to also track the
24465 value of large memory transfers.
24466 @item show debug target
24467 Displays the current state of displaying @value{GDBN} target debugging
24469 @item set debug timestamp
24470 @cindex timestampping debugging info
24471 Turns on or off display of timestamps with @value{GDBN} debugging info.
24472 When enabled, seconds and microseconds are displayed before each debugging
24474 @item show debug timestamp
24475 Displays the current state of displaying timestamps with @value{GDBN}
24477 @item set debug varobj
24478 @cindex variable object debugging info
24479 Turns on or off display of @value{GDBN} variable object debugging
24480 info. The default is off.
24481 @item show debug varobj
24482 Displays the current state of displaying @value{GDBN} variable object
24484 @item set debug xml
24485 @cindex XML parser debugging
24486 Turn on or off debugging messages for built-in XML parsers.
24487 @item show debug xml
24488 Displays the current state of XML debugging messages.
24491 @node Other Misc Settings
24492 @section Other Miscellaneous Settings
24493 @cindex miscellaneous settings
24496 @kindex set interactive-mode
24497 @item set interactive-mode
24498 If @code{on}, forces @value{GDBN} to assume that GDB was started
24499 in a terminal. In practice, this means that @value{GDBN} should wait
24500 for the user to answer queries generated by commands entered at
24501 the command prompt. If @code{off}, forces @value{GDBN} to operate
24502 in the opposite mode, and it uses the default answers to all queries.
24503 If @code{auto} (the default), @value{GDBN} tries to determine whether
24504 its standard input is a terminal, and works in interactive-mode if it
24505 is, non-interactively otherwise.
24507 In the vast majority of cases, the debugger should be able to guess
24508 correctly which mode should be used. But this setting can be useful
24509 in certain specific cases, such as running a MinGW @value{GDBN}
24510 inside a cygwin window.
24512 @kindex show interactive-mode
24513 @item show interactive-mode
24514 Displays whether the debugger is operating in interactive mode or not.
24517 @node Extending GDB
24518 @chapter Extending @value{GDBN}
24519 @cindex extending GDB
24521 @value{GDBN} provides several mechanisms for extension.
24522 @value{GDBN} also provides the ability to automatically load
24523 extensions when it reads a file for debugging. This allows the
24524 user to automatically customize @value{GDBN} for the program
24528 * Sequences:: Canned Sequences of @value{GDBN} Commands
24529 * Python:: Extending @value{GDBN} using Python
24530 * Guile:: Extending @value{GDBN} using Guile
24531 * Auto-loading extensions:: Automatically loading extensions
24532 * Multiple Extension Languages:: Working with multiple extension languages
24533 * Aliases:: Creating new spellings of existing commands
24536 To facilitate the use of extension languages, @value{GDBN} is capable
24537 of evaluating the contents of a file. When doing so, @value{GDBN}
24538 can recognize which extension language is being used by looking at
24539 the filename extension. Files with an unrecognized filename extension
24540 are always treated as a @value{GDBN} Command Files.
24541 @xref{Command Files,, Command files}.
24543 You can control how @value{GDBN} evaluates these files with the following
24547 @kindex set script-extension
24548 @kindex show script-extension
24549 @item set script-extension off
24550 All scripts are always evaluated as @value{GDBN} Command Files.
24552 @item set script-extension soft
24553 The debugger determines the scripting language based on filename
24554 extension. If this scripting language is supported, @value{GDBN}
24555 evaluates the script using that language. Otherwise, it evaluates
24556 the file as a @value{GDBN} Command File.
24558 @item set script-extension strict
24559 The debugger determines the scripting language based on filename
24560 extension, and evaluates the script using that language. If the
24561 language is not supported, then the evaluation fails.
24563 @item show script-extension
24564 Display the current value of the @code{script-extension} option.
24569 @section Canned Sequences of Commands
24571 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
24572 Command Lists}), @value{GDBN} provides two ways to store sequences of
24573 commands for execution as a unit: user-defined commands and command
24577 * Define:: How to define your own commands
24578 * Hooks:: Hooks for user-defined commands
24579 * Command Files:: How to write scripts of commands to be stored in a file
24580 * Output:: Commands for controlled output
24581 * Auto-loading sequences:: Controlling auto-loaded command files
24585 @subsection User-defined Commands
24587 @cindex user-defined command
24588 @cindex arguments, to user-defined commands
24589 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24590 which you assign a new name as a command. This is done with the
24591 @code{define} command. User commands may accept an unlimited number of arguments
24592 separated by whitespace. Arguments are accessed within the user command
24593 via @code{$arg0@dots{}$argN}. A trivial example:
24597 print $arg0 + $arg1 + $arg2
24602 To execute the command use:
24609 This defines the command @code{adder}, which prints the sum of
24610 its three arguments. Note the arguments are text substitutions, so they may
24611 reference variables, use complex expressions, or even perform inferior
24614 @cindex argument count in user-defined commands
24615 @cindex how many arguments (user-defined commands)
24616 In addition, @code{$argc} may be used to find out how many arguments have
24622 print $arg0 + $arg1
24625 print $arg0 + $arg1 + $arg2
24630 Combining with the @code{eval} command (@pxref{eval}) makes it easier
24631 to process a variable number of arguments:
24638 eval "set $sum = $sum + $arg%d", $i
24648 @item define @var{commandname}
24649 Define a command named @var{commandname}. If there is already a command
24650 by that name, you are asked to confirm that you want to redefine it.
24651 The argument @var{commandname} may be a bare command name consisting of letters,
24652 numbers, dashes, and underscores. It may also start with any predefined
24653 prefix command. For example, @samp{define target my-target} creates
24654 a user-defined @samp{target my-target} command.
24656 The definition of the command is made up of other @value{GDBN} command lines,
24657 which are given following the @code{define} command. The end of these
24658 commands is marked by a line containing @code{end}.
24661 @kindex end@r{ (user-defined commands)}
24662 @item document @var{commandname}
24663 Document the user-defined command @var{commandname}, so that it can be
24664 accessed by @code{help}. The command @var{commandname} must already be
24665 defined. This command reads lines of documentation just as @code{define}
24666 reads the lines of the command definition, ending with @code{end}.
24667 After the @code{document} command is finished, @code{help} on command
24668 @var{commandname} displays the documentation you have written.
24670 You may use the @code{document} command again to change the
24671 documentation of a command. Redefining the command with @code{define}
24672 does not change the documentation.
24674 @kindex dont-repeat
24675 @cindex don't repeat command
24677 Used inside a user-defined command, this tells @value{GDBN} that this
24678 command should not be repeated when the user hits @key{RET}
24679 (@pxref{Command Syntax, repeat last command}).
24681 @kindex help user-defined
24682 @item help user-defined
24683 List all user-defined commands and all python commands defined in class
24684 COMAND_USER. The first line of the documentation or docstring is
24689 @itemx show user @var{commandname}
24690 Display the @value{GDBN} commands used to define @var{commandname} (but
24691 not its documentation). If no @var{commandname} is given, display the
24692 definitions for all user-defined commands.
24693 This does not work for user-defined python commands.
24695 @cindex infinite recursion in user-defined commands
24696 @kindex show max-user-call-depth
24697 @kindex set max-user-call-depth
24698 @item show max-user-call-depth
24699 @itemx set max-user-call-depth
24700 The value of @code{max-user-call-depth} controls how many recursion
24701 levels are allowed in user-defined commands before @value{GDBN} suspects an
24702 infinite recursion and aborts the command.
24703 This does not apply to user-defined python commands.
24706 In addition to the above commands, user-defined commands frequently
24707 use control flow commands, described in @ref{Command Files}.
24709 When user-defined commands are executed, the
24710 commands of the definition are not printed. An error in any command
24711 stops execution of the user-defined command.
24713 If used interactively, commands that would ask for confirmation proceed
24714 without asking when used inside a user-defined command. Many @value{GDBN}
24715 commands that normally print messages to say what they are doing omit the
24716 messages when used in a user-defined command.
24719 @subsection User-defined Command Hooks
24720 @cindex command hooks
24721 @cindex hooks, for commands
24722 @cindex hooks, pre-command
24725 You may define @dfn{hooks}, which are a special kind of user-defined
24726 command. Whenever you run the command @samp{foo}, if the user-defined
24727 command @samp{hook-foo} exists, it is executed (with no arguments)
24728 before that command.
24730 @cindex hooks, post-command
24732 A hook may also be defined which is run after the command you executed.
24733 Whenever you run the command @samp{foo}, if the user-defined command
24734 @samp{hookpost-foo} exists, it is executed (with no arguments) after
24735 that command. Post-execution hooks may exist simultaneously with
24736 pre-execution hooks, for the same command.
24738 It is valid for a hook to call the command which it hooks. If this
24739 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24741 @c It would be nice if hookpost could be passed a parameter indicating
24742 @c if the command it hooks executed properly or not. FIXME!
24744 @kindex stop@r{, a pseudo-command}
24745 In addition, a pseudo-command, @samp{stop} exists. Defining
24746 (@samp{hook-stop}) makes the associated commands execute every time
24747 execution stops in your program: before breakpoint commands are run,
24748 displays are printed, or the stack frame is printed.
24750 For example, to ignore @code{SIGALRM} signals while
24751 single-stepping, but treat them normally during normal execution,
24756 handle SIGALRM nopass
24760 handle SIGALRM pass
24763 define hook-continue
24764 handle SIGALRM pass
24768 As a further example, to hook at the beginning and end of the @code{echo}
24769 command, and to add extra text to the beginning and end of the message,
24777 define hookpost-echo
24781 (@value{GDBP}) echo Hello World
24782 <<<---Hello World--->>>
24787 You can define a hook for any single-word command in @value{GDBN}, but
24788 not for command aliases; you should define a hook for the basic command
24789 name, e.g.@: @code{backtrace} rather than @code{bt}.
24790 @c FIXME! So how does Joe User discover whether a command is an alias
24792 You can hook a multi-word command by adding @code{hook-} or
24793 @code{hookpost-} to the last word of the command, e.g.@:
24794 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24796 If an error occurs during the execution of your hook, execution of
24797 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24798 (before the command that you actually typed had a chance to run).
24800 If you try to define a hook which does not match any known command, you
24801 get a warning from the @code{define} command.
24803 @node Command Files
24804 @subsection Command Files
24806 @cindex command files
24807 @cindex scripting commands
24808 A command file for @value{GDBN} is a text file made of lines that are
24809 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24810 also be included. An empty line in a command file does nothing; it
24811 does not mean to repeat the last command, as it would from the
24814 You can request the execution of a command file with the @code{source}
24815 command. Note that the @code{source} command is also used to evaluate
24816 scripts that are not Command Files. The exact behavior can be configured
24817 using the @code{script-extension} setting.
24818 @xref{Extending GDB,, Extending GDB}.
24822 @cindex execute commands from a file
24823 @item source [-s] [-v] @var{filename}
24824 Execute the command file @var{filename}.
24827 The lines in a command file are generally executed sequentially,
24828 unless the order of execution is changed by one of the
24829 @emph{flow-control commands} described below. The commands are not
24830 printed as they are executed. An error in any command terminates
24831 execution of the command file and control is returned to the console.
24833 @value{GDBN} first searches for @var{filename} in the current directory.
24834 If the file is not found there, and @var{filename} does not specify a
24835 directory, then @value{GDBN} also looks for the file on the source search path
24836 (specified with the @samp{directory} command);
24837 except that @file{$cdir} is not searched because the compilation directory
24838 is not relevant to scripts.
24840 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
24841 on the search path even if @var{filename} specifies a directory.
24842 The search is done by appending @var{filename} to each element of the
24843 search path. So, for example, if @var{filename} is @file{mylib/myscript}
24844 and the search path contains @file{/home/user} then @value{GDBN} will
24845 look for the script @file{/home/user/mylib/myscript}.
24846 The search is also done if @var{filename} is an absolute path.
24847 For example, if @var{filename} is @file{/tmp/myscript} and
24848 the search path contains @file{/home/user} then @value{GDBN} will
24849 look for the script @file{/home/user/tmp/myscript}.
24850 For DOS-like systems, if @var{filename} contains a drive specification,
24851 it is stripped before concatenation. For example, if @var{filename} is
24852 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
24853 will look for the script @file{c:/tmp/myscript}.
24855 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
24856 each command as it is executed. The option must be given before
24857 @var{filename}, and is interpreted as part of the filename anywhere else.
24859 Commands that would ask for confirmation if used interactively proceed
24860 without asking when used in a command file. Many @value{GDBN} commands that
24861 normally print messages to say what they are doing omit the messages
24862 when called from command files.
24864 @value{GDBN} also accepts command input from standard input. In this
24865 mode, normal output goes to standard output and error output goes to
24866 standard error. Errors in a command file supplied on standard input do
24867 not terminate execution of the command file---execution continues with
24871 gdb < cmds > log 2>&1
24874 (The syntax above will vary depending on the shell used.) This example
24875 will execute commands from the file @file{cmds}. All output and errors
24876 would be directed to @file{log}.
24878 Since commands stored on command files tend to be more general than
24879 commands typed interactively, they frequently need to deal with
24880 complicated situations, such as different or unexpected values of
24881 variables and symbols, changes in how the program being debugged is
24882 built, etc. @value{GDBN} provides a set of flow-control commands to
24883 deal with these complexities. Using these commands, you can write
24884 complex scripts that loop over data structures, execute commands
24885 conditionally, etc.
24892 This command allows to include in your script conditionally executed
24893 commands. The @code{if} command takes a single argument, which is an
24894 expression to evaluate. It is followed by a series of commands that
24895 are executed only if the expression is true (its value is nonzero).
24896 There can then optionally be an @code{else} line, followed by a series
24897 of commands that are only executed if the expression was false. The
24898 end of the list is marked by a line containing @code{end}.
24902 This command allows to write loops. Its syntax is similar to
24903 @code{if}: the command takes a single argument, which is an expression
24904 to evaluate, and must be followed by the commands to execute, one per
24905 line, terminated by an @code{end}. These commands are called the
24906 @dfn{body} of the loop. The commands in the body of @code{while} are
24907 executed repeatedly as long as the expression evaluates to true.
24911 This command exits the @code{while} loop in whose body it is included.
24912 Execution of the script continues after that @code{while}s @code{end}
24915 @kindex loop_continue
24916 @item loop_continue
24917 This command skips the execution of the rest of the body of commands
24918 in the @code{while} loop in whose body it is included. Execution
24919 branches to the beginning of the @code{while} loop, where it evaluates
24920 the controlling expression.
24922 @kindex end@r{ (if/else/while commands)}
24924 Terminate the block of commands that are the body of @code{if},
24925 @code{else}, or @code{while} flow-control commands.
24930 @subsection Commands for Controlled Output
24932 During the execution of a command file or a user-defined command, normal
24933 @value{GDBN} output is suppressed; the only output that appears is what is
24934 explicitly printed by the commands in the definition. This section
24935 describes three commands useful for generating exactly the output you
24940 @item echo @var{text}
24941 @c I do not consider backslash-space a standard C escape sequence
24942 @c because it is not in ANSI.
24943 Print @var{text}. Nonprinting characters can be included in
24944 @var{text} using C escape sequences, such as @samp{\n} to print a
24945 newline. @strong{No newline is printed unless you specify one.}
24946 In addition to the standard C escape sequences, a backslash followed
24947 by a space stands for a space. This is useful for displaying a
24948 string with spaces at the beginning or the end, since leading and
24949 trailing spaces are otherwise trimmed from all arguments.
24950 To print @samp{@w{ }and foo =@w{ }}, use the command
24951 @samp{echo \@w{ }and foo = \@w{ }}.
24953 A backslash at the end of @var{text} can be used, as in C, to continue
24954 the command onto subsequent lines. For example,
24957 echo This is some text\n\
24958 which is continued\n\
24959 onto several lines.\n
24962 produces the same output as
24965 echo This is some text\n
24966 echo which is continued\n
24967 echo onto several lines.\n
24971 @item output @var{expression}
24972 Print the value of @var{expression} and nothing but that value: no
24973 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24974 value history either. @xref{Expressions, ,Expressions}, for more information
24977 @item output/@var{fmt} @var{expression}
24978 Print the value of @var{expression} in format @var{fmt}. You can use
24979 the same formats as for @code{print}. @xref{Output Formats,,Output
24980 Formats}, for more information.
24983 @item printf @var{template}, @var{expressions}@dots{}
24984 Print the values of one or more @var{expressions} under the control of
24985 the string @var{template}. To print several values, make
24986 @var{expressions} be a comma-separated list of individual expressions,
24987 which may be either numbers or pointers. Their values are printed as
24988 specified by @var{template}, exactly as a C program would do by
24989 executing the code below:
24992 printf (@var{template}, @var{expressions}@dots{});
24995 As in @code{C} @code{printf}, ordinary characters in @var{template}
24996 are printed verbatim, while @dfn{conversion specification} introduced
24997 by the @samp{%} character cause subsequent @var{expressions} to be
24998 evaluated, their values converted and formatted according to type and
24999 style information encoded in the conversion specifications, and then
25002 For example, you can print two values in hex like this:
25005 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
25008 @code{printf} supports all the standard @code{C} conversion
25009 specifications, including the flags and modifiers between the @samp{%}
25010 character and the conversion letter, with the following exceptions:
25014 The argument-ordering modifiers, such as @samp{2$}, are not supported.
25017 The modifier @samp{*} is not supported for specifying precision or
25021 The @samp{'} flag (for separation of digits into groups according to
25022 @code{LC_NUMERIC'}) is not supported.
25025 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
25029 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
25032 The conversion letters @samp{a} and @samp{A} are not supported.
25036 Note that the @samp{ll} type modifier is supported only if the
25037 underlying @code{C} implementation used to build @value{GDBN} supports
25038 the @code{long long int} type, and the @samp{L} type modifier is
25039 supported only if @code{long double} type is available.
25041 As in @code{C}, @code{printf} supports simple backslash-escape
25042 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
25043 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
25044 single character. Octal and hexadecimal escape sequences are not
25047 Additionally, @code{printf} supports conversion specifications for DFP
25048 (@dfn{Decimal Floating Point}) types using the following length modifiers
25049 together with a floating point specifier.
25054 @samp{H} for printing @code{Decimal32} types.
25057 @samp{D} for printing @code{Decimal64} types.
25060 @samp{DD} for printing @code{Decimal128} types.
25063 If the underlying @code{C} implementation used to build @value{GDBN} has
25064 support for the three length modifiers for DFP types, other modifiers
25065 such as width and precision will also be available for @value{GDBN} to use.
25067 In case there is no such @code{C} support, no additional modifiers will be
25068 available and the value will be printed in the standard way.
25070 Here's an example of printing DFP types using the above conversion letters:
25072 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
25077 @item eval @var{template}, @var{expressions}@dots{}
25078 Convert the values of one or more @var{expressions} under the control of
25079 the string @var{template} to a command line, and call it.
25083 @node Auto-loading sequences
25084 @subsection Controlling auto-loading native @value{GDBN} scripts
25085 @cindex native script auto-loading
25087 When a new object file is read (for example, due to the @code{file}
25088 command, or because the inferior has loaded a shared library),
25089 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
25090 @xref{Auto-loading extensions}.
25092 Auto-loading can be enabled or disabled,
25093 and the list of auto-loaded scripts can be printed.
25096 @anchor{set auto-load gdb-scripts}
25097 @kindex set auto-load gdb-scripts
25098 @item set auto-load gdb-scripts [on|off]
25099 Enable or disable the auto-loading of canned sequences of commands scripts.
25101 @anchor{show auto-load gdb-scripts}
25102 @kindex show auto-load gdb-scripts
25103 @item show auto-load gdb-scripts
25104 Show whether auto-loading of canned sequences of commands scripts is enabled or
25107 @anchor{info auto-load gdb-scripts}
25108 @kindex info auto-load gdb-scripts
25109 @cindex print list of auto-loaded canned sequences of commands scripts
25110 @item info auto-load gdb-scripts [@var{regexp}]
25111 Print the list of all canned sequences of commands scripts that @value{GDBN}
25115 If @var{regexp} is supplied only canned sequences of commands scripts with
25116 matching names are printed.
25118 @c Python docs live in a separate file.
25119 @include python.texi
25121 @c Guile docs live in a separate file.
25122 @include guile.texi
25124 @node Auto-loading extensions
25125 @section Auto-loading extensions
25126 @cindex auto-loading extensions
25128 @value{GDBN} provides two mechanisms for automatically loading extensions
25129 when a new object file is read (for example, due to the @code{file}
25130 command, or because the inferior has loaded a shared library):
25131 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
25132 section of modern file formats like ELF.
25135 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
25136 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
25137 * Which flavor to choose?::
25140 The auto-loading feature is useful for supplying application-specific
25141 debugging commands and features.
25143 Auto-loading can be enabled or disabled,
25144 and the list of auto-loaded scripts can be printed.
25145 See the @samp{auto-loading} section of each extension language
25146 for more information.
25147 For @value{GDBN} command files see @ref{Auto-loading sequences}.
25148 For Python files see @ref{Python Auto-loading}.
25150 Note that loading of this script file also requires accordingly configured
25151 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25153 @node objfile-gdbdotext file
25154 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
25155 @cindex @file{@var{objfile}-gdb.gdb}
25156 @cindex @file{@var{objfile}-gdb.py}
25157 @cindex @file{@var{objfile}-gdb.scm}
25159 When a new object file is read, @value{GDBN} looks for a file named
25160 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
25161 where @var{objfile} is the object file's name and
25162 where @var{ext} is the file extension for the extension language:
25165 @item @file{@var{objfile}-gdb.gdb}
25166 GDB's own command language
25167 @item @file{@var{objfile}-gdb.py}
25169 @item @file{@var{objfile}-gdb.scm}
25173 @var{script-name} is formed by ensuring that the file name of @var{objfile}
25174 is absolute, following all symlinks, and resolving @code{.} and @code{..}
25175 components, and appending the @file{-gdb.@var{ext}} suffix.
25176 If this file exists and is readable, @value{GDBN} will evaluate it as a
25177 script in the specified extension language.
25179 If this file does not exist, then @value{GDBN} will look for
25180 @var{script-name} file in all of the directories as specified below.
25182 Note that loading of these files requires an accordingly configured
25183 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25185 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
25186 scripts normally according to its @file{.exe} filename. But if no scripts are
25187 found @value{GDBN} also tries script filenames matching the object file without
25188 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
25189 is attempted on any platform. This makes the script filenames compatible
25190 between Unix and MS-Windows hosts.
25193 @anchor{set auto-load scripts-directory}
25194 @kindex set auto-load scripts-directory
25195 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
25196 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
25197 may be delimited by the host platform path separator in use
25198 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
25200 Each entry here needs to be covered also by the security setting
25201 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
25203 @anchor{with-auto-load-dir}
25204 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
25205 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
25206 configuration option @option{--with-auto-load-dir}.
25208 Any reference to @file{$debugdir} will get replaced by
25209 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
25210 reference to @file{$datadir} will get replaced by @var{data-directory} which is
25211 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
25212 @file{$datadir} must be placed as a directory component --- either alone or
25213 delimited by @file{/} or @file{\} directory separators, depending on the host
25216 The list of directories uses path separator (@samp{:} on GNU and Unix
25217 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25218 to the @env{PATH} environment variable.
25220 @anchor{show auto-load scripts-directory}
25221 @kindex show auto-load scripts-directory
25222 @item show auto-load scripts-directory
25223 Show @value{GDBN} auto-loaded scripts location.
25225 @anchor{add-auto-load-scripts-directory}
25226 @kindex add-auto-load-scripts-directory
25227 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
25228 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
25229 Multiple entries may be delimited by the host platform path separator in use.
25232 @value{GDBN} does not track which files it has already auto-loaded this way.
25233 @value{GDBN} will load the associated script every time the corresponding
25234 @var{objfile} is opened.
25235 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
25236 is evaluated more than once.
25238 @node dotdebug_gdb_scripts section
25239 @subsection The @code{.debug_gdb_scripts} section
25240 @cindex @code{.debug_gdb_scripts} section
25242 For systems using file formats like ELF and COFF,
25243 when @value{GDBN} loads a new object file
25244 it will look for a special section named @code{.debug_gdb_scripts}.
25245 If this section exists, its contents is a list of null-terminated entries
25246 specifying scripts to load. Each entry begins with a non-null prefix byte that
25247 specifies the kind of entry, typically the extension language and whether the
25248 script is in a file or inlined in @code{.debug_gdb_scripts}.
25250 The following entries are supported:
25253 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
25254 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
25255 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
25256 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
25259 @subsubsection Script File Entries
25261 If the entry specifies a file, @value{GDBN} will look for the file first
25262 in the current directory and then along the source search path
25263 (@pxref{Source Path, ,Specifying Source Directories}),
25264 except that @file{$cdir} is not searched, since the compilation
25265 directory is not relevant to scripts.
25267 File entries can be placed in section @code{.debug_gdb_scripts} with,
25268 for example, this GCC macro for Python scripts.
25271 /* Note: The "MS" section flags are to remove duplicates. */
25272 #define DEFINE_GDB_PY_SCRIPT(script_name) \
25274 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
25275 .byte 1 /* Python */\n\
25276 .asciz \"" script_name "\"\n\
25282 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
25283 Then one can reference the macro in a header or source file like this:
25286 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
25289 The script name may include directories if desired.
25291 Note that loading of this script file also requires accordingly configured
25292 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25294 If the macro invocation is put in a header, any application or library
25295 using this header will get a reference to the specified script,
25296 and with the use of @code{"MS"} attributes on the section, the linker
25297 will remove duplicates.
25299 @subsubsection Script Text Entries
25301 Script text entries allow to put the executable script in the entry
25302 itself instead of loading it from a file.
25303 The first line of the entry, everything after the prefix byte and up to
25304 the first newline (@code{0xa}) character, is the script name, and must not
25305 contain any kind of space character, e.g., spaces or tabs.
25306 The rest of the entry, up to the trailing null byte, is the script to
25307 execute in the specified language. The name needs to be unique among
25308 all script names, as @value{GDBN} executes each script only once based
25311 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
25315 #include "symcat.h"
25316 #include "gdb/section-scripts.h"
25318 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
25319 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
25320 ".ascii \"gdb.inlined-script\\n\"\n"
25321 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
25322 ".ascii \" def __init__ (self):\\n\"\n"
25323 ".ascii \" super (test_cmd, self).__init__ ("
25324 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
25325 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
25326 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
25327 ".ascii \"test_cmd ()\\n\"\n"
25333 Loading of inlined scripts requires a properly configured
25334 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25335 The path to specify in @code{auto-load safe-path} is the path of the file
25336 containing the @code{.debug_gdb_scripts} section.
25338 @node Which flavor to choose?
25339 @subsection Which flavor to choose?
25341 Given the multiple ways of auto-loading extensions, it might not always
25342 be clear which one to choose. This section provides some guidance.
25345 Benefits of the @file{-gdb.@var{ext}} way:
25349 Can be used with file formats that don't support multiple sections.
25352 Ease of finding scripts for public libraries.
25354 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25355 in the source search path.
25356 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25357 isn't a source directory in which to find the script.
25360 Doesn't require source code additions.
25364 Benefits of the @code{.debug_gdb_scripts} way:
25368 Works with static linking.
25370 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
25371 trigger their loading. When an application is statically linked the only
25372 objfile available is the executable, and it is cumbersome to attach all the
25373 scripts from all the input libraries to the executable's
25374 @file{-gdb.@var{ext}} script.
25377 Works with classes that are entirely inlined.
25379 Some classes can be entirely inlined, and thus there may not be an associated
25380 shared library to attach a @file{-gdb.@var{ext}} script to.
25383 Scripts needn't be copied out of the source tree.
25385 In some circumstances, apps can be built out of large collections of internal
25386 libraries, and the build infrastructure necessary to install the
25387 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
25388 cumbersome. It may be easier to specify the scripts in the
25389 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25390 top of the source tree to the source search path.
25393 @node Multiple Extension Languages
25394 @section Multiple Extension Languages
25396 The Guile and Python extension languages do not share any state,
25397 and generally do not interfere with each other.
25398 There are some things to be aware of, however.
25400 @subsection Python comes first
25402 Python was @value{GDBN}'s first extension language, and to avoid breaking
25403 existing behaviour Python comes first. This is generally solved by the
25404 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
25405 extension languages, and when it makes a call to an extension language,
25406 (say to pretty-print a value), it tries each in turn until an extension
25407 language indicates it has performed the request (e.g., has returned the
25408 pretty-printed form of a value).
25409 This extends to errors while performing such requests: If an error happens
25410 while, for example, trying to pretty-print an object then the error is
25411 reported and any following extension languages are not tried.
25414 @section Creating new spellings of existing commands
25415 @cindex aliases for commands
25417 It is often useful to define alternate spellings of existing commands.
25418 For example, if a new @value{GDBN} command defined in Python has
25419 a long name to type, it is handy to have an abbreviated version of it
25420 that involves less typing.
25422 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
25423 of the @samp{step} command even though it is otherwise an ambiguous
25424 abbreviation of other commands like @samp{set} and @samp{show}.
25426 Aliases are also used to provide shortened or more common versions
25427 of multi-word commands. For example, @value{GDBN} provides the
25428 @samp{tty} alias of the @samp{set inferior-tty} command.
25430 You can define a new alias with the @samp{alias} command.
25435 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
25439 @var{ALIAS} specifies the name of the new alias.
25440 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
25443 @var{COMMAND} specifies the name of an existing command
25444 that is being aliased.
25446 The @samp{-a} option specifies that the new alias is an abbreviation
25447 of the command. Abbreviations are not shown in command
25448 lists displayed by the @samp{help} command.
25450 The @samp{--} option specifies the end of options,
25451 and is useful when @var{ALIAS} begins with a dash.
25453 Here is a simple example showing how to make an abbreviation
25454 of a command so that there is less to type.
25455 Suppose you were tired of typing @samp{disas}, the current
25456 shortest unambiguous abbreviation of the @samp{disassemble} command
25457 and you wanted an even shorter version named @samp{di}.
25458 The following will accomplish this.
25461 (gdb) alias -a di = disas
25464 Note that aliases are different from user-defined commands.
25465 With a user-defined command, you also need to write documentation
25466 for it with the @samp{document} command.
25467 An alias automatically picks up the documentation of the existing command.
25469 Here is an example where we make @samp{elms} an abbreviation of
25470 @samp{elements} in the @samp{set print elements} command.
25471 This is to show that you can make an abbreviation of any part
25475 (gdb) alias -a set print elms = set print elements
25476 (gdb) alias -a show print elms = show print elements
25477 (gdb) set p elms 20
25479 Limit on string chars or array elements to print is 200.
25482 Note that if you are defining an alias of a @samp{set} command,
25483 and you want to have an alias for the corresponding @samp{show}
25484 command, then you need to define the latter separately.
25486 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25487 @var{ALIAS}, just as they are normally.
25490 (gdb) alias -a set pr elms = set p ele
25493 Finally, here is an example showing the creation of a one word
25494 alias for a more complex command.
25495 This creates alias @samp{spe} of the command @samp{set print elements}.
25498 (gdb) alias spe = set print elements
25503 @chapter Command Interpreters
25504 @cindex command interpreters
25506 @value{GDBN} supports multiple command interpreters, and some command
25507 infrastructure to allow users or user interface writers to switch
25508 between interpreters or run commands in other interpreters.
25510 @value{GDBN} currently supports two command interpreters, the console
25511 interpreter (sometimes called the command-line interpreter or @sc{cli})
25512 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25513 describes both of these interfaces in great detail.
25515 By default, @value{GDBN} will start with the console interpreter.
25516 However, the user may choose to start @value{GDBN} with another
25517 interpreter by specifying the @option{-i} or @option{--interpreter}
25518 startup options. Defined interpreters include:
25522 @cindex console interpreter
25523 The traditional console or command-line interpreter. This is the most often
25524 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25525 @value{GDBN} will use this interpreter.
25528 @cindex mi interpreter
25529 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25530 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25531 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25535 @cindex mi2 interpreter
25536 The current @sc{gdb/mi} interface.
25539 @cindex mi1 interpreter
25540 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25544 @cindex invoke another interpreter
25546 @kindex interpreter-exec
25547 You may execute commands in any interpreter from the current
25548 interpreter using the appropriate command. If you are running the
25549 console interpreter, simply use the @code{interpreter-exec} command:
25552 interpreter-exec mi "-data-list-register-names"
25555 @sc{gdb/mi} has a similar command, although it is only available in versions of
25556 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25558 Note that @code{interpreter-exec} only changes the interpreter for the
25559 duration of the specified command. It does not change the interpreter
25562 @cindex start a new independent interpreter
25564 Although you may only choose a single interpreter at startup, it is
25565 possible to run an independent interpreter on a specified input/output
25566 device (usually a tty).
25568 For example, consider a debugger GUI or IDE that wants to provide a
25569 @value{GDBN} console view. It may do so by embedding a terminal
25570 emulator widget in its GUI, starting @value{GDBN} in the traditional
25571 command-line mode with stdin/stdout/stderr redirected to that
25572 terminal, and then creating an MI interpreter running on a specified
25573 input/output device. The console interpreter created by @value{GDBN}
25574 at startup handles commands the user types in the terminal widget,
25575 while the GUI controls and synchronizes state with @value{GDBN} using
25576 the separate MI interpreter.
25578 To start a new secondary @dfn{user interface} running MI, use the
25579 @code{new-ui} command:
25582 @cindex new user interface
25584 new-ui @var{interpreter} @var{tty}
25587 The @var{interpreter} parameter specifies the interpreter to run.
25588 This accepts the same values as the @code{interpreter-exec} command.
25589 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
25590 @var{tty} parameter specifies the name of the bidirectional file the
25591 interpreter uses for input/output, usually the name of a
25592 pseudoterminal slave on Unix systems. For example:
25595 (@value{GDBP}) new-ui mi /dev/pts/9
25599 runs an MI interpreter on @file{/dev/pts/9}.
25602 @chapter @value{GDBN} Text User Interface
25604 @cindex Text User Interface
25607 * TUI Overview:: TUI overview
25608 * TUI Keys:: TUI key bindings
25609 * TUI Single Key Mode:: TUI single key mode
25610 * TUI Commands:: TUI-specific commands
25611 * TUI Configuration:: TUI configuration variables
25614 The @value{GDBN} Text User Interface (TUI) is a terminal
25615 interface which uses the @code{curses} library to show the source
25616 file, the assembly output, the program registers and @value{GDBN}
25617 commands in separate text windows. The TUI mode is supported only
25618 on platforms where a suitable version of the @code{curses} library
25621 The TUI mode is enabled by default when you invoke @value{GDBN} as
25622 @samp{@value{GDBP} -tui}.
25623 You can also switch in and out of TUI mode while @value{GDBN} runs by
25624 using various TUI commands and key bindings, such as @command{tui
25625 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
25626 @ref{TUI Keys, ,TUI Key Bindings}.
25629 @section TUI Overview
25631 In TUI mode, @value{GDBN} can display several text windows:
25635 This window is the @value{GDBN} command window with the @value{GDBN}
25636 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25637 managed using readline.
25640 The source window shows the source file of the program. The current
25641 line and active breakpoints are displayed in this window.
25644 The assembly window shows the disassembly output of the program.
25647 This window shows the processor registers. Registers are highlighted
25648 when their values change.
25651 The source and assembly windows show the current program position
25652 by highlighting the current line and marking it with a @samp{>} marker.
25653 Breakpoints are indicated with two markers. The first marker
25654 indicates the breakpoint type:
25658 Breakpoint which was hit at least once.
25661 Breakpoint which was never hit.
25664 Hardware breakpoint which was hit at least once.
25667 Hardware breakpoint which was never hit.
25670 The second marker indicates whether the breakpoint is enabled or not:
25674 Breakpoint is enabled.
25677 Breakpoint is disabled.
25680 The source, assembly and register windows are updated when the current
25681 thread changes, when the frame changes, or when the program counter
25684 These windows are not all visible at the same time. The command
25685 window is always visible. The others can be arranged in several
25696 source and assembly,
25699 source and registers, or
25702 assembly and registers.
25705 A status line above the command window shows the following information:
25709 Indicates the current @value{GDBN} target.
25710 (@pxref{Targets, ,Specifying a Debugging Target}).
25713 Gives the current process or thread number.
25714 When no process is being debugged, this field is set to @code{No process}.
25717 Gives the current function name for the selected frame.
25718 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25719 When there is no symbol corresponding to the current program counter,
25720 the string @code{??} is displayed.
25723 Indicates the current line number for the selected frame.
25724 When the current line number is not known, the string @code{??} is displayed.
25727 Indicates the current program counter address.
25731 @section TUI Key Bindings
25732 @cindex TUI key bindings
25734 The TUI installs several key bindings in the readline keymaps
25735 @ifset SYSTEM_READLINE
25736 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25738 @ifclear SYSTEM_READLINE
25739 (@pxref{Command Line Editing}).
25741 The following key bindings are installed for both TUI mode and the
25742 @value{GDBN} standard mode.
25751 Enter or leave the TUI mode. When leaving the TUI mode,
25752 the curses window management stops and @value{GDBN} operates using
25753 its standard mode, writing on the terminal directly. When reentering
25754 the TUI mode, control is given back to the curses windows.
25755 The screen is then refreshed.
25759 Use a TUI layout with only one window. The layout will
25760 either be @samp{source} or @samp{assembly}. When the TUI mode
25761 is not active, it will switch to the TUI mode.
25763 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25767 Use a TUI layout with at least two windows. When the current
25768 layout already has two windows, the next layout with two windows is used.
25769 When a new layout is chosen, one window will always be common to the
25770 previous layout and the new one.
25772 Think of it as the Emacs @kbd{C-x 2} binding.
25776 Change the active window. The TUI associates several key bindings
25777 (like scrolling and arrow keys) with the active window. This command
25778 gives the focus to the next TUI window.
25780 Think of it as the Emacs @kbd{C-x o} binding.
25784 Switch in and out of the TUI SingleKey mode that binds single
25785 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25788 The following key bindings only work in the TUI mode:
25793 Scroll the active window one page up.
25797 Scroll the active window one page down.
25801 Scroll the active window one line up.
25805 Scroll the active window one line down.
25809 Scroll the active window one column left.
25813 Scroll the active window one column right.
25817 Refresh the screen.
25820 Because the arrow keys scroll the active window in the TUI mode, they
25821 are not available for their normal use by readline unless the command
25822 window has the focus. When another window is active, you must use
25823 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25824 and @kbd{C-f} to control the command window.
25826 @node TUI Single Key Mode
25827 @section TUI Single Key Mode
25828 @cindex TUI single key mode
25830 The TUI also provides a @dfn{SingleKey} mode, which binds several
25831 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25832 switch into this mode, where the following key bindings are used:
25835 @kindex c @r{(SingleKey TUI key)}
25839 @kindex d @r{(SingleKey TUI key)}
25843 @kindex f @r{(SingleKey TUI key)}
25847 @kindex n @r{(SingleKey TUI key)}
25851 @kindex o @r{(SingleKey TUI key)}
25853 nexti. The shortcut letter @samp{o} stands for ``step Over''.
25855 @kindex q @r{(SingleKey TUI key)}
25857 exit the SingleKey mode.
25859 @kindex r @r{(SingleKey TUI key)}
25863 @kindex s @r{(SingleKey TUI key)}
25867 @kindex i @r{(SingleKey TUI key)}
25869 stepi. The shortcut letter @samp{i} stands for ``step Into''.
25871 @kindex u @r{(SingleKey TUI key)}
25875 @kindex v @r{(SingleKey TUI key)}
25879 @kindex w @r{(SingleKey TUI key)}
25884 Other keys temporarily switch to the @value{GDBN} command prompt.
25885 The key that was pressed is inserted in the editing buffer so that
25886 it is possible to type most @value{GDBN} commands without interaction
25887 with the TUI SingleKey mode. Once the command is entered the TUI
25888 SingleKey mode is restored. The only way to permanently leave
25889 this mode is by typing @kbd{q} or @kbd{C-x s}.
25893 @section TUI-specific Commands
25894 @cindex TUI commands
25896 The TUI has specific commands to control the text windows.
25897 These commands are always available, even when @value{GDBN} is not in
25898 the TUI mode. When @value{GDBN} is in the standard mode, most
25899 of these commands will automatically switch to the TUI mode.
25901 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25902 terminal, or @value{GDBN} has been started with the machine interface
25903 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25904 these commands will fail with an error, because it would not be
25905 possible or desirable to enable curses window management.
25910 Activate TUI mode. The last active TUI window layout will be used if
25911 TUI mode has prevsiouly been used in the current debugging session,
25912 otherwise a default layout is used.
25915 @kindex tui disable
25916 Disable TUI mode, returning to the console interpreter.
25920 List and give the size of all displayed windows.
25922 @item layout @var{name}
25924 Changes which TUI windows are displayed. In each layout the command
25925 window is always displayed, the @var{name} parameter controls which
25926 additional windows are displayed, and can be any of the following:
25930 Display the next layout.
25933 Display the previous layout.
25936 Display the source and command windows.
25939 Display the assembly and command windows.
25942 Display the source, assembly, and command windows.
25945 When in @code{src} layout display the register, source, and command
25946 windows. When in @code{asm} or @code{split} layout display the
25947 register, assembler, and command windows.
25950 @item focus @var{name}
25952 Changes which TUI window is currently active for scrolling. The
25953 @var{name} parameter can be any of the following:
25957 Make the next window active for scrolling.
25960 Make the previous window active for scrolling.
25963 Make the source window active for scrolling.
25966 Make the assembly window active for scrolling.
25969 Make the register window active for scrolling.
25972 Make the command window active for scrolling.
25977 Refresh the screen. This is similar to typing @kbd{C-L}.
25979 @item tui reg @var{group}
25981 Changes the register group displayed in the tui register window to
25982 @var{group}. If the register window is not currently displayed this
25983 command will cause the register window to be displayed. The list of
25984 register groups, as well as their order is target specific. The
25985 following groups are available on most targets:
25988 Repeatedly selecting this group will cause the display to cycle
25989 through all of the available register groups.
25992 Repeatedly selecting this group will cause the display to cycle
25993 through all of the available register groups in the reverse order to
25997 Display the general registers.
25999 Display the floating point registers.
26001 Display the system registers.
26003 Display the vector registers.
26005 Display all registers.
26010 Update the source window and the current execution point.
26012 @item winheight @var{name} +@var{count}
26013 @itemx winheight @var{name} -@var{count}
26015 Change the height of the window @var{name} by @var{count}
26016 lines. Positive counts increase the height, while negative counts
26017 decrease it. The @var{name} parameter can be one of @code{src} (the
26018 source window), @code{cmd} (the command window), @code{asm} (the
26019 disassembly window), or @code{regs} (the register display window).
26021 @item tabset @var{nchars}
26023 Set the width of tab stops to be @var{nchars} characters. This
26024 setting affects the display of TAB characters in the source and
26028 @node TUI Configuration
26029 @section TUI Configuration Variables
26030 @cindex TUI configuration variables
26032 Several configuration variables control the appearance of TUI windows.
26035 @item set tui border-kind @var{kind}
26036 @kindex set tui border-kind
26037 Select the border appearance for the source, assembly and register windows.
26038 The possible values are the following:
26041 Use a space character to draw the border.
26044 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26047 Use the Alternate Character Set to draw the border. The border is
26048 drawn using character line graphics if the terminal supports them.
26051 @item set tui border-mode @var{mode}
26052 @kindex set tui border-mode
26053 @itemx set tui active-border-mode @var{mode}
26054 @kindex set tui active-border-mode
26055 Select the display attributes for the borders of the inactive windows
26056 or the active window. The @var{mode} can be one of the following:
26059 Use normal attributes to display the border.
26065 Use reverse video mode.
26068 Use half bright mode.
26070 @item half-standout
26071 Use half bright and standout mode.
26074 Use extra bright or bold mode.
26076 @item bold-standout
26077 Use extra bright or bold and standout mode.
26082 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26085 @cindex @sc{gnu} Emacs
26086 A special interface allows you to use @sc{gnu} Emacs to view (and
26087 edit) the source files for the program you are debugging with
26090 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26091 executable file you want to debug as an argument. This command starts
26092 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26093 created Emacs buffer.
26094 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26096 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
26101 All ``terminal'' input and output goes through an Emacs buffer, called
26104 This applies both to @value{GDBN} commands and their output, and to the input
26105 and output done by the program you are debugging.
26107 This is useful because it means that you can copy the text of previous
26108 commands and input them again; you can even use parts of the output
26111 All the facilities of Emacs' Shell mode are available for interacting
26112 with your program. In particular, you can send signals the usual
26113 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
26117 @value{GDBN} displays source code through Emacs.
26119 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
26120 source file for that frame and puts an arrow (@samp{=>}) at the
26121 left margin of the current line. Emacs uses a separate buffer for
26122 source display, and splits the screen to show both your @value{GDBN} session
26125 Explicit @value{GDBN} @code{list} or search commands still produce output as
26126 usual, but you probably have no reason to use them from Emacs.
26129 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
26130 a graphical mode, enabled by default, which provides further buffers
26131 that can control the execution and describe the state of your program.
26132 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
26134 If you specify an absolute file name when prompted for the @kbd{M-x
26135 gdb} argument, then Emacs sets your current working directory to where
26136 your program resides. If you only specify the file name, then Emacs
26137 sets your current working directory to the directory associated
26138 with the previous buffer. In this case, @value{GDBN} may find your
26139 program by searching your environment's @code{PATH} variable, but on
26140 some operating systems it might not find the source. So, although the
26141 @value{GDBN} input and output session proceeds normally, the auxiliary
26142 buffer does not display the current source and line of execution.
26144 The initial working directory of @value{GDBN} is printed on the top
26145 line of the GUD buffer and this serves as a default for the commands
26146 that specify files for @value{GDBN} to operate on. @xref{Files,
26147 ,Commands to Specify Files}.
26149 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
26150 need to call @value{GDBN} by a different name (for example, if you
26151 keep several configurations around, with different names) you can
26152 customize the Emacs variable @code{gud-gdb-command-name} to run the
26155 In the GUD buffer, you can use these special Emacs commands in
26156 addition to the standard Shell mode commands:
26160 Describe the features of Emacs' GUD Mode.
26163 Execute to another source line, like the @value{GDBN} @code{step} command; also
26164 update the display window to show the current file and location.
26167 Execute to next source line in this function, skipping all function
26168 calls, like the @value{GDBN} @code{next} command. Then update the display window
26169 to show the current file and location.
26172 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
26173 display window accordingly.
26176 Execute until exit from the selected stack frame, like the @value{GDBN}
26177 @code{finish} command.
26180 Continue execution of your program, like the @value{GDBN} @code{continue}
26184 Go up the number of frames indicated by the numeric argument
26185 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
26186 like the @value{GDBN} @code{up} command.
26189 Go down the number of frames indicated by the numeric argument, like the
26190 @value{GDBN} @code{down} command.
26193 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
26194 tells @value{GDBN} to set a breakpoint on the source line point is on.
26196 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
26197 separate frame which shows a backtrace when the GUD buffer is current.
26198 Move point to any frame in the stack and type @key{RET} to make it
26199 become the current frame and display the associated source in the
26200 source buffer. Alternatively, click @kbd{Mouse-2} to make the
26201 selected frame become the current one. In graphical mode, the
26202 speedbar displays watch expressions.
26204 If you accidentally delete the source-display buffer, an easy way to get
26205 it back is to type the command @code{f} in the @value{GDBN} buffer, to
26206 request a frame display; when you run under Emacs, this recreates
26207 the source buffer if necessary to show you the context of the current
26210 The source files displayed in Emacs are in ordinary Emacs buffers
26211 which are visiting the source files in the usual way. You can edit
26212 the files with these buffers if you wish; but keep in mind that @value{GDBN}
26213 communicates with Emacs in terms of line numbers. If you add or
26214 delete lines from the text, the line numbers that @value{GDBN} knows cease
26215 to correspond properly with the code.
26217 A more detailed description of Emacs' interaction with @value{GDBN} is
26218 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
26222 @chapter The @sc{gdb/mi} Interface
26224 @unnumberedsec Function and Purpose
26226 @cindex @sc{gdb/mi}, its purpose
26227 @sc{gdb/mi} is a line based machine oriented text interface to
26228 @value{GDBN} and is activated by specifying using the
26229 @option{--interpreter} command line option (@pxref{Mode Options}). It
26230 is specifically intended to support the development of systems which
26231 use the debugger as just one small component of a larger system.
26233 This chapter is a specification of the @sc{gdb/mi} interface. It is written
26234 in the form of a reference manual.
26236 Note that @sc{gdb/mi} is still under construction, so some of the
26237 features described below are incomplete and subject to change
26238 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
26240 @unnumberedsec Notation and Terminology
26242 @cindex notational conventions, for @sc{gdb/mi}
26243 This chapter uses the following notation:
26247 @code{|} separates two alternatives.
26250 @code{[ @var{something} ]} indicates that @var{something} is optional:
26251 it may or may not be given.
26254 @code{( @var{group} )*} means that @var{group} inside the parentheses
26255 may repeat zero or more times.
26258 @code{( @var{group} )+} means that @var{group} inside the parentheses
26259 may repeat one or more times.
26262 @code{"@var{string}"} means a literal @var{string}.
26266 @heading Dependencies
26270 * GDB/MI General Design::
26271 * GDB/MI Command Syntax::
26272 * GDB/MI Compatibility with CLI::
26273 * GDB/MI Development and Front Ends::
26274 * GDB/MI Output Records::
26275 * GDB/MI Simple Examples::
26276 * GDB/MI Command Description Format::
26277 * GDB/MI Breakpoint Commands::
26278 * GDB/MI Catchpoint Commands::
26279 * GDB/MI Program Context::
26280 * GDB/MI Thread Commands::
26281 * GDB/MI Ada Tasking Commands::
26282 * GDB/MI Program Execution::
26283 * GDB/MI Stack Manipulation::
26284 * GDB/MI Variable Objects::
26285 * GDB/MI Data Manipulation::
26286 * GDB/MI Tracepoint Commands::
26287 * GDB/MI Symbol Query::
26288 * GDB/MI File Commands::
26290 * GDB/MI Kod Commands::
26291 * GDB/MI Memory Overlay Commands::
26292 * GDB/MI Signal Handling Commands::
26294 * GDB/MI Target Manipulation::
26295 * GDB/MI File Transfer Commands::
26296 * GDB/MI Ada Exceptions Commands::
26297 * GDB/MI Support Commands::
26298 * GDB/MI Miscellaneous Commands::
26301 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26302 @node GDB/MI General Design
26303 @section @sc{gdb/mi} General Design
26304 @cindex GDB/MI General Design
26306 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26307 parts---commands sent to @value{GDBN}, responses to those commands
26308 and notifications. Each command results in exactly one response,
26309 indicating either successful completion of the command, or an error.
26310 For the commands that do not resume the target, the response contains the
26311 requested information. For the commands that resume the target, the
26312 response only indicates whether the target was successfully resumed.
26313 Notifications is the mechanism for reporting changes in the state of the
26314 target, or in @value{GDBN} state, that cannot conveniently be associated with
26315 a command and reported as part of that command response.
26317 The important examples of notifications are:
26321 Exec notifications. These are used to report changes in
26322 target state---when a target is resumed, or stopped. It would not
26323 be feasible to include this information in response of resuming
26324 commands, because one resume commands can result in multiple events in
26325 different threads. Also, quite some time may pass before any event
26326 happens in the target, while a frontend needs to know whether the resuming
26327 command itself was successfully executed.
26330 Console output, and status notifications. Console output
26331 notifications are used to report output of CLI commands, as well as
26332 diagnostics for other commands. Status notifications are used to
26333 report the progress of a long-running operation. Naturally, including
26334 this information in command response would mean no output is produced
26335 until the command is finished, which is undesirable.
26338 General notifications. Commands may have various side effects on
26339 the @value{GDBN} or target state beyond their official purpose. For example,
26340 a command may change the selected thread. Although such changes can
26341 be included in command response, using notification allows for more
26342 orthogonal frontend design.
26346 There's no guarantee that whenever an MI command reports an error,
26347 @value{GDBN} or the target are in any specific state, and especially,
26348 the state is not reverted to the state before the MI command was
26349 processed. Therefore, whenever an MI command results in an error,
26350 we recommend that the frontend refreshes all the information shown in
26351 the user interface.
26355 * Context management::
26356 * Asynchronous and non-stop modes::
26360 @node Context management
26361 @subsection Context management
26363 @subsubsection Threads and Frames
26365 In most cases when @value{GDBN} accesses the target, this access is
26366 done in context of a specific thread and frame (@pxref{Frames}).
26367 Often, even when accessing global data, the target requires that a thread
26368 be specified. The CLI interface maintains the selected thread and frame,
26369 and supplies them to target on each command. This is convenient,
26370 because a command line user would not want to specify that information
26371 explicitly on each command, and because user interacts with
26372 @value{GDBN} via a single terminal, so no confusion is possible as
26373 to what thread and frame are the current ones.
26375 In the case of MI, the concept of selected thread and frame is less
26376 useful. First, a frontend can easily remember this information
26377 itself. Second, a graphical frontend can have more than one window,
26378 each one used for debugging a different thread, and the frontend might
26379 want to access additional threads for internal purposes. This
26380 increases the risk that by relying on implicitly selected thread, the
26381 frontend may be operating on a wrong one. Therefore, each MI command
26382 should explicitly specify which thread and frame to operate on. To
26383 make it possible, each MI command accepts the @samp{--thread} and
26384 @samp{--frame} options, the value to each is @value{GDBN} global
26385 identifier for thread and frame to operate on.
26387 Usually, each top-level window in a frontend allows the user to select
26388 a thread and a frame, and remembers the user selection for further
26389 operations. However, in some cases @value{GDBN} may suggest that the
26390 current thread or frame be changed. For example, when stopping on a
26391 breakpoint it is reasonable to switch to the thread where breakpoint is
26392 hit. For another example, if the user issues the CLI @samp{thread} or
26393 @samp{frame} commands via the frontend, it is desirable to change the
26394 frontend's selection to the one specified by user. @value{GDBN}
26395 communicates the suggestion to change current thread and frame using the
26396 @samp{=thread-selected} notification.
26398 Note that historically, MI shares the selected thread with CLI, so
26399 frontends used the @code{-thread-select} to execute commands in the
26400 right context. However, getting this to work right is cumbersome. The
26401 simplest way is for frontend to emit @code{-thread-select} command
26402 before every command. This doubles the number of commands that need
26403 to be sent. The alternative approach is to suppress @code{-thread-select}
26404 if the selected thread in @value{GDBN} is supposed to be identical to the
26405 thread the frontend wants to operate on. However, getting this
26406 optimization right can be tricky. In particular, if the frontend
26407 sends several commands to @value{GDBN}, and one of the commands changes the
26408 selected thread, then the behaviour of subsequent commands will
26409 change. So, a frontend should either wait for response from such
26410 problematic commands, or explicitly add @code{-thread-select} for
26411 all subsequent commands. No frontend is known to do this exactly
26412 right, so it is suggested to just always pass the @samp{--thread} and
26413 @samp{--frame} options.
26415 @subsubsection Language
26417 The execution of several commands depends on which language is selected.
26418 By default, the current language (@pxref{show language}) is used.
26419 But for commands known to be language-sensitive, it is recommended
26420 to use the @samp{--language} option. This option takes one argument,
26421 which is the name of the language to use while executing the command.
26425 -data-evaluate-expression --language c "sizeof (void*)"
26430 The valid language names are the same names accepted by the
26431 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
26432 @samp{local} or @samp{unknown}.
26434 @node Asynchronous and non-stop modes
26435 @subsection Asynchronous command execution and non-stop mode
26437 On some targets, @value{GDBN} is capable of processing MI commands
26438 even while the target is running. This is called @dfn{asynchronous
26439 command execution} (@pxref{Background Execution}). The frontend may
26440 specify a preferrence for asynchronous execution using the
26441 @code{-gdb-set mi-async 1} command, which should be emitted before
26442 either running the executable or attaching to the target. After the
26443 frontend has started the executable or attached to the target, it can
26444 find if asynchronous execution is enabled using the
26445 @code{-list-target-features} command.
26448 @item -gdb-set mi-async on
26449 @item -gdb-set mi-async off
26450 Set whether MI is in asynchronous mode.
26452 When @code{off}, which is the default, MI execution commands (e.g.,
26453 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
26454 for the program to stop before processing further commands.
26456 When @code{on}, MI execution commands are background execution
26457 commands (e.g., @code{-exec-continue} becomes the equivalent of the
26458 @code{c&} CLI command), and so @value{GDBN} is capable of processing
26459 MI commands even while the target is running.
26461 @item -gdb-show mi-async
26462 Show whether MI asynchronous mode is enabled.
26465 Note: In @value{GDBN} version 7.7 and earlier, this option was called
26466 @code{target-async} instead of @code{mi-async}, and it had the effect
26467 of both putting MI in asynchronous mode and making CLI background
26468 commands possible. CLI background commands are now always possible
26469 ``out of the box'' if the target supports them. The old spelling is
26470 kept as a deprecated alias for backwards compatibility.
26472 Even if @value{GDBN} can accept a command while target is running,
26473 many commands that access the target do not work when the target is
26474 running. Therefore, asynchronous command execution is most useful
26475 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
26476 it is possible to examine the state of one thread, while other threads
26479 When a given thread is running, MI commands that try to access the
26480 target in the context of that thread may not work, or may work only on
26481 some targets. In particular, commands that try to operate on thread's
26482 stack will not work, on any target. Commands that read memory, or
26483 modify breakpoints, may work or not work, depending on the target. Note
26484 that even commands that operate on global state, such as @code{print},
26485 @code{set}, and breakpoint commands, still access the target in the
26486 context of a specific thread, so frontend should try to find a
26487 stopped thread and perform the operation on that thread (using the
26488 @samp{--thread} option).
26490 Which commands will work in the context of a running thread is
26491 highly target dependent. However, the two commands
26492 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
26493 to find the state of a thread, will always work.
26495 @node Thread groups
26496 @subsection Thread groups
26497 @value{GDBN} may be used to debug several processes at the same time.
26498 On some platfroms, @value{GDBN} may support debugging of several
26499 hardware systems, each one having several cores with several different
26500 processes running on each core. This section describes the MI
26501 mechanism to support such debugging scenarios.
26503 The key observation is that regardless of the structure of the
26504 target, MI can have a global list of threads, because most commands that
26505 accept the @samp{--thread} option do not need to know what process that
26506 thread belongs to. Therefore, it is not necessary to introduce
26507 neither additional @samp{--process} option, nor an notion of the
26508 current process in the MI interface. The only strictly new feature
26509 that is required is the ability to find how the threads are grouped
26512 To allow the user to discover such grouping, and to support arbitrary
26513 hierarchy of machines/cores/processes, MI introduces the concept of a
26514 @dfn{thread group}. Thread group is a collection of threads and other
26515 thread groups. A thread group always has a string identifier, a type,
26516 and may have additional attributes specific to the type. A new
26517 command, @code{-list-thread-groups}, returns the list of top-level
26518 thread groups, which correspond to processes that @value{GDBN} is
26519 debugging at the moment. By passing an identifier of a thread group
26520 to the @code{-list-thread-groups} command, it is possible to obtain
26521 the members of specific thread group.
26523 To allow the user to easily discover processes, and other objects, he
26524 wishes to debug, a concept of @dfn{available thread group} is
26525 introduced. Available thread group is an thread group that
26526 @value{GDBN} is not debugging, but that can be attached to, using the
26527 @code{-target-attach} command. The list of available top-level thread
26528 groups can be obtained using @samp{-list-thread-groups --available}.
26529 In general, the content of a thread group may be only retrieved only
26530 after attaching to that thread group.
26532 Thread groups are related to inferiors (@pxref{Inferiors and
26533 Programs}). Each inferior corresponds to a thread group of a special
26534 type @samp{process}, and some additional operations are permitted on
26535 such thread groups.
26537 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26538 @node GDB/MI Command Syntax
26539 @section @sc{gdb/mi} Command Syntax
26542 * GDB/MI Input Syntax::
26543 * GDB/MI Output Syntax::
26546 @node GDB/MI Input Syntax
26547 @subsection @sc{gdb/mi} Input Syntax
26549 @cindex input syntax for @sc{gdb/mi}
26550 @cindex @sc{gdb/mi}, input syntax
26552 @item @var{command} @expansion{}
26553 @code{@var{cli-command} | @var{mi-command}}
26555 @item @var{cli-command} @expansion{}
26556 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26557 @var{cli-command} is any existing @value{GDBN} CLI command.
26559 @item @var{mi-command} @expansion{}
26560 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26561 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26563 @item @var{token} @expansion{}
26564 "any sequence of digits"
26566 @item @var{option} @expansion{}
26567 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26569 @item @var{parameter} @expansion{}
26570 @code{@var{non-blank-sequence} | @var{c-string}}
26572 @item @var{operation} @expansion{}
26573 @emph{any of the operations described in this chapter}
26575 @item @var{non-blank-sequence} @expansion{}
26576 @emph{anything, provided it doesn't contain special characters such as
26577 "-", @var{nl}, """ and of course " "}
26579 @item @var{c-string} @expansion{}
26580 @code{""" @var{seven-bit-iso-c-string-content} """}
26582 @item @var{nl} @expansion{}
26591 The CLI commands are still handled by the @sc{mi} interpreter; their
26592 output is described below.
26595 The @code{@var{token}}, when present, is passed back when the command
26599 Some @sc{mi} commands accept optional arguments as part of the parameter
26600 list. Each option is identified by a leading @samp{-} (dash) and may be
26601 followed by an optional argument parameter. Options occur first in the
26602 parameter list and can be delimited from normal parameters using
26603 @samp{--} (this is useful when some parameters begin with a dash).
26610 We want easy access to the existing CLI syntax (for debugging).
26613 We want it to be easy to spot a @sc{mi} operation.
26616 @node GDB/MI Output Syntax
26617 @subsection @sc{gdb/mi} Output Syntax
26619 @cindex output syntax of @sc{gdb/mi}
26620 @cindex @sc{gdb/mi}, output syntax
26621 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26622 followed, optionally, by a single result record. This result record
26623 is for the most recent command. The sequence of output records is
26624 terminated by @samp{(gdb)}.
26626 If an input command was prefixed with a @code{@var{token}} then the
26627 corresponding output for that command will also be prefixed by that same
26631 @item @var{output} @expansion{}
26632 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26634 @item @var{result-record} @expansion{}
26635 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26637 @item @var{out-of-band-record} @expansion{}
26638 @code{@var{async-record} | @var{stream-record}}
26640 @item @var{async-record} @expansion{}
26641 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26643 @item @var{exec-async-output} @expansion{}
26644 @code{[ @var{token} ] "*" @var{async-output nl}}
26646 @item @var{status-async-output} @expansion{}
26647 @code{[ @var{token} ] "+" @var{async-output nl}}
26649 @item @var{notify-async-output} @expansion{}
26650 @code{[ @var{token} ] "=" @var{async-output nl}}
26652 @item @var{async-output} @expansion{}
26653 @code{@var{async-class} ( "," @var{result} )*}
26655 @item @var{result-class} @expansion{}
26656 @code{"done" | "running" | "connected" | "error" | "exit"}
26658 @item @var{async-class} @expansion{}
26659 @code{"stopped" | @var{others}} (where @var{others} will be added
26660 depending on the needs---this is still in development).
26662 @item @var{result} @expansion{}
26663 @code{ @var{variable} "=" @var{value}}
26665 @item @var{variable} @expansion{}
26666 @code{ @var{string} }
26668 @item @var{value} @expansion{}
26669 @code{ @var{const} | @var{tuple} | @var{list} }
26671 @item @var{const} @expansion{}
26672 @code{@var{c-string}}
26674 @item @var{tuple} @expansion{}
26675 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26677 @item @var{list} @expansion{}
26678 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26679 @var{result} ( "," @var{result} )* "]" }
26681 @item @var{stream-record} @expansion{}
26682 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26684 @item @var{console-stream-output} @expansion{}
26685 @code{"~" @var{c-string nl}}
26687 @item @var{target-stream-output} @expansion{}
26688 @code{"@@" @var{c-string nl}}
26690 @item @var{log-stream-output} @expansion{}
26691 @code{"&" @var{c-string nl}}
26693 @item @var{nl} @expansion{}
26696 @item @var{token} @expansion{}
26697 @emph{any sequence of digits}.
26705 All output sequences end in a single line containing a period.
26708 The @code{@var{token}} is from the corresponding request. Note that
26709 for all async output, while the token is allowed by the grammar and
26710 may be output by future versions of @value{GDBN} for select async
26711 output messages, it is generally omitted. Frontends should treat
26712 all async output as reporting general changes in the state of the
26713 target and there should be no need to associate async output to any
26717 @cindex status output in @sc{gdb/mi}
26718 @var{status-async-output} contains on-going status information about the
26719 progress of a slow operation. It can be discarded. All status output is
26720 prefixed by @samp{+}.
26723 @cindex async output in @sc{gdb/mi}
26724 @var{exec-async-output} contains asynchronous state change on the target
26725 (stopped, started, disappeared). All async output is prefixed by
26729 @cindex notify output in @sc{gdb/mi}
26730 @var{notify-async-output} contains supplementary information that the
26731 client should handle (e.g., a new breakpoint information). All notify
26732 output is prefixed by @samp{=}.
26735 @cindex console output in @sc{gdb/mi}
26736 @var{console-stream-output} is output that should be displayed as is in the
26737 console. It is the textual response to a CLI command. All the console
26738 output is prefixed by @samp{~}.
26741 @cindex target output in @sc{gdb/mi}
26742 @var{target-stream-output} is the output produced by the target program.
26743 All the target output is prefixed by @samp{@@}.
26746 @cindex log output in @sc{gdb/mi}
26747 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26748 instance messages that should be displayed as part of an error log. All
26749 the log output is prefixed by @samp{&}.
26752 @cindex list output in @sc{gdb/mi}
26753 New @sc{gdb/mi} commands should only output @var{lists} containing
26759 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26760 details about the various output records.
26762 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26763 @node GDB/MI Compatibility with CLI
26764 @section @sc{gdb/mi} Compatibility with CLI
26766 @cindex compatibility, @sc{gdb/mi} and CLI
26767 @cindex @sc{gdb/mi}, compatibility with CLI
26769 For the developers convenience CLI commands can be entered directly,
26770 but there may be some unexpected behaviour. For example, commands
26771 that query the user will behave as if the user replied yes, breakpoint
26772 command lists are not executed and some CLI commands, such as
26773 @code{if}, @code{when} and @code{define}, prompt for further input with
26774 @samp{>}, which is not valid MI output.
26776 This feature may be removed at some stage in the future and it is
26777 recommended that front ends use the @code{-interpreter-exec} command
26778 (@pxref{-interpreter-exec}).
26780 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26781 @node GDB/MI Development and Front Ends
26782 @section @sc{gdb/mi} Development and Front Ends
26783 @cindex @sc{gdb/mi} development
26785 The application which takes the MI output and presents the state of the
26786 program being debugged to the user is called a @dfn{front end}.
26788 Although @sc{gdb/mi} is still incomplete, it is currently being used
26789 by a variety of front ends to @value{GDBN}. This makes it difficult
26790 to introduce new functionality without breaking existing usage. This
26791 section tries to minimize the problems by describing how the protocol
26794 Some changes in MI need not break a carefully designed front end, and
26795 for these the MI version will remain unchanged. The following is a
26796 list of changes that may occur within one level, so front ends should
26797 parse MI output in a way that can handle them:
26801 New MI commands may be added.
26804 New fields may be added to the output of any MI command.
26807 The range of values for fields with specified values, e.g.,
26808 @code{in_scope} (@pxref{-var-update}) may be extended.
26810 @c The format of field's content e.g type prefix, may change so parse it
26811 @c at your own risk. Yes, in general?
26813 @c The order of fields may change? Shouldn't really matter but it might
26814 @c resolve inconsistencies.
26817 If the changes are likely to break front ends, the MI version level
26818 will be increased by one. This will allow the front end to parse the
26819 output according to the MI version. Apart from mi0, new versions of
26820 @value{GDBN} will not support old versions of MI and it will be the
26821 responsibility of the front end to work with the new one.
26823 @c Starting with mi3, add a new command -mi-version that prints the MI
26826 The best way to avoid unexpected changes in MI that might break your front
26827 end is to make your project known to @value{GDBN} developers and
26828 follow development on @email{gdb@@sourceware.org} and
26829 @email{gdb-patches@@sourceware.org}.
26830 @cindex mailing lists
26832 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26833 @node GDB/MI Output Records
26834 @section @sc{gdb/mi} Output Records
26837 * GDB/MI Result Records::
26838 * GDB/MI Stream Records::
26839 * GDB/MI Async Records::
26840 * GDB/MI Breakpoint Information::
26841 * GDB/MI Frame Information::
26842 * GDB/MI Thread Information::
26843 * GDB/MI Ada Exception Information::
26846 @node GDB/MI Result Records
26847 @subsection @sc{gdb/mi} Result Records
26849 @cindex result records in @sc{gdb/mi}
26850 @cindex @sc{gdb/mi}, result records
26851 In addition to a number of out-of-band notifications, the response to a
26852 @sc{gdb/mi} command includes one of the following result indications:
26856 @item "^done" [ "," @var{results} ]
26857 The synchronous operation was successful, @code{@var{results}} are the return
26862 This result record is equivalent to @samp{^done}. Historically, it
26863 was output instead of @samp{^done} if the command has resumed the
26864 target. This behaviour is maintained for backward compatibility, but
26865 all frontends should treat @samp{^done} and @samp{^running}
26866 identically and rely on the @samp{*running} output record to determine
26867 which threads are resumed.
26871 @value{GDBN} has connected to a remote target.
26873 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
26875 The operation failed. The @code{msg=@var{c-string}} variable contains
26876 the corresponding error message.
26878 If present, the @code{code=@var{c-string}} variable provides an error
26879 code on which consumers can rely on to detect the corresponding
26880 error condition. At present, only one error code is defined:
26883 @item "undefined-command"
26884 Indicates that the command causing the error does not exist.
26889 @value{GDBN} has terminated.
26893 @node GDB/MI Stream Records
26894 @subsection @sc{gdb/mi} Stream Records
26896 @cindex @sc{gdb/mi}, stream records
26897 @cindex stream records in @sc{gdb/mi}
26898 @value{GDBN} internally maintains a number of output streams: the console, the
26899 target, and the log. The output intended for each of these streams is
26900 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26902 Each stream record begins with a unique @dfn{prefix character} which
26903 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26904 Syntax}). In addition to the prefix, each stream record contains a
26905 @code{@var{string-output}}. This is either raw text (with an implicit new
26906 line) or a quoted C string (which does not contain an implicit newline).
26909 @item "~" @var{string-output}
26910 The console output stream contains text that should be displayed in the
26911 CLI console window. It contains the textual responses to CLI commands.
26913 @item "@@" @var{string-output}
26914 The target output stream contains any textual output from the running
26915 target. This is only present when GDB's event loop is truly
26916 asynchronous, which is currently only the case for remote targets.
26918 @item "&" @var{string-output}
26919 The log stream contains debugging messages being produced by @value{GDBN}'s
26923 @node GDB/MI Async Records
26924 @subsection @sc{gdb/mi} Async Records
26926 @cindex async records in @sc{gdb/mi}
26927 @cindex @sc{gdb/mi}, async records
26928 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26929 additional changes that have occurred. Those changes can either be a
26930 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26931 target activity (e.g., target stopped).
26933 The following is the list of possible async records:
26937 @item *running,thread-id="@var{thread}"
26938 The target is now running. The @var{thread} field can be the global
26939 thread ID of the the thread that is now running, and it can be
26940 @samp{all} if all threads are running. The frontend should assume
26941 that no interaction with a running thread is possible after this
26942 notification is produced. The frontend should not assume that this
26943 notification is output only once for any command. @value{GDBN} may
26944 emit this notification several times, either for different threads,
26945 because it cannot resume all threads together, or even for a single
26946 thread, if the thread must be stepped though some code before letting
26949 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26950 The target has stopped. The @var{reason} field can have one of the
26954 @item breakpoint-hit
26955 A breakpoint was reached.
26956 @item watchpoint-trigger
26957 A watchpoint was triggered.
26958 @item read-watchpoint-trigger
26959 A read watchpoint was triggered.
26960 @item access-watchpoint-trigger
26961 An access watchpoint was triggered.
26962 @item function-finished
26963 An -exec-finish or similar CLI command was accomplished.
26964 @item location-reached
26965 An -exec-until or similar CLI command was accomplished.
26966 @item watchpoint-scope
26967 A watchpoint has gone out of scope.
26968 @item end-stepping-range
26969 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26970 similar CLI command was accomplished.
26971 @item exited-signalled
26972 The inferior exited because of a signal.
26974 The inferior exited.
26975 @item exited-normally
26976 The inferior exited normally.
26977 @item signal-received
26978 A signal was received by the inferior.
26980 The inferior has stopped due to a library being loaded or unloaded.
26981 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26982 set or when a @code{catch load} or @code{catch unload} catchpoint is
26983 in use (@pxref{Set Catchpoints}).
26985 The inferior has forked. This is reported when @code{catch fork}
26986 (@pxref{Set Catchpoints}) has been used.
26988 The inferior has vforked. This is reported in when @code{catch vfork}
26989 (@pxref{Set Catchpoints}) has been used.
26990 @item syscall-entry
26991 The inferior entered a system call. This is reported when @code{catch
26992 syscall} (@pxref{Set Catchpoints}) has been used.
26993 @item syscall-return
26994 The inferior returned from a system call. This is reported when
26995 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26997 The inferior called @code{exec}. This is reported when @code{catch exec}
26998 (@pxref{Set Catchpoints}) has been used.
27001 The @var{id} field identifies the global thread ID of the thread
27002 that directly caused the stop -- for example by hitting a breakpoint.
27003 Depending on whether all-stop
27004 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27005 stop all threads, or only the thread that directly triggered the stop.
27006 If all threads are stopped, the @var{stopped} field will have the
27007 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27008 field will be a list of thread identifiers. Presently, this list will
27009 always include a single thread, but frontend should be prepared to see
27010 several threads in the list. The @var{core} field reports the
27011 processor core on which the stop event has happened. This field may be absent
27012 if such information is not available.
27014 @item =thread-group-added,id="@var{id}"
27015 @itemx =thread-group-removed,id="@var{id}"
27016 A thread group was either added or removed. The @var{id} field
27017 contains the @value{GDBN} identifier of the thread group. When a thread
27018 group is added, it generally might not be associated with a running
27019 process. When a thread group is removed, its id becomes invalid and
27020 cannot be used in any way.
27022 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27023 A thread group became associated with a running program,
27024 either because the program was just started or the thread group
27025 was attached to a program. The @var{id} field contains the
27026 @value{GDBN} identifier of the thread group. The @var{pid} field
27027 contains process identifier, specific to the operating system.
27029 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27030 A thread group is no longer associated with a running program,
27031 either because the program has exited, or because it was detached
27032 from. The @var{id} field contains the @value{GDBN} identifier of the
27033 thread group. The @var{code} field is the exit code of the inferior; it exists
27034 only when the inferior exited with some code.
27036 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27037 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27038 A thread either was created, or has exited. The @var{id} field
27039 contains the global @value{GDBN} identifier of the thread. The @var{gid}
27040 field identifies the thread group this thread belongs to.
27042 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
27043 Informs that the selected thread or frame were changed. This notification
27044 is not emitted as result of the @code{-thread-select} or
27045 @code{-stack-select-frame} commands, but is emitted whenever an MI command
27046 that is not documented to change the selected thread and frame actually
27047 changes them. In particular, invoking, directly or indirectly
27048 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
27049 will generate this notification. Changing the thread or frame from another
27050 user interface (see @ref{Interpreters}) will also generate this notification.
27052 The @var{frame} field is only present if the newly selected thread is
27053 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
27055 We suggest that in response to this notification, front ends
27056 highlight the selected thread and cause subsequent commands to apply to
27059 @item =library-loaded,...
27060 Reports that a new library file was loaded by the program. This
27061 notification has 5 fields---@var{id}, @var{target-name},
27062 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
27063 opaque identifier of the library. For remote debugging case,
27064 @var{target-name} and @var{host-name} fields give the name of the
27065 library file on the target, and on the host respectively. For native
27066 debugging, both those fields have the same value. The
27067 @var{symbols-loaded} field is emitted only for backward compatibility
27068 and should not be relied on to convey any useful information. The
27069 @var{thread-group} field, if present, specifies the id of the thread
27070 group in whose context the library was loaded. If the field is
27071 absent, it means the library was loaded in the context of all present
27072 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
27075 @item =library-unloaded,...
27076 Reports that a library was unloaded by the program. This notification
27077 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27078 the same meaning as for the @code{=library-loaded} notification.
27079 The @var{thread-group} field, if present, specifies the id of the
27080 thread group in whose context the library was unloaded. If the field is
27081 absent, it means the library was unloaded in the context of all present
27084 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
27085 @itemx =traceframe-changed,end
27086 Reports that the trace frame was changed and its new number is
27087 @var{tfnum}. The number of the tracepoint associated with this trace
27088 frame is @var{tpnum}.
27090 @item =tsv-created,name=@var{name},initial=@var{initial}
27091 Reports that the new trace state variable @var{name} is created with
27092 initial value @var{initial}.
27094 @item =tsv-deleted,name=@var{name}
27095 @itemx =tsv-deleted
27096 Reports that the trace state variable @var{name} is deleted or all
27097 trace state variables are deleted.
27099 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
27100 Reports that the trace state variable @var{name} is modified with
27101 the initial value @var{initial}. The current value @var{current} of
27102 trace state variable is optional and is reported if the current
27103 value of trace state variable is known.
27105 @item =breakpoint-created,bkpt=@{...@}
27106 @itemx =breakpoint-modified,bkpt=@{...@}
27107 @itemx =breakpoint-deleted,id=@var{number}
27108 Reports that a breakpoint was created, modified, or deleted,
27109 respectively. Only user-visible breakpoints are reported to the MI
27112 The @var{bkpt} argument is of the same form as returned by the various
27113 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
27114 @var{number} is the ordinal number of the breakpoint.
27116 Note that if a breakpoint is emitted in the result record of a
27117 command, then it will not also be emitted in an async record.
27119 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
27120 @itemx =record-stopped,thread-group="@var{id}"
27121 Execution log recording was either started or stopped on an
27122 inferior. The @var{id} is the @value{GDBN} identifier of the thread
27123 group corresponding to the affected inferior.
27125 The @var{method} field indicates the method used to record execution. If the
27126 method in use supports multiple recording formats, @var{format} will be present
27127 and contain the currently used format. @xref{Process Record and Replay},
27128 for existing method and format values.
27130 @item =cmd-param-changed,param=@var{param},value=@var{value}
27131 Reports that a parameter of the command @code{set @var{param}} is
27132 changed to @var{value}. In the multi-word @code{set} command,
27133 the @var{param} is the whole parameter list to @code{set} command.
27134 For example, In command @code{set check type on}, @var{param}
27135 is @code{check type} and @var{value} is @code{on}.
27137 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
27138 Reports that bytes from @var{addr} to @var{data} + @var{len} were
27139 written in an inferior. The @var{id} is the identifier of the
27140 thread group corresponding to the affected inferior. The optional
27141 @code{type="code"} part is reported if the memory written to holds
27145 @node GDB/MI Breakpoint Information
27146 @subsection @sc{gdb/mi} Breakpoint Information
27148 When @value{GDBN} reports information about a breakpoint, a
27149 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
27154 The breakpoint number. For a breakpoint that represents one location
27155 of a multi-location breakpoint, this will be a dotted pair, like
27159 The type of the breakpoint. For ordinary breakpoints this will be
27160 @samp{breakpoint}, but many values are possible.
27163 If the type of the breakpoint is @samp{catchpoint}, then this
27164 indicates the exact type of catchpoint.
27167 This is the breakpoint disposition---either @samp{del}, meaning that
27168 the breakpoint will be deleted at the next stop, or @samp{keep},
27169 meaning that the breakpoint will not be deleted.
27172 This indicates whether the breakpoint is enabled, in which case the
27173 value is @samp{y}, or disabled, in which case the value is @samp{n}.
27174 Note that this is not the same as the field @code{enable}.
27177 The address of the breakpoint. This may be a hexidecimal number,
27178 giving the address; or the string @samp{<PENDING>}, for a pending
27179 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
27180 multiple locations. This field will not be present if no address can
27181 be determined. For example, a watchpoint does not have an address.
27184 If known, the function in which the breakpoint appears.
27185 If not known, this field is not present.
27188 The name of the source file which contains this function, if known.
27189 If not known, this field is not present.
27192 The full file name of the source file which contains this function, if
27193 known. If not known, this field is not present.
27196 The line number at which this breakpoint appears, if known.
27197 If not known, this field is not present.
27200 If the source file is not known, this field may be provided. If
27201 provided, this holds the address of the breakpoint, possibly followed
27205 If this breakpoint is pending, this field is present and holds the
27206 text used to set the breakpoint, as entered by the user.
27209 Where this breakpoint's condition is evaluated, either @samp{host} or
27213 If this is a thread-specific breakpoint, then this identifies the
27214 thread in which the breakpoint can trigger.
27217 If this breakpoint is restricted to a particular Ada task, then this
27218 field will hold the task identifier.
27221 If the breakpoint is conditional, this is the condition expression.
27224 The ignore count of the breakpoint.
27227 The enable count of the breakpoint.
27229 @item traceframe-usage
27232 @item static-tracepoint-marker-string-id
27233 For a static tracepoint, the name of the static tracepoint marker.
27236 For a masked watchpoint, this is the mask.
27239 A tracepoint's pass count.
27241 @item original-location
27242 The location of the breakpoint as originally specified by the user.
27243 This field is optional.
27246 The number of times the breakpoint has been hit.
27249 This field is only given for tracepoints. This is either @samp{y},
27250 meaning that the tracepoint is installed, or @samp{n}, meaning that it
27254 Some extra data, the exact contents of which are type-dependent.
27258 For example, here is what the output of @code{-break-insert}
27259 (@pxref{GDB/MI Breakpoint Commands}) might be:
27262 -> -break-insert main
27263 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27264 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27265 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27270 @node GDB/MI Frame Information
27271 @subsection @sc{gdb/mi} Frame Information
27273 Response from many MI commands includes an information about stack
27274 frame. This information is a tuple that may have the following
27279 The level of the stack frame. The innermost frame has the level of
27280 zero. This field is always present.
27283 The name of the function corresponding to the frame. This field may
27284 be absent if @value{GDBN} is unable to determine the function name.
27287 The code address for the frame. This field is always present.
27290 The name of the source files that correspond to the frame's code
27291 address. This field may be absent.
27294 The source line corresponding to the frames' code address. This field
27298 The name of the binary file (either executable or shared library) the
27299 corresponds to the frame's code address. This field may be absent.
27303 @node GDB/MI Thread Information
27304 @subsection @sc{gdb/mi} Thread Information
27306 Whenever @value{GDBN} has to report an information about a thread, it
27307 uses a tuple with the following fields. The fields are always present unless
27312 The global numeric id assigned to the thread by @value{GDBN}.
27315 The target-specific string identifying the thread.
27318 Additional information about the thread provided by the target.
27319 It is supposed to be human-readable and not interpreted by the
27320 frontend. This field is optional.
27323 The name of the thread. If the user specified a name using the
27324 @code{thread name} command, then this name is given. Otherwise, if
27325 @value{GDBN} can extract the thread name from the target, then that
27326 name is given. If @value{GDBN} cannot find the thread name, then this
27330 The execution state of the thread, either @samp{stopped} or @samp{running},
27331 depending on whether the thread is presently running.
27334 The stack frame currently executing in the thread. This field is only present
27335 if the thread is stopped. Its format is documented in
27336 @ref{GDB/MI Frame Information}.
27339 The value of this field is an integer number of the processor core the
27340 thread was last seen on. This field is optional.
27343 @node GDB/MI Ada Exception Information
27344 @subsection @sc{gdb/mi} Ada Exception Information
27346 Whenever a @code{*stopped} record is emitted because the program
27347 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27348 @value{GDBN} provides the name of the exception that was raised via
27349 the @code{exception-name} field. Also, for exceptions that were raised
27350 with an exception message, @value{GDBN} provides that message via
27351 the @code{exception-message} field.
27353 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27354 @node GDB/MI Simple Examples
27355 @section Simple Examples of @sc{gdb/mi} Interaction
27356 @cindex @sc{gdb/mi}, simple examples
27358 This subsection presents several simple examples of interaction using
27359 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27360 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27361 the output received from @sc{gdb/mi}.
27363 Note the line breaks shown in the examples are here only for
27364 readability, they don't appear in the real output.
27366 @subheading Setting a Breakpoint
27368 Setting a breakpoint generates synchronous output which contains detailed
27369 information of the breakpoint.
27372 -> -break-insert main
27373 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27374 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27375 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27380 @subheading Program Execution
27382 Program execution generates asynchronous records and MI gives the
27383 reason that execution stopped.
27389 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27390 frame=@{addr="0x08048564",func="main",
27391 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
27392 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
27397 <- *stopped,reason="exited-normally"
27401 @subheading Quitting @value{GDBN}
27403 Quitting @value{GDBN} just prints the result class @samp{^exit}.
27411 Please note that @samp{^exit} is printed immediately, but it might
27412 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
27413 performs necessary cleanups, including killing programs being debugged
27414 or disconnecting from debug hardware, so the frontend should wait till
27415 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
27416 fails to exit in reasonable time.
27418 @subheading A Bad Command
27420 Here's what happens if you pass a non-existent command:
27424 <- ^error,msg="Undefined MI command: rubbish"
27429 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27430 @node GDB/MI Command Description Format
27431 @section @sc{gdb/mi} Command Description Format
27433 The remaining sections describe blocks of commands. Each block of
27434 commands is laid out in a fashion similar to this section.
27436 @subheading Motivation
27438 The motivation for this collection of commands.
27440 @subheading Introduction
27442 A brief introduction to this collection of commands as a whole.
27444 @subheading Commands
27446 For each command in the block, the following is described:
27448 @subsubheading Synopsis
27451 -command @var{args}@dots{}
27454 @subsubheading Result
27456 @subsubheading @value{GDBN} Command
27458 The corresponding @value{GDBN} CLI command(s), if any.
27460 @subsubheading Example
27462 Example(s) formatted for readability. Some of the described commands have
27463 not been implemented yet and these are labeled N.A.@: (not available).
27466 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27467 @node GDB/MI Breakpoint Commands
27468 @section @sc{gdb/mi} Breakpoint Commands
27470 @cindex breakpoint commands for @sc{gdb/mi}
27471 @cindex @sc{gdb/mi}, breakpoint commands
27472 This section documents @sc{gdb/mi} commands for manipulating
27475 @subheading The @code{-break-after} Command
27476 @findex -break-after
27478 @subsubheading Synopsis
27481 -break-after @var{number} @var{count}
27484 The breakpoint number @var{number} is not in effect until it has been
27485 hit @var{count} times. To see how this is reflected in the output of
27486 the @samp{-break-list} command, see the description of the
27487 @samp{-break-list} command below.
27489 @subsubheading @value{GDBN} Command
27491 The corresponding @value{GDBN} command is @samp{ignore}.
27493 @subsubheading Example
27498 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27499 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27500 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27508 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27509 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27510 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27511 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27512 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27513 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27514 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27515 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27516 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27517 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
27522 @subheading The @code{-break-catch} Command
27523 @findex -break-catch
27526 @subheading The @code{-break-commands} Command
27527 @findex -break-commands
27529 @subsubheading Synopsis
27532 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27535 Specifies the CLI commands that should be executed when breakpoint
27536 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27537 are the commands. If no command is specified, any previously-set
27538 commands are cleared. @xref{Break Commands}. Typical use of this
27539 functionality is tracing a program, that is, printing of values of
27540 some variables whenever breakpoint is hit and then continuing.
27542 @subsubheading @value{GDBN} Command
27544 The corresponding @value{GDBN} command is @samp{commands}.
27546 @subsubheading Example
27551 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27552 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27553 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27556 -break-commands 1 "print v" "continue"
27561 @subheading The @code{-break-condition} Command
27562 @findex -break-condition
27564 @subsubheading Synopsis
27567 -break-condition @var{number} @var{expr}
27570 Breakpoint @var{number} will stop the program only if the condition in
27571 @var{expr} is true. The condition becomes part of the
27572 @samp{-break-list} output (see the description of the @samp{-break-list}
27575 @subsubheading @value{GDBN} Command
27577 The corresponding @value{GDBN} command is @samp{condition}.
27579 @subsubheading Example
27583 -break-condition 1 1
27587 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27588 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27589 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27590 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27591 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27592 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27593 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27594 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27595 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27596 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
27600 @subheading The @code{-break-delete} Command
27601 @findex -break-delete
27603 @subsubheading Synopsis
27606 -break-delete ( @var{breakpoint} )+
27609 Delete the breakpoint(s) whose number(s) are specified in the argument
27610 list. This is obviously reflected in the breakpoint list.
27612 @subsubheading @value{GDBN} Command
27614 The corresponding @value{GDBN} command is @samp{delete}.
27616 @subsubheading Example
27624 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27625 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27626 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27627 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27628 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27629 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27630 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27635 @subheading The @code{-break-disable} Command
27636 @findex -break-disable
27638 @subsubheading Synopsis
27641 -break-disable ( @var{breakpoint} )+
27644 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27645 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27647 @subsubheading @value{GDBN} Command
27649 The corresponding @value{GDBN} command is @samp{disable}.
27651 @subsubheading Example
27659 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27660 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27661 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27662 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27663 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27664 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27665 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27666 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27667 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27668 line="5",thread-groups=["i1"],times="0"@}]@}
27672 @subheading The @code{-break-enable} Command
27673 @findex -break-enable
27675 @subsubheading Synopsis
27678 -break-enable ( @var{breakpoint} )+
27681 Enable (previously disabled) @var{breakpoint}(s).
27683 @subsubheading @value{GDBN} Command
27685 The corresponding @value{GDBN} command is @samp{enable}.
27687 @subsubheading Example
27695 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27696 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27697 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27698 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27699 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27700 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27701 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27702 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27703 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27704 line="5",thread-groups=["i1"],times="0"@}]@}
27708 @subheading The @code{-break-info} Command
27709 @findex -break-info
27711 @subsubheading Synopsis
27714 -break-info @var{breakpoint}
27718 Get information about a single breakpoint.
27720 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
27721 Information}, for details on the format of each breakpoint in the
27724 @subsubheading @value{GDBN} Command
27726 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27728 @subsubheading Example
27731 @subheading The @code{-break-insert} Command
27732 @findex -break-insert
27733 @anchor{-break-insert}
27735 @subsubheading Synopsis
27738 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27739 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27740 [ -p @var{thread-id} ] [ @var{location} ]
27744 If specified, @var{location}, can be one of:
27747 @item linespec location
27748 A linespec location. @xref{Linespec Locations}.
27750 @item explicit location
27751 An explicit location. @sc{gdb/mi} explicit locations are
27752 analogous to the CLI's explicit locations using the option names
27753 listed below. @xref{Explicit Locations}.
27756 @item --source @var{filename}
27757 The source file name of the location. This option requires the use
27758 of either @samp{--function} or @samp{--line}.
27760 @item --function @var{function}
27761 The name of a function or method.
27763 @item --label @var{label}
27764 The name of a label.
27766 @item --line @var{lineoffset}
27767 An absolute or relative line offset from the start of the location.
27770 @item address location
27771 An address location, *@var{address}. @xref{Address Locations}.
27775 The possible optional parameters of this command are:
27779 Insert a temporary breakpoint.
27781 Insert a hardware breakpoint.
27783 If @var{location} cannot be parsed (for example if it
27784 refers to unknown files or functions), create a pending
27785 breakpoint. Without this flag, @value{GDBN} will report
27786 an error, and won't create a breakpoint, if @var{location}
27789 Create a disabled breakpoint.
27791 Create a tracepoint. @xref{Tracepoints}. When this parameter
27792 is used together with @samp{-h}, a fast tracepoint is created.
27793 @item -c @var{condition}
27794 Make the breakpoint conditional on @var{condition}.
27795 @item -i @var{ignore-count}
27796 Initialize the @var{ignore-count}.
27797 @item -p @var{thread-id}
27798 Restrict the breakpoint to the thread with the specified global
27802 @subsubheading Result
27804 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27805 resulting breakpoint.
27807 Note: this format is open to change.
27808 @c An out-of-band breakpoint instead of part of the result?
27810 @subsubheading @value{GDBN} Command
27812 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27813 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
27815 @subsubheading Example
27820 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27821 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
27824 -break-insert -t foo
27825 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27826 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
27830 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27831 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27832 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27833 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27834 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27835 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27836 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27837 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27838 addr="0x0001072c", func="main",file="recursive2.c",
27839 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
27841 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27842 addr="0x00010774",func="foo",file="recursive2.c",
27843 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27846 @c -break-insert -r foo.*
27847 @c ~int foo(int, int);
27848 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27849 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27854 @subheading The @code{-dprintf-insert} Command
27855 @findex -dprintf-insert
27857 @subsubheading Synopsis
27860 -dprintf-insert [ -t ] [ -f ] [ -d ]
27861 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27862 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
27867 If supplied, @var{location} may be specified the same way as for
27868 the @code{-break-insert} command. @xref{-break-insert}.
27870 The possible optional parameters of this command are:
27874 Insert a temporary breakpoint.
27876 If @var{location} cannot be parsed (for example, if it
27877 refers to unknown files or functions), create a pending
27878 breakpoint. Without this flag, @value{GDBN} will report
27879 an error, and won't create a breakpoint, if @var{location}
27882 Create a disabled breakpoint.
27883 @item -c @var{condition}
27884 Make the breakpoint conditional on @var{condition}.
27885 @item -i @var{ignore-count}
27886 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
27887 to @var{ignore-count}.
27888 @item -p @var{thread-id}
27889 Restrict the breakpoint to the thread with the specified global
27893 @subsubheading Result
27895 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27896 resulting breakpoint.
27898 @c An out-of-band breakpoint instead of part of the result?
27900 @subsubheading @value{GDBN} Command
27902 The corresponding @value{GDBN} command is @samp{dprintf}.
27904 @subsubheading Example
27908 4-dprintf-insert foo "At foo entry\n"
27909 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
27910 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
27911 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
27912 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
27913 original-location="foo"@}
27915 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
27916 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
27917 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
27918 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
27919 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
27920 original-location="mi-dprintf.c:26"@}
27924 @subheading The @code{-break-list} Command
27925 @findex -break-list
27927 @subsubheading Synopsis
27933 Displays the list of inserted breakpoints, showing the following fields:
27937 number of the breakpoint
27939 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27941 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27944 is the breakpoint enabled or no: @samp{y} or @samp{n}
27946 memory location at which the breakpoint is set
27948 logical location of the breakpoint, expressed by function name, file
27950 @item Thread-groups
27951 list of thread groups to which this breakpoint applies
27953 number of times the breakpoint has been hit
27956 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27957 @code{body} field is an empty list.
27959 @subsubheading @value{GDBN} Command
27961 The corresponding @value{GDBN} command is @samp{info break}.
27963 @subsubheading Example
27968 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27969 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27970 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27971 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27972 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27973 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27974 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27975 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27976 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
27978 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27979 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27980 line="13",thread-groups=["i1"],times="0"@}]@}
27984 Here's an example of the result when there are no breakpoints:
27989 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27990 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27991 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27992 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27993 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27994 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27995 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28000 @subheading The @code{-break-passcount} Command
28001 @findex -break-passcount
28003 @subsubheading Synopsis
28006 -break-passcount @var{tracepoint-number} @var{passcount}
28009 Set the passcount for tracepoint @var{tracepoint-number} to
28010 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28011 is not a tracepoint, error is emitted. This corresponds to CLI
28012 command @samp{passcount}.
28014 @subheading The @code{-break-watch} Command
28015 @findex -break-watch
28017 @subsubheading Synopsis
28020 -break-watch [ -a | -r ]
28023 Create a watchpoint. With the @samp{-a} option it will create an
28024 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28025 read from or on a write to the memory location. With the @samp{-r}
28026 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28027 trigger only when the memory location is accessed for reading. Without
28028 either of the options, the watchpoint created is a regular watchpoint,
28029 i.e., it will trigger when the memory location is accessed for writing.
28030 @xref{Set Watchpoints, , Setting Watchpoints}.
28032 Note that @samp{-break-list} will report a single list of watchpoints and
28033 breakpoints inserted.
28035 @subsubheading @value{GDBN} Command
28037 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28040 @subsubheading Example
28042 Setting a watchpoint on a variable in the @code{main} function:
28047 ^done,wpt=@{number="2",exp="x"@}
28052 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28053 value=@{old="-268439212",new="55"@},
28054 frame=@{func="main",args=[],file="recursive2.c",
28055 fullname="/home/foo/bar/recursive2.c",line="5"@}
28059 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28060 the program execution twice: first for the variable changing value, then
28061 for the watchpoint going out of scope.
28066 ^done,wpt=@{number="5",exp="C"@}
28071 *stopped,reason="watchpoint-trigger",
28072 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28073 frame=@{func="callee4",args=[],
28074 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28075 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28080 *stopped,reason="watchpoint-scope",wpnum="5",
28081 frame=@{func="callee3",args=[@{name="strarg",
28082 value="0x11940 \"A string argument.\""@}],
28083 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28084 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28088 Listing breakpoints and watchpoints, at different points in the program
28089 execution. Note that once the watchpoint goes out of scope, it is
28095 ^done,wpt=@{number="2",exp="C"@}
28098 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28099 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28100 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28101 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28102 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28103 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28104 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28105 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28106 addr="0x00010734",func="callee4",
28107 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28108 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
28110 bkpt=@{number="2",type="watchpoint",disp="keep",
28111 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
28116 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28117 value=@{old="-276895068",new="3"@},
28118 frame=@{func="callee4",args=[],
28119 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28120 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28123 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28124 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28125 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28126 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28127 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28128 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28129 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28130 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28131 addr="0x00010734",func="callee4",
28132 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28133 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
28135 bkpt=@{number="2",type="watchpoint",disp="keep",
28136 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
28140 ^done,reason="watchpoint-scope",wpnum="2",
28141 frame=@{func="callee3",args=[@{name="strarg",
28142 value="0x11940 \"A string argument.\""@}],
28143 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28144 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28147 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28148 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28149 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28150 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28151 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28152 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28153 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28154 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28155 addr="0x00010734",func="callee4",
28156 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28157 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28158 thread-groups=["i1"],times="1"@}]@}
28163 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28164 @node GDB/MI Catchpoint Commands
28165 @section @sc{gdb/mi} Catchpoint Commands
28167 This section documents @sc{gdb/mi} commands for manipulating
28171 * Shared Library GDB/MI Catchpoint Commands::
28172 * Ada Exception GDB/MI Catchpoint Commands::
28175 @node Shared Library GDB/MI Catchpoint Commands
28176 @subsection Shared Library @sc{gdb/mi} Catchpoints
28178 @subheading The @code{-catch-load} Command
28179 @findex -catch-load
28181 @subsubheading Synopsis
28184 -catch-load [ -t ] [ -d ] @var{regexp}
28187 Add a catchpoint for library load events. If the @samp{-t} option is used,
28188 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28189 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
28190 in a disabled state. The @samp{regexp} argument is a regular
28191 expression used to match the name of the loaded library.
28194 @subsubheading @value{GDBN} Command
28196 The corresponding @value{GDBN} command is @samp{catch load}.
28198 @subsubheading Example
28201 -catch-load -t foo.so
28202 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
28203 what="load of library matching foo.so",catch-type="load",times="0"@}
28208 @subheading The @code{-catch-unload} Command
28209 @findex -catch-unload
28211 @subsubheading Synopsis
28214 -catch-unload [ -t ] [ -d ] @var{regexp}
28217 Add a catchpoint for library unload events. If the @samp{-t} option is
28218 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28219 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
28220 created in a disabled state. The @samp{regexp} argument is a regular
28221 expression used to match the name of the unloaded library.
28223 @subsubheading @value{GDBN} Command
28225 The corresponding @value{GDBN} command is @samp{catch unload}.
28227 @subsubheading Example
28230 -catch-unload -d bar.so
28231 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
28232 what="load of library matching bar.so",catch-type="unload",times="0"@}
28236 @node Ada Exception GDB/MI Catchpoint Commands
28237 @subsection Ada Exception @sc{gdb/mi} Catchpoints
28239 The following @sc{gdb/mi} commands can be used to create catchpoints
28240 that stop the execution when Ada exceptions are being raised.
28242 @subheading The @code{-catch-assert} Command
28243 @findex -catch-assert
28245 @subsubheading Synopsis
28248 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
28251 Add a catchpoint for failed Ada assertions.
28253 The possible optional parameters for this command are:
28256 @item -c @var{condition}
28257 Make the catchpoint conditional on @var{condition}.
28259 Create a disabled catchpoint.
28261 Create a temporary catchpoint.
28264 @subsubheading @value{GDBN} Command
28266 The corresponding @value{GDBN} command is @samp{catch assert}.
28268 @subsubheading Example
28272 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
28273 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
28274 thread-groups=["i1"],times="0",
28275 original-location="__gnat_debug_raise_assert_failure"@}
28279 @subheading The @code{-catch-exception} Command
28280 @findex -catch-exception
28282 @subsubheading Synopsis
28285 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
28289 Add a catchpoint stopping when Ada exceptions are raised.
28290 By default, the command stops the program when any Ada exception
28291 gets raised. But it is also possible, by using some of the
28292 optional parameters described below, to create more selective
28295 The possible optional parameters for this command are:
28298 @item -c @var{condition}
28299 Make the catchpoint conditional on @var{condition}.
28301 Create a disabled catchpoint.
28302 @item -e @var{exception-name}
28303 Only stop when @var{exception-name} is raised. This option cannot
28304 be used combined with @samp{-u}.
28306 Create a temporary catchpoint.
28308 Stop only when an unhandled exception gets raised. This option
28309 cannot be used combined with @samp{-e}.
28312 @subsubheading @value{GDBN} Command
28314 The corresponding @value{GDBN} commands are @samp{catch exception}
28315 and @samp{catch exception unhandled}.
28317 @subsubheading Example
28320 -catch-exception -e Program_Error
28321 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
28322 enabled="y",addr="0x0000000000404874",
28323 what="`Program_Error' Ada exception", thread-groups=["i1"],
28324 times="0",original-location="__gnat_debug_raise_exception"@}
28328 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28329 @node GDB/MI Program Context
28330 @section @sc{gdb/mi} Program Context
28332 @subheading The @code{-exec-arguments} Command
28333 @findex -exec-arguments
28336 @subsubheading Synopsis
28339 -exec-arguments @var{args}
28342 Set the inferior program arguments, to be used in the next
28345 @subsubheading @value{GDBN} Command
28347 The corresponding @value{GDBN} command is @samp{set args}.
28349 @subsubheading Example
28353 -exec-arguments -v word
28360 @subheading The @code{-exec-show-arguments} Command
28361 @findex -exec-show-arguments
28363 @subsubheading Synopsis
28366 -exec-show-arguments
28369 Print the arguments of the program.
28371 @subsubheading @value{GDBN} Command
28373 The corresponding @value{GDBN} command is @samp{show args}.
28375 @subsubheading Example
28380 @subheading The @code{-environment-cd} Command
28381 @findex -environment-cd
28383 @subsubheading Synopsis
28386 -environment-cd @var{pathdir}
28389 Set @value{GDBN}'s working directory.
28391 @subsubheading @value{GDBN} Command
28393 The corresponding @value{GDBN} command is @samp{cd}.
28395 @subsubheading Example
28399 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28405 @subheading The @code{-environment-directory} Command
28406 @findex -environment-directory
28408 @subsubheading Synopsis
28411 -environment-directory [ -r ] [ @var{pathdir} ]+
28414 Add directories @var{pathdir} to beginning of search path for source files.
28415 If the @samp{-r} option is used, the search path is reset to the default
28416 search path. If directories @var{pathdir} are supplied in addition to the
28417 @samp{-r} option, the search path is first reset and then addition
28419 Multiple directories may be specified, separated by blanks. Specifying
28420 multiple directories in a single command
28421 results in the directories added to the beginning of the
28422 search path in the same order they were presented in the command.
28423 If blanks are needed as
28424 part of a directory name, double-quotes should be used around
28425 the name. In the command output, the path will show up separated
28426 by the system directory-separator character. The directory-separator
28427 character must not be used
28428 in any directory name.
28429 If no directories are specified, the current search path is displayed.
28431 @subsubheading @value{GDBN} Command
28433 The corresponding @value{GDBN} command is @samp{dir}.
28435 @subsubheading Example
28439 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28440 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28442 -environment-directory ""
28443 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28445 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28446 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28448 -environment-directory -r
28449 ^done,source-path="$cdir:$cwd"
28454 @subheading The @code{-environment-path} Command
28455 @findex -environment-path
28457 @subsubheading Synopsis
28460 -environment-path [ -r ] [ @var{pathdir} ]+
28463 Add directories @var{pathdir} to beginning of search path for object files.
28464 If the @samp{-r} option is used, the search path is reset to the original
28465 search path that existed at gdb start-up. If directories @var{pathdir} are
28466 supplied in addition to the
28467 @samp{-r} option, the search path is first reset and then addition
28469 Multiple directories may be specified, separated by blanks. Specifying
28470 multiple directories in a single command
28471 results in the directories added to the beginning of the
28472 search path in the same order they were presented in the command.
28473 If blanks are needed as
28474 part of a directory name, double-quotes should be used around
28475 the name. In the command output, the path will show up separated
28476 by the system directory-separator character. The directory-separator
28477 character must not be used
28478 in any directory name.
28479 If no directories are specified, the current path is displayed.
28482 @subsubheading @value{GDBN} Command
28484 The corresponding @value{GDBN} command is @samp{path}.
28486 @subsubheading Example
28491 ^done,path="/usr/bin"
28493 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28494 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28496 -environment-path -r /usr/local/bin
28497 ^done,path="/usr/local/bin:/usr/bin"
28502 @subheading The @code{-environment-pwd} Command
28503 @findex -environment-pwd
28505 @subsubheading Synopsis
28511 Show the current working directory.
28513 @subsubheading @value{GDBN} Command
28515 The corresponding @value{GDBN} command is @samp{pwd}.
28517 @subsubheading Example
28522 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28526 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28527 @node GDB/MI Thread Commands
28528 @section @sc{gdb/mi} Thread Commands
28531 @subheading The @code{-thread-info} Command
28532 @findex -thread-info
28534 @subsubheading Synopsis
28537 -thread-info [ @var{thread-id} ]
28540 Reports information about either a specific thread, if the
28541 @var{thread-id} parameter is present, or about all threads.
28542 @var{thread-id} is the thread's global thread ID. When printing
28543 information about all threads, also reports the global ID of the
28546 @subsubheading @value{GDBN} Command
28548 The @samp{info thread} command prints the same information
28551 @subsubheading Result
28553 The result contains the following attributes:
28557 A list of threads. The format of the elements of the list is described in
28558 @ref{GDB/MI Thread Information}.
28560 @item current-thread-id
28561 The global id of the currently selected thread. This field is omitted if there
28562 is no selected thread (for example, when the selected inferior is not running,
28563 and therefore has no threads) or if a @var{thread-id} argument was passed to
28568 @subsubheading Example
28573 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28574 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28575 args=[]@},state="running"@},
28576 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28577 frame=@{level="0",addr="0x0804891f",func="foo",
28578 args=[@{name="i",value="10"@}],
28579 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28580 state="running"@}],
28581 current-thread-id="1"
28585 @subheading The @code{-thread-list-ids} Command
28586 @findex -thread-list-ids
28588 @subsubheading Synopsis
28594 Produces a list of the currently known global @value{GDBN} thread ids.
28595 At the end of the list it also prints the total number of such
28598 This command is retained for historical reasons, the
28599 @code{-thread-info} command should be used instead.
28601 @subsubheading @value{GDBN} Command
28603 Part of @samp{info threads} supplies the same information.
28605 @subsubheading Example
28610 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28611 current-thread-id="1",number-of-threads="3"
28616 @subheading The @code{-thread-select} Command
28617 @findex -thread-select
28619 @subsubheading Synopsis
28622 -thread-select @var{thread-id}
28625 Make thread with global thread number @var{thread-id} the current
28626 thread. It prints the number of the new current thread, and the
28627 topmost frame for that thread.
28629 This command is deprecated in favor of explicitly using the
28630 @samp{--thread} option to each command.
28632 @subsubheading @value{GDBN} Command
28634 The corresponding @value{GDBN} command is @samp{thread}.
28636 @subsubheading Example
28643 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28644 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28648 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28649 number-of-threads="3"
28652 ^done,new-thread-id="3",
28653 frame=@{level="0",func="vprintf",
28654 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28655 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28659 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28660 @node GDB/MI Ada Tasking Commands
28661 @section @sc{gdb/mi} Ada Tasking Commands
28663 @subheading The @code{-ada-task-info} Command
28664 @findex -ada-task-info
28666 @subsubheading Synopsis
28669 -ada-task-info [ @var{task-id} ]
28672 Reports information about either a specific Ada task, if the
28673 @var{task-id} parameter is present, or about all Ada tasks.
28675 @subsubheading @value{GDBN} Command
28677 The @samp{info tasks} command prints the same information
28678 about all Ada tasks (@pxref{Ada Tasks}).
28680 @subsubheading Result
28682 The result is a table of Ada tasks. The following columns are
28683 defined for each Ada task:
28687 This field exists only for the current thread. It has the value @samp{*}.
28690 The identifier that @value{GDBN} uses to refer to the Ada task.
28693 The identifier that the target uses to refer to the Ada task.
28696 The global thread identifier of the thread corresponding to the Ada
28699 This field should always exist, as Ada tasks are always implemented
28700 on top of a thread. But if @value{GDBN} cannot find this corresponding
28701 thread for any reason, the field is omitted.
28704 This field exists only when the task was created by another task.
28705 In this case, it provides the ID of the parent task.
28708 The base priority of the task.
28711 The current state of the task. For a detailed description of the
28712 possible states, see @ref{Ada Tasks}.
28715 The name of the task.
28719 @subsubheading Example
28723 ^done,tasks=@{nr_rows="3",nr_cols="8",
28724 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28725 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28726 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28727 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28728 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28729 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28730 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28731 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28732 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28733 state="Child Termination Wait",name="main_task"@}]@}
28737 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28738 @node GDB/MI Program Execution
28739 @section @sc{gdb/mi} Program Execution
28741 These are the asynchronous commands which generate the out-of-band
28742 record @samp{*stopped}. Currently @value{GDBN} only really executes
28743 asynchronously with remote targets and this interaction is mimicked in
28746 @subheading The @code{-exec-continue} Command
28747 @findex -exec-continue
28749 @subsubheading Synopsis
28752 -exec-continue [--reverse] [--all|--thread-group N]
28755 Resumes the execution of the inferior program, which will continue
28756 to execute until it reaches a debugger stop event. If the
28757 @samp{--reverse} option is specified, execution resumes in reverse until
28758 it reaches a stop event. Stop events may include
28761 breakpoints or watchpoints
28763 signals or exceptions
28765 the end of the process (or its beginning under @samp{--reverse})
28767 the end or beginning of a replay log if one is being used.
28769 In all-stop mode (@pxref{All-Stop
28770 Mode}), may resume only one thread, or all threads, depending on the
28771 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28772 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28773 ignored in all-stop mode. If the @samp{--thread-group} options is
28774 specified, then all threads in that thread group are resumed.
28776 @subsubheading @value{GDBN} Command
28778 The corresponding @value{GDBN} corresponding is @samp{continue}.
28780 @subsubheading Example
28787 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28788 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28794 @subheading The @code{-exec-finish} Command
28795 @findex -exec-finish
28797 @subsubheading Synopsis
28800 -exec-finish [--reverse]
28803 Resumes the execution of the inferior program until the current
28804 function is exited. Displays the results returned by the function.
28805 If the @samp{--reverse} option is specified, resumes the reverse
28806 execution of the inferior program until the point where current
28807 function was called.
28809 @subsubheading @value{GDBN} Command
28811 The corresponding @value{GDBN} command is @samp{finish}.
28813 @subsubheading Example
28815 Function returning @code{void}.
28822 *stopped,reason="function-finished",frame=@{func="main",args=[],
28823 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28827 Function returning other than @code{void}. The name of the internal
28828 @value{GDBN} variable storing the result is printed, together with the
28835 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28836 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28837 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28838 gdb-result-var="$1",return-value="0"
28843 @subheading The @code{-exec-interrupt} Command
28844 @findex -exec-interrupt
28846 @subsubheading Synopsis
28849 -exec-interrupt [--all|--thread-group N]
28852 Interrupts the background execution of the target. Note how the token
28853 associated with the stop message is the one for the execution command
28854 that has been interrupted. The token for the interrupt itself only
28855 appears in the @samp{^done} output. If the user is trying to
28856 interrupt a non-running program, an error message will be printed.
28858 Note that when asynchronous execution is enabled, this command is
28859 asynchronous just like other execution commands. That is, first the
28860 @samp{^done} response will be printed, and the target stop will be
28861 reported after that using the @samp{*stopped} notification.
28863 In non-stop mode, only the context thread is interrupted by default.
28864 All threads (in all inferiors) will be interrupted if the
28865 @samp{--all} option is specified. If the @samp{--thread-group}
28866 option is specified, all threads in that group will be interrupted.
28868 @subsubheading @value{GDBN} Command
28870 The corresponding @value{GDBN} command is @samp{interrupt}.
28872 @subsubheading Example
28883 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28884 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28885 fullname="/home/foo/bar/try.c",line="13"@}
28890 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28894 @subheading The @code{-exec-jump} Command
28897 @subsubheading Synopsis
28900 -exec-jump @var{location}
28903 Resumes execution of the inferior program at the location specified by
28904 parameter. @xref{Specify Location}, for a description of the
28905 different forms of @var{location}.
28907 @subsubheading @value{GDBN} Command
28909 The corresponding @value{GDBN} command is @samp{jump}.
28911 @subsubheading Example
28914 -exec-jump foo.c:10
28915 *running,thread-id="all"
28920 @subheading The @code{-exec-next} Command
28923 @subsubheading Synopsis
28926 -exec-next [--reverse]
28929 Resumes execution of the inferior program, stopping when the beginning
28930 of the next source line is reached.
28932 If the @samp{--reverse} option is specified, resumes reverse execution
28933 of the inferior program, stopping at the beginning of the previous
28934 source line. If you issue this command on the first line of a
28935 function, it will take you back to the caller of that function, to the
28936 source line where the function was called.
28939 @subsubheading @value{GDBN} Command
28941 The corresponding @value{GDBN} command is @samp{next}.
28943 @subsubheading Example
28949 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28954 @subheading The @code{-exec-next-instruction} Command
28955 @findex -exec-next-instruction
28957 @subsubheading Synopsis
28960 -exec-next-instruction [--reverse]
28963 Executes one machine instruction. If the instruction is a function
28964 call, continues until the function returns. If the program stops at an
28965 instruction in the middle of a source line, the address will be
28968 If the @samp{--reverse} option is specified, resumes reverse execution
28969 of the inferior program, stopping at the previous instruction. If the
28970 previously executed instruction was a return from another function,
28971 it will continue to execute in reverse until the call to that function
28972 (from the current stack frame) is reached.
28974 @subsubheading @value{GDBN} Command
28976 The corresponding @value{GDBN} command is @samp{nexti}.
28978 @subsubheading Example
28982 -exec-next-instruction
28986 *stopped,reason="end-stepping-range",
28987 addr="0x000100d4",line="5",file="hello.c"
28992 @subheading The @code{-exec-return} Command
28993 @findex -exec-return
28995 @subsubheading Synopsis
29001 Makes current function return immediately. Doesn't execute the inferior.
29002 Displays the new current frame.
29004 @subsubheading @value{GDBN} Command
29006 The corresponding @value{GDBN} command is @samp{return}.
29008 @subsubheading Example
29012 200-break-insert callee4
29013 200^done,bkpt=@{number="1",addr="0x00010734",
29014 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29019 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29020 frame=@{func="callee4",args=[],
29021 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29022 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29028 111^done,frame=@{level="0",func="callee3",
29029 args=[@{name="strarg",
29030 value="0x11940 \"A string argument.\""@}],
29031 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29032 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29037 @subheading The @code{-exec-run} Command
29040 @subsubheading Synopsis
29043 -exec-run [ --all | --thread-group N ] [ --start ]
29046 Starts execution of the inferior from the beginning. The inferior
29047 executes until either a breakpoint is encountered or the program
29048 exits. In the latter case the output will include an exit code, if
29049 the program has exited exceptionally.
29051 When neither the @samp{--all} nor the @samp{--thread-group} option
29052 is specified, the current inferior is started. If the
29053 @samp{--thread-group} option is specified, it should refer to a thread
29054 group of type @samp{process}, and that thread group will be started.
29055 If the @samp{--all} option is specified, then all inferiors will be started.
29057 Using the @samp{--start} option instructs the debugger to stop
29058 the execution at the start of the inferior's main subprogram,
29059 following the same behavior as the @code{start} command
29060 (@pxref{Starting}).
29062 @subsubheading @value{GDBN} Command
29064 The corresponding @value{GDBN} command is @samp{run}.
29066 @subsubheading Examples
29071 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29076 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29077 frame=@{func="main",args=[],file="recursive2.c",
29078 fullname="/home/foo/bar/recursive2.c",line="4"@}
29083 Program exited normally:
29091 *stopped,reason="exited-normally"
29096 Program exited exceptionally:
29104 *stopped,reason="exited",exit-code="01"
29108 Another way the program can terminate is if it receives a signal such as
29109 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29113 *stopped,reason="exited-signalled",signal-name="SIGINT",
29114 signal-meaning="Interrupt"
29118 @c @subheading -exec-signal
29121 @subheading The @code{-exec-step} Command
29124 @subsubheading Synopsis
29127 -exec-step [--reverse]
29130 Resumes execution of the inferior program, stopping when the beginning
29131 of the next source line is reached, if the next source line is not a
29132 function call. If it is, stop at the first instruction of the called
29133 function. If the @samp{--reverse} option is specified, resumes reverse
29134 execution of the inferior program, stopping at the beginning of the
29135 previously executed source line.
29137 @subsubheading @value{GDBN} Command
29139 The corresponding @value{GDBN} command is @samp{step}.
29141 @subsubheading Example
29143 Stepping into a function:
29149 *stopped,reason="end-stepping-range",
29150 frame=@{func="foo",args=[@{name="a",value="10"@},
29151 @{name="b",value="0"@}],file="recursive2.c",
29152 fullname="/home/foo/bar/recursive2.c",line="11"@}
29162 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29167 @subheading The @code{-exec-step-instruction} Command
29168 @findex -exec-step-instruction
29170 @subsubheading Synopsis
29173 -exec-step-instruction [--reverse]
29176 Resumes the inferior which executes one machine instruction. If the
29177 @samp{--reverse} option is specified, resumes reverse execution of the
29178 inferior program, stopping at the previously executed instruction.
29179 The output, once @value{GDBN} has stopped, will vary depending on
29180 whether we have stopped in the middle of a source line or not. In the
29181 former case, the address at which the program stopped will be printed
29184 @subsubheading @value{GDBN} Command
29186 The corresponding @value{GDBN} command is @samp{stepi}.
29188 @subsubheading Example
29192 -exec-step-instruction
29196 *stopped,reason="end-stepping-range",
29197 frame=@{func="foo",args=[],file="try.c",
29198 fullname="/home/foo/bar/try.c",line="10"@}
29200 -exec-step-instruction
29204 *stopped,reason="end-stepping-range",
29205 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29206 fullname="/home/foo/bar/try.c",line="10"@}
29211 @subheading The @code{-exec-until} Command
29212 @findex -exec-until
29214 @subsubheading Synopsis
29217 -exec-until [ @var{location} ]
29220 Executes the inferior until the @var{location} specified in the
29221 argument is reached. If there is no argument, the inferior executes
29222 until a source line greater than the current one is reached. The
29223 reason for stopping in this case will be @samp{location-reached}.
29225 @subsubheading @value{GDBN} Command
29227 The corresponding @value{GDBN} command is @samp{until}.
29229 @subsubheading Example
29233 -exec-until recursive2.c:6
29237 *stopped,reason="location-reached",frame=@{func="main",args=[],
29238 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29243 @subheading -file-clear
29244 Is this going away????
29247 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29248 @node GDB/MI Stack Manipulation
29249 @section @sc{gdb/mi} Stack Manipulation Commands
29251 @subheading The @code{-enable-frame-filters} Command
29252 @findex -enable-frame-filters
29255 -enable-frame-filters
29258 @value{GDBN} allows Python-based frame filters to affect the output of
29259 the MI commands relating to stack traces. As there is no way to
29260 implement this in a fully backward-compatible way, a front end must
29261 request that this functionality be enabled.
29263 Once enabled, this feature cannot be disabled.
29265 Note that if Python support has not been compiled into @value{GDBN},
29266 this command will still succeed (and do nothing).
29268 @subheading The @code{-stack-info-frame} Command
29269 @findex -stack-info-frame
29271 @subsubheading Synopsis
29277 Get info on the selected frame.
29279 @subsubheading @value{GDBN} Command
29281 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29282 (without arguments).
29284 @subsubheading Example
29289 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29290 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29291 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29295 @subheading The @code{-stack-info-depth} Command
29296 @findex -stack-info-depth
29298 @subsubheading Synopsis
29301 -stack-info-depth [ @var{max-depth} ]
29304 Return the depth of the stack. If the integer argument @var{max-depth}
29305 is specified, do not count beyond @var{max-depth} frames.
29307 @subsubheading @value{GDBN} Command
29309 There's no equivalent @value{GDBN} command.
29311 @subsubheading Example
29313 For a stack with frame levels 0 through 11:
29320 -stack-info-depth 4
29323 -stack-info-depth 12
29326 -stack-info-depth 11
29329 -stack-info-depth 13
29334 @anchor{-stack-list-arguments}
29335 @subheading The @code{-stack-list-arguments} Command
29336 @findex -stack-list-arguments
29338 @subsubheading Synopsis
29341 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29342 [ @var{low-frame} @var{high-frame} ]
29345 Display a list of the arguments for the frames between @var{low-frame}
29346 and @var{high-frame} (inclusive). If @var{low-frame} and
29347 @var{high-frame} are not provided, list the arguments for the whole
29348 call stack. If the two arguments are equal, show the single frame
29349 at the corresponding level. It is an error if @var{low-frame} is
29350 larger than the actual number of frames. On the other hand,
29351 @var{high-frame} may be larger than the actual number of frames, in
29352 which case only existing frames will be returned.
29354 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29355 the variables; if it is 1 or @code{--all-values}, print also their
29356 values; and if it is 2 or @code{--simple-values}, print the name,
29357 type and value for simple data types, and the name and type for arrays,
29358 structures and unions. If the option @code{--no-frame-filters} is
29359 supplied, then Python frame filters will not be executed.
29361 If the @code{--skip-unavailable} option is specified, arguments that
29362 are not available are not listed. Partially available arguments
29363 are still displayed, however.
29365 Use of this command to obtain arguments in a single frame is
29366 deprecated in favor of the @samp{-stack-list-variables} command.
29368 @subsubheading @value{GDBN} Command
29370 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29371 @samp{gdb_get_args} command which partially overlaps with the
29372 functionality of @samp{-stack-list-arguments}.
29374 @subsubheading Example
29381 frame=@{level="0",addr="0x00010734",func="callee4",
29382 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29383 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29384 frame=@{level="1",addr="0x0001076c",func="callee3",
29385 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29386 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29387 frame=@{level="2",addr="0x0001078c",func="callee2",
29388 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29389 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29390 frame=@{level="3",addr="0x000107b4",func="callee1",
29391 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29392 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29393 frame=@{level="4",addr="0x000107e0",func="main",
29394 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29395 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29397 -stack-list-arguments 0
29400 frame=@{level="0",args=[]@},
29401 frame=@{level="1",args=[name="strarg"]@},
29402 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29403 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29404 frame=@{level="4",args=[]@}]
29406 -stack-list-arguments 1
29409 frame=@{level="0",args=[]@},
29411 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29412 frame=@{level="2",args=[
29413 @{name="intarg",value="2"@},
29414 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29415 @{frame=@{level="3",args=[
29416 @{name="intarg",value="2"@},
29417 @{name="strarg",value="0x11940 \"A string argument.\""@},
29418 @{name="fltarg",value="3.5"@}]@},
29419 frame=@{level="4",args=[]@}]
29421 -stack-list-arguments 0 2 2
29422 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29424 -stack-list-arguments 1 2 2
29425 ^done,stack-args=[frame=@{level="2",
29426 args=[@{name="intarg",value="2"@},
29427 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29431 @c @subheading -stack-list-exception-handlers
29434 @anchor{-stack-list-frames}
29435 @subheading The @code{-stack-list-frames} Command
29436 @findex -stack-list-frames
29438 @subsubheading Synopsis
29441 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
29444 List the frames currently on the stack. For each frame it displays the
29449 The frame number, 0 being the topmost frame, i.e., the innermost function.
29451 The @code{$pc} value for that frame.
29455 File name of the source file where the function lives.
29456 @item @var{fullname}
29457 The full file name of the source file where the function lives.
29459 Line number corresponding to the @code{$pc}.
29461 The shared library where this function is defined. This is only given
29462 if the frame's function is not known.
29465 If invoked without arguments, this command prints a backtrace for the
29466 whole stack. If given two integer arguments, it shows the frames whose
29467 levels are between the two arguments (inclusive). If the two arguments
29468 are equal, it shows the single frame at the corresponding level. It is
29469 an error if @var{low-frame} is larger than the actual number of
29470 frames. On the other hand, @var{high-frame} may be larger than the
29471 actual number of frames, in which case only existing frames will be
29472 returned. If the option @code{--no-frame-filters} is supplied, then
29473 Python frame filters will not be executed.
29475 @subsubheading @value{GDBN} Command
29477 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29479 @subsubheading Example
29481 Full stack backtrace:
29487 [frame=@{level="0",addr="0x0001076c",func="foo",
29488 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29489 frame=@{level="1",addr="0x000107a4",func="foo",
29490 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29491 frame=@{level="2",addr="0x000107a4",func="foo",
29492 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29493 frame=@{level="3",addr="0x000107a4",func="foo",
29494 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29495 frame=@{level="4",addr="0x000107a4",func="foo",
29496 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29497 frame=@{level="5",addr="0x000107a4",func="foo",
29498 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29499 frame=@{level="6",addr="0x000107a4",func="foo",
29500 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29501 frame=@{level="7",addr="0x000107a4",func="foo",
29502 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29503 frame=@{level="8",addr="0x000107a4",func="foo",
29504 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29505 frame=@{level="9",addr="0x000107a4",func="foo",
29506 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29507 frame=@{level="10",addr="0x000107a4",func="foo",
29508 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29509 frame=@{level="11",addr="0x00010738",func="main",
29510 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29514 Show frames between @var{low_frame} and @var{high_frame}:
29518 -stack-list-frames 3 5
29520 [frame=@{level="3",addr="0x000107a4",func="foo",
29521 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29522 frame=@{level="4",addr="0x000107a4",func="foo",
29523 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29524 frame=@{level="5",addr="0x000107a4",func="foo",
29525 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29529 Show a single frame:
29533 -stack-list-frames 3 3
29535 [frame=@{level="3",addr="0x000107a4",func="foo",
29536 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29541 @subheading The @code{-stack-list-locals} Command
29542 @findex -stack-list-locals
29543 @anchor{-stack-list-locals}
29545 @subsubheading Synopsis
29548 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29551 Display the local variable names for the selected frame. If
29552 @var{print-values} is 0 or @code{--no-values}, print only the names of
29553 the variables; if it is 1 or @code{--all-values}, print also their
29554 values; and if it is 2 or @code{--simple-values}, print the name,
29555 type and value for simple data types, and the name and type for arrays,
29556 structures and unions. In this last case, a frontend can immediately
29557 display the value of simple data types and create variable objects for
29558 other data types when the user wishes to explore their values in
29559 more detail. If the option @code{--no-frame-filters} is supplied, then
29560 Python frame filters will not be executed.
29562 If the @code{--skip-unavailable} option is specified, local variables
29563 that are not available are not listed. Partially available local
29564 variables are still displayed, however.
29566 This command is deprecated in favor of the
29567 @samp{-stack-list-variables} command.
29569 @subsubheading @value{GDBN} Command
29571 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29573 @subsubheading Example
29577 -stack-list-locals 0
29578 ^done,locals=[name="A",name="B",name="C"]
29580 -stack-list-locals --all-values
29581 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29582 @{name="C",value="@{1, 2, 3@}"@}]
29583 -stack-list-locals --simple-values
29584 ^done,locals=[@{name="A",type="int",value="1"@},
29585 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29589 @anchor{-stack-list-variables}
29590 @subheading The @code{-stack-list-variables} Command
29591 @findex -stack-list-variables
29593 @subsubheading Synopsis
29596 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29599 Display the names of local variables and function arguments for the selected frame. If
29600 @var{print-values} is 0 or @code{--no-values}, print only the names of
29601 the variables; if it is 1 or @code{--all-values}, print also their
29602 values; and if it is 2 or @code{--simple-values}, print the name,
29603 type and value for simple data types, and the name and type for arrays,
29604 structures and unions. If the option @code{--no-frame-filters} is
29605 supplied, then Python frame filters will not be executed.
29607 If the @code{--skip-unavailable} option is specified, local variables
29608 and arguments that are not available are not listed. Partially
29609 available arguments and local variables are still displayed, however.
29611 @subsubheading Example
29615 -stack-list-variables --thread 1 --frame 0 --all-values
29616 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29621 @subheading The @code{-stack-select-frame} Command
29622 @findex -stack-select-frame
29624 @subsubheading Synopsis
29627 -stack-select-frame @var{framenum}
29630 Change the selected frame. Select a different frame @var{framenum} on
29633 This command in deprecated in favor of passing the @samp{--frame}
29634 option to every command.
29636 @subsubheading @value{GDBN} Command
29638 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29639 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29641 @subsubheading Example
29645 -stack-select-frame 2
29650 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29651 @node GDB/MI Variable Objects
29652 @section @sc{gdb/mi} Variable Objects
29656 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29658 For the implementation of a variable debugger window (locals, watched
29659 expressions, etc.), we are proposing the adaptation of the existing code
29660 used by @code{Insight}.
29662 The two main reasons for that are:
29666 It has been proven in practice (it is already on its second generation).
29669 It will shorten development time (needless to say how important it is
29673 The original interface was designed to be used by Tcl code, so it was
29674 slightly changed so it could be used through @sc{gdb/mi}. This section
29675 describes the @sc{gdb/mi} operations that will be available and gives some
29676 hints about their use.
29678 @emph{Note}: In addition to the set of operations described here, we
29679 expect the @sc{gui} implementation of a variable window to require, at
29680 least, the following operations:
29683 @item @code{-gdb-show} @code{output-radix}
29684 @item @code{-stack-list-arguments}
29685 @item @code{-stack-list-locals}
29686 @item @code{-stack-select-frame}
29691 @subheading Introduction to Variable Objects
29693 @cindex variable objects in @sc{gdb/mi}
29695 Variable objects are "object-oriented" MI interface for examining and
29696 changing values of expressions. Unlike some other MI interfaces that
29697 work with expressions, variable objects are specifically designed for
29698 simple and efficient presentation in the frontend. A variable object
29699 is identified by string name. When a variable object is created, the
29700 frontend specifies the expression for that variable object. The
29701 expression can be a simple variable, or it can be an arbitrary complex
29702 expression, and can even involve CPU registers. After creating a
29703 variable object, the frontend can invoke other variable object
29704 operations---for example to obtain or change the value of a variable
29705 object, or to change display format.
29707 Variable objects have hierarchical tree structure. Any variable object
29708 that corresponds to a composite type, such as structure in C, has
29709 a number of child variable objects, for example corresponding to each
29710 element of a structure. A child variable object can itself have
29711 children, recursively. Recursion ends when we reach
29712 leaf variable objects, which always have built-in types. Child variable
29713 objects are created only by explicit request, so if a frontend
29714 is not interested in the children of a particular variable object, no
29715 child will be created.
29717 For a leaf variable object it is possible to obtain its value as a
29718 string, or set the value from a string. String value can be also
29719 obtained for a non-leaf variable object, but it's generally a string
29720 that only indicates the type of the object, and does not list its
29721 contents. Assignment to a non-leaf variable object is not allowed.
29723 A frontend does not need to read the values of all variable objects each time
29724 the program stops. Instead, MI provides an update command that lists all
29725 variable objects whose values has changed since the last update
29726 operation. This considerably reduces the amount of data that must
29727 be transferred to the frontend. As noted above, children variable
29728 objects are created on demand, and only leaf variable objects have a
29729 real value. As result, gdb will read target memory only for leaf
29730 variables that frontend has created.
29732 The automatic update is not always desirable. For example, a frontend
29733 might want to keep a value of some expression for future reference,
29734 and never update it. For another example, fetching memory is
29735 relatively slow for embedded targets, so a frontend might want
29736 to disable automatic update for the variables that are either not
29737 visible on the screen, or ``closed''. This is possible using so
29738 called ``frozen variable objects''. Such variable objects are never
29739 implicitly updated.
29741 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29742 fixed variable object, the expression is parsed when the variable
29743 object is created, including associating identifiers to specific
29744 variables. The meaning of expression never changes. For a floating
29745 variable object the values of variables whose names appear in the
29746 expressions are re-evaluated every time in the context of the current
29747 frame. Consider this example:
29752 struct work_state state;
29759 If a fixed variable object for the @code{state} variable is created in
29760 this function, and we enter the recursive call, the variable
29761 object will report the value of @code{state} in the top-level
29762 @code{do_work} invocation. On the other hand, a floating variable
29763 object will report the value of @code{state} in the current frame.
29765 If an expression specified when creating a fixed variable object
29766 refers to a local variable, the variable object becomes bound to the
29767 thread and frame in which the variable object is created. When such
29768 variable object is updated, @value{GDBN} makes sure that the
29769 thread/frame combination the variable object is bound to still exists,
29770 and re-evaluates the variable object in context of that thread/frame.
29772 The following is the complete set of @sc{gdb/mi} operations defined to
29773 access this functionality:
29775 @multitable @columnfractions .4 .6
29776 @item @strong{Operation}
29777 @tab @strong{Description}
29779 @item @code{-enable-pretty-printing}
29780 @tab enable Python-based pretty-printing
29781 @item @code{-var-create}
29782 @tab create a variable object
29783 @item @code{-var-delete}
29784 @tab delete the variable object and/or its children
29785 @item @code{-var-set-format}
29786 @tab set the display format of this variable
29787 @item @code{-var-show-format}
29788 @tab show the display format of this variable
29789 @item @code{-var-info-num-children}
29790 @tab tells how many children this object has
29791 @item @code{-var-list-children}
29792 @tab return a list of the object's children
29793 @item @code{-var-info-type}
29794 @tab show the type of this variable object
29795 @item @code{-var-info-expression}
29796 @tab print parent-relative expression that this variable object represents
29797 @item @code{-var-info-path-expression}
29798 @tab print full expression that this variable object represents
29799 @item @code{-var-show-attributes}
29800 @tab is this variable editable? does it exist here?
29801 @item @code{-var-evaluate-expression}
29802 @tab get the value of this variable
29803 @item @code{-var-assign}
29804 @tab set the value of this variable
29805 @item @code{-var-update}
29806 @tab update the variable and its children
29807 @item @code{-var-set-frozen}
29808 @tab set frozeness attribute
29809 @item @code{-var-set-update-range}
29810 @tab set range of children to display on update
29813 In the next subsection we describe each operation in detail and suggest
29814 how it can be used.
29816 @subheading Description And Use of Operations on Variable Objects
29818 @subheading The @code{-enable-pretty-printing} Command
29819 @findex -enable-pretty-printing
29822 -enable-pretty-printing
29825 @value{GDBN} allows Python-based visualizers to affect the output of the
29826 MI variable object commands. However, because there was no way to
29827 implement this in a fully backward-compatible way, a front end must
29828 request that this functionality be enabled.
29830 Once enabled, this feature cannot be disabled.
29832 Note that if Python support has not been compiled into @value{GDBN},
29833 this command will still succeed (and do nothing).
29835 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29836 may work differently in future versions of @value{GDBN}.
29838 @subheading The @code{-var-create} Command
29839 @findex -var-create
29841 @subsubheading Synopsis
29844 -var-create @{@var{name} | "-"@}
29845 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29848 This operation creates a variable object, which allows the monitoring of
29849 a variable, the result of an expression, a memory cell or a CPU
29852 The @var{name} parameter is the string by which the object can be
29853 referenced. It must be unique. If @samp{-} is specified, the varobj
29854 system will generate a string ``varNNNNNN'' automatically. It will be
29855 unique provided that one does not specify @var{name} of that format.
29856 The command fails if a duplicate name is found.
29858 The frame under which the expression should be evaluated can be
29859 specified by @var{frame-addr}. A @samp{*} indicates that the current
29860 frame should be used. A @samp{@@} indicates that a floating variable
29861 object must be created.
29863 @var{expression} is any expression valid on the current language set (must not
29864 begin with a @samp{*}), or one of the following:
29868 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29871 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29874 @samp{$@var{regname}} --- a CPU register name
29877 @cindex dynamic varobj
29878 A varobj's contents may be provided by a Python-based pretty-printer. In this
29879 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29880 have slightly different semantics in some cases. If the
29881 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29882 will never create a dynamic varobj. This ensures backward
29883 compatibility for existing clients.
29885 @subsubheading Result
29887 This operation returns attributes of the newly-created varobj. These
29892 The name of the varobj.
29895 The number of children of the varobj. This number is not necessarily
29896 reliable for a dynamic varobj. Instead, you must examine the
29897 @samp{has_more} attribute.
29900 The varobj's scalar value. For a varobj whose type is some sort of
29901 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29902 will not be interesting.
29905 The varobj's type. This is a string representation of the type, as
29906 would be printed by the @value{GDBN} CLI. If @samp{print object}
29907 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29908 @emph{actual} (derived) type of the object is shown rather than the
29909 @emph{declared} one.
29912 If a variable object is bound to a specific thread, then this is the
29913 thread's global identifier.
29916 For a dynamic varobj, this indicates whether there appear to be any
29917 children available. For a non-dynamic varobj, this will be 0.
29920 This attribute will be present and have the value @samp{1} if the
29921 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29922 then this attribute will not be present.
29925 A dynamic varobj can supply a display hint to the front end. The
29926 value comes directly from the Python pretty-printer object's
29927 @code{display_hint} method. @xref{Pretty Printing API}.
29930 Typical output will look like this:
29933 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29934 has_more="@var{has_more}"
29938 @subheading The @code{-var-delete} Command
29939 @findex -var-delete
29941 @subsubheading Synopsis
29944 -var-delete [ -c ] @var{name}
29947 Deletes a previously created variable object and all of its children.
29948 With the @samp{-c} option, just deletes the children.
29950 Returns an error if the object @var{name} is not found.
29953 @subheading The @code{-var-set-format} Command
29954 @findex -var-set-format
29956 @subsubheading Synopsis
29959 -var-set-format @var{name} @var{format-spec}
29962 Sets the output format for the value of the object @var{name} to be
29965 @anchor{-var-set-format}
29966 The syntax for the @var{format-spec} is as follows:
29969 @var{format-spec} @expansion{}
29970 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
29973 The natural format is the default format choosen automatically
29974 based on the variable type (like decimal for an @code{int}, hex
29975 for pointers, etc.).
29977 The zero-hexadecimal format has a representation similar to hexadecimal
29978 but with padding zeroes to the left of the value. For example, a 32-bit
29979 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
29980 zero-hexadecimal format.
29982 For a variable with children, the format is set only on the
29983 variable itself, and the children are not affected.
29985 @subheading The @code{-var-show-format} Command
29986 @findex -var-show-format
29988 @subsubheading Synopsis
29991 -var-show-format @var{name}
29994 Returns the format used to display the value of the object @var{name}.
29997 @var{format} @expansion{}
30002 @subheading The @code{-var-info-num-children} Command
30003 @findex -var-info-num-children
30005 @subsubheading Synopsis
30008 -var-info-num-children @var{name}
30011 Returns the number of children of a variable object @var{name}:
30017 Note that this number is not completely reliable for a dynamic varobj.
30018 It will return the current number of children, but more children may
30022 @subheading The @code{-var-list-children} Command
30023 @findex -var-list-children
30025 @subsubheading Synopsis
30028 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30030 @anchor{-var-list-children}
30032 Return a list of the children of the specified variable object and
30033 create variable objects for them, if they do not already exist. With
30034 a single argument or if @var{print-values} has a value of 0 or
30035 @code{--no-values}, print only the names of the variables; if
30036 @var{print-values} is 1 or @code{--all-values}, also print their
30037 values; and if it is 2 or @code{--simple-values} print the name and
30038 value for simple data types and just the name for arrays, structures
30041 @var{from} and @var{to}, if specified, indicate the range of children
30042 to report. If @var{from} or @var{to} is less than zero, the range is
30043 reset and all children will be reported. Otherwise, children starting
30044 at @var{from} (zero-based) and up to and excluding @var{to} will be
30047 If a child range is requested, it will only affect the current call to
30048 @code{-var-list-children}, but not future calls to @code{-var-update}.
30049 For this, you must instead use @code{-var-set-update-range}. The
30050 intent of this approach is to enable a front end to implement any
30051 update approach it likes; for example, scrolling a view may cause the
30052 front end to request more children with @code{-var-list-children}, and
30053 then the front end could call @code{-var-set-update-range} with a
30054 different range to ensure that future updates are restricted to just
30057 For each child the following results are returned:
30062 Name of the variable object created for this child.
30065 The expression to be shown to the user by the front end to designate this child.
30066 For example this may be the name of a structure member.
30068 For a dynamic varobj, this value cannot be used to form an
30069 expression. There is no way to do this at all with a dynamic varobj.
30071 For C/C@t{++} structures there are several pseudo children returned to
30072 designate access qualifiers. For these pseudo children @var{exp} is
30073 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30074 type and value are not present.
30076 A dynamic varobj will not report the access qualifying
30077 pseudo-children, regardless of the language. This information is not
30078 available at all with a dynamic varobj.
30081 Number of children this child has. For a dynamic varobj, this will be
30085 The type of the child. If @samp{print object}
30086 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30087 @emph{actual} (derived) type of the object is shown rather than the
30088 @emph{declared} one.
30091 If values were requested, this is the value.
30094 If this variable object is associated with a thread, this is the
30095 thread's global thread id. Otherwise this result is not present.
30098 If the variable object is frozen, this variable will be present with a value of 1.
30101 A dynamic varobj can supply a display hint to the front end. The
30102 value comes directly from the Python pretty-printer object's
30103 @code{display_hint} method. @xref{Pretty Printing API}.
30106 This attribute will be present and have the value @samp{1} if the
30107 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30108 then this attribute will not be present.
30112 The result may have its own attributes:
30116 A dynamic varobj can supply a display hint to the front end. The
30117 value comes directly from the Python pretty-printer object's
30118 @code{display_hint} method. @xref{Pretty Printing API}.
30121 This is an integer attribute which is nonzero if there are children
30122 remaining after the end of the selected range.
30125 @subsubheading Example
30129 -var-list-children n
30130 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30131 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30133 -var-list-children --all-values n
30134 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30135 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30139 @subheading The @code{-var-info-type} Command
30140 @findex -var-info-type
30142 @subsubheading Synopsis
30145 -var-info-type @var{name}
30148 Returns the type of the specified variable @var{name}. The type is
30149 returned as a string in the same format as it is output by the
30153 type=@var{typename}
30157 @subheading The @code{-var-info-expression} Command
30158 @findex -var-info-expression
30160 @subsubheading Synopsis
30163 -var-info-expression @var{name}
30166 Returns a string that is suitable for presenting this
30167 variable object in user interface. The string is generally
30168 not valid expression in the current language, and cannot be evaluated.
30170 For example, if @code{a} is an array, and variable object
30171 @code{A} was created for @code{a}, then we'll get this output:
30174 (gdb) -var-info-expression A.1
30175 ^done,lang="C",exp="1"
30179 Here, the value of @code{lang} is the language name, which can be
30180 found in @ref{Supported Languages}.
30182 Note that the output of the @code{-var-list-children} command also
30183 includes those expressions, so the @code{-var-info-expression} command
30186 @subheading The @code{-var-info-path-expression} Command
30187 @findex -var-info-path-expression
30189 @subsubheading Synopsis
30192 -var-info-path-expression @var{name}
30195 Returns an expression that can be evaluated in the current
30196 context and will yield the same value that a variable object has.
30197 Compare this with the @code{-var-info-expression} command, which
30198 result can be used only for UI presentation. Typical use of
30199 the @code{-var-info-path-expression} command is creating a
30200 watchpoint from a variable object.
30202 This command is currently not valid for children of a dynamic varobj,
30203 and will give an error when invoked on one.
30205 For example, suppose @code{C} is a C@t{++} class, derived from class
30206 @code{Base}, and that the @code{Base} class has a member called
30207 @code{m_size}. Assume a variable @code{c} is has the type of
30208 @code{C} and a variable object @code{C} was created for variable
30209 @code{c}. Then, we'll get this output:
30211 (gdb) -var-info-path-expression C.Base.public.m_size
30212 ^done,path_expr=((Base)c).m_size)
30215 @subheading The @code{-var-show-attributes} Command
30216 @findex -var-show-attributes
30218 @subsubheading Synopsis
30221 -var-show-attributes @var{name}
30224 List attributes of the specified variable object @var{name}:
30227 status=@var{attr} [ ( ,@var{attr} )* ]
30231 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30233 @subheading The @code{-var-evaluate-expression} Command
30234 @findex -var-evaluate-expression
30236 @subsubheading Synopsis
30239 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30242 Evaluates the expression that is represented by the specified variable
30243 object and returns its value as a string. The format of the string
30244 can be specified with the @samp{-f} option. The possible values of
30245 this option are the same as for @code{-var-set-format}
30246 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30247 the current display format will be used. The current display format
30248 can be changed using the @code{-var-set-format} command.
30254 Note that one must invoke @code{-var-list-children} for a variable
30255 before the value of a child variable can be evaluated.
30257 @subheading The @code{-var-assign} Command
30258 @findex -var-assign
30260 @subsubheading Synopsis
30263 -var-assign @var{name} @var{expression}
30266 Assigns the value of @var{expression} to the variable object specified
30267 by @var{name}. The object must be @samp{editable}. If the variable's
30268 value is altered by the assign, the variable will show up in any
30269 subsequent @code{-var-update} list.
30271 @subsubheading Example
30279 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30283 @subheading The @code{-var-update} Command
30284 @findex -var-update
30286 @subsubheading Synopsis
30289 -var-update [@var{print-values}] @{@var{name} | "*"@}
30292 Reevaluate the expressions corresponding to the variable object
30293 @var{name} and all its direct and indirect children, and return the
30294 list of variable objects whose values have changed; @var{name} must
30295 be a root variable object. Here, ``changed'' means that the result of
30296 @code{-var-evaluate-expression} before and after the
30297 @code{-var-update} is different. If @samp{*} is used as the variable
30298 object names, all existing variable objects are updated, except
30299 for frozen ones (@pxref{-var-set-frozen}). The option
30300 @var{print-values} determines whether both names and values, or just
30301 names are printed. The possible values of this option are the same
30302 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30303 recommended to use the @samp{--all-values} option, to reduce the
30304 number of MI commands needed on each program stop.
30306 With the @samp{*} parameter, if a variable object is bound to a
30307 currently running thread, it will not be updated, without any
30310 If @code{-var-set-update-range} was previously used on a varobj, then
30311 only the selected range of children will be reported.
30313 @code{-var-update} reports all the changed varobjs in a tuple named
30316 Each item in the change list is itself a tuple holding:
30320 The name of the varobj.
30323 If values were requested for this update, then this field will be
30324 present and will hold the value of the varobj.
30327 @anchor{-var-update}
30328 This field is a string which may take one of three values:
30332 The variable object's current value is valid.
30335 The variable object does not currently hold a valid value but it may
30336 hold one in the future if its associated expression comes back into
30340 The variable object no longer holds a valid value.
30341 This can occur when the executable file being debugged has changed,
30342 either through recompilation or by using the @value{GDBN} @code{file}
30343 command. The front end should normally choose to delete these variable
30347 In the future new values may be added to this list so the front should
30348 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30351 This is only present if the varobj is still valid. If the type
30352 changed, then this will be the string @samp{true}; otherwise it will
30355 When a varobj's type changes, its children are also likely to have
30356 become incorrect. Therefore, the varobj's children are automatically
30357 deleted when this attribute is @samp{true}. Also, the varobj's update
30358 range, when set using the @code{-var-set-update-range} command, is
30362 If the varobj's type changed, then this field will be present and will
30365 @item new_num_children
30366 For a dynamic varobj, if the number of children changed, or if the
30367 type changed, this will be the new number of children.
30369 The @samp{numchild} field in other varobj responses is generally not
30370 valid for a dynamic varobj -- it will show the number of children that
30371 @value{GDBN} knows about, but because dynamic varobjs lazily
30372 instantiate their children, this will not reflect the number of
30373 children which may be available.
30375 The @samp{new_num_children} attribute only reports changes to the
30376 number of children known by @value{GDBN}. This is the only way to
30377 detect whether an update has removed children (which necessarily can
30378 only happen at the end of the update range).
30381 The display hint, if any.
30384 This is an integer value, which will be 1 if there are more children
30385 available outside the varobj's update range.
30388 This attribute will be present and have the value @samp{1} if the
30389 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30390 then this attribute will not be present.
30393 If new children were added to a dynamic varobj within the selected
30394 update range (as set by @code{-var-set-update-range}), then they will
30395 be listed in this attribute.
30398 @subsubheading Example
30405 -var-update --all-values var1
30406 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30407 type_changed="false"@}]
30411 @subheading The @code{-var-set-frozen} Command
30412 @findex -var-set-frozen
30413 @anchor{-var-set-frozen}
30415 @subsubheading Synopsis
30418 -var-set-frozen @var{name} @var{flag}
30421 Set the frozenness flag on the variable object @var{name}. The
30422 @var{flag} parameter should be either @samp{1} to make the variable
30423 frozen or @samp{0} to make it unfrozen. If a variable object is
30424 frozen, then neither itself, nor any of its children, are
30425 implicitly updated by @code{-var-update} of
30426 a parent variable or by @code{-var-update *}. Only
30427 @code{-var-update} of the variable itself will update its value and
30428 values of its children. After a variable object is unfrozen, it is
30429 implicitly updated by all subsequent @code{-var-update} operations.
30430 Unfreezing a variable does not update it, only subsequent
30431 @code{-var-update} does.
30433 @subsubheading Example
30437 -var-set-frozen V 1
30442 @subheading The @code{-var-set-update-range} command
30443 @findex -var-set-update-range
30444 @anchor{-var-set-update-range}
30446 @subsubheading Synopsis
30449 -var-set-update-range @var{name} @var{from} @var{to}
30452 Set the range of children to be returned by future invocations of
30453 @code{-var-update}.
30455 @var{from} and @var{to} indicate the range of children to report. If
30456 @var{from} or @var{to} is less than zero, the range is reset and all
30457 children will be reported. Otherwise, children starting at @var{from}
30458 (zero-based) and up to and excluding @var{to} will be reported.
30460 @subsubheading Example
30464 -var-set-update-range V 1 2
30468 @subheading The @code{-var-set-visualizer} command
30469 @findex -var-set-visualizer
30470 @anchor{-var-set-visualizer}
30472 @subsubheading Synopsis
30475 -var-set-visualizer @var{name} @var{visualizer}
30478 Set a visualizer for the variable object @var{name}.
30480 @var{visualizer} is the visualizer to use. The special value
30481 @samp{None} means to disable any visualizer in use.
30483 If not @samp{None}, @var{visualizer} must be a Python expression.
30484 This expression must evaluate to a callable object which accepts a
30485 single argument. @value{GDBN} will call this object with the value of
30486 the varobj @var{name} as an argument (this is done so that the same
30487 Python pretty-printing code can be used for both the CLI and MI).
30488 When called, this object must return an object which conforms to the
30489 pretty-printing interface (@pxref{Pretty Printing API}).
30491 The pre-defined function @code{gdb.default_visualizer} may be used to
30492 select a visualizer by following the built-in process
30493 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30494 a varobj is created, and so ordinarily is not needed.
30496 This feature is only available if Python support is enabled. The MI
30497 command @code{-list-features} (@pxref{GDB/MI Support Commands})
30498 can be used to check this.
30500 @subsubheading Example
30502 Resetting the visualizer:
30506 -var-set-visualizer V None
30510 Reselecting the default (type-based) visualizer:
30514 -var-set-visualizer V gdb.default_visualizer
30518 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30519 can be used to instantiate this class for a varobj:
30523 -var-set-visualizer V "lambda val: SomeClass()"
30527 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30528 @node GDB/MI Data Manipulation
30529 @section @sc{gdb/mi} Data Manipulation
30531 @cindex data manipulation, in @sc{gdb/mi}
30532 @cindex @sc{gdb/mi}, data manipulation
30533 This section describes the @sc{gdb/mi} commands that manipulate data:
30534 examine memory and registers, evaluate expressions, etc.
30536 For details about what an addressable memory unit is,
30537 @pxref{addressable memory unit}.
30539 @c REMOVED FROM THE INTERFACE.
30540 @c @subheading -data-assign
30541 @c Change the value of a program variable. Plenty of side effects.
30542 @c @subsubheading GDB Command
30544 @c @subsubheading Example
30547 @subheading The @code{-data-disassemble} Command
30548 @findex -data-disassemble
30550 @subsubheading Synopsis
30554 [ -s @var{start-addr} -e @var{end-addr} ]
30555 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30563 @item @var{start-addr}
30564 is the beginning address (or @code{$pc})
30565 @item @var{end-addr}
30567 @item @var{filename}
30568 is the name of the file to disassemble
30569 @item @var{linenum}
30570 is the line number to disassemble around
30572 is the number of disassembly lines to be produced. If it is -1,
30573 the whole function will be disassembled, in case no @var{end-addr} is
30574 specified. If @var{end-addr} is specified as a non-zero value, and
30575 @var{lines} is lower than the number of disassembly lines between
30576 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30577 displayed; if @var{lines} is higher than the number of lines between
30578 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30583 @item 0 disassembly only
30584 @item 1 mixed source and disassembly (deprecated)
30585 @item 2 disassembly with raw opcodes
30586 @item 3 mixed source and disassembly with raw opcodes (deprecated)
30587 @item 4 mixed source and disassembly
30588 @item 5 mixed source and disassembly with raw opcodes
30591 Modes 1 and 3 are deprecated. The output is ``source centric''
30592 which hasn't proved useful in practice.
30593 @xref{Machine Code}, for a discussion of the difference between
30594 @code{/m} and @code{/s} output of the @code{disassemble} command.
30597 @subsubheading Result
30599 The result of the @code{-data-disassemble} command will be a list named
30600 @samp{asm_insns}, the contents of this list depend on the @var{mode}
30601 used with the @code{-data-disassemble} command.
30603 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
30608 The address at which this instruction was disassembled.
30611 The name of the function this instruction is within.
30614 The decimal offset in bytes from the start of @samp{func-name}.
30617 The text disassembly for this @samp{address}.
30620 This field is only present for modes 2, 3 and 5. This contains the raw opcode
30621 bytes for the @samp{inst} field.
30625 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
30626 @samp{src_and_asm_line}, each of which has the following fields:
30630 The line number within @samp{file}.
30633 The file name from the compilation unit. This might be an absolute
30634 file name or a relative file name depending on the compile command
30638 Absolute file name of @samp{file}. It is converted to a canonical form
30639 using the source file search path
30640 (@pxref{Source Path, ,Specifying Source Directories})
30641 and after resolving all the symbolic links.
30643 If the source file is not found this field will contain the path as
30644 present in the debug information.
30646 @item line_asm_insn
30647 This is a list of tuples containing the disassembly for @samp{line} in
30648 @samp{file}. The fields of each tuple are the same as for
30649 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
30650 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
30655 Note that whatever included in the @samp{inst} field, is not
30656 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
30659 @subsubheading @value{GDBN} Command
30661 The corresponding @value{GDBN} command is @samp{disassemble}.
30663 @subsubheading Example
30665 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30669 -data-disassemble -s $pc -e "$pc + 20" -- 0
30672 @{address="0x000107c0",func-name="main",offset="4",
30673 inst="mov 2, %o0"@},
30674 @{address="0x000107c4",func-name="main",offset="8",
30675 inst="sethi %hi(0x11800), %o2"@},
30676 @{address="0x000107c8",func-name="main",offset="12",
30677 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30678 @{address="0x000107cc",func-name="main",offset="16",
30679 inst="sethi %hi(0x11800), %o2"@},
30680 @{address="0x000107d0",func-name="main",offset="20",
30681 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30685 Disassemble the whole @code{main} function. Line 32 is part of
30689 -data-disassemble -f basics.c -l 32 -- 0
30691 @{address="0x000107bc",func-name="main",offset="0",
30692 inst="save %sp, -112, %sp"@},
30693 @{address="0x000107c0",func-name="main",offset="4",
30694 inst="mov 2, %o0"@},
30695 @{address="0x000107c4",func-name="main",offset="8",
30696 inst="sethi %hi(0x11800), %o2"@},
30698 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30699 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30703 Disassemble 3 instructions from the start of @code{main}:
30707 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30709 @{address="0x000107bc",func-name="main",offset="0",
30710 inst="save %sp, -112, %sp"@},
30711 @{address="0x000107c0",func-name="main",offset="4",
30712 inst="mov 2, %o0"@},
30713 @{address="0x000107c4",func-name="main",offset="8",
30714 inst="sethi %hi(0x11800), %o2"@}]
30718 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30722 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30724 src_and_asm_line=@{line="31",
30725 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30726 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30727 line_asm_insn=[@{address="0x000107bc",
30728 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
30729 src_and_asm_line=@{line="32",
30730 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30731 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30732 line_asm_insn=[@{address="0x000107c0",
30733 func-name="main",offset="4",inst="mov 2, %o0"@},
30734 @{address="0x000107c4",func-name="main",offset="8",
30735 inst="sethi %hi(0x11800), %o2"@}]@}]
30740 @subheading The @code{-data-evaluate-expression} Command
30741 @findex -data-evaluate-expression
30743 @subsubheading Synopsis
30746 -data-evaluate-expression @var{expr}
30749 Evaluate @var{expr} as an expression. The expression could contain an
30750 inferior function call. The function call will execute synchronously.
30751 If the expression contains spaces, it must be enclosed in double quotes.
30753 @subsubheading @value{GDBN} Command
30755 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30756 @samp{call}. In @code{gdbtk} only, there's a corresponding
30757 @samp{gdb_eval} command.
30759 @subsubheading Example
30761 In the following example, the numbers that precede the commands are the
30762 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30763 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30767 211-data-evaluate-expression A
30770 311-data-evaluate-expression &A
30771 311^done,value="0xefffeb7c"
30773 411-data-evaluate-expression A+3
30776 511-data-evaluate-expression "A + 3"
30782 @subheading The @code{-data-list-changed-registers} Command
30783 @findex -data-list-changed-registers
30785 @subsubheading Synopsis
30788 -data-list-changed-registers
30791 Display a list of the registers that have changed.
30793 @subsubheading @value{GDBN} Command
30795 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30796 has the corresponding command @samp{gdb_changed_register_list}.
30798 @subsubheading Example
30800 On a PPC MBX board:
30808 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30809 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30812 -data-list-changed-registers
30813 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30814 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30815 "24","25","26","27","28","30","31","64","65","66","67","69"]
30820 @subheading The @code{-data-list-register-names} Command
30821 @findex -data-list-register-names
30823 @subsubheading Synopsis
30826 -data-list-register-names [ ( @var{regno} )+ ]
30829 Show a list of register names for the current target. If no arguments
30830 are given, it shows a list of the names of all the registers. If
30831 integer numbers are given as arguments, it will print a list of the
30832 names of the registers corresponding to the arguments. To ensure
30833 consistency between a register name and its number, the output list may
30834 include empty register names.
30836 @subsubheading @value{GDBN} Command
30838 @value{GDBN} does not have a command which corresponds to
30839 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30840 corresponding command @samp{gdb_regnames}.
30842 @subsubheading Example
30844 For the PPC MBX board:
30847 -data-list-register-names
30848 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30849 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30850 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30851 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30852 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30853 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30854 "", "pc","ps","cr","lr","ctr","xer"]
30856 -data-list-register-names 1 2 3
30857 ^done,register-names=["r1","r2","r3"]
30861 @subheading The @code{-data-list-register-values} Command
30862 @findex -data-list-register-values
30864 @subsubheading Synopsis
30867 -data-list-register-values
30868 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
30871 Display the registers' contents. The format according to which the
30872 registers' contents are to be returned is given by @var{fmt}, followed
30873 by an optional list of numbers specifying the registers to display. A
30874 missing list of numbers indicates that the contents of all the
30875 registers must be returned. The @code{--skip-unavailable} option
30876 indicates that only the available registers are to be returned.
30878 Allowed formats for @var{fmt} are:
30895 @subsubheading @value{GDBN} Command
30897 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30898 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30900 @subsubheading Example
30902 For a PPC MBX board (note: line breaks are for readability only, they
30903 don't appear in the actual output):
30907 -data-list-register-values r 64 65
30908 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30909 @{number="65",value="0x00029002"@}]
30911 -data-list-register-values x
30912 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30913 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30914 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30915 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30916 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30917 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30918 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30919 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30920 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30921 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30922 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30923 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30924 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30925 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30926 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30927 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30928 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30929 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30930 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30931 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30932 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30933 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30934 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30935 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30936 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30937 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30938 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30939 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30940 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30941 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30942 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30943 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30944 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30945 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30946 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30947 @{number="69",value="0x20002b03"@}]
30952 @subheading The @code{-data-read-memory} Command
30953 @findex -data-read-memory
30955 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30957 @subsubheading Synopsis
30960 -data-read-memory [ -o @var{byte-offset} ]
30961 @var{address} @var{word-format} @var{word-size}
30962 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30969 @item @var{address}
30970 An expression specifying the address of the first memory word to be
30971 read. Complex expressions containing embedded white space should be
30972 quoted using the C convention.
30974 @item @var{word-format}
30975 The format to be used to print the memory words. The notation is the
30976 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30979 @item @var{word-size}
30980 The size of each memory word in bytes.
30982 @item @var{nr-rows}
30983 The number of rows in the output table.
30985 @item @var{nr-cols}
30986 The number of columns in the output table.
30989 If present, indicates that each row should include an @sc{ascii} dump. The
30990 value of @var{aschar} is used as a padding character when a byte is not a
30991 member of the printable @sc{ascii} character set (printable @sc{ascii}
30992 characters are those whose code is between 32 and 126, inclusively).
30994 @item @var{byte-offset}
30995 An offset to add to the @var{address} before fetching memory.
30998 This command displays memory contents as a table of @var{nr-rows} by
30999 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31000 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31001 (returned as @samp{total-bytes}). Should less than the requested number
31002 of bytes be returned by the target, the missing words are identified
31003 using @samp{N/A}. The number of bytes read from the target is returned
31004 in @samp{nr-bytes} and the starting address used to read memory in
31007 The address of the next/previous row or page is available in
31008 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31011 @subsubheading @value{GDBN} Command
31013 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31014 @samp{gdb_get_mem} memory read command.
31016 @subsubheading Example
31018 Read six bytes of memory starting at @code{bytes+6} but then offset by
31019 @code{-6} bytes. Format as three rows of two columns. One byte per
31020 word. Display each word in hex.
31024 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31025 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31026 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31027 prev-page="0x0000138a",memory=[
31028 @{addr="0x00001390",data=["0x00","0x01"]@},
31029 @{addr="0x00001392",data=["0x02","0x03"]@},
31030 @{addr="0x00001394",data=["0x04","0x05"]@}]
31034 Read two bytes of memory starting at address @code{shorts + 64} and
31035 display as a single word formatted in decimal.
31039 5-data-read-memory shorts+64 d 2 1 1
31040 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31041 next-row="0x00001512",prev-row="0x0000150e",
31042 next-page="0x00001512",prev-page="0x0000150e",memory=[
31043 @{addr="0x00001510",data=["128"]@}]
31047 Read thirty two bytes of memory starting at @code{bytes+16} and format
31048 as eight rows of four columns. Include a string encoding with @samp{x}
31049 used as the non-printable character.
31053 4-data-read-memory bytes+16 x 1 8 4 x
31054 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31055 next-row="0x000013c0",prev-row="0x0000139c",
31056 next-page="0x000013c0",prev-page="0x00001380",memory=[
31057 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31058 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31059 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31060 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31061 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31062 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31063 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31064 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31068 @subheading The @code{-data-read-memory-bytes} Command
31069 @findex -data-read-memory-bytes
31071 @subsubheading Synopsis
31074 -data-read-memory-bytes [ -o @var{offset} ]
31075 @var{address} @var{count}
31082 @item @var{address}
31083 An expression specifying the address of the first addressable memory unit
31084 to be read. Complex expressions containing embedded white space should be
31085 quoted using the C convention.
31088 The number of addressable memory units to read. This should be an integer
31092 The offset relative to @var{address} at which to start reading. This
31093 should be an integer literal. This option is provided so that a frontend
31094 is not required to first evaluate address and then perform address
31095 arithmetics itself.
31099 This command attempts to read all accessible memory regions in the
31100 specified range. First, all regions marked as unreadable in the memory
31101 map (if one is defined) will be skipped. @xref{Memory Region
31102 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31103 regions. For each one, if reading full region results in an errors,
31104 @value{GDBN} will try to read a subset of the region.
31106 In general, every single memory unit in the region may be readable or not,
31107 and the only way to read every readable unit is to try a read at
31108 every address, which is not practical. Therefore, @value{GDBN} will
31109 attempt to read all accessible memory units at either beginning or the end
31110 of the region, using a binary division scheme. This heuristic works
31111 well for reading accross a memory map boundary. Note that if a region
31112 has a readable range that is neither at the beginning or the end,
31113 @value{GDBN} will not read it.
31115 The result record (@pxref{GDB/MI Result Records}) that is output of
31116 the command includes a field named @samp{memory} whose content is a
31117 list of tuples. Each tuple represent a successfully read memory block
31118 and has the following fields:
31122 The start address of the memory block, as hexadecimal literal.
31125 The end address of the memory block, as hexadecimal literal.
31128 The offset of the memory block, as hexadecimal literal, relative to
31129 the start address passed to @code{-data-read-memory-bytes}.
31132 The contents of the memory block, in hex.
31138 @subsubheading @value{GDBN} Command
31140 The corresponding @value{GDBN} command is @samp{x}.
31142 @subsubheading Example
31146 -data-read-memory-bytes &a 10
31147 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31149 contents="01000000020000000300"@}]
31154 @subheading The @code{-data-write-memory-bytes} Command
31155 @findex -data-write-memory-bytes
31157 @subsubheading Synopsis
31160 -data-write-memory-bytes @var{address} @var{contents}
31161 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31168 @item @var{address}
31169 An expression specifying the address of the first addressable memory unit
31170 to be written. Complex expressions containing embedded white space should
31171 be quoted using the C convention.
31173 @item @var{contents}
31174 The hex-encoded data to write. It is an error if @var{contents} does
31175 not represent an integral number of addressable memory units.
31178 Optional argument indicating the number of addressable memory units to be
31179 written. If @var{count} is greater than @var{contents}' length,
31180 @value{GDBN} will repeatedly write @var{contents} until it fills
31181 @var{count} memory units.
31185 @subsubheading @value{GDBN} Command
31187 There's no corresponding @value{GDBN} command.
31189 @subsubheading Example
31193 -data-write-memory-bytes &a "aabbccdd"
31200 -data-write-memory-bytes &a "aabbccdd" 16e
31205 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31206 @node GDB/MI Tracepoint Commands
31207 @section @sc{gdb/mi} Tracepoint Commands
31209 The commands defined in this section implement MI support for
31210 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31212 @subheading The @code{-trace-find} Command
31213 @findex -trace-find
31215 @subsubheading Synopsis
31218 -trace-find @var{mode} [@var{parameters}@dots{}]
31221 Find a trace frame using criteria defined by @var{mode} and
31222 @var{parameters}. The following table lists permissible
31223 modes and their parameters. For details of operation, see @ref{tfind}.
31228 No parameters are required. Stops examining trace frames.
31231 An integer is required as parameter. Selects tracepoint frame with
31234 @item tracepoint-number
31235 An integer is required as parameter. Finds next
31236 trace frame that corresponds to tracepoint with the specified number.
31239 An address is required as parameter. Finds
31240 next trace frame that corresponds to any tracepoint at the specified
31243 @item pc-inside-range
31244 Two addresses are required as parameters. Finds next trace
31245 frame that corresponds to a tracepoint at an address inside the
31246 specified range. Both bounds are considered to be inside the range.
31248 @item pc-outside-range
31249 Two addresses are required as parameters. Finds
31250 next trace frame that corresponds to a tracepoint at an address outside
31251 the specified range. Both bounds are considered to be inside the range.
31254 Line specification is required as parameter. @xref{Specify Location}.
31255 Finds next trace frame that corresponds to a tracepoint at
31256 the specified location.
31260 If @samp{none} was passed as @var{mode}, the response does not
31261 have fields. Otherwise, the response may have the following fields:
31265 This field has either @samp{0} or @samp{1} as the value, depending
31266 on whether a matching tracepoint was found.
31269 The index of the found traceframe. This field is present iff
31270 the @samp{found} field has value of @samp{1}.
31273 The index of the found tracepoint. This field is present iff
31274 the @samp{found} field has value of @samp{1}.
31277 The information about the frame corresponding to the found trace
31278 frame. This field is present only if a trace frame was found.
31279 @xref{GDB/MI Frame Information}, for description of this field.
31283 @subsubheading @value{GDBN} Command
31285 The corresponding @value{GDBN} command is @samp{tfind}.
31287 @subheading -trace-define-variable
31288 @findex -trace-define-variable
31290 @subsubheading Synopsis
31293 -trace-define-variable @var{name} [ @var{value} ]
31296 Create trace variable @var{name} if it does not exist. If
31297 @var{value} is specified, sets the initial value of the specified
31298 trace variable to that value. Note that the @var{name} should start
31299 with the @samp{$} character.
31301 @subsubheading @value{GDBN} Command
31303 The corresponding @value{GDBN} command is @samp{tvariable}.
31305 @subheading The @code{-trace-frame-collected} Command
31306 @findex -trace-frame-collected
31308 @subsubheading Synopsis
31311 -trace-frame-collected
31312 [--var-print-values @var{var_pval}]
31313 [--comp-print-values @var{comp_pval}]
31314 [--registers-format @var{regformat}]
31315 [--memory-contents]
31318 This command returns the set of collected objects, register names,
31319 trace state variable names, memory ranges and computed expressions
31320 that have been collected at a particular trace frame. The optional
31321 parameters to the command affect the output format in different ways.
31322 See the output description table below for more details.
31324 The reported names can be used in the normal manner to create
31325 varobjs and inspect the objects themselves. The items returned by
31326 this command are categorized so that it is clear which is a variable,
31327 which is a register, which is a trace state variable, which is a
31328 memory range and which is a computed expression.
31330 For instance, if the actions were
31332 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
31333 collect *(int*)0xaf02bef0@@40
31337 the object collected in its entirety would be @code{myVar}. The
31338 object @code{myArray} would be partially collected, because only the
31339 element at index @code{myIndex} would be collected. The remaining
31340 objects would be computed expressions.
31342 An example output would be:
31346 -trace-frame-collected
31348 explicit-variables=[@{name="myVar",value="1"@}],
31349 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
31350 @{name="myObj.field",value="0"@},
31351 @{name="myPtr->field",value="1"@},
31352 @{name="myCount + 2",value="3"@},
31353 @{name="$tvar1 + 1",value="43970027"@}],
31354 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
31355 @{number="1",value="0x0"@},
31356 @{number="2",value="0x4"@},
31358 @{number="125",value="0x0"@}],
31359 tvars=[@{name="$tvar1",current="43970026"@}],
31360 memory=[@{address="0x0000000000602264",length="4"@},
31361 @{address="0x0000000000615bc0",length="4"@}]
31368 @item explicit-variables
31369 The set of objects that have been collected in their entirety (as
31370 opposed to collecting just a few elements of an array or a few struct
31371 members). For each object, its name and value are printed.
31372 The @code{--var-print-values} option affects how or whether the value
31373 field is output. If @var{var_pval} is 0, then print only the names;
31374 if it is 1, print also their values; and if it is 2, print the name,
31375 type and value for simple data types, and the name and type for
31376 arrays, structures and unions.
31378 @item computed-expressions
31379 The set of computed expressions that have been collected at the
31380 current trace frame. The @code{--comp-print-values} option affects
31381 this set like the @code{--var-print-values} option affects the
31382 @code{explicit-variables} set. See above.
31385 The registers that have been collected at the current trace frame.
31386 For each register collected, the name and current value are returned.
31387 The value is formatted according to the @code{--registers-format}
31388 option. See the @command{-data-list-register-values} command for a
31389 list of the allowed formats. The default is @samp{x}.
31392 The trace state variables that have been collected at the current
31393 trace frame. For each trace state variable collected, the name and
31394 current value are returned.
31397 The set of memory ranges that have been collected at the current trace
31398 frame. Its content is a list of tuples. Each tuple represents a
31399 collected memory range and has the following fields:
31403 The start address of the memory range, as hexadecimal literal.
31406 The length of the memory range, as decimal literal.
31409 The contents of the memory block, in hex. This field is only present
31410 if the @code{--memory-contents} option is specified.
31416 @subsubheading @value{GDBN} Command
31418 There is no corresponding @value{GDBN} command.
31420 @subsubheading Example
31422 @subheading -trace-list-variables
31423 @findex -trace-list-variables
31425 @subsubheading Synopsis
31428 -trace-list-variables
31431 Return a table of all defined trace variables. Each element of the
31432 table has the following fields:
31436 The name of the trace variable. This field is always present.
31439 The initial value. This is a 64-bit signed integer. This
31440 field is always present.
31443 The value the trace variable has at the moment. This is a 64-bit
31444 signed integer. This field is absent iff current value is
31445 not defined, for example if the trace was never run, or is
31450 @subsubheading @value{GDBN} Command
31452 The corresponding @value{GDBN} command is @samp{tvariables}.
31454 @subsubheading Example
31458 -trace-list-variables
31459 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31460 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31461 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31462 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31463 body=[variable=@{name="$trace_timestamp",initial="0"@}
31464 variable=@{name="$foo",initial="10",current="15"@}]@}
31468 @subheading -trace-save
31469 @findex -trace-save
31471 @subsubheading Synopsis
31474 -trace-save [ -r ] [ -ctf ] @var{filename}
31477 Saves the collected trace data to @var{filename}. Without the
31478 @samp{-r} option, the data is downloaded from the target and saved
31479 in a local file. With the @samp{-r} option the target is asked
31480 to perform the save.
31482 By default, this command will save the trace in the tfile format. You can
31483 supply the optional @samp{-ctf} argument to save it the CTF format. See
31484 @ref{Trace Files} for more information about CTF.
31486 @subsubheading @value{GDBN} Command
31488 The corresponding @value{GDBN} command is @samp{tsave}.
31491 @subheading -trace-start
31492 @findex -trace-start
31494 @subsubheading Synopsis
31500 Starts a tracing experiment. The result of this command does not
31503 @subsubheading @value{GDBN} Command
31505 The corresponding @value{GDBN} command is @samp{tstart}.
31507 @subheading -trace-status
31508 @findex -trace-status
31510 @subsubheading Synopsis
31516 Obtains the status of a tracing experiment. The result may include
31517 the following fields:
31522 May have a value of either @samp{0}, when no tracing operations are
31523 supported, @samp{1}, when all tracing operations are supported, or
31524 @samp{file} when examining trace file. In the latter case, examining
31525 of trace frame is possible but new tracing experiement cannot be
31526 started. This field is always present.
31529 May have a value of either @samp{0} or @samp{1} depending on whether
31530 tracing experiement is in progress on target. This field is present
31531 if @samp{supported} field is not @samp{0}.
31534 Report the reason why the tracing was stopped last time. This field
31535 may be absent iff tracing was never stopped on target yet. The
31536 value of @samp{request} means the tracing was stopped as result of
31537 the @code{-trace-stop} command. The value of @samp{overflow} means
31538 the tracing buffer is full. The value of @samp{disconnection} means
31539 tracing was automatically stopped when @value{GDBN} has disconnected.
31540 The value of @samp{passcount} means tracing was stopped when a
31541 tracepoint was passed a maximal number of times for that tracepoint.
31542 This field is present if @samp{supported} field is not @samp{0}.
31544 @item stopping-tracepoint
31545 The number of tracepoint whose passcount as exceeded. This field is
31546 present iff the @samp{stop-reason} field has the value of
31550 @itemx frames-created
31551 The @samp{frames} field is a count of the total number of trace frames
31552 in the trace buffer, while @samp{frames-created} is the total created
31553 during the run, including ones that were discarded, such as when a
31554 circular trace buffer filled up. Both fields are optional.
31558 These fields tell the current size of the tracing buffer and the
31559 remaining space. These fields are optional.
31562 The value of the circular trace buffer flag. @code{1} means that the
31563 trace buffer is circular and old trace frames will be discarded if
31564 necessary to make room, @code{0} means that the trace buffer is linear
31568 The value of the disconnected tracing flag. @code{1} means that
31569 tracing will continue after @value{GDBN} disconnects, @code{0} means
31570 that the trace run will stop.
31573 The filename of the trace file being examined. This field is
31574 optional, and only present when examining a trace file.
31578 @subsubheading @value{GDBN} Command
31580 The corresponding @value{GDBN} command is @samp{tstatus}.
31582 @subheading -trace-stop
31583 @findex -trace-stop
31585 @subsubheading Synopsis
31591 Stops a tracing experiment. The result of this command has the same
31592 fields as @code{-trace-status}, except that the @samp{supported} and
31593 @samp{running} fields are not output.
31595 @subsubheading @value{GDBN} Command
31597 The corresponding @value{GDBN} command is @samp{tstop}.
31600 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31601 @node GDB/MI Symbol Query
31602 @section @sc{gdb/mi} Symbol Query Commands
31606 @subheading The @code{-symbol-info-address} Command
31607 @findex -symbol-info-address
31609 @subsubheading Synopsis
31612 -symbol-info-address @var{symbol}
31615 Describe where @var{symbol} is stored.
31617 @subsubheading @value{GDBN} Command
31619 The corresponding @value{GDBN} command is @samp{info address}.
31621 @subsubheading Example
31625 @subheading The @code{-symbol-info-file} Command
31626 @findex -symbol-info-file
31628 @subsubheading Synopsis
31634 Show the file for the symbol.
31636 @subsubheading @value{GDBN} Command
31638 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31639 @samp{gdb_find_file}.
31641 @subsubheading Example
31645 @subheading The @code{-symbol-info-function} Command
31646 @findex -symbol-info-function
31648 @subsubheading Synopsis
31651 -symbol-info-function
31654 Show which function the symbol lives in.
31656 @subsubheading @value{GDBN} Command
31658 @samp{gdb_get_function} in @code{gdbtk}.
31660 @subsubheading Example
31664 @subheading The @code{-symbol-info-line} Command
31665 @findex -symbol-info-line
31667 @subsubheading Synopsis
31673 Show the core addresses of the code for a source line.
31675 @subsubheading @value{GDBN} Command
31677 The corresponding @value{GDBN} command is @samp{info line}.
31678 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31680 @subsubheading Example
31684 @subheading The @code{-symbol-info-symbol} Command
31685 @findex -symbol-info-symbol
31687 @subsubheading Synopsis
31690 -symbol-info-symbol @var{addr}
31693 Describe what symbol is at location @var{addr}.
31695 @subsubheading @value{GDBN} Command
31697 The corresponding @value{GDBN} command is @samp{info symbol}.
31699 @subsubheading Example
31703 @subheading The @code{-symbol-list-functions} Command
31704 @findex -symbol-list-functions
31706 @subsubheading Synopsis
31709 -symbol-list-functions
31712 List the functions in the executable.
31714 @subsubheading @value{GDBN} Command
31716 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31717 @samp{gdb_search} in @code{gdbtk}.
31719 @subsubheading Example
31724 @subheading The @code{-symbol-list-lines} Command
31725 @findex -symbol-list-lines
31727 @subsubheading Synopsis
31730 -symbol-list-lines @var{filename}
31733 Print the list of lines that contain code and their associated program
31734 addresses for the given source filename. The entries are sorted in
31735 ascending PC order.
31737 @subsubheading @value{GDBN} Command
31739 There is no corresponding @value{GDBN} command.
31741 @subsubheading Example
31744 -symbol-list-lines basics.c
31745 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31751 @subheading The @code{-symbol-list-types} Command
31752 @findex -symbol-list-types
31754 @subsubheading Synopsis
31760 List all the type names.
31762 @subsubheading @value{GDBN} Command
31764 The corresponding commands are @samp{info types} in @value{GDBN},
31765 @samp{gdb_search} in @code{gdbtk}.
31767 @subsubheading Example
31771 @subheading The @code{-symbol-list-variables} Command
31772 @findex -symbol-list-variables
31774 @subsubheading Synopsis
31777 -symbol-list-variables
31780 List all the global and static variable names.
31782 @subsubheading @value{GDBN} Command
31784 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31786 @subsubheading Example
31790 @subheading The @code{-symbol-locate} Command
31791 @findex -symbol-locate
31793 @subsubheading Synopsis
31799 @subsubheading @value{GDBN} Command
31801 @samp{gdb_loc} in @code{gdbtk}.
31803 @subsubheading Example
31807 @subheading The @code{-symbol-type} Command
31808 @findex -symbol-type
31810 @subsubheading Synopsis
31813 -symbol-type @var{variable}
31816 Show type of @var{variable}.
31818 @subsubheading @value{GDBN} Command
31820 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31821 @samp{gdb_obj_variable}.
31823 @subsubheading Example
31828 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31829 @node GDB/MI File Commands
31830 @section @sc{gdb/mi} File Commands
31832 This section describes the GDB/MI commands to specify executable file names
31833 and to read in and obtain symbol table information.
31835 @subheading The @code{-file-exec-and-symbols} Command
31836 @findex -file-exec-and-symbols
31838 @subsubheading Synopsis
31841 -file-exec-and-symbols @var{file}
31844 Specify the executable file to be debugged. This file is the one from
31845 which the symbol table is also read. If no file is specified, the
31846 command clears the executable and symbol information. If breakpoints
31847 are set when using this command with no arguments, @value{GDBN} will produce
31848 error messages. Otherwise, no output is produced, except a completion
31851 @subsubheading @value{GDBN} Command
31853 The corresponding @value{GDBN} command is @samp{file}.
31855 @subsubheading Example
31859 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31865 @subheading The @code{-file-exec-file} Command
31866 @findex -file-exec-file
31868 @subsubheading Synopsis
31871 -file-exec-file @var{file}
31874 Specify the executable file to be debugged. Unlike
31875 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31876 from this file. If used without argument, @value{GDBN} clears the information
31877 about the executable file. No output is produced, except a completion
31880 @subsubheading @value{GDBN} Command
31882 The corresponding @value{GDBN} command is @samp{exec-file}.
31884 @subsubheading Example
31888 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31895 @subheading The @code{-file-list-exec-sections} Command
31896 @findex -file-list-exec-sections
31898 @subsubheading Synopsis
31901 -file-list-exec-sections
31904 List the sections of the current executable file.
31906 @subsubheading @value{GDBN} Command
31908 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31909 information as this command. @code{gdbtk} has a corresponding command
31910 @samp{gdb_load_info}.
31912 @subsubheading Example
31917 @subheading The @code{-file-list-exec-source-file} Command
31918 @findex -file-list-exec-source-file
31920 @subsubheading Synopsis
31923 -file-list-exec-source-file
31926 List the line number, the current source file, and the absolute path
31927 to the current source file for the current executable. The macro
31928 information field has a value of @samp{1} or @samp{0} depending on
31929 whether or not the file includes preprocessor macro information.
31931 @subsubheading @value{GDBN} Command
31933 The @value{GDBN} equivalent is @samp{info source}
31935 @subsubheading Example
31939 123-file-list-exec-source-file
31940 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31945 @subheading The @code{-file-list-exec-source-files} Command
31946 @findex -file-list-exec-source-files
31948 @subsubheading Synopsis
31951 -file-list-exec-source-files
31954 List the source files for the current executable.
31956 It will always output both the filename and fullname (absolute file
31957 name) of a source file.
31959 @subsubheading @value{GDBN} Command
31961 The @value{GDBN} equivalent is @samp{info sources}.
31962 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31964 @subsubheading Example
31967 -file-list-exec-source-files
31969 @{file=foo.c,fullname=/home/foo.c@},
31970 @{file=/home/bar.c,fullname=/home/bar.c@},
31971 @{file=gdb_could_not_find_fullpath.c@}]
31975 @subheading The @code{-file-list-shared-libraries} Command
31976 @findex -file-list-shared-libraries
31978 @subsubheading Synopsis
31981 -file-list-shared-libraries [ @var{regexp} ]
31984 List the shared libraries in the program.
31985 With a regular expression @var{regexp}, only those libraries whose
31986 names match @var{regexp} are listed.
31988 @subsubheading @value{GDBN} Command
31990 The corresponding @value{GDBN} command is @samp{info shared}. The fields
31991 have a similar meaning to the @code{=library-loaded} notification.
31992 The @code{ranges} field specifies the multiple segments belonging to this
31993 library. Each range has the following fields:
31997 The address defining the inclusive lower bound of the segment.
31999 The address defining the exclusive upper bound of the segment.
32002 @subsubheading Example
32005 -file-list-exec-source-files
32006 ^done,shared-libraries=[
32007 @{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"@}]@},
32008 @{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"@}]@}]
32014 @subheading The @code{-file-list-symbol-files} Command
32015 @findex -file-list-symbol-files
32017 @subsubheading Synopsis
32020 -file-list-symbol-files
32025 @subsubheading @value{GDBN} Command
32027 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32029 @subsubheading Example
32034 @subheading The @code{-file-symbol-file} Command
32035 @findex -file-symbol-file
32037 @subsubheading Synopsis
32040 -file-symbol-file @var{file}
32043 Read symbol table info from the specified @var{file} argument. When
32044 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32045 produced, except for a completion notification.
32047 @subsubheading @value{GDBN} Command
32049 The corresponding @value{GDBN} command is @samp{symbol-file}.
32051 @subsubheading Example
32055 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32061 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32062 @node GDB/MI Memory Overlay Commands
32063 @section @sc{gdb/mi} Memory Overlay Commands
32065 The memory overlay commands are not implemented.
32067 @c @subheading -overlay-auto
32069 @c @subheading -overlay-list-mapping-state
32071 @c @subheading -overlay-list-overlays
32073 @c @subheading -overlay-map
32075 @c @subheading -overlay-off
32077 @c @subheading -overlay-on
32079 @c @subheading -overlay-unmap
32081 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32082 @node GDB/MI Signal Handling Commands
32083 @section @sc{gdb/mi} Signal Handling Commands
32085 Signal handling commands are not implemented.
32087 @c @subheading -signal-handle
32089 @c @subheading -signal-list-handle-actions
32091 @c @subheading -signal-list-signal-types
32095 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32096 @node GDB/MI Target Manipulation
32097 @section @sc{gdb/mi} Target Manipulation Commands
32100 @subheading The @code{-target-attach} Command
32101 @findex -target-attach
32103 @subsubheading Synopsis
32106 -target-attach @var{pid} | @var{gid} | @var{file}
32109 Attach to a process @var{pid} or a file @var{file} outside of
32110 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32111 group, the id previously returned by
32112 @samp{-list-thread-groups --available} must be used.
32114 @subsubheading @value{GDBN} Command
32116 The corresponding @value{GDBN} command is @samp{attach}.
32118 @subsubheading Example
32122 =thread-created,id="1"
32123 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32129 @subheading The @code{-target-compare-sections} Command
32130 @findex -target-compare-sections
32132 @subsubheading Synopsis
32135 -target-compare-sections [ @var{section} ]
32138 Compare data of section @var{section} on target to the exec file.
32139 Without the argument, all sections are compared.
32141 @subsubheading @value{GDBN} Command
32143 The @value{GDBN} equivalent is @samp{compare-sections}.
32145 @subsubheading Example
32150 @subheading The @code{-target-detach} Command
32151 @findex -target-detach
32153 @subsubheading Synopsis
32156 -target-detach [ @var{pid} | @var{gid} ]
32159 Detach from the remote target which normally resumes its execution.
32160 If either @var{pid} or @var{gid} is specified, detaches from either
32161 the specified process, or specified thread group. There's no output.
32163 @subsubheading @value{GDBN} Command
32165 The corresponding @value{GDBN} command is @samp{detach}.
32167 @subsubheading Example
32177 @subheading The @code{-target-disconnect} Command
32178 @findex -target-disconnect
32180 @subsubheading Synopsis
32186 Disconnect from the remote target. There's no output and the target is
32187 generally not resumed.
32189 @subsubheading @value{GDBN} Command
32191 The corresponding @value{GDBN} command is @samp{disconnect}.
32193 @subsubheading Example
32203 @subheading The @code{-target-download} Command
32204 @findex -target-download
32206 @subsubheading Synopsis
32212 Loads the executable onto the remote target.
32213 It prints out an update message every half second, which includes the fields:
32217 The name of the section.
32219 The size of what has been sent so far for that section.
32221 The size of the section.
32223 The total size of what was sent so far (the current and the previous sections).
32225 The size of the overall executable to download.
32229 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32230 @sc{gdb/mi} Output Syntax}).
32232 In addition, it prints the name and size of the sections, as they are
32233 downloaded. These messages include the following fields:
32237 The name of the section.
32239 The size of the section.
32241 The size of the overall executable to download.
32245 At the end, a summary is printed.
32247 @subsubheading @value{GDBN} Command
32249 The corresponding @value{GDBN} command is @samp{load}.
32251 @subsubheading Example
32253 Note: each status message appears on a single line. Here the messages
32254 have been broken down so that they can fit onto a page.
32259 +download,@{section=".text",section-size="6668",total-size="9880"@}
32260 +download,@{section=".text",section-sent="512",section-size="6668",
32261 total-sent="512",total-size="9880"@}
32262 +download,@{section=".text",section-sent="1024",section-size="6668",
32263 total-sent="1024",total-size="9880"@}
32264 +download,@{section=".text",section-sent="1536",section-size="6668",
32265 total-sent="1536",total-size="9880"@}
32266 +download,@{section=".text",section-sent="2048",section-size="6668",
32267 total-sent="2048",total-size="9880"@}
32268 +download,@{section=".text",section-sent="2560",section-size="6668",
32269 total-sent="2560",total-size="9880"@}
32270 +download,@{section=".text",section-sent="3072",section-size="6668",
32271 total-sent="3072",total-size="9880"@}
32272 +download,@{section=".text",section-sent="3584",section-size="6668",
32273 total-sent="3584",total-size="9880"@}
32274 +download,@{section=".text",section-sent="4096",section-size="6668",
32275 total-sent="4096",total-size="9880"@}
32276 +download,@{section=".text",section-sent="4608",section-size="6668",
32277 total-sent="4608",total-size="9880"@}
32278 +download,@{section=".text",section-sent="5120",section-size="6668",
32279 total-sent="5120",total-size="9880"@}
32280 +download,@{section=".text",section-sent="5632",section-size="6668",
32281 total-sent="5632",total-size="9880"@}
32282 +download,@{section=".text",section-sent="6144",section-size="6668",
32283 total-sent="6144",total-size="9880"@}
32284 +download,@{section=".text",section-sent="6656",section-size="6668",
32285 total-sent="6656",total-size="9880"@}
32286 +download,@{section=".init",section-size="28",total-size="9880"@}
32287 +download,@{section=".fini",section-size="28",total-size="9880"@}
32288 +download,@{section=".data",section-size="3156",total-size="9880"@}
32289 +download,@{section=".data",section-sent="512",section-size="3156",
32290 total-sent="7236",total-size="9880"@}
32291 +download,@{section=".data",section-sent="1024",section-size="3156",
32292 total-sent="7748",total-size="9880"@}
32293 +download,@{section=".data",section-sent="1536",section-size="3156",
32294 total-sent="8260",total-size="9880"@}
32295 +download,@{section=".data",section-sent="2048",section-size="3156",
32296 total-sent="8772",total-size="9880"@}
32297 +download,@{section=".data",section-sent="2560",section-size="3156",
32298 total-sent="9284",total-size="9880"@}
32299 +download,@{section=".data",section-sent="3072",section-size="3156",
32300 total-sent="9796",total-size="9880"@}
32301 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32308 @subheading The @code{-target-exec-status} Command
32309 @findex -target-exec-status
32311 @subsubheading Synopsis
32314 -target-exec-status
32317 Provide information on the state of the target (whether it is running or
32318 not, for instance).
32320 @subsubheading @value{GDBN} Command
32322 There's no equivalent @value{GDBN} command.
32324 @subsubheading Example
32328 @subheading The @code{-target-list-available-targets} Command
32329 @findex -target-list-available-targets
32331 @subsubheading Synopsis
32334 -target-list-available-targets
32337 List the possible targets to connect to.
32339 @subsubheading @value{GDBN} Command
32341 The corresponding @value{GDBN} command is @samp{help target}.
32343 @subsubheading Example
32347 @subheading The @code{-target-list-current-targets} Command
32348 @findex -target-list-current-targets
32350 @subsubheading Synopsis
32353 -target-list-current-targets
32356 Describe the current target.
32358 @subsubheading @value{GDBN} Command
32360 The corresponding information is printed by @samp{info file} (among
32363 @subsubheading Example
32367 @subheading The @code{-target-list-parameters} Command
32368 @findex -target-list-parameters
32370 @subsubheading Synopsis
32373 -target-list-parameters
32379 @subsubheading @value{GDBN} Command
32383 @subsubheading Example
32386 @subheading The @code{-target-flash-erase} Command
32387 @findex -target-flash-erase
32389 @subsubheading Synopsis
32392 -target-flash-erase
32395 Erases all known flash memory regions on the target.
32397 The corresponding @value{GDBN} command is @samp{flash-erase}.
32399 The output is a list of flash regions that have been erased, with starting
32400 addresses and memory region sizes.
32404 -target-flash-erase
32405 ^done,erased-regions=@{address="0x0",size="0x40000"@}
32409 @subheading The @code{-target-select} Command
32410 @findex -target-select
32412 @subsubheading Synopsis
32415 -target-select @var{type} @var{parameters @dots{}}
32418 Connect @value{GDBN} to the remote target. This command takes two args:
32422 The type of target, for instance @samp{remote}, etc.
32423 @item @var{parameters}
32424 Device names, host names and the like. @xref{Target Commands, ,
32425 Commands for Managing Targets}, for more details.
32428 The output is a connection notification, followed by the address at
32429 which the target program is, in the following form:
32432 ^connected,addr="@var{address}",func="@var{function name}",
32433 args=[@var{arg list}]
32436 @subsubheading @value{GDBN} Command
32438 The corresponding @value{GDBN} command is @samp{target}.
32440 @subsubheading Example
32444 -target-select remote /dev/ttya
32445 ^connected,addr="0xfe00a300",func="??",args=[]
32449 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32450 @node GDB/MI File Transfer Commands
32451 @section @sc{gdb/mi} File Transfer Commands
32454 @subheading The @code{-target-file-put} Command
32455 @findex -target-file-put
32457 @subsubheading Synopsis
32460 -target-file-put @var{hostfile} @var{targetfile}
32463 Copy file @var{hostfile} from the host system (the machine running
32464 @value{GDBN}) to @var{targetfile} on the target system.
32466 @subsubheading @value{GDBN} Command
32468 The corresponding @value{GDBN} command is @samp{remote put}.
32470 @subsubheading Example
32474 -target-file-put localfile remotefile
32480 @subheading The @code{-target-file-get} Command
32481 @findex -target-file-get
32483 @subsubheading Synopsis
32486 -target-file-get @var{targetfile} @var{hostfile}
32489 Copy file @var{targetfile} from the target system to @var{hostfile}
32490 on the host system.
32492 @subsubheading @value{GDBN} Command
32494 The corresponding @value{GDBN} command is @samp{remote get}.
32496 @subsubheading Example
32500 -target-file-get remotefile localfile
32506 @subheading The @code{-target-file-delete} Command
32507 @findex -target-file-delete
32509 @subsubheading Synopsis
32512 -target-file-delete @var{targetfile}
32515 Delete @var{targetfile} from the target system.
32517 @subsubheading @value{GDBN} Command
32519 The corresponding @value{GDBN} command is @samp{remote delete}.
32521 @subsubheading Example
32525 -target-file-delete remotefile
32531 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32532 @node GDB/MI Ada Exceptions Commands
32533 @section Ada Exceptions @sc{gdb/mi} Commands
32535 @subheading The @code{-info-ada-exceptions} Command
32536 @findex -info-ada-exceptions
32538 @subsubheading Synopsis
32541 -info-ada-exceptions [ @var{regexp}]
32544 List all Ada exceptions defined within the program being debugged.
32545 With a regular expression @var{regexp}, only those exceptions whose
32546 names match @var{regexp} are listed.
32548 @subsubheading @value{GDBN} Command
32550 The corresponding @value{GDBN} command is @samp{info exceptions}.
32552 @subsubheading Result
32554 The result is a table of Ada exceptions. The following columns are
32555 defined for each exception:
32559 The name of the exception.
32562 The address of the exception.
32566 @subsubheading Example
32569 -info-ada-exceptions aint
32570 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
32571 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
32572 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
32573 body=[@{name="constraint_error",address="0x0000000000613da0"@},
32574 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
32577 @subheading Catching Ada Exceptions
32579 The commands describing how to ask @value{GDBN} to stop when a program
32580 raises an exception are described at @ref{Ada Exception GDB/MI
32581 Catchpoint Commands}.
32584 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32585 @node GDB/MI Support Commands
32586 @section @sc{gdb/mi} Support Commands
32588 Since new commands and features get regularly added to @sc{gdb/mi},
32589 some commands are available to help front-ends query the debugger
32590 about support for these capabilities. Similarly, it is also possible
32591 to query @value{GDBN} about target support of certain features.
32593 @subheading The @code{-info-gdb-mi-command} Command
32594 @cindex @code{-info-gdb-mi-command}
32595 @findex -info-gdb-mi-command
32597 @subsubheading Synopsis
32600 -info-gdb-mi-command @var{cmd_name}
32603 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
32605 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
32606 is technically not part of the command name (@pxref{GDB/MI Input
32607 Syntax}), and thus should be omitted in @var{cmd_name}. However,
32608 for ease of use, this command also accepts the form with the leading
32611 @subsubheading @value{GDBN} Command
32613 There is no corresponding @value{GDBN} command.
32615 @subsubheading Result
32617 The result is a tuple. There is currently only one field:
32621 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
32622 @code{"false"} otherwise.
32626 @subsubheading Example
32628 Here is an example where the @sc{gdb/mi} command does not exist:
32631 -info-gdb-mi-command unsupported-command
32632 ^done,command=@{exists="false"@}
32636 And here is an example where the @sc{gdb/mi} command is known
32640 -info-gdb-mi-command symbol-list-lines
32641 ^done,command=@{exists="true"@}
32644 @subheading The @code{-list-features} Command
32645 @findex -list-features
32646 @cindex supported @sc{gdb/mi} features, list
32648 Returns a list of particular features of the MI protocol that
32649 this version of gdb implements. A feature can be a command,
32650 or a new field in an output of some command, or even an
32651 important bugfix. While a frontend can sometimes detect presence
32652 of a feature at runtime, it is easier to perform detection at debugger
32655 The command returns a list of strings, with each string naming an
32656 available feature. Each returned string is just a name, it does not
32657 have any internal structure. The list of possible feature names
32663 (gdb) -list-features
32664 ^done,result=["feature1","feature2"]
32667 The current list of features is:
32670 @item frozen-varobjs
32671 Indicates support for the @code{-var-set-frozen} command, as well
32672 as possible presense of the @code{frozen} field in the output
32673 of @code{-varobj-create}.
32674 @item pending-breakpoints
32675 Indicates support for the @option{-f} option to the @code{-break-insert}
32678 Indicates Python scripting support, Python-based
32679 pretty-printing commands, and possible presence of the
32680 @samp{display_hint} field in the output of @code{-var-list-children}
32682 Indicates support for the @code{-thread-info} command.
32683 @item data-read-memory-bytes
32684 Indicates support for the @code{-data-read-memory-bytes} and the
32685 @code{-data-write-memory-bytes} commands.
32686 @item breakpoint-notifications
32687 Indicates that changes to breakpoints and breakpoints created via the
32688 CLI will be announced via async records.
32689 @item ada-task-info
32690 Indicates support for the @code{-ada-task-info} command.
32691 @item language-option
32692 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
32693 option (@pxref{Context management}).
32694 @item info-gdb-mi-command
32695 Indicates support for the @code{-info-gdb-mi-command} command.
32696 @item undefined-command-error-code
32697 Indicates support for the "undefined-command" error code in error result
32698 records, produced when trying to execute an undefined @sc{gdb/mi} command
32699 (@pxref{GDB/MI Result Records}).
32700 @item exec-run-start-option
32701 Indicates that the @code{-exec-run} command supports the @option{--start}
32702 option (@pxref{GDB/MI Program Execution}).
32705 @subheading The @code{-list-target-features} Command
32706 @findex -list-target-features
32708 Returns a list of particular features that are supported by the
32709 target. Those features affect the permitted MI commands, but
32710 unlike the features reported by the @code{-list-features} command, the
32711 features depend on which target GDB is using at the moment. Whenever
32712 a target can change, due to commands such as @code{-target-select},
32713 @code{-target-attach} or @code{-exec-run}, the list of target features
32714 may change, and the frontend should obtain it again.
32718 (gdb) -list-target-features
32719 ^done,result=["async"]
32722 The current list of features is:
32726 Indicates that the target is capable of asynchronous command
32727 execution, which means that @value{GDBN} will accept further commands
32728 while the target is running.
32731 Indicates that the target is capable of reverse execution.
32732 @xref{Reverse Execution}, for more information.
32736 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32737 @node GDB/MI Miscellaneous Commands
32738 @section Miscellaneous @sc{gdb/mi} Commands
32740 @c @subheading -gdb-complete
32742 @subheading The @code{-gdb-exit} Command
32745 @subsubheading Synopsis
32751 Exit @value{GDBN} immediately.
32753 @subsubheading @value{GDBN} Command
32755 Approximately corresponds to @samp{quit}.
32757 @subsubheading Example
32767 @subheading The @code{-exec-abort} Command
32768 @findex -exec-abort
32770 @subsubheading Synopsis
32776 Kill the inferior running program.
32778 @subsubheading @value{GDBN} Command
32780 The corresponding @value{GDBN} command is @samp{kill}.
32782 @subsubheading Example
32787 @subheading The @code{-gdb-set} Command
32790 @subsubheading Synopsis
32796 Set an internal @value{GDBN} variable.
32797 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32799 @subsubheading @value{GDBN} Command
32801 The corresponding @value{GDBN} command is @samp{set}.
32803 @subsubheading Example
32813 @subheading The @code{-gdb-show} Command
32816 @subsubheading Synopsis
32822 Show the current value of a @value{GDBN} variable.
32824 @subsubheading @value{GDBN} Command
32826 The corresponding @value{GDBN} command is @samp{show}.
32828 @subsubheading Example
32837 @c @subheading -gdb-source
32840 @subheading The @code{-gdb-version} Command
32841 @findex -gdb-version
32843 @subsubheading Synopsis
32849 Show version information for @value{GDBN}. Used mostly in testing.
32851 @subsubheading @value{GDBN} Command
32853 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32854 default shows this information when you start an interactive session.
32856 @subsubheading Example
32858 @c This example modifies the actual output from GDB to avoid overfull
32864 ~Copyright 2000 Free Software Foundation, Inc.
32865 ~GDB is free software, covered by the GNU General Public License, and
32866 ~you are welcome to change it and/or distribute copies of it under
32867 ~ certain conditions.
32868 ~Type "show copying" to see the conditions.
32869 ~There is absolutely no warranty for GDB. Type "show warranty" for
32871 ~This GDB was configured as
32872 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32877 @subheading The @code{-list-thread-groups} Command
32878 @findex -list-thread-groups
32880 @subheading Synopsis
32883 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32886 Lists thread groups (@pxref{Thread groups}). When a single thread
32887 group is passed as the argument, lists the children of that group.
32888 When several thread group are passed, lists information about those
32889 thread groups. Without any parameters, lists information about all
32890 top-level thread groups.
32892 Normally, thread groups that are being debugged are reported.
32893 With the @samp{--available} option, @value{GDBN} reports thread groups
32894 available on the target.
32896 The output of this command may have either a @samp{threads} result or
32897 a @samp{groups} result. The @samp{thread} result has a list of tuples
32898 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32899 Information}). The @samp{groups} result has a list of tuples as value,
32900 each tuple describing a thread group. If top-level groups are
32901 requested (that is, no parameter is passed), or when several groups
32902 are passed, the output always has a @samp{groups} result. The format
32903 of the @samp{group} result is described below.
32905 To reduce the number of roundtrips it's possible to list thread groups
32906 together with their children, by passing the @samp{--recurse} option
32907 and the recursion depth. Presently, only recursion depth of 1 is
32908 permitted. If this option is present, then every reported thread group
32909 will also include its children, either as @samp{group} or
32910 @samp{threads} field.
32912 In general, any combination of option and parameters is permitted, with
32913 the following caveats:
32917 When a single thread group is passed, the output will typically
32918 be the @samp{threads} result. Because threads may not contain
32919 anything, the @samp{recurse} option will be ignored.
32922 When the @samp{--available} option is passed, limited information may
32923 be available. In particular, the list of threads of a process might
32924 be inaccessible. Further, specifying specific thread groups might
32925 not give any performance advantage over listing all thread groups.
32926 The frontend should assume that @samp{-list-thread-groups --available}
32927 is always an expensive operation and cache the results.
32931 The @samp{groups} result is a list of tuples, where each tuple may
32932 have the following fields:
32936 Identifier of the thread group. This field is always present.
32937 The identifier is an opaque string; frontends should not try to
32938 convert it to an integer, even though it might look like one.
32941 The type of the thread group. At present, only @samp{process} is a
32945 The target-specific process identifier. This field is only present
32946 for thread groups of type @samp{process} and only if the process exists.
32949 The exit code of this group's last exited thread, formatted in octal.
32950 This field is only present for thread groups of type @samp{process} and
32951 only if the process is not running.
32954 The number of children this thread group has. This field may be
32955 absent for an available thread group.
32958 This field has a list of tuples as value, each tuple describing a
32959 thread. It may be present if the @samp{--recurse} option is
32960 specified, and it's actually possible to obtain the threads.
32963 This field is a list of integers, each identifying a core that one
32964 thread of the group is running on. This field may be absent if
32965 such information is not available.
32968 The name of the executable file that corresponds to this thread group.
32969 The field is only present for thread groups of type @samp{process},
32970 and only if there is a corresponding executable file.
32974 @subheading Example
32978 -list-thread-groups
32979 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32980 -list-thread-groups 17
32981 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32982 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32983 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32984 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32985 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32986 -list-thread-groups --available
32987 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32988 -list-thread-groups --available --recurse 1
32989 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32990 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32991 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32992 -list-thread-groups --available --recurse 1 17 18
32993 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32994 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32995 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32998 @subheading The @code{-info-os} Command
33001 @subsubheading Synopsis
33004 -info-os [ @var{type} ]
33007 If no argument is supplied, the command returns a table of available
33008 operating-system-specific information types. If one of these types is
33009 supplied as an argument @var{type}, then the command returns a table
33010 of data of that type.
33012 The types of information available depend on the target operating
33015 @subsubheading @value{GDBN} Command
33017 The corresponding @value{GDBN} command is @samp{info os}.
33019 @subsubheading Example
33021 When run on a @sc{gnu}/Linux system, the output will look something
33027 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
33028 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33029 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33030 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33031 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
33033 item=@{col0="files",col1="Listing of all file descriptors",
33034 col2="File descriptors"@},
33035 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33036 col2="Kernel modules"@},
33037 item=@{col0="msg",col1="Listing of all message queues",
33038 col2="Message queues"@},
33039 item=@{col0="processes",col1="Listing of all processes",
33040 col2="Processes"@},
33041 item=@{col0="procgroups",col1="Listing of all process groups",
33042 col2="Process groups"@},
33043 item=@{col0="semaphores",col1="Listing of all semaphores",
33044 col2="Semaphores"@},
33045 item=@{col0="shm",col1="Listing of all shared-memory regions",
33046 col2="Shared-memory regions"@},
33047 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33049 item=@{col0="threads",col1="Listing of all threads",
33053 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33054 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33055 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33056 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33057 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33058 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33059 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33060 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33062 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33063 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33067 (Note that the MI output here includes a @code{"Title"} column that
33068 does not appear in command-line @code{info os}; this column is useful
33069 for MI clients that want to enumerate the types of data, such as in a
33070 popup menu, but is needless clutter on the command line, and
33071 @code{info os} omits it.)
33073 @subheading The @code{-add-inferior} Command
33074 @findex -add-inferior
33076 @subheading Synopsis
33082 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33083 inferior is not associated with any executable. Such association may
33084 be established with the @samp{-file-exec-and-symbols} command
33085 (@pxref{GDB/MI File Commands}). The command response has a single
33086 field, @samp{inferior}, whose value is the identifier of the
33087 thread group corresponding to the new inferior.
33089 @subheading Example
33094 ^done,inferior="i3"
33097 @subheading The @code{-interpreter-exec} Command
33098 @findex -interpreter-exec
33100 @subheading Synopsis
33103 -interpreter-exec @var{interpreter} @var{command}
33105 @anchor{-interpreter-exec}
33107 Execute the specified @var{command} in the given @var{interpreter}.
33109 @subheading @value{GDBN} Command
33111 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33113 @subheading Example
33117 -interpreter-exec console "break main"
33118 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33119 &"During symbol reading, bad structure-type format.\n"
33120 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33125 @subheading The @code{-inferior-tty-set} Command
33126 @findex -inferior-tty-set
33128 @subheading Synopsis
33131 -inferior-tty-set /dev/pts/1
33134 Set terminal for future runs of the program being debugged.
33136 @subheading @value{GDBN} Command
33138 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33140 @subheading Example
33144 -inferior-tty-set /dev/pts/1
33149 @subheading The @code{-inferior-tty-show} Command
33150 @findex -inferior-tty-show
33152 @subheading Synopsis
33158 Show terminal for future runs of program being debugged.
33160 @subheading @value{GDBN} Command
33162 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33164 @subheading Example
33168 -inferior-tty-set /dev/pts/1
33172 ^done,inferior_tty_terminal="/dev/pts/1"
33176 @subheading The @code{-enable-timings} Command
33177 @findex -enable-timings
33179 @subheading Synopsis
33182 -enable-timings [yes | no]
33185 Toggle the printing of the wallclock, user and system times for an MI
33186 command as a field in its output. This command is to help frontend
33187 developers optimize the performance of their code. No argument is
33188 equivalent to @samp{yes}.
33190 @subheading @value{GDBN} Command
33194 @subheading Example
33202 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33203 addr="0x080484ed",func="main",file="myprog.c",
33204 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33206 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33214 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33215 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33216 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33217 fullname="/home/nickrob/myprog.c",line="73"@}
33222 @chapter @value{GDBN} Annotations
33224 This chapter describes annotations in @value{GDBN}. Annotations were
33225 designed to interface @value{GDBN} to graphical user interfaces or other
33226 similar programs which want to interact with @value{GDBN} at a
33227 relatively high level.
33229 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33233 This is Edition @value{EDITION}, @value{DATE}.
33237 * Annotations Overview:: What annotations are; the general syntax.
33238 * Server Prefix:: Issuing a command without affecting user state.
33239 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33240 * Errors:: Annotations for error messages.
33241 * Invalidation:: Some annotations describe things now invalid.
33242 * Annotations for Running::
33243 Whether the program is running, how it stopped, etc.
33244 * Source Annotations:: Annotations describing source code.
33247 @node Annotations Overview
33248 @section What is an Annotation?
33249 @cindex annotations
33251 Annotations start with a newline character, two @samp{control-z}
33252 characters, and the name of the annotation. If there is no additional
33253 information associated with this annotation, the name of the annotation
33254 is followed immediately by a newline. If there is additional
33255 information, the name of the annotation is followed by a space, the
33256 additional information, and a newline. The additional information
33257 cannot contain newline characters.
33259 Any output not beginning with a newline and two @samp{control-z}
33260 characters denotes literal output from @value{GDBN}. Currently there is
33261 no need for @value{GDBN} to output a newline followed by two
33262 @samp{control-z} characters, but if there was such a need, the
33263 annotations could be extended with an @samp{escape} annotation which
33264 means those three characters as output.
33266 The annotation @var{level}, which is specified using the
33267 @option{--annotate} command line option (@pxref{Mode Options}), controls
33268 how much information @value{GDBN} prints together with its prompt,
33269 values of expressions, source lines, and other types of output. Level 0
33270 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33271 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33272 for programs that control @value{GDBN}, and level 2 annotations have
33273 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33274 Interface, annotate, GDB's Obsolete Annotations}).
33277 @kindex set annotate
33278 @item set annotate @var{level}
33279 The @value{GDBN} command @code{set annotate} sets the level of
33280 annotations to the specified @var{level}.
33282 @item show annotate
33283 @kindex show annotate
33284 Show the current annotation level.
33287 This chapter describes level 3 annotations.
33289 A simple example of starting up @value{GDBN} with annotations is:
33292 $ @kbd{gdb --annotate=3}
33294 Copyright 2003 Free Software Foundation, Inc.
33295 GDB is free software, covered by the GNU General Public License,
33296 and you are welcome to change it and/or distribute copies of it
33297 under certain conditions.
33298 Type "show copying" to see the conditions.
33299 There is absolutely no warranty for GDB. Type "show warranty"
33301 This GDB was configured as "i386-pc-linux-gnu"
33312 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33313 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33314 denotes a @samp{control-z} character) are annotations; the rest is
33315 output from @value{GDBN}.
33317 @node Server Prefix
33318 @section The Server Prefix
33319 @cindex server prefix
33321 If you prefix a command with @samp{server } then it will not affect
33322 the command history, nor will it affect @value{GDBN}'s notion of which
33323 command to repeat if @key{RET} is pressed on a line by itself. This
33324 means that commands can be run behind a user's back by a front-end in
33325 a transparent manner.
33327 The @code{server } prefix does not affect the recording of values into
33328 the value history; to print a value without recording it into the
33329 value history, use the @code{output} command instead of the
33330 @code{print} command.
33332 Using this prefix also disables confirmation requests
33333 (@pxref{confirmation requests}).
33336 @section Annotation for @value{GDBN} Input
33338 @cindex annotations for prompts
33339 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33340 to know when to send output, when the output from a given command is
33343 Different kinds of input each have a different @dfn{input type}. Each
33344 input type has three annotations: a @code{pre-} annotation, which
33345 denotes the beginning of any prompt which is being output, a plain
33346 annotation, which denotes the end of the prompt, and then a @code{post-}
33347 annotation which denotes the end of any echo which may (or may not) be
33348 associated with the input. For example, the @code{prompt} input type
33349 features the following annotations:
33357 The input types are
33360 @findex pre-prompt annotation
33361 @findex prompt annotation
33362 @findex post-prompt annotation
33364 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33366 @findex pre-commands annotation
33367 @findex commands annotation
33368 @findex post-commands annotation
33370 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33371 command. The annotations are repeated for each command which is input.
33373 @findex pre-overload-choice annotation
33374 @findex overload-choice annotation
33375 @findex post-overload-choice annotation
33376 @item overload-choice
33377 When @value{GDBN} wants the user to select between various overloaded functions.
33379 @findex pre-query annotation
33380 @findex query annotation
33381 @findex post-query annotation
33383 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33385 @findex pre-prompt-for-continue annotation
33386 @findex prompt-for-continue annotation
33387 @findex post-prompt-for-continue annotation
33388 @item prompt-for-continue
33389 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33390 expect this to work well; instead use @code{set height 0} to disable
33391 prompting. This is because the counting of lines is buggy in the
33392 presence of annotations.
33397 @cindex annotations for errors, warnings and interrupts
33399 @findex quit annotation
33404 This annotation occurs right before @value{GDBN} responds to an interrupt.
33406 @findex error annotation
33411 This annotation occurs right before @value{GDBN} responds to an error.
33413 Quit and error annotations indicate that any annotations which @value{GDBN} was
33414 in the middle of may end abruptly. For example, if a
33415 @code{value-history-begin} annotation is followed by a @code{error}, one
33416 cannot expect to receive the matching @code{value-history-end}. One
33417 cannot expect not to receive it either, however; an error annotation
33418 does not necessarily mean that @value{GDBN} is immediately returning all the way
33421 @findex error-begin annotation
33422 A quit or error annotation may be preceded by
33428 Any output between that and the quit or error annotation is the error
33431 Warning messages are not yet annotated.
33432 @c If we want to change that, need to fix warning(), type_error(),
33433 @c range_error(), and possibly other places.
33436 @section Invalidation Notices
33438 @cindex annotations for invalidation messages
33439 The following annotations say that certain pieces of state may have
33443 @findex frames-invalid annotation
33444 @item ^Z^Zframes-invalid
33446 The frames (for example, output from the @code{backtrace} command) may
33449 @findex breakpoints-invalid annotation
33450 @item ^Z^Zbreakpoints-invalid
33452 The breakpoints may have changed. For example, the user just added or
33453 deleted a breakpoint.
33456 @node Annotations for Running
33457 @section Running the Program
33458 @cindex annotations for running programs
33460 @findex starting annotation
33461 @findex stopping annotation
33462 When the program starts executing due to a @value{GDBN} command such as
33463 @code{step} or @code{continue},
33469 is output. When the program stops,
33475 is output. Before the @code{stopped} annotation, a variety of
33476 annotations describe how the program stopped.
33479 @findex exited annotation
33480 @item ^Z^Zexited @var{exit-status}
33481 The program exited, and @var{exit-status} is the exit status (zero for
33482 successful exit, otherwise nonzero).
33484 @findex signalled annotation
33485 @findex signal-name annotation
33486 @findex signal-name-end annotation
33487 @findex signal-string annotation
33488 @findex signal-string-end annotation
33489 @item ^Z^Zsignalled
33490 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33491 annotation continues:
33497 ^Z^Zsignal-name-end
33501 ^Z^Zsignal-string-end
33506 where @var{name} is the name of the signal, such as @code{SIGILL} or
33507 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33508 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
33509 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33510 user's benefit and have no particular format.
33512 @findex signal annotation
33514 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33515 just saying that the program received the signal, not that it was
33516 terminated with it.
33518 @findex breakpoint annotation
33519 @item ^Z^Zbreakpoint @var{number}
33520 The program hit breakpoint number @var{number}.
33522 @findex watchpoint annotation
33523 @item ^Z^Zwatchpoint @var{number}
33524 The program hit watchpoint number @var{number}.
33527 @node Source Annotations
33528 @section Displaying Source
33529 @cindex annotations for source display
33531 @findex source annotation
33532 The following annotation is used instead of displaying source code:
33535 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33538 where @var{filename} is an absolute file name indicating which source
33539 file, @var{line} is the line number within that file (where 1 is the
33540 first line in the file), @var{character} is the character position
33541 within the file (where 0 is the first character in the file) (for most
33542 debug formats this will necessarily point to the beginning of a line),
33543 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33544 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33545 @var{addr} is the address in the target program associated with the
33546 source which is being displayed. The @var{addr} is in the form @samp{0x}
33547 followed by one or more lowercase hex digits (note that this does not
33548 depend on the language).
33550 @node JIT Interface
33551 @chapter JIT Compilation Interface
33552 @cindex just-in-time compilation
33553 @cindex JIT compilation interface
33555 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33556 interface. A JIT compiler is a program or library that generates native
33557 executable code at runtime and executes it, usually in order to achieve good
33558 performance while maintaining platform independence.
33560 Programs that use JIT compilation are normally difficult to debug because
33561 portions of their code are generated at runtime, instead of being loaded from
33562 object files, which is where @value{GDBN} normally finds the program's symbols
33563 and debug information. In order to debug programs that use JIT compilation,
33564 @value{GDBN} has an interface that allows the program to register in-memory
33565 symbol files with @value{GDBN} at runtime.
33567 If you are using @value{GDBN} to debug a program that uses this interface, then
33568 it should work transparently so long as you have not stripped the binary. If
33569 you are developing a JIT compiler, then the interface is documented in the rest
33570 of this chapter. At this time, the only known client of this interface is the
33573 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33574 JIT compiler communicates with @value{GDBN} by writing data into a global
33575 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33576 attaches, it reads a linked list of symbol files from the global variable to
33577 find existing code, and puts a breakpoint in the function so that it can find
33578 out about additional code.
33581 * Declarations:: Relevant C struct declarations
33582 * Registering Code:: Steps to register code
33583 * Unregistering Code:: Steps to unregister code
33584 * Custom Debug Info:: Emit debug information in a custom format
33588 @section JIT Declarations
33590 These are the relevant struct declarations that a C program should include to
33591 implement the interface:
33601 struct jit_code_entry
33603 struct jit_code_entry *next_entry;
33604 struct jit_code_entry *prev_entry;
33605 const char *symfile_addr;
33606 uint64_t symfile_size;
33609 struct jit_descriptor
33612 /* This type should be jit_actions_t, but we use uint32_t
33613 to be explicit about the bitwidth. */
33614 uint32_t action_flag;
33615 struct jit_code_entry *relevant_entry;
33616 struct jit_code_entry *first_entry;
33619 /* GDB puts a breakpoint in this function. */
33620 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33622 /* Make sure to specify the version statically, because the
33623 debugger may check the version before we can set it. */
33624 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33627 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33628 modifications to this global data properly, which can easily be done by putting
33629 a global mutex around modifications to these structures.
33631 @node Registering Code
33632 @section Registering Code
33634 To register code with @value{GDBN}, the JIT should follow this protocol:
33638 Generate an object file in memory with symbols and other desired debug
33639 information. The file must include the virtual addresses of the sections.
33642 Create a code entry for the file, which gives the start and size of the symbol
33646 Add it to the linked list in the JIT descriptor.
33649 Point the relevant_entry field of the descriptor at the entry.
33652 Set @code{action_flag} to @code{JIT_REGISTER} and call
33653 @code{__jit_debug_register_code}.
33656 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33657 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33658 new code. However, the linked list must still be maintained in order to allow
33659 @value{GDBN} to attach to a running process and still find the symbol files.
33661 @node Unregistering Code
33662 @section Unregistering Code
33664 If code is freed, then the JIT should use the following protocol:
33668 Remove the code entry corresponding to the code from the linked list.
33671 Point the @code{relevant_entry} field of the descriptor at the code entry.
33674 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33675 @code{__jit_debug_register_code}.
33678 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33679 and the JIT will leak the memory used for the associated symbol files.
33681 @node Custom Debug Info
33682 @section Custom Debug Info
33683 @cindex custom JIT debug info
33684 @cindex JIT debug info reader
33686 Generating debug information in platform-native file formats (like ELF
33687 or COFF) may be an overkill for JIT compilers; especially if all the
33688 debug info is used for is displaying a meaningful backtrace. The
33689 issue can be resolved by having the JIT writers decide on a debug info
33690 format and also provide a reader that parses the debug info generated
33691 by the JIT compiler. This section gives a brief overview on writing
33692 such a parser. More specific details can be found in the source file
33693 @file{gdb/jit-reader.in}, which is also installed as a header at
33694 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33696 The reader is implemented as a shared object (so this functionality is
33697 not available on platforms which don't allow loading shared objects at
33698 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33699 @code{jit-reader-unload} are provided, to be used to load and unload
33700 the readers from a preconfigured directory. Once loaded, the shared
33701 object is used the parse the debug information emitted by the JIT
33705 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33706 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33709 @node Using JIT Debug Info Readers
33710 @subsection Using JIT Debug Info Readers
33711 @kindex jit-reader-load
33712 @kindex jit-reader-unload
33714 Readers can be loaded and unloaded using the @code{jit-reader-load}
33715 and @code{jit-reader-unload} commands.
33718 @item jit-reader-load @var{reader}
33719 Load the JIT reader named @var{reader}, which is a shared
33720 object specified as either an absolute or a relative file name. In
33721 the latter case, @value{GDBN} will try to load the reader from a
33722 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33723 system (here @var{libdir} is the system library directory, often
33724 @file{/usr/local/lib}).
33726 Only one reader can be active at a time; trying to load a second
33727 reader when one is already loaded will result in @value{GDBN}
33728 reporting an error. A new JIT reader can be loaded by first unloading
33729 the current one using @code{jit-reader-unload} and then invoking
33730 @code{jit-reader-load}.
33732 @item jit-reader-unload
33733 Unload the currently loaded JIT reader.
33737 @node Writing JIT Debug Info Readers
33738 @subsection Writing JIT Debug Info Readers
33739 @cindex writing JIT debug info readers
33741 As mentioned, a reader is essentially a shared object conforming to a
33742 certain ABI. This ABI is described in @file{jit-reader.h}.
33744 @file{jit-reader.h} defines the structures, macros and functions
33745 required to write a reader. It is installed (along with
33746 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33747 the system include directory.
33749 Readers need to be released under a GPL compatible license. A reader
33750 can be declared as released under such a license by placing the macro
33751 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33753 The entry point for readers is the symbol @code{gdb_init_reader},
33754 which is expected to be a function with the prototype
33756 @findex gdb_init_reader
33758 extern struct gdb_reader_funcs *gdb_init_reader (void);
33761 @cindex @code{struct gdb_reader_funcs}
33763 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33764 functions. These functions are executed to read the debug info
33765 generated by the JIT compiler (@code{read}), to unwind stack frames
33766 (@code{unwind}) and to create canonical frame IDs
33767 (@code{get_Frame_id}). It also has a callback that is called when the
33768 reader is being unloaded (@code{destroy}). The struct looks like this
33771 struct gdb_reader_funcs
33773 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33774 int reader_version;
33776 /* For use by the reader. */
33779 gdb_read_debug_info *read;
33780 gdb_unwind_frame *unwind;
33781 gdb_get_frame_id *get_frame_id;
33782 gdb_destroy_reader *destroy;
33786 @cindex @code{struct gdb_symbol_callbacks}
33787 @cindex @code{struct gdb_unwind_callbacks}
33789 The callbacks are provided with another set of callbacks by
33790 @value{GDBN} to do their job. For @code{read}, these callbacks are
33791 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33792 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33793 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33794 files and new symbol tables inside those object files. @code{struct
33795 gdb_unwind_callbacks} has callbacks to read registers off the current
33796 frame and to write out the values of the registers in the previous
33797 frame. Both have a callback (@code{target_read}) to read bytes off the
33798 target's address space.
33800 @node In-Process Agent
33801 @chapter In-Process Agent
33802 @cindex debugging agent
33803 The traditional debugging model is conceptually low-speed, but works fine,
33804 because most bugs can be reproduced in debugging-mode execution. However,
33805 as multi-core or many-core processors are becoming mainstream, and
33806 multi-threaded programs become more and more popular, there should be more
33807 and more bugs that only manifest themselves at normal-mode execution, for
33808 example, thread races, because debugger's interference with the program's
33809 timing may conceal the bugs. On the other hand, in some applications,
33810 it is not feasible for the debugger to interrupt the program's execution
33811 long enough for the developer to learn anything helpful about its behavior.
33812 If the program's correctness depends on its real-time behavior, delays
33813 introduced by a debugger might cause the program to fail, even when the
33814 code itself is correct. It is useful to be able to observe the program's
33815 behavior without interrupting it.
33817 Therefore, traditional debugging model is too intrusive to reproduce
33818 some bugs. In order to reduce the interference with the program, we can
33819 reduce the number of operations performed by debugger. The
33820 @dfn{In-Process Agent}, a shared library, is running within the same
33821 process with inferior, and is able to perform some debugging operations
33822 itself. As a result, debugger is only involved when necessary, and
33823 performance of debugging can be improved accordingly. Note that
33824 interference with program can be reduced but can't be removed completely,
33825 because the in-process agent will still stop or slow down the program.
33827 The in-process agent can interpret and execute Agent Expressions
33828 (@pxref{Agent Expressions}) during performing debugging operations. The
33829 agent expressions can be used for different purposes, such as collecting
33830 data in tracepoints, and condition evaluation in breakpoints.
33832 @anchor{Control Agent}
33833 You can control whether the in-process agent is used as an aid for
33834 debugging with the following commands:
33837 @kindex set agent on
33839 Causes the in-process agent to perform some operations on behalf of the
33840 debugger. Just which operations requested by the user will be done
33841 by the in-process agent depends on the its capabilities. For example,
33842 if you request to evaluate breakpoint conditions in the in-process agent,
33843 and the in-process agent has such capability as well, then breakpoint
33844 conditions will be evaluated in the in-process agent.
33846 @kindex set agent off
33847 @item set agent off
33848 Disables execution of debugging operations by the in-process agent. All
33849 of the operations will be performed by @value{GDBN}.
33853 Display the current setting of execution of debugging operations by
33854 the in-process agent.
33858 * In-Process Agent Protocol::
33861 @node In-Process Agent Protocol
33862 @section In-Process Agent Protocol
33863 @cindex in-process agent protocol
33865 The in-process agent is able to communicate with both @value{GDBN} and
33866 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
33867 used for communications between @value{GDBN} or GDBserver and the IPA.
33868 In general, @value{GDBN} or GDBserver sends commands
33869 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33870 in-process agent replies back with the return result of the command, or
33871 some other information. The data sent to in-process agent is composed
33872 of primitive data types, such as 4-byte or 8-byte type, and composite
33873 types, which are called objects (@pxref{IPA Protocol Objects}).
33876 * IPA Protocol Objects::
33877 * IPA Protocol Commands::
33880 @node IPA Protocol Objects
33881 @subsection IPA Protocol Objects
33882 @cindex ipa protocol objects
33884 The commands sent to and results received from agent may contain some
33885 complex data types called @dfn{objects}.
33887 The in-process agent is running on the same machine with @value{GDBN}
33888 or GDBserver, so it doesn't have to handle as much differences between
33889 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33890 However, there are still some differences of two ends in two processes:
33894 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33895 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33897 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33898 GDBserver is compiled with one, and in-process agent is compiled with
33902 Here are the IPA Protocol Objects:
33906 agent expression object. It represents an agent expression
33907 (@pxref{Agent Expressions}).
33908 @anchor{agent expression object}
33910 tracepoint action object. It represents a tracepoint action
33911 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33912 memory, static trace data and to evaluate expression.
33913 @anchor{tracepoint action object}
33915 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33916 @anchor{tracepoint object}
33920 The following table describes important attributes of each IPA protocol
33923 @multitable @columnfractions .30 .20 .50
33924 @headitem Name @tab Size @tab Description
33925 @item @emph{agent expression object} @tab @tab
33926 @item length @tab 4 @tab length of bytes code
33927 @item byte code @tab @var{length} @tab contents of byte code
33928 @item @emph{tracepoint action for collecting memory} @tab @tab
33929 @item 'M' @tab 1 @tab type of tracepoint action
33930 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33931 address of the lowest byte to collect, otherwise @var{addr} is the offset
33932 of @var{basereg} for memory collecting.
33933 @item len @tab 8 @tab length of memory for collecting
33934 @item basereg @tab 4 @tab the register number containing the starting
33935 memory address for collecting.
33936 @item @emph{tracepoint action for collecting registers} @tab @tab
33937 @item 'R' @tab 1 @tab type of tracepoint action
33938 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33939 @item 'L' @tab 1 @tab type of tracepoint action
33940 @item @emph{tracepoint action for expression evaluation} @tab @tab
33941 @item 'X' @tab 1 @tab type of tracepoint action
33942 @item agent expression @tab length of @tab @ref{agent expression object}
33943 @item @emph{tracepoint object} @tab @tab
33944 @item number @tab 4 @tab number of tracepoint
33945 @item address @tab 8 @tab address of tracepoint inserted on
33946 @item type @tab 4 @tab type of tracepoint
33947 @item enabled @tab 1 @tab enable or disable of tracepoint
33948 @item step_count @tab 8 @tab step
33949 @item pass_count @tab 8 @tab pass
33950 @item numactions @tab 4 @tab number of tracepoint actions
33951 @item hit count @tab 8 @tab hit count
33952 @item trace frame usage @tab 8 @tab trace frame usage
33953 @item compiled_cond @tab 8 @tab compiled condition
33954 @item orig_size @tab 8 @tab orig size
33955 @item condition @tab 4 if condition is NULL otherwise length of
33956 @ref{agent expression object}
33957 @tab zero if condition is NULL, otherwise is
33958 @ref{agent expression object}
33959 @item actions @tab variable
33960 @tab numactions number of @ref{tracepoint action object}
33963 @node IPA Protocol Commands
33964 @subsection IPA Protocol Commands
33965 @cindex ipa protocol commands
33967 The spaces in each command are delimiters to ease reading this commands
33968 specification. They don't exist in real commands.
33972 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33973 Installs a new fast tracepoint described by @var{tracepoint_object}
33974 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
33975 head of @dfn{jumppad}, which is used to jump to data collection routine
33980 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33981 @var{target_address} is address of tracepoint in the inferior.
33982 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33983 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33984 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
33985 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33992 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33993 is about to kill inferiors.
34001 @item probe_marker_at:@var{address}
34002 Asks in-process agent to probe the marker at @var{address}.
34009 @item unprobe_marker_at:@var{address}
34010 Asks in-process agent to unprobe the marker at @var{address}.
34014 @chapter Reporting Bugs in @value{GDBN}
34015 @cindex bugs in @value{GDBN}
34016 @cindex reporting bugs in @value{GDBN}
34018 Your bug reports play an essential role in making @value{GDBN} reliable.
34020 Reporting a bug may help you by bringing a solution to your problem, or it
34021 may not. But in any case the principal function of a bug report is to help
34022 the entire community by making the next version of @value{GDBN} work better. Bug
34023 reports are your contribution to the maintenance of @value{GDBN}.
34025 In order for a bug report to serve its purpose, you must include the
34026 information that enables us to fix the bug.
34029 * Bug Criteria:: Have you found a bug?
34030 * Bug Reporting:: How to report bugs
34034 @section Have You Found a Bug?
34035 @cindex bug criteria
34037 If you are not sure whether you have found a bug, here are some guidelines:
34040 @cindex fatal signal
34041 @cindex debugger crash
34042 @cindex crash of debugger
34044 If the debugger gets a fatal signal, for any input whatever, that is a
34045 @value{GDBN} bug. Reliable debuggers never crash.
34047 @cindex error on valid input
34049 If @value{GDBN} produces an error message for valid input, that is a
34050 bug. (Note that if you're cross debugging, the problem may also be
34051 somewhere in the connection to the target.)
34053 @cindex invalid input
34055 If @value{GDBN} does not produce an error message for invalid input,
34056 that is a bug. However, you should note that your idea of
34057 ``invalid input'' might be our idea of ``an extension'' or ``support
34058 for traditional practice''.
34061 If you are an experienced user of debugging tools, your suggestions
34062 for improvement of @value{GDBN} are welcome in any case.
34065 @node Bug Reporting
34066 @section How to Report Bugs
34067 @cindex bug reports
34068 @cindex @value{GDBN} bugs, reporting
34070 A number of companies and individuals offer support for @sc{gnu} products.
34071 If you obtained @value{GDBN} from a support organization, we recommend you
34072 contact that organization first.
34074 You can find contact information for many support companies and
34075 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34077 @c should add a web page ref...
34080 @ifset BUGURL_DEFAULT
34081 In any event, we also recommend that you submit bug reports for
34082 @value{GDBN}. The preferred method is to submit them directly using
34083 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34084 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34087 @strong{Do not send bug reports to @samp{info-gdb}, or to
34088 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34089 not want to receive bug reports. Those that do have arranged to receive
34092 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34093 serves as a repeater. The mailing list and the newsgroup carry exactly
34094 the same messages. Often people think of posting bug reports to the
34095 newsgroup instead of mailing them. This appears to work, but it has one
34096 problem which can be crucial: a newsgroup posting often lacks a mail
34097 path back to the sender. Thus, if we need to ask for more information,
34098 we may be unable to reach you. For this reason, it is better to send
34099 bug reports to the mailing list.
34101 @ifclear BUGURL_DEFAULT
34102 In any event, we also recommend that you submit bug reports for
34103 @value{GDBN} to @value{BUGURL}.
34107 The fundamental principle of reporting bugs usefully is this:
34108 @strong{report all the facts}. If you are not sure whether to state a
34109 fact or leave it out, state it!
34111 Often people omit facts because they think they know what causes the
34112 problem and assume that some details do not matter. Thus, you might
34113 assume that the name of the variable you use in an example does not matter.
34114 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34115 stray memory reference which happens to fetch from the location where that
34116 name is stored in memory; perhaps, if the name were different, the contents
34117 of that location would fool the debugger into doing the right thing despite
34118 the bug. Play it safe and give a specific, complete example. That is the
34119 easiest thing for you to do, and the most helpful.
34121 Keep in mind that the purpose of a bug report is to enable us to fix the
34122 bug. It may be that the bug has been reported previously, but neither
34123 you nor we can know that unless your bug report is complete and
34126 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34127 bell?'' Those bug reports are useless, and we urge everyone to
34128 @emph{refuse to respond to them} except to chide the sender to report
34131 To enable us to fix the bug, you should include all these things:
34135 The version of @value{GDBN}. @value{GDBN} announces it if you start
34136 with no arguments; you can also print it at any time using @code{show
34139 Without this, we will not know whether there is any point in looking for
34140 the bug in the current version of @value{GDBN}.
34143 The type of machine you are using, and the operating system name and
34147 The details of the @value{GDBN} build-time configuration.
34148 @value{GDBN} shows these details if you invoke it with the
34149 @option{--configuration} command-line option, or if you type
34150 @code{show configuration} at @value{GDBN}'s prompt.
34153 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34154 ``@value{GCC}--2.8.1''.
34157 What compiler (and its version) was used to compile the program you are
34158 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34159 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34160 to get this information; for other compilers, see the documentation for
34164 The command arguments you gave the compiler to compile your example and
34165 observe the bug. For example, did you use @samp{-O}? To guarantee
34166 you will not omit something important, list them all. A copy of the
34167 Makefile (or the output from make) is sufficient.
34169 If we were to try to guess the arguments, we would probably guess wrong
34170 and then we might not encounter the bug.
34173 A complete input script, and all necessary source files, that will
34177 A description of what behavior you observe that you believe is
34178 incorrect. For example, ``It gets a fatal signal.''
34180 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34181 will certainly notice it. But if the bug is incorrect output, we might
34182 not notice unless it is glaringly wrong. You might as well not give us
34183 a chance to make a mistake.
34185 Even if the problem you experience is a fatal signal, you should still
34186 say so explicitly. Suppose something strange is going on, such as, your
34187 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34188 the C library on your system. (This has happened!) Your copy might
34189 crash and ours would not. If you told us to expect a crash, then when
34190 ours fails to crash, we would know that the bug was not happening for
34191 us. If you had not told us to expect a crash, then we would not be able
34192 to draw any conclusion from our observations.
34195 @cindex recording a session script
34196 To collect all this information, you can use a session recording program
34197 such as @command{script}, which is available on many Unix systems.
34198 Just run your @value{GDBN} session inside @command{script} and then
34199 include the @file{typescript} file with your bug report.
34201 Another way to record a @value{GDBN} session is to run @value{GDBN}
34202 inside Emacs and then save the entire buffer to a file.
34205 If you wish to suggest changes to the @value{GDBN} source, send us context
34206 diffs. If you even discuss something in the @value{GDBN} source, refer to
34207 it by context, not by line number.
34209 The line numbers in our development sources will not match those in your
34210 sources. Your line numbers would convey no useful information to us.
34214 Here are some things that are not necessary:
34218 A description of the envelope of the bug.
34220 Often people who encounter a bug spend a lot of time investigating
34221 which changes to the input file will make the bug go away and which
34222 changes will not affect it.
34224 This is often time consuming and not very useful, because the way we
34225 will find the bug is by running a single example under the debugger
34226 with breakpoints, not by pure deduction from a series of examples.
34227 We recommend that you save your time for something else.
34229 Of course, if you can find a simpler example to report @emph{instead}
34230 of the original one, that is a convenience for us. Errors in the
34231 output will be easier to spot, running under the debugger will take
34232 less time, and so on.
34234 However, simplification is not vital; if you do not want to do this,
34235 report the bug anyway and send us the entire test case you used.
34238 A patch for the bug.
34240 A patch for the bug does help us if it is a good one. But do not omit
34241 the necessary information, such as the test case, on the assumption that
34242 a patch is all we need. We might see problems with your patch and decide
34243 to fix the problem another way, or we might not understand it at all.
34245 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34246 construct an example that will make the program follow a certain path
34247 through the code. If you do not send us the example, we will not be able
34248 to construct one, so we will not be able to verify that the bug is fixed.
34250 And if we cannot understand what bug you are trying to fix, or why your
34251 patch should be an improvement, we will not install it. A test case will
34252 help us to understand.
34255 A guess about what the bug is or what it depends on.
34257 Such guesses are usually wrong. Even we cannot guess right about such
34258 things without first using the debugger to find the facts.
34261 @c The readline documentation is distributed with the readline code
34262 @c and consists of the two following files:
34265 @c Use -I with makeinfo to point to the appropriate directory,
34266 @c environment var TEXINPUTS with TeX.
34267 @ifclear SYSTEM_READLINE
34268 @include rluser.texi
34269 @include hsuser.texi
34273 @appendix In Memoriam
34275 The @value{GDBN} project mourns the loss of the following long-time
34280 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34281 to Free Software in general. Outside of @value{GDBN}, he was known in
34282 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34284 @item Michael Snyder
34285 Michael was one of the Global Maintainers of the @value{GDBN} project,
34286 with contributions recorded as early as 1996, until 2011. In addition
34287 to his day to day participation, he was a large driving force behind
34288 adding Reverse Debugging to @value{GDBN}.
34291 Beyond their technical contributions to the project, they were also
34292 enjoyable members of the Free Software Community. We will miss them.
34294 @node Formatting Documentation
34295 @appendix Formatting Documentation
34297 @cindex @value{GDBN} reference card
34298 @cindex reference card
34299 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34300 for printing with PostScript or Ghostscript, in the @file{gdb}
34301 subdirectory of the main source directory@footnote{In
34302 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34303 release.}. If you can use PostScript or Ghostscript with your printer,
34304 you can print the reference card immediately with @file{refcard.ps}.
34306 The release also includes the source for the reference card. You
34307 can format it, using @TeX{}, by typing:
34313 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34314 mode on US ``letter'' size paper;
34315 that is, on a sheet 11 inches wide by 8.5 inches
34316 high. You will need to specify this form of printing as an option to
34317 your @sc{dvi} output program.
34319 @cindex documentation
34321 All the documentation for @value{GDBN} comes as part of the machine-readable
34322 distribution. The documentation is written in Texinfo format, which is
34323 a documentation system that uses a single source file to produce both
34324 on-line information and a printed manual. You can use one of the Info
34325 formatting commands to create the on-line version of the documentation
34326 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34328 @value{GDBN} includes an already formatted copy of the on-line Info
34329 version of this manual in the @file{gdb} subdirectory. The main Info
34330 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34331 subordinate files matching @samp{gdb.info*} in the same directory. If
34332 necessary, you can print out these files, or read them with any editor;
34333 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34334 Emacs or the standalone @code{info} program, available as part of the
34335 @sc{gnu} Texinfo distribution.
34337 If you want to format these Info files yourself, you need one of the
34338 Info formatting programs, such as @code{texinfo-format-buffer} or
34341 If you have @code{makeinfo} installed, and are in the top level
34342 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34343 version @value{GDBVN}), you can make the Info file by typing:
34350 If you want to typeset and print copies of this manual, you need @TeX{},
34351 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34352 Texinfo definitions file.
34354 @TeX{} is a typesetting program; it does not print files directly, but
34355 produces output files called @sc{dvi} files. To print a typeset
34356 document, you need a program to print @sc{dvi} files. If your system
34357 has @TeX{} installed, chances are it has such a program. The precise
34358 command to use depends on your system; @kbd{lpr -d} is common; another
34359 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34360 require a file name without any extension or a @samp{.dvi} extension.
34362 @TeX{} also requires a macro definitions file called
34363 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34364 written in Texinfo format. On its own, @TeX{} cannot either read or
34365 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34366 and is located in the @file{gdb-@var{version-number}/texinfo}
34369 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34370 typeset and print this manual. First switch to the @file{gdb}
34371 subdirectory of the main source directory (for example, to
34372 @file{gdb-@value{GDBVN}/gdb}) and type:
34378 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34380 @node Installing GDB
34381 @appendix Installing @value{GDBN}
34382 @cindex installation
34385 * Requirements:: Requirements for building @value{GDBN}
34386 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34387 * Separate Objdir:: Compiling @value{GDBN} in another directory
34388 * Config Names:: Specifying names for hosts and targets
34389 * Configure Options:: Summary of options for configure
34390 * System-wide configuration:: Having a system-wide init file
34394 @section Requirements for Building @value{GDBN}
34395 @cindex building @value{GDBN}, requirements for
34397 Building @value{GDBN} requires various tools and packages to be available.
34398 Other packages will be used only if they are found.
34400 @heading Tools/Packages Necessary for Building @value{GDBN}
34402 @item ISO C90 compiler
34403 @value{GDBN} is written in ISO C90. It should be buildable with any
34404 working C90 compiler, e.g.@: GCC.
34408 @heading Tools/Packages Optional for Building @value{GDBN}
34412 @value{GDBN} can use the Expat XML parsing library. This library may be
34413 included with your operating system distribution; if it is not, you
34414 can get the latest version from @url{http://expat.sourceforge.net}.
34415 The @file{configure} script will search for this library in several
34416 standard locations; if it is installed in an unusual path, you can
34417 use the @option{--with-libexpat-prefix} option to specify its location.
34423 Remote protocol memory maps (@pxref{Memory Map Format})
34425 Target descriptions (@pxref{Target Descriptions})
34427 Remote shared library lists (@xref{Library List Format},
34428 or alternatively @pxref{Library List Format for SVR4 Targets})
34430 MS-Windows shared libraries (@pxref{Shared Libraries})
34432 Traceframe info (@pxref{Traceframe Info Format})
34434 Branch trace (@pxref{Branch Trace Format},
34435 @pxref{Branch Trace Configuration Format})
34440 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
34441 library. This library may be included with your operating system
34442 distribution; if it is not, you can get the latest version from
34443 @url{http://www.mpfr.org}. The @file{configure} script will search
34444 for this library in several standard locations; if it is installed
34445 in an unusual path, you can use the @option{--with-libmpfr-prefix}
34446 option to specify its location.
34448 GNU MPFR is used to emulate target floating-point arithmetic during
34449 expression evaluation when the target uses different floating-point
34450 formats than the host. If GNU MPFR it is not available, @value{GDBN}
34451 will fall back to using host floating-point arithmetic.
34454 @cindex compressed debug sections
34455 @value{GDBN} will use the @samp{zlib} library, if available, to read
34456 compressed debug sections. Some linkers, such as GNU gold, are capable
34457 of producing binaries with compressed debug sections. If @value{GDBN}
34458 is compiled with @samp{zlib}, it will be able to read the debug
34459 information in such binaries.
34461 The @samp{zlib} library is likely included with your operating system
34462 distribution; if it is not, you can get the latest version from
34463 @url{http://zlib.net}.
34466 @value{GDBN}'s features related to character sets (@pxref{Character
34467 Sets}) require a functioning @code{iconv} implementation. If you are
34468 on a GNU system, then this is provided by the GNU C Library. Some
34469 other systems also provide a working @code{iconv}.
34471 If @value{GDBN} is using the @code{iconv} program which is installed
34472 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34473 This is done with @option{--with-iconv-bin} which specifies the
34474 directory that contains the @code{iconv} program.
34476 On systems without @code{iconv}, you can install GNU Libiconv. If you
34477 have previously installed Libiconv, you can use the
34478 @option{--with-libiconv-prefix} option to configure.
34480 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34481 arrange to build Libiconv if a directory named @file{libiconv} appears
34482 in the top-most source directory. If Libiconv is built this way, and
34483 if the operating system does not provide a suitable @code{iconv}
34484 implementation, then the just-built library will automatically be used
34485 by @value{GDBN}. One easy way to set this up is to download GNU
34486 Libiconv, unpack it, and then rename the directory holding the
34487 Libiconv source code to @samp{libiconv}.
34490 @node Running Configure
34491 @section Invoking the @value{GDBN} @file{configure} Script
34492 @cindex configuring @value{GDBN}
34493 @value{GDBN} comes with a @file{configure} script that automates the process
34494 of preparing @value{GDBN} for installation; you can then use @code{make} to
34495 build the @code{gdb} program.
34497 @c irrelevant in info file; it's as current as the code it lives with.
34498 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34499 look at the @file{README} file in the sources; we may have improved the
34500 installation procedures since publishing this manual.}
34503 The @value{GDBN} distribution includes all the source code you need for
34504 @value{GDBN} in a single directory, whose name is usually composed by
34505 appending the version number to @samp{gdb}.
34507 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34508 @file{gdb-@value{GDBVN}} directory. That directory contains:
34511 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34512 script for configuring @value{GDBN} and all its supporting libraries
34514 @item gdb-@value{GDBVN}/gdb
34515 the source specific to @value{GDBN} itself
34517 @item gdb-@value{GDBVN}/bfd
34518 source for the Binary File Descriptor library
34520 @item gdb-@value{GDBVN}/include
34521 @sc{gnu} include files
34523 @item gdb-@value{GDBVN}/libiberty
34524 source for the @samp{-liberty} free software library
34526 @item gdb-@value{GDBVN}/opcodes
34527 source for the library of opcode tables and disassemblers
34529 @item gdb-@value{GDBVN}/readline
34530 source for the @sc{gnu} command-line interface
34532 @item gdb-@value{GDBVN}/glob
34533 source for the @sc{gnu} filename pattern-matching subroutine
34535 @item gdb-@value{GDBVN}/mmalloc
34536 source for the @sc{gnu} memory-mapped malloc package
34539 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34540 from the @file{gdb-@var{version-number}} source directory, which in
34541 this example is the @file{gdb-@value{GDBVN}} directory.
34543 First switch to the @file{gdb-@var{version-number}} source directory
34544 if you are not already in it; then run @file{configure}. Pass the
34545 identifier for the platform on which @value{GDBN} will run as an
34551 cd gdb-@value{GDBVN}
34552 ./configure @var{host}
34557 where @var{host} is an identifier such as @samp{sun4} or
34558 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34559 (You can often leave off @var{host}; @file{configure} tries to guess the
34560 correct value by examining your system.)
34562 Running @samp{configure @var{host}} and then running @code{make} builds the
34563 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34564 libraries, then @code{gdb} itself. The configured source files, and the
34565 binaries, are left in the corresponding source directories.
34568 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34569 system does not recognize this automatically when you run a different
34570 shell, you may need to run @code{sh} on it explicitly:
34573 sh configure @var{host}
34576 If you run @file{configure} from a directory that contains source
34577 directories for multiple libraries or programs, such as the
34578 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34580 creates configuration files for every directory level underneath (unless
34581 you tell it not to, with the @samp{--norecursion} option).
34583 You should run the @file{configure} script from the top directory in the
34584 source tree, the @file{gdb-@var{version-number}} directory. If you run
34585 @file{configure} from one of the subdirectories, you will configure only
34586 that subdirectory. That is usually not what you want. In particular,
34587 if you run the first @file{configure} from the @file{gdb} subdirectory
34588 of the @file{gdb-@var{version-number}} directory, you will omit the
34589 configuration of @file{bfd}, @file{readline}, and other sibling
34590 directories of the @file{gdb} subdirectory. This leads to build errors
34591 about missing include files such as @file{bfd/bfd.h}.
34593 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34594 However, you should make sure that the shell on your path (named by
34595 the @samp{SHELL} environment variable) is publicly readable. Remember
34596 that @value{GDBN} uses the shell to start your program---some systems refuse to
34597 let @value{GDBN} debug child processes whose programs are not readable.
34599 @node Separate Objdir
34600 @section Compiling @value{GDBN} in Another Directory
34602 If you want to run @value{GDBN} versions for several host or target machines,
34603 you need a different @code{gdb} compiled for each combination of
34604 host and target. @file{configure} is designed to make this easy by
34605 allowing you to generate each configuration in a separate subdirectory,
34606 rather than in the source directory. If your @code{make} program
34607 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34608 @code{make} in each of these directories builds the @code{gdb}
34609 program specified there.
34611 To build @code{gdb} in a separate directory, run @file{configure}
34612 with the @samp{--srcdir} option to specify where to find the source.
34613 (You also need to specify a path to find @file{configure}
34614 itself from your working directory. If the path to @file{configure}
34615 would be the same as the argument to @samp{--srcdir}, you can leave out
34616 the @samp{--srcdir} option; it is assumed.)
34618 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34619 separate directory for a Sun 4 like this:
34623 cd gdb-@value{GDBVN}
34626 ../gdb-@value{GDBVN}/configure sun4
34631 When @file{configure} builds a configuration using a remote source
34632 directory, it creates a tree for the binaries with the same structure
34633 (and using the same names) as the tree under the source directory. In
34634 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34635 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34636 @file{gdb-sun4/gdb}.
34638 Make sure that your path to the @file{configure} script has just one
34639 instance of @file{gdb} in it. If your path to @file{configure} looks
34640 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34641 one subdirectory of @value{GDBN}, not the whole package. This leads to
34642 build errors about missing include files such as @file{bfd/bfd.h}.
34644 One popular reason to build several @value{GDBN} configurations in separate
34645 directories is to configure @value{GDBN} for cross-compiling (where
34646 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34647 programs that run on another machine---the @dfn{target}).
34648 You specify a cross-debugging target by
34649 giving the @samp{--target=@var{target}} option to @file{configure}.
34651 When you run @code{make} to build a program or library, you must run
34652 it in a configured directory---whatever directory you were in when you
34653 called @file{configure} (or one of its subdirectories).
34655 The @code{Makefile} that @file{configure} generates in each source
34656 directory also runs recursively. If you type @code{make} in a source
34657 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34658 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34659 will build all the required libraries, and then build GDB.
34661 When you have multiple hosts or targets configured in separate
34662 directories, you can run @code{make} on them in parallel (for example,
34663 if they are NFS-mounted on each of the hosts); they will not interfere
34667 @section Specifying Names for Hosts and Targets
34669 The specifications used for hosts and targets in the @file{configure}
34670 script are based on a three-part naming scheme, but some short predefined
34671 aliases are also supported. The full naming scheme encodes three pieces
34672 of information in the following pattern:
34675 @var{architecture}-@var{vendor}-@var{os}
34678 For example, you can use the alias @code{sun4} as a @var{host} argument,
34679 or as the value for @var{target} in a @code{--target=@var{target}}
34680 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34682 The @file{configure} script accompanying @value{GDBN} does not provide
34683 any query facility to list all supported host and target names or
34684 aliases. @file{configure} calls the Bourne shell script
34685 @code{config.sub} to map abbreviations to full names; you can read the
34686 script, if you wish, or you can use it to test your guesses on
34687 abbreviations---for example:
34690 % sh config.sub i386-linux
34692 % sh config.sub alpha-linux
34693 alpha-unknown-linux-gnu
34694 % sh config.sub hp9k700
34696 % sh config.sub sun4
34697 sparc-sun-sunos4.1.1
34698 % sh config.sub sun3
34699 m68k-sun-sunos4.1.1
34700 % sh config.sub i986v
34701 Invalid configuration `i986v': machine `i986v' not recognized
34705 @code{config.sub} is also distributed in the @value{GDBN} source
34706 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34708 @node Configure Options
34709 @section @file{configure} Options
34711 Here is a summary of the @file{configure} options and arguments that
34712 are most often useful for building @value{GDBN}. @file{configure} also has
34713 several other options not listed here. @inforef{What Configure
34714 Does,,configure.info}, for a full explanation of @file{configure}.
34717 configure @r{[}--help@r{]}
34718 @r{[}--prefix=@var{dir}@r{]}
34719 @r{[}--exec-prefix=@var{dir}@r{]}
34720 @r{[}--srcdir=@var{dirname}@r{]}
34721 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34722 @r{[}--target=@var{target}@r{]}
34727 You may introduce options with a single @samp{-} rather than
34728 @samp{--} if you prefer; but you may abbreviate option names if you use
34733 Display a quick summary of how to invoke @file{configure}.
34735 @item --prefix=@var{dir}
34736 Configure the source to install programs and files under directory
34739 @item --exec-prefix=@var{dir}
34740 Configure the source to install programs under directory
34743 @c avoid splitting the warning from the explanation:
34745 @item --srcdir=@var{dirname}
34746 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34747 @code{make} that implements the @code{VPATH} feature.}@*
34748 Use this option to make configurations in directories separate from the
34749 @value{GDBN} source directories. Among other things, you can use this to
34750 build (or maintain) several configurations simultaneously, in separate
34751 directories. @file{configure} writes configuration-specific files in
34752 the current directory, but arranges for them to use the source in the
34753 directory @var{dirname}. @file{configure} creates directories under
34754 the working directory in parallel to the source directories below
34757 @item --norecursion
34758 Configure only the directory level where @file{configure} is executed; do not
34759 propagate configuration to subdirectories.
34761 @item --target=@var{target}
34762 Configure @value{GDBN} for cross-debugging programs running on the specified
34763 @var{target}. Without this option, @value{GDBN} is configured to debug
34764 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34766 There is no convenient way to generate a list of all available targets.
34768 @item @var{host} @dots{}
34769 Configure @value{GDBN} to run on the specified @var{host}.
34771 There is no convenient way to generate a list of all available hosts.
34774 There are many other options available as well, but they are generally
34775 needed for special purposes only.
34777 @node System-wide configuration
34778 @section System-wide configuration and settings
34779 @cindex system-wide init file
34781 @value{GDBN} can be configured to have a system-wide init file;
34782 this file will be read and executed at startup (@pxref{Startup, , What
34783 @value{GDBN} does during startup}).
34785 Here is the corresponding configure option:
34788 @item --with-system-gdbinit=@var{file}
34789 Specify that the default location of the system-wide init file is
34793 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34794 it may be subject to relocation. Two possible cases:
34798 If the default location of this init file contains @file{$prefix},
34799 it will be subject to relocation. Suppose that the configure options
34800 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34801 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34802 init file is looked for as @file{$install/etc/gdbinit} instead of
34803 @file{$prefix/etc/gdbinit}.
34806 By contrast, if the default location does not contain the prefix,
34807 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34808 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34809 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34810 wherever @value{GDBN} is installed.
34813 If the configured location of the system-wide init file (as given by the
34814 @option{--with-system-gdbinit} option at configure time) is in the
34815 data-directory (as specified by @option{--with-gdb-datadir} at configure
34816 time) or in one of its subdirectories, then @value{GDBN} will look for the
34817 system-wide init file in the directory specified by the
34818 @option{--data-directory} command-line option.
34819 Note that the system-wide init file is only read once, during @value{GDBN}
34820 initialization. If the data-directory is changed after @value{GDBN} has
34821 started with the @code{set data-directory} command, the file will not be
34825 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
34828 @node System-wide Configuration Scripts
34829 @subsection Installed System-wide Configuration Scripts
34830 @cindex system-wide configuration scripts
34832 The @file{system-gdbinit} directory, located inside the data-directory
34833 (as specified by @option{--with-gdb-datadir} at configure time) contains
34834 a number of scripts which can be used as system-wide init files. To
34835 automatically source those scripts at startup, @value{GDBN} should be
34836 configured with @option{--with-system-gdbinit}. Otherwise, any user
34837 should be able to source them by hand as needed.
34839 The following scripts are currently available:
34842 @item @file{elinos.py}
34844 @cindex ELinOS system-wide configuration script
34845 This script is useful when debugging a program on an ELinOS target.
34846 It takes advantage of the environment variables defined in a standard
34847 ELinOS environment in order to determine the location of the system
34848 shared libraries, and then sets the @samp{solib-absolute-prefix}
34849 and @samp{solib-search-path} variables appropriately.
34851 @item @file{wrs-linux.py}
34852 @pindex wrs-linux.py
34853 @cindex Wind River Linux system-wide configuration script
34854 This script is useful when debugging a program on a target running
34855 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
34856 the host-side sysroot used by the target system.
34860 @node Maintenance Commands
34861 @appendix Maintenance Commands
34862 @cindex maintenance commands
34863 @cindex internal commands
34865 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34866 includes a number of commands intended for @value{GDBN} developers,
34867 that are not documented elsewhere in this manual. These commands are
34868 provided here for reference. (For commands that turn on debugging
34869 messages, see @ref{Debugging Output}.)
34872 @kindex maint agent
34873 @kindex maint agent-eval
34874 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34875 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34876 Translate the given @var{expression} into remote agent bytecodes.
34877 This command is useful for debugging the Agent Expression mechanism
34878 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34879 expression useful for data collection, such as by tracepoints, while
34880 @samp{maint agent-eval} produces an expression that evaluates directly
34881 to a result. For instance, a collection expression for @code{globa +
34882 globb} will include bytecodes to record four bytes of memory at each
34883 of the addresses of @code{globa} and @code{globb}, while discarding
34884 the result of the addition, while an evaluation expression will do the
34885 addition and return the sum.
34886 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34887 If not, generate remote agent bytecode for current frame PC address.
34889 @kindex maint agent-printf
34890 @item maint agent-printf @var{format},@var{expr},...
34891 Translate the given format string and list of argument expressions
34892 into remote agent bytecodes and display them as a disassembled list.
34893 This command is useful for debugging the agent version of dynamic
34894 printf (@pxref{Dynamic Printf}).
34896 @kindex maint info breakpoints
34897 @item @anchor{maint info breakpoints}maint info breakpoints
34898 Using the same format as @samp{info breakpoints}, display both the
34899 breakpoints you've set explicitly, and those @value{GDBN} is using for
34900 internal purposes. Internal breakpoints are shown with negative
34901 breakpoint numbers. The type column identifies what kind of breakpoint
34906 Normal, explicitly set breakpoint.
34909 Normal, explicitly set watchpoint.
34912 Internal breakpoint, used to handle correctly stepping through
34913 @code{longjmp} calls.
34915 @item longjmp resume
34916 Internal breakpoint at the target of a @code{longjmp}.
34919 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34922 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34925 Shared library events.
34929 @kindex maint info btrace
34930 @item maint info btrace
34931 Pint information about raw branch tracing data.
34933 @kindex maint btrace packet-history
34934 @item maint btrace packet-history
34935 Print the raw branch trace packets that are used to compute the
34936 execution history for the @samp{record btrace} command. Both the
34937 information and the format in which it is printed depend on the btrace
34942 For the BTS recording format, print a list of blocks of sequential
34943 code. For each block, the following information is printed:
34947 Newer blocks have higher numbers. The oldest block has number zero.
34948 @item Lowest @samp{PC}
34949 @item Highest @samp{PC}
34953 For the Intel Processor Trace recording format, print a list of
34954 Intel Processor Trace packets. For each packet, the following
34955 information is printed:
34958 @item Packet number
34959 Newer packets have higher numbers. The oldest packet has number zero.
34961 The packet's offset in the trace stream.
34962 @item Packet opcode and payload
34966 @kindex maint btrace clear-packet-history
34967 @item maint btrace clear-packet-history
34968 Discards the cached packet history printed by the @samp{maint btrace
34969 packet-history} command. The history will be computed again when
34972 @kindex maint btrace clear
34973 @item maint btrace clear
34974 Discard the branch trace data. The data will be fetched anew and the
34975 branch trace will be recomputed when needed.
34977 This implicitly truncates the branch trace to a single branch trace
34978 buffer. When updating branch trace incrementally, the branch trace
34979 available to @value{GDBN} may be bigger than a single branch trace
34982 @kindex maint set btrace pt skip-pad
34983 @item maint set btrace pt skip-pad
34984 @kindex maint show btrace pt skip-pad
34985 @item maint show btrace pt skip-pad
34986 Control whether @value{GDBN} will skip PAD packets when computing the
34989 @kindex set displaced-stepping
34990 @kindex show displaced-stepping
34991 @cindex displaced stepping support
34992 @cindex out-of-line single-stepping
34993 @item set displaced-stepping
34994 @itemx show displaced-stepping
34995 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34996 if the target supports it. Displaced stepping is a way to single-step
34997 over breakpoints without removing them from the inferior, by executing
34998 an out-of-line copy of the instruction that was originally at the
34999 breakpoint location. It is also known as out-of-line single-stepping.
35002 @item set displaced-stepping on
35003 If the target architecture supports it, @value{GDBN} will use
35004 displaced stepping to step over breakpoints.
35006 @item set displaced-stepping off
35007 @value{GDBN} will not use displaced stepping to step over breakpoints,
35008 even if such is supported by the target architecture.
35010 @cindex non-stop mode, and @samp{set displaced-stepping}
35011 @item set displaced-stepping auto
35012 This is the default mode. @value{GDBN} will use displaced stepping
35013 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35014 architecture supports displaced stepping.
35017 @kindex maint check-psymtabs
35018 @item maint check-psymtabs
35019 Check the consistency of currently expanded psymtabs versus symtabs.
35020 Use this to check, for example, whether a symbol is in one but not the other.
35022 @kindex maint check-symtabs
35023 @item maint check-symtabs
35024 Check the consistency of currently expanded symtabs.
35026 @kindex maint expand-symtabs
35027 @item maint expand-symtabs [@var{regexp}]
35028 Expand symbol tables.
35029 If @var{regexp} is specified, only expand symbol tables for file
35030 names matching @var{regexp}.
35032 @kindex maint set catch-demangler-crashes
35033 @kindex maint show catch-demangler-crashes
35034 @cindex demangler crashes
35035 @item maint set catch-demangler-crashes [on|off]
35036 @itemx maint show catch-demangler-crashes
35037 Control whether @value{GDBN} should attempt to catch crashes in the
35038 symbol name demangler. The default is to attempt to catch crashes.
35039 If enabled, the first time a crash is caught, a core file is created,
35040 the offending symbol is displayed and the user is presented with the
35041 option to terminate the current session.
35043 @kindex maint cplus first_component
35044 @item maint cplus first_component @var{name}
35045 Print the first C@t{++} class/namespace component of @var{name}.
35047 @kindex maint cplus namespace
35048 @item maint cplus namespace
35049 Print the list of possible C@t{++} namespaces.
35051 @kindex maint deprecate
35052 @kindex maint undeprecate
35053 @cindex deprecated commands
35054 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35055 @itemx maint undeprecate @var{command}
35056 Deprecate or undeprecate the named @var{command}. Deprecated commands
35057 cause @value{GDBN} to issue a warning when you use them. The optional
35058 argument @var{replacement} says which newer command should be used in
35059 favor of the deprecated one; if it is given, @value{GDBN} will mention
35060 the replacement as part of the warning.
35062 @kindex maint dump-me
35063 @item maint dump-me
35064 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35065 Cause a fatal signal in the debugger and force it to dump its core.
35066 This is supported only on systems which support aborting a program
35067 with the @code{SIGQUIT} signal.
35069 @kindex maint internal-error
35070 @kindex maint internal-warning
35071 @kindex maint demangler-warning
35072 @cindex demangler crashes
35073 @item maint internal-error @r{[}@var{message-text}@r{]}
35074 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35075 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
35077 Cause @value{GDBN} to call the internal function @code{internal_error},
35078 @code{internal_warning} or @code{demangler_warning} and hence behave
35079 as though an internal problem has been detected. In addition to
35080 reporting the internal problem, these functions give the user the
35081 opportunity to either quit @value{GDBN} or (for @code{internal_error}
35082 and @code{internal_warning}) create a core file of the current
35083 @value{GDBN} session.
35085 These commands take an optional parameter @var{message-text} that is
35086 used as the text of the error or warning message.
35088 Here's an example of using @code{internal-error}:
35091 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35092 @dots{}/maint.c:121: internal-error: testing, 1, 2
35093 A problem internal to GDB has been detected. Further
35094 debugging may prove unreliable.
35095 Quit this debugging session? (y or n) @kbd{n}
35096 Create a core file? (y or n) @kbd{n}
35100 @cindex @value{GDBN} internal error
35101 @cindex internal errors, control of @value{GDBN} behavior
35102 @cindex demangler crashes
35104 @kindex maint set internal-error
35105 @kindex maint show internal-error
35106 @kindex maint set internal-warning
35107 @kindex maint show internal-warning
35108 @kindex maint set demangler-warning
35109 @kindex maint show demangler-warning
35110 @item maint set internal-error @var{action} [ask|yes|no]
35111 @itemx maint show internal-error @var{action}
35112 @itemx maint set internal-warning @var{action} [ask|yes|no]
35113 @itemx maint show internal-warning @var{action}
35114 @itemx maint set demangler-warning @var{action} [ask|yes|no]
35115 @itemx maint show demangler-warning @var{action}
35116 When @value{GDBN} reports an internal problem (error or warning) it
35117 gives the user the opportunity to both quit @value{GDBN} and create a
35118 core file of the current @value{GDBN} session. These commands let you
35119 override the default behaviour for each particular @var{action},
35120 described in the table below.
35124 You can specify that @value{GDBN} should always (yes) or never (no)
35125 quit. The default is to ask the user what to do.
35128 You can specify that @value{GDBN} should always (yes) or never (no)
35129 create a core file. The default is to ask the user what to do. Note
35130 that there is no @code{corefile} option for @code{demangler-warning}:
35131 demangler warnings always create a core file and this cannot be
35135 @kindex maint packet
35136 @item maint packet @var{text}
35137 If @value{GDBN} is talking to an inferior via the serial protocol,
35138 then this command sends the string @var{text} to the inferior, and
35139 displays the response packet. @value{GDBN} supplies the initial
35140 @samp{$} character, the terminating @samp{#} character, and the
35143 @kindex maint print architecture
35144 @item maint print architecture @r{[}@var{file}@r{]}
35145 Print the entire architecture configuration. The optional argument
35146 @var{file} names the file where the output goes.
35148 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
35149 @item maint print c-tdesc
35150 Print the target description (@pxref{Target Descriptions}) as
35151 a C source file. By default, the target description is for the current
35152 target, but if the optional argument @var{file} is provided, that file
35153 is used to produce the description. The @var{file} should be an XML
35154 document, of the form described in @ref{Target Description Format}.
35155 The created source file is built into @value{GDBN} when @value{GDBN} is
35156 built again. This command is used by developers after they add or
35157 modify XML target descriptions.
35159 @kindex maint check xml-descriptions
35160 @item maint check xml-descriptions @var{dir}
35161 Check that the target descriptions dynamically created by @value{GDBN}
35162 equal the descriptions created from XML files found in @var{dir}.
35164 @kindex maint print dummy-frames
35165 @item maint print dummy-frames
35166 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35169 (@value{GDBP}) @kbd{b add}
35171 (@value{GDBP}) @kbd{print add(2,3)}
35172 Breakpoint 2, add (a=2, b=3) at @dots{}
35174 The program being debugged stopped while in a function called from GDB.
35176 (@value{GDBP}) @kbd{maint print dummy-frames}
35177 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
35181 Takes an optional file parameter.
35183 @kindex maint print registers
35184 @kindex maint print raw-registers
35185 @kindex maint print cooked-registers
35186 @kindex maint print register-groups
35187 @kindex maint print remote-registers
35188 @item maint print registers @r{[}@var{file}@r{]}
35189 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35190 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35191 @itemx maint print register-groups @r{[}@var{file}@r{]}
35192 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35193 Print @value{GDBN}'s internal register data structures.
35195 The command @code{maint print raw-registers} includes the contents of
35196 the raw register cache; the command @code{maint print
35197 cooked-registers} includes the (cooked) value of all registers,
35198 including registers which aren't available on the target nor visible
35199 to user; the command @code{maint print register-groups} includes the
35200 groups that each register is a member of; and the command @code{maint
35201 print remote-registers} includes the remote target's register numbers
35202 and offsets in the `G' packets.
35204 These commands take an optional parameter, a file name to which to
35205 write the information.
35207 @kindex maint print reggroups
35208 @item maint print reggroups @r{[}@var{file}@r{]}
35209 Print @value{GDBN}'s internal register group data structures. The
35210 optional argument @var{file} tells to what file to write the
35213 The register groups info looks like this:
35216 (@value{GDBP}) @kbd{maint print reggroups}
35229 This command forces @value{GDBN} to flush its internal register cache.
35231 @kindex maint print objfiles
35232 @cindex info for known object files
35233 @item maint print objfiles @r{[}@var{regexp}@r{]}
35234 Print a dump of all known object files.
35235 If @var{regexp} is specified, only print object files whose names
35236 match @var{regexp}. For each object file, this command prints its name,
35237 address in memory, and all of its psymtabs and symtabs.
35239 @kindex maint print user-registers
35240 @cindex user registers
35241 @item maint print user-registers
35242 List all currently available @dfn{user registers}. User registers
35243 typically provide alternate names for actual hardware registers. They
35244 include the four ``standard'' registers @code{$fp}, @code{$pc},
35245 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
35246 registers can be used in expressions in the same way as the canonical
35247 register names, but only the latter are listed by the @code{info
35248 registers} and @code{maint print registers} commands.
35250 @kindex maint print section-scripts
35251 @cindex info for known .debug_gdb_scripts-loaded scripts
35252 @item maint print section-scripts [@var{regexp}]
35253 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35254 If @var{regexp} is specified, only print scripts loaded by object files
35255 matching @var{regexp}.
35256 For each script, this command prints its name as specified in the objfile,
35257 and the full path if known.
35258 @xref{dotdebug_gdb_scripts section}.
35260 @kindex maint print statistics
35261 @cindex bcache statistics
35262 @item maint print statistics
35263 This command prints, for each object file in the program, various data
35264 about that object file followed by the byte cache (@dfn{bcache})
35265 statistics for the object file. The objfile data includes the number
35266 of minimal, partial, full, and stabs symbols, the number of types
35267 defined by the objfile, the number of as yet unexpanded psym tables,
35268 the number of line tables and string tables, and the amount of memory
35269 used by the various tables. The bcache statistics include the counts,
35270 sizes, and counts of duplicates of all and unique objects, max,
35271 average, and median entry size, total memory used and its overhead and
35272 savings, and various measures of the hash table size and chain
35275 @kindex maint print target-stack
35276 @cindex target stack description
35277 @item maint print target-stack
35278 A @dfn{target} is an interface between the debugger and a particular
35279 kind of file or process. Targets can be stacked in @dfn{strata},
35280 so that more than one target can potentially respond to a request.
35281 In particular, memory accesses will walk down the stack of targets
35282 until they find a target that is interested in handling that particular
35285 This command prints a short description of each layer that was pushed on
35286 the @dfn{target stack}, starting from the top layer down to the bottom one.
35288 @kindex maint print type
35289 @cindex type chain of a data type
35290 @item maint print type @var{expr}
35291 Print the type chain for a type specified by @var{expr}. The argument
35292 can be either a type name or a symbol. If it is a symbol, the type of
35293 that symbol is described. The type chain produced by this command is
35294 a recursive definition of the data type as stored in @value{GDBN}'s
35295 data structures, including its flags and contained types.
35297 @kindex maint selftest
35299 @item maint selftest @r{[}@var{filter}@r{]}
35300 Run any self tests that were compiled in to @value{GDBN}. This will
35301 print a message showing how many tests were run, and how many failed.
35302 If a @var{filter} is passed, only the tests with @var{filter} in their
35305 @kindex "maint info selftests"
35307 @item maint info selftests
35308 List the selftests compiled in to @value{GDBN}.
35310 @kindex maint set dwarf always-disassemble
35311 @kindex maint show dwarf always-disassemble
35312 @item maint set dwarf always-disassemble
35313 @item maint show dwarf always-disassemble
35314 Control the behavior of @code{info address} when using DWARF debugging
35317 The default is @code{off}, which means that @value{GDBN} should try to
35318 describe a variable's location in an easily readable format. When
35319 @code{on}, @value{GDBN} will instead display the DWARF location
35320 expression in an assembly-like format. Note that some locations are
35321 too complex for @value{GDBN} to describe simply; in this case you will
35322 always see the disassembly form.
35324 Here is an example of the resulting disassembly:
35327 (gdb) info addr argc
35328 Symbol "argc" is a complex DWARF expression:
35332 For more information on these expressions, see
35333 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35335 @kindex maint set dwarf max-cache-age
35336 @kindex maint show dwarf max-cache-age
35337 @item maint set dwarf max-cache-age
35338 @itemx maint show dwarf max-cache-age
35339 Control the DWARF compilation unit cache.
35341 @cindex DWARF compilation units cache
35342 In object files with inter-compilation-unit references, such as those
35343 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
35344 reader needs to frequently refer to previously read compilation units.
35345 This setting controls how long a compilation unit will remain in the
35346 cache if it is not referenced. A higher limit means that cached
35347 compilation units will be stored in memory longer, and more total
35348 memory will be used. Setting it to zero disables caching, which will
35349 slow down @value{GDBN} startup, but reduce memory consumption.
35351 @kindex maint set profile
35352 @kindex maint show profile
35353 @cindex profiling GDB
35354 @item maint set profile
35355 @itemx maint show profile
35356 Control profiling of @value{GDBN}.
35358 Profiling will be disabled until you use the @samp{maint set profile}
35359 command to enable it. When you enable profiling, the system will begin
35360 collecting timing and execution count data; when you disable profiling or
35361 exit @value{GDBN}, the results will be written to a log file. Remember that
35362 if you use profiling, @value{GDBN} will overwrite the profiling log file
35363 (often called @file{gmon.out}). If you have a record of important profiling
35364 data in a @file{gmon.out} file, be sure to move it to a safe location.
35366 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35367 compiled with the @samp{-pg} compiler option.
35369 @kindex maint set show-debug-regs
35370 @kindex maint show show-debug-regs
35371 @cindex hardware debug registers
35372 @item maint set show-debug-regs
35373 @itemx maint show show-debug-regs
35374 Control whether to show variables that mirror the hardware debug
35375 registers. Use @code{on} to enable, @code{off} to disable. If
35376 enabled, the debug registers values are shown when @value{GDBN} inserts or
35377 removes a hardware breakpoint or watchpoint, and when the inferior
35378 triggers a hardware-assisted breakpoint or watchpoint.
35380 @kindex maint set show-all-tib
35381 @kindex maint show show-all-tib
35382 @item maint set show-all-tib
35383 @itemx maint show show-all-tib
35384 Control whether to show all non zero areas within a 1k block starting
35385 at thread local base, when using the @samp{info w32 thread-information-block}
35388 @kindex maint set target-async
35389 @kindex maint show target-async
35390 @item maint set target-async
35391 @itemx maint show target-async
35392 This controls whether @value{GDBN} targets operate in synchronous or
35393 asynchronous mode (@pxref{Background Execution}). Normally the
35394 default is asynchronous, if it is available; but this can be changed
35395 to more easily debug problems occurring only in synchronous mode.
35397 @kindex maint set target-non-stop @var{mode} [on|off|auto]
35398 @kindex maint show target-non-stop
35399 @item maint set target-non-stop
35400 @itemx maint show target-non-stop
35402 This controls whether @value{GDBN} targets always operate in non-stop
35403 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
35404 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
35405 if supported by the target.
35408 @item maint set target-non-stop auto
35409 This is the default mode. @value{GDBN} controls the target in
35410 non-stop mode if the target supports it.
35412 @item maint set target-non-stop on
35413 @value{GDBN} controls the target in non-stop mode even if the target
35414 does not indicate support.
35416 @item maint set target-non-stop off
35417 @value{GDBN} does not control the target in non-stop mode even if the
35418 target supports it.
35421 @kindex maint set per-command
35422 @kindex maint show per-command
35423 @item maint set per-command
35424 @itemx maint show per-command
35425 @cindex resources used by commands
35427 @value{GDBN} can display the resources used by each command.
35428 This is useful in debugging performance problems.
35431 @item maint set per-command space [on|off]
35432 @itemx maint show per-command space
35433 Enable or disable the printing of the memory used by GDB for each command.
35434 If enabled, @value{GDBN} will display how much memory each command
35435 took, following the command's own output.
35436 This can also be requested by invoking @value{GDBN} with the
35437 @option{--statistics} command-line switch (@pxref{Mode Options}).
35439 @item maint set per-command time [on|off]
35440 @itemx maint show per-command time
35441 Enable or disable the printing of the execution time of @value{GDBN}
35443 If enabled, @value{GDBN} will display how much time it
35444 took to execute each command, following the command's own output.
35445 Both CPU time and wallclock time are printed.
35446 Printing both is useful when trying to determine whether the cost is
35447 CPU or, e.g., disk/network latency.
35448 Note that the CPU time printed is for @value{GDBN} only, it does not include
35449 the execution time of the inferior because there's no mechanism currently
35450 to compute how much time was spent by @value{GDBN} and how much time was
35451 spent by the program been debugged.
35452 This can also be requested by invoking @value{GDBN} with the
35453 @option{--statistics} command-line switch (@pxref{Mode Options}).
35455 @item maint set per-command symtab [on|off]
35456 @itemx maint show per-command symtab
35457 Enable or disable the printing of basic symbol table statistics
35459 If enabled, @value{GDBN} will display the following information:
35463 number of symbol tables
35465 number of primary symbol tables
35467 number of blocks in the blockvector
35471 @kindex maint space
35472 @cindex memory used by commands
35473 @item maint space @var{value}
35474 An alias for @code{maint set per-command space}.
35475 A non-zero value enables it, zero disables it.
35478 @cindex time of command execution
35479 @item maint time @var{value}
35480 An alias for @code{maint set per-command time}.
35481 A non-zero value enables it, zero disables it.
35483 @kindex maint translate-address
35484 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35485 Find the symbol stored at the location specified by the address
35486 @var{addr} and an optional section name @var{section}. If found,
35487 @value{GDBN} prints the name of the closest symbol and an offset from
35488 the symbol's location to the specified address. This is similar to
35489 the @code{info address} command (@pxref{Symbols}), except that this
35490 command also allows to find symbols in other sections.
35492 If section was not specified, the section in which the symbol was found
35493 is also printed. For dynamically linked executables, the name of
35494 executable or shared library containing the symbol is printed as well.
35498 The following command is useful for non-interactive invocations of
35499 @value{GDBN}, such as in the test suite.
35502 @item set watchdog @var{nsec}
35503 @kindex set watchdog
35504 @cindex watchdog timer
35505 @cindex timeout for commands
35506 Set the maximum number of seconds @value{GDBN} will wait for the
35507 target operation to finish. If this time expires, @value{GDBN}
35508 reports and error and the command is aborted.
35510 @item show watchdog
35511 Show the current setting of the target wait timeout.
35514 @node Remote Protocol
35515 @appendix @value{GDBN} Remote Serial Protocol
35520 * Stop Reply Packets::
35521 * General Query Packets::
35522 * Architecture-Specific Protocol Details::
35523 * Tracepoint Packets::
35524 * Host I/O Packets::
35526 * Notification Packets::
35527 * Remote Non-Stop::
35528 * Packet Acknowledgment::
35530 * File-I/O Remote Protocol Extension::
35531 * Library List Format::
35532 * Library List Format for SVR4 Targets::
35533 * Memory Map Format::
35534 * Thread List Format::
35535 * Traceframe Info Format::
35536 * Branch Trace Format::
35537 * Branch Trace Configuration Format::
35543 There may be occasions when you need to know something about the
35544 protocol---for example, if there is only one serial port to your target
35545 machine, you might want your program to do something special if it
35546 recognizes a packet meant for @value{GDBN}.
35548 In the examples below, @samp{->} and @samp{<-} are used to indicate
35549 transmitted and received data, respectively.
35551 @cindex protocol, @value{GDBN} remote serial
35552 @cindex serial protocol, @value{GDBN} remote
35553 @cindex remote serial protocol
35554 All @value{GDBN} commands and responses (other than acknowledgments
35555 and notifications, see @ref{Notification Packets}) are sent as a
35556 @var{packet}. A @var{packet} is introduced with the character
35557 @samp{$}, the actual @var{packet-data}, and the terminating character
35558 @samp{#} followed by a two-digit @var{checksum}:
35561 @code{$}@var{packet-data}@code{#}@var{checksum}
35565 @cindex checksum, for @value{GDBN} remote
35567 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35568 characters between the leading @samp{$} and the trailing @samp{#} (an
35569 eight bit unsigned checksum).
35571 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35572 specification also included an optional two-digit @var{sequence-id}:
35575 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35578 @cindex sequence-id, for @value{GDBN} remote
35580 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35581 has never output @var{sequence-id}s. Stubs that handle packets added
35582 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35584 When either the host or the target machine receives a packet, the first
35585 response expected is an acknowledgment: either @samp{+} (to indicate
35586 the package was received correctly) or @samp{-} (to request
35590 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35595 The @samp{+}/@samp{-} acknowledgments can be disabled
35596 once a connection is established.
35597 @xref{Packet Acknowledgment}, for details.
35599 The host (@value{GDBN}) sends @var{command}s, and the target (the
35600 debugging stub incorporated in your program) sends a @var{response}. In
35601 the case of step and continue @var{command}s, the response is only sent
35602 when the operation has completed, and the target has again stopped all
35603 threads in all attached processes. This is the default all-stop mode
35604 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35605 execution mode; see @ref{Remote Non-Stop}, for details.
35607 @var{packet-data} consists of a sequence of characters with the
35608 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35611 @cindex remote protocol, field separator
35612 Fields within the packet should be separated using @samp{,} @samp{;} or
35613 @samp{:}. Except where otherwise noted all numbers are represented in
35614 @sc{hex} with leading zeros suppressed.
35616 Implementors should note that prior to @value{GDBN} 5.0, the character
35617 @samp{:} could not appear as the third character in a packet (as it
35618 would potentially conflict with the @var{sequence-id}).
35620 @cindex remote protocol, binary data
35621 @anchor{Binary Data}
35622 Binary data in most packets is encoded either as two hexadecimal
35623 digits per byte of binary data. This allowed the traditional remote
35624 protocol to work over connections which were only seven-bit clean.
35625 Some packets designed more recently assume an eight-bit clean
35626 connection, and use a more efficient encoding to send and receive
35629 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35630 as an escape character. Any escaped byte is transmitted as the escape
35631 character followed by the original character XORed with @code{0x20}.
35632 For example, the byte @code{0x7d} would be transmitted as the two
35633 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35634 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35635 @samp{@}}) must always be escaped. Responses sent by the stub
35636 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35637 is not interpreted as the start of a run-length encoded sequence
35640 Response @var{data} can be run-length encoded to save space.
35641 Run-length encoding replaces runs of identical characters with one
35642 instance of the repeated character, followed by a @samp{*} and a
35643 repeat count. The repeat count is itself sent encoded, to avoid
35644 binary characters in @var{data}: a value of @var{n} is sent as
35645 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35646 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35647 code 32) for a repeat count of 3. (This is because run-length
35648 encoding starts to win for counts 3 or more.) Thus, for example,
35649 @samp{0* } is a run-length encoding of ``0000'': the space character
35650 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35653 The printable characters @samp{#} and @samp{$} or with a numeric value
35654 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35655 seven repeats (@samp{$}) can be expanded using a repeat count of only
35656 five (@samp{"}). For example, @samp{00000000} can be encoded as
35659 The error response returned for some packets includes a two character
35660 error number. That number is not well defined.
35662 @cindex empty response, for unsupported packets
35663 For any @var{command} not supported by the stub, an empty response
35664 (@samp{$#00}) should be returned. That way it is possible to extend the
35665 protocol. A newer @value{GDBN} can tell if a packet is supported based
35668 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35669 commands for register access, and the @samp{m} and @samp{M} commands
35670 for memory access. Stubs that only control single-threaded targets
35671 can implement run control with the @samp{c} (continue), and @samp{s}
35672 (step) commands. Stubs that support multi-threading targets should
35673 support the @samp{vCont} command. All other commands are optional.
35678 The following table provides a complete list of all currently defined
35679 @var{command}s and their corresponding response @var{data}.
35680 @xref{File-I/O Remote Protocol Extension}, for details about the File
35681 I/O extension of the remote protocol.
35683 Each packet's description has a template showing the packet's overall
35684 syntax, followed by an explanation of the packet's meaning. We
35685 include spaces in some of the templates for clarity; these are not
35686 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35687 separate its components. For example, a template like @samp{foo
35688 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35689 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35690 @var{baz}. @value{GDBN} does not transmit a space character between the
35691 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35694 @cindex @var{thread-id}, in remote protocol
35695 @anchor{thread-id syntax}
35696 Several packets and replies include a @var{thread-id} field to identify
35697 a thread. Normally these are positive numbers with a target-specific
35698 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35699 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35702 In addition, the remote protocol supports a multiprocess feature in
35703 which the @var{thread-id} syntax is extended to optionally include both
35704 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35705 The @var{pid} (process) and @var{tid} (thread) components each have the
35706 format described above: a positive number with target-specific
35707 interpretation formatted as a big-endian hex string, literal @samp{-1}
35708 to indicate all processes or threads (respectively), or @samp{0} to
35709 indicate an arbitrary process or thread. Specifying just a process, as
35710 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35711 error to specify all processes but a specific thread, such as
35712 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35713 for those packets and replies explicitly documented to include a process
35714 ID, rather than a @var{thread-id}.
35716 The multiprocess @var{thread-id} syntax extensions are only used if both
35717 @value{GDBN} and the stub report support for the @samp{multiprocess}
35718 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35721 Note that all packet forms beginning with an upper- or lower-case
35722 letter, other than those described here, are reserved for future use.
35724 Here are the packet descriptions.
35729 @cindex @samp{!} packet
35730 @anchor{extended mode}
35731 Enable extended mode. In extended mode, the remote server is made
35732 persistent. The @samp{R} packet is used to restart the program being
35738 The remote target both supports and has enabled extended mode.
35742 @cindex @samp{?} packet
35744 Indicate the reason the target halted. The reply is the same as for
35745 step and continue. This packet has a special interpretation when the
35746 target is in non-stop mode; see @ref{Remote Non-Stop}.
35749 @xref{Stop Reply Packets}, for the reply specifications.
35751 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35752 @cindex @samp{A} packet
35753 Initialized @code{argv[]} array passed into program. @var{arglen}
35754 specifies the number of bytes in the hex encoded byte stream
35755 @var{arg}. See @code{gdbserver} for more details.
35760 The arguments were set.
35766 @cindex @samp{b} packet
35767 (Don't use this packet; its behavior is not well-defined.)
35768 Change the serial line speed to @var{baud}.
35770 JTC: @emph{When does the transport layer state change? When it's
35771 received, or after the ACK is transmitted. In either case, there are
35772 problems if the command or the acknowledgment packet is dropped.}
35774 Stan: @emph{If people really wanted to add something like this, and get
35775 it working for the first time, they ought to modify ser-unix.c to send
35776 some kind of out-of-band message to a specially-setup stub and have the
35777 switch happen "in between" packets, so that from remote protocol's point
35778 of view, nothing actually happened.}
35780 @item B @var{addr},@var{mode}
35781 @cindex @samp{B} packet
35782 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35783 breakpoint at @var{addr}.
35785 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35786 (@pxref{insert breakpoint or watchpoint packet}).
35788 @cindex @samp{bc} packet
35791 Backward continue. Execute the target system in reverse. No parameter.
35792 @xref{Reverse Execution}, for more information.
35795 @xref{Stop Reply Packets}, for the reply specifications.
35797 @cindex @samp{bs} packet
35800 Backward single step. Execute one instruction in reverse. No parameter.
35801 @xref{Reverse Execution}, for more information.
35804 @xref{Stop Reply Packets}, for the reply specifications.
35806 @item c @r{[}@var{addr}@r{]}
35807 @cindex @samp{c} packet
35808 Continue at @var{addr}, which is the address to resume. If @var{addr}
35809 is omitted, resume at current address.
35811 This packet is deprecated for multi-threading support. @xref{vCont
35815 @xref{Stop Reply Packets}, for the reply specifications.
35817 @item C @var{sig}@r{[};@var{addr}@r{]}
35818 @cindex @samp{C} packet
35819 Continue with signal @var{sig} (hex signal number). If
35820 @samp{;@var{addr}} is omitted, resume at same address.
35822 This packet is deprecated for multi-threading support. @xref{vCont
35826 @xref{Stop Reply Packets}, for the reply specifications.
35829 @cindex @samp{d} packet
35832 Don't use this packet; instead, define a general set packet
35833 (@pxref{General Query Packets}).
35837 @cindex @samp{D} packet
35838 The first form of the packet is used to detach @value{GDBN} from the
35839 remote system. It is sent to the remote target
35840 before @value{GDBN} disconnects via the @code{detach} command.
35842 The second form, including a process ID, is used when multiprocess
35843 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35844 detach only a specific process. The @var{pid} is specified as a
35845 big-endian hex string.
35855 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35856 @cindex @samp{F} packet
35857 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35858 This is part of the File-I/O protocol extension. @xref{File-I/O
35859 Remote Protocol Extension}, for the specification.
35862 @anchor{read registers packet}
35863 @cindex @samp{g} packet
35864 Read general registers.
35868 @item @var{XX@dots{}}
35869 Each byte of register data is described by two hex digits. The bytes
35870 with the register are transmitted in target byte order. The size of
35871 each register and their position within the @samp{g} packet are
35872 determined by the @value{GDBN} internal gdbarch functions
35873 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
35875 When reading registers from a trace frame (@pxref{Analyze Collected
35876 Data,,Using the Collected Data}), the stub may also return a string of
35877 literal @samp{x}'s in place of the register data digits, to indicate
35878 that the corresponding register has not been collected, thus its value
35879 is unavailable. For example, for an architecture with 4 registers of
35880 4 bytes each, the following reply indicates to @value{GDBN} that
35881 registers 0 and 2 have not been collected, while registers 1 and 3
35882 have been collected, and both have zero value:
35886 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35893 @item G @var{XX@dots{}}
35894 @cindex @samp{G} packet
35895 Write general registers. @xref{read registers packet}, for a
35896 description of the @var{XX@dots{}} data.
35906 @item H @var{op} @var{thread-id}
35907 @cindex @samp{H} packet
35908 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35909 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
35910 should be @samp{c} for step and continue operations (note that this
35911 is deprecated, supporting the @samp{vCont} command is a better
35912 option), and @samp{g} for other operations. The thread designator
35913 @var{thread-id} has the format and interpretation described in
35914 @ref{thread-id syntax}.
35925 @c 'H': How restrictive (or permissive) is the thread model. If a
35926 @c thread is selected and stopped, are other threads allowed
35927 @c to continue to execute? As I mentioned above, I think the
35928 @c semantics of each command when a thread is selected must be
35929 @c described. For example:
35931 @c 'g': If the stub supports threads and a specific thread is
35932 @c selected, returns the register block from that thread;
35933 @c otherwise returns current registers.
35935 @c 'G' If the stub supports threads and a specific thread is
35936 @c selected, sets the registers of the register block of
35937 @c that thread; otherwise sets current registers.
35939 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35940 @anchor{cycle step packet}
35941 @cindex @samp{i} packet
35942 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35943 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35944 step starting at that address.
35947 @cindex @samp{I} packet
35948 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35952 @cindex @samp{k} packet
35955 The exact effect of this packet is not specified.
35957 For a bare-metal target, it may power cycle or reset the target
35958 system. For that reason, the @samp{k} packet has no reply.
35960 For a single-process target, it may kill that process if possible.
35962 A multiple-process target may choose to kill just one process, or all
35963 that are under @value{GDBN}'s control. For more precise control, use
35964 the vKill packet (@pxref{vKill packet}).
35966 If the target system immediately closes the connection in response to
35967 @samp{k}, @value{GDBN} does not consider the lack of packet
35968 acknowledgment to be an error, and assumes the kill was successful.
35970 If connected using @kbd{target extended-remote}, and the target does
35971 not close the connection in response to a kill request, @value{GDBN}
35972 probes the target state as if a new connection was opened
35973 (@pxref{? packet}).
35975 @item m @var{addr},@var{length}
35976 @cindex @samp{m} packet
35977 Read @var{length} addressable memory units starting at address @var{addr}
35978 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
35979 any particular boundary.
35981 The stub need not use any particular size or alignment when gathering
35982 data from memory for the response; even if @var{addr} is word-aligned
35983 and @var{length} is a multiple of the word size, the stub is free to
35984 use byte accesses, or not. For this reason, this packet may not be
35985 suitable for accessing memory-mapped I/O devices.
35986 @cindex alignment of remote memory accesses
35987 @cindex size of remote memory accesses
35988 @cindex memory, alignment and size of remote accesses
35992 @item @var{XX@dots{}}
35993 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
35994 The reply may contain fewer addressable memory units than requested if the
35995 server was able to read only part of the region of memory.
36000 @item M @var{addr},@var{length}:@var{XX@dots{}}
36001 @cindex @samp{M} packet
36002 Write @var{length} addressable memory units starting at address @var{addr}
36003 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
36004 byte is transmitted as a two-digit hexadecimal number.
36011 for an error (this includes the case where only part of the data was
36016 @cindex @samp{p} packet
36017 Read the value of register @var{n}; @var{n} is in hex.
36018 @xref{read registers packet}, for a description of how the returned
36019 register value is encoded.
36023 @item @var{XX@dots{}}
36024 the register's value
36028 Indicating an unrecognized @var{query}.
36031 @item P @var{n@dots{}}=@var{r@dots{}}
36032 @anchor{write register packet}
36033 @cindex @samp{P} packet
36034 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36035 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36036 digits for each byte in the register (target byte order).
36046 @item q @var{name} @var{params}@dots{}
36047 @itemx Q @var{name} @var{params}@dots{}
36048 @cindex @samp{q} packet
36049 @cindex @samp{Q} packet
36050 General query (@samp{q}) and set (@samp{Q}). These packets are
36051 described fully in @ref{General Query Packets}.
36054 @cindex @samp{r} packet
36055 Reset the entire system.
36057 Don't use this packet; use the @samp{R} packet instead.
36060 @cindex @samp{R} packet
36061 Restart the program being debugged. The @var{XX}, while needed, is ignored.
36062 This packet is only available in extended mode (@pxref{extended mode}).
36064 The @samp{R} packet has no reply.
36066 @item s @r{[}@var{addr}@r{]}
36067 @cindex @samp{s} packet
36068 Single step, resuming at @var{addr}. If
36069 @var{addr} is omitted, resume at same address.
36071 This packet is deprecated for multi-threading support. @xref{vCont
36075 @xref{Stop Reply Packets}, for the reply specifications.
36077 @item S @var{sig}@r{[};@var{addr}@r{]}
36078 @anchor{step with signal packet}
36079 @cindex @samp{S} packet
36080 Step with signal. This is analogous to the @samp{C} packet, but
36081 requests a single-step, rather than a normal resumption of execution.
36083 This packet is deprecated for multi-threading support. @xref{vCont
36087 @xref{Stop Reply Packets}, for the reply specifications.
36089 @item t @var{addr}:@var{PP},@var{MM}
36090 @cindex @samp{t} packet
36091 Search backwards starting at address @var{addr} for a match with pattern
36092 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
36093 There must be at least 3 digits in @var{addr}.
36095 @item T @var{thread-id}
36096 @cindex @samp{T} packet
36097 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36102 thread is still alive
36108 Packets starting with @samp{v} are identified by a multi-letter name,
36109 up to the first @samp{;} or @samp{?} (or the end of the packet).
36111 @item vAttach;@var{pid}
36112 @cindex @samp{vAttach} packet
36113 Attach to a new process with the specified process ID @var{pid}.
36114 The process ID is a
36115 hexadecimal integer identifying the process. In all-stop mode, all
36116 threads in the attached process are stopped; in non-stop mode, it may be
36117 attached without being stopped if that is supported by the target.
36119 @c In non-stop mode, on a successful vAttach, the stub should set the
36120 @c current thread to a thread of the newly-attached process. After
36121 @c attaching, GDB queries for the attached process's thread ID with qC.
36122 @c Also note that, from a user perspective, whether or not the
36123 @c target is stopped on attach in non-stop mode depends on whether you
36124 @c use the foreground or background version of the attach command, not
36125 @c on what vAttach does; GDB does the right thing with respect to either
36126 @c stopping or restarting threads.
36128 This packet is only available in extended mode (@pxref{extended mode}).
36134 @item @r{Any stop packet}
36135 for success in all-stop mode (@pxref{Stop Reply Packets})
36137 for success in non-stop mode (@pxref{Remote Non-Stop})
36140 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36141 @cindex @samp{vCont} packet
36142 @anchor{vCont packet}
36143 Resume the inferior, specifying different actions for each thread.
36145 For each inferior thread, the leftmost action with a matching
36146 @var{thread-id} is applied. Threads that don't match any action
36147 remain in their current state. Thread IDs are specified using the
36148 syntax described in @ref{thread-id syntax}. If multiprocess
36149 extensions (@pxref{multiprocess extensions}) are supported, actions
36150 can be specified to match all threads in a process by using the
36151 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
36152 @var{thread-id} matches all threads. Specifying no actions is an
36155 Currently supported actions are:
36161 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36165 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36168 @item r @var{start},@var{end}
36169 Step once, and then keep stepping as long as the thread stops at
36170 addresses between @var{start} (inclusive) and @var{end} (exclusive).
36171 The remote stub reports a stop reply when either the thread goes out
36172 of the range or is stopped due to an unrelated reason, such as hitting
36173 a breakpoint. @xref{range stepping}.
36175 If the range is empty (@var{start} == @var{end}), then the action
36176 becomes equivalent to the @samp{s} action. In other words,
36177 single-step once, and report the stop (even if the stepped instruction
36178 jumps to @var{start}).
36180 (A stop reply may be sent at any point even if the PC is still within
36181 the stepping range; for example, it is valid to implement this packet
36182 in a degenerate way as a single instruction step operation.)
36186 The optional argument @var{addr} normally associated with the
36187 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36188 not supported in @samp{vCont}.
36190 The @samp{t} action is only relevant in non-stop mode
36191 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36192 A stop reply should be generated for any affected thread not already stopped.
36193 When a thread is stopped by means of a @samp{t} action,
36194 the corresponding stop reply should indicate that the thread has stopped with
36195 signal @samp{0}, regardless of whether the target uses some other signal
36196 as an implementation detail.
36198 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
36199 @samp{r} actions for threads that are already running. Conversely,
36200 the server must ignore @samp{t} actions for threads that are already
36203 @emph{Note:} In non-stop mode, a thread is considered running until
36204 @value{GDBN} acknowleges an asynchronous stop notification for it with
36205 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
36207 The stub must support @samp{vCont} if it reports support for
36208 multiprocess extensions (@pxref{multiprocess extensions}).
36211 @xref{Stop Reply Packets}, for the reply specifications.
36214 @cindex @samp{vCont?} packet
36215 Request a list of actions supported by the @samp{vCont} packet.
36219 @item vCont@r{[};@var{action}@dots{}@r{]}
36220 The @samp{vCont} packet is supported. Each @var{action} is a supported
36221 command in the @samp{vCont} packet.
36223 The @samp{vCont} packet is not supported.
36226 @anchor{vCtrlC packet}
36228 @cindex @samp{vCtrlC} packet
36229 Interrupt remote target as if a control-C was pressed on the remote
36230 terminal. This is the equivalent to reacting to the @code{^C}
36231 (@samp{\003}, the control-C character) character in all-stop mode
36232 while the target is running, except this works in non-stop mode.
36233 @xref{interrupting remote targets}, for more info on the all-stop
36244 @item vFile:@var{operation}:@var{parameter}@dots{}
36245 @cindex @samp{vFile} packet
36246 Perform a file operation on the target system. For details,
36247 see @ref{Host I/O Packets}.
36249 @item vFlashErase:@var{addr},@var{length}
36250 @cindex @samp{vFlashErase} packet
36251 Direct the stub to erase @var{length} bytes of flash starting at
36252 @var{addr}. The region may enclose any number of flash blocks, but
36253 its start and end must fall on block boundaries, as indicated by the
36254 flash block size appearing in the memory map (@pxref{Memory Map
36255 Format}). @value{GDBN} groups flash memory programming operations
36256 together, and sends a @samp{vFlashDone} request after each group; the
36257 stub is allowed to delay erase operation until the @samp{vFlashDone}
36258 packet is received.
36268 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36269 @cindex @samp{vFlashWrite} packet
36270 Direct the stub to write data to flash address @var{addr}. The data
36271 is passed in binary form using the same encoding as for the @samp{X}
36272 packet (@pxref{Binary Data}). The memory ranges specified by
36273 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36274 not overlap, and must appear in order of increasing addresses
36275 (although @samp{vFlashErase} packets for higher addresses may already
36276 have been received; the ordering is guaranteed only between
36277 @samp{vFlashWrite} packets). If a packet writes to an address that was
36278 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36279 target-specific method, the results are unpredictable.
36287 for vFlashWrite addressing non-flash memory
36293 @cindex @samp{vFlashDone} packet
36294 Indicate to the stub that flash programming operation is finished.
36295 The stub is permitted to delay or batch the effects of a group of
36296 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36297 @samp{vFlashDone} packet is received. The contents of the affected
36298 regions of flash memory are unpredictable until the @samp{vFlashDone}
36299 request is completed.
36301 @item vKill;@var{pid}
36302 @cindex @samp{vKill} packet
36303 @anchor{vKill packet}
36304 Kill the process with the specified process ID @var{pid}, which is a
36305 hexadecimal integer identifying the process. This packet is used in
36306 preference to @samp{k} when multiprocess protocol extensions are
36307 supported; see @ref{multiprocess extensions}.
36317 @item vMustReplyEmpty
36318 @cindex @samp{vMustReplyEmpty} packet
36319 The correct reply to an unknown @samp{v} packet is to return the empty
36320 string, however, some older versions of @command{gdbserver} would
36321 incorrectly return @samp{OK} for unknown @samp{v} packets.
36323 The @samp{vMustReplyEmpty} is used as a feature test to check how
36324 @command{gdbserver} handles unknown packets, it is important that this
36325 packet be handled in the same way as other unknown @samp{v} packets.
36326 If this packet is handled differently to other unknown @samp{v}
36327 packets then it is possile that @value{GDBN} may run into problems in
36328 other areas, specifically around use of @samp{vFile:setfs:}.
36330 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36331 @cindex @samp{vRun} packet
36332 Run the program @var{filename}, passing it each @var{argument} on its
36333 command line. The file and arguments are hex-encoded strings. If
36334 @var{filename} is an empty string, the stub may use a default program
36335 (e.g.@: the last program run). The program is created in the stopped
36338 @c FIXME: What about non-stop mode?
36340 This packet is only available in extended mode (@pxref{extended mode}).
36346 @item @r{Any stop packet}
36347 for success (@pxref{Stop Reply Packets})
36351 @cindex @samp{vStopped} packet
36352 @xref{Notification Packets}.
36354 @item X @var{addr},@var{length}:@var{XX@dots{}}
36356 @cindex @samp{X} packet
36357 Write data to memory, where the data is transmitted in binary.
36358 Memory is specified by its address @var{addr} and number of addressable memory
36359 units @var{length} (@pxref{addressable memory unit});
36360 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36370 @item z @var{type},@var{addr},@var{kind}
36371 @itemx Z @var{type},@var{addr},@var{kind}
36372 @anchor{insert breakpoint or watchpoint packet}
36373 @cindex @samp{z} packet
36374 @cindex @samp{Z} packets
36375 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36376 watchpoint starting at address @var{address} of kind @var{kind}.
36378 Each breakpoint and watchpoint packet @var{type} is documented
36381 @emph{Implementation notes: A remote target shall return an empty string
36382 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36383 remote target shall support either both or neither of a given
36384 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36385 avoid potential problems with duplicate packets, the operations should
36386 be implemented in an idempotent way.}
36388 @item z0,@var{addr},@var{kind}
36389 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36390 @cindex @samp{z0} packet
36391 @cindex @samp{Z0} packet
36392 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
36393 @var{addr} of type @var{kind}.
36395 A software breakpoint is implemented by replacing the instruction at
36396 @var{addr} with a software breakpoint or trap instruction. The
36397 @var{kind} is target-specific and typically indicates the size of the
36398 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
36399 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36400 architectures have additional meanings for @var{kind}
36401 (@pxref{Architecture-Specific Protocol Details}); if no
36402 architecture-specific value is being used, it should be @samp{0}.
36403 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
36404 conditional expressions in bytecode form that should be evaluated on
36405 the target's side. These are the conditions that should be taken into
36406 consideration when deciding if the breakpoint trigger should be
36407 reported back to @value{GDBN}.
36409 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
36410 for how to best report a software breakpoint event to @value{GDBN}.
36412 The @var{cond_list} parameter is comprised of a series of expressions,
36413 concatenated without separators. Each expression has the following form:
36417 @item X @var{len},@var{expr}
36418 @var{len} is the length of the bytecode expression and @var{expr} is the
36419 actual conditional expression in bytecode form.
36423 The optional @var{cmd_list} parameter introduces commands that may be
36424 run on the target, rather than being reported back to @value{GDBN}.
36425 The parameter starts with a numeric flag @var{persist}; if the flag is
36426 nonzero, then the breakpoint may remain active and the commands
36427 continue to be run even when @value{GDBN} disconnects from the target.
36428 Following this flag is a series of expressions concatenated with no
36429 separators. Each expression has the following form:
36433 @item X @var{len},@var{expr}
36434 @var{len} is the length of the bytecode expression and @var{expr} is the
36435 actual commands expression in bytecode form.
36439 @emph{Implementation note: It is possible for a target to copy or move
36440 code that contains software breakpoints (e.g., when implementing
36441 overlays). The behavior of this packet, in the presence of such a
36442 target, is not defined.}
36454 @item z1,@var{addr},@var{kind}
36455 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36456 @cindex @samp{z1} packet
36457 @cindex @samp{Z1} packet
36458 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36459 address @var{addr}.
36461 A hardware breakpoint is implemented using a mechanism that is not
36462 dependent on being able to modify the target's memory. The
36463 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
36464 same meaning as in @samp{Z0} packets.
36466 @emph{Implementation note: A hardware breakpoint is not affected by code
36479 @item z2,@var{addr},@var{kind}
36480 @itemx Z2,@var{addr},@var{kind}
36481 @cindex @samp{z2} packet
36482 @cindex @samp{Z2} packet
36483 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36484 The number of bytes to watch is specified by @var{kind}.
36496 @item z3,@var{addr},@var{kind}
36497 @itemx Z3,@var{addr},@var{kind}
36498 @cindex @samp{z3} packet
36499 @cindex @samp{Z3} packet
36500 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36501 The number of bytes to watch is specified by @var{kind}.
36513 @item z4,@var{addr},@var{kind}
36514 @itemx Z4,@var{addr},@var{kind}
36515 @cindex @samp{z4} packet
36516 @cindex @samp{Z4} packet
36517 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36518 The number of bytes to watch is specified by @var{kind}.
36532 @node Stop Reply Packets
36533 @section Stop Reply Packets
36534 @cindex stop reply packets
36536 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36537 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36538 receive any of the below as a reply. Except for @samp{?}
36539 and @samp{vStopped}, that reply is only returned
36540 when the target halts. In the below the exact meaning of @dfn{signal
36541 number} is defined by the header @file{include/gdb/signals.h} in the
36542 @value{GDBN} source code.
36544 In non-stop mode, the server will simply reply @samp{OK} to commands
36545 such as @samp{vCont}; any stop will be the subject of a future
36546 notification. @xref{Remote Non-Stop}.
36548 As in the description of request packets, we include spaces in the
36549 reply templates for clarity; these are not part of the reply packet's
36550 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36556 The program received signal number @var{AA} (a two-digit hexadecimal
36557 number). This is equivalent to a @samp{T} response with no
36558 @var{n}:@var{r} pairs.
36560 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36561 @cindex @samp{T} packet reply
36562 The program received signal number @var{AA} (a two-digit hexadecimal
36563 number). This is equivalent to an @samp{S} response, except that the
36564 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36565 and other information directly in the stop reply packet, reducing
36566 round-trip latency. Single-step and breakpoint traps are reported
36567 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36571 If @var{n} is a hexadecimal number, it is a register number, and the
36572 corresponding @var{r} gives that register's value. The data @var{r} is a
36573 series of bytes in target byte order, with each byte given by a
36574 two-digit hex number.
36577 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36578 the stopped thread, as specified in @ref{thread-id syntax}.
36581 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36582 the core on which the stop event was detected.
36585 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36586 specific event that stopped the target. The currently defined stop
36587 reasons are listed below. The @var{aa} should be @samp{05}, the trap
36588 signal. At most one stop reason should be present.
36591 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36592 and go on to the next; this allows us to extend the protocol in the
36596 The currently defined stop reasons are:
36602 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36605 @item syscall_entry
36606 @itemx syscall_return
36607 The packet indicates a syscall entry or return, and @var{r} is the
36608 syscall number, in hex.
36610 @cindex shared library events, remote reply
36612 The packet indicates that the loaded libraries have changed.
36613 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36614 list of loaded libraries. The @var{r} part is ignored.
36616 @cindex replay log events, remote reply
36618 The packet indicates that the target cannot continue replaying
36619 logged execution events, because it has reached the end (or the
36620 beginning when executing backward) of the log. The value of @var{r}
36621 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36622 for more information.
36625 @anchor{swbreak stop reason}
36626 The packet indicates a software breakpoint instruction was executed,
36627 irrespective of whether it was @value{GDBN} that planted the
36628 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
36629 part must be left empty.
36631 On some architectures, such as x86, at the architecture level, when a
36632 breakpoint instruction executes the program counter points at the
36633 breakpoint address plus an offset. On such targets, the stub is
36634 responsible for adjusting the PC to point back at the breakpoint
36637 This packet should not be sent by default; older @value{GDBN} versions
36638 did not support it. @value{GDBN} requests it, by supplying an
36639 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36640 remote stub must also supply the appropriate @samp{qSupported} feature
36641 indicating support.
36643 This packet is required for correct non-stop mode operation.
36646 The packet indicates the target stopped for a hardware breakpoint.
36647 The @var{r} part must be left empty.
36649 The same remarks about @samp{qSupported} and non-stop mode above
36652 @cindex fork events, remote reply
36654 The packet indicates that @code{fork} was called, and @var{r}
36655 is the thread ID of the new child process. Refer to
36656 @ref{thread-id syntax} for the format of the @var{thread-id}
36657 field. This packet is only applicable to targets that support
36660 This packet should not be sent by default; older @value{GDBN} versions
36661 did not support it. @value{GDBN} requests it, by supplying an
36662 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36663 remote stub must also supply the appropriate @samp{qSupported} feature
36664 indicating support.
36666 @cindex vfork events, remote reply
36668 The packet indicates that @code{vfork} was called, and @var{r}
36669 is the thread ID of the new child process. Refer to
36670 @ref{thread-id syntax} for the format of the @var{thread-id}
36671 field. This packet is only applicable to targets that support
36674 This packet should not be sent by default; older @value{GDBN} versions
36675 did not support it. @value{GDBN} requests it, by supplying an
36676 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36677 remote stub must also supply the appropriate @samp{qSupported} feature
36678 indicating support.
36680 @cindex vforkdone events, remote reply
36682 The packet indicates that a child process created by a vfork
36683 has either called @code{exec} or terminated, so that the
36684 address spaces of the parent and child process are no longer
36685 shared. The @var{r} part is ignored. This packet is only
36686 applicable to targets that support vforkdone events.
36688 This packet should not be sent by default; older @value{GDBN} versions
36689 did not support it. @value{GDBN} requests it, by supplying an
36690 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36691 remote stub must also supply the appropriate @samp{qSupported} feature
36692 indicating support.
36694 @cindex exec events, remote reply
36696 The packet indicates that @code{execve} was called, and @var{r}
36697 is the absolute pathname of the file that was executed, in hex.
36698 This packet is only applicable to targets that support exec events.
36700 This packet should not be sent by default; older @value{GDBN} versions
36701 did not support it. @value{GDBN} requests it, by supplying an
36702 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36703 remote stub must also supply the appropriate @samp{qSupported} feature
36704 indicating support.
36706 @cindex thread create event, remote reply
36707 @anchor{thread create event}
36709 The packet indicates that the thread was just created. The new thread
36710 is stopped until @value{GDBN} sets it running with a resumption packet
36711 (@pxref{vCont packet}). This packet should not be sent by default;
36712 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
36713 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
36714 @var{r} part is ignored.
36719 @itemx W @var{AA} ; process:@var{pid}
36720 The process exited, and @var{AA} is the exit status. This is only
36721 applicable to certain targets.
36723 The second form of the response, including the process ID of the
36724 exited process, can be used only when @value{GDBN} has reported
36725 support for multiprocess protocol extensions; see @ref{multiprocess
36726 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36730 @itemx X @var{AA} ; process:@var{pid}
36731 The process terminated with signal @var{AA}.
36733 The second form of the response, including the process ID of the
36734 terminated process, can be used only when @value{GDBN} has reported
36735 support for multiprocess protocol extensions; see @ref{multiprocess
36736 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36739 @anchor{thread exit event}
36740 @cindex thread exit event, remote reply
36741 @item w @var{AA} ; @var{tid}
36743 The thread exited, and @var{AA} is the exit status. This response
36744 should not be sent by default; @value{GDBN} requests it with the
36745 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
36746 @var{AA} is formatted as a big-endian hex string.
36749 There are no resumed threads left in the target. In other words, even
36750 though the process is alive, the last resumed thread has exited. For
36751 example, say the target process has two threads: thread 1 and thread
36752 2. The client leaves thread 1 stopped, and resumes thread 2, which
36753 subsequently exits. At this point, even though the process is still
36754 alive, and thus no @samp{W} stop reply is sent, no thread is actually
36755 executing either. The @samp{N} stop reply thus informs the client
36756 that it can stop waiting for stop replies. This packet should not be
36757 sent by default; older @value{GDBN} versions did not support it.
36758 @value{GDBN} requests it, by supplying an appropriate
36759 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
36760 also supply the appropriate @samp{qSupported} feature indicating
36763 @item O @var{XX}@dots{}
36764 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36765 written as the program's console output. This can happen at any time
36766 while the program is running and the debugger should continue to wait
36767 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36769 @item F @var{call-id},@var{parameter}@dots{}
36770 @var{call-id} is the identifier which says which host system call should
36771 be called. This is just the name of the function. Translation into the
36772 correct system call is only applicable as it's defined in @value{GDBN}.
36773 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36776 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36777 this very system call.
36779 The target replies with this packet when it expects @value{GDBN} to
36780 call a host system call on behalf of the target. @value{GDBN} replies
36781 with an appropriate @samp{F} packet and keeps up waiting for the next
36782 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36783 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36784 Protocol Extension}, for more details.
36788 @node General Query Packets
36789 @section General Query Packets
36790 @cindex remote query requests
36792 Packets starting with @samp{q} are @dfn{general query packets};
36793 packets starting with @samp{Q} are @dfn{general set packets}. General
36794 query and set packets are a semi-unified form for retrieving and
36795 sending information to and from the stub.
36797 The initial letter of a query or set packet is followed by a name
36798 indicating what sort of thing the packet applies to. For example,
36799 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36800 definitions with the stub. These packet names follow some
36805 The name must not contain commas, colons or semicolons.
36807 Most @value{GDBN} query and set packets have a leading upper case
36810 The names of custom vendor packets should use a company prefix, in
36811 lower case, followed by a period. For example, packets designed at
36812 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36813 foos) or @samp{Qacme.bar} (for setting bars).
36816 The name of a query or set packet should be separated from any
36817 parameters by a @samp{:}; the parameters themselves should be
36818 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36819 full packet name, and check for a separator or the end of the packet,
36820 in case two packet names share a common prefix. New packets should not begin
36821 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36822 packets predate these conventions, and have arguments without any terminator
36823 for the packet name; we suspect they are in widespread use in places that
36824 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36825 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36828 Like the descriptions of the other packets, each description here
36829 has a template showing the packet's overall syntax, followed by an
36830 explanation of the packet's meaning. We include spaces in some of the
36831 templates for clarity; these are not part of the packet's syntax. No
36832 @value{GDBN} packet uses spaces to separate its components.
36834 Here are the currently defined query and set packets:
36840 Turn on or off the agent as a helper to perform some debugging operations
36841 delegated from @value{GDBN} (@pxref{Control Agent}).
36843 @item QAllow:@var{op}:@var{val}@dots{}
36844 @cindex @samp{QAllow} packet
36845 Specify which operations @value{GDBN} expects to request of the
36846 target, as a semicolon-separated list of operation name and value
36847 pairs. Possible values for @var{op} include @samp{WriteReg},
36848 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36849 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36850 indicating that @value{GDBN} will not request the operation, or 1,
36851 indicating that it may. (The target can then use this to set up its
36852 own internals optimally, for instance if the debugger never expects to
36853 insert breakpoints, it may not need to install its own trap handler.)
36856 @cindex current thread, remote request
36857 @cindex @samp{qC} packet
36858 Return the current thread ID.
36862 @item QC @var{thread-id}
36863 Where @var{thread-id} is a thread ID as documented in
36864 @ref{thread-id syntax}.
36865 @item @r{(anything else)}
36866 Any other reply implies the old thread ID.
36869 @item qCRC:@var{addr},@var{length}
36870 @cindex CRC of memory block, remote request
36871 @cindex @samp{qCRC} packet
36872 @anchor{qCRC packet}
36873 Compute the CRC checksum of a block of memory using CRC-32 defined in
36874 IEEE 802.3. The CRC is computed byte at a time, taking the most
36875 significant bit of each byte first. The initial pattern code
36876 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36878 @emph{Note:} This is the same CRC used in validating separate debug
36879 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36880 Files}). However the algorithm is slightly different. When validating
36881 separate debug files, the CRC is computed taking the @emph{least}
36882 significant bit of each byte first, and the final result is inverted to
36883 detect trailing zeros.
36888 An error (such as memory fault)
36889 @item C @var{crc32}
36890 The specified memory region's checksum is @var{crc32}.
36893 @item QDisableRandomization:@var{value}
36894 @cindex disable address space randomization, remote request
36895 @cindex @samp{QDisableRandomization} packet
36896 Some target operating systems will randomize the virtual address space
36897 of the inferior process as a security feature, but provide a feature
36898 to disable such randomization, e.g.@: to allow for a more deterministic
36899 debugging experience. On such systems, this packet with a @var{value}
36900 of 1 directs the target to disable address space randomization for
36901 processes subsequently started via @samp{vRun} packets, while a packet
36902 with a @var{value} of 0 tells the target to enable address space
36905 This packet is only available in extended mode (@pxref{extended mode}).
36910 The request succeeded.
36913 An error occurred. The error number @var{nn} is given as hex digits.
36916 An empty reply indicates that @samp{QDisableRandomization} is not supported
36920 This packet is not probed by default; the remote stub must request it,
36921 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36922 This should only be done on targets that actually support disabling
36923 address space randomization.
36925 @item QStartupWithShell:@var{value}
36926 @cindex startup with shell, remote request
36927 @cindex @samp{QStartupWithShell} packet
36928 On UNIX-like targets, it is possible to start the inferior using a
36929 shell program. This is the default behavior on both @value{GDBN} and
36930 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
36931 used to inform @command{gdbserver} whether it should start the
36932 inferior using a shell or not.
36934 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
36935 to start the inferior. If @var{value} is @samp{1},
36936 @command{gdbserver} will use a shell to start the inferior. All other
36937 values are considered an error.
36939 This packet is only available in extended mode (@pxref{extended
36945 The request succeeded.
36948 An error occurred. The error number @var{nn} is given as hex digits.
36951 This packet is not probed by default; the remote stub must request it,
36952 by supplying an appropriate @samp{qSupported} response
36953 (@pxref{qSupported}). This should only be done on targets that
36954 actually support starting the inferior using a shell.
36956 Use of this packet is controlled by the @code{set startup-with-shell}
36957 command; @pxref{set startup-with-shell}.
36959 @item QEnvironmentHexEncoded:@var{hex-value}
36960 @anchor{QEnvironmentHexEncoded}
36961 @cindex set environment variable, remote request
36962 @cindex @samp{QEnvironmentHexEncoded} packet
36963 On UNIX-like targets, it is possible to set environment variables that
36964 will be passed to the inferior during the startup process. This
36965 packet is used to inform @command{gdbserver} of an environment
36966 variable that has been defined by the user on @value{GDBN} (@pxref{set
36969 The packet is composed by @var{hex-value}, an hex encoded
36970 representation of the @var{name=value} format representing an
36971 environment variable. The name of the environment variable is
36972 represented by @var{name}, and the value to be assigned to the
36973 environment variable is represented by @var{value}. If the variable
36974 has no value (i.e., the value is @code{null}), then @var{value} will
36977 This packet is only available in extended mode (@pxref{extended
36983 The request succeeded.
36986 This packet is not probed by default; the remote stub must request it,
36987 by supplying an appropriate @samp{qSupported} response
36988 (@pxref{qSupported}). This should only be done on targets that
36989 actually support passing environment variables to the starting
36992 This packet is related to the @code{set environment} command;
36993 @pxref{set environment}.
36995 @item QEnvironmentUnset:@var{hex-value}
36996 @anchor{QEnvironmentUnset}
36997 @cindex unset environment variable, remote request
36998 @cindex @samp{QEnvironmentUnset} packet
36999 On UNIX-like targets, it is possible to unset environment variables
37000 before starting the inferior in the remote target. This packet is
37001 used to inform @command{gdbserver} of an environment variable that has
37002 been unset by the user on @value{GDBN} (@pxref{unset environment}).
37004 The packet is composed by @var{hex-value}, an hex encoded
37005 representation of the name of the environment variable to be unset.
37007 This packet is only available in extended mode (@pxref{extended
37013 The request succeeded.
37016 This packet is not probed by default; the remote stub must request it,
37017 by supplying an appropriate @samp{qSupported} response
37018 (@pxref{qSupported}). This should only be done on targets that
37019 actually support passing environment variables to the starting
37022 This packet is related to the @code{unset environment} command;
37023 @pxref{unset environment}.
37025 @item QEnvironmentReset
37026 @anchor{QEnvironmentReset}
37027 @cindex reset environment, remote request
37028 @cindex @samp{QEnvironmentReset} packet
37029 On UNIX-like targets, this packet is used to reset the state of
37030 environment variables in the remote target before starting the
37031 inferior. In this context, reset means unsetting all environment
37032 variables that were previously set by the user (i.e., were not
37033 initially present in the environment). It is sent to
37034 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
37035 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
37036 (@pxref{QEnvironmentUnset}) packets.
37038 This packet is only available in extended mode (@pxref{extended
37044 The request succeeded.
37047 This packet is not probed by default; the remote stub must request it,
37048 by supplying an appropriate @samp{qSupported} response
37049 (@pxref{qSupported}). This should only be done on targets that
37050 actually support passing environment variables to the starting
37053 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
37054 @anchor{QSetWorkingDir packet}
37055 @cindex set working directory, remote request
37056 @cindex @samp{QSetWorkingDir} packet
37057 This packet is used to inform the remote server of the intended
37058 current working directory for programs that are going to be executed.
37060 The packet is composed by @var{directory}, an hex encoded
37061 representation of the directory that the remote inferior will use as
37062 its current working directory. If @var{directory} is an empty string,
37063 the remote server should reset the inferior's current working
37064 directory to its original, empty value.
37066 This packet is only available in extended mode (@pxref{extended
37072 The request succeeded.
37076 @itemx qsThreadInfo
37077 @cindex list active threads, remote request
37078 @cindex @samp{qfThreadInfo} packet
37079 @cindex @samp{qsThreadInfo} packet
37080 Obtain a list of all active thread IDs from the target (OS). Since there
37081 may be too many active threads to fit into one reply packet, this query
37082 works iteratively: it may require more than one query/reply sequence to
37083 obtain the entire list of threads. The first query of the sequence will
37084 be the @samp{qfThreadInfo} query; subsequent queries in the
37085 sequence will be the @samp{qsThreadInfo} query.
37087 NOTE: This packet replaces the @samp{qL} query (see below).
37091 @item m @var{thread-id}
37093 @item m @var{thread-id},@var{thread-id}@dots{}
37094 a comma-separated list of thread IDs
37096 (lower case letter @samp{L}) denotes end of list.
37099 In response to each query, the target will reply with a list of one or
37100 more thread IDs, separated by commas.
37101 @value{GDBN} will respond to each reply with a request for more thread
37102 ids (using the @samp{qs} form of the query), until the target responds
37103 with @samp{l} (lower-case ell, for @dfn{last}).
37104 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37107 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
37108 initial connection with the remote target, and the very first thread ID
37109 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
37110 message. Therefore, the stub should ensure that the first thread ID in
37111 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
37113 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37114 @cindex get thread-local storage address, remote request
37115 @cindex @samp{qGetTLSAddr} packet
37116 Fetch the address associated with thread local storage specified
37117 by @var{thread-id}, @var{offset}, and @var{lm}.
37119 @var{thread-id} is the thread ID associated with the
37120 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37122 @var{offset} is the (big endian, hex encoded) offset associated with the
37123 thread local variable. (This offset is obtained from the debug
37124 information associated with the variable.)
37126 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37127 load module associated with the thread local storage. For example,
37128 a @sc{gnu}/Linux system will pass the link map address of the shared
37129 object associated with the thread local storage under consideration.
37130 Other operating environments may choose to represent the load module
37131 differently, so the precise meaning of this parameter will vary.
37135 @item @var{XX}@dots{}
37136 Hex encoded (big endian) bytes representing the address of the thread
37137 local storage requested.
37140 An error occurred. The error number @var{nn} is given as hex digits.
37143 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37146 @item qGetTIBAddr:@var{thread-id}
37147 @cindex get thread information block address
37148 @cindex @samp{qGetTIBAddr} packet
37149 Fetch address of the Windows OS specific Thread Information Block.
37151 @var{thread-id} is the thread ID associated with the thread.
37155 @item @var{XX}@dots{}
37156 Hex encoded (big endian) bytes representing the linear address of the
37157 thread information block.
37160 An error occured. This means that either the thread was not found, or the
37161 address could not be retrieved.
37164 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37167 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37168 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37169 digit) is one to indicate the first query and zero to indicate a
37170 subsequent query; @var{threadcount} (two hex digits) is the maximum
37171 number of threads the response packet can contain; and @var{nextthread}
37172 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37173 returned in the response as @var{argthread}.
37175 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37179 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37180 Where: @var{count} (two hex digits) is the number of threads being
37181 returned; @var{done} (one hex digit) is zero to indicate more threads
37182 and one indicates no further threads; @var{argthreadid} (eight hex
37183 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37184 is a sequence of thread IDs, @var{threadid} (eight hex
37185 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
37189 @cindex section offsets, remote request
37190 @cindex @samp{qOffsets} packet
37191 Get section offsets that the target used when relocating the downloaded
37196 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37197 Relocate the @code{Text} section by @var{xxx} from its original address.
37198 Relocate the @code{Data} section by @var{yyy} from its original address.
37199 If the object file format provides segment information (e.g.@: @sc{elf}
37200 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37201 segments by the supplied offsets.
37203 @emph{Note: while a @code{Bss} offset may be included in the response,
37204 @value{GDBN} ignores this and instead applies the @code{Data} offset
37205 to the @code{Bss} section.}
37207 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37208 Relocate the first segment of the object file, which conventionally
37209 contains program code, to a starting address of @var{xxx}. If
37210 @samp{DataSeg} is specified, relocate the second segment, which
37211 conventionally contains modifiable data, to a starting address of
37212 @var{yyy}. @value{GDBN} will report an error if the object file
37213 does not contain segment information, or does not contain at least
37214 as many segments as mentioned in the reply. Extra segments are
37215 kept at fixed offsets relative to the last relocated segment.
37218 @item qP @var{mode} @var{thread-id}
37219 @cindex thread information, remote request
37220 @cindex @samp{qP} packet
37221 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37222 encoded 32 bit mode; @var{thread-id} is a thread ID
37223 (@pxref{thread-id syntax}).
37225 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37228 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37232 @cindex non-stop mode, remote request
37233 @cindex @samp{QNonStop} packet
37235 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37236 @xref{Remote Non-Stop}, for more information.
37241 The request succeeded.
37244 An error occurred. The error number @var{nn} is given as hex digits.
37247 An empty reply indicates that @samp{QNonStop} is not supported by
37251 This packet is not probed by default; the remote stub must request it,
37252 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37253 Use of this packet is controlled by the @code{set non-stop} command;
37254 @pxref{Non-Stop Mode}.
37256 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
37257 @itemx QCatchSyscalls:0
37258 @cindex catch syscalls from inferior, remote request
37259 @cindex @samp{QCatchSyscalls} packet
37260 @anchor{QCatchSyscalls}
37261 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
37262 catching syscalls from the inferior process.
37264 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
37265 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
37266 is listed, every system call should be reported.
37268 Note that if a syscall not in the list is reported, @value{GDBN} will
37269 still filter the event according to its own list from all corresponding
37270 @code{catch syscall} commands. However, it is more efficient to only
37271 report the requested syscalls.
37273 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
37274 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
37276 If the inferior process execs, the state of @samp{QCatchSyscalls} is
37277 kept for the new process too. On targets where exec may affect syscall
37278 numbers, for example with exec between 32 and 64-bit processes, the
37279 client should send a new packet with the new syscall list.
37284 The request succeeded.
37287 An error occurred. @var{nn} are hex digits.
37290 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
37294 Use of this packet is controlled by the @code{set remote catch-syscalls}
37295 command (@pxref{Remote Configuration, set remote catch-syscalls}).
37296 This packet is not probed by default; the remote stub must request it,
37297 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37299 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37300 @cindex pass signals to inferior, remote request
37301 @cindex @samp{QPassSignals} packet
37302 @anchor{QPassSignals}
37303 Each listed @var{signal} should be passed directly to the inferior process.
37304 Signals are numbered identically to continue packets and stop replies
37305 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37306 strictly greater than the previous item. These signals do not need to stop
37307 the inferior, or be reported to @value{GDBN}. All other signals should be
37308 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37309 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37310 new list. This packet improves performance when using @samp{handle
37311 @var{signal} nostop noprint pass}.
37316 The request succeeded.
37319 An error occurred. The error number @var{nn} is given as hex digits.
37322 An empty reply indicates that @samp{QPassSignals} is not supported by
37326 Use of this packet is controlled by the @code{set remote pass-signals}
37327 command (@pxref{Remote Configuration, set remote pass-signals}).
37328 This packet is not probed by default; the remote stub must request it,
37329 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37331 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37332 @cindex signals the inferior may see, remote request
37333 @cindex @samp{QProgramSignals} packet
37334 @anchor{QProgramSignals}
37335 Each listed @var{signal} may be delivered to the inferior process.
37336 Others should be silently discarded.
37338 In some cases, the remote stub may need to decide whether to deliver a
37339 signal to the program or not without @value{GDBN} involvement. One
37340 example of that is while detaching --- the program's threads may have
37341 stopped for signals that haven't yet had a chance of being reported to
37342 @value{GDBN}, and so the remote stub can use the signal list specified
37343 by this packet to know whether to deliver or ignore those pending
37346 This does not influence whether to deliver a signal as requested by a
37347 resumption packet (@pxref{vCont packet}).
37349 Signals are numbered identically to continue packets and stop replies
37350 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37351 strictly greater than the previous item. Multiple
37352 @samp{QProgramSignals} packets do not combine; any earlier
37353 @samp{QProgramSignals} list is completely replaced by the new list.
37358 The request succeeded.
37361 An error occurred. The error number @var{nn} is given as hex digits.
37364 An empty reply indicates that @samp{QProgramSignals} is not supported
37368 Use of this packet is controlled by the @code{set remote program-signals}
37369 command (@pxref{Remote Configuration, set remote program-signals}).
37370 This packet is not probed by default; the remote stub must request it,
37371 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37373 @anchor{QThreadEvents}
37374 @item QThreadEvents:1
37375 @itemx QThreadEvents:0
37376 @cindex thread create/exit events, remote request
37377 @cindex @samp{QThreadEvents} packet
37379 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
37380 reporting of thread create and exit events. @xref{thread create
37381 event}, for the reply specifications. For example, this is used in
37382 non-stop mode when @value{GDBN} stops a set of threads and
37383 synchronously waits for the their corresponding stop replies. Without
37384 exit events, if one of the threads exits, @value{GDBN} would hang
37385 forever not knowing that it should no longer expect a stop for that
37386 same thread. @value{GDBN} does not enable this feature unless the
37387 stub reports that it supports it by including @samp{QThreadEvents+} in
37388 its @samp{qSupported} reply.
37393 The request succeeded.
37396 An error occurred. The error number @var{nn} is given as hex digits.
37399 An empty reply indicates that @samp{QThreadEvents} is not supported by
37403 Use of this packet is controlled by the @code{set remote thread-events}
37404 command (@pxref{Remote Configuration, set remote thread-events}).
37406 @item qRcmd,@var{command}
37407 @cindex execute remote command, remote request
37408 @cindex @samp{qRcmd} packet
37409 @var{command} (hex encoded) is passed to the local interpreter for
37410 execution. Invalid commands should be reported using the output
37411 string. Before the final result packet, the target may also respond
37412 with a number of intermediate @samp{O@var{output}} console output
37413 packets. @emph{Implementors should note that providing access to a
37414 stubs's interpreter may have security implications}.
37419 A command response with no output.
37421 A command response with the hex encoded output string @var{OUTPUT}.
37423 Indicate a badly formed request.
37425 An empty reply indicates that @samp{qRcmd} is not recognized.
37428 (Note that the @code{qRcmd} packet's name is separated from the
37429 command by a @samp{,}, not a @samp{:}, contrary to the naming
37430 conventions above. Please don't use this packet as a model for new
37433 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37434 @cindex searching memory, in remote debugging
37436 @cindex @samp{qSearch:memory} packet
37438 @cindex @samp{qSearch memory} packet
37439 @anchor{qSearch memory}
37440 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37441 Both @var{address} and @var{length} are encoded in hex;
37442 @var{search-pattern} is a sequence of bytes, also hex encoded.
37447 The pattern was not found.
37449 The pattern was found at @var{address}.
37451 A badly formed request or an error was encountered while searching memory.
37453 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37456 @item QStartNoAckMode
37457 @cindex @samp{QStartNoAckMode} packet
37458 @anchor{QStartNoAckMode}
37459 Request that the remote stub disable the normal @samp{+}/@samp{-}
37460 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37465 The stub has switched to no-acknowledgment mode.
37466 @value{GDBN} acknowledges this reponse,
37467 but neither the stub nor @value{GDBN} shall send or expect further
37468 @samp{+}/@samp{-} acknowledgments in the current connection.
37470 An empty reply indicates that the stub does not support no-acknowledgment mode.
37473 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37474 @cindex supported packets, remote query
37475 @cindex features of the remote protocol
37476 @cindex @samp{qSupported} packet
37477 @anchor{qSupported}
37478 Tell the remote stub about features supported by @value{GDBN}, and
37479 query the stub for features it supports. This packet allows
37480 @value{GDBN} and the remote stub to take advantage of each others'
37481 features. @samp{qSupported} also consolidates multiple feature probes
37482 at startup, to improve @value{GDBN} performance---a single larger
37483 packet performs better than multiple smaller probe packets on
37484 high-latency links. Some features may enable behavior which must not
37485 be on by default, e.g.@: because it would confuse older clients or
37486 stubs. Other features may describe packets which could be
37487 automatically probed for, but are not. These features must be
37488 reported before @value{GDBN} will use them. This ``default
37489 unsupported'' behavior is not appropriate for all packets, but it
37490 helps to keep the initial connection time under control with new
37491 versions of @value{GDBN} which support increasing numbers of packets.
37495 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37496 The stub supports or does not support each returned @var{stubfeature},
37497 depending on the form of each @var{stubfeature} (see below for the
37500 An empty reply indicates that @samp{qSupported} is not recognized,
37501 or that no features needed to be reported to @value{GDBN}.
37504 The allowed forms for each feature (either a @var{gdbfeature} in the
37505 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37509 @item @var{name}=@var{value}
37510 The remote protocol feature @var{name} is supported, and associated
37511 with the specified @var{value}. The format of @var{value} depends
37512 on the feature, but it must not include a semicolon.
37514 The remote protocol feature @var{name} is supported, and does not
37515 need an associated value.
37517 The remote protocol feature @var{name} is not supported.
37519 The remote protocol feature @var{name} may be supported, and
37520 @value{GDBN} should auto-detect support in some other way when it is
37521 needed. This form will not be used for @var{gdbfeature} notifications,
37522 but may be used for @var{stubfeature} responses.
37525 Whenever the stub receives a @samp{qSupported} request, the
37526 supplied set of @value{GDBN} features should override any previous
37527 request. This allows @value{GDBN} to put the stub in a known
37528 state, even if the stub had previously been communicating with
37529 a different version of @value{GDBN}.
37531 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37536 This feature indicates whether @value{GDBN} supports multiprocess
37537 extensions to the remote protocol. @value{GDBN} does not use such
37538 extensions unless the stub also reports that it supports them by
37539 including @samp{multiprocess+} in its @samp{qSupported} reply.
37540 @xref{multiprocess extensions}, for details.
37543 This feature indicates that @value{GDBN} supports the XML target
37544 description. If the stub sees @samp{xmlRegisters=} with target
37545 specific strings separated by a comma, it will report register
37549 This feature indicates whether @value{GDBN} supports the
37550 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37551 instruction reply packet}).
37554 This feature indicates whether @value{GDBN} supports the swbreak stop
37555 reason in stop replies. @xref{swbreak stop reason}, for details.
37558 This feature indicates whether @value{GDBN} supports the hwbreak stop
37559 reason in stop replies. @xref{swbreak stop reason}, for details.
37562 This feature indicates whether @value{GDBN} supports fork event
37563 extensions to the remote protocol. @value{GDBN} does not use such
37564 extensions unless the stub also reports that it supports them by
37565 including @samp{fork-events+} in its @samp{qSupported} reply.
37568 This feature indicates whether @value{GDBN} supports vfork event
37569 extensions to the remote protocol. @value{GDBN} does not use such
37570 extensions unless the stub also reports that it supports them by
37571 including @samp{vfork-events+} in its @samp{qSupported} reply.
37574 This feature indicates whether @value{GDBN} supports exec event
37575 extensions to the remote protocol. @value{GDBN} does not use such
37576 extensions unless the stub also reports that it supports them by
37577 including @samp{exec-events+} in its @samp{qSupported} reply.
37579 @item vContSupported
37580 This feature indicates whether @value{GDBN} wants to know the
37581 supported actions in the reply to @samp{vCont?} packet.
37584 Stubs should ignore any unknown values for
37585 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37586 packet supports receiving packets of unlimited length (earlier
37587 versions of @value{GDBN} may reject overly long responses). Additional values
37588 for @var{gdbfeature} may be defined in the future to let the stub take
37589 advantage of new features in @value{GDBN}, e.g.@: incompatible
37590 improvements in the remote protocol---the @samp{multiprocess} feature is
37591 an example of such a feature. The stub's reply should be independent
37592 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37593 describes all the features it supports, and then the stub replies with
37594 all the features it supports.
37596 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37597 responses, as long as each response uses one of the standard forms.
37599 Some features are flags. A stub which supports a flag feature
37600 should respond with a @samp{+} form response. Other features
37601 require values, and the stub should respond with an @samp{=}
37604 Each feature has a default value, which @value{GDBN} will use if
37605 @samp{qSupported} is not available or if the feature is not mentioned
37606 in the @samp{qSupported} response. The default values are fixed; a
37607 stub is free to omit any feature responses that match the defaults.
37609 Not all features can be probed, but for those which can, the probing
37610 mechanism is useful: in some cases, a stub's internal
37611 architecture may not allow the protocol layer to know some information
37612 about the underlying target in advance. This is especially common in
37613 stubs which may be configured for multiple targets.
37615 These are the currently defined stub features and their properties:
37617 @multitable @columnfractions 0.35 0.2 0.12 0.2
37618 @c NOTE: The first row should be @headitem, but we do not yet require
37619 @c a new enough version of Texinfo (4.7) to use @headitem.
37621 @tab Value Required
37625 @item @samp{PacketSize}
37630 @item @samp{qXfer:auxv:read}
37635 @item @samp{qXfer:btrace:read}
37640 @item @samp{qXfer:btrace-conf:read}
37645 @item @samp{qXfer:exec-file:read}
37650 @item @samp{qXfer:features:read}
37655 @item @samp{qXfer:libraries:read}
37660 @item @samp{qXfer:libraries-svr4:read}
37665 @item @samp{augmented-libraries-svr4-read}
37670 @item @samp{qXfer:memory-map:read}
37675 @item @samp{qXfer:sdata:read}
37680 @item @samp{qXfer:spu:read}
37685 @item @samp{qXfer:spu:write}
37690 @item @samp{qXfer:siginfo:read}
37695 @item @samp{qXfer:siginfo:write}
37700 @item @samp{qXfer:threads:read}
37705 @item @samp{qXfer:traceframe-info:read}
37710 @item @samp{qXfer:uib:read}
37715 @item @samp{qXfer:fdpic:read}
37720 @item @samp{Qbtrace:off}
37725 @item @samp{Qbtrace:bts}
37730 @item @samp{Qbtrace:pt}
37735 @item @samp{Qbtrace-conf:bts:size}
37740 @item @samp{Qbtrace-conf:pt:size}
37745 @item @samp{QNonStop}
37750 @item @samp{QCatchSyscalls}
37755 @item @samp{QPassSignals}
37760 @item @samp{QStartNoAckMode}
37765 @item @samp{multiprocess}
37770 @item @samp{ConditionalBreakpoints}
37775 @item @samp{ConditionalTracepoints}
37780 @item @samp{ReverseContinue}
37785 @item @samp{ReverseStep}
37790 @item @samp{TracepointSource}
37795 @item @samp{QAgent}
37800 @item @samp{QAllow}
37805 @item @samp{QDisableRandomization}
37810 @item @samp{EnableDisableTracepoints}
37815 @item @samp{QTBuffer:size}
37820 @item @samp{tracenz}
37825 @item @samp{BreakpointCommands}
37830 @item @samp{swbreak}
37835 @item @samp{hwbreak}
37840 @item @samp{fork-events}
37845 @item @samp{vfork-events}
37850 @item @samp{exec-events}
37855 @item @samp{QThreadEvents}
37860 @item @samp{no-resumed}
37867 These are the currently defined stub features, in more detail:
37870 @cindex packet size, remote protocol
37871 @item PacketSize=@var{bytes}
37872 The remote stub can accept packets up to at least @var{bytes} in
37873 length. @value{GDBN} will send packets up to this size for bulk
37874 transfers, and will never send larger packets. This is a limit on the
37875 data characters in the packet, including the frame and checksum.
37876 There is no trailing NUL byte in a remote protocol packet; if the stub
37877 stores packets in a NUL-terminated format, it should allow an extra
37878 byte in its buffer for the NUL. If this stub feature is not supported,
37879 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37881 @item qXfer:auxv:read
37882 The remote stub understands the @samp{qXfer:auxv:read} packet
37883 (@pxref{qXfer auxiliary vector read}).
37885 @item qXfer:btrace:read
37886 The remote stub understands the @samp{qXfer:btrace:read}
37887 packet (@pxref{qXfer btrace read}).
37889 @item qXfer:btrace-conf:read
37890 The remote stub understands the @samp{qXfer:btrace-conf:read}
37891 packet (@pxref{qXfer btrace-conf read}).
37893 @item qXfer:exec-file:read
37894 The remote stub understands the @samp{qXfer:exec-file:read} packet
37895 (@pxref{qXfer executable filename read}).
37897 @item qXfer:features:read
37898 The remote stub understands the @samp{qXfer:features:read} packet
37899 (@pxref{qXfer target description read}).
37901 @item qXfer:libraries:read
37902 The remote stub understands the @samp{qXfer:libraries:read} packet
37903 (@pxref{qXfer library list read}).
37905 @item qXfer:libraries-svr4:read
37906 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37907 (@pxref{qXfer svr4 library list read}).
37909 @item augmented-libraries-svr4-read
37910 The remote stub understands the augmented form of the
37911 @samp{qXfer:libraries-svr4:read} packet
37912 (@pxref{qXfer svr4 library list read}).
37914 @item qXfer:memory-map:read
37915 The remote stub understands the @samp{qXfer:memory-map:read} packet
37916 (@pxref{qXfer memory map read}).
37918 @item qXfer:sdata:read
37919 The remote stub understands the @samp{qXfer:sdata:read} packet
37920 (@pxref{qXfer sdata read}).
37922 @item qXfer:spu:read
37923 The remote stub understands the @samp{qXfer:spu:read} packet
37924 (@pxref{qXfer spu read}).
37926 @item qXfer:spu:write
37927 The remote stub understands the @samp{qXfer:spu:write} packet
37928 (@pxref{qXfer spu write}).
37930 @item qXfer:siginfo:read
37931 The remote stub understands the @samp{qXfer:siginfo:read} packet
37932 (@pxref{qXfer siginfo read}).
37934 @item qXfer:siginfo:write
37935 The remote stub understands the @samp{qXfer:siginfo:write} packet
37936 (@pxref{qXfer siginfo write}).
37938 @item qXfer:threads:read
37939 The remote stub understands the @samp{qXfer:threads:read} packet
37940 (@pxref{qXfer threads read}).
37942 @item qXfer:traceframe-info:read
37943 The remote stub understands the @samp{qXfer:traceframe-info:read}
37944 packet (@pxref{qXfer traceframe info read}).
37946 @item qXfer:uib:read
37947 The remote stub understands the @samp{qXfer:uib:read}
37948 packet (@pxref{qXfer unwind info block}).
37950 @item qXfer:fdpic:read
37951 The remote stub understands the @samp{qXfer:fdpic:read}
37952 packet (@pxref{qXfer fdpic loadmap read}).
37955 The remote stub understands the @samp{QNonStop} packet
37956 (@pxref{QNonStop}).
37958 @item QCatchSyscalls
37959 The remote stub understands the @samp{QCatchSyscalls} packet
37960 (@pxref{QCatchSyscalls}).
37963 The remote stub understands the @samp{QPassSignals} packet
37964 (@pxref{QPassSignals}).
37966 @item QStartNoAckMode
37967 The remote stub understands the @samp{QStartNoAckMode} packet and
37968 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37971 @anchor{multiprocess extensions}
37972 @cindex multiprocess extensions, in remote protocol
37973 The remote stub understands the multiprocess extensions to the remote
37974 protocol syntax. The multiprocess extensions affect the syntax of
37975 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37976 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37977 replies. Note that reporting this feature indicates support for the
37978 syntactic extensions only, not that the stub necessarily supports
37979 debugging of more than one process at a time. The stub must not use
37980 multiprocess extensions in packet replies unless @value{GDBN} has also
37981 indicated it supports them in its @samp{qSupported} request.
37983 @item qXfer:osdata:read
37984 The remote stub understands the @samp{qXfer:osdata:read} packet
37985 ((@pxref{qXfer osdata read}).
37987 @item ConditionalBreakpoints
37988 The target accepts and implements evaluation of conditional expressions
37989 defined for breakpoints. The target will only report breakpoint triggers
37990 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37992 @item ConditionalTracepoints
37993 The remote stub accepts and implements conditional expressions defined
37994 for tracepoints (@pxref{Tracepoint Conditions}).
37996 @item ReverseContinue
37997 The remote stub accepts and implements the reverse continue packet
38001 The remote stub accepts and implements the reverse step packet
38004 @item TracepointSource
38005 The remote stub understands the @samp{QTDPsrc} packet that supplies
38006 the source form of tracepoint definitions.
38009 The remote stub understands the @samp{QAgent} packet.
38012 The remote stub understands the @samp{QAllow} packet.
38014 @item QDisableRandomization
38015 The remote stub understands the @samp{QDisableRandomization} packet.
38017 @item StaticTracepoint
38018 @cindex static tracepoints, in remote protocol
38019 The remote stub supports static tracepoints.
38021 @item InstallInTrace
38022 @anchor{install tracepoint in tracing}
38023 The remote stub supports installing tracepoint in tracing.
38025 @item EnableDisableTracepoints
38026 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
38027 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
38028 to be enabled and disabled while a trace experiment is running.
38030 @item QTBuffer:size
38031 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
38032 packet that allows to change the size of the trace buffer.
38035 @cindex string tracing, in remote protocol
38036 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
38037 See @ref{Bytecode Descriptions} for details about the bytecode.
38039 @item BreakpointCommands
38040 @cindex breakpoint commands, in remote protocol
38041 The remote stub supports running a breakpoint's command list itself,
38042 rather than reporting the hit to @value{GDBN}.
38045 The remote stub understands the @samp{Qbtrace:off} packet.
38048 The remote stub understands the @samp{Qbtrace:bts} packet.
38051 The remote stub understands the @samp{Qbtrace:pt} packet.
38053 @item Qbtrace-conf:bts:size
38054 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
38056 @item Qbtrace-conf:pt:size
38057 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
38060 The remote stub reports the @samp{swbreak} stop reason for memory
38064 The remote stub reports the @samp{hwbreak} stop reason for hardware
38068 The remote stub reports the @samp{fork} stop reason for fork events.
38071 The remote stub reports the @samp{vfork} stop reason for vfork events
38072 and vforkdone events.
38075 The remote stub reports the @samp{exec} stop reason for exec events.
38077 @item vContSupported
38078 The remote stub reports the supported actions in the reply to
38079 @samp{vCont?} packet.
38081 @item QThreadEvents
38082 The remote stub understands the @samp{QThreadEvents} packet.
38085 The remote stub reports the @samp{N} stop reply.
38090 @cindex symbol lookup, remote request
38091 @cindex @samp{qSymbol} packet
38092 Notify the target that @value{GDBN} is prepared to serve symbol lookup
38093 requests. Accept requests from the target for the values of symbols.
38098 The target does not need to look up any (more) symbols.
38099 @item qSymbol:@var{sym_name}
38100 The target requests the value of symbol @var{sym_name} (hex encoded).
38101 @value{GDBN} may provide the value by using the
38102 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
38106 @item qSymbol:@var{sym_value}:@var{sym_name}
38107 Set the value of @var{sym_name} to @var{sym_value}.
38109 @var{sym_name} (hex encoded) is the name of a symbol whose value the
38110 target has previously requested.
38112 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
38113 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
38119 The target does not need to look up any (more) symbols.
38120 @item qSymbol:@var{sym_name}
38121 The target requests the value of a new symbol @var{sym_name} (hex
38122 encoded). @value{GDBN} will continue to supply the values of symbols
38123 (if available), until the target ceases to request them.
38128 @itemx QTDisconnected
38135 @itemx qTMinFTPILen
38137 @xref{Tracepoint Packets}.
38139 @item qThreadExtraInfo,@var{thread-id}
38140 @cindex thread attributes info, remote request
38141 @cindex @samp{qThreadExtraInfo} packet
38142 Obtain from the target OS a printable string description of thread
38143 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
38144 for the forms of @var{thread-id}. This
38145 string may contain anything that the target OS thinks is interesting
38146 for @value{GDBN} to tell the user about the thread. The string is
38147 displayed in @value{GDBN}'s @code{info threads} display. Some
38148 examples of possible thread extra info strings are @samp{Runnable}, or
38149 @samp{Blocked on Mutex}.
38153 @item @var{XX}@dots{}
38154 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
38155 comprising the printable string containing the extra information about
38156 the thread's attributes.
38159 (Note that the @code{qThreadExtraInfo} packet's name is separated from
38160 the command by a @samp{,}, not a @samp{:}, contrary to the naming
38161 conventions above. Please don't use this packet as a model for new
38180 @xref{Tracepoint Packets}.
38182 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
38183 @cindex read special object, remote request
38184 @cindex @samp{qXfer} packet
38185 @anchor{qXfer read}
38186 Read uninterpreted bytes from the target's special data area
38187 identified by the keyword @var{object}. Request @var{length} bytes
38188 starting at @var{offset} bytes into the data. The content and
38189 encoding of @var{annex} is specific to @var{object}; it can supply
38190 additional details about what data to access.
38195 Data @var{data} (@pxref{Binary Data}) has been read from the
38196 target. There may be more data at a higher address (although
38197 it is permitted to return @samp{m} even for the last valid
38198 block of data, as long as at least one byte of data was read).
38199 It is possible for @var{data} to have fewer bytes than the @var{length} in the
38203 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38204 There is no more data to be read. It is possible for @var{data} to
38205 have fewer bytes than the @var{length} in the request.
38208 The @var{offset} in the request is at the end of the data.
38209 There is no more data to be read.
38212 The request was malformed, or @var{annex} was invalid.
38215 The offset was invalid, or there was an error encountered reading the data.
38216 The @var{nn} part is a hex-encoded @code{errno} value.
38219 An empty reply indicates the @var{object} string was not recognized by
38220 the stub, or that the object does not support reading.
38223 Here are the specific requests of this form defined so far. All the
38224 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
38225 formats, listed above.
38228 @item qXfer:auxv:read::@var{offset},@var{length}
38229 @anchor{qXfer auxiliary vector read}
38230 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
38231 auxiliary vector}. Note @var{annex} must be empty.
38233 This packet is not probed by default; the remote stub must request it,
38234 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38236 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
38237 @anchor{qXfer btrace read}
38239 Return a description of the current branch trace.
38240 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
38241 packet may have one of the following values:
38245 Returns all available branch trace.
38248 Returns all available branch trace if the branch trace changed since
38249 the last read request.
38252 Returns the new branch trace since the last read request. Adds a new
38253 block to the end of the trace that begins at zero and ends at the source
38254 location of the first branch in the trace buffer. This extra block is
38255 used to stitch traces together.
38257 If the trace buffer overflowed, returns an error indicating the overflow.
38260 This packet is not probed by default; the remote stub must request it
38261 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38263 @item qXfer:btrace-conf:read::@var{offset},@var{length}
38264 @anchor{qXfer btrace-conf read}
38266 Return a description of the current branch trace configuration.
38267 @xref{Branch Trace Configuration Format}.
38269 This packet is not probed by default; the remote stub must request it
38270 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38272 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
38273 @anchor{qXfer executable filename read}
38274 Return the full absolute name of the file that was executed to create
38275 a process running on the remote system. The annex specifies the
38276 numeric process ID of the process to query, encoded as a hexadecimal
38277 number. If the annex part is empty the remote stub should return the
38278 filename corresponding to the currently executing process.
38280 This packet is not probed by default; the remote stub must request it,
38281 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38283 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
38284 @anchor{qXfer target description read}
38285 Access the @dfn{target description}. @xref{Target Descriptions}. The
38286 annex specifies which XML document to access. The main description is
38287 always loaded from the @samp{target.xml} annex.
38289 This packet is not probed by default; the remote stub must request it,
38290 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38292 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
38293 @anchor{qXfer library list read}
38294 Access the target's list of loaded libraries. @xref{Library List Format}.
38295 The annex part of the generic @samp{qXfer} packet must be empty
38296 (@pxref{qXfer read}).
38298 Targets which maintain a list of libraries in the program's memory do
38299 not need to implement this packet; it is designed for platforms where
38300 the operating system manages the list of loaded libraries.
38302 This packet is not probed by default; the remote stub must request it,
38303 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38305 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
38306 @anchor{qXfer svr4 library list read}
38307 Access the target's list of loaded libraries when the target is an SVR4
38308 platform. @xref{Library List Format for SVR4 Targets}. The annex part
38309 of the generic @samp{qXfer} packet must be empty unless the remote
38310 stub indicated it supports the augmented form of this packet
38311 by supplying an appropriate @samp{qSupported} response
38312 (@pxref{qXfer read}, @ref{qSupported}).
38314 This packet is optional for better performance on SVR4 targets.
38315 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
38317 This packet is not probed by default; the remote stub must request it,
38318 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38320 If the remote stub indicates it supports the augmented form of this
38321 packet then the annex part of the generic @samp{qXfer} packet may
38322 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
38323 arguments. The currently supported arguments are:
38326 @item start=@var{address}
38327 A hexadecimal number specifying the address of the @samp{struct
38328 link_map} to start reading the library list from. If unset or zero
38329 then the first @samp{struct link_map} in the library list will be
38330 chosen as the starting point.
38332 @item prev=@var{address}
38333 A hexadecimal number specifying the address of the @samp{struct
38334 link_map} immediately preceding the @samp{struct link_map}
38335 specified by the @samp{start} argument. If unset or zero then
38336 the remote stub will expect that no @samp{struct link_map}
38337 exists prior to the starting point.
38341 Arguments that are not understood by the remote stub will be silently
38344 @item qXfer:memory-map:read::@var{offset},@var{length}
38345 @anchor{qXfer memory map read}
38346 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
38347 annex part of the generic @samp{qXfer} packet must be empty
38348 (@pxref{qXfer read}).
38350 This packet is not probed by default; the remote stub must request it,
38351 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38353 @item qXfer:sdata:read::@var{offset},@var{length}
38354 @anchor{qXfer sdata read}
38356 Read contents of the extra collected static tracepoint marker
38357 information. The annex part of the generic @samp{qXfer} packet must
38358 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
38361 This packet is not probed by default; the remote stub must request it,
38362 by supplying an appropriate @samp{qSupported} response
38363 (@pxref{qSupported}).
38365 @item qXfer:siginfo:read::@var{offset},@var{length}
38366 @anchor{qXfer siginfo read}
38367 Read contents of the extra signal information on the target
38368 system. The annex part of the generic @samp{qXfer} packet must be
38369 empty (@pxref{qXfer read}).
38371 This packet is not probed by default; the remote stub must request it,
38372 by supplying an appropriate @samp{qSupported} response
38373 (@pxref{qSupported}).
38375 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
38376 @anchor{qXfer spu read}
38377 Read contents of an @code{spufs} file on the target system. The
38378 annex specifies which file to read; it must be of the form
38379 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38380 in the target process, and @var{name} identifes the @code{spufs} file
38381 in that context to be accessed.
38383 This packet is not probed by default; the remote stub must request it,
38384 by supplying an appropriate @samp{qSupported} response
38385 (@pxref{qSupported}).
38387 @item qXfer:threads:read::@var{offset},@var{length}
38388 @anchor{qXfer threads read}
38389 Access the list of threads on target. @xref{Thread List Format}. The
38390 annex part of the generic @samp{qXfer} packet must be empty
38391 (@pxref{qXfer read}).
38393 This packet is not probed by default; the remote stub must request it,
38394 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38396 @item qXfer:traceframe-info:read::@var{offset},@var{length}
38397 @anchor{qXfer traceframe info read}
38399 Return a description of the current traceframe's contents.
38400 @xref{Traceframe Info Format}. The annex part of the generic
38401 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
38403 This packet is not probed by default; the remote stub must request it,
38404 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38406 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
38407 @anchor{qXfer unwind info block}
38409 Return the unwind information block for @var{pc}. This packet is used
38410 on OpenVMS/ia64 to ask the kernel unwind information.
38412 This packet is not probed by default.
38414 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
38415 @anchor{qXfer fdpic loadmap read}
38416 Read contents of @code{loadmap}s on the target system. The
38417 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
38418 executable @code{loadmap} or interpreter @code{loadmap} to read.
38420 This packet is not probed by default; the remote stub must request it,
38421 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38423 @item qXfer:osdata:read::@var{offset},@var{length}
38424 @anchor{qXfer osdata read}
38425 Access the target's @dfn{operating system information}.
38426 @xref{Operating System Information}.
38430 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38431 @cindex write data into object, remote request
38432 @anchor{qXfer write}
38433 Write uninterpreted bytes into the target's special data area
38434 identified by the keyword @var{object}, starting at @var{offset} bytes
38435 into the data. The binary-encoded data (@pxref{Binary Data}) to be
38436 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
38437 is specific to @var{object}; it can supply additional details about what data
38443 @var{nn} (hex encoded) is the number of bytes written.
38444 This may be fewer bytes than supplied in the request.
38447 The request was malformed, or @var{annex} was invalid.
38450 The offset was invalid, or there was an error encountered writing the data.
38451 The @var{nn} part is a hex-encoded @code{errno} value.
38454 An empty reply indicates the @var{object} string was not
38455 recognized by the stub, or that the object does not support writing.
38458 Here are the specific requests of this form defined so far. All the
38459 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38460 formats, listed above.
38463 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38464 @anchor{qXfer siginfo write}
38465 Write @var{data} to the extra signal information on the target system.
38466 The annex part of the generic @samp{qXfer} packet must be
38467 empty (@pxref{qXfer write}).
38469 This packet is not probed by default; the remote stub must request it,
38470 by supplying an appropriate @samp{qSupported} response
38471 (@pxref{qSupported}).
38473 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38474 @anchor{qXfer spu write}
38475 Write @var{data} to an @code{spufs} file on the target system. The
38476 annex specifies which file to write; it must be of the form
38477 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38478 in the target process, and @var{name} identifes the @code{spufs} file
38479 in that context to be accessed.
38481 This packet is not probed by default; the remote stub must request it,
38482 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38485 @item qXfer:@var{object}:@var{operation}:@dots{}
38486 Requests of this form may be added in the future. When a stub does
38487 not recognize the @var{object} keyword, or its support for
38488 @var{object} does not recognize the @var{operation} keyword, the stub
38489 must respond with an empty packet.
38491 @item qAttached:@var{pid}
38492 @cindex query attached, remote request
38493 @cindex @samp{qAttached} packet
38494 Return an indication of whether the remote server attached to an
38495 existing process or created a new process. When the multiprocess
38496 protocol extensions are supported (@pxref{multiprocess extensions}),
38497 @var{pid} is an integer in hexadecimal format identifying the target
38498 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38499 the query packet will be simplified as @samp{qAttached}.
38501 This query is used, for example, to know whether the remote process
38502 should be detached or killed when a @value{GDBN} session is ended with
38503 the @code{quit} command.
38508 The remote server attached to an existing process.
38510 The remote server created a new process.
38512 A badly formed request or an error was encountered.
38516 Enable branch tracing for the current thread using Branch Trace Store.
38521 Branch tracing has been enabled.
38523 A badly formed request or an error was encountered.
38527 Enable branch tracing for the current thread using Intel Processor Trace.
38532 Branch tracing has been enabled.
38534 A badly formed request or an error was encountered.
38538 Disable branch tracing for the current thread.
38543 Branch tracing has been disabled.
38545 A badly formed request or an error was encountered.
38548 @item Qbtrace-conf:bts:size=@var{value}
38549 Set the requested ring buffer size for new threads that use the
38550 btrace recording method in bts format.
38555 The ring buffer size has been set.
38557 A badly formed request or an error was encountered.
38560 @item Qbtrace-conf:pt:size=@var{value}
38561 Set the requested ring buffer size for new threads that use the
38562 btrace recording method in pt format.
38567 The ring buffer size has been set.
38569 A badly formed request or an error was encountered.
38574 @node Architecture-Specific Protocol Details
38575 @section Architecture-Specific Protocol Details
38577 This section describes how the remote protocol is applied to specific
38578 target architectures. Also see @ref{Standard Target Features}, for
38579 details of XML target descriptions for each architecture.
38582 * ARM-Specific Protocol Details::
38583 * MIPS-Specific Protocol Details::
38586 @node ARM-Specific Protocol Details
38587 @subsection @acronym{ARM}-specific Protocol Details
38590 * ARM Breakpoint Kinds::
38593 @node ARM Breakpoint Kinds
38594 @subsubsection @acronym{ARM} Breakpoint Kinds
38595 @cindex breakpoint kinds, @acronym{ARM}
38597 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38602 16-bit Thumb mode breakpoint.
38605 32-bit Thumb mode (Thumb-2) breakpoint.
38608 32-bit @acronym{ARM} mode breakpoint.
38612 @node MIPS-Specific Protocol Details
38613 @subsection @acronym{MIPS}-specific Protocol Details
38616 * MIPS Register packet Format::
38617 * MIPS Breakpoint Kinds::
38620 @node MIPS Register packet Format
38621 @subsubsection @acronym{MIPS} Register Packet Format
38622 @cindex register packet format, @acronym{MIPS}
38624 The following @code{g}/@code{G} packets have previously been defined.
38625 In the below, some thirty-two bit registers are transferred as
38626 sixty-four bits. Those registers should be zero/sign extended (which?)
38627 to fill the space allocated. Register bytes are transferred in target
38628 byte order. The two nibbles within a register byte are transferred
38629 most-significant -- least-significant.
38634 All registers are transferred as thirty-two bit quantities in the order:
38635 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38636 registers; fsr; fir; fp.
38639 All registers are transferred as sixty-four bit quantities (including
38640 thirty-two bit registers such as @code{sr}). The ordering is the same
38645 @node MIPS Breakpoint Kinds
38646 @subsubsection @acronym{MIPS} Breakpoint Kinds
38647 @cindex breakpoint kinds, @acronym{MIPS}
38649 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38654 16-bit @acronym{MIPS16} mode breakpoint.
38657 16-bit @acronym{microMIPS} mode breakpoint.
38660 32-bit standard @acronym{MIPS} mode breakpoint.
38663 32-bit @acronym{microMIPS} mode breakpoint.
38667 @node Tracepoint Packets
38668 @section Tracepoint Packets
38669 @cindex tracepoint packets
38670 @cindex packets, tracepoint
38672 Here we describe the packets @value{GDBN} uses to implement
38673 tracepoints (@pxref{Tracepoints}).
38677 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38678 @cindex @samp{QTDP} packet
38679 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38680 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38681 the tracepoint is disabled. The @var{step} gives the tracepoint's step
38682 count, and @var{pass} gives its pass count. If an @samp{F} is present,
38683 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38684 the number of bytes that the target should copy elsewhere to make room
38685 for the tracepoint. If an @samp{X} is present, it introduces a
38686 tracepoint condition, which consists of a hexadecimal length, followed
38687 by a comma and hex-encoded bytes, in a manner similar to action
38688 encodings as described below. If the trailing @samp{-} is present,
38689 further @samp{QTDP} packets will follow to specify this tracepoint's
38695 The packet was understood and carried out.
38697 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38699 The packet was not recognized.
38702 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38703 Define actions to be taken when a tracepoint is hit. The @var{n} and
38704 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38705 this tracepoint. This packet may only be sent immediately after
38706 another @samp{QTDP} packet that ended with a @samp{-}. If the
38707 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38708 specifying more actions for this tracepoint.
38710 In the series of action packets for a given tracepoint, at most one
38711 can have an @samp{S} before its first @var{action}. If such a packet
38712 is sent, it and the following packets define ``while-stepping''
38713 actions. Any prior packets define ordinary actions --- that is, those
38714 taken when the tracepoint is first hit. If no action packet has an
38715 @samp{S}, then all the packets in the series specify ordinary
38716 tracepoint actions.
38718 The @samp{@var{action}@dots{}} portion of the packet is a series of
38719 actions, concatenated without separators. Each action has one of the
38725 Collect the registers whose bits are set in @var{mask},
38726 a hexadecimal number whose @var{i}'th bit is set if register number
38727 @var{i} should be collected. (The least significant bit is numbered
38728 zero.) Note that @var{mask} may be any number of digits long; it may
38729 not fit in a 32-bit word.
38731 @item M @var{basereg},@var{offset},@var{len}
38732 Collect @var{len} bytes of memory starting at the address in register
38733 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38734 @samp{-1}, then the range has a fixed address: @var{offset} is the
38735 address of the lowest byte to collect. The @var{basereg},
38736 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38737 values (the @samp{-1} value for @var{basereg} is a special case).
38739 @item X @var{len},@var{expr}
38740 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38741 it directs. The agent expression @var{expr} is as described in
38742 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38743 two-digit hex number in the packet; @var{len} is the number of bytes
38744 in the expression (and thus one-half the number of hex digits in the
38749 Any number of actions may be packed together in a single @samp{QTDP}
38750 packet, as long as the packet does not exceed the maximum packet
38751 length (400 bytes, for many stubs). There may be only one @samp{R}
38752 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38753 actions. Any registers referred to by @samp{M} and @samp{X} actions
38754 must be collected by a preceding @samp{R} action. (The
38755 ``while-stepping'' actions are treated as if they were attached to a
38756 separate tracepoint, as far as these restrictions are concerned.)
38761 The packet was understood and carried out.
38763 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38765 The packet was not recognized.
38768 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38769 @cindex @samp{QTDPsrc} packet
38770 Specify a source string of tracepoint @var{n} at address @var{addr}.
38771 This is useful to get accurate reproduction of the tracepoints
38772 originally downloaded at the beginning of the trace run. The @var{type}
38773 is the name of the tracepoint part, such as @samp{cond} for the
38774 tracepoint's conditional expression (see below for a list of types), while
38775 @var{bytes} is the string, encoded in hexadecimal.
38777 @var{start} is the offset of the @var{bytes} within the overall source
38778 string, while @var{slen} is the total length of the source string.
38779 This is intended for handling source strings that are longer than will
38780 fit in a single packet.
38781 @c Add detailed example when this info is moved into a dedicated
38782 @c tracepoint descriptions section.
38784 The available string types are @samp{at} for the location,
38785 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38786 @value{GDBN} sends a separate packet for each command in the action
38787 list, in the same order in which the commands are stored in the list.
38789 The target does not need to do anything with source strings except
38790 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38793 Although this packet is optional, and @value{GDBN} will only send it
38794 if the target replies with @samp{TracepointSource} @xref{General
38795 Query Packets}, it makes both disconnected tracing and trace files
38796 much easier to use. Otherwise the user must be careful that the
38797 tracepoints in effect while looking at trace frames are identical to
38798 the ones in effect during the trace run; even a small discrepancy
38799 could cause @samp{tdump} not to work, or a particular trace frame not
38802 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
38803 @cindex define trace state variable, remote request
38804 @cindex @samp{QTDV} packet
38805 Create a new trace state variable, number @var{n}, with an initial
38806 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38807 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38808 the option of not using this packet for initial values of zero; the
38809 target should simply create the trace state variables as they are
38810 mentioned in expressions. The value @var{builtin} should be 1 (one)
38811 if the trace state variable is builtin and 0 (zero) if it is not builtin.
38812 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
38813 @samp{qTsV} packet had it set. The contents of @var{name} is the
38814 hex-encoded name (without the leading @samp{$}) of the trace state
38817 @item QTFrame:@var{n}
38818 @cindex @samp{QTFrame} packet
38819 Select the @var{n}'th tracepoint frame from the buffer, and use the
38820 register and memory contents recorded there to answer subsequent
38821 request packets from @value{GDBN}.
38823 A successful reply from the stub indicates that the stub has found the
38824 requested frame. The response is a series of parts, concatenated
38825 without separators, describing the frame we selected. Each part has
38826 one of the following forms:
38830 The selected frame is number @var{n} in the trace frame buffer;
38831 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38832 was no frame matching the criteria in the request packet.
38835 The selected trace frame records a hit of tracepoint number @var{t};
38836 @var{t} is a hexadecimal number.
38840 @item QTFrame:pc:@var{addr}
38841 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38842 currently selected frame whose PC is @var{addr};
38843 @var{addr} is a hexadecimal number.
38845 @item QTFrame:tdp:@var{t}
38846 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38847 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38848 is a hexadecimal number.
38850 @item QTFrame:range:@var{start}:@var{end}
38851 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38852 currently selected frame whose PC is between @var{start} (inclusive)
38853 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38856 @item QTFrame:outside:@var{start}:@var{end}
38857 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38858 frame @emph{outside} the given range of addresses (exclusive).
38861 @cindex @samp{qTMinFTPILen} packet
38862 This packet requests the minimum length of instruction at which a fast
38863 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38864 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38865 it depends on the target system being able to create trampolines in
38866 the first 64K of memory, which might or might not be possible for that
38867 system. So the reply to this packet will be 4 if it is able to
38874 The minimum instruction length is currently unknown.
38876 The minimum instruction length is @var{length}, where @var{length}
38877 is a hexadecimal number greater or equal to 1. A reply
38878 of 1 means that a fast tracepoint may be placed on any instruction
38879 regardless of size.
38881 An error has occurred.
38883 An empty reply indicates that the request is not supported by the stub.
38887 @cindex @samp{QTStart} packet
38888 Begin the tracepoint experiment. Begin collecting data from
38889 tracepoint hits in the trace frame buffer. This packet supports the
38890 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38891 instruction reply packet}).
38894 @cindex @samp{QTStop} packet
38895 End the tracepoint experiment. Stop collecting trace frames.
38897 @item QTEnable:@var{n}:@var{addr}
38899 @cindex @samp{QTEnable} packet
38900 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38901 experiment. If the tracepoint was previously disabled, then collection
38902 of data from it will resume.
38904 @item QTDisable:@var{n}:@var{addr}
38906 @cindex @samp{QTDisable} packet
38907 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38908 experiment. No more data will be collected from the tracepoint unless
38909 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38912 @cindex @samp{QTinit} packet
38913 Clear the table of tracepoints, and empty the trace frame buffer.
38915 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38916 @cindex @samp{QTro} packet
38917 Establish the given ranges of memory as ``transparent''. The stub
38918 will answer requests for these ranges from memory's current contents,
38919 if they were not collected as part of the tracepoint hit.
38921 @value{GDBN} uses this to mark read-only regions of memory, like those
38922 containing program code. Since these areas never change, they should
38923 still have the same contents they did when the tracepoint was hit, so
38924 there's no reason for the stub to refuse to provide their contents.
38926 @item QTDisconnected:@var{value}
38927 @cindex @samp{QTDisconnected} packet
38928 Set the choice to what to do with the tracing run when @value{GDBN}
38929 disconnects from the target. A @var{value} of 1 directs the target to
38930 continue the tracing run, while 0 tells the target to stop tracing if
38931 @value{GDBN} is no longer in the picture.
38934 @cindex @samp{qTStatus} packet
38935 Ask the stub if there is a trace experiment running right now.
38937 The reply has the form:
38941 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38942 @var{running} is a single digit @code{1} if the trace is presently
38943 running, or @code{0} if not. It is followed by semicolon-separated
38944 optional fields that an agent may use to report additional status.
38948 If the trace is not running, the agent may report any of several
38949 explanations as one of the optional fields:
38954 No trace has been run yet.
38956 @item tstop[:@var{text}]:0
38957 The trace was stopped by a user-originated stop command. The optional
38958 @var{text} field is a user-supplied string supplied as part of the
38959 stop command (for instance, an explanation of why the trace was
38960 stopped manually). It is hex-encoded.
38963 The trace stopped because the trace buffer filled up.
38965 @item tdisconnected:0
38966 The trace stopped because @value{GDBN} disconnected from the target.
38968 @item tpasscount:@var{tpnum}
38969 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38971 @item terror:@var{text}:@var{tpnum}
38972 The trace stopped because tracepoint @var{tpnum} had an error. The
38973 string @var{text} is available to describe the nature of the error
38974 (for instance, a divide by zero in the condition expression); it
38978 The trace stopped for some other reason.
38982 Additional optional fields supply statistical and other information.
38983 Although not required, they are extremely useful for users monitoring
38984 the progress of a trace run. If a trace has stopped, and these
38985 numbers are reported, they must reflect the state of the just-stopped
38990 @item tframes:@var{n}
38991 The number of trace frames in the buffer.
38993 @item tcreated:@var{n}
38994 The total number of trace frames created during the run. This may
38995 be larger than the trace frame count, if the buffer is circular.
38997 @item tsize:@var{n}
38998 The total size of the trace buffer, in bytes.
39000 @item tfree:@var{n}
39001 The number of bytes still unused in the buffer.
39003 @item circular:@var{n}
39004 The value of the circular trace buffer flag. @code{1} means that the
39005 trace buffer is circular and old trace frames will be discarded if
39006 necessary to make room, @code{0} means that the trace buffer is linear
39009 @item disconn:@var{n}
39010 The value of the disconnected tracing flag. @code{1} means that
39011 tracing will continue after @value{GDBN} disconnects, @code{0} means
39012 that the trace run will stop.
39016 @item qTP:@var{tp}:@var{addr}
39017 @cindex tracepoint status, remote request
39018 @cindex @samp{qTP} packet
39019 Ask the stub for the current state of tracepoint number @var{tp} at
39020 address @var{addr}.
39024 @item V@var{hits}:@var{usage}
39025 The tracepoint has been hit @var{hits} times so far during the trace
39026 run, and accounts for @var{usage} in the trace buffer. Note that
39027 @code{while-stepping} steps are not counted as separate hits, but the
39028 steps' space consumption is added into the usage number.
39032 @item qTV:@var{var}
39033 @cindex trace state variable value, remote request
39034 @cindex @samp{qTV} packet
39035 Ask the stub for the value of the trace state variable number @var{var}.
39040 The value of the variable is @var{value}. This will be the current
39041 value of the variable if the user is examining a running target, or a
39042 saved value if the variable was collected in the trace frame that the
39043 user is looking at. Note that multiple requests may result in
39044 different reply values, such as when requesting values while the
39045 program is running.
39048 The value of the variable is unknown. This would occur, for example,
39049 if the user is examining a trace frame in which the requested variable
39054 @cindex @samp{qTfP} packet
39056 @cindex @samp{qTsP} packet
39057 These packets request data about tracepoints that are being used by
39058 the target. @value{GDBN} sends @code{qTfP} to get the first piece
39059 of data, and multiple @code{qTsP} to get additional pieces. Replies
39060 to these packets generally take the form of the @code{QTDP} packets
39061 that define tracepoints. (FIXME add detailed syntax)
39064 @cindex @samp{qTfV} packet
39066 @cindex @samp{qTsV} packet
39067 These packets request data about trace state variables that are on the
39068 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
39069 and multiple @code{qTsV} to get additional variables. Replies to
39070 these packets follow the syntax of the @code{QTDV} packets that define
39071 trace state variables.
39077 @cindex @samp{qTfSTM} packet
39078 @cindex @samp{qTsSTM} packet
39079 These packets request data about static tracepoint markers that exist
39080 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
39081 first piece of data, and multiple @code{qTsSTM} to get additional
39082 pieces. Replies to these packets take the following form:
39086 @item m @var{address}:@var{id}:@var{extra}
39088 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
39089 a comma-separated list of markers
39091 (lower case letter @samp{L}) denotes end of list.
39093 An error occurred. The error number @var{nn} is given as hex digits.
39095 An empty reply indicates that the request is not supported by the
39099 The @var{address} is encoded in hex;
39100 @var{id} and @var{extra} are strings encoded in hex.
39102 In response to each query, the target will reply with a list of one or
39103 more markers, separated by commas. @value{GDBN} will respond to each
39104 reply with a request for more markers (using the @samp{qs} form of the
39105 query), until the target responds with @samp{l} (lower-case ell, for
39108 @item qTSTMat:@var{address}
39110 @cindex @samp{qTSTMat} packet
39111 This packets requests data about static tracepoint markers in the
39112 target program at @var{address}. Replies to this packet follow the
39113 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
39114 tracepoint markers.
39116 @item QTSave:@var{filename}
39117 @cindex @samp{QTSave} packet
39118 This packet directs the target to save trace data to the file name
39119 @var{filename} in the target's filesystem. The @var{filename} is encoded
39120 as a hex string; the interpretation of the file name (relative vs
39121 absolute, wild cards, etc) is up to the target.
39123 @item qTBuffer:@var{offset},@var{len}
39124 @cindex @samp{qTBuffer} packet
39125 Return up to @var{len} bytes of the current contents of trace buffer,
39126 starting at @var{offset}. The trace buffer is treated as if it were
39127 a contiguous collection of traceframes, as per the trace file format.
39128 The reply consists as many hex-encoded bytes as the target can deliver
39129 in a packet; it is not an error to return fewer than were asked for.
39130 A reply consisting of just @code{l} indicates that no bytes are
39133 @item QTBuffer:circular:@var{value}
39134 This packet directs the target to use a circular trace buffer if
39135 @var{value} is 1, or a linear buffer if the value is 0.
39137 @item QTBuffer:size:@var{size}
39138 @anchor{QTBuffer-size}
39139 @cindex @samp{QTBuffer size} packet
39140 This packet directs the target to make the trace buffer be of size
39141 @var{size} if possible. A value of @code{-1} tells the target to
39142 use whatever size it prefers.
39144 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
39145 @cindex @samp{QTNotes} packet
39146 This packet adds optional textual notes to the trace run. Allowable
39147 types include @code{user}, @code{notes}, and @code{tstop}, the
39148 @var{text} fields are arbitrary strings, hex-encoded.
39152 @subsection Relocate instruction reply packet
39153 When installing fast tracepoints in memory, the target may need to
39154 relocate the instruction currently at the tracepoint address to a
39155 different address in memory. For most instructions, a simple copy is
39156 enough, but, for example, call instructions that implicitly push the
39157 return address on the stack, and relative branches or other
39158 PC-relative instructions require offset adjustment, so that the effect
39159 of executing the instruction at a different address is the same as if
39160 it had executed in the original location.
39162 In response to several of the tracepoint packets, the target may also
39163 respond with a number of intermediate @samp{qRelocInsn} request
39164 packets before the final result packet, to have @value{GDBN} handle
39165 this relocation operation. If a packet supports this mechanism, its
39166 documentation will explicitly say so. See for example the above
39167 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
39168 format of the request is:
39171 @item qRelocInsn:@var{from};@var{to}
39173 This requests @value{GDBN} to copy instruction at address @var{from}
39174 to address @var{to}, possibly adjusted so that executing the
39175 instruction at @var{to} has the same effect as executing it at
39176 @var{from}. @value{GDBN} writes the adjusted instruction to target
39177 memory starting at @var{to}.
39182 @item qRelocInsn:@var{adjusted_size}
39183 Informs the stub the relocation is complete. The @var{adjusted_size} is
39184 the length in bytes of resulting relocated instruction sequence.
39186 A badly formed request was detected, or an error was encountered while
39187 relocating the instruction.
39190 @node Host I/O Packets
39191 @section Host I/O Packets
39192 @cindex Host I/O, remote protocol
39193 @cindex file transfer, remote protocol
39195 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
39196 operations on the far side of a remote link. For example, Host I/O is
39197 used to upload and download files to a remote target with its own
39198 filesystem. Host I/O uses the same constant values and data structure
39199 layout as the target-initiated File-I/O protocol. However, the
39200 Host I/O packets are structured differently. The target-initiated
39201 protocol relies on target memory to store parameters and buffers.
39202 Host I/O requests are initiated by @value{GDBN}, and the
39203 target's memory is not involved. @xref{File-I/O Remote Protocol
39204 Extension}, for more details on the target-initiated protocol.
39206 The Host I/O request packets all encode a single operation along with
39207 its arguments. They have this format:
39211 @item vFile:@var{operation}: @var{parameter}@dots{}
39212 @var{operation} is the name of the particular request; the target
39213 should compare the entire packet name up to the second colon when checking
39214 for a supported operation. The format of @var{parameter} depends on
39215 the operation. Numbers are always passed in hexadecimal. Negative
39216 numbers have an explicit minus sign (i.e.@: two's complement is not
39217 used). Strings (e.g.@: filenames) are encoded as a series of
39218 hexadecimal bytes. The last argument to a system call may be a
39219 buffer of escaped binary data (@pxref{Binary Data}).
39223 The valid responses to Host I/O packets are:
39227 @item F @var{result} [, @var{errno}] [; @var{attachment}]
39228 @var{result} is the integer value returned by this operation, usually
39229 non-negative for success and -1 for errors. If an error has occured,
39230 @var{errno} will be included in the result specifying a
39231 value defined by the File-I/O protocol (@pxref{Errno Values}). For
39232 operations which return data, @var{attachment} supplies the data as a
39233 binary buffer. Binary buffers in response packets are escaped in the
39234 normal way (@pxref{Binary Data}). See the individual packet
39235 documentation for the interpretation of @var{result} and
39239 An empty response indicates that this operation is not recognized.
39243 These are the supported Host I/O operations:
39246 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
39247 Open a file at @var{filename} and return a file descriptor for it, or
39248 return -1 if an error occurs. The @var{filename} is a string,
39249 @var{flags} is an integer indicating a mask of open flags
39250 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
39251 of mode bits to use if the file is created (@pxref{mode_t Values}).
39252 @xref{open}, for details of the open flags and mode values.
39254 @item vFile:close: @var{fd}
39255 Close the open file corresponding to @var{fd} and return 0, or
39256 -1 if an error occurs.
39258 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
39259 Read data from the open file corresponding to @var{fd}. Up to
39260 @var{count} bytes will be read from the file, starting at @var{offset}
39261 relative to the start of the file. The target may read fewer bytes;
39262 common reasons include packet size limits and an end-of-file
39263 condition. The number of bytes read is returned. Zero should only be
39264 returned for a successful read at the end of the file, or if
39265 @var{count} was zero.
39267 The data read should be returned as a binary attachment on success.
39268 If zero bytes were read, the response should include an empty binary
39269 attachment (i.e.@: a trailing semicolon). The return value is the
39270 number of target bytes read; the binary attachment may be longer if
39271 some characters were escaped.
39273 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
39274 Write @var{data} (a binary buffer) to the open file corresponding
39275 to @var{fd}. Start the write at @var{offset} from the start of the
39276 file. Unlike many @code{write} system calls, there is no
39277 separate @var{count} argument; the length of @var{data} in the
39278 packet is used. @samp{vFile:write} returns the number of bytes written,
39279 which may be shorter than the length of @var{data}, or -1 if an
39282 @item vFile:fstat: @var{fd}
39283 Get information about the open file corresponding to @var{fd}.
39284 On success the information is returned as a binary attachment
39285 and the return value is the size of this attachment in bytes.
39286 If an error occurs the return value is -1. The format of the
39287 returned binary attachment is as described in @ref{struct stat}.
39289 @item vFile:unlink: @var{filename}
39290 Delete the file at @var{filename} on the target. Return 0,
39291 or -1 if an error occurs. The @var{filename} is a string.
39293 @item vFile:readlink: @var{filename}
39294 Read value of symbolic link @var{filename} on the target. Return
39295 the number of bytes read, or -1 if an error occurs.
39297 The data read should be returned as a binary attachment on success.
39298 If zero bytes were read, the response should include an empty binary
39299 attachment (i.e.@: a trailing semicolon). The return value is the
39300 number of target bytes read; the binary attachment may be longer if
39301 some characters were escaped.
39303 @item vFile:setfs: @var{pid}
39304 Select the filesystem on which @code{vFile} operations with
39305 @var{filename} arguments will operate. This is required for
39306 @value{GDBN} to be able to access files on remote targets where
39307 the remote stub does not share a common filesystem with the
39310 If @var{pid} is nonzero, select the filesystem as seen by process
39311 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
39312 the remote stub. Return 0 on success, or -1 if an error occurs.
39313 If @code{vFile:setfs:} indicates success, the selected filesystem
39314 remains selected until the next successful @code{vFile:setfs:}
39320 @section Interrupts
39321 @cindex interrupts (remote protocol)
39322 @anchor{interrupting remote targets}
39324 In all-stop mode, when a program on the remote target is running,
39325 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
39326 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
39327 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
39329 The precise meaning of @code{BREAK} is defined by the transport
39330 mechanism and may, in fact, be undefined. @value{GDBN} does not
39331 currently define a @code{BREAK} mechanism for any of the network
39332 interfaces except for TCP, in which case @value{GDBN} sends the
39333 @code{telnet} BREAK sequence.
39335 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
39336 transport mechanisms. It is represented by sending the single byte
39337 @code{0x03} without any of the usual packet overhead described in
39338 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
39339 transmitted as part of a packet, it is considered to be packet data
39340 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
39341 (@pxref{X packet}), used for binary downloads, may include an unescaped
39342 @code{0x03} as part of its packet.
39344 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
39345 When Linux kernel receives this sequence from serial port,
39346 it stops execution and connects to gdb.
39348 In non-stop mode, because packet resumptions are asynchronous
39349 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
39350 command to the remote stub, even when the target is running. For that
39351 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
39352 packet}) with the usual packet framing instead of the single byte
39355 Stubs are not required to recognize these interrupt mechanisms and the
39356 precise meaning associated with receipt of the interrupt is
39357 implementation defined. If the target supports debugging of multiple
39358 threads and/or processes, it should attempt to interrupt all
39359 currently-executing threads and processes.
39360 If the stub is successful at interrupting the
39361 running program, it should send one of the stop
39362 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
39363 of successfully stopping the program in all-stop mode, and a stop reply
39364 for each stopped thread in non-stop mode.
39365 Interrupts received while the
39366 program is stopped are queued and the program will be interrupted when
39367 it is resumed next time.
39369 @node Notification Packets
39370 @section Notification Packets
39371 @cindex notification packets
39372 @cindex packets, notification
39374 The @value{GDBN} remote serial protocol includes @dfn{notifications},
39375 packets that require no acknowledgment. Both the GDB and the stub
39376 may send notifications (although the only notifications defined at
39377 present are sent by the stub). Notifications carry information
39378 without incurring the round-trip latency of an acknowledgment, and so
39379 are useful for low-impact communications where occasional packet loss
39382 A notification packet has the form @samp{% @var{data} #
39383 @var{checksum}}, where @var{data} is the content of the notification,
39384 and @var{checksum} is a checksum of @var{data}, computed and formatted
39385 as for ordinary @value{GDBN} packets. A notification's @var{data}
39386 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
39387 receiving a notification, the recipient sends no @samp{+} or @samp{-}
39388 to acknowledge the notification's receipt or to report its corruption.
39390 Every notification's @var{data} begins with a name, which contains no
39391 colon characters, followed by a colon character.
39393 Recipients should silently ignore corrupted notifications and
39394 notifications they do not understand. Recipients should restart
39395 timeout periods on receipt of a well-formed notification, whether or
39396 not they understand it.
39398 Senders should only send the notifications described here when this
39399 protocol description specifies that they are permitted. In the
39400 future, we may extend the protocol to permit existing notifications in
39401 new contexts; this rule helps older senders avoid confusing newer
39404 (Older versions of @value{GDBN} ignore bytes received until they see
39405 the @samp{$} byte that begins an ordinary packet, so new stubs may
39406 transmit notifications without fear of confusing older clients. There
39407 are no notifications defined for @value{GDBN} to send at the moment, but we
39408 assume that most older stubs would ignore them, as well.)
39410 Each notification is comprised of three parts:
39412 @item @var{name}:@var{event}
39413 The notification packet is sent by the side that initiates the
39414 exchange (currently, only the stub does that), with @var{event}
39415 carrying the specific information about the notification, and
39416 @var{name} specifying the name of the notification.
39418 The acknowledge sent by the other side, usually @value{GDBN}, to
39419 acknowledge the exchange and request the event.
39422 The purpose of an asynchronous notification mechanism is to report to
39423 @value{GDBN} that something interesting happened in the remote stub.
39425 The remote stub may send notification @var{name}:@var{event}
39426 at any time, but @value{GDBN} acknowledges the notification when
39427 appropriate. The notification event is pending before @value{GDBN}
39428 acknowledges. Only one notification at a time may be pending; if
39429 additional events occur before @value{GDBN} has acknowledged the
39430 previous notification, they must be queued by the stub for later
39431 synchronous transmission in response to @var{ack} packets from
39432 @value{GDBN}. Because the notification mechanism is unreliable,
39433 the stub is permitted to resend a notification if it believes
39434 @value{GDBN} may not have received it.
39436 Specifically, notifications may appear when @value{GDBN} is not
39437 otherwise reading input from the stub, or when @value{GDBN} is
39438 expecting to read a normal synchronous response or a
39439 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
39440 Notification packets are distinct from any other communication from
39441 the stub so there is no ambiguity.
39443 After receiving a notification, @value{GDBN} shall acknowledge it by
39444 sending a @var{ack} packet as a regular, synchronous request to the
39445 stub. Such acknowledgment is not required to happen immediately, as
39446 @value{GDBN} is permitted to send other, unrelated packets to the
39447 stub first, which the stub should process normally.
39449 Upon receiving a @var{ack} packet, if the stub has other queued
39450 events to report to @value{GDBN}, it shall respond by sending a
39451 normal @var{event}. @value{GDBN} shall then send another @var{ack}
39452 packet to solicit further responses; again, it is permitted to send
39453 other, unrelated packets as well which the stub should process
39456 If the stub receives a @var{ack} packet and there are no additional
39457 @var{event} to report, the stub shall return an @samp{OK} response.
39458 At this point, @value{GDBN} has finished processing a notification
39459 and the stub has completed sending any queued events. @value{GDBN}
39460 won't accept any new notifications until the final @samp{OK} is
39461 received . If further notification events occur, the stub shall send
39462 a new notification, @value{GDBN} shall accept the notification, and
39463 the process shall be repeated.
39465 The process of asynchronous notification can be illustrated by the
39468 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39471 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39473 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39478 The following notifications are defined:
39479 @multitable @columnfractions 0.12 0.12 0.38 0.38
39488 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39489 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39490 for information on how these notifications are acknowledged by
39492 @tab Report an asynchronous stop event in non-stop mode.
39496 @node Remote Non-Stop
39497 @section Remote Protocol Support for Non-Stop Mode
39499 @value{GDBN}'s remote protocol supports non-stop debugging of
39500 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39501 supports non-stop mode, it should report that to @value{GDBN} by including
39502 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39504 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39505 establishing a new connection with the stub. Entering non-stop mode
39506 does not alter the state of any currently-running threads, but targets
39507 must stop all threads in any already-attached processes when entering
39508 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39509 probe the target state after a mode change.
39511 In non-stop mode, when an attached process encounters an event that
39512 would otherwise be reported with a stop reply, it uses the
39513 asynchronous notification mechanism (@pxref{Notification Packets}) to
39514 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39515 in all processes are stopped when a stop reply is sent, in non-stop
39516 mode only the thread reporting the stop event is stopped. That is,
39517 when reporting a @samp{S} or @samp{T} response to indicate completion
39518 of a step operation, hitting a breakpoint, or a fault, only the
39519 affected thread is stopped; any other still-running threads continue
39520 to run. When reporting a @samp{W} or @samp{X} response, all running
39521 threads belonging to other attached processes continue to run.
39523 In non-stop mode, the target shall respond to the @samp{?} packet as
39524 follows. First, any incomplete stop reply notification/@samp{vStopped}
39525 sequence in progress is abandoned. The target must begin a new
39526 sequence reporting stop events for all stopped threads, whether or not
39527 it has previously reported those events to @value{GDBN}. The first
39528 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39529 subsequent stop replies are sent as responses to @samp{vStopped} packets
39530 using the mechanism described above. The target must not send
39531 asynchronous stop reply notifications until the sequence is complete.
39532 If all threads are running when the target receives the @samp{?} packet,
39533 or if the target is not attached to any process, it shall respond
39536 If the stub supports non-stop mode, it should also support the
39537 @samp{swbreak} stop reason if software breakpoints are supported, and
39538 the @samp{hwbreak} stop reason if hardware breakpoints are supported
39539 (@pxref{swbreak stop reason}). This is because given the asynchronous
39540 nature of non-stop mode, between the time a thread hits a breakpoint
39541 and the time the event is finally processed by @value{GDBN}, the
39542 breakpoint may have already been removed from the target. Due to
39543 this, @value{GDBN} needs to be able to tell whether a trap stop was
39544 caused by a delayed breakpoint event, which should be ignored, as
39545 opposed to a random trap signal, which should be reported to the user.
39546 Note the @samp{swbreak} feature implies that the target is responsible
39547 for adjusting the PC when a software breakpoint triggers, if
39548 necessary, such as on the x86 architecture.
39550 @node Packet Acknowledgment
39551 @section Packet Acknowledgment
39553 @cindex acknowledgment, for @value{GDBN} remote
39554 @cindex packet acknowledgment, for @value{GDBN} remote
39555 By default, when either the host or the target machine receives a packet,
39556 the first response expected is an acknowledgment: either @samp{+} (to indicate
39557 the package was received correctly) or @samp{-} (to request retransmission).
39558 This mechanism allows the @value{GDBN} remote protocol to operate over
39559 unreliable transport mechanisms, such as a serial line.
39561 In cases where the transport mechanism is itself reliable (such as a pipe or
39562 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39563 It may be desirable to disable them in that case to reduce communication
39564 overhead, or for other reasons. This can be accomplished by means of the
39565 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39567 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39568 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39569 and response format still includes the normal checksum, as described in
39570 @ref{Overview}, but the checksum may be ignored by the receiver.
39572 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39573 no-acknowledgment mode, it should report that to @value{GDBN}
39574 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39575 @pxref{qSupported}.
39576 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39577 disabled via the @code{set remote noack-packet off} command
39578 (@pxref{Remote Configuration}),
39579 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39580 Only then may the stub actually turn off packet acknowledgments.
39581 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39582 response, which can be safely ignored by the stub.
39584 Note that @code{set remote noack-packet} command only affects negotiation
39585 between @value{GDBN} and the stub when subsequent connections are made;
39586 it does not affect the protocol acknowledgment state for any current
39588 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39589 new connection is established,
39590 there is also no protocol request to re-enable the acknowledgments
39591 for the current connection, once disabled.
39596 Example sequence of a target being re-started. Notice how the restart
39597 does not get any direct output:
39602 @emph{target restarts}
39605 <- @code{T001:1234123412341234}
39609 Example sequence of a target being stepped by a single instruction:
39612 -> @code{G1445@dots{}}
39617 <- @code{T001:1234123412341234}
39621 <- @code{1455@dots{}}
39625 @node File-I/O Remote Protocol Extension
39626 @section File-I/O Remote Protocol Extension
39627 @cindex File-I/O remote protocol extension
39630 * File-I/O Overview::
39631 * Protocol Basics::
39632 * The F Request Packet::
39633 * The F Reply Packet::
39634 * The Ctrl-C Message::
39636 * List of Supported Calls::
39637 * Protocol-specific Representation of Datatypes::
39639 * File-I/O Examples::
39642 @node File-I/O Overview
39643 @subsection File-I/O Overview
39644 @cindex file-i/o overview
39646 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39647 target to use the host's file system and console I/O to perform various
39648 system calls. System calls on the target system are translated into a
39649 remote protocol packet to the host system, which then performs the needed
39650 actions and returns a response packet to the target system.
39651 This simulates file system operations even on targets that lack file systems.
39653 The protocol is defined to be independent of both the host and target systems.
39654 It uses its own internal representation of datatypes and values. Both
39655 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39656 translating the system-dependent value representations into the internal
39657 protocol representations when data is transmitted.
39659 The communication is synchronous. A system call is possible only when
39660 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39661 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39662 the target is stopped to allow deterministic access to the target's
39663 memory. Therefore File-I/O is not interruptible by target signals. On
39664 the other hand, it is possible to interrupt File-I/O by a user interrupt
39665 (@samp{Ctrl-C}) within @value{GDBN}.
39667 The target's request to perform a host system call does not finish
39668 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39669 after finishing the system call, the target returns to continuing the
39670 previous activity (continue, step). No additional continue or step
39671 request from @value{GDBN} is required.
39674 (@value{GDBP}) continue
39675 <- target requests 'system call X'
39676 target is stopped, @value{GDBN} executes system call
39677 -> @value{GDBN} returns result
39678 ... target continues, @value{GDBN} returns to wait for the target
39679 <- target hits breakpoint and sends a Txx packet
39682 The protocol only supports I/O on the console and to regular files on
39683 the host file system. Character or block special devices, pipes,
39684 named pipes, sockets or any other communication method on the host
39685 system are not supported by this protocol.
39687 File I/O is not supported in non-stop mode.
39689 @node Protocol Basics
39690 @subsection Protocol Basics
39691 @cindex protocol basics, file-i/o
39693 The File-I/O protocol uses the @code{F} packet as the request as well
39694 as reply packet. Since a File-I/O system call can only occur when
39695 @value{GDBN} is waiting for a response from the continuing or stepping target,
39696 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39697 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39698 This @code{F} packet contains all information needed to allow @value{GDBN}
39699 to call the appropriate host system call:
39703 A unique identifier for the requested system call.
39706 All parameters to the system call. Pointers are given as addresses
39707 in the target memory address space. Pointers to strings are given as
39708 pointer/length pair. Numerical values are given as they are.
39709 Numerical control flags are given in a protocol-specific representation.
39713 At this point, @value{GDBN} has to perform the following actions.
39717 If the parameters include pointer values to data needed as input to a
39718 system call, @value{GDBN} requests this data from the target with a
39719 standard @code{m} packet request. This additional communication has to be
39720 expected by the target implementation and is handled as any other @code{m}
39724 @value{GDBN} translates all value from protocol representation to host
39725 representation as needed. Datatypes are coerced into the host types.
39728 @value{GDBN} calls the system call.
39731 It then coerces datatypes back to protocol representation.
39734 If the system call is expected to return data in buffer space specified
39735 by pointer parameters to the call, the data is transmitted to the
39736 target using a @code{M} or @code{X} packet. This packet has to be expected
39737 by the target implementation and is handled as any other @code{M} or @code{X}
39742 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39743 necessary information for the target to continue. This at least contains
39750 @code{errno}, if has been changed by the system call.
39757 After having done the needed type and value coercion, the target continues
39758 the latest continue or step action.
39760 @node The F Request Packet
39761 @subsection The @code{F} Request Packet
39762 @cindex file-i/o request packet
39763 @cindex @code{F} request packet
39765 The @code{F} request packet has the following format:
39768 @item F@var{call-id},@var{parameter@dots{}}
39770 @var{call-id} is the identifier to indicate the host system call to be called.
39771 This is just the name of the function.
39773 @var{parameter@dots{}} are the parameters to the system call.
39774 Parameters are hexadecimal integer values, either the actual values in case
39775 of scalar datatypes, pointers to target buffer space in case of compound
39776 datatypes and unspecified memory areas, or pointer/length pairs in case
39777 of string parameters. These are appended to the @var{call-id} as a
39778 comma-delimited list. All values are transmitted in ASCII
39779 string representation, pointer/length pairs separated by a slash.
39785 @node The F Reply Packet
39786 @subsection The @code{F} Reply Packet
39787 @cindex file-i/o reply packet
39788 @cindex @code{F} reply packet
39790 The @code{F} reply packet has the following format:
39794 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39796 @var{retcode} is the return code of the system call as hexadecimal value.
39798 @var{errno} is the @code{errno} set by the call, in protocol-specific
39800 This parameter can be omitted if the call was successful.
39802 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39803 case, @var{errno} must be sent as well, even if the call was successful.
39804 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39811 or, if the call was interrupted before the host call has been performed:
39818 assuming 4 is the protocol-specific representation of @code{EINTR}.
39823 @node The Ctrl-C Message
39824 @subsection The @samp{Ctrl-C} Message
39825 @cindex ctrl-c message, in file-i/o protocol
39827 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39828 reply packet (@pxref{The F Reply Packet}),
39829 the target should behave as if it had
39830 gotten a break message. The meaning for the target is ``system call
39831 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39832 (as with a break message) and return to @value{GDBN} with a @code{T02}
39835 It's important for the target to know in which
39836 state the system call was interrupted. There are two possible cases:
39840 The system call hasn't been performed on the host yet.
39843 The system call on the host has been finished.
39847 These two states can be distinguished by the target by the value of the
39848 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39849 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39850 on POSIX systems. In any other case, the target may presume that the
39851 system call has been finished --- successfully or not --- and should behave
39852 as if the break message arrived right after the system call.
39854 @value{GDBN} must behave reliably. If the system call has not been called
39855 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39856 @code{errno} in the packet. If the system call on the host has been finished
39857 before the user requests a break, the full action must be finished by
39858 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39859 The @code{F} packet may only be sent when either nothing has happened
39860 or the full action has been completed.
39863 @subsection Console I/O
39864 @cindex console i/o as part of file-i/o
39866 By default and if not explicitly closed by the target system, the file
39867 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39868 on the @value{GDBN} console is handled as any other file output operation
39869 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39870 by @value{GDBN} so that after the target read request from file descriptor
39871 0 all following typing is buffered until either one of the following
39876 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39878 system call is treated as finished.
39881 The user presses @key{RET}. This is treated as end of input with a trailing
39885 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39886 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39890 If the user has typed more characters than fit in the buffer given to
39891 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39892 either another @code{read(0, @dots{})} is requested by the target, or debugging
39893 is stopped at the user's request.
39896 @node List of Supported Calls
39897 @subsection List of Supported Calls
39898 @cindex list of supported file-i/o calls
39915 @unnumberedsubsubsec open
39916 @cindex open, file-i/o system call
39921 int open(const char *pathname, int flags);
39922 int open(const char *pathname, int flags, mode_t mode);
39926 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39929 @var{flags} is the bitwise @code{OR} of the following values:
39933 If the file does not exist it will be created. The host
39934 rules apply as far as file ownership and time stamps
39938 When used with @code{O_CREAT}, if the file already exists it is
39939 an error and open() fails.
39942 If the file already exists and the open mode allows
39943 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39944 truncated to zero length.
39947 The file is opened in append mode.
39950 The file is opened for reading only.
39953 The file is opened for writing only.
39956 The file is opened for reading and writing.
39960 Other bits are silently ignored.
39964 @var{mode} is the bitwise @code{OR} of the following values:
39968 User has read permission.
39971 User has write permission.
39974 Group has read permission.
39977 Group has write permission.
39980 Others have read permission.
39983 Others have write permission.
39987 Other bits are silently ignored.
39990 @item Return value:
39991 @code{open} returns the new file descriptor or -1 if an error
39998 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
40001 @var{pathname} refers to a directory.
40004 The requested access is not allowed.
40007 @var{pathname} was too long.
40010 A directory component in @var{pathname} does not exist.
40013 @var{pathname} refers to a device, pipe, named pipe or socket.
40016 @var{pathname} refers to a file on a read-only filesystem and
40017 write access was requested.
40020 @var{pathname} is an invalid pointer value.
40023 No space on device to create the file.
40026 The process already has the maximum number of files open.
40029 The limit on the total number of files open on the system
40033 The call was interrupted by the user.
40039 @unnumberedsubsubsec close
40040 @cindex close, file-i/o system call
40049 @samp{Fclose,@var{fd}}
40051 @item Return value:
40052 @code{close} returns zero on success, or -1 if an error occurred.
40058 @var{fd} isn't a valid open file descriptor.
40061 The call was interrupted by the user.
40067 @unnumberedsubsubsec read
40068 @cindex read, file-i/o system call
40073 int read(int fd, void *buf, unsigned int count);
40077 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
40079 @item Return value:
40080 On success, the number of bytes read is returned.
40081 Zero indicates end of file. If count is zero, read
40082 returns zero as well. On error, -1 is returned.
40088 @var{fd} is not a valid file descriptor or is not open for
40092 @var{bufptr} is an invalid pointer value.
40095 The call was interrupted by the user.
40101 @unnumberedsubsubsec write
40102 @cindex write, file-i/o system call
40107 int write(int fd, const void *buf, unsigned int count);
40111 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
40113 @item Return value:
40114 On success, the number of bytes written are returned.
40115 Zero indicates nothing was written. On error, -1
40122 @var{fd} is not a valid file descriptor or is not open for
40126 @var{bufptr} is an invalid pointer value.
40129 An attempt was made to write a file that exceeds the
40130 host-specific maximum file size allowed.
40133 No space on device to write the data.
40136 The call was interrupted by the user.
40142 @unnumberedsubsubsec lseek
40143 @cindex lseek, file-i/o system call
40148 long lseek (int fd, long offset, int flag);
40152 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
40154 @var{flag} is one of:
40158 The offset is set to @var{offset} bytes.
40161 The offset is set to its current location plus @var{offset}
40165 The offset is set to the size of the file plus @var{offset}
40169 @item Return value:
40170 On success, the resulting unsigned offset in bytes from
40171 the beginning of the file is returned. Otherwise, a
40172 value of -1 is returned.
40178 @var{fd} is not a valid open file descriptor.
40181 @var{fd} is associated with the @value{GDBN} console.
40184 @var{flag} is not a proper value.
40187 The call was interrupted by the user.
40193 @unnumberedsubsubsec rename
40194 @cindex rename, file-i/o system call
40199 int rename(const char *oldpath, const char *newpath);
40203 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
40205 @item Return value:
40206 On success, zero is returned. On error, -1 is returned.
40212 @var{newpath} is an existing directory, but @var{oldpath} is not a
40216 @var{newpath} is a non-empty directory.
40219 @var{oldpath} or @var{newpath} is a directory that is in use by some
40223 An attempt was made to make a directory a subdirectory
40227 A component used as a directory in @var{oldpath} or new
40228 path is not a directory. Or @var{oldpath} is a directory
40229 and @var{newpath} exists but is not a directory.
40232 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
40235 No access to the file or the path of the file.
40239 @var{oldpath} or @var{newpath} was too long.
40242 A directory component in @var{oldpath} or @var{newpath} does not exist.
40245 The file is on a read-only filesystem.
40248 The device containing the file has no room for the new
40252 The call was interrupted by the user.
40258 @unnumberedsubsubsec unlink
40259 @cindex unlink, file-i/o system call
40264 int unlink(const char *pathname);
40268 @samp{Funlink,@var{pathnameptr}/@var{len}}
40270 @item Return value:
40271 On success, zero is returned. On error, -1 is returned.
40277 No access to the file or the path of the file.
40280 The system does not allow unlinking of directories.
40283 The file @var{pathname} cannot be unlinked because it's
40284 being used by another process.
40287 @var{pathnameptr} is an invalid pointer value.
40290 @var{pathname} was too long.
40293 A directory component in @var{pathname} does not exist.
40296 A component of the path is not a directory.
40299 The file is on a read-only filesystem.
40302 The call was interrupted by the user.
40308 @unnumberedsubsubsec stat/fstat
40309 @cindex fstat, file-i/o system call
40310 @cindex stat, file-i/o system call
40315 int stat(const char *pathname, struct stat *buf);
40316 int fstat(int fd, struct stat *buf);
40320 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
40321 @samp{Ffstat,@var{fd},@var{bufptr}}
40323 @item Return value:
40324 On success, zero is returned. On error, -1 is returned.
40330 @var{fd} is not a valid open file.
40333 A directory component in @var{pathname} does not exist or the
40334 path is an empty string.
40337 A component of the path is not a directory.
40340 @var{pathnameptr} is an invalid pointer value.
40343 No access to the file or the path of the file.
40346 @var{pathname} was too long.
40349 The call was interrupted by the user.
40355 @unnumberedsubsubsec gettimeofday
40356 @cindex gettimeofday, file-i/o system call
40361 int gettimeofday(struct timeval *tv, void *tz);
40365 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
40367 @item Return value:
40368 On success, 0 is returned, -1 otherwise.
40374 @var{tz} is a non-NULL pointer.
40377 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
40383 @unnumberedsubsubsec isatty
40384 @cindex isatty, file-i/o system call
40389 int isatty(int fd);
40393 @samp{Fisatty,@var{fd}}
40395 @item Return value:
40396 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
40402 The call was interrupted by the user.
40407 Note that the @code{isatty} call is treated as a special case: it returns
40408 1 to the target if the file descriptor is attached
40409 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
40410 would require implementing @code{ioctl} and would be more complex than
40415 @unnumberedsubsubsec system
40416 @cindex system, file-i/o system call
40421 int system(const char *command);
40425 @samp{Fsystem,@var{commandptr}/@var{len}}
40427 @item Return value:
40428 If @var{len} is zero, the return value indicates whether a shell is
40429 available. A zero return value indicates a shell is not available.
40430 For non-zero @var{len}, the value returned is -1 on error and the
40431 return status of the command otherwise. Only the exit status of the
40432 command is returned, which is extracted from the host's @code{system}
40433 return value by calling @code{WEXITSTATUS(retval)}. In case
40434 @file{/bin/sh} could not be executed, 127 is returned.
40440 The call was interrupted by the user.
40445 @value{GDBN} takes over the full task of calling the necessary host calls
40446 to perform the @code{system} call. The return value of @code{system} on
40447 the host is simplified before it's returned
40448 to the target. Any termination signal information from the child process
40449 is discarded, and the return value consists
40450 entirely of the exit status of the called command.
40452 Due to security concerns, the @code{system} call is by default refused
40453 by @value{GDBN}. The user has to allow this call explicitly with the
40454 @code{set remote system-call-allowed 1} command.
40457 @item set remote system-call-allowed
40458 @kindex set remote system-call-allowed
40459 Control whether to allow the @code{system} calls in the File I/O
40460 protocol for the remote target. The default is zero (disabled).
40462 @item show remote system-call-allowed
40463 @kindex show remote system-call-allowed
40464 Show whether the @code{system} calls are allowed in the File I/O
40468 @node Protocol-specific Representation of Datatypes
40469 @subsection Protocol-specific Representation of Datatypes
40470 @cindex protocol-specific representation of datatypes, in file-i/o protocol
40473 * Integral Datatypes::
40475 * Memory Transfer::
40480 @node Integral Datatypes
40481 @unnumberedsubsubsec Integral Datatypes
40482 @cindex integral datatypes, in file-i/o protocol
40484 The integral datatypes used in the system calls are @code{int},
40485 @code{unsigned int}, @code{long}, @code{unsigned long},
40486 @code{mode_t}, and @code{time_t}.
40488 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40489 implemented as 32 bit values in this protocol.
40491 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40493 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40494 in @file{limits.h}) to allow range checking on host and target.
40496 @code{time_t} datatypes are defined as seconds since the Epoch.
40498 All integral datatypes transferred as part of a memory read or write of a
40499 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40502 @node Pointer Values
40503 @unnumberedsubsubsec Pointer Values
40504 @cindex pointer values, in file-i/o protocol
40506 Pointers to target data are transmitted as they are. An exception
40507 is made for pointers to buffers for which the length isn't
40508 transmitted as part of the function call, namely strings. Strings
40509 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40516 which is a pointer to data of length 18 bytes at position 0x1aaf.
40517 The length is defined as the full string length in bytes, including
40518 the trailing null byte. For example, the string @code{"hello world"}
40519 at address 0x123456 is transmitted as
40525 @node Memory Transfer
40526 @unnumberedsubsubsec Memory Transfer
40527 @cindex memory transfer, in file-i/o protocol
40529 Structured data which is transferred using a memory read or write (for
40530 example, a @code{struct stat}) is expected to be in a protocol-specific format
40531 with all scalar multibyte datatypes being big endian. Translation to
40532 this representation needs to be done both by the target before the @code{F}
40533 packet is sent, and by @value{GDBN} before
40534 it transfers memory to the target. Transferred pointers to structured
40535 data should point to the already-coerced data at any time.
40539 @unnumberedsubsubsec struct stat
40540 @cindex struct stat, in file-i/o protocol
40542 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40543 is defined as follows:
40547 unsigned int st_dev; /* device */
40548 unsigned int st_ino; /* inode */
40549 mode_t st_mode; /* protection */
40550 unsigned int st_nlink; /* number of hard links */
40551 unsigned int st_uid; /* user ID of owner */
40552 unsigned int st_gid; /* group ID of owner */
40553 unsigned int st_rdev; /* device type (if inode device) */
40554 unsigned long st_size; /* total size, in bytes */
40555 unsigned long st_blksize; /* blocksize for filesystem I/O */
40556 unsigned long st_blocks; /* number of blocks allocated */
40557 time_t st_atime; /* time of last access */
40558 time_t st_mtime; /* time of last modification */
40559 time_t st_ctime; /* time of last change */
40563 The integral datatypes conform to the definitions given in the
40564 appropriate section (see @ref{Integral Datatypes}, for details) so this
40565 structure is of size 64 bytes.
40567 The values of several fields have a restricted meaning and/or
40573 A value of 0 represents a file, 1 the console.
40576 No valid meaning for the target. Transmitted unchanged.
40579 Valid mode bits are described in @ref{Constants}. Any other
40580 bits have currently no meaning for the target.
40585 No valid meaning for the target. Transmitted unchanged.
40590 These values have a host and file system dependent
40591 accuracy. Especially on Windows hosts, the file system may not
40592 support exact timing values.
40595 The target gets a @code{struct stat} of the above representation and is
40596 responsible for coercing it to the target representation before
40599 Note that due to size differences between the host, target, and protocol
40600 representations of @code{struct stat} members, these members could eventually
40601 get truncated on the target.
40603 @node struct timeval
40604 @unnumberedsubsubsec struct timeval
40605 @cindex struct timeval, in file-i/o protocol
40607 The buffer of type @code{struct timeval} used by the File-I/O protocol
40608 is defined as follows:
40612 time_t tv_sec; /* second */
40613 long tv_usec; /* microsecond */
40617 The integral datatypes conform to the definitions given in the
40618 appropriate section (see @ref{Integral Datatypes}, for details) so this
40619 structure is of size 8 bytes.
40622 @subsection Constants
40623 @cindex constants, in file-i/o protocol
40625 The following values are used for the constants inside of the
40626 protocol. @value{GDBN} and target are responsible for translating these
40627 values before and after the call as needed.
40638 @unnumberedsubsubsec Open Flags
40639 @cindex open flags, in file-i/o protocol
40641 All values are given in hexadecimal representation.
40653 @node mode_t Values
40654 @unnumberedsubsubsec mode_t Values
40655 @cindex mode_t values, in file-i/o protocol
40657 All values are given in octal representation.
40674 @unnumberedsubsubsec Errno Values
40675 @cindex errno values, in file-i/o protocol
40677 All values are given in decimal representation.
40702 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40703 any error value not in the list of supported error numbers.
40706 @unnumberedsubsubsec Lseek Flags
40707 @cindex lseek flags, in file-i/o protocol
40716 @unnumberedsubsubsec Limits
40717 @cindex limits, in file-i/o protocol
40719 All values are given in decimal representation.
40722 INT_MIN -2147483648
40724 UINT_MAX 4294967295
40725 LONG_MIN -9223372036854775808
40726 LONG_MAX 9223372036854775807
40727 ULONG_MAX 18446744073709551615
40730 @node File-I/O Examples
40731 @subsection File-I/O Examples
40732 @cindex file-i/o examples
40734 Example sequence of a write call, file descriptor 3, buffer is at target
40735 address 0x1234, 6 bytes should be written:
40738 <- @code{Fwrite,3,1234,6}
40739 @emph{request memory read from target}
40742 @emph{return "6 bytes written"}
40746 Example sequence of a read call, file descriptor 3, buffer is at target
40747 address 0x1234, 6 bytes should be read:
40750 <- @code{Fread,3,1234,6}
40751 @emph{request memory write to target}
40752 -> @code{X1234,6:XXXXXX}
40753 @emph{return "6 bytes read"}
40757 Example sequence of a read call, call fails on the host due to invalid
40758 file descriptor (@code{EBADF}):
40761 <- @code{Fread,3,1234,6}
40765 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40769 <- @code{Fread,3,1234,6}
40774 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40778 <- @code{Fread,3,1234,6}
40779 -> @code{X1234,6:XXXXXX}
40783 @node Library List Format
40784 @section Library List Format
40785 @cindex library list format, remote protocol
40787 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40788 same process as your application to manage libraries. In this case,
40789 @value{GDBN} can use the loader's symbol table and normal memory
40790 operations to maintain a list of shared libraries. On other
40791 platforms, the operating system manages loaded libraries.
40792 @value{GDBN} can not retrieve the list of currently loaded libraries
40793 through memory operations, so it uses the @samp{qXfer:libraries:read}
40794 packet (@pxref{qXfer library list read}) instead. The remote stub
40795 queries the target's operating system and reports which libraries
40798 The @samp{qXfer:libraries:read} packet returns an XML document which
40799 lists loaded libraries and their offsets. Each library has an
40800 associated name and one or more segment or section base addresses,
40801 which report where the library was loaded in memory.
40803 For the common case of libraries that are fully linked binaries, the
40804 library should have a list of segments. If the target supports
40805 dynamic linking of a relocatable object file, its library XML element
40806 should instead include a list of allocated sections. The segment or
40807 section bases are start addresses, not relocation offsets; they do not
40808 depend on the library's link-time base addresses.
40810 @value{GDBN} must be linked with the Expat library to support XML
40811 library lists. @xref{Expat}.
40813 A simple memory map, with one loaded library relocated by a single
40814 offset, looks like this:
40818 <library name="/lib/libc.so.6">
40819 <segment address="0x10000000"/>
40824 Another simple memory map, with one loaded library with three
40825 allocated sections (.text, .data, .bss), looks like this:
40829 <library name="sharedlib.o">
40830 <section address="0x10000000"/>
40831 <section address="0x20000000"/>
40832 <section address="0x30000000"/>
40837 The format of a library list is described by this DTD:
40840 <!-- library-list: Root element with versioning -->
40841 <!ELEMENT library-list (library)*>
40842 <!ATTLIST library-list version CDATA #FIXED "1.0">
40843 <!ELEMENT library (segment*, section*)>
40844 <!ATTLIST library name CDATA #REQUIRED>
40845 <!ELEMENT segment EMPTY>
40846 <!ATTLIST segment address CDATA #REQUIRED>
40847 <!ELEMENT section EMPTY>
40848 <!ATTLIST section address CDATA #REQUIRED>
40851 In addition, segments and section descriptors cannot be mixed within a
40852 single library element, and you must supply at least one segment or
40853 section for each library.
40855 @node Library List Format for SVR4 Targets
40856 @section Library List Format for SVR4 Targets
40857 @cindex library list format, remote protocol
40859 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40860 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40861 shared libraries. Still a special library list provided by this packet is
40862 more efficient for the @value{GDBN} remote protocol.
40864 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40865 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40866 target, the following parameters are reported:
40870 @code{name}, the absolute file name from the @code{l_name} field of
40871 @code{struct link_map}.
40873 @code{lm} with address of @code{struct link_map} used for TLS
40874 (Thread Local Storage) access.
40876 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40877 @code{struct link_map}. For prelinked libraries this is not an absolute
40878 memory address. It is a displacement of absolute memory address against
40879 address the file was prelinked to during the library load.
40881 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40884 Additionally the single @code{main-lm} attribute specifies address of
40885 @code{struct link_map} used for the main executable. This parameter is used
40886 for TLS access and its presence is optional.
40888 @value{GDBN} must be linked with the Expat library to support XML
40889 SVR4 library lists. @xref{Expat}.
40891 A simple memory map, with two loaded libraries (which do not use prelink),
40895 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40896 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40898 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40900 </library-list-svr>
40903 The format of an SVR4 library list is described by this DTD:
40906 <!-- library-list-svr4: Root element with versioning -->
40907 <!ELEMENT library-list-svr4 (library)*>
40908 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40909 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40910 <!ELEMENT library EMPTY>
40911 <!ATTLIST library name CDATA #REQUIRED>
40912 <!ATTLIST library lm CDATA #REQUIRED>
40913 <!ATTLIST library l_addr CDATA #REQUIRED>
40914 <!ATTLIST library l_ld CDATA #REQUIRED>
40917 @node Memory Map Format
40918 @section Memory Map Format
40919 @cindex memory map format
40921 To be able to write into flash memory, @value{GDBN} needs to obtain a
40922 memory map from the target. This section describes the format of the
40925 The memory map is obtained using the @samp{qXfer:memory-map:read}
40926 (@pxref{qXfer memory map read}) packet and is an XML document that
40927 lists memory regions.
40929 @value{GDBN} must be linked with the Expat library to support XML
40930 memory maps. @xref{Expat}.
40932 The top-level structure of the document is shown below:
40935 <?xml version="1.0"?>
40936 <!DOCTYPE memory-map
40937 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40938 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40944 Each region can be either:
40949 A region of RAM starting at @var{addr} and extending for @var{length}
40953 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40958 A region of read-only memory:
40961 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40966 A region of flash memory, with erasure blocks @var{blocksize}
40970 <memory type="flash" start="@var{addr}" length="@var{length}">
40971 <property name="blocksize">@var{blocksize}</property>
40977 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40978 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40979 packets to write to addresses in such ranges.
40981 The formal DTD for memory map format is given below:
40984 <!-- ................................................... -->
40985 <!-- Memory Map XML DTD ................................ -->
40986 <!-- File: memory-map.dtd .............................. -->
40987 <!-- .................................... .............. -->
40988 <!-- memory-map.dtd -->
40989 <!-- memory-map: Root element with versioning -->
40990 <!ELEMENT memory-map (memory)*>
40991 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40992 <!ELEMENT memory (property)*>
40993 <!-- memory: Specifies a memory region,
40994 and its type, or device. -->
40995 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
40996 start CDATA #REQUIRED
40997 length CDATA #REQUIRED>
40998 <!-- property: Generic attribute tag -->
40999 <!ELEMENT property (#PCDATA | property)*>
41000 <!ATTLIST property name (blocksize) #REQUIRED>
41003 @node Thread List Format
41004 @section Thread List Format
41005 @cindex thread list format
41007 To efficiently update the list of threads and their attributes,
41008 @value{GDBN} issues the @samp{qXfer:threads:read} packet
41009 (@pxref{qXfer threads read}) and obtains the XML document with
41010 the following structure:
41013 <?xml version="1.0"?>
41015 <thread id="id" core="0" name="name">
41016 ... description ...
41021 Each @samp{thread} element must have the @samp{id} attribute that
41022 identifies the thread (@pxref{thread-id syntax}). The
41023 @samp{core} attribute, if present, specifies which processor core
41024 the thread was last executing on. The @samp{name} attribute, if
41025 present, specifies the human-readable name of the thread. The content
41026 of the of @samp{thread} element is interpreted as human-readable
41027 auxiliary information. The @samp{handle} attribute, if present,
41028 is a hex encoded representation of the thread handle.
41031 @node Traceframe Info Format
41032 @section Traceframe Info Format
41033 @cindex traceframe info format
41035 To be able to know which objects in the inferior can be examined when
41036 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
41037 memory ranges, registers and trace state variables that have been
41038 collected in a traceframe.
41040 This list is obtained using the @samp{qXfer:traceframe-info:read}
41041 (@pxref{qXfer traceframe info read}) packet and is an XML document.
41043 @value{GDBN} must be linked with the Expat library to support XML
41044 traceframe info discovery. @xref{Expat}.
41046 The top-level structure of the document is shown below:
41049 <?xml version="1.0"?>
41050 <!DOCTYPE traceframe-info
41051 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41052 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
41058 Each traceframe block can be either:
41063 A region of collected memory starting at @var{addr} and extending for
41064 @var{length} bytes from there:
41067 <memory start="@var{addr}" length="@var{length}"/>
41071 A block indicating trace state variable numbered @var{number} has been
41075 <tvar id="@var{number}"/>
41080 The formal DTD for the traceframe info format is given below:
41083 <!ELEMENT traceframe-info (memory | tvar)* >
41084 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
41086 <!ELEMENT memory EMPTY>
41087 <!ATTLIST memory start CDATA #REQUIRED
41088 length CDATA #REQUIRED>
41090 <!ATTLIST tvar id CDATA #REQUIRED>
41093 @node Branch Trace Format
41094 @section Branch Trace Format
41095 @cindex branch trace format
41097 In order to display the branch trace of an inferior thread,
41098 @value{GDBN} needs to obtain the list of branches. This list is
41099 represented as list of sequential code blocks that are connected via
41100 branches. The code in each block has been executed sequentially.
41102 This list is obtained using the @samp{qXfer:btrace:read}
41103 (@pxref{qXfer btrace read}) packet and is an XML document.
41105 @value{GDBN} must be linked with the Expat library to support XML
41106 traceframe info discovery. @xref{Expat}.
41108 The top-level structure of the document is shown below:
41111 <?xml version="1.0"?>
41113 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
41114 "http://sourceware.org/gdb/gdb-btrace.dtd">
41123 A block of sequentially executed instructions starting at @var{begin}
41124 and ending at @var{end}:
41127 <block begin="@var{begin}" end="@var{end}"/>
41132 The formal DTD for the branch trace format is given below:
41135 <!ELEMENT btrace (block* | pt) >
41136 <!ATTLIST btrace version CDATA #FIXED "1.0">
41138 <!ELEMENT block EMPTY>
41139 <!ATTLIST block begin CDATA #REQUIRED
41140 end CDATA #REQUIRED>
41142 <!ELEMENT pt (pt-config?, raw?)>
41144 <!ELEMENT pt-config (cpu?)>
41146 <!ELEMENT cpu EMPTY>
41147 <!ATTLIST cpu vendor CDATA #REQUIRED
41148 family CDATA #REQUIRED
41149 model CDATA #REQUIRED
41150 stepping CDATA #REQUIRED>
41152 <!ELEMENT raw (#PCDATA)>
41155 @node Branch Trace Configuration Format
41156 @section Branch Trace Configuration Format
41157 @cindex branch trace configuration format
41159 For each inferior thread, @value{GDBN} can obtain the branch trace
41160 configuration using the @samp{qXfer:btrace-conf:read}
41161 (@pxref{qXfer btrace-conf read}) packet.
41163 The configuration describes the branch trace format and configuration
41164 settings for that format. The following information is described:
41168 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
41171 The size of the @acronym{BTS} ring buffer in bytes.
41174 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
41178 The size of the @acronym{Intel PT} ring buffer in bytes.
41182 @value{GDBN} must be linked with the Expat library to support XML
41183 branch trace configuration discovery. @xref{Expat}.
41185 The formal DTD for the branch trace configuration format is given below:
41188 <!ELEMENT btrace-conf (bts?, pt?)>
41189 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
41191 <!ELEMENT bts EMPTY>
41192 <!ATTLIST bts size CDATA #IMPLIED>
41194 <!ELEMENT pt EMPTY>
41195 <!ATTLIST pt size CDATA #IMPLIED>
41198 @include agentexpr.texi
41200 @node Target Descriptions
41201 @appendix Target Descriptions
41202 @cindex target descriptions
41204 One of the challenges of using @value{GDBN} to debug embedded systems
41205 is that there are so many minor variants of each processor
41206 architecture in use. It is common practice for vendors to start with
41207 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
41208 and then make changes to adapt it to a particular market niche. Some
41209 architectures have hundreds of variants, available from dozens of
41210 vendors. This leads to a number of problems:
41214 With so many different customized processors, it is difficult for
41215 the @value{GDBN} maintainers to keep up with the changes.
41217 Since individual variants may have short lifetimes or limited
41218 audiences, it may not be worthwhile to carry information about every
41219 variant in the @value{GDBN} source tree.
41221 When @value{GDBN} does support the architecture of the embedded system
41222 at hand, the task of finding the correct architecture name to give the
41223 @command{set architecture} command can be error-prone.
41226 To address these problems, the @value{GDBN} remote protocol allows a
41227 target system to not only identify itself to @value{GDBN}, but to
41228 actually describe its own features. This lets @value{GDBN} support
41229 processor variants it has never seen before --- to the extent that the
41230 descriptions are accurate, and that @value{GDBN} understands them.
41232 @value{GDBN} must be linked with the Expat library to support XML
41233 target descriptions. @xref{Expat}.
41236 * Retrieving Descriptions:: How descriptions are fetched from a target.
41237 * Target Description Format:: The contents of a target description.
41238 * Predefined Target Types:: Standard types available for target
41240 * Enum Target Types:: How to define enum target types.
41241 * Standard Target Features:: Features @value{GDBN} knows about.
41244 @node Retrieving Descriptions
41245 @section Retrieving Descriptions
41247 Target descriptions can be read from the target automatically, or
41248 specified by the user manually. The default behavior is to read the
41249 description from the target. @value{GDBN} retrieves it via the remote
41250 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
41251 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
41252 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
41253 XML document, of the form described in @ref{Target Description
41256 Alternatively, you can specify a file to read for the target description.
41257 If a file is set, the target will not be queried. The commands to
41258 specify a file are:
41261 @cindex set tdesc filename
41262 @item set tdesc filename @var{path}
41263 Read the target description from @var{path}.
41265 @cindex unset tdesc filename
41266 @item unset tdesc filename
41267 Do not read the XML target description from a file. @value{GDBN}
41268 will use the description supplied by the current target.
41270 @cindex show tdesc filename
41271 @item show tdesc filename
41272 Show the filename to read for a target description, if any.
41276 @node Target Description Format
41277 @section Target Description Format
41278 @cindex target descriptions, XML format
41280 A target description annex is an @uref{http://www.w3.org/XML/, XML}
41281 document which complies with the Document Type Definition provided in
41282 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
41283 means you can use generally available tools like @command{xmllint} to
41284 check that your feature descriptions are well-formed and valid.
41285 However, to help people unfamiliar with XML write descriptions for
41286 their targets, we also describe the grammar here.
41288 Target descriptions can identify the architecture of the remote target
41289 and (for some architectures) provide information about custom register
41290 sets. They can also identify the OS ABI of the remote target.
41291 @value{GDBN} can use this information to autoconfigure for your
41292 target, or to warn you if you connect to an unsupported target.
41294 Here is a simple target description:
41297 <target version="1.0">
41298 <architecture>i386:x86-64</architecture>
41303 This minimal description only says that the target uses
41304 the x86-64 architecture.
41306 A target description has the following overall form, with [ ] marking
41307 optional elements and @dots{} marking repeatable elements. The elements
41308 are explained further below.
41311 <?xml version="1.0"?>
41312 <!DOCTYPE target SYSTEM "gdb-target.dtd">
41313 <target version="1.0">
41314 @r{[}@var{architecture}@r{]}
41315 @r{[}@var{osabi}@r{]}
41316 @r{[}@var{compatible}@r{]}
41317 @r{[}@var{feature}@dots{}@r{]}
41322 The description is generally insensitive to whitespace and line
41323 breaks, under the usual common-sense rules. The XML version
41324 declaration and document type declaration can generally be omitted
41325 (@value{GDBN} does not require them), but specifying them may be
41326 useful for XML validation tools. The @samp{version} attribute for
41327 @samp{<target>} may also be omitted, but we recommend
41328 including it; if future versions of @value{GDBN} use an incompatible
41329 revision of @file{gdb-target.dtd}, they will detect and report
41330 the version mismatch.
41332 @subsection Inclusion
41333 @cindex target descriptions, inclusion
41336 @cindex <xi:include>
41339 It can sometimes be valuable to split a target description up into
41340 several different annexes, either for organizational purposes, or to
41341 share files between different possible target descriptions. You can
41342 divide a description into multiple files by replacing any element of
41343 the target description with an inclusion directive of the form:
41346 <xi:include href="@var{document}"/>
41350 When @value{GDBN} encounters an element of this form, it will retrieve
41351 the named XML @var{document}, and replace the inclusion directive with
41352 the contents of that document. If the current description was read
41353 using @samp{qXfer}, then so will be the included document;
41354 @var{document} will be interpreted as the name of an annex. If the
41355 current description was read from a file, @value{GDBN} will look for
41356 @var{document} as a file in the same directory where it found the
41357 original description.
41359 @subsection Architecture
41360 @cindex <architecture>
41362 An @samp{<architecture>} element has this form:
41365 <architecture>@var{arch}</architecture>
41368 @var{arch} is one of the architectures from the set accepted by
41369 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41372 @cindex @code{<osabi>}
41374 This optional field was introduced in @value{GDBN} version 7.0.
41375 Previous versions of @value{GDBN} ignore it.
41377 An @samp{<osabi>} element has this form:
41380 <osabi>@var{abi-name}</osabi>
41383 @var{abi-name} is an OS ABI name from the same selection accepted by
41384 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
41386 @subsection Compatible Architecture
41387 @cindex @code{<compatible>}
41389 This optional field was introduced in @value{GDBN} version 7.0.
41390 Previous versions of @value{GDBN} ignore it.
41392 A @samp{<compatible>} element has this form:
41395 <compatible>@var{arch}</compatible>
41398 @var{arch} is one of the architectures from the set accepted by
41399 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41401 A @samp{<compatible>} element is used to specify that the target
41402 is able to run binaries in some other than the main target architecture
41403 given by the @samp{<architecture>} element. For example, on the
41404 Cell Broadband Engine, the main architecture is @code{powerpc:common}
41405 or @code{powerpc:common64}, but the system is able to run binaries
41406 in the @code{spu} architecture as well. The way to describe this
41407 capability with @samp{<compatible>} is as follows:
41410 <architecture>powerpc:common</architecture>
41411 <compatible>spu</compatible>
41414 @subsection Features
41417 Each @samp{<feature>} describes some logical portion of the target
41418 system. Features are currently used to describe available CPU
41419 registers and the types of their contents. A @samp{<feature>} element
41423 <feature name="@var{name}">
41424 @r{[}@var{type}@dots{}@r{]}
41430 Each feature's name should be unique within the description. The name
41431 of a feature does not matter unless @value{GDBN} has some special
41432 knowledge of the contents of that feature; if it does, the feature
41433 should have its standard name. @xref{Standard Target Features}.
41437 Any register's value is a collection of bits which @value{GDBN} must
41438 interpret. The default interpretation is a two's complement integer,
41439 but other types can be requested by name in the register description.
41440 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
41441 Target Types}), and the description can define additional composite
41444 Each type element must have an @samp{id} attribute, which gives
41445 a unique (within the containing @samp{<feature>}) name to the type.
41446 Types must be defined before they are used.
41449 Some targets offer vector registers, which can be treated as arrays
41450 of scalar elements. These types are written as @samp{<vector>} elements,
41451 specifying the array element type, @var{type}, and the number of elements,
41455 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
41459 If a register's value is usefully viewed in multiple ways, define it
41460 with a union type containing the useful representations. The
41461 @samp{<union>} element contains one or more @samp{<field>} elements,
41462 each of which has a @var{name} and a @var{type}:
41465 <union id="@var{id}">
41466 <field name="@var{name}" type="@var{type}"/>
41473 If a register's value is composed from several separate values, define
41474 it with either a structure type or a flags type.
41475 A flags type may only contain bitfields.
41476 A structure type may either contain only bitfields or contain no bitfields.
41477 If the value contains only bitfields, its total size in bytes must be
41480 Non-bitfield values have a @var{name} and @var{type}.
41483 <struct id="@var{id}">
41484 <field name="@var{name}" type="@var{type}"/>
41489 Both @var{name} and @var{type} values are required.
41490 No implicit padding is added.
41492 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
41495 <struct id="@var{id}" size="@var{size}">
41496 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41502 <flags id="@var{id}" size="@var{size}">
41503 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41508 The @var{name} value is required.
41509 Bitfield values may be named with the empty string, @samp{""},
41510 in which case the field is ``filler'' and its value is not printed.
41511 Not all bits need to be specified, so ``filler'' fields are optional.
41513 The @var{start} and @var{end} values are required, and @var{type}
41515 The field's @var{start} must be less than or equal to its @var{end},
41516 and zero represents the least significant bit.
41518 The default value of @var{type} is @code{bool} for single bit fields,
41519 and an unsigned integer otherwise.
41521 Which to choose? Structures or flags?
41523 Registers defined with @samp{flags} have these advantages over
41524 defining them with @samp{struct}:
41528 Arithmetic may be performed on them as if they were integers.
41530 They are printed in a more readable fashion.
41533 Registers defined with @samp{struct} have one advantage over
41534 defining them with @samp{flags}:
41538 One can fetch individual fields like in @samp{C}.
41541 (gdb) print $my_struct_reg.field3
41547 @subsection Registers
41550 Each register is represented as an element with this form:
41553 <reg name="@var{name}"
41554 bitsize="@var{size}"
41555 @r{[}regnum="@var{num}"@r{]}
41556 @r{[}save-restore="@var{save-restore}"@r{]}
41557 @r{[}type="@var{type}"@r{]}
41558 @r{[}group="@var{group}"@r{]}/>
41562 The components are as follows:
41567 The register's name; it must be unique within the target description.
41570 The register's size, in bits.
41573 The register's number. If omitted, a register's number is one greater
41574 than that of the previous register (either in the current feature or in
41575 a preceding feature); the first register in the target description
41576 defaults to zero. This register number is used to read or write
41577 the register; e.g.@: it is used in the remote @code{p} and @code{P}
41578 packets, and registers appear in the @code{g} and @code{G} packets
41579 in order of increasing register number.
41582 Whether the register should be preserved across inferior function
41583 calls; this must be either @code{yes} or @code{no}. The default is
41584 @code{yes}, which is appropriate for most registers except for
41585 some system control registers; this is not related to the target's
41589 The type of the register. It may be a predefined type, a type
41590 defined in the current feature, or one of the special types @code{int}
41591 and @code{float}. @code{int} is an integer type of the correct size
41592 for @var{bitsize}, and @code{float} is a floating point type (in the
41593 architecture's normal floating point format) of the correct size for
41594 @var{bitsize}. The default is @code{int}.
41597 The register group to which this register belongs. It must
41598 be either @code{general}, @code{float}, or @code{vector}. If no
41599 @var{group} is specified, @value{GDBN} will not display the register
41600 in @code{info registers}.
41604 @node Predefined Target Types
41605 @section Predefined Target Types
41606 @cindex target descriptions, predefined types
41608 Type definitions in the self-description can build up composite types
41609 from basic building blocks, but can not define fundamental types. Instead,
41610 standard identifiers are provided by @value{GDBN} for the fundamental
41611 types. The currently supported types are:
41616 Boolean type, occupying a single bit.
41623 Signed integer types holding the specified number of bits.
41630 Unsigned integer types holding the specified number of bits.
41634 Pointers to unspecified code and data. The program counter and
41635 any dedicated return address register may be marked as code
41636 pointers; printing a code pointer converts it into a symbolic
41637 address. The stack pointer and any dedicated address registers
41638 may be marked as data pointers.
41641 Single precision IEEE floating point.
41644 Double precision IEEE floating point.
41647 The 12-byte extended precision format used by ARM FPA registers.
41650 The 10-byte extended precision format used by x87 registers.
41653 32bit @sc{eflags} register used by x86.
41656 32bit @sc{mxcsr} register used by x86.
41660 @node Enum Target Types
41661 @section Enum Target Types
41662 @cindex target descriptions, enum types
41664 Enum target types are useful in @samp{struct} and @samp{flags}
41665 register descriptions. @xref{Target Description Format}.
41667 Enum types have a name, size and a list of name/value pairs.
41670 <enum id="@var{id}" size="@var{size}">
41671 <evalue name="@var{name}" value="@var{value}"/>
41676 Enums must be defined before they are used.
41679 <enum id="levels_type" size="4">
41680 <evalue name="low" value="0"/>
41681 <evalue name="high" value="1"/>
41683 <flags id="flags_type" size="4">
41684 <field name="X" start="0"/>
41685 <field name="LEVEL" start="1" end="1" type="levels_type"/>
41687 <reg name="flags" bitsize="32" type="flags_type"/>
41690 Given that description, a value of 3 for the @samp{flags} register
41691 would be printed as:
41694 (gdb) info register flags
41695 flags 0x3 [ X LEVEL=high ]
41698 @node Standard Target Features
41699 @section Standard Target Features
41700 @cindex target descriptions, standard features
41702 A target description must contain either no registers or all the
41703 target's registers. If the description contains no registers, then
41704 @value{GDBN} will assume a default register layout, selected based on
41705 the architecture. If the description contains any registers, the
41706 default layout will not be used; the standard registers must be
41707 described in the target description, in such a way that @value{GDBN}
41708 can recognize them.
41710 This is accomplished by giving specific names to feature elements
41711 which contain standard registers. @value{GDBN} will look for features
41712 with those names and verify that they contain the expected registers;
41713 if any known feature is missing required registers, or if any required
41714 feature is missing, @value{GDBN} will reject the target
41715 description. You can add additional registers to any of the
41716 standard features --- @value{GDBN} will display them just as if
41717 they were added to an unrecognized feature.
41719 This section lists the known features and their expected contents.
41720 Sample XML documents for these features are included in the
41721 @value{GDBN} source tree, in the directory @file{gdb/features}.
41723 Names recognized by @value{GDBN} should include the name of the
41724 company or organization which selected the name, and the overall
41725 architecture to which the feature applies; so e.g.@: the feature
41726 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41728 The names of registers are not case sensitive for the purpose
41729 of recognizing standard features, but @value{GDBN} will only display
41730 registers using the capitalization used in the description.
41733 * AArch64 Features::
41737 * MicroBlaze Features::
41741 * Nios II Features::
41742 * PowerPC Features::
41743 * S/390 and System z Features::
41749 @node AArch64 Features
41750 @subsection AArch64 Features
41751 @cindex target descriptions, AArch64 features
41753 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41754 targets. It should contain registers @samp{x0} through @samp{x30},
41755 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41757 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41758 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41762 @subsection ARC Features
41763 @cindex target descriptions, ARC Features
41765 ARC processors are highly configurable, so even core registers and their number
41766 are not completely predetermined. In addition flags and PC registers which are
41767 important to @value{GDBN} are not ``core'' registers in ARC. It is required
41768 that one of the core registers features is present.
41769 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
41771 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
41772 targets with a normal register file. It should contain registers @samp{r0}
41773 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41774 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
41775 and any of extension core registers @samp{r32} through @samp{r59/acch}.
41776 @samp{ilink} and extension core registers are not available to read/write, when
41777 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
41779 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
41780 ARC HS targets with a reduced register file. It should contain registers
41781 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
41782 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
41783 This feature may contain register @samp{ilink} and any of extension core
41784 registers @samp{r32} through @samp{r59/acch}.
41786 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
41787 targets with a normal register file. It should contain registers @samp{r0}
41788 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41789 @samp{lp_count} and @samp{pcl}. This feature may contain registers
41790 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
41791 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
41792 registers are not available when debugging GNU/Linux applications. The only
41793 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
41794 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
41795 ARC v2, but @samp{ilink2} is optional on ARCompact.
41797 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
41798 targets. It should contain registers @samp{pc} and @samp{status32}.
41801 @subsection ARM Features
41802 @cindex target descriptions, ARM features
41804 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41806 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41807 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41809 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41810 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41811 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41814 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41815 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41817 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41818 it should contain at least registers @samp{wR0} through @samp{wR15} and
41819 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41820 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41822 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41823 should contain at least registers @samp{d0} through @samp{d15}. If
41824 they are present, @samp{d16} through @samp{d31} should also be included.
41825 @value{GDBN} will synthesize the single-precision registers from
41826 halves of the double-precision registers.
41828 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41829 need to contain registers; it instructs @value{GDBN} to display the
41830 VFP double-precision registers as vectors and to synthesize the
41831 quad-precision registers from pairs of double-precision registers.
41832 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41833 be present and include 32 double-precision registers.
41835 @node i386 Features
41836 @subsection i386 Features
41837 @cindex target descriptions, i386 features
41839 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41840 targets. It should describe the following registers:
41844 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41846 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41848 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41849 @samp{fs}, @samp{gs}
41851 @samp{st0} through @samp{st7}
41853 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41854 @samp{foseg}, @samp{fooff} and @samp{fop}
41857 The register sets may be different, depending on the target.
41859 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41860 describe registers:
41864 @samp{xmm0} through @samp{xmm7} for i386
41866 @samp{xmm0} through @samp{xmm15} for amd64
41871 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41872 @samp{org.gnu.gdb.i386.sse} feature. It should
41873 describe the upper 128 bits of @sc{ymm} registers:
41877 @samp{ymm0h} through @samp{ymm7h} for i386
41879 @samp{ymm0h} through @samp{ymm15h} for amd64
41882 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
41883 Memory Protection Extension (MPX). It should describe the following registers:
41887 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
41889 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
41892 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41893 describe a single register, @samp{orig_eax}.
41895 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
41896 describe two system registers: @samp{fs_base} and @samp{gs_base}.
41898 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
41899 @samp{org.gnu.gdb.i386.avx} feature. It should
41900 describe additional @sc{xmm} registers:
41904 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
41907 It should describe the upper 128 bits of additional @sc{ymm} registers:
41911 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
41915 describe the upper 256 bits of @sc{zmm} registers:
41919 @samp{zmm0h} through @samp{zmm7h} for i386.
41921 @samp{zmm0h} through @samp{zmm15h} for amd64.
41925 describe the additional @sc{zmm} registers:
41929 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
41932 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
41933 describe a single register, @samp{pkru}. It is a 32-bit register
41934 valid for i386 and amd64.
41936 @node MicroBlaze Features
41937 @subsection MicroBlaze Features
41938 @cindex target descriptions, MicroBlaze features
41940 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
41941 targets. It should contain registers @samp{r0} through @samp{r31},
41942 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
41943 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
41944 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
41946 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
41947 If present, it should contain registers @samp{rshr} and @samp{rslr}
41949 @node MIPS Features
41950 @subsection @acronym{MIPS} Features
41951 @cindex target descriptions, @acronym{MIPS} features
41953 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41954 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41955 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41958 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41959 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41960 registers. They may be 32-bit or 64-bit depending on the target.
41962 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41963 it may be optional in a future version of @value{GDBN}. It should
41964 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41965 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41967 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41968 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41969 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41970 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41972 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41973 contain a single register, @samp{restart}, which is used by the
41974 Linux kernel to control restartable syscalls.
41976 @node M68K Features
41977 @subsection M68K Features
41978 @cindex target descriptions, M68K features
41981 @item @samp{org.gnu.gdb.m68k.core}
41982 @itemx @samp{org.gnu.gdb.coldfire.core}
41983 @itemx @samp{org.gnu.gdb.fido.core}
41984 One of those features must be always present.
41985 The feature that is present determines which flavor of m68k is
41986 used. The feature that is present should contain registers
41987 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41988 @samp{sp}, @samp{ps} and @samp{pc}.
41990 @item @samp{org.gnu.gdb.coldfire.fp}
41991 This feature is optional. If present, it should contain registers
41992 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41996 @node NDS32 Features
41997 @subsection NDS32 Features
41998 @cindex target descriptions, NDS32 features
42000 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
42001 targets. It should contain at least registers @samp{r0} through
42002 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
42005 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
42006 it should contain 64-bit double-precision floating-point registers
42007 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
42008 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
42010 @emph{Note:} The first sixteen 64-bit double-precision floating-point
42011 registers are overlapped with the thirty-two 32-bit single-precision
42012 floating-point registers. The 32-bit single-precision registers, if
42013 not being listed explicitly, will be synthesized from halves of the
42014 overlapping 64-bit double-precision registers. Listing 32-bit
42015 single-precision registers explicitly is deprecated, and the
42016 support to it could be totally removed some day.
42018 @node Nios II Features
42019 @subsection Nios II Features
42020 @cindex target descriptions, Nios II features
42022 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
42023 targets. It should contain the 32 core registers (@samp{zero},
42024 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
42025 @samp{pc}, and the 16 control registers (@samp{status} through
42028 @node PowerPC Features
42029 @subsection PowerPC Features
42030 @cindex target descriptions, PowerPC features
42032 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
42033 targets. It should contain registers @samp{r0} through @samp{r31},
42034 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
42035 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
42037 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
42038 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
42040 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
42041 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
42044 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
42045 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
42046 will combine these registers with the floating point registers
42047 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
42048 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
42049 through @samp{vs63}, the set of vector registers for POWER7.
42051 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
42052 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
42053 @samp{spefscr}. SPE targets should provide 32-bit registers in
42054 @samp{org.gnu.gdb.power.core} and provide the upper halves in
42055 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
42056 these to present registers @samp{ev0} through @samp{ev31} to the
42059 @node S/390 and System z Features
42060 @subsection S/390 and System z Features
42061 @cindex target descriptions, S/390 features
42062 @cindex target descriptions, System z features
42064 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
42065 System z targets. It should contain the PSW and the 16 general
42066 registers. In particular, System z targets should provide the 64-bit
42067 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
42068 S/390 targets should provide the 32-bit versions of these registers.
42069 A System z target that runs in 31-bit addressing mode should provide
42070 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
42071 register's upper halves @samp{r0h} through @samp{r15h}, and their
42072 lower halves @samp{r0l} through @samp{r15l}.
42074 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
42075 contain the 64-bit registers @samp{f0} through @samp{f15}, and
42078 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
42079 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
42081 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
42082 contain the register @samp{orig_r2}, which is 64-bit wide on System z
42083 targets and 32-bit otherwise. In addition, the feature may contain
42084 the @samp{last_break} register, whose width depends on the addressing
42085 mode, as well as the @samp{system_call} register, which is always
42088 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
42089 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
42090 @samp{atia}, and @samp{tr0} through @samp{tr15}.
42092 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
42093 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
42094 combined by @value{GDBN} with the floating point registers @samp{f0}
42095 through @samp{f15} to present the 128-bit wide vector registers
42096 @samp{v0} through @samp{v15}. In addition, this feature should
42097 contain the 128-bit wide vector registers @samp{v16} through
42100 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
42101 the 64-bit wide guarded-storage-control registers @samp{gsd},
42102 @samp{gssm}, and @samp{gsepla}.
42104 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
42105 the 64-bit wide guarded-storage broadcast control registers
42106 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
42108 @node Sparc Features
42109 @subsection Sparc Features
42110 @cindex target descriptions, sparc32 features
42111 @cindex target descriptions, sparc64 features
42112 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
42113 targets. It should describe the following registers:
42117 @samp{g0} through @samp{g7}
42119 @samp{o0} through @samp{o7}
42121 @samp{l0} through @samp{l7}
42123 @samp{i0} through @samp{i7}
42126 They may be 32-bit or 64-bit depending on the target.
42128 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
42129 targets. It should describe the following registers:
42133 @samp{f0} through @samp{f31}
42135 @samp{f32} through @samp{f62} for sparc64
42138 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
42139 targets. It should describe the following registers:
42143 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
42144 @samp{fsr}, and @samp{csr} for sparc32
42146 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
42150 @node TIC6x Features
42151 @subsection TMS320C6x Features
42152 @cindex target descriptions, TIC6x features
42153 @cindex target descriptions, TMS320C6x features
42154 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
42155 targets. It should contain registers @samp{A0} through @samp{A15},
42156 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
42158 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
42159 contain registers @samp{A16} through @samp{A31} and @samp{B16}
42160 through @samp{B31}.
42162 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
42163 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
42165 @node Operating System Information
42166 @appendix Operating System Information
42167 @cindex operating system information
42173 Users of @value{GDBN} often wish to obtain information about the state of
42174 the operating system running on the target---for example the list of
42175 processes, or the list of open files. This section describes the
42176 mechanism that makes it possible. This mechanism is similar to the
42177 target features mechanism (@pxref{Target Descriptions}), but focuses
42178 on a different aspect of target.
42180 Operating system information is retrived from the target via the
42181 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
42182 read}). The object name in the request should be @samp{osdata}, and
42183 the @var{annex} identifies the data to be fetched.
42186 @appendixsection Process list
42187 @cindex operating system information, process list
42189 When requesting the process list, the @var{annex} field in the
42190 @samp{qXfer} request should be @samp{processes}. The returned data is
42191 an XML document. The formal syntax of this document is defined in
42192 @file{gdb/features/osdata.dtd}.
42194 An example document is:
42197 <?xml version="1.0"?>
42198 <!DOCTYPE target SYSTEM "osdata.dtd">
42199 <osdata type="processes">
42201 <column name="pid">1</column>
42202 <column name="user">root</column>
42203 <column name="command">/sbin/init</column>
42204 <column name="cores">1,2,3</column>
42209 Each item should include a column whose name is @samp{pid}. The value
42210 of that column should identify the process on the target. The
42211 @samp{user} and @samp{command} columns are optional, and will be
42212 displayed by @value{GDBN}. The @samp{cores} column, if present,
42213 should contain a comma-separated list of cores that this process
42214 is running on. Target may provide additional columns,
42215 which @value{GDBN} currently ignores.
42217 @node Trace File Format
42218 @appendix Trace File Format
42219 @cindex trace file format
42221 The trace file comes in three parts: a header, a textual description
42222 section, and a trace frame section with binary data.
42224 The header has the form @code{\x7fTRACE0\n}. The first byte is
42225 @code{0x7f} so as to indicate that the file contains binary data,
42226 while the @code{0} is a version number that may have different values
42229 The description section consists of multiple lines of @sc{ascii} text
42230 separated by newline characters (@code{0xa}). The lines may include a
42231 variety of optional descriptive or context-setting information, such
42232 as tracepoint definitions or register set size. @value{GDBN} will
42233 ignore any line that it does not recognize. An empty line marks the end
42238 Specifies the size of a register block in bytes. This is equal to the
42239 size of a @code{g} packet payload in the remote protocol. @var{size}
42240 is an ascii decimal number. There should be only one such line in
42241 a single trace file.
42243 @item status @var{status}
42244 Trace status. @var{status} has the same format as a @code{qTStatus}
42245 remote packet reply. There should be only one such line in a single trace
42248 @item tp @var{payload}
42249 Tracepoint definition. The @var{payload} has the same format as
42250 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
42251 may take multiple lines of definition, corresponding to the multiple
42254 @item tsv @var{payload}
42255 Trace state variable definition. The @var{payload} has the same format as
42256 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
42257 may take multiple lines of definition, corresponding to the multiple
42260 @item tdesc @var{payload}
42261 Target description in XML format. The @var{payload} is a single line of
42262 the XML file. All such lines should be concatenated together to get
42263 the original XML file. This file is in the same format as @code{qXfer}
42264 @code{features} payload, and corresponds to the main @code{target.xml}
42265 file. Includes are not allowed.
42269 The trace frame section consists of a number of consecutive frames.
42270 Each frame begins with a two-byte tracepoint number, followed by a
42271 four-byte size giving the amount of data in the frame. The data in
42272 the frame consists of a number of blocks, each introduced by a
42273 character indicating its type (at least register, memory, and trace
42274 state variable). The data in this section is raw binary, not a
42275 hexadecimal or other encoding; its endianness matches the target's
42278 @c FIXME bi-arch may require endianness/arch info in description section
42281 @item R @var{bytes}
42282 Register block. The number and ordering of bytes matches that of a
42283 @code{g} packet in the remote protocol. Note that these are the
42284 actual bytes, in target order, not a hexadecimal encoding.
42286 @item M @var{address} @var{length} @var{bytes}...
42287 Memory block. This is a contiguous block of memory, at the 8-byte
42288 address @var{address}, with a 2-byte length @var{length}, followed by
42289 @var{length} bytes.
42291 @item V @var{number} @var{value}
42292 Trace state variable block. This records the 8-byte signed value
42293 @var{value} of trace state variable numbered @var{number}.
42297 Future enhancements of the trace file format may include additional types
42300 @node Index Section Format
42301 @appendix @code{.gdb_index} section format
42302 @cindex .gdb_index section format
42303 @cindex index section format
42305 This section documents the index section that is created by @code{save
42306 gdb-index} (@pxref{Index Files}). The index section is
42307 DWARF-specific; some knowledge of DWARF is assumed in this
42310 The mapped index file format is designed to be directly
42311 @code{mmap}able on any architecture. In most cases, a datum is
42312 represented using a little-endian 32-bit integer value, called an
42313 @code{offset_type}. Big endian machines must byte-swap the values
42314 before using them. Exceptions to this rule are noted. The data is
42315 laid out such that alignment is always respected.
42317 A mapped index consists of several areas, laid out in order.
42321 The file header. This is a sequence of values, of @code{offset_type}
42322 unless otherwise noted:
42326 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
42327 Version 4 uses a different hashing function from versions 5 and 6.
42328 Version 6 includes symbols for inlined functions, whereas versions 4
42329 and 5 do not. Version 7 adds attributes to the CU indices in the
42330 symbol table. Version 8 specifies that symbols from DWARF type units
42331 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
42332 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
42334 @value{GDBN} will only read version 4, 5, or 6 indices
42335 by specifying @code{set use-deprecated-index-sections on}.
42336 GDB has a workaround for potentially broken version 7 indices so it is
42337 currently not flagged as deprecated.
42340 The offset, from the start of the file, of the CU list.
42343 The offset, from the start of the file, of the types CU list. Note
42344 that this area can be empty, in which case this offset will be equal
42345 to the next offset.
42348 The offset, from the start of the file, of the address area.
42351 The offset, from the start of the file, of the symbol table.
42354 The offset, from the start of the file, of the constant pool.
42358 The CU list. This is a sequence of pairs of 64-bit little-endian
42359 values, sorted by the CU offset. The first element in each pair is
42360 the offset of a CU in the @code{.debug_info} section. The second
42361 element in each pair is the length of that CU. References to a CU
42362 elsewhere in the map are done using a CU index, which is just the
42363 0-based index into this table. Note that if there are type CUs, then
42364 conceptually CUs and type CUs form a single list for the purposes of
42368 The types CU list. This is a sequence of triplets of 64-bit
42369 little-endian values. In a triplet, the first value is the CU offset,
42370 the second value is the type offset in the CU, and the third value is
42371 the type signature. The types CU list is not sorted.
42374 The address area. The address area consists of a sequence of address
42375 entries. Each address entry has three elements:
42379 The low address. This is a 64-bit little-endian value.
42382 The high address. This is a 64-bit little-endian value. Like
42383 @code{DW_AT_high_pc}, the value is one byte beyond the end.
42386 The CU index. This is an @code{offset_type} value.
42390 The symbol table. This is an open-addressed hash table. The size of
42391 the hash table is always a power of 2.
42393 Each slot in the hash table consists of a pair of @code{offset_type}
42394 values. The first value is the offset of the symbol's name in the
42395 constant pool. The second value is the offset of the CU vector in the
42398 If both values are 0, then this slot in the hash table is empty. This
42399 is ok because while 0 is a valid constant pool index, it cannot be a
42400 valid index for both a string and a CU vector.
42402 The hash value for a table entry is computed by applying an
42403 iterative hash function to the symbol's name. Starting with an
42404 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
42405 the string is incorporated into the hash using the formula depending on the
42410 The formula is @code{r = r * 67 + c - 113}.
42412 @item Versions 5 to 7
42413 The formula is @code{r = r * 67 + tolower (c) - 113}.
42416 The terminating @samp{\0} is not incorporated into the hash.
42418 The step size used in the hash table is computed via
42419 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
42420 value, and @samp{size} is the size of the hash table. The step size
42421 is used to find the next candidate slot when handling a hash
42424 The names of C@t{++} symbols in the hash table are canonicalized. We
42425 don't currently have a simple description of the canonicalization
42426 algorithm; if you intend to create new index sections, you must read
42430 The constant pool. This is simply a bunch of bytes. It is organized
42431 so that alignment is correct: CU vectors are stored first, followed by
42434 A CU vector in the constant pool is a sequence of @code{offset_type}
42435 values. The first value is the number of CU indices in the vector.
42436 Each subsequent value is the index and symbol attributes of a CU in
42437 the CU list. This element in the hash table is used to indicate which
42438 CUs define the symbol and how the symbol is used.
42439 See below for the format of each CU index+attributes entry.
42441 A string in the constant pool is zero-terminated.
42444 Attributes were added to CU index values in @code{.gdb_index} version 7.
42445 If a symbol has multiple uses within a CU then there is one
42446 CU index+attributes value for each use.
42448 The format of each CU index+attributes entry is as follows
42454 This is the index of the CU in the CU list.
42456 These bits are reserved for future purposes and must be zero.
42458 The kind of the symbol in the CU.
42462 This value is reserved and should not be used.
42463 By reserving zero the full @code{offset_type} value is backwards compatible
42464 with previous versions of the index.
42466 The symbol is a type.
42468 The symbol is a variable or an enum value.
42470 The symbol is a function.
42472 Any other kind of symbol.
42474 These values are reserved.
42478 This bit is zero if the value is global and one if it is static.
42480 The determination of whether a symbol is global or static is complicated.
42481 The authorative reference is the file @file{dwarf2read.c} in
42482 @value{GDBN} sources.
42486 This pseudo-code describes the computation of a symbol's kind and
42487 global/static attributes in the index.
42490 is_external = get_attribute (die, DW_AT_external);
42491 language = get_attribute (cu_die, DW_AT_language);
42494 case DW_TAG_typedef:
42495 case DW_TAG_base_type:
42496 case DW_TAG_subrange_type:
42500 case DW_TAG_enumerator:
42502 is_static = language != CPLUS;
42504 case DW_TAG_subprogram:
42506 is_static = ! (is_external || language == ADA);
42508 case DW_TAG_constant:
42510 is_static = ! is_external;
42512 case DW_TAG_variable:
42514 is_static = ! is_external;
42516 case DW_TAG_namespace:
42520 case DW_TAG_class_type:
42521 case DW_TAG_interface_type:
42522 case DW_TAG_structure_type:
42523 case DW_TAG_union_type:
42524 case DW_TAG_enumeration_type:
42526 is_static = language != CPLUS;
42534 @appendix Manual pages
42538 * gdb man:: The GNU Debugger man page
42539 * gdbserver man:: Remote Server for the GNU Debugger man page
42540 * gcore man:: Generate a core file of a running program
42541 * gdbinit man:: gdbinit scripts
42547 @c man title gdb The GNU Debugger
42549 @c man begin SYNOPSIS gdb
42550 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
42551 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
42552 [@option{-b}@w{ }@var{bps}]
42553 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
42554 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
42555 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
42556 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
42557 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
42560 @c man begin DESCRIPTION gdb
42561 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
42562 going on ``inside'' another program while it executes -- or what another
42563 program was doing at the moment it crashed.
42565 @value{GDBN} can do four main kinds of things (plus other things in support of
42566 these) to help you catch bugs in the act:
42570 Start your program, specifying anything that might affect its behavior.
42573 Make your program stop on specified conditions.
42576 Examine what has happened, when your program has stopped.
42579 Change things in your program, so you can experiment with correcting the
42580 effects of one bug and go on to learn about another.
42583 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
42586 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
42587 commands from the terminal until you tell it to exit with the @value{GDBN}
42588 command @code{quit}. You can get online help from @value{GDBN} itself
42589 by using the command @code{help}.
42591 You can run @code{gdb} with no arguments or options; but the most
42592 usual way to start @value{GDBN} is with one argument or two, specifying an
42593 executable program as the argument:
42599 You can also start with both an executable program and a core file specified:
42605 You can, instead, specify a process ID as a second argument, if you want
42606 to debug a running process:
42614 would attach @value{GDBN} to process @code{1234} (unless you also have a file
42615 named @file{1234}; @value{GDBN} does check for a core file first).
42616 With option @option{-p} you can omit the @var{program} filename.
42618 Here are some of the most frequently needed @value{GDBN} commands:
42620 @c pod2man highlights the right hand side of the @item lines.
42622 @item break [@var{file}:]@var{function}
42623 Set a breakpoint at @var{function} (in @var{file}).
42625 @item run [@var{arglist}]
42626 Start your program (with @var{arglist}, if specified).
42629 Backtrace: display the program stack.
42631 @item print @var{expr}
42632 Display the value of an expression.
42635 Continue running your program (after stopping, e.g. at a breakpoint).
42638 Execute next program line (after stopping); step @emph{over} any
42639 function calls in the line.
42641 @item edit [@var{file}:]@var{function}
42642 look at the program line where it is presently stopped.
42644 @item list [@var{file}:]@var{function}
42645 type the text of the program in the vicinity of where it is presently stopped.
42648 Execute next program line (after stopping); step @emph{into} any
42649 function calls in the line.
42651 @item help [@var{name}]
42652 Show information about @value{GDBN} command @var{name}, or general information
42653 about using @value{GDBN}.
42656 Exit from @value{GDBN}.
42660 For full details on @value{GDBN},
42661 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42662 by Richard M. Stallman and Roland H. Pesch. The same text is available online
42663 as the @code{gdb} entry in the @code{info} program.
42667 @c man begin OPTIONS gdb
42668 Any arguments other than options specify an executable
42669 file and core file (or process ID); that is, the first argument
42670 encountered with no
42671 associated option flag is equivalent to a @option{-se} option, and the second,
42672 if any, is equivalent to a @option{-c} option if it's the name of a file.
42674 both long and short forms; both are shown here. The long forms are also
42675 recognized if you truncate them, so long as enough of the option is
42676 present to be unambiguous. (If you prefer, you can flag option
42677 arguments with @option{+} rather than @option{-}, though we illustrate the
42678 more usual convention.)
42680 All the options and command line arguments you give are processed
42681 in sequential order. The order makes a difference when the @option{-x}
42687 List all options, with brief explanations.
42689 @item -symbols=@var{file}
42690 @itemx -s @var{file}
42691 Read symbol table from file @var{file}.
42694 Enable writing into executable and core files.
42696 @item -exec=@var{file}
42697 @itemx -e @var{file}
42698 Use file @var{file} as the executable file to execute when
42699 appropriate, and for examining pure data in conjunction with a core
42702 @item -se=@var{file}
42703 Read symbol table from file @var{file} and use it as the executable
42706 @item -core=@var{file}
42707 @itemx -c @var{file}
42708 Use file @var{file} as a core dump to examine.
42710 @item -command=@var{file}
42711 @itemx -x @var{file}
42712 Execute @value{GDBN} commands from file @var{file}.
42714 @item -ex @var{command}
42715 Execute given @value{GDBN} @var{command}.
42717 @item -directory=@var{directory}
42718 @itemx -d @var{directory}
42719 Add @var{directory} to the path to search for source files.
42722 Do not execute commands from @file{~/.gdbinit}.
42726 Do not execute commands from any @file{.gdbinit} initialization files.
42730 ``Quiet''. Do not print the introductory and copyright messages. These
42731 messages are also suppressed in batch mode.
42734 Run in batch mode. Exit with status @code{0} after processing all the command
42735 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
42736 Exit with nonzero status if an error occurs in executing the @value{GDBN}
42737 commands in the command files.
42739 Batch mode may be useful for running @value{GDBN} as a filter, for example to
42740 download and run a program on another computer; in order to make this
42741 more useful, the message
42744 Program exited normally.
42748 (which is ordinarily issued whenever a program running under @value{GDBN} control
42749 terminates) is not issued when running in batch mode.
42751 @item -cd=@var{directory}
42752 Run @value{GDBN} using @var{directory} as its working directory,
42753 instead of the current directory.
42757 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
42758 @value{GDBN} to output the full file name and line number in a standard,
42759 recognizable fashion each time a stack frame is displayed (which
42760 includes each time the program stops). This recognizable format looks
42761 like two @samp{\032} characters, followed by the file name, line number
42762 and character position separated by colons, and a newline. The
42763 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
42764 characters as a signal to display the source code for the frame.
42767 Set the line speed (baud rate or bits per second) of any serial
42768 interface used by @value{GDBN} for remote debugging.
42770 @item -tty=@var{device}
42771 Run using @var{device} for your program's standard input and output.
42775 @c man begin SEEALSO gdb
42777 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42778 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42779 documentation are properly installed at your site, the command
42786 should give you access to the complete manual.
42788 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42789 Richard M. Stallman and Roland H. Pesch, July 1991.
42793 @node gdbserver man
42794 @heading gdbserver man
42796 @c man title gdbserver Remote Server for the GNU Debugger
42798 @c man begin SYNOPSIS gdbserver
42799 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42801 gdbserver --attach @var{comm} @var{pid}
42803 gdbserver --multi @var{comm}
42807 @c man begin DESCRIPTION gdbserver
42808 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
42809 than the one which is running the program being debugged.
42812 @subheading Usage (server (target) side)
42815 Usage (server (target) side):
42818 First, you need to have a copy of the program you want to debug put onto
42819 the target system. The program can be stripped to save space if needed, as
42820 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
42821 the @value{GDBN} running on the host system.
42823 To use the server, you log on to the target system, and run the @command{gdbserver}
42824 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
42825 your program, and (c) its arguments. The general syntax is:
42828 target> gdbserver @var{comm} @var{program} [@var{args} ...]
42831 For example, using a serial port, you might say:
42835 @c @file would wrap it as F</dev/com1>.
42836 target> gdbserver /dev/com1 emacs foo.txt
42839 target> gdbserver @file{/dev/com1} emacs foo.txt
42843 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
42844 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
42845 waits patiently for the host @value{GDBN} to communicate with it.
42847 To use a TCP connection, you could say:
42850 target> gdbserver host:2345 emacs foo.txt
42853 This says pretty much the same thing as the last example, except that we are
42854 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
42855 that we are expecting to see a TCP connection from @code{host} to local TCP port
42856 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
42857 want for the port number as long as it does not conflict with any existing TCP
42858 ports on the target system. This same port number must be used in the host
42859 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
42860 you chose a port number that conflicts with another service, @command{gdbserver} will
42861 print an error message and exit.
42863 @command{gdbserver} can also attach to running programs.
42864 This is accomplished via the @option{--attach} argument. The syntax is:
42867 target> gdbserver --attach @var{comm} @var{pid}
42870 @var{pid} is the process ID of a currently running process. It isn't
42871 necessary to point @command{gdbserver} at a binary for the running process.
42873 To start @code{gdbserver} without supplying an initial command to run
42874 or process ID to attach, use the @option{--multi} command line option.
42875 In such case you should connect using @kbd{target extended-remote} to start
42876 the program you want to debug.
42879 target> gdbserver --multi @var{comm}
42883 @subheading Usage (host side)
42889 You need an unstripped copy of the target program on your host system, since
42890 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
42891 would, with the target program as the first argument. (You may need to use the
42892 @option{--baud} option if the serial line is running at anything except 9600 baud.)
42893 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
42894 new command you need to know about is @code{target remote}
42895 (or @code{target extended-remote}). Its argument is either
42896 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
42897 descriptor. For example:
42901 @c @file would wrap it as F</dev/ttyb>.
42902 (gdb) target remote /dev/ttyb
42905 (gdb) target remote @file{/dev/ttyb}
42910 communicates with the server via serial line @file{/dev/ttyb}, and:
42913 (gdb) target remote the-target:2345
42917 communicates via a TCP connection to port 2345 on host `the-target', where
42918 you previously started up @command{gdbserver} with the same port number. Note that for
42919 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
42920 command, otherwise you may get an error that looks something like
42921 `Connection refused'.
42923 @command{gdbserver} can also debug multiple inferiors at once,
42926 the @value{GDBN} manual in node @code{Inferiors and Programs}
42927 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
42930 @ref{Inferiors and Programs}.
42932 In such case use the @code{extended-remote} @value{GDBN} command variant:
42935 (gdb) target extended-remote the-target:2345
42938 The @command{gdbserver} option @option{--multi} may or may not be used in such
42942 @c man begin OPTIONS gdbserver
42943 There are three different modes for invoking @command{gdbserver}:
42948 Debug a specific program specified by its program name:
42951 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42954 The @var{comm} parameter specifies how should the server communicate
42955 with @value{GDBN}; it is either a device name (to use a serial line),
42956 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
42957 stdin/stdout of @code{gdbserver}. Specify the name of the program to
42958 debug in @var{prog}. Any remaining arguments will be passed to the
42959 program verbatim. When the program exits, @value{GDBN} will close the
42960 connection, and @code{gdbserver} will exit.
42963 Debug a specific program by specifying the process ID of a running
42967 gdbserver --attach @var{comm} @var{pid}
42970 The @var{comm} parameter is as described above. Supply the process ID
42971 of a running program in @var{pid}; @value{GDBN} will do everything
42972 else. Like with the previous mode, when the process @var{pid} exits,
42973 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
42976 Multi-process mode -- debug more than one program/process:
42979 gdbserver --multi @var{comm}
42982 In this mode, @value{GDBN} can instruct @command{gdbserver} which
42983 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
42984 close the connection when a process being debugged exits, so you can
42985 debug several processes in the same session.
42988 In each of the modes you may specify these options:
42993 List all options, with brief explanations.
42996 This option causes @command{gdbserver} to print its version number and exit.
42999 @command{gdbserver} will attach to a running program. The syntax is:
43002 target> gdbserver --attach @var{comm} @var{pid}
43005 @var{pid} is the process ID of a currently running process. It isn't
43006 necessary to point @command{gdbserver} at a binary for the running process.
43009 To start @code{gdbserver} without supplying an initial command to run
43010 or process ID to attach, use this command line option.
43011 Then you can connect using @kbd{target extended-remote} and start
43012 the program you want to debug. The syntax is:
43015 target> gdbserver --multi @var{comm}
43019 Instruct @code{gdbserver} to display extra status information about the debugging
43021 This option is intended for @code{gdbserver} development and for bug reports to
43024 @item --remote-debug
43025 Instruct @code{gdbserver} to display remote protocol debug output.
43026 This option is intended for @code{gdbserver} development and for bug reports to
43029 @item --debug-format=option1@r{[},option2,...@r{]}
43030 Instruct @code{gdbserver} to include extra information in each line
43031 of debugging output.
43032 @xref{Other Command-Line Arguments for gdbserver}.
43035 Specify a wrapper to launch programs
43036 for debugging. The option should be followed by the name of the
43037 wrapper, then any command-line arguments to pass to the wrapper, then
43038 @kbd{--} indicating the end of the wrapper arguments.
43041 By default, @command{gdbserver} keeps the listening TCP port open, so that
43042 additional connections are possible. However, if you start @code{gdbserver}
43043 with the @option{--once} option, it will stop listening for any further
43044 connection attempts after connecting to the first @value{GDBN} session.
43046 @c --disable-packet is not documented for users.
43048 @c --disable-randomization and --no-disable-randomization are superseded by
43049 @c QDisableRandomization.
43054 @c man begin SEEALSO gdbserver
43056 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43057 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43058 documentation are properly installed at your site, the command
43064 should give you access to the complete manual.
43066 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43067 Richard M. Stallman and Roland H. Pesch, July 1991.
43074 @c man title gcore Generate a core file of a running program
43077 @c man begin SYNOPSIS gcore
43078 gcore [-a] [-o @var{filename}] @var{pid}
43082 @c man begin DESCRIPTION gcore
43083 Generate a core dump of a running program with process ID @var{pid}.
43084 Produced file is equivalent to a kernel produced core file as if the process
43085 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
43086 limit). Unlike after a crash, after @command{gcore} the program remains
43087 running without any change.
43090 @c man begin OPTIONS gcore
43093 Dump all memory mappings. The actual effect of this option depends on
43094 the Operating System. On @sc{gnu}/Linux, it will disable
43095 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
43096 enable @code{dump-excluded-mappings} (@pxref{set
43097 dump-excluded-mappings}).
43099 @item -o @var{filename}
43100 The optional argument
43101 @var{filename} specifies the file name where to put the core dump.
43102 If not specified, the file name defaults to @file{core.@var{pid}},
43103 where @var{pid} is the running program process ID.
43107 @c man begin SEEALSO gcore
43109 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43110 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43111 documentation are properly installed at your site, the command
43118 should give you access to the complete manual.
43120 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43121 Richard M. Stallman and Roland H. Pesch, July 1991.
43128 @c man title gdbinit GDB initialization scripts
43131 @c man begin SYNOPSIS gdbinit
43132 @ifset SYSTEM_GDBINIT
43133 @value{SYSTEM_GDBINIT}
43142 @c man begin DESCRIPTION gdbinit
43143 These files contain @value{GDBN} commands to automatically execute during
43144 @value{GDBN} startup. The lines of contents are canned sequences of commands,
43147 the @value{GDBN} manual in node @code{Sequences}
43148 -- shell command @code{info -f gdb -n Sequences}.
43154 Please read more in
43156 the @value{GDBN} manual in node @code{Startup}
43157 -- shell command @code{info -f gdb -n Startup}.
43164 @ifset SYSTEM_GDBINIT
43165 @item @value{SYSTEM_GDBINIT}
43167 @ifclear SYSTEM_GDBINIT
43168 @item (not enabled with @code{--with-system-gdbinit} during compilation)
43170 System-wide initialization file. It is executed unless user specified
43171 @value{GDBN} option @code{-nx} or @code{-n}.
43174 the @value{GDBN} manual in node @code{System-wide configuration}
43175 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
43178 @ref{System-wide configuration}.
43182 User initialization file. It is executed unless user specified
43183 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
43186 Initialization file for current directory. It may need to be enabled with
43187 @value{GDBN} security command @code{set auto-load local-gdbinit}.
43190 the @value{GDBN} manual in node @code{Init File in the Current Directory}
43191 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
43194 @ref{Init File in the Current Directory}.
43199 @c man begin SEEALSO gdbinit
43201 gdb(1), @code{info -f gdb -n Startup}
43203 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43204 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43205 documentation are properly installed at your site, the command
43211 should give you access to the complete manual.
43213 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43214 Richard M. Stallman and Roland H. Pesch, July 1991.
43220 @node GNU Free Documentation License
43221 @appendix GNU Free Documentation License
43224 @node Concept Index
43225 @unnumbered Concept Index
43229 @node Command and Variable Index
43230 @unnumbered Command, Variable, and Function Index
43235 % I think something like @@colophon should be in texinfo. In the
43237 \long\def\colophon{\hbox to0pt{}\vfill
43238 \centerline{The body of this manual is set in}
43239 \centerline{\fontname\tenrm,}
43240 \centerline{with headings in {\bf\fontname\tenbf}}
43241 \centerline{and examples in {\tt\fontname\tentt}.}
43242 \centerline{{\it\fontname\tenit\/},}
43243 \centerline{{\bf\fontname\tenbf}, and}
43244 \centerline{{\sl\fontname\tensl\/}}
43245 \centerline{are used for emphasis.}\vfill}
43247 % Blame: doc@@cygnus.com, 1991.